Modified Ridley lenses.

A MODIFICATION of the original Ridley acrylic implant suggested in a previous communication (Epstein, 1957) comprised a biconvex lens of larger diameter (9.4 mm.) and thinner central thickness (1 5 mm.), and with a naturally tapering edge instead of a relatively thick square edge. It was found that such a lens facilitates centration, and adjusts itself almost automatically after insertion, little or no additional manipulation being necessary. The fact that the iris is separated from the posterior capsule over a larger area lessens the risk of adhesions between these two layers, and the thin tapering edge of the lens minimizes the undesirable effects of iris pucker which may be produced by these peripheral posterior synechiae. The greater thickness and relatively thick edges of the original Ridley lens allow the formation of large synechiae which pucker the iris and may draw the pupil towards the edge and cause dislocation of the lens. The modified lens being thinner allows a deeper anterior chamber, and the fact that the volume and mass of the lens are less despite its larger surface area makes it more stable in situ. Because the pressure on the zonule and posterior capsule and on the posterior surface of the iris is lessened, there is more freedom for the circulation of the aqueous in the posterior chamber and between the lens and posterior capsule. The larger diameter may make it more difficult to insert the lens through the pupil, but a few drops of adrenaline 1/1000 from an ampoule applied directly to the iris dilates the pupil and makes this manoeuvre easier.