Controlling the capsular shape in lens refilling
O. Nishi, K. Nishi, C. Mano, M. Ichihara and T. Honda
Nishi Eye Hospital, Osaka, Japan.
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.
