The aim of this study was to evaluate the effect of linoleic acid (LA) and gamma-linolenic acid (GLA), both precursors of PGE(1), on tear production, tear fluorescein clearance and on the ocular surface after photorefractive keratectomy (PRK).

Sixty subjects (age 25+/-10 years; refractive error -3+/-2 diopters (spherical equivalent), mean +/- standard deviation) undergoing PRK were enrolled. The inclusion criteria were: Schirmer 1 test >10 mm/5 min, no corneal fluorescein staining, low irritation symptoms (questionnaire score <5), standardised visual scale (to evaluate tear fluorescein clearance) score <3. Patients were randomly divided into two groups. One group of 31 subjects was treated once daily orally with tablets containing LA (28.5 mg) and GLA (15.1 mg) (from 3 days before PRK to 1 month after PRK). The control group (29 subjects) underwent PRK and received no treatment with LA and GLA. A symptoms questionnaire, Schirmer 1 test and fluorescein clearance test (FCT) using the standardised visual scale were performed before starting therapy (T(0)) and 30 days after PRK (T(1)).

All patients completed the study. The Schirmer 1 test varied from 16.3+/-6.9 (T(0)) to 17.6+/-7.2 (T(1)) for the treated group and from 18.3+/-6.2 (T(0)) to 15.7+/-7.4 (T(1)) for the untreated group ( P<0.0001, two-tailed unpaired t-test). FCT was 1.9+/-0.6 at T(0) and 1.6+/-0.8 at T(1) for the treated group and 1.7+/-0.7 at T(0) and 2.0+/-0.9 at T(1) for the untreated group ( P<0.0001). The symptoms score was 4.7+/-1.9 at T(0) and 7.6+/-7.2 at T(1) for the treated group and 4.2+/-2.0 at T(0) and 10.1+/-7.6 at T(1) for the untreated group ( P<0.05).

Reduced corneal sensitivity has already been proved after PRK. This could be the main reason for a decrease in tear production and for a reduced blinking rate leading to delayed tear clearance. The oral precursors of PGE(1), LA and GLA, could be helpful in increasing tear production and clearance after PRK.