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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

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.

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.

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).

This study introduces an improved computing scheme for determining eye rotation from Purkinje images I and IV. The original computing scheme systematically underestimated eye rotation. Paraxial raytracing calculations revealed that this error resulted from failure to account for the fact that Purkinje images I and IV fall at different distances behind the cornea. The error could be overcome with a correction factor derived from paraxial raytracing calculations. A series of experiments were carried out to test the validity of this correction factor; involving exact raytracing calculations as well as measurements on physical model eyes and human eyes. The influence on the correction factor of ocular surface asphericity, accommodation, age and ocular component variations were examined. The new method was also compared to Hirschberg's technique, which makes use of Purkinje image I alone, as a means of screening for strabismus.

Purpose Due to inaccuracy of diagnostic tests, prevalence of orthotropy after the first strabismus surgery varies in the range of 40 to 90%, and frequency of repeated surgeries comprises 10–50%. The purpose of the study was to investigate the efficacy of using of 3D biomechanical eye model (TBEM) in diagnostics and treatment of patients with concomitant strabismus (CS). Methods 30 CS patients were examined and underwent standard strabometric tests (Hirschberg test, Krymskiy test, Maddox scale, synoptophore with fusion reserves). Hyperfunction and hypofunction of one muscle or another was measured by coordimetry according to Hess-Lancaster; modeling of eye positions was performed using SEE-KID 3D biomechanical model (RISC Software GmbH, Hagenberg, Austria). Standard surgeries were performed on the basis of their pre-surgical modeling in SEE-KID TBEM. Exclusion criteria: patients with high and moderate amblyopia were excluded from the study. Follow-up period comprised 1 – 3 months. Results Virtual pathological models created using SEE-KID TBEM for all examined patients conformed to their actual strabismologic status. Surgeries conducted on the basis of preliminary TBEM modeling have resulted in achievement of orthotropy in 20 patients (66.7%) and its preservation at last visit in follow-up period. Residual strabismus angle (5-8°) was detected in 10 patients, including hypocorrection (9 patients), and hypercorrection (1 patient). Conclusion The use of existing strabometric methods in complex with TBEM is a promising diagnostic algorithm for assessment of the state of concomitant strabismus patients, which requires further studies.

Purpose: Presentation of a paediatric eye screening program which is based on the educators’ performance Methods: 4400 children(n1=2200 3-3 ½ y.o., n2=2200 4-6 y.o.),10 ophthalmologists and 20 teachers participated in this study.Children were tested for visual acuity(Va),using the NK test and manifest horizontal strabismus,using the Hirschberg test.Criteria for further evaluation:n1: Va

Purpose To evaluate measurement errors that are introduced in video eye tracking when pupil centration changes with pupil size. Methods Software was developed under Visual C++ to track both pupil centre and corneal centre at 87 Hz sampling rate at baseline pupil sizes of 4.75 mm (800 lux room illuminance) and while pupil constrictions were elicited by a flashlight. Corneal centres were determined by a circle fit through the pixels detected at the corneal margin by an edge detection algorithm. Standard deviations for repeated measurements were ±0.04 mm for horizontal pupil centre position and ±0.04 mm for horizontal corneal centre positions and ±0.03 mm for vertical pupil centre position and ±0.05 mm for vertical corneal centre position. Ten subjects were tested (five female, five male, age 25–58 years). Results At 4 mm pupil sizes, the pupils were nasally decentred relative to the corneal centre by 0.18 ± 0.19 mm in the right eyes and −0.14 ± 0.22 mm in the left eyes. Vertical decentrations were 0.30 ± 0.30 mm and 0.27 ± 0.29 mm, respectively, always in a superior direction. At baseline pupil sizes (the natural pupil sizes at 800 lux) of 4.75 ± 0.52 mm, the decentrations became less (right and left eyes: horizontal 0.17 ± 0.20 mm and −0.12 ± 0.22 mm, and vertical 0.26 ± 0.28 mm and 0.20 ± 0.25 mm). While pupil decentration changed minimally in eight of the subjects, it shifted considerably in two others. Averaged over all subjects, the shift of the pupil centre position per millimetre pupil constriction was not significant (right and left eyes: −0.03 ± 0.07 mm and 0.03 ± 0.04 mm nasally per mm pupil size change, respectively, and −0.04 ± 0.06 mm and −0.05 ± 0.12 mm superiorly). Direction and magnitude of the changes in pupil centration could not be predicted from the initial decentration at baseline pupil sizes. Conclusions In line with data in the literature, the pupil centre was significantly decentred relative to the corneal centre in the nasal and superior direction. Pupil decentration changed significantly with pupil size by 0.05 mm on average for 1 mm of constriction. Assuming a Hirschberg ratio of 12° mm−1, a shift of 0.05 mm is equivalent to a measurement error in a Purkinje image-based eye tracker of 0.6°. However, the induced measurement error could also exceed 1.5° in some subjects for only a 1 mm change in pupil size.