Evaluation of patients with decreased vision or blindness

Animal Welfare Considerations and Ethical Dilemmas Inherent in the Euthanasia of Blind Canine Patients

Simple Summary

Although many dogs with blindness diagnosis can reach a similar age compared to those not affected, often the owners require euthanasia of their animals. This choice leads to conflicting moral principles relating to what is better for the animal and the owner. This article discusses the suitability of euthanasia in blind dogs. To better assess factors influencing the choice of euthanasia, four different scenarios were constructed that described various situations regarding the animal’s aptitude, pet owner, and veterinarian relations.

Abstract

In dogs, several primary or secondary diseases affecting the ocular structures may cause blindness. In cases where the visual impairment is not associated with severe systemic involvement and the animal can still have, predictably, a good “long-term” quality of life, the veterinarian should inform the owner about the differences between humans and animals, concerning the type of visual perception. In the light of the daily findings in veterinary clinic practice, the Authors report four different scenarios with conflicting views between veterinarians and owners about the euthanasia request for a blind dog. They underline how the diagnosis of incipient or already established blindness in dogs can sometimes lead to an inappropriate request for euthanasia.

Efficacy of the use of a colorimetric pupil light reflex device in the diagnosis of fundus disease or optic pathway disease in dogs

The aim of this study was to determine the efficacy of a colorimetric pupil light reflex (PLR) device (Melan-100(®), U.S.A.) in dogs with sudden acquired retinal degeneration syndrome (SARDS; 16 cases), progressive retinal atrophy (PRA; 10 cases) and optic pathway disease (6 cases). The colorimetric device detected PLR abnormality in 32, 16 and 9 eyes with SARDS, PRA and optic pathway disease, respectively, whereas white light detected PLR abnormality in 18, 11 and 9 eyes with SARDS, PRA and optic pathway disease, respectively. SARDS dogs displayed miosis, while optic pathway disease dogs displayed mydriasis in a blue light examination. Thus, colorimetric PLR may be a useful method for determining whether electroretinography (ERG) or magnetic resonance imaging (MRI) should be performed for dogs with acute blindness.

Acute postretinal blindness: ophthalmologic, neurologic, and magnetic resonance imaging findings in dogs and cats (seven cases)

OBJECTIVE

To describe the ophthalmologic, neurologic, and magnetic resonance imaging (MRI) findings of seven animals with acute postretinal blindness as sole neurologic deficit.

METHODS

Medical records were reviewed to identify dogs and cats with postretinal blindness of acute presentation, that had a cranial MRI performed as part of the diagnostic workup. Only animals lacking other neurologic signs at presentation were included. Complete physical, ophthalmic, and neurologic examinations, routine laboratory evaluations, thoracic radiographs, abdominal ultrasound, electroretinography, and brain MRI were performed in all animals. Cerebrospinal fluid analysis and postmortem histopathologic results were recorded when available.

RESULTS

Four dogs and three cats met the inclusion criteria. Lesions affecting the visual pathways were observed on magnetic resonance (MR) images in six cases. Location, extension, and MRI features were described. Neuroanatomic localization included: olfactory region with involvement of the optic chiasm (n = 4), pituitary fossa with involvement of the optic chiasm and optic tracts (n = 1), and optic nerves (n = 1). Of all lesions detected, five were consistent with intracranial tumors (two meningiomas, one pituitary tumor, two nasal tumors with intracranial extension), and one with bilateral optic neuritis that was confirmed by cerebrospinal fluid analysis. Histologic diagnosis was obtained in four cases and included one meningioma, one pituitary carcinoma, one nasal osteosarcoma, and one nasal carcinoma.

CONCLUSIONS

Central nervous system (CNS) disease should be considered in dogs and cats with acute blindness, even when other neurologic deficits are absent. This study emphasizes the relevance of MRI as a diagnostic tool for detection and characterization of CNS lesions affecting the visual pathways.