1.7 The Red Eye

Question 1

Red eyelids DDx

skin, muscles, Meibomian glands and conjunctiva

Answer 1

• periocular dermatitis - several causes, some systemic and potentially severe
• meibomian glands - can become infected, inflamed or neoplastic

Question 2

Red third eyelid DDx

normally has some vasculature visible but minimal

Answer 2

• TEL hyperemia and swelling - ocular surface disease, orbital disease, TEL neoplasia
• TEL follicular proliferation- lymphoid follicles are (immune system) exist on TEL, responding to infections and foreign materials within the eye. If these immune cells become overstimulated (allergies, infections, etc.), the follicles can become enlarged and cause follicular conjunctivitis. Mainly present in the inner side, Usually accompanied by hyperemia
• TEL scrolled cartilage vs prolapse nictitans gland (cherry eye)- can be very similar clinically - manipulation may be required under topical anesthesia to differentiate both conditions

T shaped cartilage holds the third eyelid up against the eye - can curl and cause an outward fold

Accessory lacrimal gland (nictitans / TEL gland) produces up to 30% of the aqueous component of the tears - can prolapse and become inflamed

Question 3

Red conjunctiva DDx

mucous membrane of eyelids, third eyelid and sclera; vasculature minimal

Answer 3

• conjunctival hyperemia - Sign of ocular surface disease. With dichotomous division, appear superficial and move with the conjunctiva - Most evident in the fornixes

Question 4

Red episclera / sclera DDx

posterior tunic of globe; episclera (clear) sits atop the sclera (white)

Answer 4

• episcleral hyperemia - Sign of deeper ocular tissues disease (including intraocular) - No dichotomous division, deeper and does not move with the conjunctiva. Most evident close to the limbus

Question 5

Red cornea DDx

(epithelium, stroma, Descemet’s, endothelium)

Answer 5

• superficial corneal neovascularization (due to ulcerative keratitis or keratoconjunctivitis sicca)
• deep corneal neovascularization (due to uveitis or glaucoma)
• intracorneal hemorrhage (uncommon) - always associated with corneal neovascularization. Can be associated with systemic hypertension

Question 6

Red anterior chamber DDx

Answer 6

• hyphema (blood in anterior chamber)

due to inflammation (uveitis), trauma (penetrating or blunt), intraocular neoplasia, retinal detachment, glaucoma, congenital defect, systemic condition (hypertension, thrombopathy, coagulopathy, etc.)

Question 7

Red posterior chamber DDx

Answer 7

• vitreous hemorrhage

same as anterior chamber: due to inflammation (uveitis), trauma (penetrating or blunt), intraocular neoplasia, retinal detachment, glaucoma, congenital defect, systemic condition (hypertension, thrombopathy, coagulopathy, etc.)

Question 8

Red anterior uvea DDx

AKA the iris

Answer 8

• Uveal bleed
• Uveal tumor
• Engorgement of normal vascularization - most commonly secondary to uveitis
• formation of new vasculature over the iris surface - Histologically referred as pre-iridal fibrovascular membranes (PIFM) - Secondary to uveitis, intraocular tumor, retinal detachment or glaucoma

Question 9

Red posterior uvea DDx

AKA the retina

Answer 9

• Retinal detachment & retinal bleeds (seen as blood on tapetum)

Important: Some anatomical variations can ‘mimic’ retinal/choroidal bleeds

Normal anatomical variation: Some lightly pigmented animals can present a marked red reflexion of the ocular fundus due to lack of pigmentation in the posterior uvea and retinal pigmented epithelium

Question 10

Red retrobulbar space DDx

Answer 10

Any growing structure within the retobulbar space (inflammatory, infectious or neoplastic) will most like deviate the globe, as well as compromising the vascular return from the rest of orbital structures