The population is rapidly aging. Previous studies of the effect of aging on the retina and particularly the retinal cone photoreceptors have provided conflicting information on age-related changes. These previous studies were based on post-mortem samples.

In our experiment, we obtained measurements of the cone mosaics from 0.18mm to 3.5mm (approximately 0.6 deg to 12 deg) retinal eccentricity in 4 meridians from 20 subjects in two age groups using an adaptive optics scanning laser ophthalmoscope (AOSLO). Cone packing analysis of the cone mosaics was performed. Results showed cone photoreceptor packing density was lower in the older subject group than in the younger subject group within the central 0.45 mm (raidus) of the retina. No significant difference with age was found beyond 1.1 mm except in the nasal retina, where the older group had a slightly higher cone density.

It has been demonstrated that normal aging will increase retinal scattering and pathology in aging related eye diseases will scatter more light. To further improve the ability to study the aging and diseased retina, we implemented polarization imaging techniques in our AOSLO system. We developed a high resolution adaptive optics scanning laser polarimeter by coupling a quarter wave plate and an analyzer in the detection channel. 3 healthy subjects were tested using this polarization sensitive AOSLO. This system measured the Stokes vector of the retina at the cellular level, but limitations for practical use were identified. To address these limitations, we constructed a second generation AOSLO polarimeter by introducing dual electro-optical modulators into the detection channel. This high speed polarization technique can measure over 500,000 Stokes vectors per second. The high speed can effectively decreases the effects of eye motions induced errors in polarization measurements, improving the contrast of retinal imaging of structures according to their polarization properties.