Two different procedures for managing ocular melanosis presenting scleral pigmentation with glaucoma in a Shih-Tzu dog: A case of definitive diagnosis in one eye and a presumed diagnosis in the contralateral eye

Abstract

A 12-year-old castrated male Shih-Tzu dog was referred for uncontrolled glaucoma and uveitis with highly pigmented sclera, in both eyes (OU). On ophthalmic examination, the menace response, dazzle reflex and pupillary light reflex were negative OU. The intraocular pressure was 27 mmHg in the right eye (OD) and 70 mmHg in the left eye (OS) despite the administration of antiglaucoma eyedrops. Ultrasound biomicroscopy revealed a closed ciliary cleft OU. Ocular ultrasonography revealed hyperechoic materials in the vitreous OU and retinal detachment OS. When presented for recheck, an extensive malacic corneal ulcer was observed OS. To relieve pain in the blind eyes, enucleation OS and pharmacologic ciliary body ablation (CBA) OD were performed. Histologically, ocular melanosis, which is an inherited disease in the Cairn Terrier breed, was identified in the enucleated eye. The uvea was heavily pigmented. The iris and ciliary body were mildly distorted by a single population of large, round, nonneoplastic cells with pigmented cytoplasm. There was no evidence of an intraocular mass or metastasis before and after intravitreal CBA. This is the first report of bilateral ocular melanosis in a Shih-Tzu dog. Ocular melanosis is a possible differential diagnosis for globe presenting scleral pigmentation with glaucoma in even non-Cairn Terrier breeds and pharmacologic CBA could be considered as a treatment for ocular melanosis with end-stage glaucoma.

Keywords: Cairn Terrier; Shih-Tzu; ciliary body ablation; ocular melanosis; scleral pigmentation.

FIGURE 1

Photographs of both eyes of a 12‐year‐old Shih‐Tzu dog with slit‐lamp biomicroscopy and ultrasound biomicroscopy (UBM). The right eye (a) and the left eye (b, c) had pigmentation on the sclera along the rim of the limbus (asterisk). Moderate conjunctival hyperaemia and corneal oedema (arrowhead) were present in both eyes. UBM images confirmed that the ciliary clefts of the right eye (d) and the left eye (e) were closed.

FIGURE 2

Photographs of the right eye before and after intravitreal cidofovir injection. (a) Before intravitreal cidofovir injection, intraocular pressure (IOP) was elevated at 84 mmHg, and consequently, corneal oedema was severe. (b) Two weeks after intravitreal cidofovir injection, IOP of the right eye decreased to 2 mmHg, and corneal oedema decreased significantly. (c) Gross photograph of the right eye. Dark brown to black pigmentation was distributed 360 degrees around the perilimbal zone of the sclera.

FIGURE 3

Photomicrographs of sections of the enucleated left eye. (a) Subgross photograph of the globe. The iris and ciliary body were highly pigmented. The iris leaflet was moderately expanded, but there was no distinct mass. (b) Pigmented cells infiltrated the iris. (c) Pigmented cells infiltrated the ciliary body, choroid (arrowhead), and sclera (asterisk). (d) Some pigmented cells were found in the posterior corneal stroma (arrowhead). (e) Pigmented cells contained numerous melanin granules of dark brown to black in their cytoplasm. (f) The iridocorneal angle was narrowed, and the ciliary cleft was closed by pigmented cells (arrowhead). (g) Full‐thickness retinal atrophy was observed. (H) Cupping and gliosis of the optic nerve head was observed. Retinal detachment was also observed. H&E stain; Scale bar: A = 5.5 mm; B,H = 500 µm; C,F = 200 µm; D,G = 100 µm; E = 50 µm.