Kathryn J. Saunders

Purpose Controversy exists regarding the influence of peripheral visual experience on the onset and progression of childhood myopia. This longitudinal, observational study evaluated the relationship between relative peripheral refraction (RPR) and changes in refractive error and axial length (AL) over 12 months in White children aged 6–7 and 12–13 years with a range of baseline refractive errors. Methods Cycloplegic baseline autorefraction at horizontal retinal eccentricities of 0° and ±30° were recorded with the Shin‐Nippon NVision‐K 5001 while AL was measured using the Zeiss IOLMaster 700. Measurements were repeated after 12 months on a subgroup. Refractive data were transposed into power vectors as mean spherical equivalent (M), J 0 and J 45 . RPR was calculated by subtracting central from peripheral measurements. Participants were defined as myopic (M ≤ −0.50 D), premyopic (−0.50 D < M ≤ +0.75 D), emmetropic (+0.75 D < M < +2.00 D) or hyperopic (M ≥ +2.00 D). Results Data were collected from 222 and 245 participants aged 6–7 and 12–13 years, respectively. Myopic eyes demonstrated, on average, more hyperopic RPR. Emmetropes and premyopes displayed emmetropic RPR, and hyperopes showed a myopic RPR. Fifty‐six 6‐ to 7‐year‐olds and seventy 12‐ to 13‐year‐olds contributed 12‐month repeated measures. Longitudinal data demonstrated a significant relationship between a more hyperopic RPR in the nasal retina and greater short‐term axial elongation in teens with myopia at baseline (β = 0.69; p = 0.04). Each dioptre of relative peripheral hyperopia in the nasal retina was associated with an additional 0.10 mm (95% CI: 0.02–0.18 mm) annual increase in AL. Conclusions Hyperopic RPR in the nasal retina of myopic children is indicative of increased risk for rapid axial elongation and may be a useful metric to support decision‐making in myopia management.

Purpose We have previously demonstrated the upper limit of complete spatial summation (Ricco's area) to increase in non‐pathological axial myopia compared to non‐myopic controls. This study sought to investigate whether temporal summation is also altered in axial myopia to determine if this aspect of visual function, like in glaucoma, is influenced by reductions in retinal ganglion cell (RGC) density. Methods Achromatic contrast thresholds were measured for a GIII‐equivalent stimulus (0.43° diameter) of six different stimulus durations (1–24 frames, 1.1–187.8 ms) in 24 participants with axial myopia (mean spherical refractive error: −4.65D, range: −1.00D to −11.25D, mean age: 34.1, range: 21–57 years) and 21 age‐similar non‐myopic controls (mean spherical refractive error: +0.87D, range: −0.25D to +2.00D, mean age: 31.0, range: 18–55 years). Measurements were performed at 10° eccentricity along the 90°, 180°, 270° and 360° meridians on an achromatic 10 cd/m 2 background. The upper limit of complete temporal summation (critical duration, CD) was estimated from the data with iterative two‐phase regression analysis. Results There was no significant difference ( p = 0.90, Mann–Whitney U ‐test) in median CD between myopes (median: 44.3 ms; IQR: 26.5, 51.2) and non‐myopes (median: 41.6 ms; IQR: 27.3, 48.5). Despite RGC numbers underlying the stimulus being significantly lower in the myopic group ( p < 0.001), no relationship was observed between the CD estimate and co‐localised RGC number (Pearson's r = −0.13, p = 0.43) or ocular length (Pearson's r = −0.08, p = 0.61). Conclusions Unlike spatial summation, temporal summation is unchanged in myopia. This contrasts with glaucoma where both temporal and spatial summation are altered. As such, perimetric methods optimised to test for anomalies of temporal summation may provide a means to differentiate between conditions causing only a reduced RGC density (e.g., myopia), and pathological processes causing both a reduced RGC density and RGC dysfunction (e.g., glaucoma).