When Can Anti-Allergy Eye Drops Help and When It Can Be More Serious!
There are many eye drops available, many widely obtainable without even a recommendation from an Eye Care/Heath Care Professional. Some have clinical trial evidence behind them and are authorised by the Medicines and Healthcare products Regulatory Agency (MHRA), others use some of ‘natures’ ingredients and while they may help they not have been subject to the standards of proof medicines have. Most eye allergy is relatively benign but unpleasant, however some forms do have the potential to be sight-threatning! The only sure way of knowing is to be examined by an Eye Care Professional.
First let’s look at ocular allergies and how they may be managed. To help us, let’s start with basics, what is an allergy? We can consider it an inappropriate inflammatory reaction to foreign substances by the body’s immune system, whereas it’s appropriate for the immune system to react to fight off parasites, bacteria or viruses for instance, an inappropriate reaction to usually harmless substances like pollen, molds, dust mites etc manifests itself as allergy. The substances that trigger allergy are called allergens.
Immunoglobulin E (IgE) is an antibody that all of us have in small amounts. Allergic individuals, however, generally produce IgE in larger quantities. During a sensitisation period an allergen causes the body to overproduce IgE which coats cells such as mast cells and basophils, these contain various mediators, such as histamine. These coated cells are now primed, ready to react to all subsequent exposures to the allergen, this leads cells to the release of the allergic mediators mentioned above (Type 1 reaction within minutes). These chemicals cause typical allergic symptoms, such as localized swelling, inflammation, itching, and mucus production.
Histamine is the main mediator of type I allergic reactions. In ocular tissue, histamine release from mast cells induces itching, tearing, swelling of the conjunctiva and eyelids and blood vessel dilation. Type IV hypersensitivity is a cell-mediated process involving T-cells, cytokines, and macrophage activation. The response peaks at 48 to 72 hours (called “delayed” hypersensitivity) and results in tissue damage.
Typical symptoms include sudden onset of ocular itching (the symptom of true itching is highly indicative of an allergy component), irritation, burning sensation and watering.
Mast cell stabilisers
Pharmaceutical agents called mast cell stabilisers inhibit the release of histamine and therefor its effects, sodium cromoglycate 2% is such an agent, was the first mast cell stabiliser and the one most used by patients with ocular allergy, mainly because not only is it available as a prescription and pharmacy medication but it is now widely available from many sources without medical supervision in preserved and single-dose non-preserved forms. However, it can take several days before its use starts to relieve symptoms, in fact it is advocated sodium cromoglycate is ideally used several days before the antigen is encountered. Systemic side-effects are rare but not unknown, topical side-effects are normally mild and transient.
Anti-histamines inhibit the activity of histamine and its signalling pathways between cells. Both systemic and topical anti-histamines can be divided into first generation where the potential for systemic side-effects is greater, such as sedation, dry mouth, dry eye, blurred vision, constipation and urine retention. These effects can happen with topical application but are less likely than if taken orally. Second generation anti-histamines tend not to produce these effects as much.
They will tend to have a more rapid effect in relieving symptoms than the mast cell stabilisers, all though generally well tolerated, as with all eye-drop medication, topical side-effects can occur, ranging from burning, eye redness and stinging through lid swelling to eye surface damage.
Decongesting, avoiding, cooling and flushing!
Many eye drops with the names that include or imply a ‘dazzling’, ‘brightening’ ‘sparkling’ or ‘redness relieving’ (grouped under the title of ocular decongestants) effect contain agents such as naphazoline which constrict conjunctival blood vessels, relieving eye redness, tearing and irritation. The effect is normally rapid, however ocular side-effects such as mild pupil dilation and an increase in intraocular pressure may occur. Systemic side-effects have been reported, amongst them being changes in heart rate and blood pressure.
Other simple, readily available, methods of relieving symptoms of ocular allergy instead, or as well as medication are; to avoid contact with the source of the offending allergen be it a cat, grass/tree pollens etc this is a basic strategy but amazingly effective! Cool applications (aka cold compresses, a term I try to avoid as occasionally patients will go home to compress their eyes!), this too will have a vasoconstriction effect and relieve itching. Dry eye drops if used several times per day will have a flushing effect, diluting and/or washing out allergens and inflammatory mediators, having read previous articles of mine on topical eye therapy you will know I would recommend they are non-preserved.
So you can see that what might appear to be a simple problem, with a quick and easy remedy is more complex and the answers are more nuanced. If at all possible, to help with eye allergy problems that don’t manifest themselves significantly in other parts of the body, we would always recommend specific eye drops, used in a specific way, perhaps alongside other direct methods of reducing symptoms, so a more comprehensive approach than ‘redness relieving’ drops alone. We will even show you how to reduce the possibility of adverse side-effects from the medications, remember these can occur in prescription and non-prescription eye drops!
Although it is not possible to be 'allergic' in the true meaning of the word to contact lenses, it is possible for patient's to find certain lenses more 'bio-compatible' than others. It is certainly possible imune system responses can be trigered by contact lens care products or depoits on the lenses. A Contact Lens Practitioner is by far the best person to determine the cause and answer to contact lens related problems.
At the beginning of this article we mentioned the posiiblity that the eye's allergic reaction can be sight-threatning. Because of the potential for vision loss, it is critical that the form of ocular allergy is correctly identified. Keratoconus and cataract formation are common in certain eye allergies which can also cause corneal ulceration. It is also thought that persistent eye rubbing results in an increased risk of retinal detachment. This correct identification of the specifc form of eye allergy cannot be be done by a GP or pharmacist, only by a Eye Care Professional using a bio-micropscope to examine the eye.
By far the best way for us to help is through a consultation, be it remotely or even better face-to-face.
If you would like to contact us for non-urgent eye care discussions related to eye allergy, dry eyes or contact lenses you can by email:
- Andrew D Price (Leyland, Nantwich, Southport or general enquiries)
- Elizabeth Ralph (East Midlands and South Yorkshire)
- Vanessa Uden (Surrey, Hants, Berks)
- Mr Ganeshbabu Mahalingam (West Yorkshire)
Personal portfolios can be found here:
- Mr Andrew D Price FBDO(Hons)CL MBCLA
- Mrs Elizabeth Ralph FBDO CL MBCLA
- Mrs Vanessa Uden FBDO CL MBCLA
- Mr Ganeshbabu Mahalingam MPhil PhD FCOptom FBCLA ProfHigherGlaucoma