Retinoschisis: a retrospective study of an uncommon retinal change in cats and dogs.

Retinoschisis is a poorly documented form of retinal degeneration characterized by cyst-like splitting that occurs between the inner nuclear and outer plexiform layers. The pathogenesis of retinoschisis is incompletely understood, but congenital, acquired and secondary aetiologies (glaucoma, inflammation, neoplasia) are described in humans. This retrospective study investigated the prevalence and associated histological and clinical features of retinoschisis in cats and dogs submitted for biopsy over a 10-year period. Of 140 samples with documented 'retinal vacuolation', four out of 120 (3%) canine samples and one out of 20 (5%) feline samples had changes consistent with retinoschisis. In most cases (80%), there was concurrent retinal detachment. In cases with available histories, increased intraocular pressure, proptosis and retinal detachment were reported clinical findings. In cats and dogs, retinoschisis is a retinal change that is generally secondary to other ocular lesions.

Bilateral retinoschisis in a dog: A veterinary clinical application for optical coherence tomography.

A 11-year-old neutered male Labrador retriever-cross dog was presented to the University of Missouri-Columbia Veterinary Ophthalmology Service for subtle visual deficits. Indirect ophthalmoscopy revealed a smooth, bullous elevation in the superior-temporal retina OU. Optical coherence tomography (OCT) performed OU showed inner retinal separation consistent with retinoschisis. Electroretinography (ERG) revealed markedly reduced b-wave amplitudes in the more severely affected eye (OD) compared with the less severely affected eye (OS). The most notable reductions were in the rod response and 30-Hz flicker b-waves OD which were approximately 50% of the corresponding amplitudes OS. Implicit times, particularly the a-wave implicit times, were noticeably longer OD compared with OS. Lesions remained unchanged over 4 months at which time the dog was humanely euthanized for reasons unrelated to the ocular disease. Significant light microscopic ocular findings were bilateral superior temporal peripheral retinoschisis. The separation of the retinal tissue was similar between eyes and effectively divided the outer plexiform layer. In addition, thinning of the surrounding retinal layers was present. To the authors' knowledge, this is the first case of canine retinoschisis diagnosed with OCT, evaluated with electroretinography, and confirmed with light microscopic examination. History, clinical, and diagnostic findings, with the absence of disease progression over time, are analogous with cases of acquired senile retinoschisis in humans.