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Dry Eye

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Dry Eye

 

What is it?

The front surface of the eye is kept moist by a tear film made up of three layers. The more usually affected middle layer is produced by small glands scattered over the surface of the conjunctiva (the white of the eye). When production is inadequate, the tear film becomes thin. It doesn't lubricate the eye properly. Then the eye feels uncomfortable, gritty or even painful. If this discomfort is sufficient, the main lacrimal (tear) gland is stimulated. It is right under the upper lid at the outer edge.

A lot of tears can be produced by this gland, which is also responsible for the tears of crying. If this happens, the eye then waters. So the situation can develop where the eye is basically dry, but because of the discomfort from this, it then waters! Another reason exists for watering of the eye. There is a channel called the lacrimal (tear) draining system. This starts at an upper and lower opening (punctum) on the edge of the lid, a short distance from the inner corner of the eye. (These are easily seen in a mirror.)

Then, two fine ducts, or canaliculi, meet together and enter a receptacle called the lacrimal sac. This sac in turn leads down a bony channel in the side of the nose called the naso-lacrimal duct. If for some reason the system is not working properly, the eye fills with tears and then waters. Constant watering of the eye is a very frustrating symptom. If a blockage is at the end of the channel an infection can occur. This makes the eye sticky. This is especially true of a blocked channel in babies.
 
How does it occur ?
DRY EYE The small tear-producing glands may just fail, or else they may be destroyed by the body's own defence immune system. Patients with this condition often complain of dryness of other areas like the mouth. It is known as Sjogren's syndrome. WATERING EYE The first problem concerns the punctum. If the lid is too loose, it can fall away from the surface of the eye. Then the opening is no longer in contact with the eye, a condition called ectropion. The punctum can also have a tight or closed opening. The tears cannot then get through. Further along the system, the canaliculus can be blocked before opening into the sac. Lastly, the naso-lacrimal duct to the nose can be blocked. These blockages can result from earlier eye infections and scarring. In small infants, the end of the duct opening into the nose may be blocked by a layer of tissue.
 

Treatment Involved …

DRY EYE The diagnosis is made after examination on a piece of equipment called a slit lamp. Either a red dye or an orange dye is used on the eye during the examination. Treatment is by means of artificial tear drops. These are used about four times a day. Lubricating ointment can be used at night. Both can usually be bought at a pharmacist without prescription. Special acetyl cysteine drops are given in more severe cases where the mucus foundation layer is affected. Also in more advanced cases, permanent closure of the punctum by cautery may be required. This prevents the tears being removed from the eye.

WATERING EYE All children with a blocked duct must be given a chance to cure themselves. If they are not better by the age of a year, or if the eye is very sticky and troublesome, a fine tube is passed all the way down the duct under anaesthetic. This should give a permanent cure. When a blockage is suspected in an adult, and if the punctum of the lid is not at fault, the surgeon must decide where the problem lies. After an anaesthetic eye drop, the punctum is opened wide and a tube on the end of a syringe is passed down the canaliculus. It is then passed into the sac and water is squirted through. If the patient can feel the water at the back of the throat, the passage is clear. If not, it is blocked. The position of the tube tells the surgeon if the block is in the canaliculus or lower in the duct. Adults can have it passed all the way through the duct with a local anaesthetic. This is uncomfortable and not very likely to be curative. For a tight punctum, stretching may work. Or else a small cut to widen the opening can be made. For a blocked canaliculus or duct, a large operation is done called a DCR (dacryocystorhinostomy). It involves opening the sac and breaking an opening in the bone at the side of the nose. The tears can then flow straight to the nose, bypassing the duct. If the canaliculus is blocked, a plastic tube is left in the system for 3 months.
 

After Treatment …

Use of artificial tear drops should provide immediate relief. These drops should be used forever. There is no need for regular clinic checks after starting the treatment. The drops may sometimes cause some feeling of stickiness or a little crusting of the lid. WATERING EYE Surgery should completely cure infants, and there is no need for follow-up. In adults, surgery is only performed for severe disability, and the patient needs to be reasonably fit. It is a big operation and the success rate is less than l00%. After surgery the nose should not be blown, to allow for healing. If a plastic tube is placed, then watering will continue until its removal.
 

If Left Untreated …

DRY EYE Without treatment, discomfort continues indefinitely. The eye will be more likely to get infected as well. WATERING EYE Continued watering of the eye can often be tolerated. Recurrent infections can also be treated. If the sac becomes infected it can swell up and cause tremendous discomfort. Then a lot of treatment is needed and surgery becomes necessary to remove the sac.

 

 

 

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