Abstract
Purpose :
Pupil alignment is fundamental to achieving good quality retinal imaging. Typical measures of peripheral refraction are performed using autorefractors, however it has previously been shown that slit-scanning ophthalmoscopes can be used to measure peripheral refraction over a wide field of view. A prospective study was performed to examine the effect of pupil alignment on peripheral refraction with a slit-scanning ophthalmoscope.
Methods :
Peripheral refraction measurements were acquired using a widefield slit-scanning ophthalmoscope (CLARUS™ 500, ZEISS, Dublin, CA) with prototype software on a model eye (7mm Imaging Eye Model, Ocular Instruments, Bellevue, WA). A custom translation stage was used to offset the model eye’s pupil location relative to the instrument’s exit pupil, by known amounts in the x, y, and z directions. The vertical component of refraction was computed from the slit-scan data. Relative peripheral refraction measures were computed by taking the difference between the refractive error at 30° temporally and the central refractive error. Sample peripheral refraction data on a normal human eye (with -0.25 D refractive error) was also acquired. During several acquisitions, co-alignment between the pupil and the instrument was monitored using the instrument’s built-in iris cameras.
Results :
In Figure 1, a graph of relative peripheral refraction vs. pupil offset for each of three axes (x, y, z) is shown for both the (A) model eye, and the (B) human eye. The subject’s pupil size limited the range of measurement in x and y.
Conclusions :
Studies using autorefractors show that variation in pupil alignment has an impact on the accuracy of peripheral refraction measurements (Ehsaei et al. Ophthalmic and Physiological Optics, 2011). Our results using the slit-scanning ophthalmoscope suggest that peripheral refraction maps obtained with this technique also can vary with pupil position. In order to maximize reliability of such measurements, it is therefore important to minimize pupil decentration during the data acquisition.
This is a 2021 Imaging in the Eye Conference abstract.