Blindness

Jump to... Pathogenesis Diagnosis Treatment Prevention Sequelae Sources

• Cause:
  • Intra-ocular disease (uveitis, cataract, glaucoma, retinal detachment, intra-ocular tumor; hypertensive retinal detachment is the most common).
  • Optic nerve disease (optic neuritis, optic nerve or perineural tumor, all rare in cat).
  • Intracranial disease (inflammatory disease or brain tumor, again both rare in the cat).
• It is important to localize where the lesion is occurring so that any specific treatment can be administered.
• Signs: obvious blindness, pupil dilation.
• Diagnosis: recognition of blindness, diagnosis of underlying disease.
• Treatment: treat underlying cause when possible.
• Prognosis: variable - may be reversible depending on cause.

• Cat obviously blind, bumping into objects, with or without ocular pain.
• Note that a cat with long-standing blindness will negotiate obstacles so well that it may be very difficult to assess vision apart from using an obstacle course.
• Also, cats with hypertension may have been blind in one eye for some time and it is only when the second retina detaches that a problem is noted.
• Pupil dilation and absent pupillary light reflex.

• Investigation of underlying disease may be costly and time consuming.

• See pathogenesis of uveitis , glaucoma , cataract , retinal detachment .

• Slow, progressive sight loss.
• Acute or peracute blindness.

• Obvious signs of visual impairment, eg bumping into objects.
• Behavioral changes, eg reluctant to go out in the dark.
• Timecourse of visual loss:
  • Slow with gradual retinal degeneration.
  • Fast with acute glaucoma, severe uveitis, retinal detachment.

• Poor performance on obstacle course.

Ophthalmoscopy

• Signs of glaucoma, uveitis, corneal edema, cataract.
• Signs of retinal degeneration: narrowing retinal vessels, tapetal hyper-reflectivity.
• Signs of retinal detachment - folds of retina within vitreous often with hemorrhages.
• Diagnosis of hypertensive retinopathy likely.

Ocular reflexes

• Pupillary light reflex (subcortical response).
• Dazzle reflex (subcortical response).
• Menace reflex (cortical response).

• Investigation of underlying disease.

Other

• Electroretinography - to detect retinal degeneration but this is much less commonly undertaken in the cat than the dog.

Imaging

• If ERG positive then consider MRI/CT to assess for intracranial mass or retrobulbar optic neuritis.
• Measure blood pressure.

• Diagnosis of underlying cause.

• Differentiate ocular, optic nerve and intracranial causes of blindness above.

• For hypertensive retinopathy treatment is Norvasc 0.625 mg/day.

• Monitor retinal health in retinal detachment ophthalmoscopically and blood pressure by doppler ultrasound.

• Examine cats ophthalmoscopically at every vaccination consultation to assess if a subclinical retinal detachment is occurring with a hypertensive cat.

• Blindness may be reversible depending on cause.

• Progressive or irreversible disease.

• Recent references from PubMed.
• Gelatt K N (1998) Visual disturbance - where do I look? JSAP 38, 328-335.

• Petersen-Jones S & Crispin S (2002) BSAVA Manual of Small Animal Ophthalmology. 2nd edn. British Small Animal Veterinary Association. ISBN 0 905214 54 4

• Dr Dennis E Brooks DVM PhD DipACVO, College of Veterinary Medicine, 2015 SW 16th Ave, University of Florida, PO Box 100126, Gainesville, FL 32610-0126, USA. Fax: 001 352 392 6125. E-mail: brooksd@mail.vetmed.ufl.edu.
• Dr David L. Williams MA VetMB CertVOphthal PhD MRCVS, Department of Clinical Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge CB3 0ES, UK.

Back to top
© Copyright Vetstream

FELIS DIS02681

---