Péter Vámosi MD
Initial trials of an intraocular lens specifically designed to counteract negative dysphotopsia indicate that the lens is safe, well tolerated and effective at relieving patients of undesired optical complications after cataract surgery, according to Péter Vámosi MD, PhD, Péterfy Sándor Hospital, Budapest, Hungary.
“With the latest version of the lens, no patients reported negative dysphotopsia after implantation,” Dr Vámosi told delegates attending the XXXV ESCRS Congress in Lisbon.
Post-cataract dysphotopsia typically presents in two principal forms: negative dysphotopsia, with a dark crescent in the temporal field of vision, or positive dysphotopsia, with light streaks, arcs, flashes or starbursts.
Although likely multifactorial in cause, experience suggests that negative dysphotopsia occurs only with “in-the bag” IOLs and is prevented, relieved or improved when the IOL optic edge overlaps the anterior capsulotomy, either sulcus placed or with reverse optic capture, said Dr Vámosi.
Based on an idea by Samuel Masket MD, the Morcher 90S anti-dysphotopic IOL, which has received the European CE mark, was designed with a peripheral groove to accept the anterior capsule edge, allowing the bulk of the IOL to remain in the capsule bag with a portion overlying the capsule to avoid negative dysphotopsia.
Part of the optic overlies the capsule rather than vice versa, explained Dr Vámosi. The lens simulates reverse optic capture, a technique in which the anterior capsule edge is freed from the optic, and the optic is then elevated anterior to the capsulorhexis or capsule edge.
While initial results in the first 39 cases showed no incidence of negative dysphotopsia, other complications included capsule block in three patients and optic capture in another two cases.
In a design modification, fenestrations in the peripheral optic-haptic junction were created, which solved the problem of capsule block. However, optic capture was still an issue in five out of 48 subsequent implantations of the lens, said Dr Vámosi.
Further modifications to the lens design, this time extending the anterior optic from 6.0mm to 6.4mm, seems to have resolved the issue once and for all.
“In 13 cases of the latest version of the IOL implanted, there has been no incidence of negative dysphotopsia, no capsule block and no iris-optic capture,” said Dr Vámosi.
While the manufacturer recommends using a femtosecond laser to perform an anterior capsulotomy of 4.8-4.9mm, Dr Vámosi said that his own personal experience of more than 50 implantations of the IOL shows that a 4.5-5.5mm manual capsulorhexis also works well.
In addition to the absence of negative dysphotopsias, fixation within the anterior capsulotomy confers other advantages such as stable fixation, avoidance of anterior capsule contraction, absence of lens tilt, a stable toric axis, excellent centration, a more predictable effective lens position and decreased higher-order aberrations, he said.
Péter Vámosi: vamosipeter@freemail.hu
