Intraocular Lens Implantation National Institutes of Health
Consensus Development Conference Statement
September 10-11, 1979
This statement is more than five years old and is provided solely for historical purposes. Due to the cumulative nature of medical research, new knowledge has inevitably accumulated in this subject area in the time since the statement was initially prepared. Thus some of the material is likely to be out of date, and at worst simply wrong. For reliable, current information on this and other health topics, we recommend consulting the National Institutes of Health's MedlinePlus http://www.nlm.nih.gov/medlineplus/.
This statement was originally published as: Intraocular Lens Implantation. NIH Consens Statement 1979 Sep 10-11;2(7):37-42.For making bibliographic reference to the statement in the electronic form displayed here, it is recommended that the following format be used: Intraocular Lens Implantation. NIH Consens Statement Online 1979 Sep 10-11 [cited year month day];2(7):37-42.
A Conference on intraocular lens implantation was held at the National Institutes of Health on September 10-11, 1979.
The NIH Consensus Development Program brings together practicing physicians, biomedical research scientists, consumers, and others in an effort to reach general agreement on the safety and efficacy of a medical technology, whether it be a drug, device, or procedure.
Since the late 1960's, intraocular lenses (IOLs) have been used in the United States with increasing frequency as an alternative to eyeglasses and conventional contact lenses in restoring useful vision to cataract patients. The IOL, usually made of plastic, is implanted permanently into the eye during cataract surgery, following removal of the clouded natural lens of the eye. Although approximately one-fourth of the estimated 400,000 cataract operations performed each year in the U.S. now involve implantation of IOLs, questions continue to be raised about the use of these devices. This conference provided a forum for discussion of IOLs by experts in ophthalmology and vision research, as well as representatives of consumer and professional groups. Following an historical review of intraocular lenses, seven panels convened to discuss the topics indicated below. In addition, studies of intraocular lenses either planned or in progress were reviewed, and organizations and individuals interested in intraocular lenses were given an opportunity to make public comment.
Lens Design and Manufacture
Since implantation of the first intraocular lenses by Harold Ridley, M.D., F.R.C.S., in 1949, these devices have undergone a continuous evolution in design, weight, and manufacturing process. Also, surgical techniques for inserting IOLs, and for cataract extraction as well, have been considerably refined during this time. However, the plastic material most frequently used in the optic or lens portion of such lenses--polymethylmethacrylate (PMMA)--has remained the same.
The panel on Lens Design and Manufacture considered lens materials currently used for the optic and haptic (loop) portions of the device, techniques of lens manufacture, quality control, and evaluation of the lens by the surgeon. The panel agreed that currently used lens materials, with the exception of metal loops, are generally satisfactory, although they may contain substances which influence tolerance. Improved tolerance should be one goal of future research. It is also desirable to search for improved materials or coatings which minimize possible damage to the endothelium.
The panel called for industry-wide adoption of uniform physical and chemical manufacturing standards, and concluded that all current alternative IOL fabrication techniques are satisfactory, provided that stringent quality control is maintained. The panel called for continued cooperation among the research, manufacturing, and ophthalmic communities to improve further lens implant design and materials development.
Preoperative Evaluation of the Patient
The panel on Preoperative Evaluation of the Patient agreed that a careful examination of the cataract patient before surgery is important, whether or not intraocular lens implantation is planned. The results of the examination should be written into the medical record. For those who are to undergo lens implantation, careful slit lamp examination of the eye is imperative to rule out abnormalities that may contraindicate IOL implantation, in addition, there was a consensus that A-scan ultrasonography is of definite benefit in the preoperative examination. Although specular microscopy is also considered to be a valuable clinical and research tool, the panel said that it is not presently considered a routine part of the examination prior to primary lens insertion. The panel suggested that further studies to correlate maintenance of corneal clarity with endothelial cell count might help to clarify this instrument's role in predicting the development of corneal edema following lens implantation. Such studies were strongly recommended by the panel.
Indications and Contraindications for Intraocular Lens Implantation
The panel on Indications and Contraindications for Intraocular Lens Implantation agreed on broad general guidelines for ophthalmic surgeons who perform intraocular lens implantation.
The panel recommended that in general intraocular lens implants be restricted to the elderly, that they be implanted in the eyes of slightly younger patients only when contact lenses or spectacles are not likely to provide adequate visual function, and that they initially be restricted to one eye unless the needs of the patient dictate otherwise.
The panel also acknowledged other possible special indications for IOL implantation, as follows:
- Patients whose occupation may rule out contact lens wear;
- Elderly patients with an advanced cataract in one eye and visual acuity of 20/40 to 20/60 in the other eye, or exceptional patients whose activities are severely impeded by cataract even when better vision is present in the other eye;
- Slightly younger people with physical or mental infirmities who are poor candidates for contact lenses;
- Elderly patients with disabling cataracts in both eyes, in which case an intraocular lens may be indicated in one eye, and perhaps in the second eye if the patient cannot function adequately on a uniocular basis. A reasonable time period should elapse before the second operation.
Patients with bilateral macular degeneration are also possible candidates for intraocular lenses if they have dense lens opacities which would be expected to reduce their vision to less than 20/200. And, elderly individuals who wear a contact lens for unilateral aphakia, but require cataract surgery in the second eye, may be considered for intraocular lens implantation.
Contraindications to implantation of intraocular lenses are as follows, except under very unusual circumstances:
Method of Cataract Extraction
- The patient's desire not to have an implant;
- Axial myopia greater than 7 diopters;
- A poor result from an implant or cataract extraction alone in the first eye;
- A patient with only one eye with potentially good vision;
- A relatively young patient;
- Individuals with senile macular choroidal degeneration without dense cataracts in both eyes;
- Endothelial corneal dystrophy;
- Proliferative diabetic retinopathy and possibly significant background retinopathy;
- Uncontrolled glaucoma;
- Previous retinal detachment in either eye;
- Congenital cataracts (particularly rubella cataracts) and cataracts associated with certain other ocular abnormalities (such as recurrent iritis, essential iris atrophy, or atopic dermatitis);
- Significant complications during the cataract extraction procedure.
The panel on Method of Cataract Extraction agreed that there are circumstances under which either intracapsular or extracapsular extraction would be equally suitable for cataract removal in conjunction with intraocular lens implantation. Under certain circumstances, however, there may be a definite procedure of choice. To determine the specific indications for each of these methods, the panel recommended controlled studies comparing intracapsular and extracapsular cataract extraction in association with intraocular lens implantation. The panel also called for studies to determine the optimum timing and technique for discussion of the posterior lens capsule and for research on methods for preserving transparency of the posterior lens capsule after extracapsular extraction. In addition, the panel suggested that the precise relationship between various methods of cataract extraction and subsequent cystoid macular edema warrants further study.
Retinal detachment occurs more frequently after cataract extraction, with or without intraocular lens implantation, than in the population as a whole. Evidence concerning which method of cataract extraction combined with lens implantation carries less risk of retinal detachment is inconclusive at this time. Therefore, further study of this question is also recommended.
Experience to Date With Intraocular Lens Implantation
The panel on Experience to Date with Intraocular Lens Implantation summarized and discussed clinical experiences with intraocular lens implantation which have been reported by many investigators. Excellent visual results have been reported for each of a variety of intraocular lens types, and some insight has been gained regarding possible advantages and risks associated with each. It was the consensus of this panel that the use of intraocular lenses is associated with a small but significant risk of additional complications beyond that of cataract surgery itself. Many of these may be transient or treatable medically and thus do not affect the visual result.
The incidence of severe corneal decompensation leading to significantly reduced visual acuity is reportedly greater following lens implantation, and it may require subsequent corneal transplantation. But this condition is not distinguishable from that which follows cataract extraction alone, and its occurrence has been reduced considerably in recent years by refinements in surgical techniques.
Without disparaging published information on the safety and visual advantages of intraocular lenses, some of the panel members believe that prospective clinical trials are required to refine knowledge of both the short-term and long-term advantages and risks of lens implantation. One of the questions that may be studied in a controlled trial is the relative risk of cystoid macular edema and/or of retinal detachment in extracapsular versus intracapsular surgery, in the presence or absence of a lens implant. The panel also recommended continued study of a large series of matched patients being followed in Miami because this will provide at least a five-year head start on any future prospective studies and important information on long-term visual results.
Special Considerations in Intraocular Implantation
The panel on Special Considerations in Intraocular Lens implantation discussed secondary implantation, bilateral implantation, and implantation in pediatric patients. The panel members emphasized that patients should be made aware of the additional risks involved in secondary and bilateral implantation. They concluded that there is presently a limited role for secondary implantation of intraocular lenses, and they recommended that secondary implantation be limited to older patients who cannot wear contact lenses or spectacles, specifically to persons who are incapacitated by unilateral aphakia and who have a particular personal or occupational need for binocular vision. Because late complications have occurred in the occasional patient with an intraocular lens, great caution is indicated in considering bilateral implantation. The panel agreed that contact lenses should be considered before deciding on bilateral implantation, and that bilateral implantation should not be used in young patients, except under unusual circumstances.
The panel also agreed that there were relatively few indications for lens implantation in children, although there is some feeling that an intraocular lens might be used in a child with a unilateral congenital cataract, but then only in a controlled clinical trial. Additional data from follow-up studies on children who currently have intraocular lenses should be made available and analyzed before there is any widespread use of IOLs in this age group. Well-controlled studies in pediatric eye centers are suggested for this special group of patients. Although preliminary data suggest a role for intraocular lenses in acquired pediatric cataracts, great caution should be exercised in this area. Generally, use of IOLs in these instances is not recommended, but a controlled clinical trial is indicated.
Alternatives to Intraocular Lenses
The panel on Alternatives to Intraocular Lenses considered the many difficulties inherent to the use of spectacles for correction of aphakia, although some recent improvements in spectacle lenses may have made them somewhat more acceptable both cosmetically and functionally. Panel members acknowledged both the advantages and disadvantages of conventional hard contact and soft contact lenses which are optically superior to spectacles but which may be difficult if not impossible for elderly persons and certain other individuals to handle. They also pointed out that over a period of years expected replacements for conventional or extended-wear contact lenses will cost more than the one-time cost of intraocular lens implantation.
Although extended-wear lenses are a potentially significant advance in the treatment of aphakia, not everyone can be or should be fitted with them. Although early data look promising, additional information is required on the long-term safety and efficacy of extended-wear lenses.
New surgical techniques to change the curvature of the cornea, for example keratophakia or keratomileusis, are also undergoing rapid development, and some studies are in progress. Advances in these surgical techniques are expected, as are improvements in contact lenses and intraocular lenses. Long-term follow-up data and additional research are required on all these alternatives to aphakic spectacles.
Studies Planned or in Progress
The Food and Drug Administration's (FDA) approach to monitoring the testing of intraocular lenses was determined in large part by a Congressional mandate which required regulation of the lenses and institution of an immediate study while not interfering with the availability of the lenses. In the FDA study, all intraocular lenses are treated as investigational devices. (The first release of data was made at the American Academy of Ophthalmology meeting in November 1979.)
Two prospective studies on intraocular lenses supported by the National Eye Institute were described. One is a five-year study of the effects of intraocular lenses on the corneal endothelium. In patients undergoing extracapsular extraction, contact lens wear will be compared to intraocular lens implantation. The other is a long-term randomized prospective study comparing intracapsular cataract extraction with contact lens wear to intracapsular extraction with intraocular lens implantation and extracapsular extraction with intraocular lens implantation. The principal comparisons will be of corneal effects, visual acuity, and complication rates.
A study of the economic implications of intraocular lens implantation is the first economic analysis conducted under the auspices of the National Center for Health Care Technology. An attempt will be made to determine whether IOL implantation costs more or less than various alternatives.
Several projects of the American Intraocular Lens Implant Society were briefly described. They include studies on: inflammation, sterilization procedures, lens coatings, and new lens materials; anterior chamber reactions; intraocular lenses compared to contact lenses in patients undergoing bilateral cataract extraction; and IOLs that have been removed. A quality assurance program is also being developed.
Two speakers, an ophthalmologist and a representative from the Health Research Group, strongly criticized the current status of intraocular lens implantation. Although both stated they were not opposed to the implantation of well-made lenses in appropriately selected patients, they raised the following concerns:
- Overuse of lenses in patients for whom they were not indicated.
- Adequacy of information given to the patient about the risks as compared to the benefits of the procedure.
- Inadequately trained lens implant surgeons.
- Need for reevaluation of Medicare reimbursement of IOL implantation.
- Marketing of lenses of inadequate quality as evidenced by numerous IOL recalls by the FDA.
- The purported failure of the FDA study to provide valid data on lens safety and efficacy.
- Adequacy of data on lens safety generally, and lack of data comparing the safety of lenses made by different manufacturers.
Representatives from the American Intraocular Lens Implant Society responded to the initial speakers and emphasized the following:
- Criteria for patient selection for IOLs have been available and widely disseminated for many years.
- Many problems with lenses were first identified by members of the Society; thus lens implant surgeons alerted the FDA to the advisability of some recalls.
- From a numerical standpoint, most recalled lenses were recalled because it was decided to exclude them from the FDA study, but they never became a problem for patients because they were never used.
- Meetings, courses, newsletters and telegrams are used to provide the latest information on IOL problems to practitioners.
- Training of surgeons and peer review are also concerns of the Society.
Another ophthalmologist in the audience emphasized his concern that guidelines for training of implant surgeons should be developed.
The last speaker, an ophthalmologist representing the Montana Foundation for Medical Care (a Professional Standards Review Organization), described how widely-agreed-upon criteria for intraocular lens implantation were effectively used in his state as a basis for peer review of implant surgeons. After observing a wide variation in indications and contraindications used by Montana lens implant surgeons, the PSRO established a committee for reviewing records of intraocular lens implantations. After the PSRO adopted and applied what they considered to be conservative criteria, practice patterns wee found to have changed to conform to the peer review standards. This, according to the speaker, has resulted in improved medical care in Montana.
Consensus Development Panel
Edward Maumenee, M.D., Chairman
Henry M. Clayman, M.D. Donald J. Doughman, M.D. Norman S. Jaffe, M.D. Herbert E. Kaufman, M.D. A. Edward Maumenee, M.D. Ronald E. Smith, M.D. Bradley R. Straatsma, M.D.
National Eye Institute
Office of Medical Applications of Research