REDUCTION IN CORNEAL HYDRATION CONTROL AFTER 20 YEARS OF EXTENDED WEAR OF PMMA LENSES

Title REDUCTION IN CORNEAL HYDRATION CONTROL AFTER 20 YEARS OF EXTENDED WEAR OF PMMA LENSES
Author, Co-Author Timothy McMahon, Ken Polse
Topic
Year
1992
Day
Saturday
Program Number
Poster 19
Room
Great Hall
Affiliation
Abstract A human in vivo test has been described which measures overall corneal hydration control (CHC) by monitoring the exponential rate (expressed as percent corneal thickness recovery per hour; PRPH) at which the cornea recovers after inducing edema. Using this test on a group of subjects who had 5 years or more of PMMA wear, investigators found a reduction in the PRPH corresponding to -1.26%/yr. which was attributable to the contact lens wear alone. The implications of these results provided the basis for continued efforts to validate the CHC test as an index of corneal status. This has been done by making additional PRPH measurements on contact lens patients with different lens wearing histories. In this report, we provide information on corneal structure and function from a 37-year-old male who wore PMMA lenses on an extended wear basis for 20 years. After discontinuing lens wear for 60 days the slit lamp exam was entirely normal. However, the PRPH was found to be 39.6%/hr. (95% CL 35.6 to 43.4) and 40.5%/hr. (95% CL 37.1 to 43.8) for right and left eyes respectively, which is considerably lower when compared to a group of 28 non-CL wearers (35-45 years) whose mean PRPH was 55.3+ 6.6%/hr. Analysis of the endothelial cell count (ECD) for this PMMA wearer was 1,052 and 1,741/mm(2)[superscript] right and left eyes respectively, which differs substantially from the 28 non-wearing subjects whose mean ECD was 2,853 + 320/mm(2)[superscript]. Assuming that this PMMA wearer discontinues all contact lens wear, we predict the PRPH to be less than 20%/hr. by age 60. Previous studies have *shown that a PRPH below 20%/hr. may put the cornea at risk for decompensation following procedures such as standard cataract extraction. This case suggests that slit lamp examination alone may provide insufficient information to either assess the functional status or make a prognosis for long term survival of the cornea. Study funded by NEI EY RO1 4390 and Illinois Society for the Pr
Affiliation of Co-Authors
Outline