Clinicopathologic Findings of Congenital Megalocornea in Three Blue-Throated Conures (Pyrrhura cruentata).

Abstract

OBJECTIVE: To describe the first known occurrence of megalocornea in a cohort of juvenile blue-throated conures (Pyrrhura cruentata). ANIMALS STUDIED: Three genetically related juvenile blue-throated conures. PROCEDURES: The information collected included physical and ophthalmic examination findings, ocular ultrasound biomicroscopy, Micro-CT analysis, postoperative outcomes following chemical cycloablation and/or enucleation, and histopathology. RESULTS: Ophthalmic examinations revealed multiple congenital ocular anomalies and bilateral blindness with the predominant feature of corneal enlargement. Several eyes developed corneal edema and exposure keratitis from lagophthalmos. Ultrasound biomicroscopy (UBM) showed a globoid cornea and enlarged anterior chamber with or without anterior displacement of the lens. Micro-CT analysis revealed normal skull conformation with bilateral enlargement of the anterior segments. An initial diagnosis of presumptive congenital glaucoma with buphthalmos was made. All conures had a chemical cycloablation procedure performed in the left eye to decrease ocular size. One conure had an enucleation of its right eye (OD) due to severe corneal ulceration. Two conures were humanely euthanized due to systemic health concerns shortly after initial presentation, and one died suddenly of a suspected cardiac event 8 years later. Ocular histopathology was performed on all 6 eyes of 3 conures, confirming a diagnosis of megalocornea with secondary ulcerative keratitis, stromal attenuation, and marked fibrosis with a discontinuous Descemet's membrane. CONCLUSION: This case series represents the first documented report of congenital megalocornea in blue-throated conures, which should be considered as a differential in birds with presumed buphthalmos from glaucoma.