The Measurement of Vitreous Cavity Length and its Comparison Pre- and Postoperatively

Abstract

Objectives: To determine an accurate method of measuring the vitreous cavity lengths in pseudophakic patients and to compare the pre- and postoperative vitreous cavity lengths in various lens styles and between eyes implanted with the same lens style. To determine which lens style helps maintain the vitreous cavity length closest to its preoperative state. Study Design: A prospective study involving patients implanted with silicone prolene loop, silicone plate haptic and polymethyl methacrylate one-piece intraocular lenses implanted in eyes having undergone cataract extraction with endocapsular phacoemulsification with capsulorhexis and with an intact capsular bag. Setting: Anaheim Eye Medical Group, private practice, Anaheim, California. Patients: Twenty-three patients selected randomly from the cataract patients in the practice. Results: In the eyes implanted with silicone prolene loop lenses, the optic had a spread of 3.15 mm in its location along the axis of the eye and in 80% of the patients, the vitreous cavity was lengthened by as much as 2.17 mm.In the silicone plate haptic group, the spread was 1.45 mm and in 50% the vitreous cavity was shortened, the greatest increase in vitreous cavity length being only 0.77 mm.Using the equipment available at Anaheim Eye Medical Group, the Storz™ LT biometric ruler, it was not possible to accurately determine the vitreous cavity length in eyes implanted with polymethyl methacrylate lenses. Conclusions: The plate haptic lens design is more effective in helping to maintain the preoperative vitreous cavity length. The great variation of the location of the prolene loop lens optic along the axis of the eye explains some of the postoperative refractive surprises with loop lenses. The size of the capsulorhexis has nothing to do with the location of the prolene loop lens optic along the axis of the eye. Because of the more consistent location of the plate haptic lens along the axis of the eye, the ‘A’ constant for a plate haptic lens is more meaningful than for a prolene loop lens.