Intraocular Lens Design Research Articles

Posterior capsule fibrosis and intraocular lens design

Four different posterior chamber lens designs were used in 1,845 consecutive, unselected extracapsular cataract extractions performed over a 31-month period in Vejle, Denmark. Ninety-seven eyes (5.3%) required a posterior capsulotomy during a postoperative observation period ranging from two to 32 months. At 16 months postoperatively, the cumulative capsulotomy rate was 7.1% with plano-convex anterior lenses, but only 1.7% with meniscus lenses and 1.8% with continuous ridged lenses. These results suggest that close contact between the posterior capsule and the optic could induce early posterior capsule opacification.

Modern intraocular lens implants in children with new age limitations

Seventy-three children received modern designs of posterior and flexible anterior chamber intraocular lenses. Twenty-eight (38%) had anterior chamber and 45 (62%) had posterior chamber lenses implanted. Postoperative implant complications occurred in 38 (54%) eyes, the most frequent was secondary membrane formation. Six eyes (22%) with anterior chamber lenses and 25 eyes (58%) with posterior chamber lenses required posterior capsulotomies. Seventy percent of the posterior chamber lens recipients less than six years of age developed secondary membranes. All of these eyes had a discission except one Nd:YAG laser patient. Forty-eight percent of the patients with posterior chamber lenses over six years of age required posterior capsulotornles: 55% had Nd:YAG laser capsulotomies and 45% had discissions. Based upon these observations, we now recommend primary implantation of flexible anterior chamber lenses in three- to six-year old children who have tissue-free visual axes and for all secondary implantations. Primary posterior chamber lenses are recommended for children six years of age and older and for younger children who will tolerate a Nd:YAG laser capsulotomy.

Practice styles and preferences of ASCRS members—1986 survey

A survey of the practice styles and preferences of 1986 ASCRS members was taken in the summer of 1986. A total of 4,042 surveys were mailed in June of 1986 and 1,184 were returned—a return rate of 29%. The responses were analyzed using D Base III. Response rate was 5% greater than for the 1985 survey. There was no financial incentive for return of the survey other than return postage paid for by the author. Three main profile areas were analyzed: age of the ophthalmologist; volume of cataract surgery per month, and geographic location. Areas of interest were surgery locations, surgical techniques, Nd:YAG laser application, intraocular lens design preferences, radial keratotomy, and advertising in ophthalmology. The influence of age of the ophthalmologist, cataract surgery volume, and geographic location were cross-analyzed for each question. The results were compared to the results of comparable questions in the 1985 survey. This report looks at each question and looks for variances from the national average, as well as for trends from the 1985 survey.

Analysis of capsular bag defects and intraocular lens positions for consistent centration

Radial anterior capsular tears frequently occur in posterior-chamber iris-plane phacoemulsification cases. These tears extend to the capsular bag equator and can allow the knee of an in-the-bag posterior chamber intraocular lens (IOL) to unfold a smaller anterior capsular remnant. This unfolding can allow the knee of the IOL loop to extend beyond the capsular equator, leading to IOL decentration. Typical anterior capsular radial tear configurations along with guidelines for IOL design selection and orientation after recognition of these tears are presented. Proper IOL centration was achieved in 255 of 262 patients (97%) in a study observing these guidelines.

Lens epithelial inhibition by PMMA optic: Implications for lens design

It has been a clinical impression that posterior chamber lens implants in some way inhibit opacification of the posterior lens capsule after extracapsular cataract extraction. The mechanism of this inhibition is unclear; it may be related to mechanical contact or blockage of migration of lens epithelial cells, or possibly to the leeching of toxic factors from the lens itself. A better understanding of the exact mechanism of opacification inhibition may have important clinical implications for intraocular lens design. For example, some lens designs that facilitate Nd:YAG capsulotomy by physically separating the posterior chamber lens and the posterior capsule may result in less inhibition and in fact more opacification of posterior capsules. We performed in vitro tissue culture studies of the effect of the polymethylmethacrylate (PMMA) optic of a planoconvex intraocular lens on cultured rabbit lens epithelium. These studies demonstrated both inhibition of lens epithelial migration beneath the PMMA optic (piano side down) as well as metaplasia and necrosis of lens cells growing directly beneath the optic. The clinical implications of these studies for intraocular lens design are discussed.

Intraocular lens damage associated with posterior capsulotomy: A comparison of intraocular lens designs and four different Nd:YAG laser instruments

A comparison of intraocular lens damage associated with four different Nd:YAG laser instruments was performed using polarized light, scanning electron microscopy, and a qualitative measurement of optical resolution. Five intraocular lens designs, each of which provided a different separation between the intraocular lens and a model of the posterior capsule, were tested with each laser instrument. There was no statistically significant difference in the frequency of lens pitting caused by each laser. Intraocular lenses designed with a theoretical separation of 0.25 mm or more between the lens and the posterior capsule sustained no damage with any of the laser instruments used in this study.

An analysis of semiflexible, closed-loop anterior chamber intraocular lenses

We present the pathologic and scanning electron microscopic findings from 44 semiflexible, all polymethylmethacrylate, anterior chamber intraocular lenses (IOLs). These IOLs, which have round, small diameter, closed loops were removed following a variety of complications, including uveitis and/or the uveitis-glaucomahyphema syndrome, secondary glaucoma, pseudophakic bullous keratopathy, cystoid macular edema, erosion into uveal tissue (with and without oval pupil), and iris neovascularization. Over 200,000 of these lens styles have been implanted. Even though the number of these IOLs accessioned in our laboratory is small, we feel this analysis documents some of the problems that may be encountered with this IOL design. Many of the complications documented in our series resulted in severe visual loss. In addition to tissue damage that appeared secondary to the mechanical tissue-to-implant interface, other causes of complications included variations in surgical technique, implantation into eyes with preexisting disease (including eyes that had undergone previous surgery), and damage to tissue that occurred during IOL removal.

The Surgeon's Guide to Intraocular Lens Implantation

The stated intent of this book is to provide a guide to both surgical technique and the principles of intraocular lens (IOL) selection and implantation. No attempt is made to discuss the profusion of specific IOL designs. Rather, lens types are discussed generically, with specific lenses cited "Clayman's approach is to draw general conclusions, after a summarization of the literature, from a clearly personal perspective." for illustration. After a succinct historic review of the development of IOLs, the topics of IOL materials, power calculation methods, and cataract surgical techniques are reviewed in succeeding chapters. The reasons for the abandonment of iris-fixated lenses, the growing domination of posterior chamber lenses, the role of anterior chamber lenses in extracapsular surgery, secondary implantation, complications, possible contraindications, and future trends are then discussed in turn. None of these subjects is addressed in full detail. Clayman's approach is to draw general conclusions, after summarization of

High-Speed Photographic Evaluation of Intraocular Lens Movements

Iridodonesis and pseudophakodonesis were examined in detail with a high-speed camera capable of picture rates up to 500/sec. Tilting, or "wobble," of iris-supported intraocular lenses was extreme, with a tilt of nearly 24 degrees with respect to the visual axis of the globe being documented, even with a moderate speed of globe rotation. Oscillations of the lens continued for several cycles after the globe stopped its rotation. Such lenses can, in some instances, tilt sufficiently to contact the endothelial surface of the cornea. In the case of some anterior chamber intraocular lenses, the iridodonesis is sufficient to cause constant rubbing of the iris on the posterior surface of the lens and its haptics , suggesting that vault, finish, haptic configuration, and placement of the lens may be critical factors in anterior chamber intraocular lens design.