Ophthalmic conditions represent approximately 3-5% of all veterinary presentations, yet missed or delayed diagnosis of ocular emergencies can result in permanent vision loss within hours. Acute glaucoma can cause irreversible retinal ganglion cell death in as little as 24-48 hours. Use the Eye Diagnostics AI for image analysis and the Ophthalmology Specialist for case discussions.
A complete ophthalmic examination should follow a consistent order, moving from least invasive to most invasive tests. Perform distance assessment first (in room lighting), then proceed to hands-on examination.
1. Distant observation: Assess symmetry, globe size and position, discharge, blepharospasm, and periocular swelling before touching the patient.
2. Menace response: A threatening hand gesture toward each eye should produce a blink. Tests CN II (optic) afferent and CN VII (facial) efferent pathways. Absent menace with intact PLR suggests cortical blindness.
3. Pupillary light reflex (PLR): Direct and consensual PLR tests CN II and CN III. Perform the swinging flashlight test to identify a relative afferent pupillary defect (RAPD/Marcus Gunn pupil), which indicates unilateral retinal or optic nerve disease.
4. Schirmer tear test (STT): Measure basal plus reflex tear production. Perform BEFORE applying any topical agents. Normal values: dogs ≥15 mm/min; cats ≥10 mm/min (less commonly performed). Values <10 mm/min in dogs indicate keratoconjunctivitis sicca (KCS).
5. Fluorescein stain: Detects corneal epithelial defects (ulcers). Fluorescein adheres to exposed corneal stroma but not intact epithelium or Descemet's membrane. A deep ulcer that retains stain at the base but not centrally (Descemet's membrane exposed) is a descemetocele, which is an emergency.
6. Tonometry: Measures intraocular pressure (IOP). Normal: 15-25 mmHg in dogs and cats. IOP >25 mmHg is suspicious for glaucoma; >30 mmHg is diagnostic in most contexts. Low IOP (<10 mmHg) suggests uveitis.
7. Slit lamp biomicroscopy: Magnified examination of anterior segment structures (lids, conjunctiva, cornea, anterior chamber, iris, lens).
8. Direct/indirect ophthalmoscopy: Fundic examination evaluates the optic disc, retinal vasculature, tapetum, and non-tapetal fundus.
These conditions require immediate recognition and either urgent treatment or same-day referral to save vision or the globe:
1. Acute glaucoma: IOP >30-40 mmHg with painful, red eye, dilated/fixed pupil, episcleral injection, corneal edema, and vision loss. Begin emergency medical therapy immediately: latanoprost 0.005% topically (one drop, contraindicated if lens luxation is suspected), dorzolamide/timolol topically, and mannitol 1-2 g/kg IV over 20-30 minutes. Refer urgently.
2. Proptosis (globe prolapse): Traumatic displacement of the globe anterior to the eyelids. Keep the cornea moist (saline-soaked gauze), prevent self-trauma (e-collar), and perform surgical globe replacement under general anesthesia as soon as possible. Prognosis depends on breed (better in brachycephalics), extraocular muscle integrity, and presence of hyphema or pupil dilation.
3. Deep/melting corneal ulcer: Corneal ulcers that extend beyond 50% stromal depth, or melting (malacic/liquefactive) ulcers that show gelatinous, soupy stroma. These are at risk of corneal perforation. Aggressive topical antibiotics (q1-2h), serum or EDTA drops (anticollagenase), atropine, and surgical referral for corneal grafting if needed.
4. Anterior lens luxation: The lens displaces into the anterior chamber, causing acute glaucoma and corneal endothelial damage. Common in terrier breeds (Jack Russell, Fox Terrier). Emergency IOP reduction followed by surgical lens extraction.
5. Hyphema (blood in anterior chamber): Can result from trauma, coagulopathy, retinal detachment, neoplasia (iris melanoma, lymphoma), or systemic hypertension. Rule out coagulopathy and systemic hypertension. Treat underlying cause; topical atropine for pain and to prevent posterior synechia.
Warning: Never apply latanoprost (a prostaglandin analogue) if anterior lens luxation is suspected. Latanoprost causes miosis, which can trap the luxated lens in the anterior chamber and worsen the emergency. In anterior lens luxation, use atropine to dilate the pupil and attempt to move the lens posteriorly.
| Condition | Key Features | Treatment |
|---|---|---|
| Keratoconjunctivitis sicca (KCS) | STT <10 mm/min, mucopurulent discharge, corneal vascularization | Topical cyclosporine or tacrolimus (lacrimostimulants), artificial tears |
| Entropion | Inward rolling of eyelid margin; corneal irritation; breed-related (Shar-Pei, Chow, Rottweiler) | Surgical correction (Hotz-Celsus procedure) |
| Cherry eye (nictitans gland prolapse) | Red, fleshy mass at medial canthus; common in young Bulldogs, Beagles, Cocker Spaniels | Surgical repositioning (pocket technique); DO NOT excise |
| Cataracts | Lens opacity; distinguish from nuclear sclerosis (normal aging, does not impair vision) | Phacoemulsification surgery; manage diabetic cataracts concurrently |
| Progressive retinal atrophy (PRA) | Bilateral, progressive vision loss (night blindness first); tapetal hyperreflectivity, vascular attenuation | No treatment; genetic testing available for breeding programs |
| Anterior uveitis | Painful eye, miosis, aqueous flare, low IOP, corneal edema | Topical corticosteroids or NSAIDs, atropine; identify and treat underlying cause |
Breed awareness helps anticipate and screen for ophthalmic conditions. Cavalier King Charles Spaniels are predisposed to keratoconjunctivitis sicca, cataracts, and corneal dystrophy. Cocker Spaniels are prone to glaucoma, cataracts, and cherry eye. Pugs and other brachycephalic breeds are at high risk for corneal ulceration due to shallow orbits, lagophthalmos, and decreased corneal sensitivity. Siberian Huskies are predisposed to cataracts and corneal dystrophy. Labrador Retrievers have increased risk of PRA and cataracts.
Referral is recommended for: acute glaucoma unresponsive to initial medical therapy, deep or melting corneal ulcers requiring surgical intervention, anterior lens luxation, cataracts (surgical candidates), intraocular neoplasia, cases requiring electroretinography (ERG) before cataract surgery, complex uveitis unresponsive to standard therapy, and any condition where vision can be preserved with specialist intervention.
When referring ophthalmic emergencies, continue topical medications during transport. Keep fluorescein stain results, IOP measurements, and STT values documented to provide the ophthalmologist with baseline data. Prevent self-trauma with an Elizabethan collar during transport.
- Always perform the eye exam in order: STT first (before any drops), then fluorescein, then tonometry.
- Five ophthalmic emergencies: acute glaucoma, proptosis, deep/melting ulcer, anterior lens luxation, hyphema.
- Acute glaucoma causes irreversible vision loss in 24-48 hours; begin emergency treatment immediately.
- Never use latanoprost if anterior lens luxation is suspected; never excise a prolapsed nictitans gland.
- Differentiate cataracts (pathologic lens opacity) from nuclear sclerosis (normal aging change).
- Refer promptly when specialist intervention can preserve vision.