Abstract
Purpose :
Measurements of eye shape and peripheral refraction may be useful for clinical study of myopia. However, the fact that some measurement techniques are expensive and not widely available (e.g., magnetic resonance imaging, ultrasonography) has hindered progress in this area. We applied clinical retinal imaging technologies to measure peripheral refraction and several metrics of ocular shape.
Methods :
For 20 subjects, we acquired biometry data for both eyes (IOLMaster®, ZEISS, Jena, Germany). A widefield slit-scanning ophthalmoscope (CLARUS™ 500, ZEISS, Dublin, CA) with prototype software was used to map vertical peripheral refraction over a 90° field-of-view (FOV). Relative peripheral refractive error (RPRE) was computed as the difference between refractive error 30° temporally and on-axis refractive error (RE). For 14 eyes we acquired widefield optical coherence tomography (OCT) B-scans (2048 A-scans, 24 mm lateral FOV, 6mm depth), using a prototype 200kHz swept-source system. Automated multi-layer segmentation was used to delineate retinal layer boundaries. Retinal radius of curvature estimates (RROC) were derived from the B-scans and axial lengths (AL), using a model-based approach.
Results :
Figure 1 shows a peripheral refraction map and curvature-corrected OCT B-scan. As illustrated in Figure 2, we observed significant correlation between RPRE and AL (OD: r=0.80, p<0.01), as well as between RPRE and RE (OD: r=-0.84, p<0.01). However, we observed no significant association between RPRE and either RROC or corneal power.
Conclusions :
Relative peripheral hyperopia was associated with higher myopia and longer axial length, as shown by previous studies. However, the lack of a strong association with retinal or corneal curvature suggests that peripheral refraction may not necessarily be a good indicator of overall eye shape. The retinal imaging technologies we employed are comparable to commercially-available clinical systems, which are relatively inexpensive compared to some other techniques for eye shape assessment. The described methods might therefore be of interest to clinicians and researchers of myopia development.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.