For those who suffer with allergies, it is estimated that around one in five will experience ocular symptoms.2 A survey of almost 2,000 patients attending UK optometric practices in the West Midlands recorded a report of at least one allergy in 13% and ocular allergy in 8% of the participants: three quarters of those with ocular symptoms reported use of medication, but only 11% of this group had received advice from an optometrist.3

This study suggests that the average full-time optometrist meets more than 250 patients each year that could certainly benefit from advice about how to manage ocular symptoms related to allergy, but such patients do not tend to seek or receive it. Allergies can have a significant impact on work and school performance, quality of life and even driving.4,5 Given that the market for hay fever remedies was worth more than £56m in 2012, perhaps there may be at least a business reason to apply our professionalism to this significant group of patients if not purely a clinical one.

Figure 1: College of Optometrist’s Hayfever Infographic 2016 (used with permission)

So, what advice could we offer a patient with seasonal (or perennial) allergies that affect their eyes? With regard to hay fever, the College of Optometrists recently released an excellent infographic, designed for members to help make their patients aware of the best way to reduce their symptoms, but also to remind them to consult their optometrist.6 But in order to understand how even the simple strategies work it is important to revise some the relevant pathophysiology for seasonal and perennial allergic responses.

How ocular allergy happens

The human immune system is a collection of cells, tissues and molecules that protect the body from attack, and has broadly two parts: innate immunity that is always there and ready to fight swiftly (skin, stomach lining, etc) and adaptive immunity where the response is to specific pathogens, often slower and has memory. When a reaction to a substance is inappropriate or exaggerated, it is known as hypersensitivity: allergy is a response to a substance to which you are hypersensitive which results in damage.

Substances that provoke an immune response are known as antigens, and in allergy they are termed allergens. Lymphocytes recognise the antigens or allergens and produces antibodies that are specific to that antigen to destroy them.

Table 1: Types of hypersensitivity

With hypersensitivity there are four types of possible mechanisms of response (table 1). Ocular allergy is a type 1 reaction, where the allergen (eg pollen or pet dander) enters the tear film and binds to immunoglobulin (IgE) antibodies on the surface of mast cells in the conjunctiva (figure 2).

Figure 2: Histamine release and the allergic reaction (image courtesy: Laboratoires Thea)

Mast cells are found in huge numbers in the conjunctiva, and when the allergen interacts with IgE receptors they undergo degranulation and release inflammatory mediators, mostly histamine. This release of histamine also initiates other immune cascades further increasing inflammation. Histamine is largely responsible for the symptoms of ocular allergy: it stimulates nerve endings which results in itchiness; it binds to specific receptors on blood vessels resulting in vasodilation and increased vascular permeability, ie redness and swelling (figure 3). The resultant inflammation is allergic conjunctivitis, and is either seasonal allergic conjunctivitis (SAC) or perennial allergic conjunctivitis (PAC). When the nose is also involved, the terms seasonal or perennial allergic rhinoconjunctivitis can be used.

Figure 3: The effects of histamine on the ocular surface

Hay fever demonstrates a biphasic response to the allergen, where the initial histamine release causes symptoms as an early phase lasting 20 to 30 minutes, but the secondary cascades to attract other inflammatory mediators and sustain mast cell activity produce another episode of symptoms three to 12 hours later. By understanding how histamine is released and what its actions are, you can appreciate how remedies can work to reduce signs and symptoms of hay fever.

Symptoms of ocular allergy

  • Bilateral symptoms
  • Itching
  • Pale, milky conjunctiva between red vessels due to chemosis
  • Red, watery eyes
  • Stringy mucous
  • Papillary reaction in conjunctiva
  • Nasal symptoms also present in most cases
  • Who gets hay fever?

It is estimated that around 18 million people suffer with hay fever, with the greatest prevalence among teenagers. The peak age for the onset of hay fever is in adolescence, and as many as 63% of students surveyed reported hay fever symptoms. The impact for teenagers can be particularly significant: they are 40% more likely to drop a grade between their mock and final exams – rising to 70% if they are taking a sedating antihistamine treatment.8 People living in the south and east experience the highest rates of hay fever, and rates in urban areas are generally higher than those in rural ones.

What triggers hay fever?

While grass pollen is the most common allergen (95%), people can be allergic to tree and weed pollen plus moulds and fungus. The pollen season separates into these main sections:

  • Tree pollen – late March to mid-May.
  • Grass pollen – mid-May to July.
  • Weed pollen – end of June to September
  • Moulds – September to October

For anyone allergic to tree, grass and weed pollens, they can suffer a very prolonged ‘hay fever’ season.7 Pollen counts are lowest in the morning then rise through the day as the pollen rises in the air, and then in the evening it descends as the air cools meaning symptoms can peak in the evening for some, too.

Millions know the misery of hitting a patch of allergens

Avoidance measures

These are the simplest remedies but have the potential to be the most effective so do not be afraid to remind your patient of the simple things they can do on a daily basis to make the hay fever season more bearable. Washing hands regularly and trying not to rub itchy eyes is an obvious thing to mention, but many people may not realise that long hair can prolong exposure by holding pollen, especially when not tied back. On sunny days wearing close-fitting and wrap-around sunglasses can be a helpful barrier.

Monitoring the pollen count is now easier than ever thanks to digital communications, meaning a hay fever sufferer can take steps to minimise symptoms if they can see a high forecast in their area for the day ahead. Another tip is to circulate the air in the car internally, and use air conditioning rather than opening car windows.

Contact lenses – do they help or hinder?

Most of us have fitted lenses to patients with a history of hay fever to find that their wearing comfort and success during hay fever season varies enormously. Allergens have the potential to stick to the lens surface and increase exposure so daily disposables and strict ‘rub & rinse’ regimes might be recommended. There is some evidence to suggest that the wearing of daily disposable contact lenses (particularly those with lubricating agents added) can have a barrier effect and reduce severity and duration of symptoms.9

Are dry eye drops beneficial?

A topical eye drop will dilute the allergen and a prolonged residence time across the ocular surface can provide some physical barrier. This explains the immediate relief that is often felt from all eye drops, and you will observe more than one GSL product on the allergy market whose only ‘active’ ingredient is purified water for rinsing. Modern preservative-free artificial tears are the superior choice if you are looking for rinsing and residence time on the inflamed eye. One dry eye drop formulation has been shown to maintain an increased tear film thickness for up to four hours after a single drop.10 Artificial tears alone have been shown to reduce redness, symptoms and ocular surface temperature after exposure to grass pollen in hay fever sufferers.11

While it might be tempting to encourage patients to keep such eye drops in the fridge for vasoconstrictor effect, the stability of any product designed to be stored at room temperature cannot remain guaranteed, so this practice should not be recommended unless the packaging or the manufacturer indicates otherwise.

Cold compresses – do they work?

The cold temperature of a compress induces vasoconstriction which reduces redness and swelling but also retards the secondary wave of inflammatory mediators that would otherwise arrive faster with increased blood flow to the conjunctiva. One interesting study compared the use of cold compresses alone, with artificial tears or with a topical antihistamine/mast cell stabiliser drop. The authors concluded that cold compresses combined with artificial tears were the most effective at reducing redness (even compared to the medicinal product), and the treatment effect of the medicinal drops could actually be enhanced by adding a cold compress for five minutes after drop application.11

Topical over-the-counter remedies

Given that most patients are self-selecting products to relieve hay fever symptoms, it is no surprise that this market provides a plethora of branded and generic products, mostly in the P category. In a ‘mystery shopper’ study amongst 100 pharmacies, half recommended sodium cromoglicate as first line treatment and just a single one suggested the patient should seek advice from their optometrist.12

Indeed, the most commonly sold hay fever topical product in the UK is 2% sodium cromoglicate, acting as a mast cell stabiliser. The clue is in the name – such products stabilise the mast cell membrane to reduce its ability to degranulate but cannot do anything for the histamine already circulating. Many optometrists and contact lens opticians will know this approach from its traditional use in the management of contact-lens associated papillary conjunctivitis (although this condition is less common now due to widespread prescribing of frequent replacement contact lenses). In this situation we are perhaps more familiar than our pharmacy colleagues with the idea that it will take five to 14 days to take effect and start to reduce symptoms, so it may surprise you to hear that it is ‘first line’ in pharmacies. For hay fever, this prophylactic approach with mast cell stabilisers might not be the most effective treatment for acute presenting symptoms in a patient: they need to predict their problems (based on pollen season and predictions) and ideally start using the drops several weeks before exposure to the allergen, as a prophylactic treatment.

Topical antihistamines work differently: they block the attachment of histamine to blood vessel walls and nerve endings, so actually work to provide rapid relief of acute symptoms. When combined with a vasoconstrictor this can be particularly effective, providing rapid relief from redness, itching and swelling. So, a patient might use this initially (normally no more than seven days) but then move on to a mast cell stabiliser (or systemic medication) for more prolonged periods. A caveat should be added about any eye drop a patient intends to take long term if it contains preservatives – these should be avoided wherever possible.13,14 The leading brands involved in the management of SAC in the UK are shown in figure 4.

Figure 4: Leading brands in the management of seasonal allergic conjunctivitis

A flow chart in figure 5 suggests a summary of these management options for mild/moderate hay fever symptoms.

Figure 5: Suggested management flowchart for patients with mild/moderate seasonal allergic conjunctivitis

In summary, simple measures can be effective for managing mild/moderate hay fever symptoms that involve the eyes, and there is clinical evidence to support their use. In part 2 of this article we will review the P and POM products available to UK optometrists for managing ocular allergy generally, and how they might be sold in the optometry setting, plus an overview of the more severe forms of allergic conjunctivitis that can involve the cornea.

Alleviating allergy suffering

If you suffer from allergies you are certainly not alone: approximately 20% of European adults are affected by at least one allergy, with hay fever being the most common.1 In fact, the UK is one of the top three countries in the world for the highest incidence of allergy (Allergy UK); it is a growing chronic disease expected to affect more than 50% of all Europeans by 2020 (EACCI, 2011). In this first part on this topic, the simple but effective ways to manage the ocular manifestations of allergy will be described, and in part two, the more medical management of allergic eye disease will be reviewed.

Professor Christine Purslow is head of medical affairs for Thea Pharmaceuticals, researcher at Cardiff University, and visiting professor at Plymouth and Aston Universities

References

1 Bergmann KC et al (2016) Current status of allergy prevalence in Germany: Position paper of the Environmental Medicine Commission of the Robert Koch Institute. Allergo J Int.25:6-10.

2 Leonardi A (2005) Emerging drugs for ocular allergy. Expert Opinion on Emerging Drugs 10(3):505-20.

3 Wolffsohn JS et al (2011) Prevalence and impact of ocular allergy in the population attending UK optometric practice. Cont Lens Ant Eye 34:13-138.

4 Pitt AD et al (2004) Economic and quality-of-life impact of seasonal allergic conjunctivitis in Oxfordshire. Ophthalmic Epidemiol 11;17-33.

5 allergyuk.org/allergy-statistics accessed May 2016.

6 college-optometrists.org/en/college/campaign_link/a-guide-to-hay-fever.cfm accessed May 2016.

7 Hay fever prevalence in the UK in 2020, 2040 and 2060, Prof Jean Emberlin, National Pollen and Aerobiology Research Unit, University of Worcester. June 2009.

8 Walker S et al (2007) Seasonal allergic rhinitis is associated with a detrimental effect on examination performance in United Kingdom teenagers: case-control study. Allergy Clin Immunol. 2007

9 Wolffsohn JS et al (2011) Role of contact lenses in relieving ocular allergy. Cont Lens Ant Eye 34;169-172.

10 Schmidl D et al. (2015) Tear film thickness after treatment with artificial tears in patients with moderate dry eye disease. Cornea 34(4):421-426.

11 Bilkhu et al (2014) Effectiveness of nonpharmacological treatments for acute seasonal allergic conjunctivitis. Ophthalmology 121(1):72-8.

12 Bilkhu et al (2013) The management of ocular allergy in community pharmacies in the United Kingdom. Int J Vlin Pharm 35:190-194.

13 Noecker R (2001) Effects of common ophthalmic preservatives on ocular health. Adv Therapy 18(5):205-208.

14 Bauduoin C et al (2010) Preservatives in eye drops: The good, the bad and the ugly. Prog Ret Eye Res 29;312-334.