Few ocular diseases specific to cats: corneal sequestrum, eosinophilic keratitis, malignant glaucoma.

Orbit

• Retrobulbar neoplasia, abscess/inflammation, trauma (fracture)
• Clinical signs
• Exophthalmos
• Deviation globe
• Protrusion third eyelid
• Conjunctival hyperemia/chemosis +/- corneal lesions
• Orbital neoplasia
• 90% malignant
• Squamous cell carcinoma most common
• Lymphosarcoma second most common
• Diagnostic approach
• Physical and ocular exam (fluorescein test)
• Retropulsion of the globes
• Exploration of the buccal cavity
• Imaging: radiographs, ultra-sound
• Therapeutic approach
• Temporary treatment until the determination of the cause
• Pain management
• Protection of the globe (lubrification, tarsorrhaphy) +/- treatment of the corneal lesions
• If obvious cause→start etiologic treatment
• Abscess: sys AB +/- drainage, sys NSAIDs
• Fracture: sys NSAIDs +/- sys AB
• Globe proptosis
• Severe trauma
• Clinical signs
• Proptosis=palpebral edge behind the equator of the globe
• Conjunctival oedema (chemosis) and hyperemia
• Lateral strabismus
• Corneal and +/- intra-ocular lesions
• Diagnostic approach and prognosis
• Pupils and PMR (fixed mydriasis: bad prognosis, myosis: better prognosis)
• Skull bones integrity
• Globe integrity (rupture: bad prognosis)
• Cornea integrity (rupture: bad prognosis)
• Extra-ocular muscles (rupture of three of the extra-oc muscles: bad prognosis)
• Intra-ocular lesions (hyphema: bad prognosis, risk of glaucoma)
• Therapeutic approach
• Main goal: to preserve the globe
• Pain management
• Keep the cornea moistened/lubricated
• General anesthesia (verify the status of the animal)
• Lateral canthotomy (+/-)
• Clean the eye (diluted betadine 1:50)
• Replace the globe or enucleate (i.e. rupture of the globe, the optic nerve or three extra-ocular muscle)
• Tarsorrhaphy (4/0–5/0, U sutures, “stents”)
• E-collar
• Medical treatment: systemic SAIDs or NSAIDs, topical AB
• Sequelae
• Lateral strabismus (100%)
• Blindness (80%)
• KCS
• Phthisis bulbi
• Glaucoma
• Corneal scar

Eyelid

• Eyelid agenesis
• Portion of the temporal upper eyelid fails to develop
• Concurrent congenital defects
• PPMs
• Optic disk colobomas
• Lenticonus
• Microphthalmos
• Choroidal hypoplasia
• Clinical signs
• Absence of palpebral edge
• Conjunctival hyperemia
• Corneal fibrosis and neovascularization caused by corneal exposure and trichiasis
• Treatment
• Repair the defect (rotational eyelid pedicle flap, H-plasty)
• Cryotherapy or electrolysis for the trichiasis
• Eyelid tumors of the cat
• 2% of the cat diseases are tumors and 2% of the cat tumors affect the eye and its adnexa
• More aggressive and malignant than those in dogs
• Types of eyelid tumors in cats: squamous cell carcinoma, fibrosarcoma, lymphosarcoma, adenoma/adenocarcinoma, mastocytoma, round cell tumor
• Squamous cell carcinoma
• Most common eyelid neoplasm
• Increased incidence in white, aged cats
• Slowly progressive, ulcerative lesions
• Late metastasis
• Diagnosis: based on age, clinical signs, cytologic or histologic examination
• Treatment: surgical excision with wide margins combined with radiation therapy or cryotherapy or hyperthermia or CO₂ laser

Conjunctiva, Nictitating Membrane, Cornea

• Conjunctivitis
• Common
• Often primary infections
• Herpesvirus
• Chlamydophila (Chlamydia)
• Mycoplasma
• Feline herpesvirus type 1 (FHV-1)
• Primary infection
• Acute, conjunctival-respiratory infection ± corneal ulcer
• Neonatal, adolescent cats
• Bilateral serous ± mucoid/mucopurulent ocular discharge
• Bilateral hyperemic conjunctiva (chemosis usually not prominent)
• Primary infection usually resolves in 10–14 days (∼80% latently infected)
• Conjunctivitis/herpesvirus
• Young adult cats
• Usually no respiratory infection
• Bilateral
• Intermittent blepharospasm
• Hyperemic conjunctiva ± corneal lesions (epithelial ulcer)
• Ocular discharge mild, serous
• Chronic and/or recurrent
• Factors inducing inflammatory episodes: stress, usage of corticosteroids
• Herpesvirus—diagnosis
• Clinical signs; best to test during active disease
• Lots of viral shedding
• Immunofluorescent antibody testing of conjunctival scrapings
• Fluorescein stain after collecting samples to avoid false positives
• Lacks sensitivity
• PCR very sensitive; may cause problem with interpretation
• Herpesvirus—treatment
• Topical antibiotics (tetracycline, chloramphenicol, erythromycin)—control secondary bacterial infections
• Antivirals (mainly for keratitis)
• Steroids contra-indicated
• Prophylactic or maintenance treatment
• Oral L-lysine: decrease frequency and severity of the inflammatory episodes (500 mg BID PO adult; 250 mg BID kitten)
• Interferon: prophylactic effects not proven
• Chlamydia psittaci (Chlamydophila felis)
• Unilateral/bilateral
• Conjunctival hyperemia
• Chemosis ++
• Serous ocular discharge
• No corneal involvement
• Cytology: inclusion bodies cytoplasm
• Treatment: tetracycline topically
• Mycoplasma felis
• Pathogenic role unclear
• Unilateral/bilateral conjunctivitis
• Conjunctival follicles, pseudomembranes
• No corneal involvement
• Cytology: inclusion bodies cytoplasm
• Treatment: susceptible to most antibiotics (tetracycline, erythromycin, chloramphenicol)
• Corneal ulcers
• Corneal ulcers from bacteria—uncommon in cats
• Herpetic keratitis (FHV-1) +/- ulcerative
• Traumatic lacerations—common
• Corneal foreign bodies—common
• General comments
• Making the diagnosis of a corneal ulcer is critical for the welfare of the patient
• It is the difference between sight and blindness, or a small scar and a large scar
• Assume ulcers will get worse—treat aggressively
• Melting ulcers
• Corneal degeneration due to proteases is referred to as “melting”
• Ulcers in which proteases are active have a grayish-gelatinous appearance which must be distinguished from corneal edema
• The action of proteases is potentiated by topical corticosteroids
• Herpetic keratitis
• Herpes—only known viral cause of keratitis in cats
• Young animals—keratitis=extension of primary conjunctival infection; adults—keratitis=reactivation of latent virus
• Acute keratitis
• Dendritic ulcers
• Mild-moderate conjunctivitis
• Serous-mucopurulent discharge
• Chronic keratitis
• May have stromal edema
• Fibrosis
• Superficial vascularization
• Diagnosis
• Blepharospasm
• Photophobia
• Epiphora
• Eyelid swelling
• Conjunctival swelling
• Sign of anterior uveitis associated
• Myosis, fibrin, hypopyon
• Corneal edema
• Rough depressed area
• Missing outer layer of cornea
• Evaluation at distance (discharge, symmetry): menace, dazzle, blinking, pupil size
• PLRs, slit lamp examination
• Schirmer tear test
• Corneal culture
• Fluorescein stain
• Rose bengal
• Corneal scraping for cytology
• Fluorescein test (detects a corneal epithelial, stromal ulcer (stain stroma not epithelium))
• Seidel test
• All red, inflamed or painful eyes should be routinely stained with fluorescein
• Look for an underlying cause (KCS, distichia, trichiasis, entropion)
• Treatment
• Medical and/or surgical ... according to whether
• Infected
• Deep
• Melting
• Inflamed (associated uveitis)
• Medical treatment
• Determine and eliminate etiology (e.g. KCS, entropion, infection)
• Prevent or treat infection (broad-spectrum topical antibiotics, culture and sensitivity tests)
• Prevent progression (melting)
• Treat uveitis
• Topical atropine cycloplegia/mydriasis
• Topical NSAIDs (careful)
• No steroids
• Prevent self-trauma: E-collar
• Herpetic keratitis +/- ulcerative
• Antimicrobial treatment
• Antibiotics
• Antiviral agents: good response in acute cases, poor response in chronic cases idoxuridine 1%, acyclovir, trifluridine 1%, ganciclovir, famciclovir
• Treatment of a superficial herpetic ulcer
• Similar to a superficial corneal ulcer (AB+antiviral)
• It can look like an indolent ulcer
• It can be debrided
• Keratotomy contra-indicated
• Treatment anti-inflammatories
• Corticosteroids: contra-indicated as they can activate the viral replication
• NSAIDs: can be used with caution, either topically (diclofenac) or systemically (meloxicam)
• Cyclosporine A
• Surgical treatment
• Conjunctival graft (or biomaterial graft)
• Corneal sequestrum
• Degeneration of collagen
• Accumulation of brown pigment
• Varying intensity
• Unknown etiology
• Ocular irritation (chronic herpetic keratitis, entropion, traumatic ulcers)
• Himalayan, Persian, and Burmese cats are predisposed
• Treatment—keratectomy: removal of the sequestrum
• Keratectomy alone: risk of recurrence
• Keratectomy and conjunctival graft→rare recurrences
• Keratectomy and corneo-conjunctival transposition→rare recurrences
• Eosinophilic keratitis
• Proliferative corneal mass
• White to pink
• Irregularly surfaced
• Vascularized
• Most commonly originates from the temporal or nasal limbus, may involve adjacent conjunctiva and nictitans
• Diagnosis
• Cytology of corneal scrapings
• Eosinophils, mast cells, lymphocytes, plasma cells
• Therapy
• Topical corticosteroids
• Topical 1% cyclosporine A
• Systemic megestrol acetate (side effects: diabetes)
• Recurrences are common

Uvea

• Uveitis
• Anterior uveitis ± chorioretinitis common in cats
• Causes
• Trauma
• Infectious (common)
• Viral: FeLV, FIV, FIP
• Toxoplasmosis
• Fungal
• Cryptococcus
• Blastomycosis
• Histoplasmosis
• Coccidioides
• Candida
• Aspergillus
• Neoplastic
• Diffuse iridal melanoma
• Primary ocular sarcoma
• Primary ciliary body adenomas/adenocarcinomas
• Metastatic uveal neoplasms
• Lens (cataract-induced, lens luxation)
• Immune-mediated
• Idiopathic (70%)
• Clinical signs
• Blepharospasm
• Epiphora
• Photophobia
• Conjunctival hyperemia
• Corneal edema
• Flare/hyphema/hypopyon/fibrin
• Hypotony
• Myosis
• Hyperemia of the iris
• Iris color change
• Keratic precipitates
• Synechiae
• Feline infectious peritonitis
• Coronavirus infection—often in younger cats
• Uveitis is more common with the non-effusive form of FIP
• Ocular lesions may be the only sign of infection or precede systemic signs
• Diagnosis
• Anterior>posterior uveitis
• Aqueous flare, keratic precipitates
• Fibrin and/or hypopyon in AC
• Chorioretinitis, retinal detachment
• Retinal vasculitis, optic neuritis
• Elevated total plasma protein
• Polyclonal gammopathy
• Toxoplasmosis
• Ocular lesions plus generalized disease
• Hematologic spread of sporozoites
• Multiplication of tachyzoites in ocular tissues
• Relatively mild anterior uveitis
• Multifocal retinitis or retinochoroiditis
• Diagnosis: IgG/IgM titers
• FeLV
• Anterior uveitis
• Chorioretinitis
• Lymphoma-related uveitis
• Anterior lymphoma
• Chorioretinal masses
• Retinal detachment
• Secondary glaucoma
• Uveitis treatment
• Mydriatics (1% atropine ointment)
• Anti-inflammatories
• Topical SAIDs: acetate forms of prednisolone or dexamethasone
• Systemic SAIDs (with caution)
• Topical and systemic NSAIDS
• Antibiotics (toxoplasmosis—clindamycin 12.5 mg/kg, BID, 28 days)
• Antifungals
• Uveal tumors
• Diffuse iridal melanoma
• Slowly progressive pigmentation of iris
• Can obstruct iridocorneal angle causing glaucoma
• Late metastasis (liver, lungs)
• Enucleation if
• Uveitis/glaucoma
• Large pigmented area
• Pigmented area not flat
• Irido-corneal angle affected, change in pupil’s shape
• Change in pupil’s mobility

Glaucoma

• Causes
• Primary glaucomas
• Open/normal angle, +/- collapsed cleft (Siamese)
• Narrow/closed angle (chronic)
• Secondary glaucomas (most common in cats)
• Uveitic (chronic anterior uveitis)
• Lens luxations (trauma/age)
• Phacolytic/phacoclastic uveitis (lens perforation), hyphema (rare)
• Intraocular neoplasia (primary/secondary neoplasms)
• Clinical signs
• Often very discreet
• Sometimes only elevated IOP and anisocoria/mydriasis, buphthalmia
• Treatment
• Correct underlying cause when possible
• Mannitol in acute cases, IOP >50 mm Hg
• Carbonic anhydrase inhibitors: dorzolamide 2% TID
• Beta blockers: timolol 0.5% BID
• Analogs of prostaglandins: not effective in cats
• Laser cyclophotocoagulation

Lens

• Lens cataract
• Primary: rare in cats
• Secondary to: uveitis, trauma, glaucoma, lens luxation, diabetes (rare)
• Congenital: rare
• Cataract surgery
• By phacoemulsification
• Intra-ocular lens: 53 D
• Outcomes even better than in dogs

Posterior Segment

• Tapetal fundus—larger and brighter than the dog
• Non-tapetal fundus—related to hair coat color
• Retinal vasculature—three large pairs of arteries and veins
• Optic nerve head: small and round
• Nutritional retinal degeneration
• Taurine deficiency
• Identical to feline central retinal degeneration
• Cats fed dog food or “homemade” diets
• Initial lesion=hyperreflectivity of area centralis
• Chronic deficiency severe retinal degeneration and irreversible blindness
• Baytril toxicity
• Safe dose 2.5 mg/kg BID PO
• Original dose: 11 mg/kg PO q 24 h
• Rod-cone degeneration in Abyssinian
• Begins 1.5–2 years of age
• Complete degeneration in 2–4 years
• Inflammation (chorioretinitis)
• FIP
• FeLV
• Toxoplasmosis
• Fungi
• Neoplasia (primary or secondary)
• Hypertensive retinopathy
• Old cats
• Ocular signs
• Sudden blindness
• Dilated or poorly to unresponsive pupils
• Tortuous retinal vessels, serous retinal detachment
• Retinal and vitreal hemorrhages
• Systemic signs
• Systolic blood pressure >160 mm Hg
• Cardiomegaly
• Renal disease
• Hyperthyroidism
• Hyperglycemia
• Treatment
• Treat underlying disease
• Calcium channel blocker, amlodipine 0.625 mg/cat/day
• Retinal folds and detachments
• Separation sensory/epithelial retina
• Congenital
• Secondary to other diseases
• Causes: hypertension, hyperviscosity, trauma, infections, neoplasms

Conclusions

• Take care of the eyes! They can reveal the presence of a systemic disease. Important to understand where, how, and why.
• Important aspects of the treatment:
• Pain management.
• Preservation of the vision.
• Esthetic appearance of the animal.