Dry Eye

Optimizing Eye Comfort and Managing "Dry Eye" 

The normal cornea is very sensitive to touch, foreign body sensation, and mild superficial injury. Anyone who has ever had an eye infection, contact lens-related irritation or corneal scratch knows this to be true. A network of sensory nerves provides this exquisite sensitivity. In LASIK, creation of the flap causes some of these nerves to be cut, which actually diminishes sensitivity. I tell patients that it is as if "the phone lines are down;" such that the eye surface cannot send requests to the tear gland when additional moisture is needed. Typically, these nerves do grow back, and sensitivity returns to reasonably normal levels within several months of treatment.

For this reason, we tell all patients that it is very important to use artificial tear eye drops on a very frequent basis for at least first 2 or 3 months after LASIK, and longer if desired to maintain or increase comfort. I advise use of tears as often as every couple of hours through the day, or whenever one remembers to put in a drop. If preservative-free tears are used, there is no hazard to over-use. There are many formulations and brands of artificial tears available. We like and currently recommend Thera-Tears, GenTeal, Systane ,and Soothe, among others. If used in a reasonably diligent fashion for the recommended interval, "dry eye" symptoms can be reduced to a manageable minimum.

It is important to recognize the influence of climate and environment on eye comfort, and on tear requirements. Ambient temperature and humidity are critical factors. It is my experience that far fewer people complain about "dry eyes" in regions where the air is moist and cool (such as Seattle, and the San Francisco bay area), compared to other regions where air quality is more dry and hot (Palm Springs, San Bernardino, Bakersfield, Las Vegas, etc.).

In LA it is often hot, dry, dusty and smoggy when outdoors. When weather conditions include high pressure over the desert, our Riverside weather make for particularly warm, windy, dry conditions. Humidity, wind, weather and air quality clearly can aggravate awareness of "dry eye" and can be the difference between being comfortable or not. There is not necessarily any escape by heading indoors, as virtually all central heating and air conditioning systems also remove moisture from the "conditioned" air.  In commercial aircraft, the cabin air is pressurized but is also de-humidified, so I encourage the use of artificial tears as often as every 20 - 30 minutes while in flight (if not asleep). 

Moving air and air turbulence are also significant factors affecting eye comfort and wetting.  Moving air and turbulence dramatically increase evaporative loss of the water portion of the tear film.  Examples include (a) driving in a convertible with the top down, (b) using a hair dryer to style and blow-dry hair, (c) simply feeling a draft or breeze.  Even a slight amount of air movement can have a significant adverse effect upon eye comfort, and it sometimes affords great relief simply to adjust the fins on a vent directing air movement from central heating and air conditioning systems .  The same holds true for A/C in a car, where there can be a trade-off between feeling that cool breeze on your face and maintaining good eye comfort (folks reading this where the climate is colder should simply substitute "warm" for "cold" and "heating" for "A/C" in the above example).

Some surgeons and microkeratome manufacturers make a big deal about the location of the 'hinge' of the LASIK flap. Some research suggests that the majority of sensory nerves grow into the cornea from the horizontal direction (from both nasal and temporal sides). There is the suggestion that creation of a LASIK flap with a superior hinge cuts through both nasal and temporal nerves, whereas creation of a flap with a nasal hinge cuts through only the nerves on the temporal side, sparing the nasal-side nerves. I have found this not to be particularly relevant. If it were important, there should be a higher percentage of patients with 'dry eye' symptoms after superior-hinge LASIK than after nasal-hinge surgery. I have not noticed this trend with any regularity.

While I do find it common for post-LASIK patients to have mild dry eye issues, these are typically easily treatable with some combination of the simple steps outlined below. It is with extreme rarity that I encounter any patient manifesting profound dryness or ocular surface disease.

Here's my routine, and the rationale behind it:

  • The normal human tear film is about 98% water (with dissolved minerals or "salts" including sodium, potassium and calcium), about 1% lipid (an oily film that reduces evaporation, reduces "tear breakup" and helps the lids glide smoothly over the corneal surface), and about 1% mucopolysaccharide (the "mucus" component, long water-soluble molecules that further stabilize the tear film, and promote adherence to the corneal epithelium). The watery portion of human tears are created by a combination of the tear gland and special mucin-secreting cells on the ocular surface.

Maintaining good hydration is essential to keeping the eyes comfortable, and I encourage three things to accomplish this:

    • Drinking adequate water or fluids ;
    • Use of artificial tears at least for the first 8-12 weeks after LASIK; and thereafter as desired to maintain comfort;
    • Use of a small room humidifier when appropriate.


Humidifiers are widely available at pharmacies, linen and bath supply stores, Costco and other retail sources. Many people already own one if they have kids, as they are commonly recommended as adjunct therapy for children with respiratory problems (croup, asthma, bronchitis, bad colds, etc.). They range in cost from about $25 to over $100, but very decent ones are typically around $50 (which is about the same as the cost of three bottles of "vanishing preservative" artificial tears). I advise putting the humidifier in the room where it will do the most good (bedroom, home office, etc.). Then, instead of dry air sucking moisture out of the eyes, moist air can actually keep the eye surface comfortable.

  • Good lid hygiene is important to maintenance of a good lipid tear layer. This is where all the advice about blepharitis, lid scrubs, hot compresses lid hygiene and lid massage comes in. If the lipid component breaks down, no amount of artificial tears will solve the problem. We treat blepharitis when appropriate, and endorse the use of moisturizing creams and/or lotions for the eyelid skin in those people that desire to use these products.
  • In some people, beneficial effects are achieved with omega-3 fatty acid dietary supplements.   Several companies offer over-the-counter supplements with such oils and fatty acids including " Thera-Tears Nutrition " and others.
  • A commercially available spray called Soothe contains lubricants and lipids, claiming to "stabilize the lipid layer of the tears" and promote overall tear stability.
  • Be aware of other factors that can affect the water and lipid layer of tear film. These include:
    • Use of diuretics, as these medications remove water from the system;
    • Use of antihistamines, either topical (eye drop) or systemic can have a drying effect, as they reduce secretions; the tear gland after all is a secretory gland too. 
    • Intake of alcohol.   Even when consumed in modest or small quantities, alcohol gets into the bloodstream and the tears.  It reduces surface tension of the tear film, leading to increased evaporation.
    • Cigarette smoking.  The particulate nature of cigarette smoke can be directly irritating to the eyes, and the chemicals that are inhaled can adversely affect both ocular surface blood flow, tear secretion, and tear quality.
    • 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 open even a little, evaporative tear loss can create significant dry-eye symptoms most notable upon arising in the morning.
    • Use of cologne, perfume, fragrance, or after-shave on or around the face.  Why?  All these substances are bottled in liquid containing -- you guessed it -- alcohol, so each spray or splash is basically giving the eyes a large, direct dose of the bad stuff we described above.
    • Use of make-up, particularly certain eye-liners which can affect the lipid layer of the tears and decrease tear break-up time. I support use of hypo-allergenic cosmetics, taking all the usual precautions, etc.;
    • Air travel .  On commercial and private aircraft, cabin air is very dry, as the air is both dehumidified and cooled.  If travelling by air within 3 months of LASIK, it is advisable to use artificial tears as often as every half hour while the plane is in flight (unless your eyes are closed as in sleep).
    • Use of any "get the red out" drops containing vasoconstrictors (Visine, Naphcon-A, Opcon-A and others) because, when the drops wear off, there can be a rebound effect leading to more congestion, more perceived need to use more drops, etc.;
    • Use of tears containing polyvinyl alcohol as the vehicle (Visine is one example, for the same reasons as "alcohol" above);
    • Use of certain medications including Acutane.  Acutane adversely affects oil production by the eyelid meibomian glands, and is actually a known contraindication to LASIK per the FDA guidelines.
    • Blink frequency and disruption of normal blinking .  People that become intensely focused on work, particularly using computers, often blink with decreased frequency.  This can lead to drying of the eye surface. The same factors hold true for people with certain hyper-thyroid conditions.
    • Exposure to hot or dry air in occupational contexts;
    • Exposure to turbulent air, particularly hot and dry turbulent air, as encountered when styling and blow-drying hair and other reasonably common situations (even driving with the window open, or the top down, or the A/C blowing), etc.;
    • Exposure to drafts, breezes, or moving air from central heating or A/C systems.   Often simply adjusting the fins on the duct openings to steer the moving air away from one's face can afford dramatic reduction in discomfort;
    • Exposure to aerosol chemicals or sprays that can be toxic or irritating;
  • Overnight lubrication with ointment or gel if necessary . For some people, it is very helpful to use lubricant ointment or gel preparations just before retiring for the night. We have used Thera-Tears Liqui-Gel and GenTeal Gel   preparations with moderate success.
  • Punctal Plugs . Normally, tears from the eye drain through a tiny channel to the nasal passages. The openings from the eyelid edge into the tear duct (there are normally two in each eye, near the nasal corner of each upper and lower lid) are called the puncta. Placing either a temporary (collagen) or permanent (silicone) plug in the punctum can reduce the rate of drainage of tears from the eye surface. At LA Sight we place the temporary (collagen) plugs with some frequency but use the more permanent (silicone) plugs only very rarely, and only in the lower lid puncta.  I have almost never found it necessary to place plugs in both the lower and upper lid puncta.
  • Prescription medications when necessary . In 2005 the FDA approved Restasis for use in treatment of severe dry eye and ocular surface disease. I have used this on rare occasion with limited success. On extremely rare occasion, other medications may be appropriate including estrogen or androgen cream (these would need to be made up by a compounding pharmacy), Salagen drops (used typically in the context of patients with Sjogren's syndrome), or Diquafosol (not yet FDA-approved).  Dr. Cheng also is aware of research studies involving other drugs and treatment regimens; and may if other methods fail advise participation in one of these investigational studies.
  • Preparation of special Autologous serum-containing tears .  Some experts feel that the addition of serum proteins to preservative-free tears affords a natural and supportive environment to the tear film, which can restore comfort. Serum is a component of human blood (the fluid remaining after clotting factors and blood cells are removed) so requires blood drawing and preparation by a medical professional.  We have found this to be of value after PRK surgery in rare cases but have not employed this to treat dry eye save for very exceptional cases.

The above is an extensive but incomplete list of factors that can cause "dry eye", and a review of suggested remedies. It is our goal that patients achieve excellent vision and optimum eye comfort.  Using the above as a guide and reference, we personalize our recommendations to the needs of each patient. With diligence on everyone's part, we are able to treat those patients that are unhappy, or functionally impaired due to ocular surface symptoms including dry eye.