Investigating Optical and Neural Causes of Vision Loss

Vision loss has become a major public health problem due to the growth and aging of the population. Age-related macular degeneration (AMD) is the most common cause of vision loss in people over 50 years of age. In the United States, over 10 million people have AMD and over 1.6 million people age 50 and older have late-stage advanced AMD. It is well established that AMD patients with central vision loss use preferred retinal loci (PRL) which are peripheral retinal areas adjacent to the fovea for performing daily activities, such as reading. However, even in healthy eyes, peripheral vision is limited due to reduced neural sampling density compared to the fovea. Additionally, the function of the peripheral retina can be further reduced in patients, owing to degenerative disease processes. These neural substrate losses are coupled with losses in the quality of the optical image on the retina. Optical imperfections increase with age and off-axis viewing, compared to viewing along the optical axis of the eye. The combination of these factors plays a significant role in reducing visual performance of patients with eccentric fixation. The long term goal of the project is to improve the visual performance of veterans with central vision loss by development of innovative approaches that will optimize the benefit of vision rehabilitation techniques. In the current proposal, optical and neural losses will be assessed in AMD patients with central vision loss using novel techniques. Increased optical losses due to age and viewing off the optical axis of the eye will be established with wavefront analysis technology. Increased neural losses due to retinal dysfunction at PRL will be determined based on measurement of visual acuity with blurred stimuli. Improvement in reading speed will be evaluated, conditional on neural losses at PRL and/or the stability of PRL, after compensating for optical losses with our adaptive optics system. The findings will provide knowledge of PRL function and stability that is beneficial for improving the outcome of available vision rehabilitation methods that train patients to better use their PRLs. Also, customized correction of optical imperfections of the eye for effectively improving visual performance can be developed as an approach for better vision rehabilitation of patients. Optimizing vision rehabilitation of our veterans will allow them to maintain function and productivity.