A Pilot Study to Evaluate the Usefulness of Optical Coherence Tomography for Staging Iris Pigmented Lesions in Cats
by
, , , , and
Hiroyuki Komatsu
1,2,*
,
Minori Akasaka
1, 
Maresuke Morita
1,
Kensuke Usami
1,
Mao Inagaki
1,
Kayo Kumashiro
1,
Kinya Tsubota
2,
Yoshihiko Usui
2
,
Hiroshi Goto
2 and
Yoshitaka Kobayashi
1 1
Animal Eye Care Tokyo Animal Eye Clinic, 1-1-3 Kaminoge, Setagaya, Tokyo 158-0093, Japan
2
Department of Ophthalmology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku, Tokyo 160-0023, Japan
*
Author to whom correspondence should be addressed.
Vet. Sci. 2024, 11(6), 261; https://doi.org/10.3390/vetsci11060261
Submission received: 20 March 2024
/
Revised: 28 May 2024
/
Accepted: 4 June 2024
/
Published: 7 June 2024
(This article belongs to the Special Issue Spotlight on Ophthalmologic Pathology in Animals)
Simple Summary
Feline diffuse iris melanoma (FDIM) is the most common uveal tumor that develops within cats worldwide; thus, surgical resection is recommended at an early stage of the disease. However, it is difficult to differentiate early-stage FDIM from iris melanosis, a precursor lesion, based on clinical findings alone. In this study, we investigated the effectiveness of optical coherence tomography (OCT) in differentiating early FDIM from iris melanosis. The results of this study provide useful information for clinicians struggling with the timing of surgery. OCT has the potential to be an adjunctive diagnostic tool to differentiate iris melanosis from early-stage FDIM.
Abstract
This study investigated the utility of optical coherence tomography (OCT) for staging iris pigmented lesions in cats. Eighteen cats that underwent OCT examination for unilateral iris pigmented lesion were included. The cats were either suspected of melanosis due to clinical features (n = 8) or had been definitively diagnosed through histopathology with iris melanosis (n = 3), early feline diffuse iris melanoma (FDIM) (n = 4), or mid-stage or advanced FDIM (n = 3). From OCT images, mean iris thickness (MIT) was measured, and the ratio of pigmented lesion to normal iris (PN) was calculated. OCT images depicted the entire iris layer in all eyes with suspected melanosis, iris melanosis, and early FDIM, but observing the entire lesion in mid-stage/advanced FDIM was challenging. No significant difference in MIT was observed among the groups. Conversely, PN ratio was significantly higher (p < 0.05) in early FDIM (1.29 ± 0.16) than in suspected melanosis (1.02 ± 0.10) or iris melanosis (0.99 ± 0.09). Furthermore, OCT imaging revealed hyperreflective lines in 75% of eyes with suspected melanosis and in all the eyes with iris melanosis, corresponding to the pigmented lesions. Our results demonstrate that OCT is capable of detecting subtle differences in iris thickness and features in early-stage FDIM, indicating its potential utility in distinguishing between iris melanosis and early FDIM. Further study is warranted to verify the reliability of such OCT findings.
