MANUAL LENS STRETCHING APPARATUS (MLSA) FOR RAPID ANALYSIS OF THE OPTICAL PROPERTIES OF THE NATURAL LENS, ACCOMMODATING IOL AND REFILLED LENS CAPSULE (PHAC0–ERSATZ).

Abstract

Abstract: : Purpose: Design and validate a compact portable instrument to rapidly measure and compare the accommodative optical properties of crystalline and implanted lenses. Methods: MLSA is a metal ring with spring–loaded plungers terminated with a ball fitting a socket machined in PMMA segment milled to fit the globe 2mm below the limbus. Twisting a lever retracts the segments by 2mm away from the center giving a 4mm total diameter stretch. To facilitate dissection, a cylindrical holder with a glass window was made to fit the apparatus. After removal of conjunctival, fatty and muscle tissues, the globe is bonded to the 8 segments of the apparatus using cyanoacrylate. The posterior pole is sectioned, a vitrectomy performed, and the apparatus is flipped over and a 360^o section is made 0.5mm below the limbus and the cornea and iris are removed. The 50mm high cylindrical holder is filled with a saline solution to prevent tissue dehydration. Un–stretched and stretched lens diameter measurement are made on a shadowphotogrammetric system with the apparatus fully immersed in BSS, lens thickness on a operation microscope equipped with a 30^o slit–illuminator and a digital camera, and optical power measurements with a Scheiner system. For assessment of image quality, another annular ring was made to hold the tissue on an optical bench. Once measurements on the crystalline lens have been made, MLSA is remounted on the cylindrical holder for surgery and IOL implantation or lens capsule refilling. After measurements, the assembly is immersed in formalin or glutaraldehyde for histology. Results: MLSA was used in 5 eyes to analyze the effect of tissue preservation and showed a ∼5% lens diameter change due to stretch over 3 days when tissues where immersed in BSS at 3^oC; no measurable changes occurred after 24hrs with 0.3% formalin. In an ongoing study, MLSA showed >8% changes in a refilled lens capsule but no changes in 2 eyes implanted with a conventional IOL. Conclusions: MLSA is useful for rapid testing of accommodation. CR: NONE. Support: NIH grant EY14225; FL Lions Eye Bank; Vision CRC, Sydney Australia; Fight for Sight; Research to Prevent Blindness, NY, NY; Henri and Flore Lesieur Foundation, Palm Beach, FL.

Keywords: small incision cataract surgery • refractive surgery: phakic IOL • optical properties