Abstract
Purpose: The Hartmann-Shack (HS) wavefront sensor was used to determine the peripheral refraction (PR) at specific angles in subjects with age related macular degeneration (AMD) (Lundström et al., Optom Vis Sci 2007). The correction of the PR in those subjects could improve their visual acuity at eccentric locations. However, instrumentation specifically designed for accurate and fast measuring PR was never tested in those patients. Easy determination of PR could provide those patients with customized corrections.
Methods: We adapted a fast scanning peripheral HS wavefront sensor previously developed (Jaeken et al., Opt Exp 2011). Its design makes it possible to measure fast (order of seconds) and with a high angular resolution (1 measurement/°) a large part of a horizontal meridian of the visual field (50°). Two fixation methods were tested: placing the target in the patient’s preferred retinal location (PRL) and having the PRL aligned to the center of the measuring system. For both applications a red laser beacon was projected on a wall at 2 meter from the patient. The stability of fixation while scanning was determined looking at the position of the pupil in each frame of a scan. PR (sphere and cylinder) was determined from the series of recorded HS images. The repeatability of 4 consecutive scans was compared with that in normal elderly eyes. The light distribution within the HS spots was evaluated intra-patient between the different retinal areas.
Results: No variation in the quality of the HS images was observed between the areas with and without retinal damage. Small displacements of the centre of the pupil were registered, although this did not affect the refraction results. The repeatability of the 4 scans in eyes with AMD was not different from that in normal elderly eyes. In some subjects anomalies were observed in the HS images which are presumed to come from a plane close to the pupil plane. Since some of the patients did not undergo cataract surgery, it probably comes from crystalline lens opacities. The measured PR of PRL varied among subjects.
Conclusions: An adapted scanning peripheral wavefront sensor was found to be a functional tool for measuring fast and accurately the PR in AMD patients. This refractive information can be useful for customized corrections. For example, they could benefit from a custom designed intraocular lens adjusted to their exact PR at their PRL.
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