We now know with certainty that dry eye diseases affects vision, so that, in addition to ocular discomfort and red eyes, patients may also suffer functional impairment. Dry eye disease can produce visual symptoms by two mechanisms.
Fairly early in the course of the disease, growing tear film instability can lead to rapid tear film evaporation between blinks, with an associated decrease in vision. Patient often compensate for this by blinking frequently, which restores the continuity of the tear film, and clears vision for a few seconds.
Patients with an unstable tear film often experience changes in vision when they are doing intense close work, such as reading or using the computer, or when they become tired-as all of these conditions reduce blink rare. Because the patient can blink while looking at a visual acuity chart (and get an instant boost in vision), this form of acuity is is often missed in standard testing.
In later stages of the disease there can be physical alteration of the ocular surface that affects vision. Superficial surface damage or breakdown can produce ocular surface irregularity that cannot be corrected by blinking. The specific problems may range from adherent mucus or filaments on the corneal surface to advanced surface disease. This type of visual impairment does not significantly improve on blink, and is more easily detected during routine testing.
Behavioral modifications can be made in our environment to reduce the dry eye visual impairments we experience. Lowering our computer monitor, increasing ambient humidity in our work and home, and avoiding air currents are some simple changes that will help reduce the visual impairment we experience with dry eyes.
Author: Dr. Thad Daniel
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