Bubble-free Gonioscopy

Abstract

Accurate gonioscopy is necessary for the diagnosis and the treatment of glaucoma. The "gold standard" for indirect gonioscopy has been the Goldmann 3-mirror lens, requires an optical coupling agent (methylcellulose) between the cornea and under the surface of the goniolens. The design of an ideal lens would not only eliminate the need for gel, but could at the same time solve the problems associated with the trapping of an air bubble under the lens. This investigation involved a prototype 2-mirror goniolens with a radius of curvature of 8.4 mm and a 16 mm diameter area of corneal contact. A total of, 69 consecutive patients had bilateral keratometer measurements made. The prototype 2-mirror lens was applied to the anesthetized eye. The results of this examination were tabulated by one of the authors (F.M.K.); A=good fit without trapping of air, B=good fit but trapped bubble of air which could be expelled by the patient turning their eye towards the bubble, and C=total failure to expel the trapped bubble of air. Finally, if there were wrinkles in Descemet's membrane, this was recorded. A total of 64 patients were evaluated with a prototype 2-mirror lens. In total, 54/64 (84.38%) of eyes were successfully evaluated without trapping of an air bubble. Our stated goal of eliminating the need for gel as a coupling agent without trapping of an air bubble was successful in 54/64 eyes (84.38%). Our findings could spur development of newer bubble-free goniolenses for procedures such as laser trabeculoplasty.