The remedy and solution for terrible eye pain and eye strain (from excessive computer use)

How to distinguish between eye allergy and dry eyes

It is crucial to distinguish between these two.

Here's a simple survey:  (or here)

Dr Maskins' wonderful book Reversing Dry Eye Syndrome has a specific section (p.96-97) on the matter.

Main tests to distinguish between the two:

Test 1: Wash the eyes with an eye rinse (e.g. Optrex) or diluted lemon drops, or just water. If this soothes the eyes EVEN temporarily, then you probably have an allergy, since allergen is washed away with the eye rinse.

In my case, I have always experienced some relief after this. Hence likely to be an allergy.

Test 2: Does vision get blurry without blinking?

Dry eyes lead to blurry vision without blinking. Allergies do not reduce tear production hence no effect on vision.

In my case, I have NEVER had blurry vision over the past year. Hence not likely to be dry eye

Test 3: Can you keep your eye open for more than 7 seconds without blinking?

If you can open your eyes for >7 seconds without experiencing EXCEPTIONAL burning then you likely have allergy.

In my case I can keep the eye open for >7 seconds, even though I have had chronic burning/ dryness sensation. This indicates I might not have dry eyes.

Other tests on the internet

If the itching is the primary complaint, the condition is mostly allergic in nature. [Source]

In my case I've had such severe symptoms including unbelievable pain (of all sorts) and burning, that itching might have been a subset but I can't really say.

If one rubs the eye, and the itching is worse, the condition is likely allergic. [Source]

No, rubbing the eyes has not made things worse in my case. Just the same. Hence dry eyes.

However, if the person has a history of using certain medications such as, diuretics, anti-depressants, antihistamines, hormone replacements, or birth control, dry eye may be the culprit. [Source

I've used oral antihistamines extensively last October before the onset of the problem, so could be dry eyes.

Usually with allergy, there is more redness in the eye [Source]

In my case I don't think there's been any noticeable redness.

You can have some level of itching with dry eye, but its hallmarks are more the foreign body sensation, grittiness, discomfort and reflex tearing [Source]

In my case I've never had a 'foreign' body sensation, but something like grittiness perhaps? Can't say. No reflex tearing, either,

Lower lids may reveal dark half circles. This swelling and discoloration is indicative of allergy.


In my case I've never had dark half circles or swelling.



See this:

and this:

and this:

and this:

Also here:

Antihistamine drops will help get rid of the itch when allergies are the cause, but the effects don't last very long. Doctors may recommend mast cell stabilizers, allergy medications that block the release of chemicals that cause eye irritation, or other types of eye drops. [Source]

Allergy drops:

This Youtube doctor suggests testsing for allergens: This one suggests rinsing out the allergens: 

This one suggests a few treatment options:


And this one, below – very informative:

Is it Dry Eye or Allergy?

Whether your patient describes the burnies, the itchies, or the itchy-burnies, here is how to make the differential diagnosis.

Mark B. Abelson, M.D., and Lauren Lilyestrom


Differentiating between dry eye and allergic conjunctivitis can be a complicated and frustrating task for many clinicians. Signs and symptoms of both dry eye and allergic conjunctivitis can be subjective and vague, and may appear to overlap.

The two conditions, however, do not share the same etiology, and treatment methods are different. Whether an individual has dry eye, allergy or a combination of both disorders, understanding the etiology and pathophysiology of each condition is essential for correctly diagnosing and treating patients.


Pathophysiology of Dry Eye

Despite the similar symptoms, dry eye and allergy each have a distinctive pathophysiology. Dry eye is caused by tear film instability resulting from insufficient or unhealthy production of one or more tear film components, namely:

Lipids. Lipid layer abnormalities often stem from meibomian gland disorders or blepharitis. These can cause rapid tear evaporation. As we age, our lacrimal glands produce fewer tears, which can result in reduced tear volume or tear flow.


Mucins. Ocular mucins are found both on the surface of the eye and freely floating in the aqueous. Underproduction of mucins by goblet cells and conjunctival epithelial cells can affect the ability of the tear film to adhere to the hydrophobic ocular epithelium.


Aqueous. The aqueous layer is generated by the lacrimal glands, and accounts for 90% of the tear film. The accessory glands are responsible for tear production, while the primary gland is associated with reflex tearing. Reflex tearing can sometimes be stimulated by the appplication of Schirmer I strips, which are used to measure tear volume. Some physicians believe reflex tears can render unanesthetized Schirmer measurements inaccurate. Fluorophotometry can provide more accurate measurements of tear volume and tear flow; however, it is also more time consuming.

Because these tear film abnormalities could be related to various environmental or biological influences, pinpointing the underlying cause of a patients dry eye symptoms may require a work-up that ranges from an extensive history to laboratory studies.

Blinking replenishes and maintains the integrity of the tear film; yet environmental, activity-related, psychological, and physiological factors can alter the blink rate.

When the blink rate is diminished, the tear film can become instable. Rapid tear film break-up caused by tear film instability can lead to ocular surface exposure, especially when combined with abnormal blink rates.

When tear film break-up occurs before a blink can replenish the tear film, some portion of the ocular surface will be exposed to the air. Over time, insufficient protection may promote surface cell desiccation and damage.

A detailed patient history is essential for subjective diagnosis and treatment of dry eye. Diagnosis of dry eye often incorporates fluorescein and lissamine green staining, which highlights damaged areas on the ocular epithelium, in the cornea and conjunctiva respectively.

Tear film break-up time (TFBUT), as measured following fluorescein dye instillation, can reveal tear film instability. Symptom or lifestyle questionnaires may offer a better understanding of a particular patients disorder.


Pathophysiology of Ocular Allergy

The ocular allergic reaction is a hypersensitivity response to pollen, animal dander, dust, or any other normally benign particle or substance. Initial exposure to an allergen primes the Th2-favoring immune system of the susceptible individual, and immunoglobulin E (IgE) antibodies bind to Fc (fragment crystallizable) receptors on conjunctival mast cells.

Mast cells are granulocytes that contain preformed mediators of allergy, most notably histamine. Subsequent exposure to the allergen induces cross-linkage of the allergen to the IgE receptors on the mast cells. The mast cells then degranulate, releasing both histamine and pro-inflammatory cytokines.

Histamine is the only allergic mediator that can cause the full range of allergic signs and symptoms, namely itching, redness, lid swelling, chemosis and tearing.1 It binds to both the H1 and the H2 receptors on the vascular endothelium, inducing dilation (redness) and endothelial gaping (swelling). Histamine that binds to the H1 receptor alone induces itching, redness and swelling.2

Since histamine is the only mediator of ocular allergy that produces itching, it is the key symptom for identifying ocular allergy.3 Diagnosis of allergy depends upon the appearance of ocular symptoms, patient history, allergy skin testing and the existance of ocular itch.

Dry Eye Etiology

Dry eye has always been linked to environmental factors, such as dry, windy conditions that rapidly desiccate the tear film. In this sense, dry eye can present either as an acutely exacerbated condition or as a chronic disorder.

Other factors associated with dry eye symptomatology include:

Autoimmune diseases. In diseases such as Sjgrens syndrome, immune system-induced inflammation attacks and destroys the lacrimal glands. Today, enhanced medical knowledge and treatments have allowed us to manage autoimmune diseases, such as Sjgrens syndrome and rheumatoid arthritis, that often cause dry eye.

LASIK and other surgical procedures. Although these may ultimately enhance a patients quality of life, such surgeries can produce temporary dry eye symptoms.

Blepharitis. This lid disorder, which is characterized by a dermatologic seborrhea and altered meibomian gland secretions, can  destabilize the lipid layer of the tear film, causing poor lipid spreading and increased evaporation.4

Contact lens movement and irritation. Up to 52% of contact lens wearers report some signs and symptoms of dry eye.5

Use of systemic medications. Oral antihistamines and numerous other medications can result in ocular dryness.6

Age and gender. Postmenopausal women are particularly susceptible to developing dry eye.

Excessive visual tasking. For example, either watching a televison or staring at a computer monitor for eight hours a day.

With all of these instigators of ocular dryness, dry eye, as a disease or a passive condition, may affect an estimated 11% to 22% of the general population.7

The many symptoms of dry eye include foreign-body sensation, general dryness, stinging, burning, grittiness and photophobia.

Nevertheless, discerning the underlying causes of a patients discomfort is vital to effectively manage the disorder and minimize both its signs and symptoms.


Allergy Etiology

Unlike dry eye, allergies appear to have arisen concurrently with industrialization and modern living conditions. The hygiene and urban allergy hypotheses are both based on the idea that the surrounding environment can alter the immune systems Th1-Th2 balance.

Cohort studies in African children who harbor helminthes, such as Schistosoma haematobium, have revealed that the parasites induce production of IL-10, an anti-inflammatory cytokine.8 Consequently, these children often have a lower prevalence of atopy than non-infected children.

This discovery suggests that city dwellers, who have not been exposed to the soil or the forest, may be more prone to allergy. This theory has been supported by epidemiological studies of rural farmers and their children, who, like children infected with helminthes, have a lower prevalence of allergy than their urban counterparts.9-10

Given the inherent filth that comes with thousands of people living in close contact, however, one may find it difficult to believe that cities are more conducive to hygienic practices than farms.

Indeed, city-dwellers often have extraordinarily high rates of asthma, and non-atopic children who grew up on the farm can develop itchy, red, swollen eyes when they move to the city.

Of course, the epidemiology of allergy extends beyond hygienic concerns and involves genetic influences in conjunction with the surrounding environment.


Differential Diagnosis

Dry eye and allergic conjunctivitis are two seperate conditions, with different epidemiologies, pathophysiologies and treatments. We must correctly differentiate between the two in order to provide the proper treatment.

The differential diagnosis of the conditions can be simplified by dividing the patient population into two groups: the burnies and the itchies. Simply put, if a patients eyes burn, the diagnosis is dry eye; if they itch, its allergy.

Be aware that semantics can confound the diagnosis. One patient may describe burning as itching and vice versa. This stems from the misconception that wanting to rub the eye means the eye is itchy. Itchy eyes are the result of histamine release, caused by allergen-induced degranulation of mast cells. The desire to rub ones eyes, however, can also be a response to dryness, as rubbing can increase reflex tearing and meibomian gland secretions, helping to temporarily relieve ocular discomfort.

It is known that the tear film deficiencies that are characteristic of dry eye can expose the eye to more allergens than normal, thereby eliciting allergic signs and symptoms.

This confusion has resulted in many years of misdiagnoses, even though dry eye and allergy tend to affect different age groups, occur in different seasons, and have different causes, signs and symptoms. The combination of the two conditions does not imply the existence of an entirely new ailment, but rather these separate conditions require individualized treatment.



Once a patient learns about his or her condition and its associated causes, he or she can try to avoid situations that will exacerbate discomfort. For example, dry eye patients may choose to avoid prolonged computer use and should minimize exposure to dry, sandy environments. Patients with allergy may have to avoid mowing the lawn and hugging the family cat.            

Complete avoidance is often unreasonable or impossible; however, several pharmaceuticals can provide relief.

Artificial tears, such as Systane (Alcon), are often used as a first-line defense against dry eye. Through a pH-dependant polymerization of the gelling agent hydroxyl-propyl guar (HP-guar), Systane coats the ocular surface, allowing for tear retention and epithelial self-repair. Optive (Allergan) is a recently released artificial tear that contains two standard demulcents (lubricants): glycerin and carboxymethylcellulose (CMC).

There is currently only one prescription drug for dry eye, Restasis (cyclosporine ophthalmic emulsion, Allergan), which incorporates cyclosporine A, a partial immunomodulator. The product is indicated specifically for aqueous deficient dry eye. Though it only has seen efficacy in 17% of patients, data suggest the effects of Restasis are improved when a tear substitute is used concomitantly.13 Various other non-prescription treatment and management options are available to dry eye patients, ranging from punctal occlusion or cauterization to ingestion of fish oil capsules, tea tree oil or omega-3 fatty acids.

Ocular allergy treatments include antihistamines, mast cell stabilizers and combination antihistamine/mast cell stabilizer drugs. Systemic antihistamines are known to cause ocular dryness, which is counterproductive when treating patients with allergic conjunctivitis or allergy/dry eye.14 Although probioticsspecifically, members of the genus Lactobacillus-have been suggested as possible remedies for allergy, to date, clinically significant reductions in both allergy signs and symptoms have only been described with any degreee of  consistency for atopic eczema.15-16

Topical antihistamine/mast cell stabilizers are the preferred treatment option because they address the release of histamine from the mast cells and work to prevent further mast cell degranulation without causing ocular dryness.

Pataday (olopatadine hydrochloride 0.2%, Alcon) is a recently introduced once-daily formulation of the olopatadine molecule. The once-daily dosing regimen is a long-awaited advancement in the treatment of ocular allergy. Contact lens wearers can instill the solution 10 minutes prior to lens insertion.

Elestat (epinastine hydrochloride 0.05%, Allergan) is a prescription H1 receptor antagonist/mast cell stabilizer, indicated for twice-daily dosing. Its antihistaminic capabilities reduce ocular itching, and its effects can for last up to 12 hours.

Optivar (azelastine hydrochloride 0.05%, MedPointe) is another prescription H1-receptor antagonist/mast cell stabilizer that is indicated for twice-daily dosing. It also has been shown to decrease the activity of other allergic mediators, such as leukotrienes.

Zaditor (ketotifen fumarate 0.035%, Novartis) has also been recently released over-the-counter, providing another

treatment option for allergy sufferers. It does not contain vasoconstrictors, lasts for up to 12 hours, and is the same formulation that has previously only been available with a prescription.

Alaway (ketotifen fumarate 0.025%, Bausch & Lomb). Like Zaditor, this is another brand of ketotifen which is now available over- the-counter.

For those patients who experience concurrent dry eye and signs and symptoms of allergic conjunctivitis, combining a tear substitute with an antihistamine/mast cell stabilizer can concentrate the tear film while minimizing allergic discomfort.


The only similarities between dry eye and allergic conjunctivitis are that they both affect the eyes, have environmental components, produce redness and tearing, and that patients find both conditions annoying. Therefore, one may believe that differential diagnosis ought to be simple.

Start by obtaining a detailed patient history to determine the possible causes of the signs and symptoms, and perform a slit lamp exam. If a patient complains of burning, gritty-feeling eyesespecially if the individual is older or spends a lot of time performing high-intensity visual tasksthen it is probably a form of dry eye. If an individual complains of itchinessespecially after exposure to an allergenthen the patient is most likely experiencing allergic conjunctivitis. Avoiding the environmental offender along with proper therapy enhances quality of life for both dry eye and allergy patients.

Dr. Abelson, an associate clinical professor of ophthalmology at Harvard Medical School and senior clinical scientist at Schepens Eye Research Institute, consults in

ophthalmic pharmaceuticals. Ms. Lilyestrom is a medical writer at Ophthalmic Research Associates in North Andover.


1. Abelson MB, Allansmith MR. Histamine in the eye. In: Silverstein A, OConnor G, eds. Immunology and Immunopathology of the Eye. New York: Masson Publishing; 1979: 362- 422.

2. Abelson MB, Udell IJ. H2-receptors in the human ocular surface. Arch Ophthalmol 1981 Feb;99(2):302-4.

3. Abelson MB, Smith L, Chapin M. Ocular allergic disease: Mechanisms, disease sub-types, treatment. Ocul Surf 2003 Jul;1(3):127-49.

4. Millar TJ, Mudgil P. The effect of human meibomian lipids and tear proteins on evaporation rate under controlled conditions. IOVS 2007;48: ARVO E-Abstract 431.

5. Riley C, Young G, Chalmers R. Prevalence of ocular surface symptoms, signs, and uncomfortable hours of wear in contact lens wearers: The effect of refitting with daily-wear silicone hydrogel lenses (senofilcon a). Eye Contact Lens 2006 Dec;32(6):281-6.

6. Ousler GW, Workman DA, Torkildsen GL. An open-label, investigator-masked, crossover study of the ocular drying effects of two antihistamines, topical epinastine and systemic loratadine, in adult volunteers with seasonal allergic conjunctivitis. Clin Ther 2007 Apr;29(4):611-6.

7. Brewitt H, Sistani F. Dry eye disease: The scale of the problem. Surv Ophthalmol 2001 Mar;45:199-202.

8. Van den Biggelaar AHJ, van Ree R, Rodrigues LC, et al. Decreased atopy in children infected with Schistosoma haematobium: a role for parasite-induced interleukin-10. The Lancet 2000 Nov;356(9243):1723-7.

9. Duramad P, Harley K, Lipsett M, et al. Early environmental exposures and intracellular Th1/Th2 cytokine profiles in 24-month-old children living in an agricultural area. Environ Health Perspect 2006 Dec;114(12):1916-22.

10. Eder W, Klimecki W, Yu L, et al. Association between exposure to farming, allergies and genetic variation in CARD4/NOD1. Allergy 2006 Sep;61(9):1117-24.

11. Grant R, Bowen S, McLean DE, et al. Asthma among homeless children in New York City: An update. Am J Public Health 2007 Mar;97(3):448-50.

12. Viinanen A, Munhbayarlah S, Zevgee T, et al. The protective effect of rural living against atopy in Mongolia. Allergy 2007 Mar;62(3):272-80.

13. Sall KN, Cohen SM, Christensen MT, et al. An evaluation of the efficacy of a cyclosporine-based dry eye therapy when used with marketed artificial tears as supportive therapy in dry eye. Eye Contact Lens 2006 Jan;32(1):21-6.

14. Ousler GW, Wilcox KA, Gupta G, et al. An evaluation of the ocular drying effects of 2 systemic antihistamines: loratadine and cetirizine hydrochlorids. Ann Allergy Asthma Immunol 2004 Nov;93(5):460-4.

15. Kalliomki M, Salminen S, Arvilommi H, et al. Probiotics in primary prevention atopic disease: a randomized placebo-controlled trial. Lancet 2001 Apr;357(9262):1076-9.

16. Xiao JZ, Kondo S, Yanagisawa N, et al. Effect of probiotic Bifidobacterium longum BBS36 in relieving clinical symptoms and modulating plasma cytokine levels of Japanese cedar pollinosis during the pollen season. A randomized double-blind, placebo-controlled trial. J Investig Allergol Clin Immunol 2006;16(2):86-93.

Vol. No: 144:08Issue: 8/15/2007
How to catch the subtle signs and ask the right questions when patients present with irritated eyes.
Gail Torkildsen, MD,
D. Andrew Workman, 
and Annie Plumer
North Andover, Mass
Differentiating between allergic conjunctivitis and dry-eye syndrome can be a challenging task. Patients may complain of non-specific symptoms like eye redness and irritation, and catching clinical clues can be difficult if patients are poor historians or can't recall the situations in which their symptoms are most prominent. To make matters worse, some patients may have both conditions.
In this article, we'll discuss the clinical tools that are available for diagnosing each of these conditions and how best to treat them. We'll then present a couple of case examples. 
Diagnosing Allergic Conjunctivitis
Allergic disorders of the ocular surface include seasonal and perennial allergic conjunctivitis, vernal keratoconjunctivitis, atopic keratoconjunctivitis and drug-induced dermatoconjunctivitis.
It's estimated that ocular allergies affect one-fifth of the general population. Seasonal allergic conjunctivitis and perennial allergic conjunctivitis are the most common, prevalent in over 90 percent of allergic disorders.1 AKC and VKC are more severe ocular allergies, often having corneal involvement. Drug-induced allergies tend to affect the area where the drug is in­stilled (mainly the lower lids) and will normally clear up once the patient stops using the offending agent. We'll focus here on identifying the more common SAC and PAC.
The ocular allergic reaction is an IgE-dependent hypersensitivity re­sponse. In susceptible individuals, initial exposure of allergen to the ocular surface stimulates the production of allergen-specific immunologic antibodies (IgE), which bind to mast cells in the conjunctiva. The mast cell is a granulocyte containing a number of preformed mediators, primarily histamines. Once activated, newly formed chemical mediators such as prosta­glandin D2, leukotrienes and platelet aggregating factor are synthesized. Exposure of allergen to the IgE-coated mast cells leads to the release of pre- and newly formed mediators contained within the mast cell.2
In allergy, hyperemia is diffuse in the conjunctival vessels and minimal in the perilimbal and episcleral vessels.
Histamine is the primary allergic mediator. It's the only mediator that can reproduce the full range of ocular allergic signs and symptoms of itching, redness, lid swelling, chemosis and tearing.3 After mast-cell degranulation, histamine binds to receptors located in the conjunctiva. Binding at H1 and H2 receptors on the vascular en­do­thelium induces dilation and endothelial gaping, while the binding of histamine to H1 receptors on nerve cells induces itching, as well as some redness and swelling.4 Histamine is also the only mediator that, when in­stilled, produces itching. Therefore, itching is the key symptom for identifying ocular allergy,2 which generally produces a strong desire in patients to rub their eyes, creating an itch-rub cycle that can contribute to eyelid swelling. If there's no itch, it's not allergy.
Most patients with ocular allergies will be asymptomatic during their office visits. The clinician must inquire about environmental triggers such as animal dander, trees, pollen, grass, ragweed, dust and molds. Many patients will forget their allergies in the off-season months. Only careful questioning may reveal that every spring their eyes bother them, or their symptoms are heightened when they mow the lawn or visit their cat-owning relative. They may reveal that their eyes only bother them when they go camping or spend more time outside. Some patients may take medications during allergy season, but won't report them when asked if they take any drugs. Occasionally, chart review will reveal that every May the patient visits the office. These are important clues. The month or season that the patient experiences symptoms is important. The intensity and frequency of the symptoms can help differentiate allergic conjunctivitis from dry eye.
Allergy skin testing can often reveal whether or not a patient is allergic to a variety of things. However, it's im­portant to note that these tests don't always correlate with site-specific testing (i.e., measuring levels of tear IgE).5 In addition, skin testing may fail to reveal the allergen which provokes the allergic conjunctivitis. Also, pa­tients with allergic conjunctivitis symp­toms and a positive skin test for a specific allergen may not have a positive conjunctival allergen challenge to that antigen. Thus, a combination of testing and questioning is necessary.
An intense itch differentiates ocular allergies from the burning, stinging and foreign body sensation associated with dry eye. If a patient experiences intense itching and redness while outdoors, suspect seasonal ocular allergies. Depending on the time of year, there may be high pollen counts for a specific antigen. For example, in the northeastern United States, March is commonly tree pollen season, May is grass season and mid-August through mid-September is ragweed season. As another example, Sacramento has a particularly high incidence of panseasonal allergies.
Perennial ocular allergens such as dust, pet hair/dander and mold can pre­sent a constant aggravation. If a pa­tient experiences intense itching, redness, and discomfort while indoors, and during times of the year inconsistent with seasonal allergens, then perennial ocular allergies may be in­volved. One study of allergens in homes found that the dust collected from nearly all of the houses sampled contained pet allergens, even though less than half of the homes had pets.6 Thus, it's difficult to avoid allergens.
Treating Allergic Conjunctivitis
Although total avoidance of environmental allergens is nearly impossible, patients can still find relief by re­ducing their exposure. For instance, staying inside on days with high pollen counts can help decrease symptom severity. However, in most cases, use of ocular allergic medications is warranted. There are a variety of available products, but the most effective for treating a topical disease such as allergic conjunctivitis are topical ocular treatments that are effective against all signs and symptoms.
Topical treatment of ocular allergies has proven superior to systemic treatment as it ensures direct delivery to the tissue. Additionally, topical treatment avoids the drying effects that have been shown to result from use of certain systemic antihistamines.7 Ocu­lar drying is counterproductive for the treatment of ocular allergies since a healthy, functioning tear film is vital for flushing away allergens.
Over-the-counter antihistamines or antihistamine/vasoconstrictor combinations offer quick onset, but short duration of action. Most are indicated for q.i.d. dosing, but the dose duration is only two to four hours. This regimen, therefore, cannot always provide all-day coverage for ocular allergic signs and symptoms.
The more potent prescription agents with antihistamine and mast-cell stabilizing activity provide the most effective treatment for ocular allergies. This class of dual-action agents includes Patanol (Alcon), Zaditor (Novartis), Elestat (Inspire/ Allergan) and Optivar (Med­Pointe). These products have comfortable formulations, rapid onset and long duration of action (dosed b.i.d.). Patanol is the only eyedrop within this category that is indicated for the full range of ocular allergic signs and symptoms.
Diagnosing Dry Eye
Patients with a tear-film breakup time of less than five seconds can be diagnosed with dry eye.
The underlying cause of dry eye is usually a deficiency in one or more of the three layers of the tear film (lipid, aqueous and mucin) due to underproduction of tears or excessive tear evaporation. Dry-eye conditions affect an estimated 11 to 22 percent of the population.8 Causative factors in dry eye include age, gender, systemic medications with drying side effects, dehydration, visual tasking, past surgical procedures and environmental conditions. Systemic diseases such as Sjögren's syndrome, rheumatoid ar­thritis and lupus are also associated with dry eye. Ocular dryness correlated with meibomian gland dysfunction and blepharitis is indicative of lipid layer deficient dry eye, while mucin- deficient dry eye is characterized by an underproduction of mucin by the conjunctival goblet cells. Aqueous-de­ficient dry eye is characterized by a de­crease in aqueous production by the lacrimal glands and is usually age-related. Malfunctions in tear secretion can also initiate an inflammatory re­sponse on the ocular surface.9
One of the most troubling aspects of dry eye is that symptoms don't al­ways correlate with signs. Patients may complain bitterly of burning and stinging yet have very little staining. Other patients may have severe staining yet only mildly complain of photophobia or have no symptoms at all. Researchers have discovered that dry eye progressively re­duces corneal sensitivity, which may account for these findings.10 There­fore, diminishing discomfort scores can be correlated with an increase in ocular-surface disease. This can make identification and treatment of dry eye a monumental task.
Patients with dry eye present with dryness, burning, stinging, grittiness, foreign body sensation, blurred vision and photophobia. It's important to distinguish between foreign body sensation (dry eye) and itch (allergy) by asking about the intensity and frequency of the symptoms. Tearing is another symptom that needs to be specifically elicited because most people don't associate it with dry eye. However, many dry-eye subjects will experience reflex tearing as a result of environmental stimuli, such as wind.
Dyes can aid in the diagnosis of dry eye by identifying dry areas of the conjunctiva and cornea. Fluore­scein is known to identify disruptions between corneal epithelium and conjunctival epithelium at intercellular junctions (dry, dead cells). Lissamine green is an alternative dye that is good for identifying degenerated cells and mu­cus. In studies, typically only 5 µl of fluorescein or 10 µl of lissamine is in­stilled. This administration of micro-quantities of dye is important to eliminate the oversaturation of the epithelium, making it easier to distinguish be­tween actual staining and quenching. Time to fluorescence can vary from pa­tient to patient, depending on tear volume and tear turnover rate, but may take two to five minutes. Barrier filters such as Wratten #12 or Tiffen #11 under 16X magnification can help highlight staining.11 A tear-film break­up time shorter than five seconds (with 5 µl of fluorescein) is indicative of dry eye.12 Dye can also be instilled using fluorescein or lissamine green strips.
Dry eye redness: Horizontal banding occurs over the conjunctiva, limited to the interpalpebral fissure.
Blinking is crucial for maintaining the integ­rity of the tear film. Some of the factors that can influence blink rate are environmental (e.g., humidity, temperature, airflow and lighting), activity-related (e.g., computer use, reading and driving), psychological (e.g., emotional state and mental load) and physiological (e.g., gender, ocular surface conditions, corneal sensitivity and muscular tension). Al­though re­searchers have developed a precise method for measuring blink rate that uses a digital camera and infrared illuminator to track pupil diameter (Casavant J, et al. IOVS 2004;45: ARVO E-abstract 77), there are other ways to measure blink rate in the office. Blinks can be simply counted while a patient is reading the eye chart. Dividing the number of blinks  per minute into 60 seconds gives the inter-blink in­terval (IBI).
The Ocular Protection Index, which measures the relationship between TFBUT and IBI, has recently been de­veloped as an accurate and reproducible tool for diagnosing dry eye. The OPI is calculated by dividing TFBUT by the IBI. If the OPI is less than 1, a patient's cornea is at risk for en­vironmental exposure, since the tear film is breaking up before the pa­tient is blinking. If the OPI is 1 or more, a patient's cornea has reduced risk because the patient is blinking be­fore the tear film breaks up. The OPI is also a useful tool for evaluating dry-eye treatments. (Ousler GW, et al. IOVS 2002;43:ARVO E-abstract 56)
Treating Dry Eye
Dry-eye treatment usually begins with increased education and a trial of artificial tears. Once patients learn about dry eye, they can begin to modify their behavior to avoid ag­gravating factors such as environmental stimuli or prolonged visual tasking.
Aside from education and modification of behavior, most pa­tients can benefit from artificial-tear therapy. There are a number of available artificial tears, each with a different mechanism of action. Some examples in­clude Soothe (Alimera), GenTeal (No­vartis), Systane (Alcon) and the Re­fresh products such as Re­fresh Tears, Liquigel and Endura (Aller­gan).
Soothe and Refresh Endura are emulsions that work by enhancing the lipid layer of the tear film. GenTeal, Refresh Tears and Refresh Liquigel in­crease the viscosity of the aqueous por­tion of the tear film and help prevent evaporation. Systane works through a pH-dependent polymerization of HP-guar, creating a gelatinous consistency, which covers and protects the ocular surface. After a period of frequent artificial tear use with no relief, punctal plugs may be inserted to help retain tears. However, punctal plugs usually reduce the quality of tears by preventing tear turnover. At this point, it may be wise to turn to a prescription dry-eye medication.
Restasis (Allergan) is the only ap­proved medication for increasing tear production due to ocular inflammation associated with dry eye, and is recommended for patients with more severe dry eye. Research has demonstrated that an artificial tear used in conjunction with Restasis, such as Systane, is a compatible and effective treatment.13 This is especially important during the period of time before the true benefits of Restasis kick in, which may be up to six months. There are also numerous products currently in clinical trials, which may prove to be beneficial treatments.
Clinical Examples 
Case #1
• History: A 60-year-old male in Sacramento, Calif., has glaucoma, and has been taking Alphagan (brimonidine, an alpha-2 agonist) twice a day for three months. He presents with red and itchy eyes. Upon further questioning, he reveals that he has nasal congestion at the same time every year.
• Exam: His eyelids are non-injected and non-edematous. The conjunctiva is non-injected and there are no follicles. Mild chemosis is present. His intraocular pressure is 16 mmHg OU.
• Diagnosis: This patient likely has seasonal allergies, unrelated to his glaucoma medication. Drug-induced dermatoconjunctivitis is less likely, as there is no evidence of lid involvement. Typically, in drug-induced allergies, the lower lid becomes excoriated and red. There is often redness in the inferior aspect on the bulbar conjunctiva. Drug-induced allergic reactions will progress relentlessly. Inferior pal­pebral follicles are also commonly seen in allergies to brimonidine, but are absent in this patient. He should continue using Alphagan. The seasonality of his complaints is a clue that he has allergic conjunctivitis.
• Treatment: A topical antihistamine/mast-cell stabilizer.
Case #2
• History: A 55-year-old woman has itchy and burning eyes. She lives in New Hampshire, and it is mid-winter. She has a cat and has been taking oral antihistamines. Her mouth is dry.
• Exam: Her lids appear normal. Her tear meniscus height is slightly re­duced at 0.1 mm and fluorescein staining shows a pattern in the palpebral conjunctiva.
• Diagnosis: Burning is highly likely to be dry eye, exacerbated by oral antihistamine use, which causes oral and ocular drying. An allergy to cat fur or dander is probably inducing itching in the eye.
• Treatment: She should frequently use a tear substitute, drink plenty of water and try to be conscious of her blink rate. She can use a humidifier for the dry eye. She should stop the oral antihistamines and use a topical antihistamine/mast-cell stabilizer and a nasal steroid for itching and nasal congestion. Restrict the cat to certain rooms and keep the house ventilated if weather permits.
• Comments: Due to her de­creased tear volume from dry eye, this woman is more likely to react to antigens, which are causing the itching. She should benefit from treating both conditions. Also, she should be re-eval­uated for dry eye once she stops taking the oral antihistamine.
Dr. Torkildsen is in private practice with Andover Eye Associates, serves as a principal investigator for numerous studies and consults in ophthalmic pharmaceuticals. Ms. Plumer is medical communications manager and Mr. Workman is a clinical research associate at Ophthalmic Research Associates in North Andover.
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