Cannabis and the Cornea.

Purpose: While cannabis has the potential to reduce corneal pain, cannabinoids might induce side effects. This review article examines the effects of cannabinoids on the cornea. As more states and countries consider the legalization of adult cannabis use, health-care providers will need to identify ocular effects of cannabis consumption.Methods: Studies included in this review examined the connection between cannabis and the cornea, more specifically anti-nociceptive and anti-inflammatory actions of cannabinoids. NCBI Databases from 1781 up to December 2019 were consulted.Results: Five studies examined corneal dysfunctions caused by cannabis consumption (opacification, decreased endothelial cell density). Twelve studies observed a reduction in corneal pain and inflammation (less lymphocytes, decreased corneal neovascularization, increased cell proliferation and migration).Conclusion: More than half of the studies examined the therapeutic effects of cannabinoids on the cornea. As the field is still young, more studies should be conducted to develop safe cannabinoid treatments for corneal diseases.

Protective effects of dispersive viscoelastics on corneal endothelial damage in a toxic anterior segment syndrome animal model.

PURPOSE: We evaluated whether viscoelastics have protective effects on the corneal endothelial cell damage in a toxic anterior segment syndrome (TASS) animal model depending on the types of viscoelastics. METHODS: A TASS animal model was established with an injection of 0.1 mL o-phthaldehyde solution (0.14%) into the anterior chamber of New Zealand white rabbits. One of two different viscoelastics, 1% sodium hyaluronate (cohesive group) or a 1:3 mixture of 4% chondroitin sulfate and 3% sodium hyaluronate (dispersive group), was injected into the anterior chamber. After five minutes, it was removed using a manual I/A instrument, and then 0.1 mL of o-phthaldehyde solution (0.14%) was injected into the anterior chamber. Damage to corneal endothelial cells was compared between the two groups. RESULTS: The corneal thickness increased quickly in both groups after the disinfectant injection. However, the dispersive group showed relatively mild corneal edema compared to the cohesive group. The mean corneal haze score in the dispersive group also was lower than that of the cohesive group. These partial protective effects of the dispersive viscoelastic were demonstrated by the different findings of a live/dead cell assay, TUNEL staining, and scanning electron microscopy between the two groups. CONCLUSIONS: The TASS animal model seems to be a useful means to evaluate corneal endothelial cell damage caused by toxic substances to find ways to protect or reduce endothelial cell damage. Dispersive viscoelastics were shown to have partial protective effects against corneal endothelial cell damage caused by a toxic disinfectant.

Inadvertent intracorneal injection of local anesthetic during lid surgery.

PURPOSE: To report a case of inadvertent intracorneal injection of anesthetic agents during lid anesthesia and corneal penetration without full-thickness perforation. METHOD: Case report. RESULTS: Corneal edema with acute loss of vision was noted. The patient was treated with topical, antibiotic, cycloplegic, hyperosmotic agent and lubricant. While the edema slowly subsided, a loss in endothelial cell count was noted. CONCLUSIONS: The effects of intracorneal injection of lignocaine, bupivacaine, and its preservatives have not previously been reported in the literature. A lower postinjection endothelial cell count and associated clinical features in our case indicate that endothelial toxicity occurred. This potential complication should be kept in mind with necessary precautions taken during injection of the eyelid, particularly in cases with preexisting lid laxity.