Profile of peripheral refraction, choroidal thickness, and its correlation with refraction among children with myopia

Abstract

Purpose: Relative peripheral refraction (RPR) and choroidal thickness (ChT) are two of the important components associated with the progression of myopia. There is a paucity of knowledge on the distribution profile of these components among Indian children.

Methods: This is a prospective cross-sectional study involving 58 participants of age group 6-12 years. Axial length (ARGOS, Suntec, Inc., Aichi, Japan), peripheral refraction (WAM-5500, Grand Seiko CO. LTD., Hiroshima, Japan), and ChT (Deep Range Imaging, OCT-1, Atlantis, Topcon, Tokyo, Japan) of myopic children (-1.00 to -6.00 D) were assessed. Both RPR and ChT were assessed up to 20° at nasal and temporal eccentricities.

Results: The RPR showed mean hyperopia at both nasal and temporal 20° eccentricities (mean ± SD; 20° nasal: +0.30 ± 1.36 D; temporal 20°: +1.24 ± 1.52 D), and the difference in refraction was significant with temporal 20° showing higher hyperopic refraction compared to nasal 20° (-0.94 ± 1.94 D, P < 0.01). Thinning of the choroid was observed from center to periphery at temporal 20°: 213.04 ± 65.22 µm and nasal 20°: 136.78 ± 37.46 µm eccentricities compared to the sub-foveal ChT 270.18 ± 67.10 µm. A positive correlation between the peripheral refraction and peripheral ChT was observed.

Conclusion: Indian myopic children had hyperopic RPR along the horizontal meridian and thinning of the choroid from the center (SFCT) to the periphery. There is a positive relation between these two parameters.

Keywords: Choroidal thickness; myopia; peripheral refraction; relative peripheral hyperopia; relative peripheral myopia.

Figure 1

(a) WAM 5500 Binocular Accommodation Auto refractor shows the examiner’s view, (b) The participant’s view with red LED lights as the targets

Figure 2

(a) Representation of the horizontal unsegmented B-scan image of the SS-OCT, (b) SS-OCT image of segmented B-scan illustrating the upper border (Bruch’s membrane - top yellow line) and lower border (Chorio-scleral interface – bottom yellow line) of the choroid, red lines indicate the measured areas of the choroidal thickness with 5° intervals represented with green lines

Figure 3

Distribution profile of mean relative peripheral refractive error for 9 locations from nasal 20° to temporal 20° in 5° intervals. Error bars represent ±1 standard errors of the mean. N represents nasal eccentricities, C represents central and T represents temporal eccentricities

Figure 4

Distribution profile of mean peripheral choroidal thickness from nasal 20° to temporal 20° in 5° intervals (15° in the nasal eccentricity was not considered as it is the anatomical location of the optic nerve). Error bars represent ±1 standard error of the mean. N represents nasal eccentricities, C represents central and T represents temporal eccentricities