Effect of linoleic acid and gamma-linolenic acid on tear production, tear clearance and on the ocular surface after photorefractive keratectomy.
BACKGROUND
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).


METHODS
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)).


RESULTS
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).


CONCLUSIONS
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.
Macrì
Angelo
A
Via Strasserra 6/18, 16100 , Genoa, Italy. macria@libero.it.|U.O. Oculistica, San Martino Hospital, Genoa, Italy. macria@libero.it.
Giuffrida
Sebastiano
S
Fidia Oftal-Bausch&Lomb Pharmaceuticals, Catania, Italy.
Amico
Valentina
V
Fidia Oftal-Bausch&Lomb Pharmaceuticals, Catania, Italy.
Iester
Michele
M
Department of Neuroscience, Ophthalmology and Genetics, University of Genoa, Italy.
Traverso
Carlo Enrico
CE
Department of Neuroscience, Ophthalmology and Genetics, University of Genoa, Italy.
D000328:Adult; D000527:Alprostadil / Q000096:biosynthesis; D003287:Contrast Media / Q000493:pharmacokinetics; D005123:Eye / Q000187:drug effects*; D019793:Fluorescein / Q000493:pharmacokinetics; D006801:Humans; D054018:Lasers, Excimer; D019787:Linoleic Acid / Q000627:therapeutic use*; D018903:Photorefractive Keratectomy; D011182:Postoperative Care; D011184:Postoperative Period; D011355:Prodrugs / Q000627:therapeutic use*; D012030:Refractive Errors / Q000503:physiopathology; D054140:Refractive Surgical Procedures; D013666:Tears / Q000187:drug effects / Q000378:metabolism*; D017965:gamma-Linolenic Acid / Q000627:therapeutic use*
D003287:Contrast Media; D011355:Prodrugs; D017965:gamma-Linolenic Acid; D019787:Linoleic Acid; D000527:Alprostadil; D019793:Fluorescein