9-1. What is presbyopia?

Presbyopia is the decrease in near vision most people experience when they reach their early 40’s.

9-2. What causes presbyopia?

Presbyopia is caused by a loss of the accommodation reflex, an automatic adjustment the eye makes for seeing up close (Figure 11).

Figure 11

9-3. Why is the accommodation reflex lost in the early 40’s?

The accommodation reflex is lost because we lose the ability to change the shape of the lens inside our eye. This lens is known as “the crystalline lens,” or simply, “the lens.”

9-4. What happens inside the eye to explain presbyopia?

As we age, the lens becomes thicker and stiffer. It loses its adjustability, and we begin to need reading glasses, to help us focus.

9-5. How rapidly does presbyopia progress?

Presbyopia progresses slowly over a period of about 20 years. Every few years, we must get slightly stronger reading glasses.

9-6. What do people notice when presbyopia occurs?

Most people with presbyopia notice difficulty reading, especially small print, as in the newspaper or telephone book. They may also have difficulty seeing their watch, sewing, or using a computer. When presbyopia begins, it helps to hold reading material a little further away. Eventually, the arms become “too short,” and most people prefer to use reading glasses.

9-7. Can presbyopia be treated with laser vision correction?

Yes, but there are some compromises. The most popular way to treat presbyopia with laser vision correction is through “monovision.” The reading eye is left slightly nearsighted. Usually, the “nondominant eye” becomes the reading eye. The dominant eye is corrected for distance.

9-8. When an eye is corrected for near vision, what happens to the distance vision?

There is a “yin” and “yang” between distance and near vision. In general, if the eye is corrected for near, it will not see clearly in the distance. The loss of clarity for distance depends on how much myopia remains in the reading eye. The more myopia that remains, the better the reading vision and the worse the distance vision.

9-9. What is the proper amount of myopia for the reading eye?

The proper amount of myopia for the reading eye depends on age and visual needs. Treatments range from 0.5 diopters to 2.50 diopters. For people who are in their mid to late 40’s and do a minimal amount of reading, a correction of 0.5 to 0.75 diopters is about right. For people in their 50’s who do a moderate amount of reading, corrections in the range of 1.00 to 1.50 diopters seem satisfactory. For those in their 60’s, and those who do a lot of close work, a correction of 2.50 diopters is about right.

9-10. How do I decide if monovision LASIK or PRK is right for me?

Many people who choose monovision LASIK have worn monovision contact lenses with good success. If they were successful with monovision contact lenses, they will probably be successful with monovision LASIK. Conversely, if they did not like the kind of vision they had with monovision contact lenses, they will probably not like monovision LASIK. If someone who has not worn monovision contact lenses is considering monovision LASIK, the best test to determine if they will like the result is to try a contact lens test. A reading contact lens should be worn in the nondominant eye for a week, if possible. A distance contact lens should be worn in the dominant eye. If there is uncertainty about which eye is dominant, and which is nondominant, the contact lenses can be switched.

9-11. What happens if I try monovision LASIK or PRK, and later decide I do not like it?

Monovision can usually be reversed. The procedure is similar to an enhancement, and it usually done at least 3 months after the initial treatment. For PRK, additional laser treatment is applied to the corneal surface. For LASIK, the flap is lifted and additional treatment is applied to the corneal bed.

9-12. If I am going to try monovision, which laser vision correction procedure should I have?

Monovision can be achieved with PRK, LASIK, or LASEK. All three procedures work equally well.

9-13. What is scleral relaxation surgery?

Scleral relaxation surgery is an operation for correcting presbyopia. Even though it has been in use for 10 years, relatively few cases have been performed. The operation is similar to radial keratotomy, in which corneal incisions are made with a sharp diamond knife. The cuts are placed at the junction of the sclera and the cornea (where the white part of the eye meets the colored part of the eye).

9-14. How well does scleral relaxation work?

Even the few ophthalmologists who perform scleral relaxation surgery admit that it only has a temporary effect. Recently, the procedure has been modified to create a more long-lasting effect. Titanium inserts, referred to as “barriers,” are inserted into the deepest part of the incision to prevent the cuts from healing. Since these barriers have a tendency to extrude, the cuts are sometimes sutured to prevent extrusion.

9-15. What can be expected for the future of scleral relaxation surgery?

No one can say for sure. To date, most ophthalmologists have not embraced scleral relaxation surgery. If future results show this procedure to be effective, safe and long lasting, it will, no doubt, gain acceptance among surgeons.

9-16. What is scleral expansion surgery?

Scleral expansion is another technique to correct presbyopia. Plastic “segments” are placed in the sclera in order to “tent up” the wall of the eye, and stretch the crystalline lens. This procedure tightens the zonules, the attachments between the inner wall of the eye and the lens. This tightening allows the ciliary muscle to function more efficiently, and restore the accommodation reflex.

9-17. How is scleral expansion surgery performed?

Incisions are made in the sclera, and segments are placed in the incisions, and sutured. The result is to increase the distance between the inner wall of the eye and the lens. This seems to restore, to some extent, the adjustability of the lens and allows near vision to improve.

9-18. Why does stretching the sclera improve near vision?

The theory, known as the Schachar theory, states that an aging lens moves closer to the inside wall of the eye as it thickens. This shorter distance causes laxity of the zonules, the fibers that attach the lens to the ciliary muscle. Because of this laxity, the ciliary muscle cannot function effectively. When the muscle contracts, the loose zonules cannot stretch the lens capsule to adjust the shape of the lens.

9-19. How well does scleral expansion surgery work?

The opinions are mixed, and relatively few procedures have been performed. Some surgeons who perform scleral expansion surgery are enthusiastic, while others are not. Some patients who have had the surgery are satisfied with the results. Others are not.

9-20. What are the complications of scleral expansion surgery?

Complications that have been reported include eye pain, especially during the first week after surgery. There may be persistent redness of the eye and dryness. Occasionally, the band or segment will come loose and extrude. In addition, the operation may not create the desired effect of improving near vision. Sometimes, near vision improves temporarily, but is lost in a matter of months. All of these complications occur less often as the surgeon gains experience with scleral expansion surgery.

9-21. Are there any sight-threatening complications of scleral expansion surgery?

A rare complication, which is associated with vision loss, is called “anterior segment ischemia.” It probably occurs when the circulation of blood to the front part of the eye is compromised. Anterior segment ischemia was more common with a continuous band was placed around the eye. Now that segments are used, anterior segment ischemia seems to be less common.

9-22. How difficult an operation is scleral expansion surgery to perform?

Scleral expansion surgery is more difficult to perform than LASIK or PRK. In recent years, surgical instruments, designed specifically for scleral expansion surgery, have made this procedure somewhat easier to perform.

9-23. What happens to distance vision after scleral expansion surgery?

Distance vision seems to be unaffected by scleral expansion surgery.

9-24. Is scleral expansion surgery performed in one eye, like monovision, or in both eyes?

Scleral expansion surgery is generally performed in both eyes. It does not create monovision in which one eye is used for distance and the other eye for near. The aim is that both distance and near vision are satisfactory without the use of glasses or contact lenses.

9-25. What does the future look like for scleral expansion surgery?

Like other types of refractive surgery, scleral expansion surgery is an evolving operation. As improvements are made, the operation changes. Equipment is created to make the operation easier to perform. As more procedures are done, more data becomes available, and more doctors share their results and suggestions for improving the procedure.

9-26. What are the alternatives to scleral expansion surgery for correcting presbyopia?

There are competing procedures for the correction of presbyopia, and at this time, it is not clear, which one, if any, will be the best. We are at an early stage in understanding how to correct presbyopia. Presently, monovision, scleral relaxation, and scleral expansion are being evaluated. A thermal procedure known as conductive keratoplasty, or CK, is also receiving some interest among patients and refractive surgeons. It will be interesting to see what direction presbyopia surgery takes in the future.

9-27. What is CK?

CK is an abbreviation for conductive keratoplasty, a “thermal” or heating procedure to correct farsightedness and presbyopia. The heat is delivered through a radiofrequency probe, a needle-like device which is used to apply a series of heat treatments deep in the cornea. The heat shrinks the corneal collagen and steepens the curvature of the cornea, reducing the amount of farsightedness, or presbyopia.

9-28. Who is a good candidate for CK?

Good candidates for CK are people who are farsighted. They should have between +0.75 to +3.00 diopters of farsightedness, and less than +0.75 diopters of astigmatism. Other good candidates are “emmetropic presbyopes.” These are people who need glasses for reading but not for distance.

9-29. How much CK treatment is required?

Eight to 24 thermal applications are used, depending upon how much correction is needed. One to three rings of treatment is made, each consisting of eight spots. The rings are centered on the pupil, guided by a special marker. The inner ring is 6 mm in diameter, the middle ring is 7 mm in diameter, and the outer ring is 8 mm in diameter.

9-30. Can CK be used to correct presbyopia?

Yes. The correction of presbyopia is one of the main uses for CK. It is usually performed in just one eye, the nondominant eye. The opposite eye remains untreated, since it is considered to be the “distance” eye.

9-31. Who is a good candidate for the correction of presbyopia by CK?

The ideal person is one who is over 40 years of age, has always had good distance vision without glasses or contact lenses, and dislikes having to wear reading glasses.

9-32. How does the doctor determine if someone is a candidate for CK?

The evaluation is similar to LASIK and other refractive surgery procedures. It is important to perform a refraction, corneal mapping, or topography, and to determine corneal thickness, by pachymetry. In addition, a “loose lens” test is done. In the loose lens test, a reading lens is held over the nondominant eye to see if the person likes the type of near and distance vision they will have with CK. Alternatively, a contact lens can be placed on the nondominant eye to simulate the effect of CK.

9-33. Does CK produce monovision?

It is accurate to say that CK produces a type of monovision. Since only one eye is corrected for near vision. The aim of CK is improve near vision without degrading distance vision.

9-34. How is it possible to produce good distance and near vision in the same eye?

It is not easy to produce good distance and near vision in the same eye in a person who is presbyopic. However, if just the right amount of treatment is given, it may be possible to achieve the desired effect. It is possible that CK produces a “multifocal” lens effect, that is, an eye that focuses at both distance and near. It is also possible that with just the right amount of treatment, CK can produce a compromise, in which reading vision is improved adequately with only a slight degradation of distance vision.

9-35. Does the effect of CK wear off?

Long-term studies on CK have not been done, since the procedure is relatively new. Most thermal procedures do lose their effect over time, so it would not be surprising if the effect of CK will wear off. In addition, the need for a stronger reading correction with time may make the CK correction inadequate.

9-36. Can CK be repeated if its effect wears off?

Again, there have not been any long-term studies of the effect of repeated CK treatments. It seems likely that CK can be repeated. How many repeat treatments can be done, and how much they would help improve near vision remains to be seen.

9-37. Are there any complications of CK?

CK appears to be a relatively safe procedure. A small number of people lose a line or two of distance vision, but this seems to be temporary. They recover this loss within a year. The main complication appears to be “surgically induced astigmatism,” which occurs in about 3% of treatments. Again, this seems to be temporary, and the astigmatism seems to go away within 1 to 2 years. But, during this 1- to 2-year period, vision may be blurred in the CK-treated eye.

9-38. What causes surgically induced astigmatism with CK?

It probably results from uneven healing, or uneven application of the radiofrequency probe. If more treatment is done on one side of the cornea than the other, astigmatism may occur. Uneven application of the radiofrequency probe is more likely to occur when a surgeon first begins to do CK. With experience, the CK marker is placed more accurately over the center of the pupil, and the probe is placed in an identical fashion each time. This results in more symmetric treatment so that the possibility of astigmatism is reduced.

9-39. Is there a treatment for the surgically induced astigmatism of CK?

Additional treatment applications can be made to correct the surgically induced astigmatism. The applications are made along the axis of the flat meridian of the cornea. In other words, an attempt is made to steepen the flatter curve, and “round out” the cornea.

9-40. Are there any other uses for CK?

CK can be used to correct small amounts of farsightedness, and CK can probably be used to correct many types of astigmatism. This could include astigmatism that occurs after cataract surgery, corneal transplantation, and after LASIK or PRK. So few cases of this type have been performed that it is difficult to say how accurate CK is in correcting these problems.