Dry eye syndrome

Dry eye syndrome is not exclusive to people who have had refractive surgery, however, it has developed into the most common complication after lasik vision correction.

Dry eye symptoms after LASIK occur as a result of the corneal nerves being cut during LASIK. As a consequence, there is an expected decrease in sensory stimulation which results in decreased tear production. Dry eye symptoms progressively disappear within a few weeks (rarely more) as the severed corneal nerves heal.

MOST COMMON COMPLAINTS

Redness, excess watering, burning, excess mucous Sandy gritty feeling, and/or feeling of something foreign in the eye. A blurry or fluctuating vision which improves by blinking and/or the installation of artificial tears. Intolerance to noxious fumes. Some patients are more likely to experience severe dry eye symptoms than others. Pre-operative screening generally provides the information required by the physician and the patient to identify a high-risk situation and make an informed decision. The pre and postoperative treatments that are available usually enable the surgeon to minimize the effects of post-operative dry eye syndrome.

FACTORS THAT CONTRIBUTE TO DRY EYE SYNDROME IN GENERAL

Ageing: The single most important risk factor for Dry Eye. Dry Eye Syndrome affects 75% of people over the age of 65.

Computer Users: Computer users spend hours staring at their terminal ignoring their normal blinking process which is necessary for refreshing the tear film.

Contact Lenses: Dry Eye is a leading cause of contact lens discomfort or intolerance. Soft contacts in particular rapidly evaporate the tears from the eye, causing irritation with possible other effects such as protein deposits and infection.

Disease: Many diseases can result in side effects of Dry Eye Syndrome: Asthma, Sjogren’s Syndrome, Lupus, Rheumatoid Arthritis, Diabetes, Thyroid Abnormality, Acne Rosacea, etc. Environmental Conditions: smoke, fluorescent lights, air pollution, wind, heaters, air conditioning, and dry climates/low humidity can increase tear evaporation.

Medications: Antibiotics, antidepressants, antihistamines, appetite suppressants, beta blockers, blood pressure medication, decongestants, diuretics, oral contraceptives, tranquilizers, over-the-counter vasoconstrictors, and ulcer medication can also decrease the body’s ability to produce lubricating tears.

Specific to Women: Hormonal changes brought on by pregnancy, lactation, oral contraceptives, menstruation, and post menopause can cause dry eye conditions.

FACTORS THAT CONTRIBUTE TO DRY EYE SYMPTOMS AFTER LASIK

Larger flaps in treating hyperopia- 9.5 mm as opposed to 8.5 mm are thought to be creating drier eyes Decreased blink rate – The normal blink interval is every 5 seconds. When there is unilateral de-innervation there is no change in blink rate. When a patient experiences a bilateral decrease in corneal sensation, there’s a decrease in the blink rate of about 30%. Since the corneal nerves are cut during LASIK, there is an expected decrease in sensory stimulation which results in subnormal tear production as well a decreased blink rate. Long time contact lens wearers experience a much lower corneal sensation than normal preoperatively, which also results in decreased blinking. Since the patient blinks less they have poor spreading of tears over the eye, usually resulting in decreased tear clearance from the reduced pump action of the lids. This creates a change in the tear composition which results in inflammation and contributes to the dry eye syndrome. Antidepressants can cause extreme dryness in a lot of patients as well as causing mydriasis (an enlargement if pupil size). A patient can undergo the LASIK procedure with one pupil size and a few months after taking antidepressants have complaints of glare, halos and other previously nonexistant symptoms which are attributed to a large pupil size.

TREATMENT OF DRY EYE SYMPTOMS

Artificial lubricants/tears are the mainstay of therapy for dry eyes. In the more severe cases of dry eye, sustained release tear inserts can be used. Artificial collagen inserts and/or permanent punctal plugs can also be inserted to help preserve the tears that are produced. Steroids and/or cyclosporine may be used to treat patients with dry eyes caused by autoimmune diseases such as keratoconjunctivitis sica, rheumatoid arthritis, etc Tear Replacement with Artificial Tears/Lubricants There are a wide variety of artificial tears available and it may be necessary for a patient to try several different formulations in order to find one that provides the greatest amount of comfort and relief. Artificial tears can be divided into three groups: 1. With preservatives 2. Preservative-free Preservatives help to retard bacterial growth. If the bottle of artificial tears comes in contact with the surface of the eye while instilling the drops, bacteria from the eye can contaminate the remainder of the drops in the bottle. Preservatives prevent this contamination from taking place. Preservatives found in artificial tears can cause itching due to an allergic reaction or can become toxic to the ocular surface, leading to irritation and inflammation. Some patients who require artificial tears more than four times a day may be required to use preservative-free artificial tear formulations. The various artificial lubricants available for dry eye treatment also have a range of viscosity. In patients with more severe dry eye symptoms, an artificial tear ointment or gel at bedtime helps to provide lubrication throughout the night. These ointments tend to blur vision and therefore have limited usefulness throughout the day. Steroids Corticosteroids are used routinely after LASIK to reduce postoperative inflammation and to relieve dry eye symptoms which are similar to those experienced by people with auto immune disease. Tear Preservation with Temporary Collagen Inserts or Permanent Punctal Plugs Patients that do not find sufficient relief from artificial tears and have displayed evidence of decreased tear production, may be treated by the insertion of punctual inserts or plugs. Both superior and inferior puncta are important in tear drainage. Rods or plugs can be inserted to block the puncta thus stopping the tears that are naturally produced from draining away. Dissolvable punctual collagen inserts can be used as a cost-effective way to evaluate the benefits of permanent punctual occlusion. The collagen inserts are effective for 3-5 days and dissolve in approximately 7-10 days. Permanent punctual plugs do not dissolve. They can be surgically removed if the need arises. Tear Stimulants The use of substances to increase lacrimal gland secretion is another option in the treatment of moderate to the severe dry eye. They have been used both topically and systemically. In order for tear stimulants to work, there must be adequate functional lacrimal tissue present. Tear Replacement with Sustained Release Tear Inserts Sustained release tear inserts reduce the necessity for frequent installation of artificial tears. These inserts can be very useful in treating patients with moderate to severe dry eye syndrome, however, they tend to blur the vision several hours after insertion. Hormones Hormone deficiencies (i.e. estrogen) have a strong link to dry eyes. Estrogen may be beneficial to menopausal and postmenopausal patients with dry eye syndrome. The decision to use systemic estrogen should be made after a patient has been diagnosed as having an estrogen deficiency with due consideration for all other potential side effects. Cyclosporine In cases where a patient displays dry eye symptoms prior to LASIK, some patients are now being treated with cyclosporine 0.05% pre and post-operatively. Preoperative treatment requires that the patient use the cyclosporine twice a day for a month. Then they go back on the cyclosporine within 24 hours of surgery.Larger flaps in treating hyperopia- 9.5 mm as opposed to 8.5 mm are thought to be creating drier eyes Decreased blink rate – The normal blink interval is every 5 seconds. When there is unilateral de-innervation there is no change in blink rate. When a patient experiences a bilateral decrease in corneal sensation, there’s a decrease in the blink rate of about 30%. Since the corneal nerves are cut during LASIK, there is an expected decrease in sensory stimulation which results in subnormal tear production as well a decreased blink rate. Long time contact lens wearers experience a much lower corneal sensation than normal preoperatively, which also results in decreased blinking. Since the patient blinks less they have poor spreading of tears over the eye, usually resulting in decreased tear clearance from the reduced pump action of the lids. This creates a change in the tear composition which results in inflammation and contributes to the dry eye syndrome. Antidepressants can cause extreme dryness in a lot of patients as well as causing mydriasis (an enlargement if pupil size). A patient can undergo the LASIK procedure with one pupil size and a few months after taking antidepressants have complaints of glare, halos and other previously nonexistant symptoms which are attributed to a large pupil size.