|Year : 1989 | Volume
| Issue : 2 | Page : 86-88
Secondary IOL versus Epi-K
David B Davis II
Medical Surgical Eye Center, 1237 B Street, Hayward, California 94541, USA
David B Davis II
Medical Surgical Eye Center, 1237 B Street, Hayward, California 94541
|How to cite this article:|
Davis II DB. Secondary IOL versus Epi-K. Indian J Ophthalmol 1989;37:86-8
Among the choices available for the treatment of aphakia are secondary intraocular lens implants, epikeratoplasty, and keratomelcusis. Contact lenses and glasses have been the time honoured and proven treatment for aphakia.
Hard contact lenses give outstanding optical quality and can be tolerated by a moderate percentage of aphakics successfully. We are all familiar with the pros and cons of hard contact lens usage, the advantages and disadvantages, and the indications and contra-indications. When extended wear soft contact lenses were developed we thought we had an ideal modality for the treatment of aphakia. Although these lenses did not give us quite the same quality of vision as a hard contact lens, it did afford the elderly a comfortable and easy wearing of contact lenses without the need for frequent removal and insertion. Many elderly patients are unable to insert and remove a contact lens because of other physical problems.
However, over the past number of years we have seen an increasing number of severe ocular infections which have destroyed not only vision, but the eye, in extended wear contact lens wearers. These have occurred most particularly in the elderly and debilitated patients, who cannot take the lens out and clean it adequately. Therefore many institutions and physicians in the United States have ceased dispensing of extended wear contact lenses. Their use is now limited to daily wear or at the most, one week.
Although the disposable soft contact lens will soon be available in aphakic powers we still have the dilemma of insertion and removal. In addition, these lenses are more expensive than the standard contacts.
Corneal inlays are in the early stages of study and are presently fraught with many problems. However, when and if these problems are solved the inlay could prove to be an excellent future modality for the treatment of aphakia. Predictability of refraction and quality of vision should both be good. The procedure is non-invasive and should not be too difficult to learn and perform.
Keratomileusis on the other hand is a very difficult procedure for the average ophthalmologist to perform, requires expensive equipment and extensive training and unless great strides are made to reduce all of the above it will probably never be a primary treatment for aphakia.
So we are left with secondary intraocular lens implantation and epikeratoplasty which we will discuss in more detail.
The advantages of a secondary intraocular lens include the following:
- A high degree of predictability of post-op refraction. With proper keratometric readings and ultrasonic axial length determinations we can predict within plus or minus 1 diopter in 90 % of our cases and are rarely more than 2 diopters in error.
- Secondary intraocular lenses give excellent optical properties and if the patient has capable retinal function, then visual acuity can be as good as 20/15
- Quick visual recovery. In a properly performed uncomplicated secondary intraocular lens implantation the patients will have useful vision by the next day and usually good visual acuity within three to five days. Because the incision size is usually no greater than 6.5mm physical rehabilitation is quick and most can be back to full activity within two to three weeks.
- Intraocular lens implantation is a familiar procedure that most of us have performed and are experienced in.
- The cost of secondary lens implantation is not high. Each year intraocular lens prices become lower and this year is no exception. In the United States, the Federal Government is planning to put the cost of intraocular lenses at $ 200, down by almost 100 % of what lenses cost in late 1987. Lenses can be produced for third world countries considerably cheaper and eventually should be available in the $ 30 to $ 40 range.
- Most hospitals and eye centres keep a reasonable quantity of intraocular lens sizes and powers in stock so that should the lens be dropped on the floor prior to insertion a replacement lens is usually available.
What are the disadvantages of a secondary intraocular lens:
- It is an invasive procedure which requires exposure to the possibility of endophthalmitis. Although endophthalmitis in the U.S. occurs in about 1 in 2,000 cases, it can be totally disasterous.
- Corneal endothelial decompensation can occur if there is serious lens endothelial touch during insertion or if the intraocular lens is inserted in a patient with corneal dystrophy. For safety Viscoclastic products should be used in adequate quantity to protect the endothelium during insertion. These products can be expensive. Doctor's Fechner in Germany and Freeman in the United States have been using 2 % Methylcellulose as a viscoelastic for the past several years and this appears to be working quite well. This product can be obtained for about $ 10 per 2cc syringe and is considerably cheaper than Healon or Viscoat.
- Cystoid macular edema can occur especially if there is vitreous manipulation during the case or if the patient has had pre- existing CME at any time. CME can also occur in what appears to be a totally uncomplicated anterior chamber lens insertion without any post-operative complications.
- Age. There is still the question of insertion of an intraocular lens in children, infants, and young adults and is still under investigation. At the present time most physicians in the U.S. feel that the insertion of a posterior chamber intraocular lens within the capsular bag can be performed safely at almost any age. However, when the lens must be inserted in the ciliary sulcus or the anterior chamber there is less certainty of the long term effects. If the anterior chamber lens is not perfectly sized and shows any movement in the eye then corneal decompensation or the UGH syndrome can occur. In addition, many anterior chamber lenses which looked good at the onset have shown to be disasterous in the long run. These include the Stable-flex, Leiske, and other lenses. So any anterior chamber lens utilized in a young adult should definitely be one with a long history of success such as the Kelman Multiflex or Omnifit.
A few cased of the UGH syndrome have been reported with posterior chamber lenses inserted in the ciliary sulcus. Although this is not common it is a consideration when lenses are implanted in a young individual.
What are the contra-indications for the insertion of a secondary intraocular lens: (1) & (2) & (3)
A low endothelial cell count and age. How low should it be before one contra-indicates the use of an anterior chamber intraocular lens? This is not an easy question to answer. It depends upon many factors including the age of the patient and the overall status of the cornea. If a posterior chamber lens can be inserted we are probably safer in inserting a secondary implant in younger patients and even in those with lower endothelial cell counts. If there are early signs of corneal decompensation such as increase of the corneal thickness in the early morning as compared to the afternoon, then it is likely that any invasive surgical procedure will most likely cause the cornea to decompensate.
In a young patient in whom an anterior chamber lens is to be inserted I would be hesitant with an endothelial count of less than 1,000. You must remember, however, that these are general figures and not absolute numbers. How young a patient is considered "too young" for secondary IOL? I would not put a secondary lens in anyone under the age of 25, and probably not an A.C. IOL in age less than 30. However, a patient's visual needs must be considered.
4. Previous history of CME, or CME present. Opening the eye in these cases is like opening pandora's box and there is a high percentage that the CME will get worse or reoccur.
5. Vitreous in the anterior chamber. Whenever the vitreous is disturbed or a vitrectomy has to be performed there is at least a 5 % chance of retinal detachment and even higher (10-15 %) in the axial myope. This has to be considered against the patient's optical needs and would be a relative contra-indication. In these cases I think it is extremely important to discuss the potential complications and risks of CME and retinal detachment with the patient's thoroughy. If the vitreous is disturbed, meticulous attention to the detail of preventing any vitreo-retinal traction by not leaving any vitreous strands to the wound or IOL footplates is important.
6. One eyed patients. If the posterior capsule is intact, a good endothelial count present (over 1500 cells/m 2 ) and the patient is a mature adult (meaning over the age of 40 - 45) insertion of a posterior chamber lens may be reasonable. One eyed patients will certainly do better optically with an intraocular lens than with other methods of visual correction. If the eye is not a "good risk" eye I would be very hesitant about inserting an intraocular lens. I might consider an A.C.IOL insertion in a one eyed individual with a fibrotic intact vitreous face well posterior to the pupillary margin, with no evidence of peripheral anterior synechia, glaucoma, or endothelial disease, and age over 40. If this patient's optical needs were such that a secondary IOL was necessary I would inform him, that at the time of surgery should we encounter any difficulty such as a firm eye, etc. the case would be aborted immediately. I would be very hesitant about inserting anterior chamber intraocular lenses in one eyed patients, and have not done so to date.
7. A previous history of complicated cataract surgery in which there is any abnormal anterior segment anatomy is always a concern when considering an intraocular lens. These patients will more likely have problems at the time of their secondary surgery or post-operatively later.
8. Glaucoma bleb. Any invasive procedure of the eye in a patient with a glaucoma bleb (especially with non-intact post. capsule) runs at least a 20 - 30 % risk of closing off the bleb at some later date and destroying the glaucoma control.
9. Uncontrolled glaucoma. An aphakic patient on full medical therapy for glaucoma with poor or inadequate control certainly waves the red flag. Again if the posterior capsule is intact it is conceivable that combined trabeculectomy-posterior chamber intraocular lens could be utilized.
10. Retinal pathology. We have already mentioned CME and histories of retinal detachement. Proliferative diabetic retinopathy would certainly be a contra-indication. Insulin dependant diabetics who have not had PRP should not have an anterior chamber intraocular lens inserted. If PRP has been performed and the retina is in a totally "quiescent" stage and all other factors make the eye a "good risk" then one should balance the patient's optical needs against future potential risks.
Epikeratoplasty: What are the advantages of Epi-K.
- This is a non-invasive extraocular procedure with less chance of infection. It is less likely to result in an exacerbation of retinal pathology such as CME or retinal detachments.
- It is reversable and repeatable in most cases although we are now finding some cases that the reversability is not as good as we originally thought.
- The vision is good, but not excellent and certainly does not give the optical quality of a contact lens or an intraocular lens.
- It is useful in cases where there is a high probability of some intraocular surgical complication on patients with significant anterior segment anatomical abnormalities: i.e; Vitreous in the anterior chamber, peripheral anterior synechia, corneal endothelial dystrophy, or abnormal iris.
- It is probably useful, and safer, than secondary IOL in a patient with macular degeneration whose potential for visual acuity is less than 20/60. The need for high quality vision in these patients is not as great as those with normal maculas.
- Young patient. Since this is non-invasive and reversible for the most part, aphakic children and young adults may be the greatest indication for Epi-K.
What are the disadvantages of epikeratoplasty:
- There is a prolonged visual recovery period. In some cases it takes up to six to eight months before final visual acuity is achieved.
- It is not as easy to do as a secondary intraocular lens implant. It requires meticulous attention to detail in suture technique. Improper suturing can lead to irregular or induced astigmatism, and to peripheral corneal neovascularization necessitating the need for removal of sutures at an earlier stage.
- Epithelialization may be a problem particularly ii. those with a compromised ocular surface. One of our biggest problems in the healing process has been proper reepithelialization of the cornea.
- One must be prepared to spend a great deal of time with patients post-operatively for suture adjustment and more training of the surgeon is definitely needed for this procedure.
- Predictability of power, although improving, is still not nearly as good as that with secondary intraocular lenses. Plus or minus 2 diopters within the predicted result is considered a good result. Some cases have shown greater than 6 diopters error.
- The freeze dried lenticles which are available are not as good optically as those made fresh when one has his own lathe. However, a lathe is very expensive. Also if you drop the lenticle prior to insertion and do not have a backup, then the case has to be cancelled.
- The lenticles themselves are not cheap; in the United States they run out about $ 700. An intraocular lens costs less.
What are the contra-indications for epikeratophakia:
- Perhaps the most important contra-indication is a poor ocular surface. Those patients with dry eyes, lagophtalmos, poor lid closure, any tear layer disfunction such as a glaucoma bleb or pterygium, and chronic blepharitis are poor candidates for epi-K. Re-epithelialization is a serious problem in these eyes.
- It is contra-indicated when a patient needs good optical quality vision such as a pilot. It is highly unlikely that he is going to get sharp 20/20 vision with epikeratophakia. Most epi-K give one to one and half lines less than that of a hard contact lens or intraocular lens.
So, what are the general recommendations to be made:
Intraocular lenses should be considered in cases where quick visual recovery and 20/20 vision is needed. It is particularly useful if originally an ECCE with an intact capsule or an ICCE without vitreous in the anterior chamber, has been performed. It should be used with caution (or not at all) if there is a very low endothelial cell count or significant anterior segment abnormalities including previous surgery, trauma, or glaucoma, and in a very young patient.
Epikeratoplasty is particularily useful for the contact lens intolerant long standing uncorrected monocular aphake who has any of the following: low endothelial cell count, vitreous in the anterior chamber with a previous history of CME, retinal pathology, severe glaucoma with or without filter (if a posterior chamber lens cannot be used) or the patient does not wish for intraocular surgery.
Epikeratoplasty should strongly be considered in the pediatric age group as an alternative to the intraocular lens