Retinal contour and peripheral optical quality interactions in isomyopia and anisomyopia

Investigative Ophthalmology & Visual Science
Carles Otero; Enian kallamata; Gabriella Velonias; Juan Tabernero; Fuensanta A. Vera-Diaz

Purpose: Retinal contour and peripheral refraction parameters are not directly interchangeable. We analyzed the interactions of retinal contour and peripheral optical quality between eyes in relation with retinal eccentricity and type of refractive error.
Methods: Biometric parameters (Lenstar LS900, HaagStreit, Switzerland), including axial length (AL), and monochromatic aberrations (peripheral aberrometer, VopticaSL, Spain) were measured in a group of 11 subjects with isomyopia (mean SE -1.50±1.66 D, mean logMAR VA -0.08±0.04, mean age 24±1 years old) and 10 subjects with anisomyopia (mean SE -5.86±3.10 D, mean logMAR VA 0.0±0.03, mean age 24±1 years old). Measurements were taken at: the fovea, 20 degrees temporally and nasally, and 15 degrees superiorly and inferiorly in each eye. A conic function was used to convert axial length to retinal contours. Blur strength, logVS (log Visual Strehl) and RMS (Root Mean Square) optical quality metrics were computed using monochromatic aberrations up to the 5th order for a 4mm pupil. Peripheral measurements were normalized to each individual’s foveal measurements. A mixed model ANOVA with two within-subjects factors (eye{right,left}, retinal location{temporal, nasal, superior and inferior}), and 1 between-subjects factor (refractive group{isomyopia, anisomyopia}) was applied to retinal contour and both optical quality metrics.
Results: No significant interactions were found for logVS, Blur strength and RMS, but there was a main effect of refractive group for Blur strength (F=13.34, p<0.01) and RMS (F=14.52, p<0.01). For retinal contour parameters, there was a statistically significant main effect of refractive group (F=5.23, p=0.03) and retinal location (F=183.46, p<0.01) but there were also no statistically significant interactions.
Conclusions: Subtle differences between individuals with isomyopia and anisomyopia can be detected with both retinal contour biometry data and optical quality metrics independently. However, to conclude whether there are interactions among retinal locations, eyes and refractive groups, evaluation of higher levels of anisomyopia is needed. Interestingly, logVS provided different statistical outcomes than the other two metrics, suggesting that current single-value optical quality metrics should be evaluated in the periphery to decide which metric best describes the peripheral optical quality.