The topical use of secretagogues, usually acetylcholine or its analogs, have been tried but generally have intolerable side effects, such as miosis and accommodative spasm, and minimal or evanescent increased tearing.

In glaucoma patients with dry eyes, however, pilocarpine, an old but effective glaucoma treatment, may provide help for both conditions in patients who tolerate the small pupil and are old enough to avoid accommodative visual change.

12.7Moisture Preservation and Oral Medications

12.7.1Moisture Chambers, Humidifiers, and Contact Lenses

The basic idea behind so-called moisture chambers is to enclose the eye so that evaporative loss of tears is minimized. Since approximately 25% of tears are lost by way of evaporation, this strategy will preserve tears in the eye for a longer time by limiting evaporation. These devices range from a wrap-around sunglass design to side shields adapted to regular eyeglasses. Sunglasses may be adapted with sponge-like lining to help retard evaporation.

During prolonged exposure in dry environments, such as airline trips, devices such as eccoeye shields with moisturizing sponges may prove helpful. A selection of these adjuncts may be found on a website http://www.dryeyezone.com.

For those patients experiencing moderate or severe episodic or chronic dry eye, the use of humidifiers is also suggested. The preference for the newer ultrasonic cold air humidifiers over the older warm air humidiÞers (which are more prone to spread potential infection on larger droplets) is noted.

For those individuals with pets or who live in areas with particulate smog, the use of air filters such as those with hepa filters may prove very helpful.

The patient is asked to remain mindful of environmental conditions, indoors and outside, changes in their own physical sense of wellbeing, stamina, and health, and any changes

in systemic medications that would indicate the need for either self-adjustment or consultation for change in management.

12.7.2 Punctal Plugs

The use of punctal plugs can be an effective step in treating moderate-to-severe dry eye that is unresponsive to artiÞcial teardrops and ointments. The tears drain into the nose via the tear ducts, and blocking this outflow is a reasonable strategy to keep the tears in the eye for a longer time.

Punctual plugs increase the comfort level in the eyes and lower the frequency of the need for artiÞcial tears in most dry eye patients. The decreased artiÞcial tear use may be economically beneÞcial, considering the high cost of preservative-free artiÞcial tears.

It is emphasized that choices regarding punctal occlusion are the domain of the experienced ophthalmologist.

Temporary punctal occlusion with collagen implants may be considered to ascertain if the punctal blockage will help reduce dry eye symptoms and also to rule out excessive tearing due to such blockage. However, a failure to respond to a temporary trial with these plugs is difÞcult to interpret. In many patients, they do not provide sufÞcient occlusion to make any conclusion about the beneÞt of more deÞnitive punctal occlusion.

There are a variety of punctal plugs available. Most silicone punctal plugs are umbrella-shaped, and the top part of the punctal plug rests on the eyelid surface.

A different type of punctal plug (Herrick plug) is completely embedded within the tear ducts (the canaliculi).

Another type of punctal plug is made of a thermosensitive, hydrophobic acrylic polymer that changes from a rigid solid to a soft, cohesive gel when its temperature changes from room temperature to body temperature.

About 40% of punctal plugs are lost within 6 months of insertion, usually within the initial monthÕs post-insertion, mostly due to spontaneous extrusion.