Phospholipids and their degrading enzyme in the tears of soft contact lens wearers.
OBJECTIVE
Low tear phospholipids levels are associated with tear film instability in soft contact lens wearers. We assayed levels of phospholipids and their degrading enzyme secretory phospholipase A2 (sPLA2) both in tears and deposited on contact lenses composed of 2 hydrophilic materials after 1 day of routine use.


METHODS
Polymacon (Medalist; FDA group 1, low water/nonionic) and Etafilcon A (One Day Acuvue; group 4, high water/ionic) contact lenses were worn for 12 hours by 16 experienced contact lens wearers. Phospholipids in tear fluids and deposited on contact lenses were estimated by phosphorus determination with ammonium molybdate through enzymatic digestion. Double-antibody sandwich ELISA was used to determine group IIa sPLA2 concentrations, and sPLA2 activity was assayed using 1,2-diheptanoyl thio-phosphatidylcholine as substrate.


RESULTS
Phospholipids concentrations in tears with Polymacon and Etafilcon A were 186 +/- 39 and 162 +/- 33 microg/mL, respectively. The latter concentration was significantly lower than that observed in the same subjects when not wearing contact lenses (P = 0.0023). In tears, both group IIa sPLA2 concentrations and enzymatic activity remained unchanged, regardless of lens wearing. However, Etafilcon A (0.57 +/- 0.09 microg/lens) showed more group IIa sPLA2 deposition than Polymacon (0.01 +/- 0.01 microg/lens; P < 0.001). Furthermore, group IIa sPLA2 deposited on Etafilcon A but not on Polymacon lenses retained its enzymatic activity.


CONCLUSIONS
Significant differences of group IIa sPLA2 deposition were found in the 2 lenses tested. Such deposition might induce phospholipid hydrolysis in tears and thereby promote tear film instability in hydrophilic contact lens wearers.
Yamada
Masakazu
M
Division for Vision Research, National Institute of Sensory Organs, National Tokyo Medical Center, 2-5-1 Higashigaoka, Meguro-ku, Tokyo 152-8902, Japan. yamadamasakazu@kankakuki.go.jp
Mochizuki
Hiroshi
H
Kawashima
Motoko
M
Hata
Seiichiro
S
D000328:Adult; D003263:Contact Lenses, Hydrophilic; D004797:Enzyme-Linked Immunosorbent Assay; D005136:Eye Proteins / Q000378:metabolism*; D005260:Female; D054501:Group II Phospholipases A2; D006801:Humans; D008297:Male; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D010743:Phospholipids / Q000378:metabolism*; D013666:Tears / Q000378:metabolism*
D005136:Eye Proteins; D010743:Phospholipids; C042434:tear proteins; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2