Corticosteroids

The anti-inflammatory effects of corticosteroids are based upon their ability to suppress capillary dilatation, vascular exudation, leucocyte migration, and immunosuppression regardless of the causative agent. In chronic conditions they inhibit neovascularisation and fibroblastic activity in the eye. This may be useful in preventing scarring and pigment deposition in the cornea but disadvantageous by retarding healing. In general, topical preparations readily penetrate the cornea. The ester of the corticosteroid used influences corneal penetration, for example, prednisolone acetate has a superior corneal penetration to prednisolone sodium phosphate.

Topical corticosteroids are particularly useful in the treatment of uveitis, various specific and non-specific inflammatory disorders of the cornea, such as chronic superficial keratitis (CSK, pannus) in the German Shepherd dog. They also assist in the reduction of post-surgical inflammation, such as that following cataract or lens extraction. Following administration, therapeutic levels remain in the eye for only about three hours and this may necessitate frequent application to prevent treatment failure. Low levels of systemic absorption will occur after frequent application of topical steroids and this should be considered in animals of low body-weight and those with metabolic diseases such as diabetes mellitus. Topical corticosteroids should not be used in the presence of corneal ulceration; systemic NSAIDs should be considered. Corticosteroids may be used in the presence of glaucoma in animals but care should obviously be taken in the differential diagnosis of a ‘red eye’. All corticosteroids should be used with care in pregnant animals because there is a slight risk of intra-uterine growth retardation.

Subconjunctival injections may augment, or replace, topical instillation. Preparations of methylprednisolone acetate or triamcinolone acetonide may be effective for up to three weeks. Their use may sometimes be effective for owners experiencing difficulty in applying drops. Subconjunctival therapy may be used for the treatment of bovine iritis. Beta-methasone sodium phosphate (2 mg) or dexamethasone sodium phosphate (2 mg) every 3 days or methylprednisolone (10 to 20 mg, depot injection) every 7 to 14 days may be administered by subconjunctival injection for the treatment of inflammatory ocular conditions in horses. However, subconjunctival granulomas, plaques, or mineralisation can occur at the injection site. It is recommended that specialist advice be sought before using subconjunctival corticosteroid treatment in equines. Care must be taken with the use of topical corticosteroids in horses because the alteration in ocular micro-environment can predispose to fungal infections. Similar caution must be exercised in cats with suspected herpetic keratitis because local immunosuppression caused by the corticosteroid can allow recrudescence of the herpes virus. The use of systemic corticosteroids for ophthalmic therapy is limited because lower ocular concentrations are achieved than with topical application. However, systemic therapy may be useful for idiopathic partial serous retinal detachments, posterior uveitis, and optic neuritis. There is an association between cataractogenesis and steroid therapy in humans but this has not been described in animals. The adverse effects of prolonged administration of systemic corticosteroids may be minimised by alternate day therapy. Equine recurrent uveitis (periodic ophthalmia) is a disease of horses resulting in recurrent photophobia, lacrimation, conjunctival injection, corneal changes (such as oedema and vascularisation), hypopyon, miosis, synechiation, and even blindness due to extensive synechiae, cataract formation, or phthisis bulbi. Some forms of the disease have been linked to Leptospira infection, although in many instances the aetiology remains obscure. Treatment consists of topical and possibly subconjunctival corticosteroids, NSAIDs, and if bacterial infection is suspected, systemic antibacterials. Topical atropine is used to achieve a mid-dilated pupil.

BETAMETHASONE

Indications. See notes above

Contra-indications. Corneal ulceration, fungal or viral infections, see notes above

Warnings. Care in pregnant animals

Dose: Apply every 2-3 hours

Prescription-only medicine:® Betnesol (Celltech) UK

Drops (for eye, ear, or nose), betamethasone sodium phosphate 0.1%

Eye ointment, betamethasone sodium phosphate 0.1%

Prescription-only medicine: ® Vista-Methasone (Martindale) UK Eye drops, betamethasonesodium phosphate 0.1%

DEXAMETHASONE

Indications. See notes above

Contra-indications. Corneal ulceration, see notes above

Warnings. Care in pregnant animals

Dose: Apply every 2-3 hours

Prescription-only medicine:® Maxidex(Alcoa) UK

Eye drops, dexamethasone 0.1%, hypromellose 0.5%

Prescription-only medicine: ® Minims Dexamethasone (Chauvin) UK Eye drops, dexamethasone sodium phosphate 0.1%

FLUOROMETHOLONE

Indications. See notes above

Contra-indications. Corneal ulceration, see notes above

Warnings. Care in pregnant animals

Dose: Apply 4 times daily

Prescription-only medicine: ® FML (Allergan) UK

Eye drops, fluorometholone 0.1%, polyvinyl alcohol 1.4%

PREDNISOLONE

Indications. See notes above

Contra-indications. Corneal ulceration, see notes above

Warnings. Care in pregnant animals

Dose: Apply 4 times daily

Prescription-only medicine: ® Pred Forte (Allergan) UK Eye drops, prednisolone acetate 1%

Prescription-only medicine:® Predsol (Celltech) UK

Drops (eye drops or ear drops), prednisolone sodium phosphate 0.5%

Prescription-only medicine: ® Minims Prednisolone (Chauvin) UK

Eye drops, prednisolone sodium phosphate 0.5% (single use)

RIMEXOLONE

Indications. Treatment of local inflammation

Warnings. Care in pregnant animals

Dose: Apply 1 drop 2-4 times daily for up to 4 weeks. May be used more frequently for severe uveitis

Prescription-only medicine:® Vexol (Alcon) UK Eye drops, rimexolone 1%

COMPOUND CORTICOSTEROID AND ANTIBACTERIAL OPHTHALMIC PREPARATIONS

Preparations containing antibacterial and glucocorticoid agents in combination can be useful in cases of infected inflammatory processes such as bacterial keratitis, and for prophylaxis, for example following intra-ocular surgery where control of inflammation is important but a risk of infection also exists. A specific diagnosis and rationale for combination therapy should always be established.

Indications. See notes above

Contra-indications. Corneal ulceration

Warnings. Care in pregnant animals

Dose: See preparation details

Prescription-only medicine:® Maxitrol (Alcoa) UK

Eye drops, dexamethasone 0.1%, hypromellose 0.5%, neomycin (as suifate) 0.35%, polymyxin B suifate 6000 units/mL

Dose: Apply 4 times daily

Prescription-only medicine:® Maxitrol (Alcon) UK

Eye ointment, dexamethasone 0.1%, neomycin (as suifate) 0.35%, polymyxin B suifate 6000 units/g

Dose: Apply 3 times daily

Prescription-only medicine:® Vista-Methasone N (Martindale) UK

Eye drops, betamethasone sodium phosphate 0.1%, neomycin suifate 0.5%