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Understanding 3 and 9 O'clock Staining

BY ROY W. PRESTON, OD
OCTOBER 1998

The 3 and 9 o'clock fluorescein stain corresponds to those areas of the cornea that are not normally covered by a rigid contact lens or the eyelids when they are in the primary open position. It is usually a result of the lens riding laterally on the lens riding laterally on the cornea, which is common in high astigmats. This one-sided staining is also often accompanied by a bright arc stain and an indentation at the limbus where the edge of the lens rests.

Based upon my own clinical experience and on what I have learned from others in the years since the development of the modern hard corneal contact lens, I believe that the cause of 3 and 9 o'clock staining is incomplete blinking, which causes corneal desiccation on either side of the contact lens. The desiccation occurs as a result of the extended drying time that exists between one complete blink and the next. An accompanying sign is a dirty contact lens with areas of dried matter and mucus on the parts of the lens that are exposed in the normal palpebral fissure. Observing the stain is usually sufficient to diagnose incomplete blinking, but watching the upper lid will confirm it. During the blink reflex of incomplete blinkers, the upper lid will just twitch, closing only one or two millimeters at most. When complete closure does occur, it is usually willful and not a reflex.

Eliminate the Cause

Treatment for 3 and 9 o'clock staining consists of eliminating the cause of the incomplete blink, then encouraging the patient to blink completely and excessively to train him to blink normally at the subconscious level. The cause of incomplete blinking is usually one of the following: a foreign body sensation with the blink due to an improperly shaped edge (too thick, too thin or too sharp), and inappropriate bevel or blend, or lens movement during the blink that causes the bevel or blend areas to impinge on the pupil and distort vision.

Using the following tests, you can diagnose whether a foreign body sensation is caused by the edge and is therefore felt by the upper lid, or is caused by the bevel and is therefore felt by the cornea. Instruct the patient to close his eyes, keeping only a slit open to maintain vision. Then instruct him to look at a fixed object while moving his head from side to side. The partial closure of the eye puts weight on the lens, and the lateral head movement will cause the lens to slide across the cornea. If the bevel of the lens is causing the discomfort, this will intensify the sensation. Use a retinoscope to determine whether the bevel or the blend is impinging on the visual area. If you can see any portion of the bevel, the patient can see it also, although he may be otherwise asymptomatic. You can observe the blend by moving the lens in your palm and studying the light reflex as it passes over the edge. Sharp areas appear as a sharp break in the light reflex. The light reflex should pass smoothly over the edge bevel and blend. The remedy for a bevel or blend that impinges on the pupil is usually a larger lens or a lens refit to improve centration. Increased discomfort when instructing the patient to open his eyes wide and blink rapidly several times implicates the edge as the cause of the incomplete blink. Look for thick or sharp edges under the biomicroscope while holding the lens with the edge facing you.

Blinking 101

Once you have determined the cause of the incomplete blink, you must retrain the patient to blink properly. Explain to the patient the importance of the blink, demonstrate complete blinks and encourage over-blinking. Have the patient watch for dirty lenses, and tell family members to watch for the lid twitch and to remind the patient to blink properly.

Dr. Preston practiced in Seattle, Wash. for 40 years until his recent retirement.