Abstract
Purpose :
Reliable and repeatable measurements of peripheral refraction are important in assessing eyes for clinical study of myopia. A slit-scanning ophthalmoscope could be a comparatively inexpensive instrument for reliably measuring peripheral refraction. We performed a prospective, test-retest reliability study in order to validate the repeatability of peripheral refraction measurements on a slit-scanning ophthalmoscope system.
Methods :
Peripheral refraction measurements over a 90° field-of-view (FOV) were acquired for 16 eyes of 16 subjects with a range of refractive errors (-9.5 to +4.0; average: -2.91D). Each eye was dilated with tropicamide and phenylephrine fifteen minutes prior to imaging with a widefield slit-scanning ophthalmoscope (CLARUS™ 500, ZEISS, Dublin, CA) with prototype software that measures the relative vertical shift on the retina of two beams entering the eye, thus measuring the vertical component of the peripheral refraction. The same operator tested each eye 3 times, with a break between each measurement to realign the eye. Peripheral refraction was computed as relative peripheral refractive error, i.e. as the difference between the refractive error 30° temporally and the central foveal refractive error. Repeatability of the system was assessed with a Bland-Altman analysis using the last 2 measurements, and test-retest standard deviation (TRT-SD) using all 3 measurements.
Results :
Intra-subject repeatability was observed through a Bland-Altman analysis with 95% limit of agreement (LoA) (r = 0.95, lower LoA: -1.06, upper LoA: 1.88; Figure 1A). The TRT-SD was 0.72D. The established trend that increasing myopia is associated with relative hyperopia in the periphery is revealed for this dataset (Figure 1B).
Conclusions :
The repeatability of a measure of peripheral refraction, using a widefield slit-scanning ophthalmoscope, was demonstrated. Possible sources of variability could include changes in pupil alignment, or orientation of patient fixation.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.