The diagnosis of dry eyes requires examination of the ocular surface by an ophthalmologist to assess for damage caused by insufficient tear production and excessive dryness.
The test involves the application of special eye drops containing a non-toxic dye called lissamine green. This dye stains areas of the ocular surface that have been damaged by persistent dryness. These areas are then assessed by the ophthalmologist using a biomicroscope (also called a slit lamp). A scoring system has been developed to rate the severity of these changes and is useful for monitoring dry eye treatment over time.
Another important test for assessing ocular health is the Tear Film Break-Up Time (TBUT) test. The tear film is a thin coating on the surface of the eye that protects and lubricates it.
Eye drops containing fluorescein dye are applied and disperse throughout the tear film. The longer the fluorescein remains evenly distributed in the tear film, the better the quality of the tear film. The ophthalmologist measures the time it takes for the tear film to “break up,” which is an important indicator of tear film integrity. Fluorescein also allows detection of small areas on the cornea where surface cells have been lost due to dryness or other forms of damage.
The fluorescein and lissamine green dyes used for ocular staining may cause mild irritation. A green stain on the surface of the eye may be present for several hours.
