Does the Accuracy and Repeatability of Refractive Error Estimates Depend on the Measurement Principle of Autorefractors?

Purpose: The purpose of this study was to determine the accuracy and repeatability of refractive errors obtained using three autorefractors based on different measurement principles, vis-à-vis, gold-standard retinoscopy. Methodology: Accuracy of noncycloplegic, sphero-cylindrical refractive error of 234 eyes was obtained using the rotary prism-based RM-8900 closed-field autorefractor, photorefraction based Spot vision screener, wavefront aberrometry based E-see, and streak retinoscopy by four different examiners, masked to the results of each other. Intersession repeatability of autorefractors was determined by repeat measurements in a subset of 40 subjects. Results: Retinoscopy values of M, J0, and J45 power vectors for the cohort ranged from -10.2 to 8 D, -1.4 to 1.8 D, and -0.9 to 1.2 D, respectively. Across autorefractors, the interequipment bias of M and J0 power vectors were statistically insignificant (< ±0.5 D; P > 0.05) but the corresponding limits of agreement were ±2.5 and ±1 D, respectively, without any trend across instruments or the patient's age (P > 0.5). Repeatability of M and J0 power vectors were ±0.75 D and ±0.40 D, respectively, across autorefractors. The range of J45 power vector was too narrow for any meaningful analysis. Conclusions: Refractive errors measured using autorefractors operating on different principles show minimal bias and good short-term repeatability but relatively large agreement limits, vis-à-vis, retinoscopy. Among them, the wavefront aberrometry based E-see autorefractor performs relatively better in all measurement parameters evaluated here. Translational Relevance: Although autorefractor estimates of noncycloplegic refractive error appears independent of their measurement principle, their relatively poor agreement with gold-standard retinoscopy warrants caution while used for screening and quantification of refractive errors.

Tribal Odisha Eye Disease Study (TOES) # 7. Prevalence of refractive error in children in tribal Odisha (India) school screening.

Purpose: To describe the prevalence of refractive error in school children in a tribal district, Rayagada, Odisha state, India. Methods: In a cross-sectional school eye health study, the students with diminished vision and other ocular abnormalities were referred for a further eye examination to the vision technicians after initial screening by the trained school teachers. The examination by vision technicians consisted of an external eye examination, photorefraction using a Spot screener and subjective correction. Those not improving with subjective correction were referred to the ophthalmologist for further examination. Results: The school teachers measured vision in 153,107 children; 5,990 students reached a vision technician. There was a near equal number of boys (50.06%) and girls (49.94%). The average age was 10.5 ± 2.63 (range: 5-15) years. The prevalence of refractive error was 9.7% (95% [CI]; 9.0-10.5%) in the vision technician-examined children. Myopia (4.9%) and astigmatism (5.4%) were more common than hyperopia (0.2%). The presenting visual acuity (PVA) was worse in children with hypermetropia (PVA 20/100-20/200 in 40% of children). Spherical equivalent of refractive error did not have a good correlation with age (R2 = 1.3); but increasing age was associated with increased risk of myopia (odds ratio 1.14; 95% CI 1.09-1.20; P < 0.001). Conclusion: The quantum of refractive error was close to other similar studies in India but the prevalence of myopia was relatively less.

Tribal Odisha Eye Disease Study Report # 6. Opportunistic screening of vitamin A deficiency through School Sight Program in tribal Odisha (India).

Purpose: To explore the possibility of vitamin A deficiency (VAD) detection through School Sight Program (SSP) in a tribal district of Odisha, India. Methods: In a cross-sectional observational study, we tracked school children with ocular signs/symptoms of VAD to their villages. The ophthalmologist examined their under-5 siblings and other under-5 children in the village. Information pertaining to family belief and practices of food, water, sanitation, and the socioeconomic status of the family were collected. Results: The ocular features of VAD were detected in 207 of 4801 (4.3%) examined children. This included 70 children (mean age 11 ± 2.6 years) detected in the school, 22 siblings (mean age 3.2 ± 1.2 years) of these children detected at their home, and 115 children (mean age 3 ± 1.5 years) detected in their habitat. The average family size was 5.8 ± 2.02 and the birth order of the child with VAD was 2.3 ± 1.25. Most parents were farmer, living in asbestos-roofed house, depended on public underground water, and practiced open-air defecation. The distribution of VAD in 207 children was conjunctival xerosis (X1A = 207; 100% of VAD and 4.3% of all children), Bitot's spot (X1B = 169; 81.6% of VAD and 3.5% of all children), corneal scar (XS = 3; 1.4% of VAD and 0.06% of all children), and night blindness (XN = 35; 16.9% of VAD and 0.72% of all children). Conclusion: An opportunistic screening for detection of VAD through a SSP could be cost-effective and complement the existing strategy.

Tribal Odisha Eye Disease Study (TOES) report # 5: Comparison of prevalence and causes of visual impairment among tribal children in native and urban schools of Odisha (India).

Purpose: To compare the prevalence and causes of blindness and visual impairment in tribal school students in the rural day-care and in a residential urban school. Methods: This was a cross-sectional comparative study. The 4-Stage screening in the native habitat of the tribal students performed in the school and hospital involved the trained school teachers, optometrists, comprehensive ophthalmologist, and pediatric ophthalmologist. The 2-Stage screening in the urban school involved only the optometrists and pediatric ophthalmologist. In both instances, vision (presenting and best corrected) was recorded and refraction performed. In addition, fundus photo was taken in all students in the urban school using a non-mydriatic fundus camera. Results: The comparison of blindness, visual impairment, and ocular anomalies were between tribal children (153,107 children; mean age 9.3 ± 2.7 years) examined in the native school and tribal children (10,038 children; mean age 8.8 + 1.64 years) in an urban residential school. Mild and moderate visual impairment was higher in the urban settings (P < 0.05), but severe visual impairment and blindness were similar in both settings. Refractive error, amblyopia, and posterior segment anomaly were detected more often in an urban settings (P < 0.05). Vitamin A deficiency (Bitot's spot) was detected only in children studying in the native schools (P < 0.05). Conclusion: The location, urban or rural, did not influence the visual impairment profile of tribal children. The food habit and environment seem to impact nutritional status.

Tribal Odisha Eye Disease Study (TOES # 2) Rayagada school screening program: efficacy of multistage screening of school teachers in detection of impaired vision and other ocular anomalies.

PURPOSE: To describe program planning and effectiveness of multistage school eye screening and assess accuracy of teachers in vision screening and detection of other ocular anomalies in Rayagada District School Sight Program, Odisha, India. METHODS: This multistage screening of students included as follows: stage I: screening for vision and other ocular anomalies by school teachers in the school; stage II: photorefraction, subjective correction and other ocular anomaly confirmation by optometrists in the school; stage III: comprehensive ophthalmologist examination in secondary eye center; and stage IV: pediatric ophthalmologist examination in tertiary eye center. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of teachers for vision screening and other ocular anomaly detection were calculated vis-à-vis optometrist (gold standard). RESULTS: In the study, 216 teachers examined 153,107 (95.7% of enrolled) students aged 5-15 years. Teachers referred 8,363 (5.4% of examined) students and 5,990 (71.6% of referred) were examined in stage II. After prescribing spectacles to 443, optometrists referred 883 students to stage III. The sensitivity (80.51%) and PPV (93.05%) of teachers for vision screening were high, but specificity (53.29%) and NPV (26.02%) were low. The specificity and NPV, in general, were higher in ocular anomaly detection but varied from disease to disease. CONCLUSION: Multistage school screening is rapid and comprehensive in a resource-limited community. Regular training and periodic reinforcement of teachers for vision assessment and other ocular anomaly identification are required for further success of the strategy.

Tribal Odisha Eye Disease Study # 4: Accuracy and utility of photorefraction for refractive error correction in tribal Odisha (India) school screening.

Purpose: To compare the photorefraction system (Welch Allyn Spot™) performance with subjective refraction in school sight program in one Odisha (India) tribal district. Methods: In a cross-sectional study school students, aged 5-15 years, referred after the preliminary screening by trained school teachers received photoscreening and subjective correction. The photoscreener was compared to subjective refraction in the range of +2D to -7.5D. Statistical analysis included Friedman nonparametric test, Wilcoxon signed-rank test, linear regression, and Bland-Altman plotting. Results: The photoscreener was used in 5990 children. This analysis included 443 children (187 males, 256 females, and the mean age was 12.43 ± 2.5 years) who received both photorefraction and subjective correction, and vision improved to 6/6 in either eye. The median spherical equivalent (SE) with spot photorefraction was 0.00 D (minimum -5.0D; maximum +1.6 D), and with subjective correction was 0.00D (minimum -6.00 D; maximum +1.5 D). The difference in the SE between the two methods was statistically significant (P < 0.001) using Friedman nonparametric test; it was not significant for J 45 and J 180 (P = 0.39 and P = 0.17, respectively). There was a good correlation in linear regression analysis (R2 = 0.84) and Bland-Altman showed a good agreement between photorefraction and subjective correction in the tested range. Conclusion: Photorefraction may be recommended for autorefraction in school screening with reasonable accuracy if verified with a satisfactory subjective correction. The added advantages include its speed, need of less expensive eye care personnel, ability to refract both eyes together, and examination possibility in the native surrounding.

Performance of Photoscreener in Detection of Refractive Error in All Age Groups and Amblyopia Risk Factors in Children in a Tribal District of Odisha: The Tribal Odisha Eye Disease Study (TOES) # 3.

PURPOSE: To evaluate effectiveness of Welch Allyn Spot Vision Screener in detecting refractive error in all age groups and amblyopia risk factors in children in a tribal district of India. METHODS: All participants received dry retinoscopy and photorefraction; children also received cycloplegic retinoscopy. Statistical analysis included Bland-Altman and coefficient of determination (R2). RESULTS: Photoscreener could not elicit a response in 113 adults and 5 children of 580 recruited participants. In Bland-Altman analysis mean difference of Spot screener spherical equivalent (SSSE) and dry retinoscopy spherical equivalent (DRSE) was 0.32 diopters (D) in adults and 0.18 D in children; this was an overestimation of hyperopia and underestimation of myopia. In Bland-Altman analysis of SSSE and cycloplegic retinoscopy spherical equivalent (CRSE) the mean difference was -0.30 D in children; this was an overestimation of myopia and underestimation of hyperopia. In regression analysis the relationship between SSSE and DRSE was poor in adults (R2 = 0.50) and good in children (R2 = 0.92). Cubic regression model for Spot versus cycloretinoscopy in children was: CRSE = 0.34 + 0.85 SSSE - 0.01 SSSE2 + 0.006 SSSE3. It was 87% accurate. Sensitivity and specificity of Spot in detecting amblyopia risk factors (2013 American Association for Pediatric Ophthalmology and Strabismus [AAPOS] criteria) was 93.3% and 96.9% respectively. Sensitivity of Spot screener in detection of amblyopia was 72%. CONCLUSIONS: Photoscreener has 87% accuracy in refraction in children. Its value could be used for subjective correction tests. TRANSLATIONAL RELEVANCE: Photoscreening could complement traditional retinoscopy to address refractive error in children in a resource-limited facility region.