RESUMO
BACKGROUND: Portable autorefractors can estimate refractive error in remote locations, but sphero-cylinder comparison and donated-spectacle dispensing are not yet simple. METHODS: Normal astigmats determined best corrected acuity, then degraded 1 logMAR (Grade A), 3 logMAR (Grade B), and 6 logMAR (Grade C) to determine limits of astigmatism axis and power at these levels. The cylindrical refraction was vector transformed with J0 on the abscissa and J45 on the ordinate. RESULTS: Ten subjects produced multiple refractions at the interfaces of Grades A, B, and C representing ovals on the J0 and J45 coordinates. When rotated, the vertical axis represented 45° or 135°, the horizontal long axis was 1.6× the short axis. The size of the ovals positively correlated with cylinder power. Given a target refraction, the comparability of a candidate lens was demonstrated on our interactive database yielding a simple A, B, C, or worse grade for cylinder, spherical equivalent, and pupillary diameter. CONCLUSIONS/RELEVANCE: Inputting a remote autorefraction, pupillary diameter and age as target and a donated spectacle as the candidate with a "B" grade similarity would be expected to attain 20/40 acuity (3 logMAR degrade) if best corrected visual acuity was 20/20. This practical Excel database could facilitate widespread remote lay dispensing of the cylinder as well as spherical spectacles. The grade similarity can also compare refracting tools such as photoscreeners and hand-held autorefractors. CLINICAL TRIALS REGISTRY: NCT04297969.
RESUMO
BACKGROUND: Handheld devices can automatically give an estimate of refraction. The established method for refraction comparison using spherical equivalent (M) and J0, J45 vector transformations by Bland-Altman analysis is too complex for non-eye doctors involved with vision screening and remote vision clinics. Therefore, a simpler comparison technique was developed. METHODS: Based on the spectacle limit to resolve grade A 1 logMAR, B 3 logMAR and C 6 logMAR blur, J0, J45, and M are combined into the Alaska Blind Child Discovery (ABCD) composite ellipsoid GRADE system. Pediatric eye patients had confirmatory examination after dry refraction with three portable autorefractors: Plusoptix, 2WIN and Retinomax. The refractions were then compared using both Bland-Altman and ABCD composite. Performance to detect AAPOS amblyopia risk factors was also assessed. RESULTS: A total of 202 children, mean age seven years, 28% high spectacle need and 43% AAPOS 2013 amblyopia risk factors showed high correlation with cycloplegic refraction (intraclass correlation 0.49 to 0.90) for sphere, J0 and J45 spectacle components. Plusoptix had more (10%) inconclusives due to patients out-of-range. The Retinomax was unable to screen some younger children and was less reliable for sphere but gave more precise astigmatism estimates. The proportion of autorefractions expected to give GRADE A/B high-need patients acuity improvement to 20/40 would be 41% for Plusoptix, 39% for 2WIN and 65% for Retinomax. Sensitivity/specificity for amblyopia risk factor detection was 80%/83% for Plusoptix, 72%/88% for 2WIN and 84%/73% for Retinomax. CONCLUSION: The simplified spectacle comparison resembled Bland-Altman and could assist lay vision screeners and non-eye doctors attempting remote spectacle donation worldwide.