SUMMARY By using a small air bubble that fills about two thirds of the anterior chamber the erect image of the fundus of the aphakic human eye can be visualised clearly during vitrectomy, enabling the surgeon to operate without the need for vitrectomy lenses. The refractive power of the human aphakic eye is calculated here and the image site and size are presented.During vitreous surgery surgeons use different types of vitrectomy lenses that are either fixed to the corneosclera or held by an assistant to provide a clear view of the fundus. In patients undergoing vitrectomy the removal of the crystalline lens is rather common. In this paper we revive a simple old optical principle that we hope will simplify and shorten the vitrectomy techniques in aphakia.In our aphakic patients undergoing vitrectomy and in patients undergoing pars plana lensectomy and vitrectomy we were able to provide a clear view of the fundus during surgery simply by injecting through a limbal incision a small air bubble that fills one-half to two-thirds of the anterior chamber. Owing to the bubble's small size and to the minimal movement of the eye during surgery the back of the cornea was kept wet all the time, leading to perfect visibility during the whole procedure. This obviates the fogging effect caused by irregular wetting of the back of the cornea when the whole eye is filled with gas or air. Peripheral portions of the fundus were easily visualised by tilting the globe in the desired direction, the examination being aided by the superior position of the air bubble in the anterior chamber. The change in magnification owing to the relative peripheral corneal flattening is gradual and practically negligible.

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In this article, we demonstrated the unexpected reduction of optical zone diameter in myopic keratomileusis and its causes. Mathematical evaluation of optical zone diameter was made possible through a module added to a computer program. Optical zone diameter was reduced more in smaller corrections than in higher corrections. Practical measurements were parallel to mathematical expectations except in some small corrections between -4.00 and -6.00 diopters, where it was even more reduced than calculated. We were able to enlarge the optical zone diameter using the same computer module. Refract Corneal Surg 1991:7:161-1 66.)