Administration of drugs to the eye

1. Eye drops and eye ointments are instilled into the pocket formed by gently pulling down the lower eyelid. For eye drops, one drop is all that is needed as long as instillation is successful. For eye ointments, a small amount is applied similarly; the ointment melts rapidly and blinking helps to spread it.

2. When two or more different drops are required at the same time of day, the patient should leave an interval of 5 minutes between drops to avoid dilution and overflow. Also to use ointment preparations 5 minutes after drops.

3. Certain preparations included within this chapter of the formulary are unlicensed and marked with *. These products will be ordered specially and are not stocked; therefore a delay in obtaining stocks may be incurred. These 'specials' may be supplied when clinical need for the individual patient demands, given no commercial alternative is available. Specials are often very costly.

Administration aids: Eye drop dispensers are available to aid the instillation of eye drops especially amongst the elderly, visually impaired, arthritic, or otherwise physically limited patients. They can be purchased from most community pharmacies or prescribed on FP10 prescription. Please refer to the Drug Tariff for details - Appliances: Eye Drops Dispensers.

Preservatives and sensitisers:

1. Long-term administration of preservative containing eye drops may cause ocular irritation.

2. RCHT Eye Unit offer the following recommendations for when to use preservative free treatments:

• the patient has a proven allergy to the preservative
• frequent use of the drops - six or more time a day (long-term use)
• the patient is wearing a soft contact lens or bandage lens at the time of instillation, on specialist advice
• after a corneal transplant in selected cases, depending on indication, and in cases where the cornea is compromised, on specialist advice

3. All Minims^® and other single use products are preservative free.

Beta-blockers

1. There is no evidence to show that 0.5% timolol is more effective than 0.25% and so to avoid side effects weaker dose is recommended.

2. Systemic absorption may follow topical application; therefore eye drops containing a beta-blocker are contra-indicated in patients with bradycardia, heart block or uncontrolled heart failure.

3. Beta-blockers, even those with apparent cardioselectivity, should not be used in patients with asthma or a history of obstructive airways disease, unless no alternative treatment is available. In such cases the risk of inducing bronchospasm should be appreciated and appropriate precautions taken.

4. Beta-blocker eye drops should be avoided in patients receiving oral verapamil.

Prostaglandin analogue

1. Prostaglandin analogues are indicated for open-angle glaucoma and ocular hypertension and have been licensed for first line use. Although more expensive they are more effective than topical beta blockers and are generally considered first line treatment.

2. Patients should be monitored for any changes to eye colouration since an increase in the brown pigment in the iris may occur. Particular care is required in those with mixed coloured irides and those receiving treatment to one eye only. Patients should be counselled regarding this side effect.

3. Latanoprost currently has a comparatively low incidence of reported side effects though uveitis and macular oedema have been reported.

4. Tafluprost is only for use in patients who cannot tolerate currently available prostaglandin preparations due to proven sensitivity to the preservative benzalkonium chloride.

Carbonic anhydrase inhibitors and systemic drugs

1. Carbonic anhydrase inhibitors are sulphonamide related drugs and may give rise to associated side effects especially with systemic treatment eg blood disorders.

2. Topical carbonic anhydrase inhibitors are licensed for use in patients resistant to beta-blockers or those in whom beta-blockers are contra-indicated. They can be used alone or as an adjunct to a topical beta-blocker.

3. Acetazolamide is used as parenteral or oral therapy for acute glaucoma. Its side effects include paraesthesia, general malaise / fatigue, dizziness, electrolyte imbalance, and depression.

4. Brinzolamide is the first choice treatment for new patients.

Miotics

1. A darkly pigmented iris may require a higher concentration of pilocarpine or more frequent administration. Care should be taken to avoid over dosage.

2. Fundus examination is advised before starting treatment with a miotic.

3. Intra-ocular pressure and visual fields should be monitored in those with primary open angle glaucoma and those receiving long-term treatment with a miotic.

4. Miotics should be used with caution in cardiac disease, hypertension, asthma, peptic ulceration, urinary-tract obstruction and Parkinson's Disease.

5. Miotics are contra-indicated in conditions where pupillary constriction is undesirable such as acute iritis, anterior uveitis and some forms of secondary glaucoma.

6. Miotics should be avoided in acute inflammatory disease of the anterior segment.

Sympathomimetics

1. Brimonidine is a selective alpha2-adrenoceptor stimulant, licensed for use in those patients who are unresponsive to beta-blockers or if beta-blockers are contra-indicated.

2. There is a high (20%) incidence of ocular reactions with long term use of brimonidine, for example sore red eyes.

3. Adrenaline and dipivefrine (Propine^®) are not included in this formulary. Their use has reduced due to associated systemic and ocular side effects.