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PURPOSE The purpose of this study was to investigate the utility of two ocular biometric measurements to obtain Hirschberg ratios (HRs) in a binocularly normal paediatric population, and to assess the repeatability of this approach. METHODS Ocular biometry data from 80 participants (aged 5 to 14 years) was obtained using the KM-1 LED manual keratometer and the Tomey Biometer AL-100 A-scan. HRs were calculated from corneal curvature and anterior chamber depth measurements in the horizontal and vertical meridians of each eye using a regression equation based on a geometric optics model. To assess intrasubject variability in the HRs obtained from biometry, measurements were repeated approximately 1 h later. RESULTS At the initial measurement, mean (SD, range) HRs were 10.77 (0.79, 9.14-12.73) and 11.02 (0.82, 9.48-13.32) °/mm for the horizontal and vertical meridians, respectively. There was a significant difference between the horizontal and vertical HRs (p

Objective: To evaluate the types of refractive errors in nystagmus patients among the age (5-15 years) patients. Study Design and Setting: An observational cross-sectional study was conducted at Pediatric department of Al-Ibrahim Eye Hospital, Karachi from June 2018 to March 2019. Methodology: A total of 55 patients (110 eyes) were selected from study setting. The protocol for examination for all patients were evaluated at the special clinic of Orthoptics includes the demographic data, educational status, history of onset, type of nystagmus. The anterior segment was examined with a slit-lamp to exclude any other ocular disease. Orthoptic assessment includes cover uncover test, Hirschberg, ocular motility, prism cover test and pupillary reflex test, to observe any associated deviation. All the patients were examined after obtaining a fully informed consent. After the proper diagnosis of nystagmus patient was recruited as per inclusion and exclusion criteria with no restrictions of gender. All the observations were noted on a Proforma, Data analysis was done by using SPSS version 20. P-value

To Elizabeth von Arnim, her experience of motherhood was associated with a particularly German coupling of sentimentality and brutality. This article explores the nexus between sentimentality, moth...

Purpose This study investigates the prevalence of manifest strabismus and its subtypes in adulthood and analyzes the risk factors and its impact on vision-related quality of life (VRQoL). Design The Gutenberg Health Study (GHS) is a population-based, observational cohort study. A cross-sectional analysis of the baseline examination was conducted. Participants Participants aged 35 to 74 years were included (n = 15 010). Methods All participants were examined with a comprehensive ophthalmologic and general examination including the Hirschberg corneal reflex test to detect manifest strabismus. The following risk factors were analyzed: age, sex, socioeconomic status, birth weight, maternal age at birth, anisometropia, astigmatism, spherical equivalent, low visual acuity in the worse seeing eye (≥1.3 logMAR), and cardiovascular factors, and included in multivariable logistic regression analysis. Lifetime period prevalence and point prevalence of manifest strabismus were computed, and VRQoL was compared between participants with and without strabismus. Main Outcome Measure Strabismus prevalence. Results A total of 14 700 participants (age, 55.0±11.1 years; 49.5% were female) were included in this analysis. The weighted prevalence of ever having strabismus was 2.9% (2.6%–3.2%), and the point prevalence for concomitant strabismus was 2.5% (2.3%–2.8%). Esotropia was twice as frequent as exotropia, and 2 participants had paralytic strabismus. Concomitant strabismus was associated with age 65 to 69 years (odds ratio [OR], 0.13 [0.05–0.39], P 1.0 diopters [D]: OR, 3.61 [2.32–5.62], P 2.0 D: OR, 6.93 [4.23–11.35], P Conclusions Strabismus is a frequent chronic eye condition that is associated with a lower VRQoL. Individuals with anisometropia, astigmatism, and hyperopia are more likely to have strabismus. In addition, low visual acuity in the worse eye was linked to strabismus prevalence.

Objective: The aim of the study is to determine the prevalence of different types of strabismus inprimary school children; grade one in Sohag city. Background: Strabismus is the most commonamblyogenic factor. Children with untreated strabismus and/or amblyopia will lack the ability to fullydevelop binocular single vision. They may have psychosocial difficulties later in life. Design: A crosssectional study was employed to determine the prevalence of strabismus among primary schoolchildren (grade one) in Sohag city from November 2017 to April 2018. Methods: Visual acuity,autorefraction, Hirschberg's test and cover test using a pen light torch were performed for 584 out of 841students (age range 5.5–7 years). Children with any type of strabismus or had a history of strabismussurgery were subjected to a full ophthalmic examination including slit lamp, extraocular musclesexamination, Worth 4 dots test, and fundus examination. Results: Students with strabismus are 8 of 584students. Four of them are boys and the others are girls. Three of the detected cases are esotropias (twoboys and one girl) with a prevalence of 0.5%. The other five detected cases are distributed as threecases of exophorias (two girls and one boy) with a prevalence of 0.5% and two cases of esophorias (onegirl and one boy) with a prevalence of 0.3%. In the present study, 506 students (255 males and 251females) are emmetropic (< ± 1.00 D) with a percentage of 86.6% and the other 78 students (40 malesand 38 females) are with refractive errors with a percentage of 13.4%. Most of them are with astigmatism(9.3%) then myopia (2.9%) and hypermetropia (1.2%). Conclusion: In this study, the prevalence ofstrabismus in children at school age in Sohag city is 1.4% with no statistically significant association withgender.

Background Hemispherotomy, which involves disconnecting hemispherical fibers, is a treatment option for medically intractable epilepsy. As various neurological disorders can cause strabismus, we hypothesized that hemispherotomy can cause post-operative strabismus in patients with medically intractable epilepsy. Methods Nineteen patients underwent the Hirschberg test before and after hemispherical disconnection surgery. Among the 19 patients, 16 patients (six females and 10 males; mean age, 12.2 years; range, 0.17–43 years) who underwent hemispherotomy were included in this study. Results The difference in the angle between the left and right eyes was significantly widened (p = 0.025). Nine (56%) of 16 patients exhibited post-operative chronic strabismus as evaluated with the Hirschberg test. Intermittent strabismus was noticed by family members or caregivers in 10 (63%) of 16 patients. Patients older than 12 years did not show post-operative strabismus as evaluated by the Hirschberg test. Conclusion Hemispherotomy can cause or worsen post-operative strabismus in pediatric patients.

Objective To compare the angle of deviation measured from Photo-Hirschberg testing and Krimsky testing, with that from an alternate prism cover test (APCT) in strabismus patients. Methods A cross-sectional study was conducted in Songklanagarind Hospital, Thailand. Thirty-three strabismus patients were photographed for analysis by Photo-Hirschberg testing using computer software. The corneal light reflex displacement, converted into prism diopter (PD), was compared to the angle of deviation measured with APCT. Twenty-eight strabismus patients were tested with the Krimsky test. Data were analyzed using Pearson correlation and paired t-tests. The study excluded 4 intermittent exotropia cases, 1 intermittent esotropia case and 2 which cases missing data for krimsky test. Results The mean±SD of the deviation angle, measured by APCT with a fixation target at 30 cm and 6 m; were 48.09±16.34PD and 47.82±15.73 PD, respectively. At 1 m, the difference in the angle of deviation measured from APCT and the Photo-Hirschberg test within 10 PD were 58.8% and 63.6%, for ET and XT, respectively. The difference in the angle of deviation measured from APCT and Krimsky tests within 10 PD in ET and XT were 86.7% and 80.0%, respectively. At 4 m, the difference in angle of deviation measured from APCT and Photo-Hirschberg tests within 10 PD in ET and XT were 58.8% and 54.5%, respectively; whereas, the difference in the angle of deviation measured from APCT and Krimsky tests within 10 PD in ET and XT were 80.0% and 70.0%, respectively. Conclusion The reliability of Krimsky test was better than Photo-Hirschberg test for measuring an angle of deviation.

Significance This study highlights potential differences that can arise in gaze-position estimates from first Purkinje image-based eye trackers based on how individual Hirschberg ratios (HRs) are calculated. Purpose The purpose of this study was to evaluate the accuracy and repeatability of eccentric-viewing, prism-based, and theoretical techniques that are routinely used to calibrate HR in first Purkinje image-based eye trackers. Methods Hirschberg ratios of 28 participants (18 to 40 years old) were obtained using the PlusOptix PowerRef 3 photorefractor and eye tracker. In the gold standard eccentric-viewing technique, participants viewed eccentric targets (±12°, 4° steps) at 2 m. In the prism-based technique, 4 to 16Δ-D base-out and base-in prisms were placed in 4Δ-D steps before an eye occluded with an infrared filter; the fellow eye fixated a target at 1 m. Each participant's HR was calculated as the slope of the linear regression of the shift in Purkinje image relative to the pupil center for each target eccentricity or induced prism power. Theoretical HR was calculated from the participant's corneal curvature and anterior chamber depth measures. Data collection was repeated on another visit using all three techniques to assess repeatability. Data were also obtained from an Indian cohort (n = 30, 18 to 40 years old) using similar protocols. Results Hirschberg ratio ranged from 10.61 to 14.63°/mm (median, 11.90°/mm) in the eccentric-viewing technique. The prism-based and theoretical techniques demonstrated inaccuracies of 12 and 4% relative to the eccentric-viewing technique. The 95% limits of agreement of intrasubject variability were ±2.00, ±0.40, and ±0.30°/mm for the prism-based, eccentric-viewing, and theoretical techniques, respectively (P > .05). Intraclass correlation coefficients (95% confidence interval) were 0.99 (0.98 to 1.00) for eccentric, 0.99 (0.99 to 1.00) for theoretical, and 0.88 (0.74 to 0.94) for prism-based techniques. Similar results were found for the Indian cohort. Conclusions The prism-based and theoretical techniques both demonstrated relative inaccuracies in measures of HR compared with the eccentric-viewing technique. The prism-based technique exhibited the poorest repeatability.

Purpose To determine the prevalence of strabismus among Danish adults and to find the frequency of history of strabismus and strabismus surgery. Furthermore, to evaluate the prevalence of strabismus-associated amblyopia among participants with strabismus and to relate the results to the current national vision screening programme. Methods In total, 3785 adults in the Danish Rural Eye Study underwent an interview regarding eye health, visual acuity measurement, Hirschberg test and retinal photography. Participants were categorized into groups based on their birth date in relation to the introduction of the national vision screening programme. Results In total, the prevalence of strabismus was 1.1% (41/3785; 95% CI: 0.8-1.5); no differences were found in relation to gender or screening status. The prevalence of exotropia (XT) was 0.3% (12/3785; 95% CI: 0.2-0.6) and of esotropia (ET) 0.8% (29/3785; 95% CI: 0.5-1.1), resulting in an XT:ET ratio of 1:2.7. A history of strabismus was present in 4.6% (174/3785; 95% CI: 4.0-5.3), and a history of strabismus surgery was present in 0.8% (32/3785; 95% CI: 0.6-1.2) of the participants. Among participants with manifest strabismus, 24% had strabismus-associated amblyopia. Conclusion In this first European population-based study of strabismus prevalence in adults, the prevalence was similar to three out of five previous studies using cover test. The use of Hirschberg test may have led to an underestimation of the true prevalence. The prevalence was neither related to screening status nor gender. Our results are the first to display a predominance of ET among Caucasian Scandinavian adults.

Asphaltene onset pressure (AOP) is a key parameter to determine the flow assurance of live oils. In this study, the capabilities of the cubic-plus-association (CPA) equation of state (EoS) and the Hirschberg method of calculating the AOP of five oils are compared to a new approach using few experimental data. Two experimental data points of AOP and only one of the bubble pressure (BP) are required for adequate parametrization of both models. The number of non-zero binary interaction parameters needed for the CPA EoS is reduced to only four binary pairs. In the Hirschberg method, the BP calculations were performed with the Soave–Redlich–Kwong EoS. For all oils, the CPA EoS provided lower deviations for both AOP and BP. To achieve a good correlation, the Hirschberg method requires the use of AOP experimental data to calculate the difference between the liquid-phase solubility parameter and the asphaltene solubility parameter. Similarly, CPA EoS requires the calculation of the cross-associating energy parame...

Purpose: Photographic Hirschberg test applications are practical options for screening in areas where a specialist is not available. A semi-automated Hirschberg test-based application was developed...

Refractive errors(RE) is an optical defect that reduces the ordinary imaginative and prescient and is a prime contributor to visual impairment, especially among school youngsters, and most of the time it remains undiagnosed for lengthy intervals leading to visionary disabilities in children. Other condition is strabismus that is when eyes do not pair as depicting misalignment, it seems as if the two eyes are not fixating on the identical region on the equal time. Objectives: To determine the pattern of refractive errors & strabismus in children. Methods: 1889 patients were observed, children of age ranging from 1 month to 14 years in Ophthalmology department of Arif Memorial Teaching Hospital, Lahore between the year 2018 to 2019. A self-structure Performa was utilized to gather information. Ocular misalignment was evaluated by cover test and the Hirschberg light reflex. The data was analyzed by SPSS 24.0 (SPSS Inc, Chicago,USA). Results: Total 1889 children examined, 18.7% were less than 1 year, 54.7% were between 1 to 4 years, and 26.6%were 4 to 14 years. In those children prevalence of Refractive error was 37.6% in which 18.8% had hypermetropia, 11.2% had astigmatism and 7.6% had myopia. In the data of 1889 patients, 18.7% were less than 1 year in which 79 had strabismus out of which 11.6% are alternating exotropia, 5.4% are alternating exotropia, 4.0% are exotropia, and 1.4% were exotropia. While 54.68% patients were between 1 to 4 years, in which 29.7% had squint. 26.57% patients were between 4 to 14 years, 157 had strabismus. In those patients 13.9% were alternating exotropia, 8.2% were exotropia, 7.4% were alternating exotropia, and 1.8% were exotropia. Conclusions: Hypermetropia appears significantly general in the children of age that is less than 1 year. While in strabismus, alternating esotropia is more commonplace in our study, but it does not suggests any significance with age.

Background Strabismus is the leading risk factor for amblyopia, which should be early detected for minimized visual impairment. However, traditional school screening for strabismus can be challenged due to several factors, most notably training, mobility and cost. The purpose of our study is to evaluate the feasibility of using a smartphone application in school vision screening for detection of strabismus. Methods The beta smartphone application, EyeTurn, can measure ocular misalignment by computerized Hirschberg test. The application was used by a school nurse in a routine vision screening for 133 elementary school children. All app measurements were reviewed by an ophthalmologist to assess the rate of successful measurement and were flagged for in-person verification with prism alternating cover test (PACT) using a 2.4Δ threshold (root mean squared error of the app). A receiver operating characteristic (ROC) curve was used to determine the best sensitivity and specificity for an 8Δ threshold (recommended by AAPOS) with the PACT measurement as ground truth. Results The nurse obtained at least one successful app measurement for 93% of children (125/133). 40 were flagged for PACT, of which 6 were confirmed to have strabismus, including 4 exotropia (10△, 10△, 14△ and 18△), 1 constant esotropia (25△) and 1 accommodative esotropia (14△). Based on the ROC curve, the optimum threshold for the app to detect strabismus was determined to be 3.0△, with the best sensitivity (83.0%), specificity (76.5%). With this threshold the app would have missed one child with accommodative esotriopia, whereas conventional screening missed 3 cases of intermittent extropia. Conclusions Results support feasibility of use of the app by personnel without professional training in routine school screenings to improve detection of strabismus.

Purpose: To find out the Centrality of Hirschberg reflex in young emmetropic females and to correlate it with asthenopia. Study Design: Cross-sectional study Place and Duration of Study: Outpatients department of Khalid Eye Hospital, Karachi, from January to December 2019. Methods: Six hundred young emmetropic females 10 to 25 years of age were included. We performed the Hirschberg test and Jackson cross cylinder to assess the astigmatism and observed near point of convergence to find out convergence insufficiency. Results: Out of 600 young emmetropic females only one hundred and ninety had a central Hirschberg corneal reflex along with an astigmatism of 0.25 to 0.50 which was observed in one hundred and sixty five patients. One hundred and twenty five had a receded near point of convergence. Conclusion: Acentrality of Hirschberg can be a cause of asthenopia among young emmetropic females. Key Words: Asthenopia, Astigmatism, Emmetropia, Hirschberg corneal reflex.

A smartphone app has been developed to perform the automated photographic Hirschberg test for objective measurement of ocular misalignment. By computing the difference in corneal reflection generated by the phone camera flash relative to the iris center based on high resolution images, the app can measure misalignment with a much higher precision than the naked eye performing the Hirschberg test. It has been validated in a previous clinical evaluation study by comparing to the clinical gold standard-prism and alternate cover test. The goal of this article is to describe the testing techniques regarding how to use the app to measure ocular alignment for different fixation distances, without or with cover to break fusion, as well as angle kappa, so that users can use the app to perform equivalent tests typically done in clinic using prisms.

Purpose. This paper presents the results of objective accommodation measurements taken from patients with concomitant strabismus. Materials and methods. The experiment was performed on 32 patients (64 eyes) ranging from 5-26 years of age (in average 13.5 ± 1.43 years old): 26 patients with esotropia (52 eyes), 2 patients with exotropia (4 eyes), and 4 patients with secondary strabismus (8 eyes). 8 of the patients (10 eyes) identified amblyopia of various degrees. 51 of the eyes exhibited hyperopia from 0.5 to 9.5 D according to spherical equivalent refraction, and 16 eyes exhibited myopia from 0.25 to 10 D. The control group consisted of 30 children with hyperopia (16 eyes), emmetropia (10 eyes), and myopia of various degrees (34 eyes) without strabismus. To determine specific indicators of objective accommodation - Binocular (BAR) and Monocular Accommodative Response (MAR), the options of consensual accommodation, as well as the resting state of accommodation (RSA) in concomitant strabismus - the open field autorefkeratometer Grand Seiko WR - 5100K was used. The degree of deviation was determined using the Hirschberg test and a handheld ophthalmoscope. Results. The MAR ranged between normal and drastically lower values averaging at -1.85 ± 0.1 D. The BAR averaged at 2.23 ± 0.1 D and was greater than the MAR in half of the measured cases (61.3 %). The interocular difference in the BAR reached 2.95 D, averaging at 0.87±0.14 D. The interocular difference in MAR reached 0.85 D, averaging at 0.34 ± 0.07 D. In the control group, BAR values were lower than MAR; the interocular differences consisted of 0.13 ± 0.01 and 0.08 ± 0.01 D, respectively. Highly amblyopic eyes had equal and drastically decreased BAR and MAR (average of -0.16 ± 0.07 D); in the fellow eyes, BAR and MAR were higher -1.08 ± 0.14 and -1.0 ± 0.14 D, respectively. In esotropic eyes, RSA was higher in the misaligned eye, and in exotropic eyes, RSA was lower in the misaligned eye. The straight and concomitant responses were decreased: until -1.43 ± 0.1 and -1.32 ± 0.15 D respectively. In the control group, the straight and concomitant accommodative response was similar (average of -1.77 ± 0.17 D in both cases). Conclusion. The results showed the characteristic changes in accommodative parameters as a result of heterotropia, not typical for orthotropic patients with various types of refraction // Russian Ophthalmological Journal, 2017; 1: 49-54. doi: 10.21516/2072-0076-2017-10-1-49-54.

Strabismus is an ophthalmological disease characterized by an imbalance in the ocular muscles, characterized by the deviation of the binocular alignment, in which the eyes can turn inwards, outwards, upwards or downwards. Its incidence can occur from the first months of life to adulthood. Thus, late detection may cause double vision or loss of vision, hence the importance of early detection of strabismus for its prognosis and effective treatment. In this work, we propose a fully automatic method to detect strabismus by evaluating the distance between the limb centroid and the point in between the eye corners. The proposed method achieved an accuracy of 96.6% with a sensitivity of 95.8% and a specificity of 100%.

The study is centered around creating a system that uses digital image processing via OpenCV-Python and the central corneal light reflex (CCLR) test, or Hirschberg test, as the basis for HOCORC. This is an algorithm that would determine whether patients have strabismus and what type of strabismus found, whether esotropia or exotropia. CCLR processing of HOCORC resulted in an accuracy of 97.5% and an error rate of 2.5% for the detection of strabismus of patients. HOCORC produced an accuracy of 97.5% and an error rate of 2.5% for strabismus classification. These results indicate that the system using the proposed HOCORC algorithm is a viable means of detecting and classifying strabismus.

Background Young children’s vision screening, as part of a preventative health care service, produces great value for developing regions. Besides yielding a high return on investment from forestalling surgeries using a low-cost intervention at a young age, it improves school performance and thus boosts future labor force quality. Leveraging low-skilled health care workers with smartphones and automated diagnosis to offer such programs can be a scalable model in resource-limited areas. Objective This study aimed to develop and evaluate an effective, efficient, and comprehensive vision screening solution for school children in resource-limited areas. First, such an exam would need to cover the major risk factors of amblyopia and myopia, 2 major sources of vision impairment effectively preventable at a young age. Second, the solution must be integrated with digital patient record-keeping for long-term monitoring and popular statistical analysis. Last, it should utilize low-skilled technicians and only low-cost tools that are available in a typical school in developing regions, without compromising quality or efficiency. Methods A workflow for the screening program was designed and a smartphone app was developed to implement it. In the standardized screening procedure, a young child went through the smartphone-based photoscreening in a dark room. The child held a smartphone in front of their forehead, displaying pre-entered personal information as a quick response code that duplexed as a reference of scale. In one 10-second procedure, the child’s personal information and interpupillary distance, relative visual axis alignment, and refractive error ranges were measured and analyzed automatically using image processing and artificial intelligence algorithms. The child’s risk for strabismus, myopia, and anisometropia was then derived and consultation given. Results A preliminary evaluation of the solution was conducted alongside yearly physical exams in Luoyang, Henan, People’s Republic of China. It covered 20 students with suspected strabismus and 80 randomly selected students, aged evenly between 8 and 10. Each examinee took about 1 minute, and a streamlined workflow allowed 3 exams to run in parallel. The 1-shot and 2-shot measurement success rates were 87% and 100%, respectively. The sensitivity and specificity of strabismus detection were 0.80 and 0.98, respectively. The sensitivity and specificity of myopia detection were 0.83 and 1.00, respectively. The sensitivity and specificity of anisometropia detection were 0.80 and 1.00, respectively. Conclusions The proposed vision screening program is effective, efficient, and scalable. Compared with previously published studies on utilizing a smartphone for an automated Hirschberg test and photorefraction screening, this comprehensive solution is optimized for practicality and robustness, and is thus better ready-to-deploy. Our evaluation validated the achievement of the program’s design specifications.

Purpose To investigate the longitudinal change in horizontal and vertical ocular alignment in normal and prism-reared infant monkeys during the critical developmental period. Methods Ocular alignment was measured using Hirschberg photographic methods in 6 infant monkeys reared under prism-viewing from day 1 after birth to 4 months, and 2 monkeys reared with normal visual experience. Photographs were acquired twice a week for the first 6 months of life and analyzed to identify pupil center and the first Purkinje image from which eye positions and strabismus angle were calculated. Results At 3 weeks after birth, prism monkeys presented with significant horizontal ocular misalignment. A gradual change in alignment was seen in all prism-reared monkeys stabilizing at approximately 11 weeks, at which time 5 monkeys were exotropic (mean, 16° XT; range, 13°-24°) and 1 monkey was esotropic (5° ET). A reduction in ocular misalignment was observed after exposure to normal visual environment at 16 weeks, but at 34 weeks of age, that is, 18 weeks after removal of prisms, prism-reared monkeys displayed a mean horizontal strabismus of 7° XT (range, 2° ET to 20° XT), which was still significantly different from normal monkeys. Conclusions Prism-rearing disrupts binocular fusion mechanisms, and horizontal and vertical strabismus is seen to develop as early as 3 weeks of age in monkey models, equivalent to approximately 3 months in humans. The time course of change in alignment overlaps with disruption in various visual sensory functions, suggesting a causal temporal link between sensory and motor mechanisms for alignment.

Approaches to the meaning of intonational meaning differ in associatingeach subcomponent with a meaning that remains invariant across contours (e.g.Pierrehumbert & Hirschberg 1990) or treating a contour as contributing its meaningholistically (e.g. Goodhue et al. 2015). This paper argues for a common core ofthe L*+H pitch accent across two intonation contours, the Rise-Fall-Rise (RFR,e.g. Ward & Hirschberg 1985), and a novel contour coined the Downscale-Contour(DSC). Both contours are analyzed as indicating the presence of an alternative withrespect to a scale derived from the QUD, but differ in the relative strength of thisalternative, with the DSC indicating a weaker and the RFR a stronger one.

Purpose We evaluate a smartphone application (app) performing an automated photographic Hirschberg test for measurement of eye deviations. Methods Three evaluation studies were conducted to measure eye deviations in the horizontal direction. First, gaze angles were measured with respect to the ground truth in nonstrabismic subjects (n = 25) as they fixated monocularly on targets of known eccentricity covering an angular range of approximately ±13°. Second, phoria measurements with the app at near fixation (distance = 40 cm) were compared with the modified Thorington (MT) test in normally-sighted subjects (n = 14). Third, eye deviations using the app were compared to a cover test with prism neutralization (CTPN; n = 66) and Synoptophore (n = 34) in strabismic subjects. Regression analyses were used to compare the app and clinical measurements of the magnitude and direction of eye deviations (prism diopters, Δ). Results The gaze angles measured by the app closely followed the ground truth (slope = 1.007, R2 = 0.97, P < 0.001), with a root mean squared error (RMSE) of 2.4Δ. Phoria measurements with the app were consistent with MT (slope = 0.94, R2 = 0.97, P < 0.001, RMSE = 1.7Δ). Overall, the strabismus measurements with the app were higher than with Synoptophore (slope = 1.15, R2 = 0.91, P < 0.001), but consistent with CTPN (slope = 0.95, R2 = 0.95, P < 0.001). After correction of CTPN values for near fixation, the consistency of the app measurements with CTPN was improved further (slope = 1.01). Conclusions The app measurements of manifest and latent eye deviations were consistent with the comparator clinical methods. Translational Relevance A smartphone app for measurement of eye alignment can be a convenient clinical tool and has potential to be beneficial in telemedicine.

Decreased vision, double vision, eye fatigue and strain associated with strabismus often require no-surgical or surgical options which may lead to overcorrection or under correction with a need for a follow up surgery. Therefore, quantitative assessment of the degree of strabismus can serve as very useful tool for deciding on therapeutic options and evaluation of their outcomes. Further, US focused statistics indicate that 4% of the population has strabismus while some global estimates attribute this anomaly only to 0.034% of world population. These contrasting statistics further lead to a necessity of having a uniform quantitative tool for a broader application to determine the scope and the degree of this anomaly in different populations. At this point variety of tests are used including Hirschberg test, Cover test, and Central Corneal Light Reflex Ratio. Therefore, the developed technique allows automatic quantitative detection of a presence of possible strabismus and calculation of linear and vertical deviations of eyes in digital images. In particular, the proposed algorithm was structured in seven stages: (1) face matching (2) face detection and alignment (3) extraction of region of interest (4) locating the iris of both eyes and their center positions (5) selection of reference points in the eyes (6) calculation of linear and vertical deviations (7) making prediction using pre-trained regression model. This methodology has 93% of accuracy, 84% of sensitivity and 30% of specificity as tested on 128 images. In particular, the outcome encompasses a methodology for two graphical user interfaces which have real time as well as local image processing capability; a bounding box approach to make the face of a person aligned; and determination of numerical linear and vertical deviations of the eyes in millimeters. While the deviation of normal eyes is close to zero, the higher numbers indicate pre-strabismus or strabismus conditions respectively.

In preparation of the 600th anniversary of Rostock University the question arose who the first female students at the institute of chemistry were. With the help of digitized materials of the enrollments and printed lists of graduations in the beginning of the 20th century, the first female graduate, Else Hirschberg, was found. This article examines her life, her scientific career and her fate. After a short introduction about women’s studies in Germany, particular attention will be paid to the ancestry of Else Hirschberg´s Jewish family in the first part. Based on documents provided by several archives and the possibilities of ancestry.com in connection with online-access detailed information about Else, her family and her ancestors will be described – both her maternal and the paternal lineage. The second part of the paper informs about Else Hirschberg´s academic career. It is not possible to name the exact reasons for her decision to study chemistry, but an impressive picture of her scientific efforts will be drawn. Furthermore, a list of her papers and some information about the network that she used in her attempts to emigrate from Germany are available.

A 38-year-old male reported suffering from left hemiparesis starting 3 months ago. He felt weakness of his left lower extremity and numbness of the left elbow and hand. He was admitted to a local hospital and told he had a stroke. At the time, the patient also noticed blurry vision in his right eye. A CT scan of the brain revealed right pontine hemorrhage (Fig. 38.1). His corrected visual acuity was 6/12 in the right eye and 6/10 in the left eye. A Hirschberg test showed 10° of esotropia in the right eye and 10° of exotropia in the left eye. Krimsky test revealed 18 prism diopters of esotropia in the right and 20 prism diopters of exotropia in the left. Extraocular movements showed severe limitation of right gaze in both eyes (Fig. 38.2, Video 38.1). Anterior segments and fundoscopic examinations were normal in both eyes. Visual fields were full in both eyes. Brain MR imaging 3 months later showed tiny hemosiderin over the posterior pons with no other vascular lesions noted (Fig. 38.3). The patient was followed for 1 year. Visual acuity improved to 6/8.6 in the right and 6/6.7 in the left. He was orthophoric on primary gaze. However, limitation of the right gaze persisted.

A 12-year-old boy presented with complaints of sudden-onset diplopia noted in the morning starting 3 days ago. One month ago, he had an episode of dizziness, chest tightness, and a common cold which resolved spontaneously. He denied any past medical history of head injury or epistaxis. Visual acuity was 6/6 in both eyes. A Hirschberg test showed a 5° esotropia on primary gaze. A prism cover test revealed 25 prism diopters of esotropia on primary gaze, which decreased to 18 on right gaze and increased to 40 on left gaze. Extraocular movements showed mild limitation of abduction in right gaze (−1 OD) and moderate limitation in left gaze (−2 OS) (Fig. 36.1). Anterior segments, pupillary reflexes, and fundoscopic examinations were normal. He received a brain CT scan which was also normal. One week later, he developed bilateral ptosis and total ophthalmoplegia (Fig. 36.2). A neostigmine test by intramuscular injection was performed in-office. However, no improvement in lid position or extraocular movement was observed. Thus, he was admitted for further investigation.

A 47-year-old female presented with complaints of eye pain OU. She was bedridden and very weak and had a significant history of breast cancer with brain metastasis. Ophthalmic consultation showed that there was lagophthalmos in both eyes. Her visual acuity was unable to be assessed due to her poor general condition. There were mild cataracts in both lenses. Her eyeballs were soft by digital examination. A Hirschberg test showed a mild degree of esotropia. Extraocular movements showed ocular bobbing on primary gaze, with severe limitation of horizontal gaze (Fig. 39.1, Video 39.1). MR imaging revealed multiple lesions in the bilateral cerebral hemispheres and cerebellar hemispheres, with an enhancing metastatic lesion over the dorsal pontine region (Fig. 39.2). She received whole brain radiotherapy and chemotherapy and was then discharged with stable conditions. She was lost to follow-up 4 months later.

This paper introduces an integrated way of detecting common visual impairments namely: Strabismus, Blind Spots and Blurry Vision. According to the Chairman of National Committee on Site Preservation, 70% of ophthalmologists are found in urban areas while the remaining 30% is scattered to rural areas. Thus, a low cost and portable product that can efficiently and effectively detect the said impairments is necessary. In addition to this, the device need not be operated by a medical practitioner. A Raspberry Pi with a monitor and camera would be used to implement Hirschberg Test for Strabismus, Visual Field Test for Blind Spot and Visual Acuity Tests for Blurry Vision. Hirschberg Test is implemented by taking the Central Corneal Light Reflex Ratio (CCLRR) of the patient through a picture taken from them. Visual Field test is done by presenting stimuli at different area of the visual field and recording the patient's response through a button press. The Visual Acuity test is done by using a Landolt C optotype and recording the patient's response through an 8 button keypad. The results from the Hirschberg Test were computed to have an accuracy of 90% by using z-test. For the Visual Field test and Visual Acuity test, the Mann Whitney Test proved that the data gathered from the patients had no significant difference with that from the medical records of patients.

More than 5% of Thai people have strabismus. Strabismus is known as cross-eyed or wall-eyed because the visual field angle of two eyes is not parallel. The amblyopia disease is the cause of strabismus in kids. Strabismus can be completely cured if the strabismus screening can be made in early stage. Currently, strabismus screening includes methods such as Hirschberg test, cover test and Krimsky test, and etc. The strabismus screening in kids is difficult and takes a lot time in special room. This research intend to develop a computer system to assist strabismus screening using the combination of computer games and eye tracking devices so that the screening results will be more accurate and exact. This screening technique requires shorter time and it is easy to use, so it is better in terms of efficiency and reducing time for strabismus screening.

This paper tackles the problem of interaction between multiple discourse particles in the same utterance. It examines how presuppositions and/or implicatures contributed by individual particles are combined to account for connotations which arise in utterances containing multiple particles. The subject of study is free combinations of set-evoking colloquial Russian particles –to, že, and ved’. The data are drawn from constructed minimal discourses. The study integrates the theories of information structure (Vallduvi, The informational component, 1992), scalar implicatures (Hirschberg, A theory of scalar implicature, 1985/1991), and discourse organization (Buring, On D-trees, beans, and B-accents, 2000). The current approach to decomposing the meaning of particles by examining them in combination sheds new light on the context-independent interpretations of the particles and makes another step toward understanding their complex roles in discourse.

Hirschberg [J. Acoust. Soc. Am. 134, 9-12 (2013)] presents a commentary and criticisms of the viscous flow model presented by Erath et al. [J. Acoust. Soc. Am. 130, 389-403 (2011)] that solves for the asymmetric pressure loading on the vocal fold walls. This pressure loading arises from asymmetric flow attachment to one vocal fold wall when the glottal channel forms a divergent configuration. Hirschberg proposes an alternative model for the asymmetric loading based upon inviscid flow curvature at the glottal inlet. In this manuscript further evidence is provided in support of the model of Erath et al. and the underlying assumptions, and demonstrates that the primary criticisms presented by Hirschberg are unwarranted. The model presented by Hirschberg is compared with the model from the original paper by Erath et al., and it is shown that each model describes different and complementary aspects of divergent glottal flows.

Purpose The aim of this study is to evaluate the effect of general anesthesia with muscle relaxant on the horizontal ocular deviation in orthophoric children. Methods Children aged 4–16 years requiring a non-ophthalmological surgical procedure under general anesthesia with neuromuscular blockade were included. Prior ophthalmological examination excluded any oculomotor disorder. Horizontal ocular deviation was measured by the Hirschberg photographic method by comparing pictures taken in the awakened state to those taken under general anesthesia. Monitoring of anesthesia was performed by the Bispectral index (BIS) and muscle relaxation by the train of four (TOF). Results 33 Patients were included. Mean age was 8(±4) years and 67.7% were male. The mean horizontal ocular deviation after general anesthesia with neuromuscular blockade was −0.2 diopters (SD 9.7). Median was −0.7 diopters. 72.7% of patients had an ocular deviation of less than 7.5 diopters with a normal distribution. Conclusions Our results show that contrary to popular belief, eye position under general anesthesia in children without strabismus is not divergent but very close to orthophoria.

To compare the amount of esotropia corrected by surgery under general anesthesia and in a conscious state in esotropia surgery.The charts of 42 patients who underwent surgery under general anesthesia for correction of esotropia were reviewed. Angle of deviation was measured by the alternate prism cover test in awakened state one day before and after surgery. Under general anesthesia, angle of deviation was measured by Hirschberg or Krimsky test in 5 prism diopters (PD) scale 30 minutes after induction and at the end of the surgery. The amount of the angle of esodeviation corrected by surgery measured in awakened state (A-correction) and under general anesthesia (G-correction) was compared and analyzed to identify significant differences.The median age was 4.0 years and the median preoperative esodeviation angle was 30.0 PD. The median amount of G-correction of 30.0 PD was significantly different compared with that of A-correction at postoperative day one (p=0.003). However, differences between A-correction and G-correction were not evident at postoperative one week, one month, and final follow-up examination (p= 0.191, 0.215, and 0.396, respectively).Esotropia in A-correction was comparable to that in G-correction only at postoperative day one. These results suggest that it is desirable to perform esotropia surgery according to the initial surgical plan of awakened state regardless of the divergence of eye position. When in doubt, it could be useful to confirm whether the actual amount of surgical correction under general anesthesia is consistent with the plan and modifying the surgical dose nomogram.

Introduction: Angle kappa is important in our clinical practice as it can give the appearance of strabismus. A vertical angle kappa is secondary to macula heterotropia as a result of retinal traction from scar tissue in the posterior pole. Case report: We present an interesting case of a 25 year-old Chinese female who presented with an abnormal vertical angle kappa due to macula ectopia from a toxocara retinochoroidal granuloma. She had an apparent right exotropia and hypotropia on Hirschberg and Krimsky but a hypertropia on alternate prism cover test. Our patient was keen for surgical correction as she was bothered by the appearance of her large angle squint. The main concern about strabismus surgery in patients with angle kappa was that it could break down the patient’s fusion and cause diplopia. Conclusion: The management of vertical angle kappa is difficult and odifficult to treat surgically. We describe this rare case of a patient who underwent surgical correction of only the horizontal recti and she achieved apparent orthophoria with a good cosmetic outcome. Patient also had no diplopia post-operatively.

To evaluate the prevalence of neurological involvement and malformative/systemic syndromes in A- and V-patterns with respect to other kinds of infantile concomitant strabismus.A retrospective comparative study of 14,006 consecutive patients examined in the Pediatric Ophthalmology and Strabismus Unit at the Catholic University of Rome between January 2002 and February 2010 was carried out. A total of 2.72% (385) of patients presented with concomitant constant infantile strabismus associated with A- and V- patterns (study group; mean age 8 years; range: 8 months - 37 years; male 211, female 174). Another 377 consecutive patients affected by infantile concomitant strabismus without A- or V- patterns were used as controls (control group; mean age 9 years, range: 1-34 years; male 194, female 183). All patients underwent a complete ophthalmologic and orthoptic examination with ocular motility evaluation and prism cover test or the Hirschberg test in primary, up and down gaze positions, as well as cycloplegic retinoscopy. The angle of deviation was evaluated at near (33 cm) and distance fixation (6 m) with full correction of refraction.Neurological involvement and malformative/systemic syndromes were observed in 30.4% of the study group and in 19.8% of patients in the control group (P0.001). Patients with A-pattern showed a greater prevalence of neurological impairment, hydrocephalus and meningomyelocele, while those affected by V-pattern exhibited a greater prevalence of craniosynostosis and malformative syndromes.Neurological involvement and malformative/systemic syndromes seem to be more evident in patients presenting with A- and V-pattern strabismus.

To evaluate the accuracy and applicability of Plusoptix photoscreener in screening pre-verbal children at risk of amblyopia.In this cross-sectional population-based study 996 children aged 6-36 months were screened with the Plusoptix. The children underwent complete examinations that included a manual cycloplegic retinoscopy, slit lamp examination, cover test, the Hirschberg test and an assessment of fixation pattern. In addition, the prevalence of amblyogenic risk factors was estimated, the Plusopix measurements were compared with cycloplegic retinoscopy, and the referral criteria were modified to improve the accuracy of the device.Amblyogenic hyperopia+3.50 D, myopia-3.00 D, astigmatism1.50 D in the orthogonal meridian or1.00 D in the oblique meridian, or anisometropia1.50 D was detected in 4.7%, 0.0%, 12.3% and 0.5% of the samples, respectively. The average difference between retinoscopy and photorefraction for spherical equivalence was -0.16 ± 1.0 D (p0.05). Testability was 98.1% for the Plusoptix. The Plusoptix vision screener referred 47.8% of these children for sensitivity, specificity, positive predictive value and false-negative rates of 100%, 38.7%, 19% and 100%, respectively. These same measurements with the modified referral criteria (hyperopia ≥ 2.00 D in children under 12 months and astigmatism ≥ 1.25 D) were 93.6%, 51.2%, 21.7% and 98.2%.The Plusoptix is a useful objective screening instrument, but still has low specificity for detecting amblyopia risk factors in the paediatric population.

Hirschberg test にかかわる原著および関連する文献を解読して、この常用検査法の歴史的評価を振り返り現代的課題を検討した．Hirschberg は1885年と1886年にあわせて3篇の原著論文を Centralblatt fur Augenheilkunde に発表した．角膜反射像の位置を指標として、瞳孔縁と角膜輪部とをランドマークとして相互の位置関係から眼位のずれを計量する、視診による他覚的斜視角の測定法を提案した．斜視角の測定精度は10°ほどのおおまかなもので、その程度から斜視を5段階に分類することに成功した．この検査法は、簡易性、応用性、信頼性、再現性などに優れ、現在まで 120 年の長きにわたって日常診療に活用されてきた．原著ではほとんど検討されていない計数値にいわゆる Hirschberg ratio がある．その数値として1960年代まで7°/mmあるいは8°/mmが踏襲されてきたが、1970年頃から再検討が試みられた．カッパ角はもとよりのこと角膜反射像の光学的特性の認識に加えて、角膜前面の曲率半径、入射瞳、前房深度などの変数を適切に考慮した理論計算および画像分析によって、12°/mmを代表とする換算値に修正されて現在に至っている．

This study was designed to establish the specific communicative function of both low (L*) and high (H*) pitch accent onsets with high rising tunes (HRTs), earlier established as a feature of Australian English. The data consisted of the dialogues of four female and four male adolescent speakers who were recorded while participating in the Map task. The discourse analysis involved the application of Pierrehumbert & Hirschberg's compositional theory of tune meaning. The study appears to support key aspects of Pierrehumbert & Hirschberg's theory: the results show overwhelmingly that the speakers used high (H*) pitch accents with new information and low (L*) pitch accents with information that was already part of the speaker and hearer's mutual beliefs. The findings suggest that the individual tones in a HRT each contribute to the overall meaning of an intonation contour, and that a close examination of intonation features within a developing communication context is crucial to understanding intonational meaning.

Purpose To investigate omission of population-based eye screening at age 6–9 months in the Netherlands. Methods Prospective population-based consecutive birth cohort study was used. In two consecutive birth cohorts, children were eye screened at 1–2 and 3–4 months, but at general-health screening at 6–9 months, the second cohort was not eye screened, unless anything conspicuous was noted or in case of positive family history. Data were collected from screening records and anonymous questionnaires. Semi-structured daylong observations were made of physicians examining children aged 0–4 years, including children from the cohorts, by two orthoptic students. Results 58 of 6059 children (0.96%), in the screened, and 48 of 5482 children (0.88%) in the unscreened group were referred to orthoptist or ophthalmologist, mostly for observed strabismus. Amblyopia, all combined with strabismus, was diagnosed in ten screened (0.17%) versus six unscreened children (0.11%). Most physicians found preverbal examinations and decisions to refer difficult. The observations by orthoptic students revealed that cover test, pupillary reflexes, pursuit movements and eye motility were frequently performed inadequately, contrary to the Hirschberg test, at this age. Conclusion The screened and unscreened group differed little regarding the number of children referred and found to have amblyopia. Referral was mostly based on observed strabismus.

PURPOSE To determine the distribution of refractive errors and clinical characteristics of strabismus in patients with Down syndrome. PATIENTS AND METHODS Patients with Down syndrome attending the Izmir Association for Supporting Patients With Down Syndrome in Izmir, Turkey, were screened for strabismus and refractive errors. All patients underwent a complete eye examination including cycloplegic refraction and dilated fundus examination. Ocular alignment was evaluated using the cover test and either the Krimsky or the Hirschberg corneal reflex test depending on the cooperation of the patient. Strabismic and nonstrabismic patients were compared for refractive errors, anisometropia, and amblyopia. RESULTS Fifty-seven patients with an average (± standard deviation) age of 9.30 years (± 6.14 years; range, 1 to 31 years) were screened. Twentyfive (44%) were female and 32 (56%) were male. Eleven patients (19%) had strabismus. Ten (18%) had esotropia and 1 (2%) had exotropia. Infantile esotropia was observed in 3 patients who had no significant refractive errors. Seven patients had acquired esotropia; they had clinically significant refractive errors and anisometropia. A higher frequency of hypermetropia was noted in patients with strabismus (P < .05). CONCLUSIONS Esotropia and hypermetropia are common in patients with Down syndrome. Early diagnosis and treatment of strabismus and associated ocular conditions such as refractive errors and amblyopia may improve the quality of life for these patients. J Pediatr Ophthalmol Strabismus 2006;43:27-30. AUTHORS The authors are from the Izmir Ataturk Education and Research Hospital, Department of Ophthalmology, Izmir, Turkey. Originally submitted July 17, 2004. Accepted for publication December 7, 2004. Address reprint requests to Nazife Sefi Yurdakul, MD, Cetas 2 sitesi, A blok 12, Narlidere-Izmir, Turkey.

The Gale-Shapley algorithm for the Stable Marriage Problem is known to take $\Theta(n^2)$ steps to find a stable marriage in the worst case, but only $\Theta(n \log n)$ steps in the average case (with $n$ women and $n$ men). In 1976, Knuth asked whether the worst-case running time can be improved in a model of computation that does not require sequential access to the whole input. A partial negative answer was given by Ng and Hirschberg, who showed that $\Theta(n^2)$ queries are required in a model that allows certain natural random-access queries to the participants' preferences. A significantly more general - albeit slightly weaker - lower bound follows from Segal's general analysis of communication complexity, namely that $\Omega(n^2)$ Boolean queries are required in order to find a stable marriage, regardless of the set of allowed Boolean queries. Using a reduction to the communication complexity of the disjointness problem, we give a far simpler, yet significantly more powerful argument showing that $\Omega(n^2)$ Boolean queries of any type are indeed required for finding a stable - or even an approximately stable - marriage. Notably, unlike Segal's lower bound, our lower bound generalizes also to (A) randomized algorithms, (B) allowing arbitrary separate preprocessing of the women's preferences profile and of the men's preferences profile, (C) several variants of the basic problem, such as whether a given pair is married in every/some stable marriage, and (D) determining whether a proposed marriage is stable or far from stable. In order to analyze "approximately stable" marriages, we introduce the notion of "distance to stability" and provide an efficient algorithm for its computation.

Recent work in intonational phonology has shown that L and H points are carefully controlled by the speaker, i.e., they are scaled and synchronized with the segmental material in extremely consistent ways (Arvaniti, 2003; Arvaniti, Ladd, & Mennen, 1988, 2000; Ladd, 2003; Liberman and Pierrehumbert, 1984; Prieto, van Santen, & Hirschberg, 1995; Xu, 1999, 2000, among others). Similarly, it has been shown that pitch pressure environments (namely, proximity to a boundary tone or to an upcoming pitch accent) can drastically affect surface H alignment patterns (Silverman & Pierrehumbert, 1990; Prieto, Shih, & Nibert, 1995). What is less well known are the effects of time and pitch pressure environments on surface scaling and L alignment patterns and whether stability effects are found in these domains. This paper discusses the effects of tonal clash (or strict adjacency between two accents) on the phonetic realization of rising prenuclear accents in Catalan. The analysis of the data shows that the adjacency of two rising accents triggers a drastic temporal reorganization of the f0 gestures involved, resulting in anticipation of the first gesture and delay of the first L of the second. The data thus reveals that f0 gestures are roughly timed to accented syllables, keeping a more or less floating relationship with the segmental string. Importantly, no significant differences are found on H scaling in clash vs. nonclash environments, revealing that these points work as real production targets. Moreover, in tonal clash contexts the time of the second tonal rise significantly shortens and the velocity of the rising gesture significantly increases in order to reach a given scaling target. Therefore, the results of the present study reveal that, in pitch pressure environments, a clear contrast is found between the stability effects of the H scaling domain and the adapting behavior of the time and velocity domains.

Purpose Analysation of the surgical treatment results of concomitant strabismus in patients based on volume of operation preliminary modeling using three-dimensional biomechanical eye model (TBEM "SEE-KID") Methods We examined the angel of strabismus by Hirschberg, with Frenel's prisms on table Maddox,binocular vision. There were analysed surgical treatment results of concomitant strabismus in 106 patients, wich were opereted after investigation preliminary modeling using three-dimensional biomechanical eye model (TBEM "SEE-KID"). Results Orthotropy was obtained in 54 from 106 patients (50,9%)at the first day after operation.52from 106 patients (49,1%) had residual angle of 5-10 hypocorrection was in 44 patients, and hypocorrection was in 8 patients. 18 patients were lost to follow-up. At 3-12 months folliw-ups ortothrop has been preserved in 53 from 88 patients (60,2%), and 35 from 88patients residual angle of 5-10 remained - hypocorrection was in 31 patients, and hypocorrection was in 4 patients. Conclusion TBEM "SEE-KID" use in complex examination and results of surgical treatment in patients with strabismus allows prognosing surgical result in 60% of cases and accelerates diagnostic process. This method needs further investigation.Particularly extraocular muscles biomechanics needs precisely estimated (degree hyper or hypofunction, movement amlitude).

PURPOSE Gaze position is calibrated in first Purkinje image-based eye trackers using the population-average Hirschberg ratio (HR) that is prone to inaccuracies or using the individual's HR that is cumbersome to obtain empirically. This study investigated (1) the agreement between HR calculated theoretically from the individual's corneal curvature and anterior chamber (AC) depth and those obtained empirically and (2) the contribution of corneal curvature and AC depth in the intersubject variance of the two HRs. METHODS Twenty-four subjects (mean ± SD age, 23.6 ± 3.5 years) fixated monocularly on a light-emitting diode array spanning ±24 degrees of horizontal or vertical gaze angle, in 4-degree steps, at 95 cm viewing distance. Empirical HR was determined using a custom-designed infrared eye tracker as the magnitude of separation between Purkinje image position and entrance pupil center per unit change in angular eccentricity. Theoretical HR was calculated from the subject's corneal curvature and AC depth using the model of Brodie (1987). RESULTS Empirical and theoretical HRs for horizontal and vertical gaze directions were well correlated (r ≥ 0.83) and not significantly different from each other (p ≥ 0.23; mean difference [±95% limits of agreement], -0.35 [0.85 to -1.55] degrees/mm for horizontal HR and -0.16 [1.01 to -1.33] degrees/mm for vertical HR). Corneal curvature and AC depth together accounted for greater than or equal to 80% and greater than or equal to 91% of intersubject variance in empirical and theoretical HR, respectively (p < 0.001). Hirschberg ratios changed at -2.3 to -2.8 degrees/mm per millimeter change in corneal curvature and at 2.0 to 2.4 degrees/mm per millimeter change in AC depth. CONCLUSIONS Theoretical HR calculated from the individual's corneal curvature and AC depth can be used in lieu of the empirical HR for gaze position calibration to within approximately 2 degrees/mm of accuracy. Gaze position accuracy significantly improves by using the theoretical HR, relative to the population-average HR. Corneal curvature and AC depth combined explain the majority of intersubject variability in HR.

Fine needle aspiration biopsy (FNAB) of tumors has a long history. The first intraocular biopsy was performed by Hirschberg in 1868. Since the publication of a major report by Jakobiec in 1979, FNAB is increasingly used in the evaluation of ophthalmic tumors. The safety and reliability of ophthalmic FNAB have been reported by several other investigators with adequacy rates of 88–95 %.

For parallel machine architecture the Iterated Longest Fragment algorithm was investigated by Stauffer and Hirschberg [Proc. 8th Int. Parallel Process. Symp., 1994, pp. 344-348] for compressing a text with a static dictionary. Later Nagumo, Lu and Watson [Inform. Process. Lett. 59 (1996) 91-96] proved that the algorithm can be implemented in an on-line way for the classical architecture as well. Beside some experimental results the efficiency of the algorithm has not been analyzed yet. In this paper we will investigate the asymptotic worst-case behaviour of the ILF algorithm for several types of static dictionaries. 2001 Elsevier Science B.V. All rights reserved.