Now that we’ve headed into spring, chances are that if you haven’t already, you’ll soon notice a steady stream of patients presenting at your practice with itchy eyes.
Allergy season is the time to get out your full armoury of treatments to help patients make it through the barrage of pollens, animal dander, mould spores and other environmental allergens that the warm winds will blow their way.
And then there are the patients year-round who also need your help to manage dry eye.
The term ‘ocular allergies’ encompasses a wide spectrum of disorders that include seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC), and the two rarer, sight threatening forms of ocular allergy, atopic keratoconjunctivitis (AKC) and vernal keratoconjunctivitis (VKS).
Whereas allergic conjunctivitis was once thought to be a disease of affluence, today there is a clear understanding that this debilitating condition is well-established worldwide, and particularly prevalent in developing countries facing sustained growth and increasing urban populations.
In Australia, at least 20 per cent of our population suffers from allergic conjunctivitis or some form of ocular allergy, the most common symptom of which is ocular itching.1
We need to remember that part of the tear film’s function is a flushing mechanism to protect the ocular surface. Because of
this, patients with dry eye disease are often more susceptible to ocular allergy…
Risk factors for allergic conjunctivitis include a patient’s family and personal histories. For example, a personal or family history of allergic disease, including hay fever (allergic rhinitis), asthma or atopic dermatitis (eczema) will increase the risk of an individual developing allergic conjunctivitis.
Additionally, environmental factors such as the air pollution, weather, age, gender, whether or not the person is a smoker and the condition of their eyes will impact risk.
While some people experience allergic conjunctivitis on a seasonal basis (most typically triggered by pollen and spikes in the weather during spring and summer), others experience perennial allergic conjunctivitis, triggered by dust mites, pet dander and mould, throughout the year.
Allergic conjunctivitis is predominantly a disease of young adults, with an average age of onset of 20 years.1 Although symptoms tend to decrease with age, older adults can continue to have severe symptoms.1
Both seasonal and perennial allergic conjunctivitis involve sensitisation of the immune system upon first exposure of the allergen. Following repeated exposure, the antigen-specific immunoglobulin E binds to mast cells in the conjunctiva, initiating their degranulation, which in turn can trigger a cascade of events representing an allergic response.2
Although the ocular itch that comes with allergic conjunctivitis will entice a patient to rub their eyes, it is important to discourage such behaviour because vigorous eye rubbing leads to mast cell degranulation, which in turn causes the itch to intensify.
Dry Eye Vs Allergic Conjunctivitis
Allergic conjunctivitis can be quite easily confused with dry eye disease and it’s easy to see why. The key symptoms of allergic conjunctivitis include itching, tearing, burning, foreign-body sensation and ocular dryness. The key symptom of dry eye is the sensation of ocular burning, with ocular signs and symptoms including corneal and conjunctival staining, a reduced tear meniscus, sandy and gritty foreign body sensation, keratitis and on occasion, photophobia.
Meibomian gland dysfunction is one of the major causes of evaporative dry eye disease and, depending on the geographic area, its signs and symptoms can often overlap with allergic conjunctivitis. According to Dr. Ernie Bowling, “the tear film serves as a barrier to allergens and dilutes them, as well as washes away inflammatory mediators. If the eyes are dry, more allergens reach the conjunctiva and mast cells. Additionally, inflammatory mediators have an increased residence time and enhanced concentration in the tear film”.2
Optometrist Dr. Jason Holland, who operates a Brisbane-based clinic specialising in the treatment of dry eye, said differentiating between dry eye disease and allergic conjunctivitis is often difficult. “Certainly I see a lot of patients where only one of the conditions has been managed and they present to me still unhappy,” he said.
“We need to remember that part of the tear film’s function is a flushing mechanism to protect the ocular surface. Because of this, patients with dry eye disease are often more susceptible to ocular allergy as the airborne particles linger on the ocular surface for longer.”
His advice?
“I always look for allergy first as there are normally common signs with this condition. Listen for the symptoms of itch, look for skin wrinkles below the nasal canthi and dark skin pigmentation below the eyelid. Assess the conjunctiva for papillae and the presence of stringy, mucous discharge. If these signs and symptoms are present you have ocular allergy. Next I would do my normal dry eye work-up to assess whether there are additional contributing factors to the patients symptoms. If you are unsure, you could always commence treatment of the ocular allergy and then at the review appointment assess the dry eye disease,” said Dr. Holland.
Treating Ocular Allergy
Sydney ophthalmologist Dr. Colin Chan agrees that both dry eye disease and ocular allergy can have similar symptoms, seasonal variation and respond to similar therapies due to common pathogenic pathways. Additionally, he says, one condition can cause or exacerbate the other. For example, reduced tear flow and volume in dry eye leads to reduced clearance of allergens from the ocular surface and therefore a greater propensity to allergy.3
Despite responding to similar therapies, Dr. Chan believes it is important to differentiate them because this will determine long-term preventative strategies. “For example, someone with ocular allergy may benefit from a desensitisation program, nasal sprays or prophylactic mast cell stabilisers. Someone with itchy eyes due to blepharitis would do better with lid scrubs.”3
Antihistamines, mast cell stabilisers, and corticosteroids all act to modify allergic responses to allergens.
Dr. Holland says when it comes to choosing a topical antihistamine, his “go to” product for many patients is Zaditen, “because of over the counter accessibility and the option of being preservative free. For some patients who don’t respond as predicted I will use Patanol. I will always manage the associated inflammation with chronic ocular allergy at the same time and my go to drop for this is Flarex. If the patient has a more severe case I will use Maxidex and if they have a poor ocular surface or associated dry eye I will use Pred Sol. Other helpful hints are chilled lubricants and cold compresses.”
He said the single biggest challenge when treating a patient with allergic conjunctivitis is the chronic nature of the condition. “Plus the fact that many patients need to treat their eyes for many months of the year. Everybody would like a quick fix! Whenever possible I will talk to the patient about the option of removing the source of the allergy but unfortunately for a lot of patients, unless they were to start living inside a bubble, this approach is not possible.”
Severe Cases
Brisbane ophthalmologist and corneal specialist Dr. Brendan Cronin manages ocular allergies for a very few patients who experience extremely severe symptoms. “Traditionally once the usual scaffold of treatments had been exhausted by an optometrist or GP, the only thing that would control an ocular allergy was steroid treatment,” he said. “Now we tend to prescribe Cyclosporine and Tacrolimus drops or ointment that can be specially compounded. With these treatments – particularly Tacrolimus, shocking allergies will often “melt away”.
Dr. Cronin told the inspiring story of a young woman who had decided against child birth for fear of losing her sight due to her allergies. “The patient had shocking allergies and as a result of them being poorly controlled she suffered from stem cell failure and scarred corneas. I put her on Tacrolimus and the allergies completely resolved. It was quite simply, life-changing. She was able to return to work, her marriage improved and she felt so good that she decided to try for a baby. When she becomes pregnant we will stop treating with Tacrolimus for a year and put her back on topical steroids. That will be difficult, however she is confident that knowing it is for a short time, she will be able to manage.
Tackling Dry Eye Disease
Dry Eye Disease (DED) or Dry Eye Syndrome (DES) – also known as keratoconjunctivitis sicca (KCS) or keratitis sicca – is one of the most common conditions seen by eye health professionals. This multifactorial disease of the tears and the ocular surface is caused by a dysfunctional lacrimal functional unit and accompanied by increased osmolarity of the tear film and inflammation of the ocular surface. Dry Eye Disease can be asymptomatic or symptomatic. In its symptomatic form, it can disrupt quality of life by causing discomfort and visual disturbance, can cause the tear film to become unstable and has the potential to damage the ocular surface.
People with dry eye are two to three times more likely to report problems with everyday activities such as reading, performing professional work, computer use, watching television, and daytime or night-time driving.4
According to Professor Fiona Stapleton et al, up to 35 per cent of the population experience dry eye as a significant problem. Two-thirds of sufferers are women, and postmenopausal women are at a higher risk. More severe dry eye affects 8 per cent of women and 4 per cent of men over 50 years of age.4
Other risk factors for dry eye include advanced age, smoking, systemic antihistamines, extreme heat or cold weather conditions, low relative humidity, computer use, refractive surgery, contact lens wear, radiation therapy, diabetes, Vitamin A deficiency, Hepatitis C infection, hematopoietic stem cell transplantation,
air travel, pollution.4,5,6
Sub-Types
There are two sub types of dry eye disease: aqueous-deficient dry eye (ADDE) or evaporative dry eye (EDE) and accurate diagnosis is important to ensure appropriate treatment. The two sub types, as described by Professor Mark Wilcox are:
Aqueous-deficient Dry Eye: usually caused by a lack of aqueous tear secretion by the lacrimal glands, but can also be a consequence of a failure of water secretion by the conjunctiva. This can result in hyperosmolarity and an unstable tear film with desiccation of the ocular surface. ADDE has two major groupings, Sjögren syndrome and non-Sjögren syndrome DED.5
Evaporative Dry Eye (EDE): can be either ‘intrinsic’ or ‘extrinsic’. Intrinsic EDE occurs where the evaporative loss from the tear film is directly affected – usually by meibomian gland dysfunction (MGD). Here the lipid secretion by the gland, required to control evaporation and maintain a normal tear film, is abnormal. Other causes include lid dynamics, low blink rate, and the effects of medications, such as systemic retinoids. Extrinsic EDE includes etiologies that increase evaporation through their pathological effects on the ocular surface, such as vitamin A deficiency, toxic topical agents (including preservatives), contact lens wear and ocular surface diseases (including allergic eye disease).5
Early detection and treatment of DED is important to help prevent ocular surface damage and improve the patient’s quality of life.
As a preventive measure, patients with dry eye should be encouraged to wear close wrapping glasses or sunglasses to slow tear evaporation and to avoid dry conditions. When indoors, they should be encouraged to sit away from air conditioning units and to use an air cleaner to filter dust and other particles from the atmosphere. A humidifier may also help by adding moisture to the air. Various studies have indicated that oral supplementation with omega-3 essential fatty acids could be evaluated as a possible therapeutic option for patients with meibomian gland dysfunction.6
Treating Mild to Moderate Dry Eye
Treatment for dry eye is primarily aimed at relieving symptoms and minimising discomfort while returning the ocular surface to normality before damage can occur.
Professor Mark Wilcox notes that the effectiveness of drops and tears can be short-term. Additionally, he says, not all artificial tear products are the same with variance in electrolytes, viscosity, osmolarity and the presence/type of preservative used. He writes that the overall protective effect of artificial tears may be further improved by combining several osmoprotectants with differing kinetics into one formulation.5
“Typically, a patient may try several products before finding one that suits their DED. Patients with moderate to severe dry eye require more frequent dosing and may benefit from unit-dose products that do not contain preservatives. Topical lubrication alone may be effective in mild cases, but many DED patients will need a multifaceted treatment approach and thorough investigation of the underlying cause(s) of their DED,” writes Professor Wilcox.5
Alongside artificial tears and lubricants are treatments such as the LipiFlow, a device which has two main components: a lid warmer and an eye cup. The lid warmer resembles a large scleral lens which heats the internal surface of the upper and lower eyelids while the eye cup, containing an inflatable air bladder, massages the eyelids to express the meibomian glands in the upper and lower eyelids simultaneously. The treatment takes just 12-minutes, making it more convenient than conventional warm compress therapy.7
Listen to your Patients
Yes, there is no doubt that this spring will present a few extra challenges on top of the usual dry eye issues for both you and your patients, but as Mr. Holland says, the solution is often at hand. “Listen to your patients. Most of the time if you ask enough questions the diagnosis will visualise before your eyes.”
