acute blindness Flashcards
(12 cards)
1
Q
What are the four main types of lesions that can cause acute blindness?
A
- Lesions that produce opacification of the clear ocular media (e.g., cataracts, severe uveitis, intraocular bleeding)
- Lesions that cause failure of the retina to process the image (e.g., retinal detachment, degeneration)
- Lesions that impede message transmission through the visual pathways (e.g., glaucoma, optic neuritis, chiasmatic tumours)
- Lesions affecting final image processing in the visual cortex (e.g., cerebral hypoxia)
2
Q
List causes of acute blindness with ocular signs.
A
- Uveitis
- Intraocular bleeding
- Glaucoma
- Diabetic cataracts
- Retinal detachment (bullous, regmatogenous, traction, dialysis)
- Hypertensive retinopathy
- Drug-induced retinal toxicity
- Optic neuritis (with papillitis)
3
Q
List causes of acute blindness without ocular signs.
A
- Sudden Acquired Retinal Degeneration Syndrome (SARDS)
- CNS diseases (e.g., infections, neoplasia, encephalopathies, head trauma, nutritional/toxic causes, cerebrovascular accidents, cortical blindness post-anesthesia or seizures)
4
Q
How is acute blindness diagnosed?
A
- Systematic clinical approach
- Thorough history, physical, and ophthalmic examination
- Visual tests: menace response, cotton ball test, visual placement, obstacle course
- Ophthalmoscopy, PLRs, ERG, and advanced imaging (MRI, CSF analysis) as needed
5
Q
Describe retinal detachment and its types.
A
- Bullous RD: subretinal fluid causes retina to balloon (e.g., chorioretinitis, hypertension)
- Rhegmatogenous RD: retinal tear allows vitreous leakage beneath retina (e.g., cataract, lens luxation)
- Traction RD: vitreous pulls on retina (e.g., organizing hemorrhage)
- Dialysis: peripheral retina completely torn
- Diagnosis via funduscopic exam; vision impairment depends on extent of detachment
6
Q
How should diabetic cataracts be managed?
A
- Develop rapidly and are bilateral
- Can cause lens swelling, rupture, phacoclastic uveitis, secondary glaucoma
- Prompt referral for cataract surgery (phacoemulsification) recommended
7
Q
What are the clinical signs and treatment options for hypertensive retinopathy?
A
- Clinical signs: retinal arterial tortuosity, hemorrhages, edema, papilledema, hyphaema, glaucoma
- Diagnosis: non-invasive BP measurement
- Treatment: address underlying cause and control hypertension
- Medications: Amlodipine (cats/dogs), ACE inhibitors (dogs)
- Prognosis good if treated early; retina degeneration may start within a week
8
Q
What are the characteristics and management of steroid-responsive retinal detachment in dogs?
A
- Bilateral bullous RD with no identifiable cause
- Suspected immune-mediated; treat with systemic steroids after excluding infections
- Early treatment critical; may result in reattachment and vision return
9
Q
Describe the signs and prognosis of drug-induced retinal toxicity.
A
- Enrofloxacin (cats): retinal degeneration, tapetal hyperreflectivity, vessel attenuation, ERG extinguished, usually permanent blindness
- Ivermectin: can cause blindness with or without CNS signs, papilledema, retinal folds; ERG changes reversible within 2–10 days
10
Q
What are the diagnostic and clinical features of SARDS?
A
- Sudden, permanent blindness with no early fundus changes
- Mydriasis with variable PLRs
- ERG is non-recordable (differentiates from CNS blindness)
- Affects middle-aged to elderly, often overweight, female spayed dogs
- Systemic signs suggest hyperadrenocorticism; no definitive treatment available
11
Q
What causes blindness due to lesions in the visual pathways (e.g., optic neuritis)?
A
- Optic neuritis: acute blindness, fixed dilated pupils
- Papillitis detectable on ophthalmoscopy
- Retrobulbar optic neuritis: normal fundus, use ERG for diagnosis
- Causes: infections, inflammation, trauma, toxins, neoplasia, vascular and idiopathic
12
Q
What is the recommended diagnostic approach for suspected optic neuritis or CNS disease?
A
- Neurological exam
- Routine labs
- CSF analysis
- MRI to localize lesion and guide treatment
