Experience with an Accommodating IOL
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W e would like to report our experience with an accommodating intraocular lens. The first lenses were implanted in cataract patients in early 1991. Since then, the lens design has been modified to perfect centration and to give maximal accommodation. Fifty-five cataract patients have now been implanted with the lenses. An accommodating amplitude has been measured, varying from 1.25 diopters (D) to 3.50 D with an average of 2.75 D with one lens design. The accommodative amplitude is dependent on the action of the ciliary muscle and increases with time, which suggests that with use the muscle gains strength. The amplitude of accommodation was measured in two ways: (1) The patient was refracted in the normal manner. Pilocarpine was then instilled in the eye and the patient was again refracted. The difference between the two refractions was the accommodative amplitude. (2) The patient was placed in a dimly lit room and the distance correction was placed in the phoropter. Stepby-step -0.25 D lenses were placed in front of the eye, confirming with each addition that the patient could still read the best corrected vision. This was found to be the case in every patient, giving them a range of accommodation precisely controlled by the brain via the ciliary muscle. Constriction of the ciliary muscles moves the optic forward within the 5.0 mm capsular bag space and relaxation causes the lens to return to its posterior position within this space, the position of rest and distance vision. There is, therefore, precise control by the ciliary muscle of small degrees of movement of the optic along the axis of the eye. This movement can be demonstrated by comparing A-scans first done with a mydriatic and repeated later after the administration of pilocarpine. The lens is spherical and allows vision at all distances because of its movement in an anterior-posterior plane. All the light passing through the lens is focused in one place on the retina; there is therefore no loss of contrast nor any need to evaluate the patient's psychological suitability for this implant prior to surgery. There have been no surgical complications resulting in visual loss in these patients, the posterior capsulotomy rate is low, and the patients appear to continue to have accommodation after posterior capsulotomy. The surgical technique and selection of the lens power to be implanted is similar to that of modern cataract surgery except that a margin of error slightly on the plus side is preferred when selecting the lens power so that the patient can, if necessary, accommodate for best distance