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Background: The morphology and between-eye symmetry of the visual field loss associated with the antiepileptic drug vigabatrin (VAVFL) has received little attention., Objective: Our objective was to model the appearance and ensuing staging of VAVFL derived with the European Medicines Agency-approved perimetric protocol., Methods: This was a retrospective, cross-sectional, observational study that identified 123 adults who had received vigabatrin for refractory seizures and who had no evidence of co-existing retino-geniculo-cortical visual pathway abnormality. A further 38 adults with refractory seizures and identical inclusion criteria but no exposure to vigabatrin acted as controls. For each group, the median outcome at each stimulus location in each eye (of absolute loss, relative loss or Pattern Deviation probability level, as appropriate) was derived for each successive ten pairs of fields, ranked for severity. Between-eye symmetry was quantified by an index that accounted for severity of loss and that was referenced to the likelihood of the occurrence of symmetry due to chance., Results: The modelled VAVFL was bilateral and highly symmetrical and was described by six stages that were all independent of the extent of vigabatrin exposure. The loss originated in the extreme temporal periphery and encroached centripetally along all meridians towards fixation. The initial appearance within the central field (Stage 2) occurred inferior-nasally. Subsequent stages exhibited increasing loss, which was greater nasally than temporally. Stage 6 described concentric loss extending to approximately 15° eccentricity from fixation., Conclusion: The model exhibited a consistent pattern of VAVFL. The staging of the loss could assist the risk:benefit analysis of vigabatrin for the treatment of epilepsy.

Background: The antiepileptic drug vigabatrin is associated with characteristic visual field loss (VAVFL) and thinning of the peripapillary retinal nerve fibre layer (PPRNFL); however, the relationship is equivocal., Objective: The aim of this study was to determine the function-structure relationship associated with long-term exposure to vigabatrin, thereby improving the risk/benefit analysis of the drug., Methods: A cross-sectional observational design identified 40 adults who had received long-term vigabatrin for refractory seizures, who had no evidence of co-existing retino-geniculo-cortical visual pathway abnormality, and who had undergone a standardized protocol of perimetry and of optical coherence tomography (OCT) of the PPRNFL. Vigabatrin toxicity was defined as the presence of VAVFL. The function-structure relationship for the superior and inferior retinal quadrants was evaluated by two established models applicable to other optic neuropathies., Results: The function-structure relationship for each model was consistent with an optic neuropathy. PPRNFL thinning, expressed in micrometres, asymptoted at an equivalent visual field loss of worse than approximately - 10.0 dB, thereby preventing assessment of more substantial thinning. Transformation of the outcomes to retinal ganglion cell soma and axon estimates, respectively, resulted in a linear relationship., Conclusions: Functional and structural abnormality is strongly related in individuals with vigabatrin toxicity and no evidence of visual pathway comorbidity, thereby implicating retinal ganglion cell dysfunction. OCT affords a limited measurement range compared with perimetry: severity cannot be directly assessed when the PPRNFL quadrant thickness is less than approximately 65 µm, depending on the tomographer. This limitation can be overcome by transformation of thickness to remaining axons, an outcome requiring input from perimetry.

Microperimetry is a novel technique for assessing visual function that appears particularly suitable for age-related macular degeneration (AMD). Compared with standard automated perimetry, microperimetry offers several unique features. It simultaneously images the fundus, incorporates an eye-tracking system to correct the stimulus location for fixation loss, and identifies any preferred retinal loci. We identified 52 articles that met the inclusion criteria for a systematic review of microperimetry in the assessment of visual function in AMD. We discuss microperimetry and AMD in relation to disease severity, structural imaging outcomes, other measures of visual function, and evaluation of the efficacy of surgical and/or medical therapies in clinical trials. The evidence for the use of microperimetry in the functional assessment of AMD is encouraging. Disruptions of the ellipsoid zone band and retinal pigment epithelium are clearly associated with reduced differential light sensitivity despite the maintenance of good visual acuity. Reduced differential light sensitivity is also associated with outer segment thinning and retinal pigment epithelium thickening in early AMD and with both a thickening and a thinning of the whole retina in choroidal neovascularization. Microperimetry, however, lacks the robust diffuse and focal loss age-corrected probability analyses associated with standard automated perimetry, and the technique is currently limited by this omission., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: The antiepileptic drug vigabatrin has been used widely since 1989, but has only been approved for use in the US since 2009. The risk:benefit of vigabatrin is generally predicated upon an assumed frequency of associated visual field loss (VAVFL) of approximately 31 %. This estimate is based upon relatively short-term usage (up to 4-5 years) and it is essential to determine whether the frequency of VAVFL increases with longer-term usage., Objective: The aim of this study was to model, from cross-sectional evidence, over greater ranges of treatment duration and cumulative dose than previously evaluated, the risk (frequency) of VAVFL with increasing exposure to vigabatrin., Study Design and Setting: This was a retrospective cohort study undertaken in a regional hospital epilepsy clinic., Patients: The cohort comprised 147 consecutive patients treated with vigabatrin for refractory complex partial (focal) seizures, who had all undergone ophthalmological examination and who had undertaken perimetry, reliably, according to a standard and robust protocol. The visual field plots were evaluated masked to treatment duration and dose., Main Outcome Measure: The risk (frequency) of VAVFL with increasing exposure to vigabatrin was modelled, from the cross-sectional evidence, by standard and plateau logistic regression., Results: The cohort comprised 80 females and 67 males (mean age 40.3 years, standard deviation 13.7). The median duration of vigabatrin exposure was 7.9 years (interquartile range 3.6-11.0, range 0.2-16.1 years); 46 patients (31 %) had received vigabatrin for over 10 years. Eighty-seven patients (59 %) exhibited VAVFL; the proportion with VAVFL was higher in males (66 %) than females (54 %). The plateau model for duration and for cumulative dose exhibited a better fit than the standard model (both p < 0.001). The modelled frequency of VAVFL increased with increasing exposure up to approximately 6 years duration and 5 kg cumulative dose, and plateaued at approximately 76 % (95 % CI 67-85) and 79 % (95 % CI 70-87), respectively. Severity of VAVFL, classified in terms of the visual field index Mean Deviation, was not significantly associated with either duration or cumulative dose of therapy., Conclusion: Clinicians and patients, in enabling informed choice, should be alert to the possible substantial increased risk:benefit for VAVFL with increasing long-term exposure to vigabatrin and the ensuing increased cost:benefit resulting from the necessary additional visual assessments.

Purpose: Vigabatrin is an efficacious antiepileptic drug licensed as add-on therapy in refractory epilepsy and used in infantile spasms. Eight years after licensing, there emerged a strong and possibly causative association with bilateral visual field loss. We report a systematic review ascertaining the magnitude of risk of vigabatrin associated visual field loss (VAVFL) and any clinical predictors of risk., Methods: Electronic searches, including MEDLINE (1966-2009), EMBASE (1974-2009), and CINAHL (1982-2009), were conducted. Reports, published in full, of observational studies investigating the prevalence of visual field loss in patients with partial epilepsy treated with vigabatrin were included. Outcomes were the proportion with visual field loss, and the relative risk of VAVFL compared to similar nonexposed patients with epilepsy., Key Findings: Thirty-two studies were identified, which included 1,678 patients exposed to vigabatrin and 406 controls. Of the 1,678 exposed patients, 738 (44%) had visual field loss compared to just 30 (7%) among the 406 controls. The random-effects estimate for the proportion of adults with visual field loss was 52% [95% confidence interval (CI) 46-59]. The estimate for children was lower at 34% (95% CI 25-42). The relative risk for field loss in vigabatrin-exposed patients was 4.0 (95% CI 2.9-5.5). Larger mean cumulative dose of vigabatrin and increasing age were associated with a higher proportion of patients with visual field loss., Significance: Vigabatrin should be reserved for patients with epilepsy for whom there is no other alternative or for patients who have determined the benefit of ongoing treatment to outweigh the risk of VAVFL., (Wiley Periodicals, Inc. © 2010 International League Against Epilepsy.)

Background: Use of the antiepileptic drug vigabatrin is associated with an elevated risk of visual field loss., Objective: To determine the frequency of, and risk factors for, vigabatrin-attributed visual field loss (VAVFL) in the setting of a large-scale, multinational, prospective, observational study., Study Design: A comparative, open-label, parallel-group, multicentre study., Setting: Hospital outpatient clinics at 46 centres in five countries., Patients: 734 patients with refractory partial epilepsy, divided into three groups and stratified by age (8-12 years; >12 years) and exposure to vigabatrin. Group I comprised patients treated with vigabatrin for > or =6 months. Group II comprised patients previously treated with vigabatrin for > or =6 months who had withdrawn from the drug for > or =6 months. Group III comprised patients never treated with vigabatrin. Patients underwent perimetry at either 4- or 6-month intervals, for up to 36 months. Visual field outcome was evaluated masked to drug exposure., Intervention: Perimetry., Main Outcome Measure: The visual field outcome at each of four analysis points: (i) at enrolment (i.e. baseline, all patients); (ii) for patients exhibiting a conclusive outcome at the initial visual field examination; (iii) for patients exhibiting at least one conclusive outcome to the visual field examinations; and (iv) at the last conclusive outcome to the visual field examinations., Results: Of the 734 patients, 524 yielded one or more conclusive visual field examinations. For Group I, the frequency of VAVFL at the last conclusive examination was 10/38 (26.3%) for those aged 8-12 years and 65/150 (43.3%) for those aged >12 years. For Group II, the respective frequencies were 7/47 (14.9%) and 37/151 (24.5%). One case resembling VAVFL was present amongst the 186 patients in Group III at the last conclusive examination. The frequency of VAVFL in Groups I and II combined was 20.0% for those aged 8-12 years and 33.9% for those aged >12 years. VAVFL was associated with duration of vigabatrin therapy (odds ratio [OR] up to 15.2; 95% CI 4.4, 51.7), mean daily dose of vigabatrin (OR up to 26.4; 95% CI 2.4, 291.7) and male gender (OR 2.51; 95% CI 1.5, 4.1). VAVFL was more frequently detected with static than with kinetic perimetry (OR up to 0.43; 95% CI 0.24, 0.75)., Conclusions: Since the probability of VAVFL is positively associated with treatment duration, careful assessment of the risk-benefit ratio of continuing treatment with vigabatrin is recommended in patients currently receiving this drug. All patients continuing to receive vigabatrin should undergo visual field examination at least every 6 months for the duration of treatment. We recommend two-level (three-zone), gradient-adapted, suprathreshold static perimetry of the peripheral field together with threshold perimetry of the central field out to 30 degrees from fixation. The frequency of ophthalmological and perimetric examinations should be increased in the presence of VAVFL.

Purpose: To investigate whether nasal peripapillary retinal nerve fiber layer (RNFL) attenuation is associated with visual field loss attributed to the anti-epileptic drug vigabatrin., Design: Prospective cross-sectional observational study., Participants: Twenty-seven individuals with focal-onset epilepsy exposed to vigabatrin and 13 individuals with focal-onset epilepsy exposed to non-GABAergic anti-epileptic drug monotherapy., Methods: At one visit, suprathreshold perimetry of the central and peripheral field (3-zone, age-corrected Full Field 135 Screening Test) and threshold perimetry of the central field (Program 30-2 and the FASTPAC strategy) were undertaken using the Humphrey Field Analyzer (Carl Zeiss Meditech, Dublin, CA). At a second visit, ocular coherence tomography was undertaken for the right eye using the 3.4 RNFL thickness protocol of the StratusOCT (Carl Zeiss Meditech)., Main Outcome Measures: The magnitude, for each individual, of the RNFL thickness, averaged across the 4 oblique quadrants, and for each separate quadrant., Results: Of the 27 individuals exposed to vigabatrin, 11 (group I) exhibited vigabatrin-attributed visual field loss, 15 exhibited a normal field, and 1 exhibited a homonymous quadrantanopia (group II). All 13 individuals exposed to non-GABAergic therapy had normal fields (group III). All individuals in group I exhibited abnormal average and nasal quadrant RNFL thicknesses in the presence of a normal temporal quadrant thickness. Most also exhibited additional RNFL attenuation in either the superior or inferior quadrant, or both. Four individuals in group II exhibited an identical pattern of RNFL attenuation suggesting that nasal RNFL thinning is a more sensitive marker for vigabatrin toxicity than visual field loss. None of the 13 individuals in group III exhibited nasal quadrant RNFL attenuation., Conclusions: Vigabatrin-attributed visual field loss is associated with a characteristic pattern of RNFL attenuation: nasal quadrant thinning and normal temporal quadrant thickness with, or without, superior or inferior quadrant involvement. Nasal attenuation may precede visual field loss. Ocular coherence tomography of the peripapillary RNFL should be considered in patients previously exposed to vigabatrin. It should also be considered at baseline and follow-up in those commencing vigabatrin for treatment of epilepsy or in trials for anti-addiction therapy. The pattern of RNFL thinning seems to be a useful biomarker to identify vigabatrin toxicity.

The purpose of the study was to determine whether in utero exposure to vigabatrin caused visual field loss. Three mothers with four children who had been exposed to vigabatrin in utero and who were subsequently formula fed were identified. All seven individuals underwent perimetry and imaging of the retinal nerve fiber layer (RNFL). All individuals yielded reliable outcomes to perimetry and RNFL images of acceptable quality. Two of the three mothers exhibited vigabatrin-attributed visual field loss and an abnormally attenuated RNFL. The third exhibited an upper left quadrantanopia, consistent with previous temporal lobe surgery, and a normal RNFL. All four children yielded normal visual fields and RNFL thicknesses. The presence of the normal findings for the children is reassuring and, if representative, suggests a lack of vigabatrin visual toxicity and therefore obviates the need for ophthalmological examination of those exposed to vigabatrin prenatally.

Purpose: To determine the increase in isopter extent, resulting from the measurement of, and correction for, individual reaction time (RT; the latency between stimulus presentation and individual patient response), derived under the standardized conditions of semi-automated kinetic perimetry (SKP), and to model the age- and RT-corrected normative isopter values for SKP applicable to any Goldmann stimulus combination., Design: Cross-sectional observational study., Participants: Eighty-three healthy participants aged 10 to 80 years (11-12 participants per decade of age)., Methods: One eye of each participant underwent SKP using the Octopus 101 perimeter (Haag-Streit, Koeniz, Switzerland). Four Goldmann stimulus combinations, III4e at 25 degrees/second, III4e at 5 degrees/second, I3e at 5 degrees/second, and I2e at 2 degrees/second, were presented centripetally (i.e., in a direction toward the center of the bowl) along the 8 cardinal meridia in random order. The local kinetic threshold (LKT) for each stimulus combination along each meridian was corrected for the angular distance traveled during the individual geometric mean RT and was modeled in terms of the covariables stimulus size, stimulus luminance, meridian, and age, and then presented in terms of a graphical reference plot., Main Outcome Measures: The variation of the LKT with RT, stimulus combination, meridian, and age., Results: The median of the individual geometric mean RTs initially decreased and then increased with increase in age and was greater for stimulus combinations producing small isopters compared with those generating large isopters. Reaction time-corrected LKTs were fitted optimally by a multiple regression model (R2 = 0.86). For large (> or =size III) and intense (4e) stimuli, RT-corrected LKTs were independent of age and mainly were influenced by instrument- and facial anatomy-related characteristics. Reaction time-corrected LKTs, particularly for small (< or = size II) stimuli, exhibited a clear age dependence above the age of 40 years particularly for reduced luminance stimuli (< or = 2e), with an approximate reduction in angular extent of 2 degrees per decade for the I1e stimulus., Conclusions: The development of a graphical reference plot with mean isopters and accompanying reference intervals for age- and RT-corrected SKP, applicable to any individual patient, should facilitate the evaluation of clinical data and the implementation of a computerized alternative to manual Goldmann kinetic perimetry.

Purpose: To quantify retinal nerve fiber layer thickness (RNFLT) and macular thickness (MT) in patients exhibiting vigabatrin-attributed visual field loss (VAVFL) and to determine the efficacy of these measures as markers of the retinal damage associated with vigabatrin., Methods: This was a prospective cross-sectional observational study involving five groups: Group I, 13 patients exhibiting VAVFL; Group II, 8 patients exposed to vigabatrin but with normal fields; Group III, 14 patients receiving carbamazepine monotherapy; Group IV, 20 normal individuals; and Group V, 7 patients receiving sodium valproate monotherapy. At one of two visits, the right eye of each participant underwent two digital imaging modalities: ocular coherence tomography (OCT; StratusOCT; Carl Zeiss Meditec, Dublin, CA) and scanning laser ophthalmoscopy (SLO; Heidelberg Retinal Tomograph; Heidelberg Engineering GmbH, Heidelberg, Germany). At the other visit, participants underwent three-zone, age-corrected suprathreshold perimetry of the whole field and threshold perimetry of the central field (Humphrey Field Analyzer 750; Carl Zeiss Meditec). The order of the visits was randomized., Results: The group mean RNFLT in Group I was attenuated relative to that of the remaining groups (all P < 0.001). At 100% specificity, based on the 95% confidence limits derived from Group IV, OCT exhibited 100% sensitivity and SLO 77% sensitivity for an attenuated RNFLT in patients with VAVFL. All participants manifested an MT within the normal range derived from Group IV., Conclusions: OCT of the RNFL can efficiently identify vigabatrin-induced damage and will be useful for adults and children unable to perform perimetry and when the perimetric outcome is equivocal.

Purpose: To document the magnitude of any learning effect for short-wavelength automated perimetry (SWAP) in patients with either ocular hypertension (OHT) or open-angle glaucoma (OAG) who are experienced in standard automated perimetry (SAP)., Design: Experimental study., Participants: Thirty-five patients (22 with OHT and 13 with OAG) who had previously undergone at least 3 threshold SAP visual field examinations with the Humphrey Field Analyzer (HFA; Carl Zeiss Meditech Inc., Dublin, CA), and 9 patients with OHT who had not previously undertaken any form of perimetry., Methods: Each patient attended for SWAP on 5 occasions, each separated by 1 week. At each visit, both eyes were examined using Program 24-2 of the HFA; the right eye was always examined before the left eye., Main Outcome Measures: (1) Change over the 5 examinations, in each eye, of the visual field indices Mean Deviation (MD), Short-term Fluctuation (SF), Pattern Standard Deviation (PSD), and Corrected Pattern Standard Deviation. (2) Change in each eye between Visits 1 and 5 in proportionate Mean Sensitivity (pMS) for the central annulus of stimulus locations compared with that for the peripheral annulus thereby determining the influence of stimulus eccentricity on any alteration in sensitivity. (3) Change between Visits 1 and 5 in the number and magnitude of the Pattern Deviation (PD) probability levels associated with any alteration in sensitivity., Results: The MD, SF, and PSD each improved over the 5 examinations (each at P<0.001). The improvement in pMS between Visits 1 and 5 was greater for the peripheral annulus than for the central annulus by approximately twofold for the patients with OAG. Considerable variation was present between patients, within and between groups, in the number of locations exhibiting an improving sensitivity between Visits 1 and 5 by 1 or more PD probability levels., Conclusions: Care should be taken to ensure that, during the initial examinations, apparent field loss with SWAP in patients exhibiting a normal field by SAP is not the result of inexperience in SWAP. Apparently deeper or wider field loss in the initial examinations with SWAP compared with that exhibited by SAP in OAG also may arise from inexperience in SWAP.

Purpose: To determine the influence of the spatial extent and the depth of localized field loss on the computation of the General Height (GH) method for estimating the diffuse component of visual field loss and, therefore, on the subsequent appearance of the Pattern Deviation (PD) map., Methods: Varying shapes and depths of localized glaucomatous field loss were modeled in each of 82 Humphrey Field Analyzer Program 30-2 fields (82 normal eyes) by superimposing, on the fields from the normal eyes, the PD defect depth (P < 0.05) of one visual field from each of 123 patients with glaucoma. The difference in GH between each of the 10,086 modeled fields and the GH in the corresponding measured normal field was derived and the relationship to possible differences in the location-by-location significance levels of each pair of PD maps determined., Results: For the group mean overestimation in the GH of -0.79 dB, the 50th, 90th, and 95th percentiles of the modeled fields described 23.4%, 37.9%, and 42.6% locations, respectively, exhibiting an underestimation in PD statistical significance. As the size of the superimposed field loss increased, the overestimation of the GH increased, and the underestimation of PD statistical significance became more apparent. This error was independent of defect depth., Conclusions: The localized component of field loss in glaucoma produced an overestimation of diffuse loss and a consequent underestimation of the severity of focal loss by PD analysis. This effect increased as the spatial extent of the loss became more extensive and will lead to an underestimation of progressive localized field loss., (Copyright Association for Research in Vision and Ophthalmology)

Objective: To derive a visual-evoked potential (VEP) technique for identifying visual field defects in children with epilepsy treated with vigabatrin and unable to perform perimetry., Background: Studies have linked vigabatrin to a specific pattern of visual field loss. Few studies have included the pediatric population because of difficulties in assessing the visual field by perimetry below a developmental age of 9 years., Methods: A field-specific VEP was developed with a central (0 degrees to 5 degrees radius) and peripheral stimulus (30 degrees to 60 degrees radius). Stimuli consisted of black and white checks that increased in size with eccentricity. Checks reversed at different rates, allowing separate central and peripheral responses to be recorded. Five vigabatrin-treated young adults with field defects were identified using this stimulus. Electroretinograms (ERG) were recorded to examine the effects of vigabatrin on retinal function. Thirty-nine children aged 3 to 15 years were included in the study. Twelve patients were examined by both the field-specific stimulus test and perimetry. The diagnostic performance of the field-specific stimulus test was compared with that of perimetry., Results: Thirty-five of 39 children complied with the field-specific stimulus, 26 of 39 complied with the ERG, and 12 of 39 complied with perimetry. Using the summed amplitude of the peripheral response from O(2) and O(1), responses below 10 microV were deemed abnormal. The field-specific stimulus identified 3 of 4 abnormal perimetry results and 7 of 8 normal perimetry results, giving a sensitivity of 75% and a specificity of 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 microV, gave a useful indication of visual field loss., Conclusion: Field-specific VEP are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.

Short Wavelength Automated Perimetry (SWAP) utilizes a blue stimulus to preferentially stimulate the blue cones and a high luminance yellow background to adapt the green and red cones and to saturate, simultaneously, the activity of the rods. This review describes the theoretical aspects of SWAP, highlights current limitations associated with the technique and discusses potential clinical applications. Compared to white-on-white (W-W) perimetry, SWAP is limited clinically by: greater variability associated with the estimation of threshold, ocular media absorption, increased examination duration and an additional learning effect. Comparative studies of SWAP and W-W perimetry have generally been undertaken on small cohorts of patients. The conclusions are frequently unconvincing due to limitations for SWAP in the delineation of abnormality and of progressive field loss. SWAP is almost certainly able to identify glaucomatous visual field loss in advance of that by W-W perimetry although the incidence of progressive field loss is similar between the two techniques. Increasing evidence suggests that functional abnormality with SWAP is preceded by structural abnormality of the optic nerve head and/or the retinal nerve fibre layer. SWAP appears to be beneficial in the detection of diabetic macular oedema and possibly in some neuro-ophthalmic disorders.

Purpose: To determine the magnitude of the homogeneous, LF(Ho), and the heterogeneous, LF(He), components of the long-term fluctuation (LF) in glaucoma suspects and in stable primary open angle glaucoma (POAG) patients undergoing short-wavelength automated perimetry (SWAP) and to compare the magnitude of the SWAP LF components with those elicited by standard white-on-white (W-W) perimetry., Methods: The sample comprised 33 glaucoma suspects and 17 patients with early-to-moderate stable POAG who underwent W-W perimetry and SWAP at each of six visits over a mean period of 12.75 months (SD, 2.29). The LF(Ho), LF(He), and error components of the long-term fluctuation were determined between the third and seventh visual field examinations. The intervening visual field examinations and the optic nerve head parameters, derived both by stereo observation and by the Heidelberg Retinal Tomograph, were used to confirm stability over the follow-up period., Results: The LF(Ho) and LF(He) components were larger in the POAG patients than in the glaucoma suspects for both W-W perimetry and SWAP; the magnitude was independent of the depth of defect and of the short-term fluctuation. All three components of long-term fluctuation were greater for SWAP than for W-W perimetry, both in the glaucoma suspects and in the POAG patients., Conclusions: SWAP exhibits greater long-term fluctuation than white-on-white perimetry. The usefulness of SWAP will be limited if the extent of this variability is not overcome in future statistical procedures developed to detect progressive visual field loss.

Purpose: Symptomatic visual field constriction thought to be associated with vigabatrin has been reported. The current study investigated the visual fields and visual electrophysiology of eight patients with known vigabatrin-attributed visual field loss, three of whom were reported previously. Six of the patients were no longer receiving vigabatrin., Methods: The central and peripheral fields were examined with the Humphrey Visual Field Analyzer. Full visual electrophysiology, including flash electroretinography (ERG), pattern electroretinography, multifocal ERG using the VERIS system, electro-oculography, and flash and pattern visual evoked potentials, was undertaken., Results: Seven patients showed marked visual field constriction with some sparing of the temporal visual field. The eighth exhibited concentric constriction. Most electrophysiological responses were usually just within normal limits; two patients had subnormal Arden electro-oculography indices; and one patient showed an abnormally delayed photopic b wave. However, five patients showed delayed 30-Hz flicker b waves, and seven patients showed delayed oscillatory potentials. Multifocal ERG showed abnormalities that sometimes correlated with the visual field appearance and confirmed that the deficit occurs at the retinal level., Conclusion: Marked visual field constriction appears to be associated with vigabatrin therapy. The field defects and some electrophysiological abnormalities persist when vigabatrin therapy is withdrawn.

Purpose: To determine, in stable glaucoma, the characteristics of the between-examination variability of the visual field recorded with the Humphrey Field Analyser (HFA; Humphrey Systems, Dublin, CA) using the homogeneous, LF(Ho), and heterogeneous, LF(He), components of the long-term fluctuation (LF), thereby providing a technique for separating progressive loss from fluctuation in sensitivity., Methods: The LF components were calculated using a two-factor analysis of variance (ANOVA) with replications and were determined between each pair of three successive HFA program 30-2 fields for each patient from two groups, each containing 30 patients with primary open-angle glaucoma. The interval between examinations for the first group was 6 to 9 months and for the second group was 3 weeks., Results: The group mean values for LF(Ho) ranged from 1.50 to 2.19 dB and for LF(He) from 1.70 to 2.05 dB. The average difference between examinations was within +/-0.35 dB for each component, and the 95% limits of agreement for the two groups, respectively, were +/- 2.31 and +/- 2.39 dB for the LF(Ho) and +/- 2.36 and +/- 2.09 dB for the LF(He). The estimate of the 90% confidence limit for the LF(Ho) was 3.30 dB and for the LF(He), 3.60 dB. Little relationship was present between the LF components and the modulus differences in mean deviation (MD), the corrected pattern SD (CPSD), or the mean MD, mean short-term fluctuation, and mean CPSD, of the two fields., Conclusions: Estimation of the LF components and of the corresponding confidence limits yields an expression of the normal between-examination variability of two consecutive fields that can be used as a reliability index. A value outside the confidence limits indicates the necessity for a confirmatory follow-up field.

Purpose: Vigabatrin (VGB) therapy is associated with a loss of peripheral vision. The characteristics and prevalence of VGB-attributed visual field loss (V-AVFL) and associated risk factors were evaluated in patients with epilepsy., Methods: The material comprised the visual fields and case notes of 88 patients with suspected V-AVFL (25 spontaneous reports and 63 cases from an open-label extension trial) and of 42 patients receiving alternative antiepileptic drugs (AEDs) from a cross-sectional study., Results: Forty-two reliable cases of visual field loss could not be assigned to an alternative known cause and were therefore attributed to VGB (13 spontaneous reports and 29 from the open-label study). All cases except one were asymptomatic. Seven cases of field loss were present in the reference cohort of 42 patients; all cases could be attributed to a known aetiology. Thirty-six of the 42 confirmed cases of V-AVFL exhibited a bilateral defect that was most profound nasally, and three, a concentric constriction. The prevalence of V-AVFL was 29% (95% confidence interval, 21-39%). Male gender was associated with a 2.1-fold increased relative risk of V-AVFL (95% confidence interval, 1.20-4.6%). Age, body weight, duration of epilepsy, and daily dose of VGB, and concomitant AEDs did not predict the occurrence of V-AVFL., Conclusions: The unique visual field defect attributed to VGB is profound in terms of the frequency of occurrence and the location and severity of loss. The asymptomatic nature of the field loss indicates that V-AVFL can be elicited only by visual field examination.

Objective: To estimate the prevalence of visual field defects in patients taking the anticonvulsant drug vigabatrin and to characterise the features of visual dysfunction found., Methods: Thirty three unselected patients attending neurology and epilepsy clinics were identified as taking vigabatrin and asked to attend for neuro-ophthalmic evaluation. A control group of 16 patients with epilepsy unexposed to vigabatrin was also evaluated. Visual fields were examined by static perimetry using a Humphrey field analyser. Patients underwent detailed ophthalmic examination, various blood tests, and brain MRI where necessary. Visual evoked responses (VERs), electro-oculograms (EOGs), and electroretinograms (ERGs) were recorded., Results: Of 31 assessable patients treated with vigabatrin, 16 (52%) had definitely abnormal visual fields, nine (29%) had fields that were inconclusive, four (13%) had normal fields, and two (6%) proved unable to cooperate with testing. In four patients some plausible cause was found for the field abnormality leaving 12 patients (39%) in whom a definite bilateral field defect was found, possibly caused by vigabatrin treatment. Of 16 control patients none had definitely abnormal fields, 12 (75%) had normal fields, and four (25%) had fields that were inconclusive. The field defects associated with vigabatrin treatment showed a characteristic pattern of concentric peripheral field loss with temporal and macular sparing. The VERs and ERGs were normal. The EOG Arden Index was reduced in patients taking vigabatrin, although this returned towards normal when vigabatrin was stopped, even in the presence of persistent field defects. Multifocal ERGs recorded in two patients were abnormal, showing marked reduction in amplitude of the peripheral focal ERG., Conclusions: Treatment with vigabatrin was associated with a high prevalence of peripheral visual field defects. This seemed to be the result of a toxic effect of vigabatrin on the retina and seemed to persist if the drug was withdrawn.

Purpose: To determine the within-visit between-algorithm and the within-algorithm between-visit differences in sensitivity for the SITA Standard, SITA Fast, FASTPAC, and Full Threshold algorithms in stable primary open angle glaucoma., Methods: One designated eye from each of 29 patients (age 67.3 +/- 10.2 years; mean +/- SD) experienced in automated perimetry was examined with the four algorithms on each of three visits, using the Humphrey Field Analyzer 750 and Program 30-2., Results: The group mean Mean Sensitivity was 1.0 dB greater for SITA Standard than Full Threshold (P < 0.001), 0.7 dB greater for SITA Standard than FASTPAC (P < 0.001), 1.6 dB greater for SITA Fast than FASTPAC (P < 0.001), and 0.9 dB greater for SITA Fast than SITA Standard (P < 0.001). The higher pointwise sensitivity for SITA Fast compared to Full Threshold, FASTPAC, and SITA Standard increased with increase in defect depth. The examination duration for SITA Standard was 53% of that for Full Threshold and 50% shorter for SITA Fast compared to FASTPAC (P < 0.001), regardless of age (P = 0.932). The examination duration increased with increase in severity of field loss (P < 0.001), and this increase was proportionately greater for both SITA algorithms (P < 0.001), particularly SITA Fast. The Total and Pattern Deviation probability analyses of both SITA algorithms yielded a statistically greater defect than Full Threshold or FASTPAC (P < 0.001). The within-algorithm between-visit differences were similar between SITA Standard and Full Threshold and between SITA Fast and FASTPAC., Conclusions: Both SITA algorithms produce a marginally higher differential light sensitivity compared to existing algorithms but with a statistically deeper defect and a marked reduction in examination duration.

Purpose: To determine the intraindividual and interindividual characteristics of normal sensitivity derived by short-wavelength automated perimetry (SWAP) as a function of threshold algorithm. To determine also the influence of ocular media absorption on the magnitude of the interindividual variation in normal sensitivity, and hence the confidence limits, derived by SWAP., Methods: The sample comprised 51 normal subjects, stratified for age by decade (mean age, 55.5 years; range, 24-83 years) and experienced in white-on-white (W-W) perimetry and SWAP. One randomly assigned eye of each subject was examined on three occasions with Program 30-2 of the 640 Humphrey Field Analyzer using the Full Threshold and FASTPAC strategies for SWAP and W-W perimetries. Ocular media absorption (OMA) was assessed by the difference in scotopic sensitivity to stimuli of 410 and 560 nm., Results: The group mean examination time (P < 0.001) was greater for SWAP than for W-W perimetry for both the Full Threshold (15.0% longer) and FASTPAC strategies (16.8% longer). The gradient of the age-decline in Mean Sensitivity for SWAP was approximately 25% less steep when corrected for OMA than when uncorrected. The interindividual normal variability, expressed as the coefficient of variation, for SWAP without correction for OMA was 2.7 times greater (range 2.0-3.9), and with correction 1.9 times greater (range 1.4-2.9), than that for W-W perimetry., Conclusions: The increased interindividual normal variability of SWAP, exacerbated by the lack of correction for OMA, currently limits the utility of SWAP in that the reduction in sensitivity required to indicate abnormality was proportionately greater than for W-W perimetry.

Purpose: The authors compared pointwise univariate linear regression (ULR) of sensitivity against follow-up as an indicator of visual field progression with that of the corresponding ULR of mean deviation (MD) and with the Glaucoma Change Probability (GCP) analysis. The authors determined the influence of the number and sequence of prior examinations on the slope of the pointwise function., Methods: Univariate linear regression was undertaken at each stimulus location on the arbitrarily assigned left eyes of 38 patients with glaucoma examined with the Humphrey Field Analyzer Programs 30-2 or 24-2 (stimulus size III, Humphrey Instruments Inc, San Leandro, CA). The mean age was 59.0 years (standard deviation [SD] = 12.9), the mean number of fields per patients was 12.0 (SD = 2.8), and the mean duration of follow-up was 6.0 years (SD = 1.6)., Results: Four patients showed statistically significant MD slopes. Of the 34 patients exhibiting a nonsignificant MD slope, 15 exhibited clusters of at least two contiguous progressing locations. Less than half of these locations were designated as progressing by GCP. The GCP detected less than one third of the locations considered progressing by ULR for the last six fields in the series: this was attributed to the nonlinear nature of the decline in sensitivity., Conclusions: The degree of agreement between the outcomes of ULR and GCP was dependent on the quality of the collected data, the magnitude of the baseline sensitivity, the extent and type of the subsequent visual field progression, and the position of the fields within the examination series. Good agreement was illustrated at those locations where the deterioration fell outside the limits of expected variability in stable glaucoma.

Background: the extent of any learning and fatigue effects in blue-on-yellow (B-Y) perimetry is unknown. The within- and between-eye changes in B-Y normal sensitivity at a single visit and between visits was investigated as a function of previous experience in white-on-white (W-W) perimetry and of subject age., Methods: Sixty-one normal subjects 22 young (range 20-34 years) and 39 elderly (range 51-80 years)-- assigned to one of four groups based upon perimetric experience and age underwent B-Y perimetry on four separate occasions using Program 30-2 of a modified Humphrey Field Analyser 640. Perimetry was performed for both eyes on three consecutive days and again one week later. Global, hemifield and annular mean sensitivities and global short-term fluctuation were calculated for each eye at each visit., Results: Mean sensitivity was higher in the first eye examined and increased over the 3 days. The increase in mean sensitivity was similar for each eye and was independent of perimetric experience and age. Short-term fluctuation decreased over the 3 days, regardless of eye and experience, but was more pronounced for the younger age group. The extent of all improvements varied considerably between subjects., Conclusions: Improvements in B-Y perimetric performance occurred as the familiarity with the test increased, regardless of previous W-W experience. Failure to account for such improvement could reduce the efficiency of B-Y perimetry.

Purpose: To evaluate short-wavelength-sensitive perimetry in the detection of glaucomatous field loss., Methods: The sample consisted of 27 normal subjects, 24 patients with primary open angle glaucoma (POAG), and 27 patients with ocular hypertension (OHT). Blue-on-yellow (B-Y) and standard (W-W) perimetry was undertaken with a modified Humphrey Field Analyzer 640 on one eye of each subject and patient. The B-Y data were corrected for individual ocular media absorption. Results were compared to an age-matched normal database of 50 subjects (age range, 60 to 82 years; mean age, 70.0 years; SD, 6.4 years). Visual field indices and total and pattern deviation probability maps were calculated for both W-W and B-Y fields., Results: The B-Y normal database exhibited increased between-subject variability compared to the W-W normal database (P < 0.001). The greater variability increased with the increase in eccentricity (P < 0.001) and with the increase in age (P = 0.032). All patients with POAG exhibited B-Y field loss; 11 demonstrated greater B-Y loss than the corresponding W-W field. In advanced POAG, the B-Y and the W-W fields were similar. Twenty-five of the 27 normal subjects exhibited normal B-Y fields. Five of the 27 patients with OHT manifested B-Y focal abnormality and a normal W-W field: in two, W-W focal loss subsequently developed., Conclusions: Short-wavelength-sensitive perimetry can identify visual field loss before that detected by W-W perimetry. However, the increased between-subject variability necessitates stringent statistical analysis in the definition of abnormality.

Purpose: To determine the influence of macular pigment absorption on blue-on-yellow perimetry using a technique suitable for application with the Humphrey Field Analyzer., Methods: The sample comprised one eye from each of 46 healthy subjects (age range, 20-80 years). Macular pigment absorption was assessed by measuring medium-wavelength sensitive cone sensitivity for 460- and 570-nm narrowband stimuli at the fovea, at 5.5 degrees and at 8 degrees eccentricity. The differences in sensitivities recorded between the fovea and 8 degrees eccentricity and between 5.5 degrees and 8 degrees eccentricity for the 460-nm stimulus relative to a value of zero at 570 nm were attributed to absorption by the macular pigment. Blue-on-yellow perimetry was undertaken using a 460-nm narrowband blue Goldmann size V stimulus and a yellow 330-cdm-2 background., Results: Group macular pigment absorption (mean +/- standard error) was 0.40 +/- 0.03 log units foveally and 0.00 +/- 0.03 log units at 5.5 degrees eccentricity. The group mean foveal macular pigment absorption was significantly different from zero (P < 0.01). The coefficient of repeatability for the macular pigment absorption procedure (based on test-retest data for 16 subjects) was +/- 0.28 log units at the fovea and +/- 0.35 log units at 5.5 degrees eccentricity., Conclusion: The net effect of ocular media and macular pigment absorption relative to 460 nm was to attenuate the blue-on-yellow visual field at the fovea by approximately 0.80 log units and elsewhere by 0.40 log units.

Purpose: The influence of cataract on the blue-on-yellow visual field is unknown. The aim of the study was to compare the effect of age-related cataract on the normal blue-on-yellow (B-Y), yellow-on-yellow (Y-Y) and white-on-white (W-W) visual field., Methods: Forty normal subjects (age range, 60 to 81 years) randomly performed B-Y, Y-Y, and W-W perimetry using a modified Humphrey Field Analyser 640 (HFA) (Program 24-2). Twenty age-matched patients with cataract underwent the same testing paradigm. Cataract was classified using the LOCS II system. Ocular media absorption was measured with the HFA by determining the difference in scotopic sensitivity to 410-nm and 560-nm stimuli. Forward light scatter was measured by the direct compensation technique of van den Berg. Unweighted mean deviation (MD), short-term fluctuation, and corrected pattern standard derivation indices were calculated for each patient with cataract for each of the three stimulus combinations., Results: Cataract produced an adverse effect on the MD (i.e., a more negative MD) in all patients for each of the three stimulus combinations. The magnitude depended on the degree and type of cataract and was highly correlated with forward light scatter. The attenuation in sensitivity was greatest for the B-Y and W-W stimulus combinations; the B-Y field was preferentially affected by posterior subcapsular cataract and the W-W field by anterior cortical cataract., Conclusions: Cataract predominantly causes a general reduction in B-Y sensitivity. Caution therefore needs to be exercised in the interpretation of the B-Y visual field in patients in whom glaucoma and cataract coexist.

The study investigated the effects of induced forward light scatter on the normal blue-on-yellow perimetric profile. Light scatter was induced using 0.00%, 0.08% and 0.16% suspensions of 500-nm-diameter polystyrene microspheres contained in optical cells. White-on-white, yellow-on-yellow and blue-on-yellow perimetry was performed using a modified Humphrey Field Analyser 640. Fifteen subjects performed perimetry with each of the scatter suspensions placed before the eye and in the cell-free situation. The degree of induced scatter for each cell was quantified using the direct compensation technique of van den Berg at small, medium and large angles of scatter. Straylight increased and perimetric sensitivity decreased with increase in scatter concentration. Forward light scatter caused a general reduction in sensitivity for all stimuli, particularly for the blue-on-yellow stimulus. This finding may have implications for the interpretation of the glaucomatous visual field in the presence of forward light scatter.

Static differential light thresholds were measured as a function of stimulus size (Goldmann sizes I-V) along four visual field meridia (75, 165, 255 and 345 degrees) with the Humphrey Field Analyzer 640. Data were obtained for both young (n = 10, age 23.6 +/- 2.9 years) and elderly (n = 10, age 72.0 +/- 5.2 years) normal subjects. The resulting peripheral spatial summation curves could be equated to the foveal data simply by a change in size scale, which increased linearly with eccentricity. E2 values, expressing the eccentricity at which stimulus size must double for performance to remain comparable to the fovea, were in the order of 3-9 degrees. Whilst the rate of scale change is approximately the same for both young and elderly observers, differences in performance can be explained by a combination of lower sensitivity and a bias in sensitivity towards larger stimulus sizes with increasing age.

A new strategy for threshold estimation, FASTPAC, has been introduced for the Humphrey Field Analyser with the aim of improving the efficiency of visual field examination without loss of accuracy. FASTPAC was compared to the standard 4-2 double staircase strategy in 98 normal volunteers (age 23-83 years). One eye of each subject was examined with both strategies on two visits using Program 30-2. The order of strategy was randomised. FASTPAC examination time was 43% faster than the standard algorithm, but the mean sensitivities were similar. Short-term fluctuation was 24% higher with FASTPAC (P < 0.001). Most parameters were adversely affected by increasing age. FASTPAC offers a valid alternative to the standard strategy in the examination of suspected normal fields and should always be considered as an alternative to the threshold-related screening strategies. The performance of the algorithm in the identification of field loss and in areas of reduced sensitivity awaits further study.

Purpose: A new fast strategy for the estimation of threshold, FASTPAC, has been introduced for the Humphrey Field Analyzer. The aim of this study is to evaluate the performance, in a glaucomatous population, of FASTPAC compared with the standard full-threshold 4-2-decibel (dB) double-staircase strategy., Methods: The sample consisted of 30 glaucoma patients experienced in automated perimetry, ranging in age from 26 to 84 years. One eye of each patient was examined with both strategies using program 24-2, target size III. The order of strategy was randomized for each patient. The results were analyzed using analysis of covariance for a two-period crossover trial. Mean deviation, pattern standard deviation, short-term fluctuation, corrected pattern standard deviation, number of stimulus presentations, and examination time were analyzed separately; test sequence and severity of field loss were considered as between subject factors and age as a covariate., Results: The FASTPAC algorithm demonstrated a 36% saving in examination time (P < 0.001), a lower mean deviation (0.91 dB) (P < 0.001), and a greater short-term fluctuation (0.64 dB) (P = 0.008). The differences in mean deviation (P = 0.015) and short-term fluctuation (P = 0.033) became greater with an increase in age. As the severity of the field loss increased, the short-term fluctuation increased (P = 0.043), and examination time was increased for the FASTPAC strategy, while it became shorter for the standard full-threshold strategy (P = 0.033)., Conclusions: The FASTPAC strategy reduced the examination time but exhibited a decreased estimate of field severity and a greater intra-test variance.

Purpose: The distribution of sensitivity across the visual field, as determined by automated threshold static perimetry, can be summarized in terms of visual field indices. Such indices can be weighted for the variation in threshold at each eccentricity. The aims of this study were to determine the influence of the weighting factor, the relationship between the unweighted indices derived from Programs 30-2 and 24-2, and the relationship between the number of double determinations of threshold and the magnitude of the short-term fluctuation., Methods: One visual field derived by Program 30-2 of the Humphrey Field Analyzer was selected from each of 60 consecutive patients with primary open-angle glaucoma. The first two fields from each individual patient were avoided. Unweighted visual field indices were calculated and compared with the Program 30-2 weighted indices using an assessment of agreement evaluated with respect to the 95% confidence limits of the population., Results: The weighting function had no influence on the mean deviation, but it caused a slight reduction in the short-term fluctuation and an elevation in the pattern and corrected pattern standard deviations. There was little difference between the indices generated by Programs 30-2 and 24-2. The short-term fluctuation increased with an increase in the number of double determinations of threshold., Conclusions: The weighting function had little clinical influence on the visual field indices. The indices derived from Programs 30-2 and 24-2 were similar, and the short-term fluctuation would better reflect the intratest variability if all available double determinations of threshold were used to calculate the index.

The various stimulus parameters offered by two standard automated projection perimeters [Humphrey Field Analyser 630 (HFA) and Octopus 201], namely, stimulus size and location and the interaction of adaptation level and stimulus duration, were compared in a sample of 20 patients attending a glaucoma clinic using the visual field indices mean defect (MD), loss variance (LV), short-term fluctuation (SF) and corrected loss variance (CLV). LV and SF were greater with Octopus program 32 compared with Octopus program G1 (P < 0.02). No difference in the indices was found between stimulus sizes I and III for HFA program 30-2. MD was greater for program 30-2 compared with program 32 (P < 0.002) when expressed in terms of log (L/delta L) whereas LV (P < 0.02) and SF (P < 0.02) were greater for program 32. All differences were considered to be negligible in the clinical sense.

Purpose: To develop a suitable mathematical model for the description of the pointwise distribution of sensitivity across the visual field in glaucoma., Methods: The pointwise distribution of sensitivity at any given stimulus location for any given examination was described by a joint topographical and longitudinal model. The topographical element modeled the pointwise distribution of sensitivity using a second-order polynomial function in terms of the respective stimulus coordinates whereas the longitudinal element modeled the pointwise distribution of sensitivity using multiple linear regression in terms of the sensitivity at the given location determined at one or more previous examinations. The sample comprised Humphrey Field Analyser (Humphrey Instruments, San Leandro, CA) Program 30-2 and 24-2 fields from 49 patients attending a glaucoma clinic for an average of 3 years., Results: The constant term of the polynomial correlated highly with the mean deviation and moderately with the pattern standard deviation. The goodness-of-fit between the modeled and the measured field increased as an exponential function of the number of previous examinations. The median R2 was 19.6% for the first examination and 83.6% for the sixth examination. The group median optimum percentage of error between the measured and modeled sensitivity at each test location was below 10% (i.e., less than 3 dB), increased with increase in eccentricity, was greater at the extremities of the superior field and varied as a function of the severity of the field loss., Conclusion: The model seems to be a promising way to evaluate visual field progression.

Purpose: The authors used a method of spatial scaling to quantify the eccentricity-related decline in differential light sensitivity as a function of visual field meridian and age., Methods: Differential light threshold at the fovea was measured in two groups of subjects of differing age (young mean age, 23.6 yr; standard deviation, 2.4 yr; elderly mean age, 69.6 yr; standard deviation, 6.2 yr) using a Goldmann size I stimulus moving across fixation at 1 degree/sec. With luminance kept constant, eccentricity thresholds for kinetic stimuli of increasing magnification were then measured. The results were analyzed in terms of the E2 value, which specifies the eccentricity at which the stimulus size must double to maintain performance equivalent to that at the fovea., Results: For the young subjects, eccentricity thresholds increased linearly with an increase in stimulus diameter for most meridians. E2 varied between 5-12 degrees, depending on the meridian, and showed the same meridional trend as that of retinal ganglion cell distribution, although the magnitudes of E2 were different. For the elderly subjects, the eccentricity thresholds increased in a nonlinear manner with the stimulus diameter., Conclusions: Further factors, such as spatial summation, must also determine the eccentricity dependence of the differential light threshold because ganglion cell density decreases at a much faster rate than the differential light threshold. The most marked effects of age on differential light sensitivity occur at the fovea and beyond 20 degrees in the peripheral field, with a relative sparing in the pericentral area.

The effects of age, stimulus size, meridian, and eccentricity on physiologic statokinetic dissociation were investigated in clinically normal subjects using the Humphrey field analyzer (HFA, model 640), an automated perimeter capable of both static and kinetic perimetry. The right eyes of 20 age-matched young and 20 age-matched elderly volunteers was examined along the 15 degrees and 195 degrees meridians with six Goldmann size I and five size III kinetic stimuli. These were chosen to produce a spread of discrete eccentricities. Kinetic sensitivity was determined seven times for each stimulus, and the mean stimulus locations were expressed in terms of their x and y coordinates. Static sensitivity for each stimulus size then was determined seven times at each of the corresponding locations using a custom threshold program. The area under each sensitivity gradient was determined using the trapezium rule. Group mean kinetic sensitivity was greater than group mean static sensitivity (P < 0.001), and this difference was largely independent of age, stimulus size, meridian, and eccentricity.

The effects of phase of eye test and order of eye examined were investigated in 38 normal subjects using a customized 30-point central threshold program of the Humphrey Field Analyzer 640. This program, designed to be completed within 5 minutes, was successively repeated three times for each eye (i.e., three phases for each eye) at two visits separated by an interval of approximately 2 weeks. Both global and pointwise group mean sensitivity decreased in a time-related manner, deterioration being greater for the second eye at each visit, for both 200 ms and 100 ms stimulus durations.

Light scatter was induced in 15 glaucoma patients, exhibiting clear media and moderate field loss, using cells containing varying concentrations of 0.5 microns diameter latex beads in distilled water. The right eye was examined with program G1 on the Octopus 201, and with a 45 degrees threshold profile on the Dicon AP3000, with and without a given cell. Forward light scatter due to the cell was assessed by measuring the depression of contrast sensitivity, with the Nicolet CS2000, under glare conditions. Perimetric mean sensitivity decreased linearly and loss variance decreased curvilinearly with increase in forward scatter. Threshold values for 26 glaucoma patients, determined in the absence of induced scatter, were then corrected for the effects of naturally occurring intraocular light scatter. The recalculated mean defect decreased linearly while loss variance remained essentially unchanged. Forward light scatter therefore predominantly exaggerates diffuse loss; the apparent underestimation of focal defects caused by induced scatter is partly a computational artefact resulting from inapplicable age-matched normal reference data.

The influence of a socially acceptable dose of alcohol (mean blood alcohol level approximately 90 minutes after ingestion 69.5 mg%; SE 6.20 mg%) on the central visual field as determined by automated static perimetry was investigated in 17 female subjects (17 eyes) trained in automated perimetry (mean age 22.5 years, SE 1.29 years). Central visual field examination was undertaken on the right eye with program 30-2 (stimulus size III) of the Humphrey Field Analyser 630, using a simple cross-over placebo design. Alcohol produced a small (1.0 dB) but statistically significant decrease in the mean deviation (P = 0.002) and small increases (0.6 dB) in the pattern and corrected pattern standard deviations (P = 0.003 and P = 0.046, respectively). The number of stimulus presentations increased by 6% (P = 0.006) and the number of false-negative responses also increased (P = 0.019), indicating impaired patient response. Attenuation of sensitivity as a result of alcohol increased with the increase in eccentricity (P = 0.046) independently of the meridian (P = 0.068) from a mean of 0.8 dB at 3 degrees eccentricity to 1.84 dB at 27 degrees.

The influence of prior perimetric experience on the magnitude of both differential sensitivity and the short and long term fluctuations remains unclear, and confounds accurate interpretation of visual field data obtained by computer-assisted perimetry. The purpose of the experiment was to identify and quantify any influence of training on the automated perimetric response. The full field of the right eye of 10 clinically normal, naive subjects was examined on 8 occasions with Octopus Program 21 (target size 3) on days 1-5 inclusive, 15, 16 and 44. Sensitivity increased with serial examination in 8 subjects. By dividing the field into zones, it was demonstrated that the learning effect was greatest in the superior field and for eccentricities beyond 30 degrees.

The influence of the learning effect on the outcome of automated perimetry was studied as a function of eccentricity. The same comprised 20 patients with suspected glaucoma who were all naive to automated perimetry. Visual field examination of the right eye followed by that of the left eye was undertaken on each of three successive days and after a further interval of 12 days using a customized full-field program of the Humphrey Field Analyser 630 (stimulus size III). The program comprised 60 points out to an eccentricity of 60 degrees with an interstimulus grid of 12 degrees. Global, central, peripheral, superior and inferior mean sensitivity each significantly increased (P less than or equal to 0.01) from the first to the second right eye examinations and from the third to the fourth left eye examinations (P less than or equal to 0.01). The global short-term fluctuation, central mean defect and number of stimulus presentations decreased from the first to the second right eye examination (P 0.01). The order of examination between eyes and the interval between examination sessions influences the response recorded by automated perimetry.

Computer assisted perimetry has revolutionised the investigation of the visual field. Experience of central field assessment with the Octopus Automated Perimeter shows that sensitivity recorded with target size 3 across all age groups can frequently be greater than the published normative values. Use of the latter values can therefore provide a serious underestimation of field loss. Inter-individual variation in sensitivity is found within and between age groups. The limitations associated with the use of the measurement error to define abnormality and the additional problems of hypernormal thresholds and resolution of the blind spot are discussed. It is suggested that methods should be developed to evaluate sensitivity on an intra-individual basis.

The nature of the interaction between spatial summation and M-scaling was investigated by means of the Octopus automated perimeter. It was found that M-scaling of spatial stimulus parameters, alone, did not result in the expected isosensitivity profile. A clinically flat profile was, however, obtained within the central 30 degrees along the horizontal meridian using a large uniform size target (size 3; projected diameter 0.431 degrees). The eccentricities at which presentation of the standard Goldmann targets would result in an isosensitivity profile across the full extent of the visual field were calculated to further illustrate the over-compensation inherent in the current M-scaling equations.

A comparative evaluation of the Octopus automated perimeter (Programmes 21 and 31), the Goldmann Bowl perimeter, the Bjerrum Screen and the Friedmann VFAs Mk I and Mk II was carried out on a heterogeneous sample of 75 patients. Field loss was categorized using a modification of the classifications proposed by Greve (1982). The results were analysed using the Level 4 analysis developed by Flanagan, Wild, Barnes, Gilmartin, Good and Crews (1984a). The performance of the various test logics was found to differ between the categories of field defect.

Sophistication of computer software and flexibility of stimulus and background luminance parameters in static perimeter design offer the opportunity for increased information in the assessment of the visual field. Relationships between dynamic ranges and resulting sensitivity gradients in a group of 10 normal 21 year old subjects using the Octopus automated perimeter, the Dicon Autoperimeter 2000 and the Friedmann VFA II are assessed. Inadequacies in the use of normative data to assess the visual field are noted. Implications for the use of dynamic range/sensitivity gradient relationships in visual field assessment without reliance on normative data are discussed.

Previous methods for the qualitative evaluation of visual field instruments are subject to certain limitations. A system is proposed to overcome these deficiencies. It has been developed from experiences of a clinical study involving 5 different visual field instruments. The method uses 4 levels of analysis and permits separate appraisals of diagnostic potential and detailed inter-instrument comparative evaluation.

The attenuation of the perimetric response arising from cataract was investigated and related to the degree of cataract quantified by glare sensitivity. Visual fields were measured with the Octopus and Dicon automated perimeters out to an eccentricity of 30 degrees. Nuclear and non-nuclear cataracts differed in their effect on the perimetric profile. Non-nuclear cataracts exhibited the same qualitative characteristics as a model developed in previous studies, whereby the overall pattern of perimetric attenuation was dependent upon target configuration. For these subjects, perimetric sensitivity was depressed to a greater extent at an eccentricity of 30 degrees compared with fixation when measured with the large projected stimuli, whereas the reverse was true when sensitivity was measured with the small LED stimuli. Conversely, nuclear cataracts depressed perimetric sensitivity to a greater extent at the fovea compared with more peripheral regions for both the large projected and small LED stimuli.

The study investigated the effect of three distinct types of stimulus configuration on the format of the normal sensitivity gradient derived by computer assisted perimetry namely: projected stimuli; light emitting diodes (LED) with the same luminance as the perimeter bowl; and 'black hole' LED stimuli. The study comprised two separate parts: 22 age matched subjects were examined with the Dicon AP3000 and with the Topcon SBP-1000 along the 15 degrees-195 degrees meridian of the visual field of the right eye; a further 22 subjects matched for age and gender were examined along the same meridian in an identical manner with the Dicon AP2025 and with the Humphrey Field Analyser 620. The various stimulus parameters were chosen in order to provide uniformity as far as possible between the instruments. The Topcon evoked greater relative sensitivity than the Dicon at all eccentricities although the rate of change of sensitivity with increase in peripheral angle varied between the two instruments at different locations. Centrally the Dicon profile followed more closely that of Humphrey stimulus size II and beyond 5 degrees that of stimulus size I. The Topcon profile followed that of the Humphrey stimulus size II both centrally and peripherally in spite of being geometrically closer to the size III stimulus. It is proposed that the variations in the sensitivity gradient are not exclusively related to stimulus size and spatial summation; the accommodative stimulus of the 'black hole' LED stimuli, stimulus colour and thresholding strategy may all be contributing factors.

The development of automated perimetry represents one of the major opportunities for clinical advancement over the last 30 years. Compared with the data obtained from equivalent manual procedures, the technique now makes feasible a rapid and reliable static threshold investigation of the visual field and, as a result, has revolutionized the potential of the visual field examination in the diagnosis of ocular and neuro-ophthalmic abnormality. Several perimeters are commercially available, each featuring a variety of stimulus parameters for investigating the visual field and a range of data reduction techniques and displays to aid the clinician in the interpretation of abnormality. The choice of stimulus, however, governs the format of the derived field and thus the efficiency of detecting and assessing a given field defect. In addition, patient-specific variables also influence the visual field profile. This review outlines the techniques used in automated perimetry. In particular, the rationale is summarized for the choice of the major stimulus parameters employed by a given perimeter, such a stimulus type, adaptation level and testing strategy. The techniques available for data display and reduction are reviewed and the extraneous factors influencing the format of the normal differential sensitivity gradient are discussed.