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BACKGROUND: The purpose of the study was to investigate the computer aided screening method using Purkinje image I and IV reflection patterns for the detection of inapparent eye misalignment and to compare this to an orthoptic examination. MATERIALS AND METHODS: 590 subjects up to 72 months of age with inapparent eye misalignment were recruited from the orthoptic outpatient department and externally. The computer aided screening consisted of taking a series of still video pictures with Purkinje reflection patterns. These were evaluated in an examiner independent way to reach a recommendation whether the child needed an ophthalmological referral or not. As gold standard, an orthoptic examination was performed. For analysis, the data were split by age groups. The orthoptic results were tested for certainty and repeatability. RESULTS: The computer aided examination had the highest sensitivity of 0.82 in the age group up to 2.5 years of age, and a specificity of 0.90. With an estimated prevalence for microtropia of 0.01, the extrapolated positive predictive value was 0.08, and the negative predictive value was 0.998. In the age group up to 2.5 years of age, the percentage of orthoptic examinations without clear result (neither non-referral, nor strabismic) was 22.4%, and 6.1% in the screening examination. Among the cases which were examined repeatedly, some were classified as "strabismic" in the beginning, and as "non-referral" in the end in the orthoptic examinations. CONCLUSIONS: The examiner independent, computer aided screening method is a cost effective option for the screening for inapparent eye misalignment, especially in the age group up to 2.5 years of age. If an orthoptic examination was carried out for screening, one should expect a higher rate of false positives, which entails more costly ophthalmological checks. Future studies should assess the validity of the single ortoptic examination as the gold standard in this age group.
PURPOSE: The second Cambridge Infant Vision Screening Program examined whether screening for accommodative errors by using videorefraction without cycloplegia could effectively serve as a first stage of screening for refractive errors, measured by standard cycloplegic retinoscopy. The screening also included an orthoptic examination for detection of strabismus. METHODS: All infants born in the Cambridge (UK) Health District, over a 2-year period, were invited for screening. Of those 5142 (76%) with mean age 8.1 +/- 0.8 months (SD) attended and received noncycloplegic videorefraction and an orthoptic examination. All those with a focusing error or orthoptic problem, as well as a randomly selected sample of visually normal control subjects, were invited to follow-up a month later for cycloplegic retinoscopy, repeat noncycloplegic videorefraction and orthoptic examination. RESULTS: Of the 5142 screened, 514 had a focusing error or orthoptic problem (positives). Four hundred thirty-nine of these and 284 visually normal control subjects (negatives) attended follow-up. A refractive or orthoptic condition was confirmed in 59.0% of the positive cases, whereas infants in 96.8% of the negative cases were confirmed normal. Adjusting for the proportions of the population represented by those infants seen at follow-up, sensitivity for the screening procedure was calculated at 0.67 and specificity at 0.96. Detailed results are presented in terms of the different conditions detected at screening (far, near, and anisometropic focus and orthoptic error), distribution of greatest axes at screening, and a comparison of initial videorefraction with repeat videorefraction and cycloplegic retinoscopy. CONCLUSIONS: A noncycloplegic screening procedure, simpler to perform than cycloplegic screening, succeeded in detecting a large proportion of infants with significant ametropia, particularly those with significant hyperopia, which is considered to be a strabismogenic and amblyogenic risk factor.
PURPOSE: The purpose of this study was to analyze the cost-effectiveness of an orthoptic screening program in kindergarten children. METHODS: An empiric cost-effectiveness analysis was conducted as part of a field study of orthoptic screening. Three-year-old children (n = 1180) in 121 German kindergartens were screened by orthoptists. The number of newly diagnosed cases of amblyopia and amblyogenic factors (target conditions) was used as the measure of effectiveness. The direct costs of orthoptic screening were calculated from a third-party-payer perspective based on comprehensive measurement of working hours and material costs. RESULTS: The average cost of a single orthoptic screening examination was 12.58 Euro. This amount consisted of labor costs (10.99 Euro) and costs of materials and traveling (1.60 Euro). With 9.9 children screened on average per kindergarten, average labor time was 279 minutes per kindergarten, or 28 minutes per child. It consisted of time for organization (46%), traveling (16%), preparing the examination site (10%), and the orthoptic examination itself (28%). The total cost of the screening program in all 121 kindergartens (including ophthalmic examination, if required) was 21,253 Euro. Twenty-three new cases of the target conditions were detected. The cost-effectiveness ratio was 924 Euro per detected case. Sensitivity analysis showed that the prevalence and the specificity of orthoptic screening had substantial influence on the cost-effectiveness ratio. CONCLUSIONS: The data on the cost-effectiveness of orthoptic screening in kindergarten may be used by such third-party payers as health insurance or public health services when deciding about organizing and financing preschool vision-screening programs.
In our comparative study of a Rodenstock sight-screener and a clinical eye examination, an orthoptic examination was included. The present study describes the orthoptic examination of 109 subjects and evaluates the predictive diagnostic value of Lang two-pencil test, TNO stereotest and Bagolini striated glasses. We found 14 orthoptic pathological cases most of which could be revealed by an accurate cover test. The TNO stereotest and the Bagolini glasses have high predictive diagnostic values of negative and even of positive tests. If one of these tests is used as a supplement to the ophthalmological examination and anamnesis, we find it to be a valuable hint of orthoptic normality or abnormality. If an orthoptic pathology is suggested, this must be followed by a complete orthoptic examination concerning diagnosis and treatment.
PURPOSE: Orthoptic screening in the kindergarten is one option to improve early detection of amblyopia in children aged 3 years. The purpose of this study was to analyse the cost-effectiveness of such a screening programme in Germany. METHODS: Based on data from the literature and own experience gained from orthoptic screening in kindergarten a decision-analytic model was developed. According to the model, all children in kindergarten, aged 3 years, who had not been treated for amblyopia before, were subjected to an orthoptic examination. Non-cooperative children were reexamined in kindergarten after one year. Children with positive test results were examined by an ophthalmologist for diagnosis. Effects were measured by the number of newly diagnosed cases of amblyopia, non-obvious strabismus and amblyogenic refractive errors. Direct costs were estimated from a third-party payer perspective. The influence of uncertain model parameters was tested by sensitivity analysis. RESULTS: In the base analysis the cost per orthoptic screening test was DM 15.39. Examination by an ophthalmologist cost DM 71.20. The total cost of the screening programme in all German kindergartens was DM 6.1 million. With a 1.5% age-specific prevalence of undiagnosed cases, a sensitivity of 95% and a specificity of 98%, a total of 4,261 new cases would be detected. The cost-effectiveness ratio was DM 1,421 per case detected. Sensitivity analysis showed considerable influence of prevalence and specificity on the cost-effectiveness ratio. It was more cost-effective to re-screen non-cooperative children in kindergarten than to have them examined by an ophthalmologist straight-away. CONCLUSIONS: The decision-analytic model showed stable results which may serve as a basis for discussion on the implementation of orthoptic screening and for planning a field study.
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.
The validity and permanence of orthoptic treatment for vergence deficiencies requires investigation due to the subjective nature of determining success in most clinical cases, i.e., the amelioration of symptoms and increases in vergence ranges. The relation between Risley prism vergences, a subjective measure, and vergence tracking rate, an objective index, is investigated. The course of orthoptics progress is compared in cases of clinical vergence dysfunction. Vergence-deficient control subjects showed no significant change in either index. However, trained subjects demonstrated rapid increases in both indices. The persistence of the training effect was monitored for up to 9 months. No regression was observed in subjects who met all release criteria, but one subject who chose to terminate therapy early showed a slow regression in tracking rate and recurrence of symptoms. These data support the validity of vergence training and increase the plausibility of previous clinical reports of orthoptics success.
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 (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 euro/QALY to 72 637 euro/QALY; the probability of an ICER <25 000 euro/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.
PURPOSE: The purpose of this study was to analyze the cost-effectiveness of orthoptic screening for amblyopia in kindergarten. METHODS: A decision-analytic model was used. In this model all kindergarten children in Germany aged 3 years were examined by an orthoptist. Children with positive screening results were referred to an ophthalmologist for diagnosis. The number of newly diagnosed cases of amblyopia, amblyogenic non-obvious strabismus and amblyogenic refractive errors was used as the measure of effectiveness. Direct costs were measured form a third-party payer perspective. Data for model parameters were obtained from the literature and from own measurements in kindergartens. A base analysis was performed using median parameter values. The influence of uncertain parameters was tested in sensitivity analyses. RESULTS: According to the base analysis, the cost of one orthoptic screening test was 7.87 euro. One ophthalmologic examination cost 36.40 euro. The total cost of the screening program in all kindergartens was 3.1 million euro. A total of 4,261 new cases would be detected. The cost-effectiveness ratio was 727 euro per case detected. Sensitivity analysis showed considerable influence of the prevalence rate of target conditions and of the specificity of the orthopic examination on the cost-effectiveness ratio. CONCLUSIONS: This analysis provides information which is useful for discussion about the implementation of orthoptic screening and for planning a field study.
Using data compiled from an earlier study of the results of the orthoptic treatment of divergence excess [Daum, K. M. Ophthal. Physiol. Opt. 4, 15-24 (1984)], a model has been presented regarding the results of the treatment. Provided the calibration sample is representative, the model may be used after an initial examination to predict the class of success a given subject will eventually be placed in as a result of orthoptic treatment. After treatment with a standard orthoptic regimen, the subjects were classified as being either totally successful (no objective or subjective visual difficulties) or partially/not successful. Stepwise discriminate analysis of 15 independent variables for the dependent variable success was used in order to choose the model with the highest coefficient of determination (r2) and the best statistical significance. The three variables chosen for the model were the angle of deviation at near and the blur and break values of the negative vergences at near. Using these variables, discriminant analysis was performed on the calibration sample of nine subjects. Each was classified correctly. The use and limitations of the model are briefly discussed.
The purpose of this paper will be to carefully examine the effectiveness of orthoptics as a viable treatment modality for strabismus. It will be necessary to first examine the scope of this problem and the significance of functional cure. A short discussion of perceptual and psychological effects will be included. A review of pertinent literature and an analysis of the data will be presented. Any commonalities or generalizations which can be identified will then be discussed and analyzed. Finally, the training of the optometrist in orthoptics and associated subjects will be examined to demonstrate the qualification of the optometrist to administer orthoptics in the treatment of visual anomalies.
The steady-state characteristics of the accommodation and vergence systems can be described by a model with six major oculomotor parameters. These include the system biases (tonic vergence and accommodation) and forward-loop gains (vergence and accommodative gains), as well as the interactive system gains (AC/A and CA/C ratios). We investigated these parameters in two populations: (1) 22 visually-normal asymptomatic individuals, and (2) 21 visually-abnormal symptomatic individuals before and after conventional orthoptic therapy. Two parameters related to system gain differentiated between the symptomatic and asymptomatic individuals: the slope of the fixation disparity curve with accommodation open-looped and the slope of the accommodative response/stimulus curve. Following orthoptic therapy, 4 static model parameters and 1 dynamic clinical parameter showed changes toward the normal mean; this included tonic accommodation, slope of the fixation disparity curve with accommodation closed-loop (2.5D), slope of the accommodative response/stimulus curve, the CA/C ratio, and the +/- 2D monocular accommodative flipper rate.