Having dry eyes can cause many symptoms of irritation and dryness but there are many tests that can be performed to provide a quantitative measure of the dryness. These special tests allow an eye doctor to make an objective decision about how to treat and manage the dry eye condition.
Types of Dry Eyes
There are two main types of dry eye syndromes. The most common type of dry eyes is called evaporative dry eye. The other, less common, type is aqueous deficient dry eye.
Each type of dry eye has different tests which are used to measure the severity of the condition.
It is common for there to be overlap between the two types of dry eyes and for someone to have symptoms of both types of dry eye.
Symptoms of Dry Eye Syndrome
The two most common symptoms of dry eye syndrome are irritation on the front of the eye and the sensation of dryness in the eyes.
Other symptoms that may occur with dry eyes include redness around the eyes, watering or tearing, and blurry vision that improves with blinking.
Testing for Dry Eyes
For objective data on how dry the eyes are or how severe the dry eye is, there are a number of tests or procedures that can be performed.
Using dyes in the form of eye drops can provide visualization of the damage associated with dry eyes. These dyes are referred to as vital dyes.
There are tests which evaluate the production of the tears and measure the rate at which tears are produced.
Since one of the main causes of dry eyes is a deficiency of the oil glands in the eyelid, there is an imaging procedure which allows the oil glands to be examined and compared to a normal, healthy eye.
Vital Dyes for Dry Eyes
There are three vital dyes which are commonly used to evaluate for dry eyes.
Fluorescein is a yellow dye that is often used to measure how quickly the tear film breaks apart on the eye. It can also show areas of chronic damage on the front surface of the eye.
Lissamine green and rose bengal are both dyes which are used to highlight the dead cells on the cornea and conjunctiva. These dyes will stain the broken and damaged areas of the eye which show how severe the dry eye condition is.
Tear Production Tests for Dry Eye
There are tests which assess the rate of tear production and quality of the tears produced.
Phenol red thread test and Shirmer’s test are two of the most well known and accepted tests for this.
If there is a deficiency in the production of the tears, the eyes will often be dry for a lack of moisture.
By measuring the tear production, this can ruled out as a cause of dry eyes and can be monitored with treatment to evaluate the success of the treatment.
Imaging Oil Glands for Dry Eyes
The oil glands in the eyelid are an important part of a healthy tear film to reduce the presence of dry eyes.
Meibography is a process in which a special infrared camera is used to image the oil glands in the lower eyelid. If the glands are weak, misshapen, missing, or damaged it can result in dry eye symptoms.