There are still many people who are wearing PMMA lenses. Some patients wear them without problems, while others only think they’re having no problems. I was curious about practitioners’ opinions on whether or not to refit these patients into state-of-the-art gas-permeable (GP) materials. So, I decided to survey my colleagues and received input from Christine Sindt, O.D., F.A.A.O., of the University of Iowa, and Arizona private practitioners Robert Maynard, O.D., Charles Edmonds, O.D., and Ken Johnson, O.D.

Ideal Candidates
The four doctors agreed that the treatment choice would depend on answers to the following questions:

• How long has the patient been out of lenses (if at all)?
• Is the correction stable?
• How long are the lenses worn each day?
• Has the patient been under a certain doctor’s care for several years, or is he or she new to the practice?
• Has the patient had problems in the past, whether or not the patient was aware of them?

The interviewees also agreed that if the patient’s refraction is stable, topography shows no abnormalities and the cornea appears healthy, refitting the patient with a new PMMA lens is a good option. When these criteria are met, this shift is expected to cause the fewest problems for the patient. But, these patients should be advised that the time may come when there is compromise to the health or optics of the cornea, and once that happens, it will be necessary to discontinue PMMA lens wear. To ensure that the eye is kept out of jeopardy, these patients must be seen on a semi-annual basis.

Dr. Edmonds evaluates the endothelial cell layer for polymegethism and pleomorphism. If there are problems with a compromised endothelium and topography shows corneal warpage, he first refits the patient temporarily with a silicone hydrogel lens until the cornea stabilizes, at which point he refits with a higher-Dk GP lens.

Another option is for the patient to be kept out of all contact lenses until the cornea stabilizes. But, this likely creates significant hardship for the patient. Long-time PMMA wearers seldom have a pair of spectacles that will allow them to see well enough to work, and if a new correction is provided, it will most likely change within a few days. For this reason, it is best to refit the patient either as Dr. Edmonds suggests with a silicone hydrogel then a GP lens, or directly into a GP lens.

From PMMA to GP
When refitting into GP lenses, the recommendation is to duplicate the fit of the PMMA lens as closely as possible, using a low- to medium-Dk material. The patient should be advised that the cornea will change and to expect that additional lenses may be needed in order to fully rehabilitate the cornea. As the patient adapts to the new material, the fit can be fine-tuned in order to achieve a more ideal lens-to-cornea relationship.

The Comfort Issue
Long-term PMMA wearers frequently have problems with the comfort of GP lenses, as well as dryness. Also, GP lenses may not be as durable as PMMA lenses. The increased oxygen supply to the cornea will enhance corneal sensitivity that may have been lost due to a lack of oxygen availability through the PMMA material. Patients may consider this change a negative response to the new lenses, so they need to be counseled ahead of time about this potential occurrence and the fact that it’s in their best interest. A good way to deal with this is to explain that corneal sensitivity is necessary to protect the eye from foreign bodies and early signs of corneal distress, whether from injury or disease.

Patients with polymegethism and pleomorphism should be refit into GP lenses. An altered endothelium is a tell-tale sign that  there is a problem or soon will be. With that said, there are still people who successfully wear PMMA lenses, and there may be no need to change them to the newer GP materials.

When there are problems with distorted optics or compromise to any layer of the cornea, it will be necessary to refit the patient with a GP lens. This should be done with caution, but without fear. Careful counseling and instruction to the patient will make this transition easier for both the patient and the practitioner.