Evaluation of ocular surface parameters before and after cryo- and laser therapy for distichiasis in dogs: A pilot study.

Objective: The aim of this pilot study was to establish a satisfactory, scientific approach to effectively compare quantitative measurements of various ocular surface parameters before and after surgical treatment in dogs suffering from distichiasis.

Methods: An ophthalmic examination was conducted on 12 dogs (23 eyes) before and after surgical treatments for distichiasis, at four different time points, (t₀ = before surgery, t₁ = 1-2 h after surgery, t₂ = 1 week after surgery, t₃ = 1 month after surgery, and t₄ = 6 months after surgery) between 2021 and 2022, and analyzed retrospectively. The examination included Schirmer tear test-1 (STT-1), interferometry, noninvasive tear film break-up time (NIBUT), tear meniscus size (TMS), and meibography.

Results: No statistically significant changes were found in STT-1 (t₀: 22.2 ± 6.5 mm, t₂: 22.5 ± 5.7 mm, t₃: 20.8 ± 5.1 mm, and t₄: 22.6 mm ± 4.8 mm) before and after surgery. Mean interferometry scores showed a slight, not statistically significant, decrease from t₀ to t₃ and t₄ (t₀: 2.1 ± 0.8, t₁: 2.1 ± 0.7, t₂: 2.1 ± 0.9, t₃: 1.8 ± 0.6, and t₄: 1.9 ± 1.1). Mean NIBUT did not change significantly between time points (t₀: 3.9 ± 1.3 s, t₁: 4.0 ± 1.3 s, t₂: 4.0 ± 1.4 s, t₃: 3.5 ± 0.7 s, and t₄: 3.5 ± 0.9 s). TMS showed a slight, not statistically significant increase (t₀: 0.5 ± 0.3 mm, t₁: 0.5 ± 0.3, t₂: 0.5 ± 0.3 mm, t₃: 0.6 ± 0.2 mm, and t₄: 0.7 ± 0.3 mm). There were no changes in the gross morphology of the meibomian glands (MG).

Conclusion: This pilot study could not detect a negative effect of different forms of treatment of distichiasis on the precorneal tear film parameters in dogs. However, due to the study's retrospective nature and small sample size, no definitive conclusion can be drawn regarding the changes at the different time points.