Ocular abnormalities in Polish Hunting Dogs

Abstract

This study aimed to describe and determine the prevalence of ocular abnormalities in Polish Hunting Dogs. The study was conducted with 193 Polish Hunting Dogs: 101 female and 92 male animals, aged between 3 months and 12 years. Ophthalmic examinations were performed using slit lamp biomicroscopy, ophthalmoscopy, and tonometry based on the ophthalmological protocol for the examination of hereditary eye diseases. Spectral-domain optical coherence tomography (SD-OCT) was performed for dogs with sudden acquired retinal degeneration syndrome (SARDS) and progressive retinal atrophy (PRA), while electroretinography was also performed in dogs with SARDS. Five dogs (2.6%) were diagnosed with cataract, iris coloboma in 3 dogs (1.6%), ocular dermoid in 1 dog (0.5%), and retinal dysplasia, distichiasis and entropion in 1 dog (1%). Three dogs (1.6%) were diagnosed with PRA and SARDS occurred in 1 dog. Retinal lesions was observed in 16 dogs (8.3%). The clinical signs of retinopathy observed in Polish Hunting Dogs included discoloration of the tapetal fundus, patchy increased reflectivity in the region of discoloration, focus of hyperpigmentation and an area of tapetal hyper-reflectivity with a pigmented center. SD-OCT performed in the 3 dogs with PRA revealed alteration in the retinal layers, which was most advanced in the non-tapetal fundus. Although SD-OCT revealed retinal layers with normal architecture only in some parts of the dorsal, nasal and temporal regions in dogs with SARDS, areas of disorganized external limiting membrane, myeloid zone, ellipsoid zone, outer photoreceptor segment and interdigitation zone were also observed. Polish Hunting Dogs should undergo periodic ophthalmological examination for the evaluation of other hereditary eye diseases. The prevalence of retinal lesions in Polish Hunting Dogs requires further research.

Fig 1. Discoloration of the tapetal fundus in dog number 3, diagnosed with retinal lesions.

Fig 2. Discoloration of the tapetal fundus with irregular foci of hypereflection in dog number 9, diagnosed with retinal lesions.

Fig 3. The hyperpigmentation with spreading halo of hyperreflection localized dorsally in dog number 10, diagnosed with retinal lesions.

Fig 4. Measurement of size (length and width) of retinal lesion and its rim thickness (TRT), in dog number 16, also diagnosed with SARDs.

Fig 5. Symmetrical funduscopic changes in dog PRA 3.

A- right eye, B- left eye.

Fig 6. Advanced retinal atrophy presented as homogenous, thin hyyperrefectiv band on SD-OCT scan in dog PRA 3.

Fig 7. Disorganization of the retinal layers and atrophy pronounced in the nontapetal fundus, in dog PRA 3.

Green vertical line on SD-OCT scan indicates localization on fundus.

Fig 8

Complete disorganization of outer retina and the blurring of their respective borders (red arrows). The INL OPL and ONL layers are visible, the ELM, MZ, EZ, OPRS, and IZ bands have lost definition (white arrows) in dog PRA 3. Unilateral coloboma of the iris was diagnosed in 3 dogs aged 2, 6, and 7 years.

Fig 9. Geographic retinal dysplasia diagnosed in a 6-month-old female dog.

Fig 10. Multifocal retinal dysplasia with retinal folds diagnosed in a 1.5-year-old male dog.

Fig 11. Retinal layers with visible architecture.

Loss of definition of ELM band in dog diagnosed with SRADs.

Fig 12. Loss of definition of ELM, MZ, EZ, OPRS and IZ band in the tapetal fundus, in dog diagnosed with SARDs.