Measurements (autokeratometry, A-scan ultrasonography and video ophthalmophakometry) of ocular surface radii, axial separations and alignment were made in the horizontal meridian of nine emmetropes (aged 20-38 years) with relaxed (cycloplegia) and active accommodation (mean +/- 95% confidence interval: 3.7 +/- 1.1 D). The anterior chamber depth (-1.5 +/- 0.3 D) and both crystalline lens surfaces (front 3.1 +/- 0.8 D; rear 2.1 +/- 0.6 D) contributed to dioptric vergence changes that accompany accommodation. Accommodation did not alter ocular surface alignment. Ocular misalignment in relaxed eyes is mainly because of eye rotation (5.7 +/- 1.6 degrees temporally) with small amounts of lens tilt (0.2 +/- 0.8 degrees temporally) and decentration (0.1 +/- 0.1 mm nasally) but these results must be viewed with caution as we did not account for corneal asymmetry. Comparison of calculated and empirically derived coefficients (upon which ocular surface alignment calculations depend) revealed that negligible inherent errors arose from neglect of ocular surface asphericity, lens gradient refractive index properties, surface astigmatism, effects of pupil size and centration, assumed eye rotation axis position and use of linear equations for analysing Purkinje image shifts.
ABSTRACT. Objective. To estimate the long-term cost-effectiveness of a hypothetical screening program for untreated amblyopia in 3-year-old children conducted by orthoptists in all German kindergartens in the year 2000.Methods. A cost-utility analysis was performed for which a decision tree was combined with a Markov model. Incremental costs and effects during the children's remaining lifetime were estimated. The model took into account the probability of treatment without screening, age-specific treatment success rates, costs of screening and treatment, as well as effects of unilateral and bilateral visual impairment caused by amblyopia and other eye diseases coming along later in life on quality of life (utility). Model parameter values were obtained from a field study of orthoptic screening in kindergarten, from the literature, and from expert interviews. Costs were estimated from a third-party payer perspective. Uncertainty was assessed by univariate and probabilistic sensitivity analysis (Monte Carlo simulation).Results. The incremental cost-effectiveness ratio (ICER) of orthoptic screening was 7397 Euro (€) per quality-adjusted life year (QALY) when costs and effects were discounted at 5%. In univariate sensitivity analysis, the ICER was sensitive to the uncertainty regarding the utility of unilateral visual impairment and to the discount rate for effects; besides uncertainty regarding the prevalence of untreated amblyopia, the odds ratio of success of treatment when started late, and the probability of treatment without screening had a noticeable but much smaller effect. Monte Carlo simulation yielded a 90% uncertainty interval for the ICER of 3452 €/QALY to 72 637 €/QALY; the probability of an ICER <25 000 €/QALY was 84%.Conclusions. The ICER of orthoptic screening seems to fall within a range that warrants careful consideration by decision-makers. Much of the uncertainty in results comes from the uncertainty regarding the effect of amblyopia on quality of life. To reduce this uncertainty, the impact of amblyopia on utility should be investigated. Pediatrics 2004;113:e95-e108. URL: http://www.pediatrics. org/cgi/content/full/113/2/e95; amblyopia, vision screening, children, preschool, cost-effectiveness, decision modeling, Markov process.
Ophthalmophakometric measurements of ocular surface radius of curvature and alignment were evaluated on physical model eyes encompassing a wide range of human ocular dimensions. The results indicated that defocus errors arising from imperfections in the ophthalmophakometer camera telecentricity and light source collimation were smaller than experimental errors. Reasonable estimates emerged for anterior lens surface radius of curvature (accuracy: 0.02-0.10 mm; precision 0.05-0.09 mm), posterior lens surface radius of curvature (accuracy: 0.10-0.55 mm; precision 0.06-0.20 mm), eye rotation (accuracy: 0.00-0.32 degrees; precision 0.06-0.25 degrees), lens tilt (accuracy: 0.00-0.33 degrees; precision 0.05-0.98 degrees) and lens decentration (accuracy: 0.00-0.07 mm; precision 0.00-0.07 mm).
Aim: To analyse the test characteristics of orthoptic screening for amblyopia or amblyogenic risk factors (target conditions) in kindergarten. Methods: 1180 three year old children were screened by orthoptists in 121 German kindergartens. Orthoptic screening consisted of cover tests, examination of eye motility and head posture, and monocular visual acuity testing with the Lea single optotype test. Children were re-examined in kindergarten by different orthoptists after 3-6 months using a more demanding pass threshold for visual acuity. All children with at least one positive orthoptic test result or an inconclusive re-examination were referred to an ophthalmologist for diagnosis. The gold standard was set positive if a target condition was diagnosed on ophthalmological examination. It was set negative if no target condition was found upon ophthalmological examination, or if a child who screened negative or inconclusive passed the orthoptic re-examination without any positive test result. Results: The gold standard was ascertained in 1114 children. 26 (2.3%) children had a "positive" gold standard. In 10.8% of the children the initial screening was "inconclusive," mostly due to lack of collaboration. Screening test sensitivity (based on conclusive results only) was 90.9% and specificity was 93.8%. Conclusions: Orthoptic vision screening of 3 year olds in kindergarten is sensitive and specific. However, owing to a substantial proportion of inconclusive screening results, rescreening of non-cooperative 3 year old children should be considered.
Aims-To assess non-cycloplegic screening for amblyopia with the hand held Nikon Retinomax autorefractor in 3 year old kindergarten children. Methods-427 three year old children were examined in kindergarten with the Retinomax without cycloplegia. A gold standard was established in all children by two orthoptic examinations in kindergarten. If there were missing, abnormal, or inconsistent findings, children were referred for ophthalmological examination. If, by the ophthalmological examination, a new case of amblyopia requiring treatment was diagnosed, the gold standard was set "positive." Results-In 404 children the gold standard was obtained. 10 children (2.5%) had a "positive" gold standard of unknown and untreated amblyopia. Screening sensitivity was 0.80, specificity 0.58, accuracy 0.58, and the likelihood ratio 1.89. Conclusion-Non-cycloplegic refractive screening with the Retinomax led to many false positive referrals due to instrument myopia and "inconclusive" results. Hence specificity, accuracy, and the likelihood ratio were too low to conduct screening eVectively. (Br J Ophthalmol 2001;85:1179-1182 The Nikon Retinomax autorefractor is a monocular refractor, using a fogging technique. In several studies, this autorefractor was found to be a reliable instrument compared with other autorefractors and retinoscopy.
During 30 years of a cycloplegia career with an average of 34 cycloplegias/week, one may expect 2-10 severe or very severe complications. In current practice, the patient risk of severe complications is very small. Health care professionals and parents should be informed about the frequent occurrence of harmless side effects in order to achieve a good compliance with cycloplegia.
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