prevention

Prevent the Onset and Exacerbation of DES

Identify the risk factors that both predispose patients to and can worsen dry eye syndrome.

Sean P. Mulqueeny, O.D., Creve Coeur, Mo.

I've achieved the 20-year milestone of practice this year, and during that time I've witnessed an enormous growth in research on the pathophysiology of ocular surface disease. (See “Dry Eye: Diagnosis and Management,” below.) This research has lead to the creation of more effective treatments. That said, we should not overlook the efficacy of reducing the modifiable factors that can both cause and worsen dry eye syndrome (DES).

Because patients are often unaware of these modifiable risk factors and how to decrease them, many think they must accept their associated ocular dryness as a fact of life. It, thus, becomes incumbent upon us, as practitioners, to ask our patients via patient history form whether they are experiencing ocular dryness and whether they have one or more of the modifiable risk factors. Then, we must educate them on how they can either keep DES at bay or preclude the worsening of the condition if they've already been diagnosed.

Here, I discuss these modifiable risk factors and what to recommend to patients to reduce them.

Contact lens wear

Approximately 50% of people who wear contact lenses complain of ocular dryness. This is because soft contact lenses can absorb one's natural tears. Soft lenses are comprised of hydrophilic plastics that house water. The more water a lens has, the more likely it is to dehydrate. This, in turn, results in the lens absorbing water from the wearer's tear film, causing ocular dryness. RGPs can disrupt the tear film as well because they are a foreign material to the eye. This creates issues with exposure due to an incongruous tear layer.

ACTION STEPS: To reduce this risk factor, recommend the patient switch to a different lens material, discuss the benefits of rewetting drops, and let the patient know that trying a lens that offers a greater replacement schedule, such as a daily wear lens, may be beneficial.

Intense visual concentration

Watching TV, video game play and computer use have all been shown to result in a reduced blink rate. In fact, a study reveals that while looking at a computer screen or reading, people's average blink rate went down by half.¹ Because lid movements not only smooth the precorneal tear film (e.g. “wind-shield effect”), but also affect the composition and stability of the different tear layers, these activities place the patient at risk for DES as well as the worsening of the condition.²

ACTION STEPS: To decrease this risk, educate patients to take make a conscious effort to blink and take frequent breaks from these activities.

Environment

Exposure to wind and dry climates can increase tear evaporation.³ In addition, ocular discomfort (e.g. burning, dryness and itching) is among the top two symptoms in in-office environments. The environmental reasons for this discomfort: exposure to allergens, indoor air pollutants and the climate conditions of low humidity, high temperature and draft.⁴ These environmental conditions result in at least three mechanisms that change the precorneal tear film (PTF). First, the PTF structure is altered by a physical process that increases the emission rate of tear loss, with the outcome being hyperosmolarity, meibomian gland dysfunction (MGD) and associated discomfort. Second, the structural composition of the PTF's outermost lipid layer is altered by aggressive aerosols and combustion products — from both the in- and outdoors — that promote tear loss and possibly chemesthesis. Finally, strong sensory irritating pollutants can induce chemesthesis via trigeminal stimulation. That said, generally speaking, organic and inorganic indoor air pollutant concentrations are often too low to cause chemesthesis, though the odor itself may still result in ocular discomfort.

ACTION STEPS: If the patient is exposed to wind and dry climates on an ongoing basis, recommend he use protective eyewear, such as wrap around goggles and although rarely used, moisture chamber-fitted goggles in extreme cases, and lubricating drops. Non-preserved tear supplements are preferred; typically dosed q.i.d. initially. Should low humidity, high temperature and draft be a potential issue in one's work environment, recommend the patient ask his supervisor whether he can relocate his desk within the office, especially if the patient is in close proximity to a heat or air conditioning vent. If this isn't an option, deflection of direct air blown into the area is beneficial, as is ensuring appropriate lighting levels in the workspace. (Utilizing warm lights in lieu of cooler lights, such as fluorescents, can help relieve eye strain that can potentially impact the quality of the tear film.) Also, instruct the patient to minimize the use of both heating and air conditioning when driving. If these environmental red flags are present in one's home, recommend the patient use a humidifier, therapeutic goggles and ointments and gels at bedtime. Results from epidemiological and clinical studies support that relative humidity >40% is beneficial for the PTF.⁵

Smoking

Cigarette smoke can also cause and exacerbate DES. Specifically, research has shown that cigarette smoke deteriorates the tear film and ocular surface with a decreased quantity and quality of tear film, a reduction in corneal sensitivity and squamous metaplasia.⁶ Further, brush cytology in smokers reveals significant conjunctival neutrophil infiltration.⁷ The toxins in cigarette smoke act as a pollutant, degrading the quality of the tear film and ultimately the ocular surface.

ACTION STEPS: To reduce this risk factor for both the onset and worsening of DES, suggest smoking cessation. In my practice, I often times offer to coordinate smoking-cessation efforts with the patient's primary-care physician. Medical treatments should also be considered and may include nicotine replacement therapy, antidepressants and nicotine receptor blockers. You may also want to recommend the patient seek counseling to kick the habit. If, however, the patient says he must smoke, recommend he cease doing it while in a car, among other enclosed areas.

Inadequate diet

A diet low in omega 3 essential fatty acids (e.g. brussels sprouts, chopped basil, fish, spinach, eggs, etc.) or one that has a high ratio of omega 6 (vegetable oil, nuts and seeds, etc.) to omega 3 fatty acids has been shown to both cause and exacerbate DES, says the 2007 Report of the International Dry Eye WorkShop (DEWS Report). Also, excesses of dietary fats, salt, cholesterol, alcohol, protein and sucrose have been associated with or suggested as causes of tear dysfunction.⁸

ACTION STEPS: To decrease this risk factor, provide patient education that an Omega 3-rich diet is critical to the management of both their systemic and ocular health. If the patient says he is unwilling or unable to consume appropriate quantities of food containing high levels of omega 3 fatty acids, omega 3 supplements should be recommended.

Refractive surgery

Because refractive surgeries, such as LASIK, involve the severing of corneal nerves during flap creation, they disrupt trophic sensory support to the denervated region. Termed LASIK-induced Neuro Epitheliopathy, or LINE, this condition upsets tear dynamics, resulting in decreased blinking, and, therefore, ocular dryness, says the DEWS Report.

ACTION STEPS: Obviously this cannot be prevented post-surgery, so initiate a pre-surgical protocol of cyclosporine ophthalmic emulsion 0.05% (Restasis, Allergan) b.i.d., a steroid q.i.d. and an Omega 3 tear supplement b.i.d. For mild dry eye, I treat the patient for two-to-three weeks pre-operatively. For more significant cases, treatment may take four-to-eight weeks to improve the tear film to an acceptable level. I've found that this regimen should be continued for a minimum of six months postoperatively to give the patient the best chance of avoiding refractive-surgery-induced DES.

What can be controlled

Although we can't control the DES risk factors of advancing age, female gender, autoimmune diseases and/or prescribed anti-cholinergics and oral contraceptives, we must keep in mind that six modifiable risk factors can both cause and exacerbate the condition as well. Knowledge of these risk factors along with patient education on how to reduce them can both prevent the onset of DES and preclude it from getting worse, should the patient already have the condition. I've seen both actions result in patient loyalty and referrals. OM

References available in the online version of this article at www.optometric.com.

Dr. Mulqueeny is in private practice in St. Louis, where he specializes in ocular surface disease. In addition, he's the director of the Dry Eye Institute of St. Louis, and is currently the Principal Investigator for the PRogression Of Ocular Findings in Patients With Dry Eye Disease (PROOF) study. E-mail him at spmulqueeny@surevision.us, or send comments to optometricmanagement@gmail.com.