Comparative evaluation of cyclosporine A and thymoquinone treatments in a benzalkonium chloride-induced experimental dry eye model.

OBJECTIVE

This study aimed to compare the therapeutic efficacy of Cyclosporine A (CsA) and Thymoquinone (TQ) in treating keratoconjunctivitis sicca (KCS) in an experimental rabbit model.

DESIGN

The right eyes were assigned to CsA and the left to TQ. During treatment, one drop of each agent was applied twice daily for 45 days.

PARTICIPANTS

An experimental dry eye model was established in 36 New Zealand rabbits (20 females, 16 males), aged 3 months and weighing 2-2.5 kg.

METHODS

KCS was induced with 5 μL of 0.1% benzalkonium chloride (BAK) applied twice daily for 14 days. Clinical evaluations included the Schirmer tear test I (STT-I), fluorescein staining, corneal opacity, neovascularization, conjunctival hyperemia, and chemosis. Measurements were taken on days 0, 3, 5, 7, 14 (induction) and 15-60 (treatment). Statistical significance was set at p < 0.05.

RESULTS

By day 15, tear production had decreased, and clinical signs including conjunctival hyperemia and ocular irritation were observed. Epiphora became mucoid and corneal lesions appeared (p < 0.001). During treatment, both groups showed significant increases in tear production and decreases in hyperemia, chemosis, and corneal staining (p < 0.001). Differences between groups were noted in STT-I on days 28, 35, 50 (p < 0.05), and 54 (p < 0.001), and in corneal staining on several days (p < 0.001). Corneal opacity also differed on days 15, 18, 28, 35, and 38 (p < 0.05).

CONCLUSION

KCS is a multifactorial condition involving inflammatory disruption of the tear cycle. In this contralateral-eye rabbit model, both CsA and TQ treated eyes showed clinical improvement over time; however, because untreated and vehicle control groups were not included, the findings should be interpreted primarily as a comparative assessment between the two active treatments rather than as definitive evidence of absolute therapeutic efficacy. Additional studies including appropriate control groups and mechanistic endpoints are needed to further clarify the therapeutic potential of TQ.