Practicability and Effectiveness of Anterior Segment Optical Coherence Tomography (AS-OCT) of the Feline Iris as a Potential Biomarker for Iris Melanoma: A Study of 76 Cases.

PURPOSE: To evaluate the practicability and diagnostic value of anterior segment optical coherence tomography (AS-OCT) in cats, focusing on image quality and distinguishing iris melanosis from iris melanoma.

METHODS

Seventy-six client-owned cats were examined using a ZEISS Primus 200 OCT system. Image acquisition occurred without anesthesia in 65 cats; eight required injectable sedation, and three received anxiolytic medication. Mean iris thickness was measured; pigmentation-to-normal (PN) ratios were calculated from paired comparisons. OCT-based structural characteristics were analyzed in 49 eyes with suspected melanosis and 27 with suspected melanoma. Histological confirmation was available in 15 melanoma cases and one melanosis case following enucleation.

RESULTS

In normal and suspected melanosis-affected irides, mean iris thickness was similar (316.32 ± 89.36 μm; 319.20 ± 78.75 μm; PN ≈1.07 ± 0.14), with preserved architecture and consistent OCT layer visibility. In suspected and confirmed melanomas, mean iris thickness increased significantly (474.25 ± 139.14 μm; PN ≈1.61 ± 0.52; 592.54 ± 186.89 μm; PN ≈1.58 ± 0.27), accompanied by posterior signal attenuation and loss of structural detail. All 15 histologically confirmed melanomas matched the OCT-based suspicion, yielding a diagnostic sensitivity of 100%. One case initially classified as suspected melanosis underwent enucleation due to clinical progression and was histopathologically confirmed as benign melanosis, supporting the accuracy of the OCT-based assessment.

CONCLUSION

AS-OCT is a valuable, non-invasive modality for in vivo assessment of the feline iris. It is a feasible and practical tool that may support diagnosis of iris melanoma and assist in clinical decision-making, particularly regarding the need for enucleation.