Long-term Effects of Contact Lens Wear
BY JOE B. GOLDBERG, OD, FAAO
The corneal lenses I began fitting in 1950 featured spherical base curves that were 4.00D to 6.00D flatter than the flat corneal meridian (flatter than K). This lens design assured peripheral corneal clearance and lacrimal interchange. The clinical results from this contact lens design were moderate.
The clinical "breakthrough" in my practice and the contact lens industry began in April, 1956. At this time practitioners began fitting Wesley-Jessen's Sphercon corneal lenses on K for all day wear.
Long-term Benefits of GP Lenses:
I selected the long-term results that are described in Tables 1 through 5 because they are similar to other long-term results I found for thousands of patients I had fit with corneal lenses during my career.
Table 1 and Table 2 describe the long-term results of spherical base curve corneal lenses fit 4.00D flatter than K that the patients wore for 47 and 43 years, respectively. There is no direct mathematical relationship between the induced refractive and corneal topographical changes.
Table 3 describes the long-term results from a patient who wore corneal lenses for 33 years. I originally fit these lenses 4.00D flatter than K. I later refit the patient with aspheric multifocal lenses that featured paraboloidal base curves when the patient became presbyopic. I fit these lenses 4.00D steeper than K. This created a myopic decrease in conjunction with no direct mathematical changes of corneal curvatures.
Table 4 describes the long-term results from a patient who wore aspheric multifocal corneal lenses that featured hyperboloidal base curves, which I fit 6.00D steeper than the flatter corneal meridian. The patient wore these lenses for 16 years. The refractive and corneal topographical changes do not have a direct mathematical relationship. I changed the OS contact lens to accommodate the induced refractive change.
The patient in Table 5 wore ellipsoidal base curve corneal lenses for 11 years. I fit these lenses 1.50D steeper than K. Prior to visiting me to be fit with these corneal lenses, she had worn GP bitoric corneal lenses. I replaced them with the ellipsoidal corneal lenses, which created a slight refraction change OD and a meaningful change OS. Once again there is no direct mathematical relationship between refraction and corneal topographical changes.
Corneal lenses may induce refractive and corneal topographical changes. These changes result from the lens-to-cornea fitting relationship. The long-term changes I have described confirm that they have no dependable mathematical relationships, and this is consistent with what I reported in a previous study.
Although I found various refractive changes in the patients I mentioned in this article, I did not change the lens design variables if biomicroscopy confirmed that there was no corneal edema. These patients could interchange their contact lenses and conventional spectacles.
There is very little literature on the long-term effects of contact lens wear. This case series summarizes the refraction and keratometry changes for patients who have worn contact lenses for up to 47, 43, 33, 16 and 11 years. Although myopia decrease and astigmatism increase is the norm, other changes may occur.
Interestingly, although some long-term changes in the cornea have been reported as a result of contact lens wear, such as polymorphism and some corneal clouding and neovascularization, in this group visual acuity did not change. This indicates the long-term success of rigid contact lenses.
References are available upon request to the editors of Contact Lens Spectrum. To receive references via fax, call (800) 239-4684 and request document #94. (Have a fax number ready.)
Dr. Goldberg is an Emeritus Fellow of the American Academy of Optometry and is a Diplomate in the Section of Cornea and Contact Lenses.