A technique for quantitation of protein deposits on rigid gas permeable contact lenses.
OBJECTIVE
The purpose of this study was to develop a method for quantitating protein on rigid gas permeable (RGP) lenses and apply it to worn lenses.


METHODS
We built a video microscope and wrote software to measure light absorbance by contact lenses before and after protein staining with Coomassie brilliant blue. We corrected for the temporal stability and spatial uniformity of the system, and set the iris aperture so that both lens surfaces could be simultaneously focused. We examined four RGP lens types worn by 22 patients. Standard curves were prepared with plastic discs spiked with dialyzed Coomassie blue-stained bovine serum albumin.


RESULTS
The method was linear (R2 = 0.99) from 14 to over 100 microg protein per image and independent of dioptric power from -6 to +14 diopters. Protein quantities on worn Equalens II, Advent, Quantum II, and Fluoroperm 92 lenses were not significantly different (123 +/- 36, 111 +/- 28, 110 +/- 23, and 83 +/- 15 microg/lens; means +/- SEMs, P > 0.7). Patients differed (P < 0.05) in protein deposition, independently of lens type, and fit a Poisson distribution.


CONCLUSIONS
The method is adequate for quantitating protein on RGP lenses or for examining the efficacy of cleaning regimens or care systems. However, because of the non-Gaussian distribution of patient protein deposits, paired or cross-over experimental design and testing is recommended for studying protein deposition in clinical trials.
Tan
A
A
Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Sydney, Australia.
Milthorpe
B K
BK
Huff
J W
JW
D000818:Animals; D002417:Cattle; D018639:Contact Lens Solutions / Q000592:standards; D003262:Contact Lenses, Extended-Wear; D003720:Densitometry; D005136:Eye Proteins / Q000032:analysis*; D006801:Humans; D007202:Indicators and Reagents; D012394:Rosaniline Dyes; D014741:Video Recording
D018639:Contact Lens Solutions; D005136:Eye Proteins; D007202:Indicators and Reagents; D012394:Rosaniline Dyes; C048139:Coomassie blue