Maintaining the cornea and the general physiological environment in visualneurophysiology experiments

Neurophysiologists have been investigating the responses of neurons in the visual system for the past half-century using monkeys and cats that are ane sthetized and paralyzed, with the non-blinking eyelids open for prolonged p eriods of time. Impermeable plastic contact lenses have been used to preven t dehydration of the corneal epithelium, which would otherwise occur in min utes. Unfortunately, such lenses rapidly introduce a variety of abnormal st ates that lead to clouding of the cornea, degradation of the retinal image, and premature termination of the experiment. To extend the viability of su ch preparations, a new protocol for maintenance of corneal health has been developed. The protocol uses rigid gas permeable contact lenses designed to maximize gas transmission, rigorous sterile methods, and a variety of meth ods for sustaining and monitoring the overall physiology of the animal. The effectiveness of the protocol was evaluated clinically by ophthalmoscopy b efore, during, and after the experiments, which lasted 8-10 days. Histopath ology and quantitative histology were performed on the corneas following th e experiment. Our observations showed that this protocol permits continuous contact lens wear without adversely affecting the corneas. Thus, it is pos sible to collect data 24 h each day, for the entire duration of the experim ent. (C) 2001 Elsevier Science B.V. All rights reserved.