Slit Lamp Examination allows a surgeon to examine the tear film, looking for debris which may be present in dry eyes and assess the Tear Break Up Time.

Tear Break-Up Time (TBUT) is one of the methods used in the evaluation for dry eye syndrome. TBUT is the time elapsed between a complete blink and the development of the first random dry spot on the tear film. For this assessment the ophthalmologist asks the patient not to blink, and then times the interval until dry spots begin to occur on the corneal surface.

The normal blink interval is every 5 seconds and tear film is typically stable for about 10 seconds. A TBUT of less than 10 seconds is considered abnormal and suggests an unstable tear film. Mucin-deficient states and lipid abnormalities produce an unstable tear film and result in a rapid TBUT. A rapid TBUT is common to patients Schirmer's Testwith dry eye syndrome.

Schirmer's Tests involve placing a thin paper tear strip inside the lower eyelid for a specified period of time (usually 5 minutes). The tear strip is then removed and the length of the strip that is wet from tears is measured and compared to a standard. Individuals with dry eye syndrome will have less wetting of the tear strip than those with normal tear production.

Rose Bengal Staining is yet another method of evaluating patients for dry eye syndrome. Rose bengal is a water soluble dye, that when applied to the ocular surface, is absorbed by devitalized (sick) epithelial cells and mucin. Positive staining of the conjunctiva with rose bengal is consistent with a diagnosis of dry eye syndrome.

People with Schirmer I test scores of less than 10 mm can be categorized into two groups: those with mild Rose Bengal staining and those with severe Rose Bengal staining. Over 90% of the group with severe Rose Bengal staining have lost the ability to produce tears in response to sensory stimulation.

Contact Lens Intolerance: People who find wearing contact lenses uncomfortable have a higher risk factor for dry eyes after LASIK. These patients require a thorough screening and may still be acceptable candidates for LASIK once they have been given the proper preoperative treatment.

After identifying potential dry-eye suspects, preventive therapy is key to managing postoperative symptoms. There are a variety of ways that you can treat patients prior to, and after LASIK. Artificial tear supplementation is the main focus of treatment after LASIK. There are many pre LASIK treatments available for lid disease and/or dry eye symptoms such as hot compresses and lid hygiene for blepharitis. The use of oral doxycycline (an antibiotic) in patients with rosacea and meibomiam gland dysfunction, 100 mg twice a day for 2 weeks, and 100 mg once a day for a month before LASIK can make an enormous difference in tear function.

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Dr. Murray McFadden
(BSc, MD, FRCS(C), Diplomate of the
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This page last updated on September 14, 2001.
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