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Thomas W Raasch, Joseph C Lehman; Meridional subjective refraction with spherical lenses and oriented targets. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4758. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate the clinical performance of a meridional subjective refraction method, that requires relatively simple equipment, consisting minimally of spherical lenses and oriented viewing targets.
Meridional subjective refraction was performed on 70 eyes of 35 normally-sighted subjects with natural pupils and accommodation. Test-retest measurements within and between sessions were performed. Targets were Gaussian-attenuated square wave gratings at four orientations: 0○, 45○, 90○, and 135○. At each orientation, the spherical dioptric power to yield maximum subjective clarity was determined. Spherical equivalent (M), J0, and J45 values were calculated from the dioptric values at these four orientations. Measurement precision was evaluated using test-retest difference distributions of M, J0, and J45, and with cumulative probability plots for astigmatic and total dioptric power differences. A goodness-of-fit metric was derived from sum-of-squared deviations between measured values and the best-fitting sphero-cylindrical power. Visual acuity was measured with each resulting sphero-cylindrical correction.
Median test-retest differences for astigmatism are similar to published values for standard subjective refraction: ~0.13 D for both. Median differences for total dioptric power are larger than published values (0.26 D vs 0.20 D). The 95th percentile level for astigmatic and total dioptric difference are larger by ~25% and ~40%, respectively. LogMAR acuity is significantly correlated with the goodness-of-fit metric.
This subjective refraction method results in median test-retest difference values that are similar to those found with standard subjective refraction. However, the larger 95th percentile values for both astigmatism and total dioptric difference suggest that outliers are more likely with this method. This refraction method could potentially be adapted for use in environments where full clinical resources and highly-trained personnel are not available.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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