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San Francisco-The quest for relief of visual dysfunction for presbyopic patients continues with the design of a new accommodating lens-the OPAL posterior chamber accommodating IOL (Bausch & Lomb).
The current thinking is that 3 D of accommodation is needed for reasonably clear near vision. However, before the introduction of accommodating IOLs the other options, such as the conventional and multifocal IOLs, were less than ideal. The multifocal IOLs were a step forward but may be associated with decreased contrast sensitivity and problems with night vision.
This latest offering on the menu of accommodative IOLs was designed to take advantage of the power of the ciliary muscle, which is believed to remain intact until into the ninth decade of life. The OPAL IOL is a hydrophilic acrylic implant with a single optic that is designed to move forward in the eye with ciliary contraction to improve near focus, according to Dr. Nichamin.
The overall diameter of the IOL is 9.7 mm and the optic is 5.5 mm.
"What is unique about this particular IOL design is that it has three 'outrigger' haptics to fixate the lens and express energy to the optic itself during accommodation," Dr. Nichamin said. "The lens is designed to vault anteriorly upon accommodation as the diameter of the capsular bag decreases. It has a specially designed square edge to prevent the development of posterior capsular opacification. We hope the IOL will prove to be a well-designed and stable lens that will provide excellent distance acuity as well as enhance intermediate and near vision with anterior movement of the optic."
The other hope is that this lens will circumvent problems associated with multifocal IOLs, i.e., glare, halos, and decreased contrast sensitivity, and avoid any neural processing on the part of the patient with the lens implanted, he explained.
To date, 55 patients have been enrolled in a prospective, unilateral, open-label, noncomparative study of the OPAL IOL at three international sites, two in Germany and one in the United Kingdom.
The investigators analyzed the following parameters: best-corrected distance visual acuity, the best distance-corrected near visual acuity, near point of accommodation, defocus curve, and objective accommodation. The data from these patients, as Dr. Nichamin pointed out, are very preliminary.
The median best-corrected distance visual acuity of all patients was 20/20. However, he reported, one patient had undiagnosed macular disease that affected the curve, but the best level achieved was 20/13, he reported. The median best distance-corrected near visual acuity was 20/50 or J6; the best level achieved was 20/25 or J2. The median near point of accommodation was about 36 cm or 2.78 D. The defocus curve, obtained from a cohort of about 20 patients, revealed a median of 2.3 ± 1.2 D of subjective amplitude. Finally, objective accommodation was only about 0.5 D (maximum, 0.2; minimum, 1.6).
"The results of this study, keeping in mind how preliminary they are, indicate that the design characteristics of this one-piece hydrophilic acrylic accommodating IOL appear to provide some lens movement that will have to be validated further," Dr. Nichamin said. "The IOL may provide patients with increased amplitude of accommodation. The best-corrected distance vision is excellent, as with standard monofocal IOLs. The lens design will be further optimized based on this early performance, analysis, and trials."