Asymmetric Peripheral Refraction Observed in Patients of Indian Descent With Myopia

Patients with Indian heritage who have myopia often exhibit an asymmetric type of peripheral refraction in the horizontal meridian, along with relative hyperopic defocus in the temporal retina and myopic defocus in the nasal retina, according to research published in Optometry Vision Science.

Researchers conducted comprehensive eye exams on 161 patients (age range 18-33 years, 65% women) of Indian ethnicity. They performed central and peripheral refractions with an open-field autorefractor using 10° intervals up to ±30° in the horizontal meridian, and 5° intervals up to ±15° in the vertical meridian. They measured axial length and central corneal radius with an optical biometer.

The team stratified participants into 1 of 3 groups based on spherical equivalent (SE) refractive error: emmetropia (SE±0.50 D, n=44), hyperopia (SE>+0.50 D, n=37), and myopia (SE<-0.50 D, n=80). They further classified patients in the myopia group as having low (-0.5>SE>-3.00 D, n=51) or moderate (-3.00≥SE≥-6.00 D, n=29) myopia.  

The investigators found that patients with myopia exhibited relative peripheral hyperopia in temporal eccentricities and relative myopia in nasal eccentricities (N30°: −0.37±0.13 D vs T30°: +0.56±0.11 D, P <.05). They also observed relative peripheral myopia in both nasal and temporal eccentricities for patients with emmetropia and hyperopia, and found relative peripheral myopia along the vertical meridian for participants in all 3 cohorts.

The researchers note that their findings of peripheral hyperopic defocus at temporal 30° in patients of Indian descent with moderate myopia are in contrast to a study reporting a higher magnitude of relative peripheral hyperopia in patients of Chinese heritage with myopia. “This large difference in peripheral refraction between these two populations, despite the similar mean refractive error, could be attributed to the possible differences in retinal shape associated with ethnicity,” according to the investigators.

However, the report states that the subgroups with myopia did share comparable asymmetry in their peripheral refraction observed in patients with moderate myopia who were White.

Limitations of the study include a single center design, the potential for geographic bias, and the exclusion of children from the analysis.

Reference

Yelagondula VK, Achanta DSR, Panigrahi S, Panthadi SK, Verkicharla PK. Asymmetric peripheral refraction profile in myopes along the horizontal meridian. Optom Vis Sci. 2022;99(4):350-357. doi:10.1097/OPX.0000000000001890