MEMS segmented-based adaptive optics scanning laser ophthalmoscope

Silvestre Manzanera,Carl J Kempf,Austin Roorda,Michael A Helmbrecht

doi:10.1364/boe.2.001204

Abstract

The performance of a MEMS (micro-electro-mechanical-system) segmented deformable mirror was evaluated in an adaptive optics (AO) scanning laser ophthalmoscope. The tested AO mirror (Iris AO, Inc, Berkeley, CA) is composed of 37 hexagonal segments that allow piston/tip/tilt motion up to 5 μm stroke and ±5 mrad angle over a 3.5 mm optical aperture. The control system that implements the closed-loop operation employs a 1:1 matched 37-lenslet Shack-Hartmann wavefront sensor whose measurements are used to apply modal corrections to the deformable mirror. After a preliminary evaluation of the AO mirror optical performance, retinal images from 4 normal subjects over a 0.9°x0.9° field size were acquired through a 6.4 mm ocular pupil, showing resolved retinal features at the cellular level. Cone photoreceptors were observed as close as 0.25 degrees from the foveal center. In general, the quality of these images is comparable to that obtained using deformable mirrors based on different technologies.

Highlights

In the early 1980s, Webb et al [1,2] devised a new ophthalmoscope to image the living human retina
Prior to using the AOSLO to obtain retinal images from human eyes, the quality of the adaptive optics (AO) correction was evaluated using a model eye, consisting of a lens that served as the refractive elements in the eye and a diffuse surface acting as the retina
The first parameter selected to evaluate the quality of the AO correction is, usually, the residual RMS of the wavefront measured by the wavefront sensor (WFS)

Summary

Introduction

In the early 1980s, Webb et al [1,2] devised a new ophthalmoscope to image the living human retina. This instrument, called the confocal scanning laser ophthalmoscope (SLO), was based on a confocal optical imaging system and a scanning laser light beam illuminating the retina. As in any other ophthalmoscope, the objective lens of the imaging system is the eye’s optical system comprised of the cornea and crystalline lens, which are affected by optical aberrations that degrade the quality of the retinal images. In order to solve this problem, adaptive optics (AO) was incorporated in the SLO.

Methods

Results

Discussion

Conclusion