OBJECTIVES: Dry eye disease and meibomian gland dysfunction are both prevalent conditions that lead to alterations of the tear film and consequent ocular surface damage. Despite the increased interest in the assessment of both of these conditions, there still remains a deficit in simple, clinically applicable grading scales for meibomian gland expression and effective therapeutic management options for dry eye disease. Therefore, two distinct studies with overlapping designs were executed to (1) develop a clinical grading scale for the assessment of meibomian gland expressibility and to (2) evaluate the efficacy of omega-3 fatty acid supplementation in a randomized, placebo-controlled, double-masked, pilot study of dry eye disease.
METHODS: A meibum expressibility scale was developed using a new standardized meibomian gland expression device, which provides constant pressure along the inferior lid. For the scale development, 30 patients (52.5 ± 12.4 years; 93.33% female) with mild to moderate dry eye were compared to 13 normal, non-dry eye subjects (25.6 ± 4.3 years; 46.1% female). The device was placed 4 glands lateral to the inferior punctum and 1 mm below the inferior lash line and held stable for 15 seconds, such that the glands expressing meibum were then counted. The weighted kappa statistic was used to evaluate the extent of agreement between visits in the normal sample, and a Receiver Operating Characteristic (ROC) curve was created to test the proposed scale. The same 30 dry eye patients were then randomized to either omega-3 fatty acid supplementation or soybean oil (placebo) and followed at 4-week intervals for 8 weeks. Outcome variables were tear osmolarity, OSDI score, SANDE analog values, and artificial tear reliance.
RESULTS: For the meibum expressibility scale, the mean number of glands that expressed from the worse lid in the normal group was 3.54 ± 1.61, while 1.53 ± 1.28 glands expressed in the dry eye group. In the dry eye group, one subject showed 5 glands expressing, and 29 had scores of 4 or less. In the normal group, 11 of 13 patients expressed from 3 or more glands. In the omega-3 study, there were no detectable associations with any of the clinical variables in the treatment arm. The placebo group trended toward improvement in osmolarity (worse eye), OSDI (baseline versus 8 weeks), SANDE values (at 4 weeks and 8 weeks), and tear reliance (at 8 weeks).
CONCLUSION: A 4-3-2-1 meibomian gland scoring system is proposed, whereby 4+=normal expressibility, 3=mildly reduced expressibility, 2=moderately reduced expressibility, and 1 or 0=severely reduced expressibility. Further validation of the scale is warranted. For the study assessing omega-3 fatty acid supplementation, there was little to no observed therapeutic benefit of omega-3s in this sample of dry eye patients. Further, soybean oil seems to lack the inert qualities of an appropriate placebo in a clinical trial of dry eye disease. Additional studies that incorporate a proper dosage, an adequate placebo, and omega fatty acid dietary consumption in their study designs are necessary to determine the therapeutic value of omega-3s in the management of dry eye disease.