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LASIK & Dry Eyes

Optimizing Eye Comfort

By Craig S. Bindi, MD

Being bothered by “Dry Eyes” is one the most common problems that I treat in my ophthalmology practice. Luckily, when managed systematically and proactively, these symptoms should be very treatable and temporary. Whether you have already had Laser Vision Correction or are considering it in the future, this article explains the simple steps for optimizing eye comfort and teaches the scientific rationale behind these tips.

Summary of the Problem

Symptoms of “Dry Eyes” include foreign body sensation, burning sensation, fluctuating vision clarity, and light sensitivity. Any corneal surgery has the potential to affect corneal nerves and decrease tear production. A recent very large scientific review (based on 32,000 LASIK procedures from 46 independently published studies from 13 countries) evaluated the frequency, duration and cause of dry eyes after laser vision correction. The study found that 35% of patients reported they noticed some dry eye symptoms after LASIK surgery, yet, 32% of patients also had these same symptoms PRIOR to surgery with glasses or contacts. Most patients reported returning to “normal or baseline” by 6 weeks after LASIK, but it can last for several months. Having dry eyes before LASIK was the best predictor of postoperative dry eye and severe dry eye problems were very rare. Also, thinner LASIK flaps, Intralase-based LASIK flaps, “nasal-hinged” LASIK flaps and PRK have been associated with less dry eye symptoms. With scientific advancements and a better understanding of the ocular surface, various treatments have limited the severity of this problem.

How Can LASIK Cause Eyes To Feel Dry?

If you have ever scratched your cornea or had a corneal infection, you already know that the corneal surface is very sensitive to touch or injury. A vast network of sensory nerves provides this sensitivity. In LASIK, creation of the corneal flap decreases the function of these nerves, which temporarily diminishes corneal sensitivity. Subsequently, the eye cannot effectively send nerve impulses to the tear gland for additional moisture. After these nerves grow back, sensitivity returns to normal levels within a couple months after treatment.

The corneal nerves enter the cornea along the horizontal axis at the 3 o’clock and 9 o’clock position. Older microkeratomes used to make the LASIK flap hinge on the top (superior-based hinge), so both branches of these nerves were incised. Newer LASIK technologies, such as Intralase, have evolved to create a nasal-based hinge, which preserves the entire nasal branch of the corneal nerve and reduces the number of corneal nerves affected by the flap creation by about 50%. LASIK flaps with a nasal-based hinge have shown to have a lower incidence of dry eye related problems. Until normal tear function returns, Dry eye can be the source of sub-optimal vision, fluctuating vision and eye discomfort until it resolves.

Basic Physiology of the Human Tear Film

The normal human tear film is about 98% water, 1% oil and 1% mucous. These three components work together to hydrate the cornea, stabilize the tear film and prevent evaporation. The lacrimal gland and other ocular surface glands create all three essential parts of the human tear film. If any of these components are missing or out of proportion, the surface of the eye will “dry out”. When the ocular surface senses irritation, it sends a nerve impulse for the tear glands to produce tears (reflex tears). Other ocular surface glands consistently produce baseline tears are less dependent on nerve impulses (basal tears). In the postoperative period, simple measures can be taken to keep the cornea hydrated, stabilize the tear film and prevent tear evaporation.

The Primary Dry Eye Remedy

With any corneal surgery, the ability to efficiently produce tears is temporarily affected. For this reason, it is very important to use preservative-free artificial tear eye drops at least 4 times per day for the first month after LASIK (whether one feels dryness or not), and longer if desired to maintain comfort. If used in a diligent manner for the recommended interval, this single remedy is effective for the vast majority of patients in keeping "dry eye" symptoms to a minimum. If preservative-free tears are used, there is no hazard preservative-induced irritation from over-use. There are many brands of preservative-free artificial tears available at the pharmacy or grocery store (i.e. Systane, Blink, Optive, Refresh Plus, Thera-Tears, and GenTeal). Some over-the-counter lubrication drops that come in a large bottle contain a “preservative”. Eye drop preservatives, such as benzalkonium chloride (BAK), tend to accumulate in the tear film and irritate the ocular surface. “Disappearing Preservative” artificial tears are expensive, but are safe to use if desired. Artificial tears WITH a preservative should be avoided right after surgery and are better tolerated when only used once or twice per day.

Checklist of Over-the-Counter Remedies to Alleviate Dry Eyes:

• Use over-the-counter preservative-free lubricating artificial tears at least 4 times per day or more if desired, especially following LASIK
• Avoid dehydration by drinking plenty of water. Staying hydrated helps produce natural tears more effectively
• Avoid “too much” caffeine, which has a drying/diuretic effect
• Use gel lubrication at night. The thicker forms of over-the-counter lubrication, such as GenTeal Gel, are more viscous and last longer. They tend to blur the vision more, so they are most useful while sleeping.
• Add dietary omega-3 fatty acids, such as 1000mg molecularly distilled fish oil oral soft gels, to optimize the oily portion of the tear film and prevent tear evaporation
• Baby shampoo eyelid scrubs can remove certain irritating oils that accumulate on the eyelids and restore the balance between the three tear film components. (Do not attempt this or rubbing eyes for one month after having LASIK) Some inflammatory skin conditions, such as ocular rosacea and seborrheic dermatitis or blepharitis, are associated with problems with the lipid component of the tear film. If the lipid component breaks down, no amount of supplemental artificial tears will solve the problem because the tear film will evaporate too quickly. Daily baby shampoo eyelid hygiene is gentle on the eyes and can inexpensively control the problem
• Use emollient eye drops, such as Soothe or Endura, which contain lipid emollient lubricants to "stabilize the lipid layer of the tears and promote overall tear stability.
• Use a room humidifier to humidify environmental air. This can make a very big difference. By putting the humidifier in the bedroom or office, moist air can actually keep the eye surface hydrated, instead of dry air depleting moisture out of the eyes.

Prescription Treatments Can Help Treat Severe Dry Eyes

• Restasis™ eye drops improve natural tear production. By reducing ocular surface inflammation, the tear glands are able to produce natural tears more efficiently
• Steroid eye drops treating inflammation on the ocular surface has been shown to increase tear production to improve eye comfort
• Low dose oral doxycycline pills treat any underlying blepharitis and stabilize the tear film. At a low dose, doxycycline has anti-inflammatory properties, rather than antibiotic properties, to treat rosacea and blepharitis
• Punctual plugs to help tears stay in the eye longer. Eye drops and tears naturally drain through tiny openings located into the inner angle of the eyelids to the nasal passages. Placing tiny plugs in each opening, called a puncta, can reduce the drainage of tears away from the eye surface
• Autologous serum eye drops are manufactured by drawing the patient's own blood and concentrating the serum by centrifugation. Serum eye drops contain natural growth factors and immunoglobulins that can heal and nurture the ocular surface. However, these are almost never needed to treat dry eyes after LASIK.

What Other Factors Can Affect Eye Comfort?

• Age. Tear glands become less efficient with age.
• Use of certain medicines. Antihistamines, antidepressants, diuretics, certain blood pressure medicines, and birth control pills can decrease tear production
• Intake of alcohol. The diuretic effect can cause dehydration
• Cigarette smoking. The particulate nature of cigarette smoke can be directly irritating to the eyes, and the chemicals that are inhaled can adversely affect tear secretion and quality
• Hormone changes. It is common for women to notice worsening of dry eye symptoms after menopause.
• Computer Vision Syndrome and blinking frequency. People blink less frequently when they intensely concentrate on a computer, drive or read. This can lead to drying of the eye surface. Right after LASIK, having artificial tears readily available at work, home and in the car can remedy this problem. Remember “20-20-20”, which means taking a 20 second break every 20 minutes and look at least 20 feet in the distance. This will rest and rehydrate your eyes
• Use of sedatives, sleep aids, or muscle relaxants. These all can decrease muscle tension, and can lead to incomplete closure of the eyes during sleep. If the eyes are slightly unclosed, tear evaporation can create significant dry-eye symptoms most notable upon arising in the morning
• Certain make-up products, particularly eyeliners, can affect the lipid tear layer, which is produced on the eyelid margin, and decrease tear break-up time
• Air travel. On commercial aircraft, cabin air is dehumidified and cooled. If travelling by air soon after LASIK, it is advisable to bring and use artificial tears more frequently on the plane
• Use of any vasoconstrictors (Visine, Naphcon-A, Opcon-A) to "get the red out". Using these drops may temporarily make you eyes look less red, but do not treat the underlying cause of the redness, which is usually dryness.
• Use of tears containing polyvinyl alcohol as the vehicle, which decreases the surface tension of the tears and leads to a less stable tear film.
• External environment & climate can affect eye comfort. Be aware of the impact of breezes from heaters, fans and air conditioners, which cause the tear film to evaporate more quickly.

Proactively Treat Dry Eye before LASIK

Careful preoperative screening can prevent postoperative Dry Eye. A previous history of dry eyes is one of the most important parts of screening evaluation for laser vision correction. Many patients are intolerant of contact lenses because of underlying dry eye. Any symptom of eye irritation, including sandy-gritty irritation, dryness, burning, or foreign body sensation, suggests the possibility of dry eye. Pre-existing dry eye doesn't necessarily affect the efficacy or safety of LASIK, but it is a risk factor for having Dry Eye after LASIK. If a patient has dry eye symptoms preoperatively, it's important to maximize the health of the ocular surface prior to surgery.

Consider Alternatives to LASIK

• Epi-LASIK (PRK) is a potential alternative for patients who are not candidates for LASIK. PRK is not quite as popular as LASIK because of a longer recovery time and more initial discomfort. Recent improvements in PRK have reduced discomfort and improved final results to be equal to LASIK. Since there is no corneal flap in PRK, there is less dryness afterward. PRK is suitable for patients with thin corneas or occupations that predispose them to ocular trauma; or who have anatomic abnormalities such as flat corneas, steep corneas, asymmetric corneas, and deep-set eyes; or who have had filtering blebs, retinal detachment surgery, or glaucoma surgery. The loss of corneal sensation is minimized with PRK compared with LASIK.
• Visian Implantable Collamer Lens (ICL) can treat a wide range (-3 to -20 diopters) of extreme nearsightedness. The FDA approved the Visian ICL in 2005. The ICL is a lens implant, instead of laser vision correction. It does not cause or worsen dry eyes.

My goal is for patients achieve excellent vision AND optimum eye comfort. Using this guide as a reference tool, I personalize my specific recommendations to the needs of each patient at my San Jose LASIK office.

References

1. Stern ME, Beuerman RW, Fox RI, et al. The pathology of dry eye: the interaction between the ocular surface and lacrimal glands.Cornea.1998;17:584-9.
2. Kanellopoulos AJ, Pallikaris IG, Donnenfeld ED, et al. Comparison of corneal sensation following photorefractive keratectomy and laser in situ keratomileusis. J Cataract Refract Surg. 1997;23:34-8.
3. Chuck RS, Quiros PA, Perez AC, et al. Corneal sensation after laser in situ keratomileusis. J Cataract Refract Surg. 2000;26:337-9.
4. Yu EY, Leung A, Rao S, et al. Effect of laser in situ keratomileusis on tear stability. Ophthalmology. 2000;107:2131-5.
5. Hovanesian JA, Maloney RK. Symptoms of dry eye and recurrent erosion syndrome after refractive surgery.J Cataract Refract Surg.2001;27:577-84.
6. Donnenfeld E, Solomon K, Perry H, et al. The effect of hinge position on corneal sensation and dry eye following LASIK. Ophthalmology. 2003;110:1023-9.
7. Toda I, Asano-Kato N, Hori-Komai Y, et al. Laser-assisted in situ keratomileusis for patients with dry eye. Arch Ophthalmol. 2002;120:1024-8.
8. Campos M, Hertzog L, Garbus JJ, et al. Corneal sensitivity after photorefractive keratectomy. Am J Ophthalmol. 1992;114:51-4.
9. Litwak S, Zadok D, Garcia-de Quevedo V, et al. Laser-assisted subepithelial keratectomy versus photorefractive keratectomy for the correction of myopia. A prospective comparative study. J Cataract Refract Surg. 2002;28:1330-3.

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