Dry Eye
A day doesn’t go by for an ophthalmologist when there isn’t at least one patient with symptoms from dry eyes. Dry eyes are an exceedingly common but often underrated cause of ocular discomfort. Patients who complain that their eyes feel tired, heavy, itchy, sticky, or gritty can all be describing symptoms of dry eyes. Sometimes, a dry ocular surface can result in blurry vision.
Background
Basal tears are secreted by the small accessory lacrimal glands and they provide the ever-present tear film which coats the surface of the eye keeping it constantly lubricated. The larger main lacrimal gland is responsible for reflex tearing which can be stimulated by any irritant to the ocular surface. Most dry eye problems are due to an insufficient production of basal tears. Tears are constantly being secreted onto the surface of the eye but they usually disappear quickly as they are produced. The two main routes by which tears disappear are drainage and evaporation. The tears drain through small openings in the inner corners of the eyelids called puncta and from there to the lacrimal sac where they eventually find their way to the nasal cavity. Normal blinking of the eyes is necessary for the tears to be pumped into the tear drainage ducts. The blink protects the eye from over-exposure to the surrounding air and it also replenishes the tear film over the ocular surface. Tear evaporation will occur more rapidly in the absence of an effective blink mechanism so that dry eye problems can occur in spite of an adequate production of basal tears if proper blinking is impaired.
Factors that may result in inadequate tear production are advanced age, many medications including antihistamines, antidepressants, birth control pills, and medical conditions such as Sjogren’s syndrome or rheumatoid arthritis. Excessive evaporation may occur with conditions that interfere with normal blinking such as eyelid laxity, Bell’s palsy or Parkinsonism. A dry environment such as that near heating vents or fans will cause more rapid evaporation of tears. Tear evaporation will also occur more readily during activities that are physiologically associated with less blinking such as reading, computer work, and driving.
Treatment
The mainstay of treatment for dry eyes is ocular lubricant preparations. Ointments are the longest lasting but will cause temporary blurring of vision and are thus best used at bedtime. There are many different artificial tear eyedrop preparations that contain various wetting agents. These are best used on an “as needed” basis for dry eye symptoms. If drops must be used frequently (more than four times a day), there is potential for toxicity to the ocular surface from the preservatives in these preparations. In those situations, it is preferable to use preservative-free drops that are marketed in single-use containers. Recently, a gel for dry eyes has become available that lasts longer than eyedrops but doesn’t blur the vision as much as ointments.
Another effective approach to treatment of dry eyes is tear conservation by surgical obstruction of tear drainage. This is usually accomplished with tiny silicone plugs that are easily inserted into the lacrimal puncta in the office setting.
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