10-1. Why are contact lenses important in LASIK?

Contact lenses produce vision which is very much like the type of vision one can expect after LASIK. If a LASIK candidate has worn contact lenses, it is easy to explain what vision will be like after LASIK. For those who wear glasses, vision after LASIK may seem slightly different. Since contact lenses simulate LASIK vision, a “preview” with contact lenses may be useful.

10-2. In what way is vision with glasses different than vision with contact lenses or LASIK?

Glasses produce a slightly larger visual image than contact lenses or LASIK. This is because the lenses of glasses are positioned about 12 mm in front of the eye, rather than on the eye’s surface. This spacing produces a slight reduction in image size. Most people adjust easily to small changes in image size, but it may take a few days for them to feel completely comfortable with their new vision. In addition, glasses have a rim which interferes slightly with peripheral vision, whereas contact lenses (and LASIK), do not.

10-3. Should contact lenses be worn before having LASIK in order to simulate the type of vision I will experience after LASIK?

It is reasonable to wear contact lenses, even for a matter of months, to see what vision will be like after LASIK. This is especially true if there is some uncertainty about adjusting to the type of vision LASIK produces.

10-4. What is CLAPIKS?

CLAPIKS stands for “contact lens-associated, pharmacologically-induced kerato-steepening. It is usually performed by an optometrist. It is a recently described method for reducing hyperopia, or farsightedness. It may be useful after laser vision correction in certain people: Those who were nearsighted preoperatively and were overcorrected with laser treatment, and those who were farsighted preoperatively and were under-corrected with laser treatment. The problem these two groups have in common is they both have a small amount of farsightedness. CLAPIKS treatment requires fitting a steep, soft contact lens which changes the shape of the cornea slightly, making the cornea steeper. The lens is left in place 24 hours a day. In addition, an eyedrop, called Acular-LS, is used four times a day. Acular is a nonsteroidal anti-inflammatory drug, like ibuprofen, but it is said, by those who perform CLAPIKS, to alter the collagen component of the cornea, allowing it to be reshaped by a steep contact lens.

10-5. How long does CLAPIKS treatment take?

The treatment is carried out for 8 weeks, but the vision and the eye are checked once a week.

10-6. How well does CLAPIKS work?

It is claimed that CLAPIKS corrects a small amount of farsightedness, perhaps one diopter. There have not been a lot of studies about this technique, so much more data would be required to determine whether CLAPIKS really works.

10-7. How does Acular LS alter the shape of the cornea?

It is not clear that it does. It has been suggested that a steep, tight contact lens deprives the cornea of oxygen, allowing more penetration of the drug into the cornea. Somehow, Acular is thought to make the cornea thicker, thereby changing its focusing power.

10-8. Is CLAPIKS safe?

Not enough people have had CLAPIKS to judge whether or not it is safe. Some concern has been expressed about depriving the cornea of oxygen and trying to induce a metabolic change with unknown consequences.

10-9. How stable is CLAPIKS?

Again, there are not enough studies to say whether or not CLAPIKS creates a temporary or permanent change in the cornea. Some patients seem to have some effect lasting up to a year and half. Others appear not to respond at all to treatment.

10-10. Are there alternatives to CLAPIKS?

Yes. Most people who have a small amount of farsightedness after laser vision correction can be easily corrected by additional laser treatment. These “enhancements” are commonly done, extremely safe, and highly predictable.

10-11. What is an intraocular lens, and why is it important in laser vision correction?

An intraocular lens is a clear, synthetic lens that can be inserted into the eye. Intraocular lenses can be made from plastic (like polymethylmethacrylate), with silicone, or various polymers. Since the lenses contain focusing power, they can be used to correct nearsightedness or farsightedness. In this regard, they can sometimes correct the same vision problems that LASIK and PRK correct.

10-12. How are intraocular lenses placed in the eye?

Intraocular lenses have been used for many years in cataract surgery. A cataract is a cloudiness of the lens in the eye. With increasing age, the lens, known as “the crystalline lens,” or, just the “lens,” can become cloudy. When the lens is removed during cataract surgery, a synthetic lens, with the proper focusing power, is placed precisely where the cataractous lens was removed.

10-13. Can intraocular lenses be used in nearsighted and farsighted people?

Yes. They can be used whether or not a cataract is present. If cataract surgery is performed, the ophthalmologist can determine the exact power of the intraocular lens needed to reduce or eliminate nearsightedness or farsightedness. Ultrasound of the eye and corneal measurements are used to calculate the lens power. When the cataract is removed at surgery, the synthetic lens is inserted in its place. An intraocular lens can also be used to change the focusing power of the eye, even when no cataract is present.

10-14. If a cataract is not removed, and the natural lens is left in the eye, where is the intraocular lens placed?

If a cataract is not removed, the intraocular lens is placed in front of the natural lens. It can be placed either in front of the iris (the colored part of the eye), or behind it. In either case, the intraocular lens must be placed very carefully so as not to damage the natural lens or the other delicate structures within the eye.

10-15. What is the Artisan Lens?

The Artisan Lens is an intraocular that can be placed in the eye to correct nearsightedness or farsightedness. It is oval in shape, with blunted ends, and it has footplates at either end that are reminiscent of crab claws. It can be considered an alternative to LASIK or PRK.

10-16. How much nearsightedness or farsightedness does the Artisan Lens correct?

The Artisan Lens can correct between 5 and 20 diopters of nearsightedness, and between 3 and 12 diopters of farsightedness.

10-17. How is the Artisan Lens placed in the eye?

It is inserted through an incision, similar to a cataract incision, at the periphery of the cornea. It is stabilized in front of the natural lens and iris by fitting its claw-like footplates in the angle between the cornea and the iris.

10-18. How good is the vision produced by the Artisan Lens?

In a recent study, 90% of people who received the Artisan Lens achieved visual acuity of 20/40 or better. This is somewhat poorer than the results that might be expected with LASIK. One problem with the Artisan Lens, and other intraocular lenses, is that they do not correct astigmatism. LASIK, of course, can correct astigmatism. On the other hand, intraocular lenses can correct high amounts of nearsightedness and farsightedness which may be beyond the limits of the LASIK and PRK.

10-19. Are there complications of the Artisan Lens?

Yes. Like all eye surgery, intraocular lenses can be associated with complications. These include bleeding and infection. Since the intraocular lens is placed close to the crystalline lens, the surgeon must be very skillful to avoid damaging the lens.

10-20. What is the result of contact between the phakic intraocular lens and the other structures within the eye?

Contact between the intraocular lens and the natural lens can cause a cataract to form. Contact between the intraocular lens and the iris can cause inflammation. Contact between the intraocular lens and the cornea can cause loss of the “endothelium,” the inner layer of corneal cells, leading to swelling and cloudiness of the cornea.

10-21. Are there any other problems with phakic intraocular lenses?

There is concern about pupil size. The pupil must be smaller than the optical portion of the intraocular lens, so phakic intraocular lenses are not well suited to people with large pupils. In addition, there is concern about fitting the lens into a farsighted eye. The space between the iris and the cornea tends to be narrow in a farsighted eye, and this makes the fit of an intraocular lens somewhat tight, and the surgical procedure somewhat more difficult.

10-22. What is a “posterior chamber phakic intraocular lens?”

A posterior chamber phakic intraocular lens is one that is placed in the posterior chamber, the space behind the iris and in front of the natural lens. Such lenses are synthetic, and made from plastic or silicone. They have focusing power, which allows them to correct nearsightedness or farsightedness. They cannot correct astigmatism.

10-23. What is the “STAAR Surgical implantable collamer lens (ICL)?”

The “STAAR ICL” is one of the more popular posterior chamber phakic intraocular lenses, made of collamer, a soft polymer material. It has been used mainly in Europe and South America, and has had limited use in the United States. It can correct between 3 and 20 diopters of nearsightedness. It requires two “iridotomies,” small holes placed in the iris to allow circulation of fluid within the eye. The laser iridotomies are made at least one week prior to lens implantation.

10-24. What is the vision like with the STAAR Surgical ICL?

In a recent study, 92% of people receiving the STAAR Surgical Intraocular contact lens achieved vision of 20/40 or better, and 59% were 20/20 or better. Disturbance of contrast sensitivity and creation of higher-order optical aberrations were minimal.

10-25. Are there other types of phakic intraocular lenses?

Yes. Other types exist. Medennium Corporation produces a silicone lens, which corrects nearsightedness and farsightedness. It is being studied in clinical trials in the United States. No doubt, we will be seeing more entries in the phakic intraocular lens field as different technologies compete in an effort to correct refractive errors of the eye.

10-26. What makes the insertion of phakic intraocular lenses difficult?

Many of the problems with phakic intraocular lenses have to do with the simple fact that there is not a lot of room in the eye for an extra lens. In addition, the delicate structures of the eye can be damaged by the very act of inserting an intraocular lens. It is true that ophthalmologists have a lot of experience implanting intraocular lenses in the eye during cataract surgery. But cataract surgery techniques have been honed over many decades and most ophthalmologists are skilled with the technique. While insertion of phakic intraocular lenses has many similarities to cataract surgery, it has some important differences that make it tricky.

10-27. What are the complications of phakic intraocular lenses?

Many complications of phakic intraocular lenses can occur. Two of the most common are cataract formation and glaucoma. Cataracts occur because of the close proximity of the phakic intraocular lens to the natural lens. The natural lens can be damaged during lens insertion. But even if the lens insertion is perfect, the phakic intraocular lens can rub against the natural lens and produce a cataract. Glaucoma can occur because the phakic intraocular lens can “crowd” the space where fluid filters out of the eye, leading to a build up of pressure. In addition, there may be some long-term effect of phakic intraocular lenses on the cornea. It is possible that corneal endothelial cells, the cells that form a single layer on the inner side of the cornea, could be rubbed off over time, leading to corneal decompensation and swelling. Corneal swelling often requires corneal transplant surgery.

10-28. What is bioptics, and can it be used to correct vision?

Bioptics is a combination of laser vision correction and intraocular lenses. This technique can be used to correct high amounts of nearsightedness or farsightedness. It is especially useful when laser vision correction, or intraocular lenses, cannot achieve a full correction of the refractive error. In such situations, the combination of techniques may allow full correction of nearsightedness, farsightedness, and even astigmatism.

10-29. How does bioptics work?

Let us say that someone has a large amount of nearsightedness and astigmatism. An example would be 15.00 diopters of nearsightedness and 3 diopters of astigmatism. Let us also assume the cornea is too thin to perform this large correction with LASIK. In this situation, an intraocular lens could be used to correct 12 diopters of nearsightedness, and a modest LASIK could be performed to correct the remaining 3 diopters of nearsightedness and 3 diopters of astigmatism. Thus, a full correction could be achieved.

10-30. What are clear lens extractions?

A clear lens extraction is removal of the crystalline lens of the eye. Since the lens accounts for about 10 diopters of power, clear lens extraction can be used to correct roughly 10 diopters of nearsightedness.

10-31. Why isn’t clear lens extraction performed routinely?

Clear lens extraction is not performed routinely because it is rare for someone to have just the right amount of nearsightedness that would be corrected by clear lens extraction. In addition, most ophthalmologists have strong reservations about removing a clear, natural lens from the eye when there is no cataract. Further, it is believed that problems, such as retinal detachments, are potential complications with clear lens extraction.

10-32. Can an intraocular lens be inserted after a clear lens extraction?

Yes. Intraocular lenses can be inserted after a clear lens extraction. This could allow a precise correction of nearsightedness or farsightedness, but it would not eliminate the potential for retina complications, or get around the natural reluctance of ophthalmologists to remove clear, natural lenses?

10-33. What are “adjustable” intraocular lenses?

Adjustable intraocular lenses, also known as “light adjustable lenses,” have a silicone matrix with embedded silicone subunits, known as “macromers.” The power of the lens can be “adjusted” by shining an ultraviolet light on different areas of the lens. This causes the macromers to “polymerize,” which in turn results in a precise change in the shape of the lens caused by fluid absorption. When the desired power is obtained, the entire lens is irradiated with ultraviolet light to “lock in” the power correction.

10-34. How much can the power of adjustable intraocular lenses be adjusted?

There is a 5 diopter range. So, if the power of the lens implant needs to be increased or decreased up to 5 diopters, it would be possible.

10-35. Can astigmatism be corrected with adjustable intraocular lenses?

Yes. Astigmatism is corrected by focusing the ultraviolet light along a specific meridian.

10-36. Can wavefront corrections be incorporated into the adjustable intraocular lens?

Yes. Because one can adjust the light adjustable lens with a spatial resolution of less than one micron, these silicone lenses enable wavefront-based adjustments.

10-37. Is the adjustable intraocular lens on the market?

Not at this time. In fact, adjustable intraocular lenses have been used in animals, but not in humans. It may be many years before this technology is proven safe and effective for human use.

10-38. Could adjustable intraocular lenses be used one day to correct refractive errors?

It is possible that adjustable intraocular lenses could one day be useful to correct nearsightedness, farsightedness, or astigmatism. But, there are many unanswered questions about this interesting technology, such as safety, effectiveness, and stability. Also, there are many other technologies which are competing for the same market. Many of these technologies do not require placing material inside the eye. On the other hand, adjustable intraocular lenses may find their main use in cataract surgery where synthetic materials need to be placed inside the eye.

10-39. What are “piggyback” intraocular lenses?

“Piggybacking” is the term used when two intraocular lenses are placed in the eye to correct refractive errors. There are two basic types of piggyback intraocular lenses. “Primary” piggyback lenses are used to correct high amounts of nearsightedness or farsightedness, in situations where one lens is not powerful enough to correct the entire refractive error. “Secondary” piggyback intraocular lenses are used in situations where an existing lens implant has the wrong power. In such cases, a piggyback lens placed in front of the existing lens can correct the residual refractive error.

10-40. Are piggyback intraocular lenses safe?

Intraocular lenses must be placed quite precisely, either behind the iris, or in front of it. It takes a great deal of skill to place one intraocular lens correctly. Placing two intraocular lenses is substantially more difficult. Not only is the space extremely tight, but lens designs are only in the early stages of development when compared with standard intraocular lenses used in cataract surgery. Piggyback intraocular lenses are used by very few ophthalmologists and even then, only in unusual circumstances.

10-41. What happens when people with laser vision correction need cataract surgery?

Almost everyone develops cataracts if they live long enough. Most people who have had laser vision correction will, one day, require cataract surgery. Since PRK and LASIK have been available for nearly 15 years, many people who have had laser vision correction have developed cataracts and undergone cataract surgery. The calculation of the intraocular lens power is based on the length of the eye and the curvature of the cornea. The length of the eye can be measured precisely with standard ultrasonic techniques. The corneal curvature is changed by LASIK, and PRK. Both techniques cause flattening of the cornea. This presented a challenge for intraocular lens power calculations. Now that thousands of cataract surgeries have been performed after laser vision correction, cataract surgeons usually understand how to factor laser vision correction into the power calculations for intraocular lenses.

10-42. What if a LASIK or PRK patient has cataract surgery and ends up nearsighted or farsighted?

The lens implant can be exchanged for one with the correct power. Alternatively, a LASIK enhancement can be performed.

10-43. What is refractive lens exchange?

Refractive lens exchange is a procedure in which lens material is removed form the crystalline lens inside the eye, and replaced by a clear, synthetic, lens implant having the precise power to correct vision. A form of this procedure was known in the past as “clear lensectomy.” The term “refractive lens exchange” seems to be a bit more accurate. The procedure is similar to a cataract operation. Typically, no cataract is present, so it is the clear lens that is removed.

10-44. What kind of synthetic lens is used to replace the natural lens?

A variety of synthetic materials can be used to replace the natural lens of the eye. They may be silicone or synthetic polymers. A lens of a particular power can be selected so that it corrects distance vision. Some lens implants act like a bifocal and correct both distance and near vision.

10-45. Are there any complications of refractive lens exchange?

Complications may occur after refractive lens exchange, and the most serious one is retinal detachment. The incidence of retinal detachment is 2% within four years, and 8% within seven years. This would seem to be an unacceptably high incidence of retinal detachment. This figure may decline with improvements in lens material and technique. But, if it does not, refractive lens exchange may not have much of a future. Other complications include undercorrection, overcorrection, presbyopia, posterior capsule opacity, and astigmatism.