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Background/aims: Preschool screening for amblyopia has controversially been abandoned in some localities within the United Kingdom, on the basis that there is no clear evidence of benefit to support its [...]

Aim: To investigate effect of patient age, gender, comorbidities and surgeon on refractive outcomes following cataract surgery., Methods: Study population: patients on UK national ophthalmic cataract database on cataract operations undertaken between 1 April 2010 and 31 August 2018. Variables examined included gender, age, diabetic retinopathy, glaucoma, high myopia, inherited retinal disease, optic nerve disease, uveitis, pseudoexfoliation, vitreous opacities, retinal pathology, cataract type, previous surgery and posterior capsular rupture. A multivariate normal cross-classified model was fitted to the refractive outcome using Markov Chain Monte Carlo (MCMC) methods with diffuse priors to approximate maximum likelihood estimation. A MCMC chain was generated with a burn-in of 5000 iterations and a monitoring chain of 50 000 iterations., Results: 490 987 cataract operations were performed on 351 864 patients by 2567 surgeons. Myopic and astigmatic errors were associated with posterior capsule rupture (-0.38/+0.04×72), glaucoma (-0.10/+0.05×95), previous vitrectomy (-0.049/+0.03×66) and high myopia (-0.07/+0.03×57). Hyperopic and astigmatic errors were associated with diabetic retinopathy (+0.08/+0.03×104), pseudoexfoliation (+0.07/+0.01×158), male gender (+0.12/+0.05×91) and age (-0.01/+0.06×97 per increasing decade). Inherited retinal disease, optic nerve disease, previous trabeculectomy, uveitis, brunescent/white cataract had no significant impact on the error of the refractive outcome. The effect of patient gender and comorbidity was additive. Surgeons only accounted for 4% of the unexplained variance in refractive outcome., Conclusion: Patient comorbidities and gender account for small but statistically significant differences in refractive outcome, which are additive. Surgeon effects are very small., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY. Published by BMJ.)

Background: There are more than one million National Health Service visits in England and Wales each year for patients with glaucoma or ocular hypertension (OHT). With the ageing population and an increase in optometric testing, the economic burden of glaucoma-related visits is predicted to increase. We examined the conversion rates of OHT to primary open-angle glaucoma (POAG) in England and assessed factors associated with risk of conversion., Methods: Electronic medical records of 45 309 patients from five regionally different glaucoma clinics in England were retrospectively examined. Conversion to POAG from OHT was defined by deterioration in visual field (two consecutive tests classified as stage 1 or worse as per the glaucoma staging system 2). Cox proportional hazards models were used to examine factors (age, sex, treatment status and baseline intraocular pressure (IOP)) associated with conversion., Results: The cumulative risk of conversion to POAG was 17.5% (95% CI 15.4% to 19.6%) at 5 years. Older age (HR 1.35 per decade, 95% CI 1.22 to 1.50, p<0.001) was associated with a higher risk of conversion. IOP-lowering therapy (HR 0.45, 95% CI 0.35 to 0.57, p<0.001) was associated with a lower risk of conversion. Predicted 5-year conversion rates for treated and untreated groups were 14.0% and 26.9%, respectively., Conclusion: Less than one-fifth of OHT patients managed in glaucoma clinics in the UK converted to POAG over a 5-year period, suggesting many patients may require less intensive follow-up. Our study provides real-world evidence for the efficacy of current management (including IOP-lowering treatment) at reducing risk of conversion., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: To investigate the impact of EyeSi surgical simulators on posterior capsule rupture (PCR) rates of cataract surgery performed by first and second year trainee surgeons., Design: A Royal College of Ophthalmologists' National Ophthalmology Database audit study of first and second year surgeons' PCR rates over seven consecutive National Health Service (NHS) years. Participating centres were contacted to ascertain the date when their surgeons had access to an EyeSi machine and whether this was on-site or off-site. Operations were classified as before, after or no access to EyeSi., Setting: The study took place in 29 NHS Ophthalmology Units in a secondary care setting., Results: Two-hundred and sixty five first and second year trainee surgeons performed 17 831 cataract operations. 6919 (38.8%) operations were performed before access to an EyeSi, 8648 (48.5%) after access to an EyeSi and 2264 (12.7%) operations by surgeons with no access to an EyeSi. Overall, there was a 38% reduction in the first and second year surgeon's unadjusted PCR rates from 4.2% in 2009 to 2.6% in 2015 for surgeons with access to an EyeSi, and a 3% reduction from 2.9% to 2.8% for surgeons without access to an EyeSi. The overall first and second year unadjusted PCR rates for before, after and no access to EyeSi were 3.5%, 2.6% and 3.8%, respectively. The decrease in the with-access to an EyeSi group PCR rate was similar for surgeons with access to an EyeSi 'on site' or 'off site'., Conclusions: First and second year trainee surgeons' unadjusted PCR rates have decreased since 2009 which has significant benefits for patients undergoing cataract surgery. This 38% reduction in complication rates aligns with the introduction of EyeSi simulator training., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Presentation with advanced glaucoma is the major risk factor for lifetime blindness. Effective intervention at diagnosis is expected to minimise risk of further visual loss in this group of patients., Aim: To compare clinical and cost-effectiveness of primary medical management compared with primary surgery for people presenting with advanced open-angle glaucoma (OAG)., Methods: Design : A prospective, pragmatic multicentre randomised controlled trial (RCT)., Setting: Twenty-seven UK hospital eye services., Participants: Four hundred and forty patients presenting with advanced OAG, according to the Hodapp-Parish-Anderson classification of visual field loss., Intervention: Participants will be randomised to medical treatment or augmented trabeculectomy (1:1 allocation minimised by centre and presence of advanced disease in both eyes)., Main Outcome Measures: The primary outcome is vision-related quality of life measured by the National Eye Institute-Visual Function Questionnaire-25 at 24 months. Secondary outcomes include generic EQ-5D-5L, Health Utility Index-3 and glaucoma-related health status (Glaucoma Utility Index), patient experience, visual field measured by mean deviation value, logarithm of the mean angle of resolution visual acuity, intraocular pressure, adverse events, standards for driving and eligibility for blind certification. Incremental cost per quality-adjusted life-year (QALY) based on EQ-5D-5L and glaucoma profile instrument will be estimated., Results: The study will report the comparative effectiveness and cost-effectiveness of medical treatment against augmented trabeculectomy in patients presenting with advanced glaucoma in terms of patient-reported health and visual function, clinical outcomes and incremental cost per QALY at 2 years., Conclusions: Treatment of Advanced Glaucoma Study will be the first RCT reporting outcomes from the perspective of those with advanced glaucoma., Trial Registration Number: ISRCTN56878850, Pre-results., Competing Interests: Competing interests: TAGS is funded by the National Institute for Health Research Health Technology Assessment (NIHR HTA) programme (project number 12/35/38). JMB, GM, AM and JMS report grants from NIHR Health Technology Assessment Programme during the conduct of the study. LV reports grants from NIHR HTA Programme during the conduct of the study; and membership of the NIHR Health Technology Assessment Programme and a director of the NIHR Research Design Service. JN reports grants from NIHR HTA during the conduct of the study; personal fees from NIHR Editors Board, other from NIHR HTA General Board, outside the submitted work., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Aims: To explore trends over time and variation in the use of anaesthetic techniques for vitreoretinal (VR) surgery in the UK., Methods: Prospectively collected data from 13 centres contributing >50 VR operations, including either pars plana vitrectomy (PPV) or scleral buckle (SB), between May 2000 and November 2010 were retrospectively analysed. Anaesthesia was categorised as general anaesthesia (GA) or local anaesthesia (LA) and results were reported by year, centre, grade of surgeon and type of operation., Results: 160 surgeons performed 12 124 operations on 10 405 eyes (9935 patients); 6054 (49.9%) under GA and 6070 (50.1%) under LA. The percentage performed under GA decreased from 95.3% in 2001 to 40.9% in 2010. Within LA techniques, peribulbar or retrobulbar injection was used in 2783 (45.8%) operations and sub-Tenon's cannula in 3287 (54.2%). The proportions of operations performed under GA or LA were similar for consultants and trainees. Primary SB, primary combined PPV and SB for retinal detachment (RD), repeat RD surgery and complex vitrectomy surgery were more commonly performed under GA (85.8%, 67.0%, 63.5% and 69.4%, respectively), while primary PPV for RD, simple vitrectomy surgery and macular surgery were more commonly performed under LA (58.1%, 53.7% and 58.2%, respectively). Marked intercentre variation existed with the extremes being one centre with 100% of operations performed under GA and one centre with 98.3% under LA., Conclusions: LA for VR surgery has steadily increased over the last decade in the UK but marked intercentre variation exists., (Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/)

Aim: To assess a two-phase method of recording levator function in order to facilitate the identification of patients with ptosis who have a synkinesis between the levator and superior rectus muscles., Methods: 40 consecutive patients who attended oculoplastic clinics with ptosis and 22 patients with normal lid function were recruited. In each subject, levator function was recorded by the conventional method, measuring total upper eyelid excursion between the extremes of down-gaze and up-gaze. Levator function was also assessed using our novel two-phase approach in which upper-eyelid excursion is measured separately between down-gaze and primary position (Phase 1), and between primary position and up-gaze (Phase 2)., Results: In normal patients and most of the patients with ptosis, the majority of lid movement and hence levator function occurs between down-gaze and the primary position (Phase1). In those patients with ptosis and levator-superior rectus synkinesis, a higher proportion of lid movement occurred on up-gaze (Phase2)., Conclusion: The two-phase measurement of lid movement highlights levator function in differing gaze positions and facilitates the identification of those patients with levator-superior rectus synkinesis.

Aims: To derive an evidence base for the efficacy of two novel optometric primary eye care services in Wales, the Primary Eyecare Acute Referral Scheme (PEARS) and the Welsh Eye Health Examination (WEHE)., Methods: A Donabedian model using structure, process and outcome was applied to evaluate prospectively 6432 individuals attending 274 optometrists within an 8-month period. Telephone interviews and review of optometric and hospital notes were used to determine management appropriateness for patients either managed in optometric practice or referred to the Hospital Eye Service (HES). A Geographic Information Systems analysis determined distances travelled to the optometrist. A cost analysis was used to determine the net cost of the schemes., Results: 4243 (66%) of the 6432 individuals were managed in optometric practice; inappropriate management was apparent in 1% of individuals. 392 hospital notes were reviewed; 75% exhibited appropriate optometric referrals to the HES. 87% of individuals travelled less than 5 miles to attend an optometrist. The net cost of a PEARS/WEHE consultation was a minimum of pound12., Conclusions: Optometric management within the schemes is acceptable. Good equity of access was achieved at a relatively low net cost per consultation. Agreement on protocols for referral to the HES would enhance the schemes.

Background: Higher or equal rates of mortality are associated with cataract surgery compared with the general population. Cataract surgery has advanced, and the clinical characteristics of the patient undergoing cataract surgery have changed., Aims: To reinvestigate survival following cataract surgery., Method: Survival data were gathered up to the end of 2006 on 933 consecutive patients who underwent cataract surgery between December 2000 and February 2001. These data were compared with national and regional mortality figures, and standardised mortality ratios (SMR) were calculated., Results: After adjusting for age and sex, there was a statistically significant reduced mortality compared with national (SMR = 0.88 (95% CI 0.79 to 0.99)) and regional figures (SMR = 0.87 (95% CI 0.78 to 0.98))., Conclusion: All previous studies found decreased survival among cataract surgery cohorts. These data differ from data at earlier times, as cataract surgery seems to be associated with increased survival. This illustrates the need for continual re-evaluation of accepted medical knowledge in the light of changes in practice and population demographics.

Objective: To estimate the distribution and predictors of some common visual problems (strabismus, amblyopia, hypermetropia) within a population-based cohort of children at the age of 7 years., Methods: Children participating in a birth cohort study were examined by orthoptists who carried out cover/uncover, alternate cover, visual acuity and non-cycloplegic refraction tests. Prospectively collected data on potential risk factors were available from the study., Results: Data were available for 7825 seven-year-old children. 2.3% (95% CI 2.0% to 2.7%) had manifest strabismus, 3.6% (95% CI 3.3% to 4.1%) had past/present amblyopia, and 4.8% (95% CI 4.4% to 5.3%) were hypermetropic. Children from the lowest occupational social class background were 1.82 (95% CI 1.03% to 3.23%) times more likely to be hypermetropic than children from the highest social class. Amblyopia (p = 0.089) and convergent strabismus (p = 0.066) also tended to increase as social class decreased., Conclusions: Although strabismus has decreased in the UK, it and amblyopia remain common problems. Children from less advantaged backgrounds were more at risk of hypermetropia and to a lesser extent of amblyopia and convergent strabismus. Children's eye-care services may need to take account of this socio-economic gradient in prevalence to avoid inequity in access to care.

Aim: To evaluate the performance of the frequency doubling technology (FDT) 24-2-5 screening test by comparison with the established N-30-5 FDT screening test for detection of glaucoma., Method: A prospective random sample of individuals referred for possible glaucoma were tested with FDT screening tests 24-2-5 and N-30-5 using the Humphrey Matrix perimeter in addition to standard clinical examination relevant to glaucoma detection. Discriminatory power, reliability and test time of these tests were assessed and compared. The case definition for glaucoma was made by patient according to the established clinical diagnosis., Results: Of 63 referred eligible individuals, 53 (84%) were recruited. Sensitivity and specificity for the N-30-5 screening test was 78 and 85% respectively, compared with 83% and 75% for the 24-2-5 with areas under a receiver operator characteristic curve being 0.87 and 0.92. Differences between these indices were not statistically significant. For a specificity of 95%, sensitivity values were 76% and 56% for the 24-2-5 and N-30-5 respectively. Mean (standard deviation) test duration for the FDT 24-2-5 and N-30-5 screening tests were 111 (13) and 39 (10) seconds respectively (p<0.001). A total of 19 subjects (36%) produced unreliable test results in one or both eyes when tested with the 24-2-5 screening test compared with 5 subjects (9%) with the N-30-5 (p<0.0005)., Conclusion: Minimal discriminatory power differences existed between the two screening tests evaluated, with both screening tests exhibiting high discriminatory power for detection of individuals with glaucoma. More individuals produced unreliable results on the 24-2-5 screening, which also took longer to perform.

Aim: To describe the ultrastructural appearance of explanted opacified Hydroview H60M intraocular lenses., Methods: 14 explanted lenses were examined by scanning electron microscopy, and their appearance compared with a non-implanted H60M lens from the same time period. Wavelength-dispersive x ray spectroscopy (WDX) was performed on two opacified lenses., Results: Subsurface deposits were seen in all explanted opacified lenses. These deposits broke only onto the surface of more densely opacified lenses. WDX confirmed that the deposits contained both calcium and phosphorous, consistent with their being calcium apatite., Conclusion: These findings challenge the widely accepted opinion that H60M intraocular lens opacification begins on the surface of the optic.

Aims: To evaluate performance of frequency doubling technology (FDT) perimetry using the Humphrey Matrix 24-2 thresholding program in a hospital eye service (HES) glaucoma clinic., Methods: A random sample of individuals referred consecutively to the HES for suspected glaucoma were examined with 24-2 threshold FDT in addition to routine clinical tests. The discriminatory power of FDT and standard automated perimetry (SAP) were assessed using glaucomatous optic nerve head appearance as the reference gold standard., Results: 48 of 62 eligible referred individuals were recruited. Glaucoma prevalence was 31%. Median test duration per eye was 5 minutes 16 seconds for FDT and 5 minutes 9 seconds for SAP. There was no significant difference (p = 0.184) between proportions of individuals with reliable test results (FDT 75%, SAP 63%). Using a clinically appropriate binary criterion for abnormal visual field, sensitivity and specificity levels were 100% and 26% respectively for FDT and 80% and 52% for SAP. Both tests had higher negative than positive predictive values with marginal differences between tests. Criterion free receiver operator characteristic analysis revealed minimal discriminatory power differences., Conclusions: In a HES glaucoma clinic in which new referrals are evaluated, threshold 24-2 FDT testing with the Humphrey Matrix has performance characteristics similar to SAP. These findings suggest threshold testing using the FDT Matrix and SAP is comparable when the 24-2 test pattern is used.

Aims: To evaluate the effect of a visual field test educational video on the reliability of the first automated visual field test of new patients., Methods: A prospective, randomised, controlled trial of an educational video on visual field test reliability of patients referred to the hospital eye service for suspected glaucoma was undertaken. Patients were randomised to either watch an educational video or a control group with no video. The video group was shown a 4.5 minute audiovisual presentation to familiarize them with the various aspects of visual field examination with particular emphasis on sources of unreliability. Reliability was determined using standard criteria of fixation loss rate less than 20%, false positive responses less than 33%, and false negative responses less than 33%., Results: 244 patients were recruited; 112 in the video group and 132 in the control group with no significant between group difference in age, sex, and density of field defects. A significant improvement in reliability (p=0.015) was observed in the group exposed to the video with 85 (75.9%) patients having reliable results compared to 81 (61.4%) in the control group. The difference was not significant for the right (first tested) eye with 93 (83.0%) of the visual fields reliable in the video group compared to 106 (80.0%) in the control group (p = 0.583), but was significant for the left (second tested) eye with 97 (86.6 %) of the video group reliable versus 97 (73.5%) of the control group (p = 0.011)., Conclusions: The use of a brief, audiovisual patient information guide on taking the visual field test produced an improvement in patient reliability for individuals tested for the first time. In this trial the use of the video had most of its impact by reducing the number of unreliable fields from the second tested eye.

Aim: To evaluate the correlation between internal slope analysis of the optic nerve head and visual field changes in normal eyes and those with ocular hypertension (OHT) and early glaucoma (POAG)., Methods: One eye of each of 22 normal subjects, 21 patients with ocular hypertension, and 50 patients with glaucoma were examined using the TopSS scanning laser ophthalmoscope. A series of topographic parameters measuring the internal features of the optic discs of these patients were obtained. These findings were compared with the Humphrey visual field analysis of these patients., Results: Global topographic average slope and cup to disc ratio could discriminate between groups of normal and OHT patients (p = 0.02). All global and sector analysis parameters could discriminate normal subjects from POAG patients. The average slope parameter provided the best separation with a receiver operating characteristic curve area of 0.88. Visual field mean deviation (MD) was most closely correlated with global average slope (r = -0.60, p<10(-7)) and cup to disc ratio (r = -0.40, p<0.001). Visual field MD was also well correlated (r = -0.50, p<0.0001) with slope parameters for sectors S8, S2, and S1., Conclusion: Average slope, a parameter independent of reference planes and magnification effects, is capable of discriminating groups of OHT and POAG patients from a group of normal subjects. This topographic parameter is also well correlated with the visual field MD. Sector slope analysis suggests early glaucomatous damage may occur in the inferotemporal region of the optic disc.

Aim: To investigate the examination of lens opacities in routine ophthalmic clinical practice., Method: A questionnaire survey was mailed to 703 consultant ophthalmologists in the UK. The surgeons were asked which lens feature(s) they assessed in their clinics when deciding whether to offer cataract surgery., Results: 489 replies were received. A broad range of lens opacities was assessed, with differences between surgeons for some opacities with high prevalences in the population, particularly cortical opacities. Many (74% of 467) surgeons assessed one or more lens opacities (anterior subcapsular cataract, vacuoles, water clefts, coronary flakes, focal dots, retrodots, fibre folds) which may be visually important but which have received relatively little attention by researchers., Conclusions: Some classes of lens opacity which are traditionally measured by researchers may be ignored in clinical practice and opacities which are traditionally ignored by some researchers are regarded as clinically important by a substantial number of surgeons.

Aim: To examine the outcome of care for patients with glaucoma followed up by the hospital eye service compared with those followed up by community optometrists., Methods: A randomised study with patients allocated to follow up by the hospital eye service or community optometrists was carried out in the former county of Avon in south west England. 403 patients with established or suspected primary open angle glaucoma attending Bristol Eye Hospital and meeting defined inclusion and exclusion criteria were studied. The mean number of missed points on visual field testing in the better eye (using a "better/worse" eye analysis) in each group were measured. The visual field was measured using the Henson semiautomated central field analyser (CFA 3000). Measurements were made by the research team on all patients at baseline before randomisation and again 2 years after randomisation. The mean number of missed points on visual field testing in the worse eye, mean intraocular pressure (mm Hg), and cup disc ratio using a "better/worse" eye analysis in each group at 2 years were also measured. Measurements were made by the research team on all patients at baseline before randomisation and again 2 years after randomisation. An analysis of covariance comparing method of follow up taking into account baseline measurements of outcome variables was carried out. Additional control was considered for age, sex, diagnostic group (glaucoma suspect/established primary open angle glaucoma), and treatment (any/none)., Results: From examination of patient notes, 2780 patients with established or suspected glaucoma were identified. Of these, 752 (27.1%) fulfilled the entry criteria. For hospital and community follow up group respectively, mean number of missed points on visual field testing at 2 year follow up for better eye was 7.9 points and 6.8 points; for the worse eye 20.2 points and 18.4 points. Similarly, intraocular pressure was 19.3 mm Hg and 19.3 mm Hg (better eye), and 19.1 mm Hg and 19.0 mm Hg (worse eye); cup disc ratio at 2 year follow up was 0.72 and 0.72 (better eye), and 0.74 and 0.74 for hospital and community follow up group respectively. No significant differences in any of the key visual variables were found between the two groups before or after adjusting for baseline values and age, sex, treatment, and type of glaucoma., Conclusions: It is feasible to set and run shared care schemes for a proportion of patients with suspected and established glaucoma using community optometrists. After 2 years (a relatively short time in the life of a patient with glaucoma), there were no marked or statistically significant differences in outcome between patients followed up in the hospital eye service or by community optometrists. Decisions to implement such schemes need to be based on careful consideration of the costs of such schemes and local circumstances, including geographical access and the current organisation of glaucoma care within the hospital eye service.

Aim: To provide information on the use of vision tests in clinical decision making about cataract surgery in the UK., Method: A questionnaire survey was mailed to 703 consultant ophthalmologists., Results: A response rate of 70% was obtained. Monocular distance visual acuity was the only visual function that was tested routinely by all surgeons. Supplementary use of contrast sensitivity and glare testing was low. Many surgeons (35%) were willing to consider surgery at acuity levels better than 6/9 and a small but substantial number (12%) indicated that they did not use an acuity criterion. Being prepared to consider surgery at relatively good levels of acuity was not associated with more common use of other tests of vision., Conclusion: Many UK surgeons are prepared to consider cataract extraction at relatively good levels of visual acuity and use other vision tests infrequently.

Background/aims: Primary open angle glaucoma patients and glaucoma suspects make up a considerable proportion of outpatient ophthalmological attendances and require lifelong review. Community optometrists can be suitably trained for assessment of glaucoma. This randomised controlled trial aims to assess the ability of community optometrists in the monitoring of this group of patients., Methods: Measures of cup to disc ratio, visual field score, and intraocular pressure were taken by community optometrists, the hospital eye service and a research clinic reference "gold" standard in 405 stable glaucoma patients and ocular hypertensives. Agreement between and within the three centres was assessed using mean differences and intraclass correlation coefficients. Tolerance limits for a change in status at the level of individual pairs of measurements were also calculated., Results: Compared with a research clinic reference standard, measurements made by community optometrists and those made in the routine hospital eye service were similar. Mean measurement differences and variability were similar across all three groups compared for each of the test variables (IOP, cup to disc ratio, and visual field). Overall, the visual field was found to be the most reliable measurement and the cup to disc ratio the least., Conclusions: Trained community optometrists are able to make reliable measurements of the factors important in the assessment of glaucoma patients and glaucoma suspects. This clinical ability should allow those optometrists with appropriate training to play a role in the monitoring of suitable patients.

Aims: To create a clinically useful classification for post-keratoplasty corneas based on corneal topography., Methods: A total of 360 topographic maps obtained with the TMS-1, from 95 eyes that had undergone penetrating keratoplasty (PKP), were reviewed independently by two examiners in a masked fashion, and were categorised according to a proposed classification scheme., Results: A high interobserver agreement (88% in the first categorisation) was achieved. At 12 months post-PKP, a regular astigmatic pattern was observed in 20/85 cases (24%). This was subclassified as oval in three cases (4%), oblate symmetric bow tie in six cases (7%), prolate asymmetric bow tie in six cases (7%), and oblate asymmetric bow tie in five cases (6%). An irregular astigmatic pattern was observed in 61/85 cases (72%), subclassified as prolate irregular in five cases (6%), oblate irregular in four cases (5%), mixed in seven cases (8%), steep/flat in 11 cases (13%), localised steepness in 16 cases (19%), and triple pattern in three cases (4%). Regular astigmatic patterns were associated with significantly higher astigmatism measurements. The surface asymmetry index was significantly lower in the regular astigmatic patterns., Conclusions: In post-PKP corneas, the prevalence of irregular astigmatism is about double that of regular astigmatism, with a trend for increase of the irregular patterns over time.

Aims: To evaluate intra- and interobserver variability in measurements on normal and astigmatic corneas with keratometry and computerized videokeratography., Methods: Keratometric readings with the 10 SL/O Zeiss keratometer and topographic maps with the TMS-1 were obtained by two independent examiners on 32 normal and 33 postkeratoplasty corneas. Inter- and intraobserver coefficients of variability (COR) for measurements of steep and flat meridian power and location, in addition to the magnitude of astigmatism, were assessed., Results: Compared with TMS-1, the 10 SL/O keratometer showed a superior repeatability in measuring normal corneas (intraobserver COR for keratometry and TMS-1 respectively: 0.22 and 0.30 D for steep meridian power; 0.18 and 0.44 D for flat meridian power; 0.26 and 0.40 D for astigmatism; 5 degrees and 26 degrees for steep meridian location; 5 degrees and 13 degrees for flat meridian location). Astigmatism intraobserver COR (0.20 D and 0.26 D for the two observers) and interobserver COR (0.28 D) of the keratometer for normal corneas was very good and not affected by observers' experience. Repeatability of the TMS-1 on normal corneas was found to be: (a) observer related, and (b) astigmatism related. A novice observer showed a much greater COR (1.62 D for astigmatism, 30 degrees for flat meridian location) compared with the experienced examiner (0.40 D for astigmatism, 13 degrees for flat meridian location). Higher deviation scores were observed for corneas with higher astigmatism. For the postkeratoplasty corneas, again the keratometer achieved superior reproducibility (astigmatism interobserver COR 1.12 D for keratometry, 4.06 D for TMS-1; steep meridian location interobserver COR 10 degrees for keratometry, 34 degrees for TMS-1)., Conclusion: Keratometric readings are more reproducible than topographic data both for normal and postkeratoplasty corneas. The two instruments should not be used interchangeably especially on highly astigmatic corneas. For the TMS-1, users with the same level of experience should be employed in clinical or experimental studies.

Aims: To evaluate the reproducibility of the retardation values (change in polarisation) obtained with the scanning-laser polarimeter in a series of normal subjects and glaucoma patients. To improve the analysis of the raw data by devising and evaluating a blood vessel removal algorithm., Methods: Scanning laser polarimetry was performed on 10 normal subjects and 10 glaucoma patients. A series of six images was obtained from each eye. The normal subjects were re-imaged 3 months after their initial assessment. The retardation values obtained from each eye were analysed using the authors' own methods, including the use of an algorithm to remove blood vessels from the polar profiles. The reproducibility of these measurements and the performance of the blood vessel removal algorithm were assessed., Results: The "individual point" coefficient of variation was approximately 12.5% for normal subjects and 17.0% for glaucoma patients. The "integral" coefficient of variation for these groups was approximately 5.5% and 9.5% respectively. The reproducibility of the measurements did not improve with an increased number of measurements. There was no difference in the reproducibility of the measurements in normal subjects over time. The blood vessel removal algorithm improved the reproducibility of the measurements when the shape of the profile was assessed., Conclusion: The intraoperator reproducibility of retardation values obtained with the scanning laser polarimeter is satisfactory for its use as a clinical tool. The use of a blood vessel removal algorithm improves the reproducibility of the measurements and also assists the clinician in the interpretation of the polar profiles. Furthermore, it allows the construction of normal database polar profiles, thereby enabling the identification, location and quantification of retinal nerve fibre layer damage in an "at risk" individual's polar profile.

Aims: To devise a method to describe and quantify the shape of polar profiles obtained with the scanning laser polarimeter and to compare this measurement with other polar profile measurements in a series of normal subjects and glaucoma patients., Methods: Scanning laser polarimetry was performed on 54 normal subjects and 74 glaucoma patients. The retardation values obtained from one randomly chosen eye of each subject were analysed using our own methods, including the use of an algorithm to remove blood vessels from the polar profiles, an algorithm to standardise the glaucoma profiles to a normal database, and a further algorithm to evaluate the profile shape. The measurements of profile shape were compared with measurements of the absolute and standardised retinal nerve fibre layer thickness obtained with the scanning laser polarimeter., Results: There was no significant difference between the mean retardation values for the normal and glaucomatous subjects in either hemiretina. However, standardisation of the glaucoma retardation values to a normal database produced significant differences at p < 1 x 10-8 in the mean retardation values for these two groups in both hemiretinas. Profile shape measurement analysis produced similar significant differences between the mean retardation values for the normal and glaucomatous subjects in both hemiretinas, although the degree of separation was greater following standardisation of the retardation values., Conclusion: The use of an algorithm to standardise an individual's retardation values in conjunction with a blood vessel removal algorithm enables an improvement in the ability of the scanning laser polarimeter to discriminate between normal and glaucomatous patients. The polar profile shape algorithm is independent of standardisation and significantly improves the discrimination between normal and glaucomatous patients, as well as providing additional information regarding the retinal nerve fibre layer.

Lenticular and anterior chamber biometry were studied in non-cataractous eyes by means of Scheimpflug photography and digital image analysis. The study population consisted of 91 late onset diabetic subjects and 115 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior clear zone thickness, anterior chamber depth, and anterior and posterior lenticular curvatures were assessed. Age played an important role in determining lens biometry in all subjects, and small but significant differences were found between late onset diabetics and non-diabetics. In the late onset diabetic subgroup, apart from age, diabetic retinopathy was the only significant parameter found which determined lens biometry. These biometric findings in late onset diabetes are in marked contrast to the large overall effect of diabetes and the powerful effect of diabetic duration which we previously reported in early onset diabetes. Further analysis of the data from our previous study has been provided, which clearly demonstrates differences between the impact of early and late onset diabetes on the biometry of the anterior ocular segment.

Blue/green autofluorescence (excitation around 420 to 430 nm, emission around 520 nm) of the crystalline lens has been studied by an in vivo photographic method in two populations of diabetics and controls. The populations consisted of a geographically based survivor group of 161 mixed early and late onset diabetics (and 133 non-diabetic controls) and a second group of 104 early onset insulin dependent diabetics (and 138 non-diabetic controls), the latter all with non-cataractous lenses. Powerful associations (p less than 10(-6) were found between the presence of diabetes and increased lenticular autofluorescence in both populations. Among the mixed diabetics diabetic type was a significant factor after accounting for the effects of age and diabetic duration. In the early onset group (clear lenses) a powerful association existed between autofluorescence and diabetic duration (p = 0.000011) after allowing for the effect of age, while in a subgroup of late onset diabetics with clear lenses this effect was modest (p = 0.015). In the early onset diabetic group diabetic retinopathy (p = 0.0064) was associated with increased lenticular autofluorescence after allowing for the effects of age and diabetic duration. In addition a powerful interaction between diabetic duration and the presence of diabetic retinopathy (p less than 10(-6) was found in this subgroup. Among the geographically based population of diabetics, increased nuclear brunescence was powerfully associated (p less than 10(-6) with increased autofluorescence after allowing for the effects of age, diabetic duration, and type of diabetes. This association was not found in the non-diabetic population. Non-enzymatic glycosylation of lens proteins should be considered as a possible mechanism of production of the fluorogen with emission around 520 nm.

Lenticular biometry on non-cataractous lenses has been studied by means of Scheimpflug photography and digital image analysis in 153 patients with early-onset insulin-dependent diabetes and 153 non-diabetic controls. Anteroposterior axial lens thickness, cortical thickness, nuclear thickness, anterior and posterior lenticular curvatures, and anterior chamber depth were assessed. Highly significant differences between the lenses of the diabetic subjects and non-diabetic controls were found. After the effect of age had been accounted for within the diabetic subgroup, diabetic duration was found to be a highly significant determinant of lens dimensions, such that age-related dimensional changes for various biometric parameters were accelerated by between 52% and 121% after the onset of diabetes. Because the diabetic duration of the early-onset diabetic subjects studied in this work was accurately known, this report is the first in which a precise assessment of the effect of 'true' diabetic duration on lens biometry has been possible.

A single masked observer examined 55 non-diabetic patients chosen randomly from a population of patients who had undergone renal transplant. The mean age was 41 years and mean time from transplant was 4.4 years (1-10 years). Fourteen patients were found to have a posterior subcapsular cataract (PSC). The axial thickness of the right lens of the renal transplant population, even in the presence of a PSC, was significantly larger than in a control population of 99 patients with clear lenses. The PSC of renal transplantation is readily distinguished from age related PSC because the opacity lies in the superficial cortex at a depth proportional to time from transplant and the lens maintains a normal anterior clear zone. It is proposed that this type of cataract be called 'recovering' PSC. It is concluded that the cataractogenic insult occurs mainly during the peritransplant period. Maintenance doses of immunosuppressives or steroids are therefore probably not cataractogenic.

The size and shape of the lens fibres were estimated by specular reflex photography. The fibres were measured in three separate regions. Peripheral fibres have a mean width of 10.2 micron, the central fibres 11.9 micron, and the central fibres with suture 15.8 micron. Measurements were made of the taper (becoming narrower towards the suture) and flare (becoming wider towards the suture). The peripheral fibres have a mean taper of 0.3 micron per 100 micron. The central fibres have a mean flare of 0.6 micron per 100 micron, and the central fibres with suture have a mean flare of 2.4 micron per 100 micron. These differences are highly significant (p less than 10(-6]. From these measurements the overall shape of the average lens fibre was estimated. This fibre tapers as it passes forward from the equator to the peripheral extent of the lens sutures and then flares increasingly as the junction with the lens suture is approached. A mean increase in peripheral lens fibre width with age at 0.028 micron per year was demonstrated. This is significant (p = 0.042). No difference in fibre width was found in diabetics and non-diabetics.

Posterior subcapsular cataracts were studied in 10 patients (19 eyes) and were photographed at four to 12 weeks intervals by the Oxford Retroillumination Camera. Changes in the fine structure of PSC may occur in as short a time as four weeks. Posterior subcapsular cataracts are shown to be in a state of flux and are not, as might be assumed, slowly but relentlessly progressive. This could imply the existence of a repair mechanism in the lens.

The lens growth through life is the net result of surface accretion partially offset by central compaction. Compaction has previously been shown to affect the cortex. The present study examines compaction in the nucleus by measuring the change in dimensions of congenital lamellar cataract with time and by comparing the different dimensions of dominantly inherited lamellar cataract in individuals of different ages in the same family. It is now shown that compaction affects the nucleus at a decreasing rate with increasing age and that the rate of compaction of lamellar cataracts is faster the greater diameter of the affected lamella. It is concluded that compaction of lens fibres towards the centre of the lens affects all regions of the cortex and nucleus in youth and that the compaction becomes largely or completely confined to the cortex in middle age and beyond. The shape of the lamellar cataract changes from a lenticular shape in youth to a rounded shape with increasing age. This accounts for the development of the peripheral divergence of the zones of discontinuity of the cortex, which allows the lens to remain emmetropic with increasing age in spite of changes in surface curvature.

A study is reported on cataract surgery, with intraocular lens implant, with measurement of the preoperative astigmatism and of the postoperative astigmatism over 28 weeks. Nine interrupted 10/0 nylon sutures are used to close a limbal section. Preoperative astigmatism is compensated for in the method of suturing by the placement of additional sutures. Postoperatively sutures are cut in line with the plus cylinder axis in eyes showing excessive astigmatism with the rule. Final postoperative astigmatism is controlled within 2.25 D cyl. 68% of cases lie within 1.0 D cyl with the rule to 1.0 D cyl against the rule. The average case in which sutures are not cut is one having 1.51 D cyl with the rule at one week postoperatively, declining to zero at approximately 12 weeks, and having a final value of 0.17 D cyl against the rule. No significant change in cylinder is seen after 10 weeks. The final postoperative astigmatism is only weakly correlated with the preoperative astigmatism, showing that the surgical method is effective. The spherical equivalent error is shown to shift in the direction of myopia in the postoperative period.