Abstract
Abstract: :
Purpose:New research on retinal prosthetics and neural and stem cell transplantation is offering hope of some visual restoration to patients who are severely blind. It is difficult to quantitatively evaluate the potential value of these treatments because there are no good means to objectively measure vision in severely blind patients. The purpose of this study was to evaluate if testing the OKN elicited at various spatial frequencies would provide a more quantitative and objective means to assess visual function as a potential way to assist in pre– and post–operative assessment for clinical trials related to retinal prostheses and neural and stem cell transplantation. Methods:We tested the OKN responses of 17 subjects (for a total of 34 eyes with monocular stimuli and recording) in the presence of full–field optokinetic stimuli. Five subjects were adults with normal vision. Twelve subjects were patients with Retinitis Pigmentosa, Age Related Macular Degeneration, or Optic Neuropathy. Subjects were seated in the center of a cylindrical curtain and stripes of varying spatial frequencies (0.023 to 1.5 cycles/°) were projected on the curtain in front of them at increasing velocity to a maximum velocity of 55°/sec. Eye movements were measured with electrodes on the medial and lateral canthi of each eye. We analyzed the maximum velocity at which each subject’s OKN gain decreased to below normal threshold at various spatial frequencies. Using the maximum velocity, we computed the maximum number of stripes/sec the subject was able to follow at each spatial frequency and then found the highest spatial frequency each patient was able to follow at this velocity, giving us a maximum number of stripes/sec (SPSmax) for each subject. We analyzed the correlation between the SPSmax and the visual acuity and visual field for each patient using Pearson’s correlation coefficient. We used average horizontal visual field on Goldmann for each patient to quantify visual field results. Results: Our results showed that log SPSmax was well correlated to log visual acuity (R2 =0.69, p<.01). In addition, we found that SPSmax increased with increasing visual field, but the results were not statistically significant. Conclusions: Our data suggest that the SPSmax measure of OKN responses in severely blind patients may prove useful in some subjects for the pre– and post–operative evaluation of retinal prostheses and neural or stem cell transplants.
Keywords: eye movements • low vision • visual acuity