Prescribing contact lenses for presbyopic patients involves compromise

Issue: May 1998

NEW YORK - The perfect bifocal contact lens continues to remain a long-sought-after goal. Each lens involves one sort of compromise or another, depending on a patient's occupation, lifestyle and hobbies. Once these factors are considered, satisfactory lenses can be chosen.

Monovision works for many

Monovision appears to be the most popular way to provide bifocal vision for presbyopic patients, said Wayne W. Wood, OD, in private practice in Jacksonville, Fla.

"Seventy-five percent of our patients do very well with monovision," and about half of those do extremely well, Dr. Wood asserted. In 25% of patients, monovision, for reasons that are unclear, fails.

Determining if monovision is the appropriate choice is a quick, straightforward procedure, he said.

"You can almost always tell in the early stages if someone is a good candidate by the initial reaction. If the patient falls out of the chair after the first few minutes of wearing trial monovision lenses or is obviously displeased after the first 15 or 20 minutes, that patient is not a good candidate," Dr. Wood explained.

But if the patient likes the lenses after 20 or 30 minutes, then you can be pretty sure he or she falls into the 75% of patients for whom the lenses will be satisfactory. However, certain occupations can present challenges to monovision, Dr. Wood noted.

"Truck drivers who have a need for distance vision or jewelers who need very fine, close-up depth perception are two areas where monovision is not impossible, but it's just a little more difficult to work," he said.

In a presbyopic patient who wants contact lenses, "a gas-permeable bifocal is still our first choice. But if the patient is not a candidate for rigid lenses, either due to sensitivity or just my evaluation of his or her circumstances, then we'll fit him or her with monovision soft lenses," Dr. Wood said.

Soft bifocal lenses

Soft bifocal contact lenses for presbyopia are most commonly used for simultaneous vision, said Craig Norman, FCLSA, director of the contact lens section in the ophthalmology department at the South Bend Clinic in South Bend, Ind.

"There are certain limitations and concerns, however, that one needs to be aware of," he said.

These systems are pupil dependent, he noted. "Depending on where the lens positions on the eye and how reactive or nonreactive the pupil is, the patient may or may not acquire the proper vision through that system."

In fitting these lenses, the practitioner must be concerned about the age of the patient.

"The older a patient gets, the less reactive the pupils are to light and the smaller they are in size. Another concern is that most of the lens system must center over the pupil directly. In the majority of the lenses marketed, the reading component is in the center of the lens. When the patient looks down to read, he or she has to move with the eye exactly so the reading optics stay in front of the pupil at all times," Mr. Norman said.

One difficulty in fitting these lenses is that a patient's pupil is not geometrically centered. "Soft lenses, because of their largeness, tend to be centered directly over the cornea. Often the optics are not centered over the visual system the way they should be," Mr. Norman said.

Appropriate fitting, consequently, depends on the individual patient's visual system, such as how closely the individual's eye matches the optics of the lens, Mr. Norman explained.

"For instance, while there are many simultaneous vision lenses, this type of lens system works well only in those patients where there pupil is aligned closely with the geometric center of the cornea," he said.

Limits to reading prescription

Another concern is the limited amount of reading prescription that can be put into the lens. "Often, these lenses are called nominal addition lenses - just a slight amount of reading correction is in the lens," Mr. Norman said.

For patients whose pupil is not in the center of the cornea, the result is a decrease in acuity. "The patient either lives with diminished vision at some level or he or she is put into other lens modalities, such as alternating vision or monovision systems."

Simultaneous vision soft lenses are the least successful contact system for presbyopia, Mr. Norman said. Simultaneous vision in gas-permeable lenses is different. The lenses can be custom designed and can change position during the blink cycle. "So the patient can use different reading and distance components," he said.

The ideal patient

For certain patients, translating bifocal rigid gas permeable lenses are "wonderful," said John L. Schachet, OD,in private practice in Englewood, Colo. "The ideal patient is the housewife who is not going to be spending much time on the computer. You have only limited range of vision for computer distances. You're either seeing long range or short range, but not well in the mid-range," Dr. Schachet said.

The lenses would be satisfactory for attorneys, accountants and real estate agents - people who spend a lot of time reading documents close-up. If you work on a computer or at any occupation requiring intermediate range of vision, these lenses are not satisfactory, he said.

Dr. Schachet noted that these lenses are more difficult to get accustomed to than a standard rigid gas-permeable lens.

"One of the principles of the lens is that it tends to ride on the lower lid. When it does that, it creates more of an awareness until the patient adjusts to the lens," he said.

Max Hettler, OD,in private practice in Lorain, Ohio, noted, as have other practitioners, there is no single lens that solves all presbyopic problems.

"You can't fit just one bifocal contact lens to everybody, just as you can't have a shoe store and have only size 10 shoes. You must have several different types available. What works for one patient may not work for another. You put a pair of diagnostic lenses on and you don't get the results for one, often you put a different manufacturer's lens on and you get the results," he said.

For your information:

Wayne W. Wood, OD, can be reached at 1500 Riverside Ave., Jacksonville, FL 32204; (904) 356-7102; fax: (904) 356-7947. Dr. Wood has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

John L. Schachet, OD, an be reached at 8586 E. Arapahoe, Suite 100, Englewood, CO 80112; (303) 771-4221; fax: (303) 721-7759. Dr. Schachet has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Craig Norman, FCLSA, can be reached at the South Bend Clinic, 211 Eddy St., South Bend, IN 46617; (219) 237-9336; fax: (219) 237-9329. Mr. Norman did not disclose if he has a direct financial interest in the products mentioned in this article or if he is a paid consultant for any companies mentioned.

Max Hettler, OD, can be reached at 209 5th St., Lorain, OH 44052; (440) 245-6406. Dr. Hettler has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.