ADJUSTING THE SLIT-LAMP OCULARS - AN UNNECESSARY BURDEN OR A MUST

Adjusting the slit-lamp eyepiece rings is perceived by some to be insi gnificant for achieving adequate focus. Others assume that these rings should be set only to compensate for one's refractive error. Observat ions are presented concerning the eyepiece scale setting during routin e examinations, slit-lamp mounted YAG and Argon laser procedures and d uring ophthalmic surgery. Diagrams illustrate the optical basis of the se observations Factors influencing optimal eyepiece ring setting, bes ides ametropia, include slit-lamp misalignment (variations in calibrat ion) as well as unconscious accommodation. An inaccurate setting canno t be fully compensated by adjusting the slit-lamp joy-stick. When an i ncorrect setting is used, while using oblique illumination, it becomes impossible to focus on details placed at the center of the viewfinder In addition, irrespective of joy-stick position, it is impossible to view an oblique slit transecting the cornea in perfect focus. An accur ate setting, as a whole, results in sharper images throughout the slit -lamp examination. Differences between individual instruments make it necessary to reset the eyepieces for each eye and for each individual instrument. Methods are described for evaluating the need for readjust ment, as well as a simple technique for calibration in the absence of a focusing rod.