Controlling the capsular shape in lens refilling.

Abstract

OBJECTIVES: To investigate control of the capsular shape by determining the ability of the lens capsule to mold injected silicone and to evaluate the relationship among the volume of silicone injected, refraction, and the amplitude of accommodation. METHODS: After endocapsular phacoemulsification following an upper, minicircular capsulorhexis, the lens capsule of a pig eye was refilled with a silicone mixture that polymerizes in vitro in 2 hours. The minicircular capsulorhexis opening was sealed by a small silicone plug to prevent leakage. The anterior capsule curvature and refraction of the lens were measured by a Scheimpflug camera and lensometer, respectively, with and without zonular tension. Zonular tension was created using a ciliary ring sutured to the ciliary bodies and expanded. RESULTS: The mean (+/- SD) anterior curvature of the lenses without zonular tension was 6.50 +/- 0.07 mm after 17 hours and 6.54 +/- 0.04 mm after 42 hours; with zonular tension it was 7.01 +/- 0.11 mm and 7.23 +/- 0.24 mm, respectively. The curvature became flatter when zonular tension was applied or steeper when zonular tension was abolished momentarily during measurements after 17 hours, but after 42 hours the curvature was unaffected by the application or removal of zonular pressure. The mean (+/- SD) amplitude of accommodation (the difference between refraction without zonular tension and that with it) was 3.2 +/- 0.5 diopters (D), 6.1 +/- 1.8 D, 4.8 +/- 0.8 D, and 2.8 +/- 1.3 D, when the lens was refilled with a silicone volume corresponding to 45%, 55%, 75%, and 95%, respectively, of the mean normal lens volume. CONCLUSIONS: The lens capsule possesses some ability to mold the injected silicone during its polymerization. When the eye is atropinized, the lens capsule may conform to its nonaccommodated state. Accommodation could be obtained by various degrees of refilling. Moderate refilling yields a greater amplitude of accommodation than does more complete refilling. Using a silicone plug to seal the capsular opening facilitates lens refilling with excellent reproducibility and seems to be useful in research.