Recovery from induced corneal edema and endothelial morphology after long-term PMMA contact lens wear.
OBJECTIVE
To study the effect of long-term polymethyl methacrylate (PMMA) contact lens wear (CLW) on corneal endothelial morphology and corneal hydration control (CHC).


METHODS
Sixteen long-term PMMA CL wearers (mean duration of wear 20.8 +/- 8.39 SD years; mean age 40.37 years +/- 10.47 SD) served as subjects and 14 age-matched, non-lens wearing subjects (mean age 41.29 years +/- 10.15 SD) served as controls. Corneal function was assessed by measuring the corneal thickness recovery rate (PRPH) after induced edema from a hypoxic stress load. Endothelial morphology was assessed by taking specular microscopy photographs, digitizing the images, and calculating the cell density, size, and coefficient of variation of cell size (CV).


RESULTS
Morphologic analysis showed a significant decrease in mean endothelial cell density (2147 vs. 2865, p < 0.01), an increase in mean cell size (582 vs. 381, p = 0.001), and an increase in polymegethism (CV, 0.32 vs. 0.26, p < 0.01) for PMMA lens wearers compared to agematched controls. Corneal function as measured by PRPH was not significantly different for PMMA lens wearers compared to controls when taken as a whole. However, a subgroup of PMMA lens wearers (seven eyes, four subjects) did show a substantial reduction in PRPH. These subjects also showed a strong relation between reduced PRPH, morphology, and years of lens wear (r2 = 0.99).


CONCLUSIONS
Longterm PMMA CLW leads to increased polymegethism in most, if not all, cases and results in a substantial decrease in corneal function in some cases.
McMahon
T T
TT
Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, College of Medicine, USA.
Polse
K A
KA
McNamara
N
N
Viana
M A
MA
D000328:Adult; D001834:Body Water / Q000378:metabolism; D002452:Cell Count; D003262:Contact Lenses, Extended-Wear; D015715:Corneal Edema / Q000209:etiology / Q000378:metabolism / Q000473:pathology*; D004728:Endothelium, Corneal / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D000860:Hypoxia / Q000150:complications; D008768:Methylmethacrylates; D008875:Middle Aged
D008768:Methylmethacrylates