Effects of long term extended wear of PMMA lenses on corneal function: a case report

Recent studies have shown that some long-term PMMA contact lens wearers who are presumably exposed to hypoxia can develop modest but permanent changes in corneal structure and function. What is not known is the corneal effects that may result from severe and long-term exposure to an hypoxic environment. This case report is presented to illustrate an extreme example of the effects of the cornea from prolonged exposure to hypoxia.

A 37-year-old male who had worn PMMA lenses on a 2-week extended wear basis for 20 years was examined in the laboratory to assess changes in corneal structure and function. Function was determined by monitoring the rate at which the cornea recovered from induced edema and is expressed as a percent recovery per hour (PRPH). Morphology was studied via specular microscopy.

For this subject, the PRPH was 39.6 percent/hr and 40.5 percent/hr for right and left eyes respectively; these values are substantially reduced compared to the reported 55.3 percent/hr for an age-matched, non-contact lens wearing population. Specular microscopy demonstrated reduced cell counts of 1,052 cells/mm2 OD and 1,741 cells/mm2 OS compared to an age adjusted normal population with 2,853 +/- 320 cells/mm2.

This case example appears to represent an extreme case of contact lens abuse and the effects of long-term hypoxic contact lens wear on corneal function.