Ординатура / Офтальмология / Английские материалы / The Eye Care Sourcebook_Lavine_2001

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openings (puncta). A stagnant pool of tears forms between the eyeball and the lower lid and can cause symptoms such as tearing and irritation. An ectropion does not have to be treated if it is not causing any symptoms, but if it remains for a long time, the skin of the eyelid can shrink. Repair at that point can be more difficult, sometimes requiring a skin graft.

Correcting Ectropion

Many surgical techniques have been developed to treat ectropion. One common method is to remove an entire segment of the lid to shorten it. This is usually done on the side of the eyelid away from the nose. If the ectropion is very mild and is causing a little tearing because the opening (punctum) to the tear drainage system in the rim of the lower lid has fallen away from the eye, a few simple techniques may help. In one technique, tiny burns are placed on the inside surface of the lid on the side toward the nose. This results in a scar that draws the lid margin inward. The other method is to surgically remove a small ellipse of tissue from the inside of the lid. This procedure, along with the scar that results, can draw the lid margin inward and allow the tears to drain out of the eye more normally.

Causes and Symptoms of Entropion

With entropion, irritation of the eye occurs because of the scraping of the eyelashes against the eyeball. Entropion often results from aging. First, there is the increased horizontal laxity of the lower lid, as

discussed with ectropion. Second, there may be a defect in the retractor muscle of the lower eyelid. I would compare it to an old piece of cloth that, as a result of wear and tear, has become stretched and thinned out. These

two factors together create a muscle imbalance in the eyelid that allows it to turn in against the eye. An entropion can also occur in any condition in which there is inflammation or irritation of the eye.

The irritation causes the muscle in the eyelid to go into spasm, and the result is an entropion. However, even in this situation, aging changes in the eyelid often contribute to the problem. Finally, scarring caused by injuries,

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chemical or thermal burns, or certain types of infection can also cause entropion.

Treating Entropion

As with ectropion, there are a variety of ways of dealing with entropion. One should first check the eye closely for any irritative problems, such as dry eye syndrome or blepharitis. Treating any such underlying problems may cause the entropion to resolve and no surgery to be necessary. A stopgap measure that is sometimes used, especially with severe entropions caused by scarring, is placing an extended wear soft contact lens on the eye. It acts as a bandage to shield the eye from the eyelashes. Bandage contact lenses such as this increase the risk of corneal infection, however.

One common surgical technique to reverse the entropion is called a basedown triangle procedure. A wedge of tissue in the shape of a triangle is removed from the inside of the lower lid. It is a simple procedure and often effective in mild cases. Another technique is the removal of an entire segment of the eyelid to shorten it, as is done for ectropion. This corrects the age-related horizontal elongation of the lid that contributes to the problem. Finally, an approach favored by many is to locate the lid’s retractor muscle and repair any defect in it, for example, where it attaches to the eyelid. This method attempts to restore the anatomy of the eyelid to its original state.

Ptosis

Ptosis generally refers to a drooping of the upper eyelid. Some infants are born with ptosis of an eyelid, but for most people, it is something acquired during life. Mild ptosis may be nothing more than a cosmetic problem. More severe ptosis may interfere with vision, however, especially the upper half of one’s field of vision. Occasionally, the drooping eyelid may even change the curvature of the upper part of the cornea and cause blurring of vision in that way.

Causes of Ptosis

Ptosis has many possible causes. The ptosis in newborns is usually caused by a defect in the levator muscle, which is responsible for elevating the upper eyelid

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when you look up and for just keeping it open. In people of all ages, the development of ptosis may indicate a nerve problem. Nerve problems may be due to serious conditions in the brain, such as tumors, strokes, and aneurysms, but can also be caused by injuries, diabetes, and migraine, to name just a few possibilities. Nerve problems causing ptosis in adults often cause other problems at the same time. For example, ptosis can be caused by a palsy of the oculomotor nerve, also known as the third cranial nerve. A palsy of this nerve usually causes at least some eye movement problems and may also cause the pupil to be enlarged. Another kind of nerve problem, Horner’s syndrome, causes mild ptosis along with a slightly smaller pupil on the affected side. It can be caused by either serious or not-so-serious problems.

In older people, ptosis is often caused by a weakening of the levator aponeurosis, a tendonlike sheet that connects the levator muscle to the structures of the eyelid. An uncommon cause of ptosis is myasthenia gravis, a muscle disease that causes weakness and sometimes involves only the muscles around the eyes.

Timing of Surgery

In children, surgery must be performed early if the ptosis is severe enough to cover most of the pupil and thereby cause the vision in the eye to deteriorate, a condition called amblyopia (lazy eye). In moderate cases, the levator muscle can undergo a strengthening procedure called a levator resection. In more severe cases in which the levator muscle is hardly functioning, a sling procedure may need to be done. It often involves taking some fibrous tissue from the thigh (called fascia lata) and using it to suspend the upper eyelid from the muscle of the forehead.

In adults, surgery can be planned once the cause of the problem has been established. For example, if there is any suspicion that myasthenia gravis may be the cause, it

must be ruled out by appropriate testing or by consulting with a neurologist. People with myasthenia gravis often find that their problem becomes worse when they are fatigued or toward the end of the day, although even ordinary age-related changes in the eyelid may sometimes be worse later in the day. A

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Tensilon test can be performed, in which the drug Tensilon is injected into a vein. If the person has myasthenia gravis, the ptosis gets better right after the injection. Since the ptosis in myasthenia gravis responds to medical treatment of the disease, it is important to diagnose this problem before doing any surgery.

In the patient with ptosis, we measure not only the height of the palpebral fissure (the distance between the edge of the upper lid and the edge of the lower lid) but also the distance traveled by the edge of the upper lid as the person’s gaze changes from looking down to looking up. This latter measurement determines how well the levator muscle is functioning and what type of surgery is appropriate. In some cases, when it appears that the ptosis may be affecting vision, we perform a visual field test to see how much of the upper field of vision is being blocked by the droopy eyelid.

For mild ptosis in an adult, the Fasanella-Servat procedure is a time-honored operation that produces very predictable results. It involves removing a few layers from the inside surface of the eyelid. One possible objection to this surgery is that the tissue removed includes some tiny tear glands from the inside of the upper lid, possibly predisposing people to a dry eye syndrome later in life.

A problem with aponeurosis of the levator muscle can be corrected with special techniques. One clue that there may be such a problem is that the horizontal crease in the upper eyelid becomes less prominent, moves higher on the lid, or disappears. The crease is the area where part of the aponeurosis normally attaches to the skin of the lid.

When older people develop ptosis because of a defect in the aponeurosis but still have a levator muscle that functions well, the defect in the aponeurosis can be repaired or the aponeurosis strengthened, often with good results. When the muscle is not functioning well, a resection of the levator muscle, a strengthening procedure, can be done. In the more severe cases, a sling procedure as described earlier can be performed. In all of these procedures, there is a certain amount of unpredictability. This means that the ptosis problem may sometimes be undercorrected or overcorrected, in which case additional surgery may be necessary. Too much correction, especially with a muscle that does not function well, may result in too much exposure of the eye and a drying out of the surface of the eye.

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Cornea and Conjunctiva

Corneal Abrasions and Lacerations

A common eye injury involves the loss of some of the epithelium, the outermost layer of cells of the cornea. A scratch of this kind is called an abrasion. Abrasions can be caused by fingernails, the edge of a sheet of paper, rubbing the eye when a foreign body is in it, or simply anything that contacts the surface of the cornea. These injuries tend to be very painful. Common symptoms include sharp pain, light sensitivity, watering, feeling of something in the eye, or a “sticking” feeling in the eye. The blood vessels in the conjunctiva become engorged, resulting in a reddened appearance, and the upper eyelid may become somewhat droopy.

In the treatment of abrasions, considerations include relieving pain, promoting healing, and preventing infection. Fortunately, abrasions tend to heal quickly, more so in the young than in the elderly. The epithelial cells on the surface of the cornea surrounding the abrasion multiply rapidly and slide in to fill up the space where the abraded cells were lost.

Treating Abrasions

The traditional method of treating corneal abrasions involves keeping the eye patched shut until it is all healed. Generally, antibiotic ointment or drops are instilled in the eye before patching to reduce the risk of infection. That’s

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because the epithelium, like the skin, is the main barrier against infection from bacteria. A dilating eyedrop is sometimes instilled to put the eye at rest and to relieve the spasm that occurs in the injured eye when light enters either eye. However, patching has several disadvantages. First, patching one eye results in a loss of depth perception, making it difficult

to drive or engage in other functions. Second, the tightness of the patch can be uncomfortable. Finally, keeping the eye shut deprives it

of oxygen, which is necessary for healing. Special types of patches have been devised that allow the eye to remain slightly open or that exert less pressure on the eye, but these are harder to apply.

Recent studies have shown that patching may be of no benefit in many cases, at least with regard to smaller corneal abrasions. The eye can be left unpatched, and antibiotic ointment can be instilled several times a day. The ointment helps prevent infection and also keeps the surface of the eye moist, thereby promoting healing.

Although some ointment ingredients could possibly retard healing a bit, overall the eyes do well in this manner, and they certainly receive more oxygen than they do when they are patched. Nevertheless, in each case, the doctor must use judgment in deciding which technique will work best.

Although anesthetic eyedrops,which numb the surface of the eye, could eliminate the pain caused by a corneal abrasion,they should never be used to treat these. They are to be used only by the doctor to eliminate the severe light sensi-

tivity that interferes with the eye examination. The numbing effect of these drops lasts only a very short time, and their continuing use has a toxic effect on the cornea that can result in a corneal ulcer, an eye-threatening condition.

Why Abrasions Recur

An occasional complication of a corneal abrasion is a recurrent abrasion, sometimes called a recurrent erosion. This occurs more often when a thin sharp object, such as a fingernail or a sheet of paper, abrades the eye. A person with a recurrent abrasion usually experiences sudden pain, watering, and light sensitivity on awakening from sleep. Apparently, the epithelial cells in the area where the

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abrasion occurred sometimes do not heal properly. During sleep, the eye may become slightly dry, and the epithelial cells of the cornea may stick to the closed eyelid. When the lid opens, off come the epithelial cells, and the result is another abrasion. These recurrent abrasions are treated

the same way as the original abrasions were treated, but additional techniques must often be used to keep them from recurring. For

example, lubricating eye ointment can be instilled in the eye at bedtime for a period of time. Sometimes a thin contact lens called a bandage lens is placed on the eye and left in place for at least several weeks. It keeps the inside of the eyelid from coming into contact with the cornea and may allow better healing to take place. Finally, more invasive methods, such as laser treatments or pricking the surface of the cornea in multiple places with a needle, may be necessary.

Treating Corneal Lacerations

When a cut on the cornea goes through the epithelium and into the thick middle layer, the stroma, we call it a laceration. Such a laceration may go only partway through the cornea or through the entire thickness of the cornea. The latter possibility is much more serious, because the fluid (aqueous humor) inside the eye can leak out, and bacteria can get into the eye, resulting in an infection that could cause loss of the eye. When a full-thickness laceration occurs, an X ray of the eye is taken to make sure that no foreign body got into the eye. A tetanus booster shot may be given. The laceration must then be repaired (with microscopic stitches) in the operating room with the patient under general anesthesia. Antibiotics are given to lower the risk of infection. Although such a laceration could result in loss of the eye, the results are often very good, especially if the laceration does not cross the center of the pupil. In contrast, a laceration that goes only partway through the stroma layer of the cornea may not need stitches at all if the laceration is not very deep.

Superficial Foreign Bodies

Although tiny foreign bodies can lodge themselves in either the cornea or the conjunctiva, we most often see them in the cornea. They may become embedded more easily in the cornea, and those in the conjunctiva may cause fewer

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symptoms. Undoubtedly, many foreign bodies become more deeply embedded as the result of eye rubbing after the foreign body contacts the surface of the eye. There is usually a feeling of something in the eye, although sometimes minutes or even hours may elapse before that feeling is present. Although the eye is very sensitive, it is poor at localizing symptoms. Therefore, the person with a foreign body in the cornea will often complain of feeling something under the upper eyelid, often in its outer portion. After a while, watering of the eye, redness, and light sensitivity may occur, and a sharp pain may be present as well.

By far the most common type of corneal foreign body is a tiny piece of steel. It can enter the eye while a person is welding or working under a car, or it may just blow into the eye. When it lodges in the cornea, it immediately starts to rust. Interestingly, even galvanized steel, which is not supposed to rust, generally rusts somewhat. As it rusts, the rust seeps into the cornea, deeper and deeper. When that occurs, removal of the metal alone leaves a so-called rust ring in the cornea. If the rust ring is not removed also, the cornea may not heal properly and may become increasingly inflamed. Therefore, early removal is helpful. Since other types of corneal foreign body do not rust, their removal is generally much easier.

Corneal foreign bodies are removed while we look at the eye through a slit lamp. After the eye is numbed with drops, the foreign body and associated rust can often be removed with the bevel or edge of a needle normally used for injections, such as those used for TB skin tests. Occasionally, a kind of motorized drill with a small burr may be used to remove as much of the rust as possible. Since the cornea numbs easily, the entire process is painless. At the completion of the procedure, antibiotic drops or ointment is instilled in the eye, and the eye may sometimes be patched. Follow-up examinations are usually necessary to make sure that the eye is healing properly and that no infection is setting in.

Although it can be uncomfortable to have a foreign body in the cornea, never use anesthetic (numbing) eyedrops to relieve the discomfort. These drops are toxic to the cornea and increase the risk of developing a corneal ulcer.

Sometimes a tiny foreign body will become embedded on the inside surface of the upper lid. The symptoms may be very similar to those caused by a corneal foreign body. When the ophthalmologist examines the cornea, multiple, fine vertical scratch marks are often seen on the upper cornea. The cornea is being lightly scratched every time the eye blinks. To locate the foreign body, we have to evert the upper lid (turn it over on itself so that the inner surface is

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visible). The foreign body is usually easy to see through the slit lamp and can be removed without difficulty.

Corneal Clouding

The cornea is a marvel of nature. When it is working properly, its crystal-clear structure allows it to be transparent. This transparency is maintained by the cornea’s endothelial cells. These cells form a single layer that lines the inner surface of the cornea, facing the fluid inside the eye. Their function is to pump any water that gets into the cornea back into the interior of the eye. This is a neverending job, because the fluid pressure inside the eye is always trying to force fluid into the cornea. As we get older, we very gradually lose these endothelial cells, which are not replaced. Fortunately, we are born with many more of these cells than we need. However, some people lose so many cells that fluid buildup, called edema, develops in the cornea. A waterlogged cornea becomes thickened and cloudy. Vision can become blurred, and lights appear as though they have halos around them. Edema of the cornea can also cause tiny blisters to form on the outside of the cornea, creating inflammation and discomfort.

Causes of Endothelial Cell Loss and Edema

In some people, the loss of these endothelial cells is a genetically transmitted disorder called Fuchs’s dystrophy. Other problems can also accelerate the loss of endothelial cells. Eye injuries, both mechanical and chemical (acid and base); surgery (including cataract); inflammations and infections in the eye; and high intraocular pressures (see chapter 10) can also cause the endothelial cells to malfunction or die off. People who have Fuchs’s dystrophy have a mild tendency toward higher eye pressures, and this can exacerbate their problem. The effects of eye surgery, especially cataract surgery, represent a large number of the cases of corneal edema that we see today.

Diagnosing Endothelial Cell Problems

The condition of the endothelial cells and the presence of corneal edema are determined during examination of the eye with the slit lamp, also known as the biomicroscope. Careful examination of the back surface of the cornea

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