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Editors Selection IGR 9-4

Medical Treatment: Ocular Surface Disease

Comment by Paul Palmberg on:

74615 Use of Topical Cannabinomimetic Palmitoylethanolamide in Ocular Surface Disease Associated with Antiglaucoma Medications, Di Zazzo A; Roberti G; Mashaghi A et al., Journal of Ocular Pharmacology and Therapeutics, 2017; 33: 670-677

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The authors report the results of a pilot study, described as an open label, single masked, randomized trial of the effect of adding DeFluxa drops (containing palmitoylethanolamide) bid for 30 days to usual topical glaucoma therapy to see if the signs of ocular surface inflammatory disease would be improved. The rationale for the study was sound, as palmitoylethanolamide, a natural substance in the brain, has known anti-inflammatory actions (inhibits inducible nictric oxide synthase, inducible cyclooxygenase, and cytokines IL-1b, PGE2, and TNF-a by inhibiting the transcription of nuclear factor NFkb), and analgesic effect (by stimulation of peroxisome proliferator-activated receptor [PPAR]a and indirectly by cannabinoid receptor CB1).

Palmitoylethanolamide, a natural substance in the brain, has known anti-inflammatory actions

The results reported were small, but statistically significant improvements in tear production (Schirmer score), tear film stability (tear break up time) and hyperemia score. The control group was given preservative free hyaluronic acid drops to use, with the implication that it served as a vehicle control. In neither group did the addition of study drops affect IOP control.

There were aspects of the study that were not clearly defined, most importantly what "single masked" meant. Were the subjects or the evaluators masked? That is critical to the validity of the study as the measurements used were subject to some bias. Were the subjects "assigned" to the treatment groups, as stated in one place, or "randomized", a word mentioned only in a table? What were the glaucoma medications being used, since prostaglandin analogs, alpha-2 agonists, and preservatives would be expected to have different mechanisms of promoting hyperemia and ocular surface disorder.

Despite the limitations of this small pilot study, the results do suggest that a larger and longer placebo controlled, double masked trials should be performed in subjects with ocular surface inflammatory disease using specific classes of glaucoma drops.

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