Introduction:

PRK is known to cause a temporary reduction in corneal sensitivity, leading to tear film changes, lowered reflex tearing, and production of inflammatory cytokines and free radicals. Transitory dry eye is a common complication after PRK and LASIK, lasting longer in patients with preoperative dry eye (1).

The anti-inflammatory properties of the fatty acid GLA have long been known. Recent studies report that oral administration of GLA and LA leads to a significant increase in tear concentrations of anti-inflammatory prostaglandin E1 (2,3), and reduces the symptoms of dry eye (2). The aim of this study was to evaluate the effects of GLA and LA on tear production, tear fluorescein clearance, dry eye symptoms, and the ocular surface after PRK (4).

Methods:

In this randomized, controlled trial, 31 patients received modest amounts of oral GLA and LA 3 days prior to 30 days after undergoing PRK. Another 29 patients underwent PRK without the supplement, serving as controls. The following measurements were made at baseline and at the end of the study period: symptom questionnaire, Schirmer 1 test, fluorescein clearance test using standardized visual scale and corneal fluorescein staining.

Results:

All 60 patients completed the study. Statistical analysis showed a significant mean difference between the groups for dry eye symptoms, fluorscein clearance, and Schirmer's results. Compared to controls, the treated group had lower symptom scores, greater Schirmer test values, and more favorable fluorescein clearance scores [See Figures 1-3]. Both groups showed no signs of corneal staining at baseline. While more areas stained in controls than treated patients at 1 month post-surgery (0.09 ± 0.10 vs. 0.25 ± 0.21 respectively), the difference was not significant. The researchers concluded that oral precursors of prostaglandin E1, GLA and LA, could be helpful in increasing tear production and clearance after PRK.

Figure 1. Results of symptoms questionnaire (mean score) before starting study (T0) and 1 month after PRK (T1). (*P<0.05)

Figure 2. Results of Schirmer 1 test (mm/5 min) before starting study (T0) and 1 month after PRK (T1). (*P<0.0001)

Figure 3. Results of fluorescein clearance test by means of visual scale (mean score) before starting study (T0) and 1 month after PRK (T1). (*P<0.0001)

References

1. Toda I et al. Laser-assisted in situ keratomileusis for patients with dry eye. Arch Opthalmol 120:1024-28, 2002.
2. Aragona P et al. Tear PGE1 levels in dry eye patients after treatment with essential fatty acids. Invvest Ophthalmol Vis Sci 42:5259, 2001.
3. Barabino S et al. Systemic linoleic and gamma-linolenic acid therapy in dry-eye syndrome with inflammatory component. Cornea 22(2): 97–101, 2003.
4. Macri A et al. Effect of linoleic acid and gamma-linolenic acid on tear production, tear clearance and on the ocular surface after photorefractive keratectomy. Graefes Arch Clin Exp Ophthalmol (published first online, May 27, 2003) Full paper available upon request.