Chapter 15: Medicines optimization: ensuring quality and safety
Skip chapter table of contents and go to main content
Ophthalmic administration
Definition
Ophthalmic administration involves dosage forms introduced into the eye for local effects (e.g. to treat infections), to dilate or constrict the pupil, or to treat eye conditions such as glaucoma (Potter and Perry [289]).
Related theory
The topical route is the most popular way to introduce drugs into the eye in the form of eye drops or eye ointment. Most types of drop are instilled into the inferior fornix (the pocket formed by gently pulling on the lower eyelid), as the conjunctiva in this area is less sensitive than that overlying the cornea and will aid the retention of the medication (Jevon et al. [146]).
There are many factors that affect how much of an effect the instilled drug will have on the eye. The eye has a highly selective corneal barrier, which can prevent absorption of drugs. It also has a tear film, which provides an effective clearance mechanism. When an excess volume of fluid is present in the eye, this fluid either will be spilled onto the cheeks and eyelashes or will enter the nasolacrimal drainage system, with the potential for systemic absorption of the drug. Drugs also need to be introduced to the eye at a neutral pH, as acidic or alkaline preparations will result in reflex lachrymation, which will remove the drug from the eye.
Evidence‐based approaches
In order to optimize the effects of topical eye preparations, attempts should be made to ensure that there is proper placement of eye drops and ointments and that the volume applied is kept to a minimum. The number of drops instilled depends on the type of solution used and its purpose. Usually one drop only is required into the affected eye(s) and will be sufficient if it is instilled in the correct manner. The exceptions to the ‘one drop’ rule are as follows:
- Oil‐based solutions: these are used to lubricate the eyeball. Usually one drop is instilled, with further drops given as required.
- Anaesthetic drops: these are used to anaesthetize the eye; one drop should be instilled at a time. This is repeated until the drop cannot be felt on the eye.
The tip of the dropper bottle should be held as close to the eye as possible without touching the lids or the cornea. This will avoid corneal damage and reduce the risk of cross‐infection. If the drop falls from too great a height, it is difficult to control and will be uncomfortable for the patient. The eye should be closed for as long as possible after application, preferably for 1–2 minutes.
It is important to remember that systemic effects may arise from absorption of drugs into the body's circulation; this absorption is highly variable but can be minimized by applying pressure to the lacrimal punctum for at least 1 minute after applying eye drops. Some eye drops are contraindicated or have special precautions in some patients due to the risk of adverse effects (e.g. beta blockers, such as timolol, in patients with asthma or chronic obstructive pulmonary disease) (EMC [88]).
If patients need to use more than one eye drop preparation at the same time of the day, they may experience overflow and dilution when one immediately follows the other, so they should be advised to leave an interval of at least 5 minutes between the two. If eye drops have an extended contact time (e.g. gels and suspensions), then this interval should be extended (BNF [25]). If both drops and ointments are prescribed, the drops should be applied before the ointment, as the ointment will leave a film on the eye and hamper the absorption of the medication in drop form (Aldridge [4]).
Useful properties of eye ointments include:
- longer duration of action than eye drops
- a soothing emollient action
- easy to apply
- long shelf life (Downie et al. [82]).
Ointments are applied to the upper rim of the inferior fornix using a similar technique to eye drops (Figures 15.17 and Figure 15.18). A 2 cm line of ointment should be applied from the nasal canthus outwards. Similarly to the instillation of eye drops, the nozzle should be held as close to the eye as possible to avoid contact with the cornea and eyelids (Aldridge [4], Alexander et al. [5]).
Figure 15.17 How to instil eye drops.
Figure 15.18 How to instil eye ointment.
Pre‐procedural considerations
Equipment
A variety of droppers and bottles are available for the instillation of eye preparations. These include glass bottles incorporating droppers, plastic bottles with an integral dropper and single‐dose forms, such as Minims. The vast majority of eye drops are supplied in plastic bottles with an integrated dropper. Droppers from glass bottles expose the drops to potential contamination and can become contaminated themselves. Plastic bottles are squeezed between the fingers, so avoiding the need for a separate dropper. They are also less expensive than glass bottles with a dropper. Single‐dose units usually consist of small plastic dropper tubes that are squeezed and discarded after a single use.
Due to the risk of eye drops introducing infection into the eye and between individual patients and eyes, the BNF ([25]) provides extensive guidelines to minimize the risk of microbial contamination. Preparations for use in the eye should be sterile on issue.
Eye drops in multiple‐application containers used at home (domiciliary use) should not be used for more than 4 weeks after first opening (unless otherwise stated by the manufacturer). Multiple‐application eye drops for use on hospital wards are normally discarded 1 week after first opening, although different hospitals have different policies so practice may vary. Individual containers should be supplied for each patient. Separate containers for each eye should only be used if there are concerns about contamination. The BNF ([25]) advises that a fresh supply should be provided on discharge from hospital, although local policies may vary.
There is specific advice for patients undergoing eye operations and in specialist ophthalmic units, and the current BNF and/or local guidance should be consulted (BNF [25]).
In clinics, single‐application containers should be used. If there is a need to use multiple‐application containers, they should be discarded after single patient use within one clinical session.
A number of patients (particularly the elderly and patients with arthritic symptoms, visual impairments or Parkinson's disease) may experience problems instilling eye medication. This may be due to co‐ordination and/or dexterity difficulties, or difficulties squeezing the bottle. Aids are available to assist patients with these problems. Some manufacturers supply devices specific to their drug containers (see individual manufacturer guidance for further information). Patients will need guidance in how to use aids (Downie et al. [82]).
Preservatives and sensitizers
Apart from preservative‐free eye drops, all multiple‐application eye drops contain a preservative. These and other contents of eye drops may act as sensitizers in some patients. Preservative‐free eye drops may be required instead. Preservatives also cause problems in contact lens wearers (see below).
Contact lenses
Many people wear contact lenses in preference to spectacles. In addition, contact lenses are sometimes used to treat medical conditions. Special care is required when using eye medication in patients using contact lenses. Some drugs and preservatives in eye preparations can accumulate in hydrogel lenses (soft contact lenses). Therefore, unless medically indicated, lenses should be removed before instillation of the eye preparation and not worn during the period of treatment. Alternatively, preservative‐free drops can be used. Eye drops can be instilled in patients with rigid corneal lenses (hard or gas permeable). Eye ointments should never be used in conjunction with contact lenses and oily eye drops should also be avoided (BNF [25]).
Eye drop storage
Some eye drops need to be kept in refrigerator storage, and it is customary practice in many institutions for in‐use eye preparations to be stored in the fridge to minimize the risk of contamination. Products should be removed from the fridge and allowed to come to room temperature before administration to minimize patient discomfort.
Pharmacological support
Drugs may be given either systemically or topically to exert an effect on the eye (BNF [25]). However, if they are given systemically, the prescribing doctor needs to take account of the blood–aqueous barrier that which exists within the eye. This barrier is selective in allowing drugs to pass into the intraocular fluids. The permeability of this barrier may increase during inflammatory conditions or following paracentesis (the removal of excess fluid with a needle or cannula) (Andrew [9]).
Medications applied topically meet some resistance at the barrier presented by the lacrimal system (tear film barrier). A further barrier is the cornea, which is selectively permeable and only allows the passage of water and not drugs. However, corneal resistance may alter if there is damage to the corneal epithelium (Kirkwood [157]). Many drugs will produce similar effects in healthy and diseased eyes.
Drugs for use in the eye are usually classified according to their action.
Anti‐inflammatories and drugs for allergic conditions
Anti‐inflammatory drugs include steroids, antihistamines, lodoxamide and sodium cromoglycate. The most commonly used steroid preparations are dexamethasone, prednisolone and beta‐methasone (BNF [25]).
Corticosteroid eye drops should be used with caution as they can cause cataract formation or a gradual rise in intraocular pressure in a small percentage of people, particularly if the individual has a history of glaucoma (Forrester et al. [96]).
Antibacterials, antivirals and antifungals
Antibacterials and antivirals can be used for the active treatment of eye infections or as prophylactic treatment for eye surgery, after removal of a foreign body or following an eye injury. Antibiotic preparations in common use are chloramphenicol, fusidic acid and gentamicin. Aciclovir is the most commonly used antiviral eye preparation and is licensed for local treatment of herpes simplex infections (BNF [25]).
Artificial tears and ocular lubricants
Artificial tears and ocular tears are used when there is a deficiency in natural tear production. This can be due to a disease process or radiotherapy treatment, can occur as a side‐effect of certain drugs, or result when the eye‐blink reflex is absent. These artificial lubricants commonly contain hypromellose or hydroxyethylcellulose (BNF [25]). These eye drops may have to be instilled frequently (e.g. hourly). Carbomer‐containing eye drops may help to reduce application to four times a day. The severity of the problem and the patient's choice will determine the treatment.
Treatment of glaucoma
A range of drugs available in ophthalmic preparations are used in the treatment of glaucomas. These include beta‐adrenoreceptor blockers, carbonic anhydrous inhibitors, prostaglandin inhibitors, prostamides and sympathomimetics, and pilocarpine. Many patients are on combination therapy and a range of combination products are available (BNF [25]). It should be noted that although the action of eye drops is local, a number of them can also have systemic effects.
Local anaesthetics
Local anaesthetics render the eye and the inner surfaces of the lids insensitive. They are used before minor surgery, removal of foreign bodies and tonometry (measurement of intraocular pressure). The most widely used eye anaesthetics are oxybuprocaine and tetracaine (BNF [25]).
Mydriatics and cycloplegics
Mydriatics and cycloplegics cause pupil dilation and produce their effects by paralysing the ciliary muscle, stimulating the dilator muscle of the pupil (Figure 15.19) or a combination of both. They are used mainly for diagnostic purposes and most have an anticholinergic action. The most commonly used preparations are cyclopentolate hydrochloride, tropicamide and atropine (BNF [25]).
Figure 15.19 Effects of mydriatics.
Miotics
Miotics produce their effects by contracting the ciliary muscle and constricting the pupil (Figure 15.20). They open the inefficient drainage channels in the trabecular meshwork (BNF [25]). Miotics help in the drainage of aqueous humour and are used mainly in the treatment of primary angle‐closure glaucoma. An example is pilocarpine (BNF [25]). However, in the treatment of glaucoma, they have mainly been superseded by other drug groups.
Figure 15.20 Effect of miotics.
Specific patient preparation
The eye to be treated must be ascertained and the unaffected eye should not be dosed. Ascertain whether the patient is wearing contact lenses as contact of the medication with the lens can lead to increased drug absorption, visual distortion and discoloration of the lens (Chernecky et al. [39]). It may be necessary for the patient to remove the lenses and replace them with glasses for the duration of their treatment.
Procedure guideline 15.8
Medication: eye administration
Post‐procedural considerations
Immediate care
After using any eye medications, any excess medication should be wiped off from the inner to the outer canthus. If an eye patch is to be worn, it should be secured without putting any pressure on the eye. Patients should be warned not to drive for 1–2 hours, until their vision is clear, after instillation of mydriatics (which dilate the pupil and paralyse the ciliary muscle) (BNF [25]). Patients should be taught how to instil eye medication. If it is difficult for them to do so then it may be necessary for a community nurse to attend and administer the eye medication (Chernecky et al. [39]).
