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Figure 32-5.  Leber’s optic neuropathy, acute. Note hyperemic appearance of disc and opacification of the peripapillary nerve fiber layer. (From Burde RM, Savino PJ, Trobe JD: Clinical Decisions in Neuro-Ophthalmology, ed 3, St. Louis, Mosby, 2004.)

30.An 18-year-old man presents with sudden vision loss in one eye, followed by the other eye within days. He denies pain. He has 20/20 vision in both eyes with decreased color plates and bilateral mild disc swelling with peripapillary telangiectatic microangiopathy (Fig. 32-5). Affected vessels do not leak on fluorescein angiography. What does he have?

Leber’s hereditary optic neuropathy. The patient’s history is typical. The disorder is transmitted by mitochondrial DNA; all female carriers transmit it to their offspring. Ten percent of daughters and 50 to 70% of sons manifest the disease. All daughters are carriers. None of the sons are carriers. Young men present with symptoms at 15 to 30 years of age. No effective treatment is known, but some mutations are more likely to have spontaneous improvement in the future; thus genetic evaluation of the mitochondria is worthwhile. Because patients have a higher incidence of cardiac conduction defects, referral to a cardiologist is indicated.

Bibliography

Burde RM, Savino PJ, Trobe JD: Clinical decisions in neuro-ophthalmology, ed 3, St. Louis, 2002, Mosby. Gerstenblith AT, Rabinowitz MP: The Wills eye manual, ed 6, Philadelphia, Lippincott, 2012, Williams & Wilkins. Kline LB, Foroozan R: Neuro-ophthalmology review manual, ed 7, Thorofare, NJ, 2012, Slack.

1.What are the causes of tearing?

Tearing, also known as epiphora, occurs when there is an increase in the amount of tears produced or when there is a problem with the tear drainage system. We produce too many tears when the cornea is irritated. This tearing is adaptive, because if there is a foreign body present, it will wash it away. Acute corneal irritation typically results from mechanical irritants, such as an eyelash, or

chemical irritants, such as the fumes from a freshly cut onion. Chronic tearing from irritation may also result from mechanical irritation as in entropion and trichiasis. However, it often occurs as a result of tear-film deficiencies (seen in dry eye syndrome and blepharitis), exposure keratopathy, or allergic conjunctivitis. When the production of tears is normal, tearing indicates an inadequate drainage of tears. A blockage at any point in the tear drainage system can cause tearing. Eyelid malpositions, such as ectropions and punctal ectropions, will also reduce the drainage of tears, as will lower eyelid laxity, which interferes with the eyelid’s ability to pump the tears naturally through the lacrimal drainage system. For many patients, tearing is multifactorial.

KEY POINTS: COMMON CAUSES OF CHRONIC TEARING

1.Ocular irritation

a.Dry eyes

b.Allergies

c.Computer vision syndrome

2. Tear-drainage dysfunction, such as from lower eyelid laxity

3. Blockage of the lacrimal drainage system, such as from a nasolacrimal duct obstruction

2.Describe the normal path of tear drainage in the eyelids

The most important function of our tears is to lubricate the surface of the eye. Our tears travel across the cornea and conjunctiva, keeping them moist. Gravity then guides most tears to rest on the margin of the lower eyelid. Here, they are carried medially to the puncta, small openings in the eyelid located approximately 6 to 7 mm lateral to the medial canthal angle. Once inside the puncta, the tears enter the canaliculi, mucosa-lined ducts approximately 10 mm in length that carry the tears to the lacrimal sac. The first portion of each canaliculus is a 2-mm dilated, vertical segment called the ampulla. Distal to the ampulla, the canaliculus bends acutely and runs parallel to the eyelid margin toward the medial canthus. In 90% of the population, the upper and lower canaliculi join together, forming the common canaliculus before merging with the lacrimal sac. However, in 10% of the population, each canaliculus merges with the lacrimal sac independently.

3.Where do tears go after leaving the eyelids?

The tears exit the canaliculi and enter the lacrimal sac, a mucosa-lined structure lying in a bony fossa in the medial orbit formed by the maxillary and lacrimal bones. The superior portion of the sac extends a few millimeters superior to the medial canthal tendon. It extends inferiorly approximately 10 mm and then continues as the nasolacrimal duct.

Tears travel from the sac to the nasolacrimal duct. The first 12 mm of the duct lies in a bony canal in the maxillary bone. The duct then continues inferiorly for an additional 3 to 5 mm before opening into the inferior meatus of the nose. The tears exit the duct through its ostium into the nasal cavity.

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The ostium of the nasolacrimal duct can be found 30 mm posterior to the external nares in an adult. In young children, this distance is approximately 20 mm.

4.What is the tear pump?

The tear pump is a muscular “pump” that drives the tears through the drainage system by peristalsis. Tears first enter the puncta by capillary action. During a blink, the orbicularis oculi muscle contracts, closing the puncta, shortening the canaliculi, and moving them medially, while dilating the lacrimal sac. As the sac dilates, it creates a vacuum, drawing in the tears from the canaliculi. When the orbicularis muscle relaxes, the lacrimal sac collapses, the canaliculi lengthen, and the puncta reopen. The valve of Rosenmüller sits between the canaliculi and the sac, preventing the tears from reentering the canaliculi. Thus, tears are forced to continue their course down the nasolacrimal duct into the nose.

5.How does lower eyelid laxity affect tear drainage?

Normal drainage of tears requires normal structure and function of the eyelids. The pretarsal orbicularis muscle surrounds the canaliculi and attaches to the wall of the lacrimal sac. Contraction and relaxation of this muscle help draw the tears into the canaliculus and the sac and eventually force the tears down the nasolacrimal duct. When lower eyelid laxity is present, contraction of the orbicularis muscle does not compresses the canaliculi or force open the lacrimal sac, and the lacrimal pump mechanism cannot function adequately.

6.How can you tell if a patient has lower eyelid laxity?

Stretching of the medial and/or lateral canthal tendon causes lower eyelid laxity. In the distraction test, if the lower eyelid can be pulled more than 6 mm from the globe, it is lax.

Poor orbicularis oculi tone, most obvious in patients with seventh cranial nerve palsy, also causes laxity of the lower eyelid. This is best demonstrated with the “snap-back” test, in which the lower eyelid is pulled down inferiorly and allowed to snap back into place. If the eyelid returns to its correct position immediately, the muscle tone is good. If the patient must blink to place the eyelid back in its normal position, eyelid tone is poor.

7.How do you correct lower eyelid laxity?

If there is laxity of the lateral canthal tendon, a horizontal lid shortening procedure is performed to tighten the eyelid. This is typically accomplished with a lateral tarsal strip procedure. In this operation the inferior limb of the lateral canthal tendon is disinserted from the periosteum of the lateral orbital rim, a portion or the entire tendon is removed, and a new lateral canthal tendon is created from the lateral portion of the tarsus. The newly formed lateral canthal tendon is sutured back to the periosteum of the lateral orbital rim. This effectively shortens the lower eyelid, making the eyelid margin more stable and improving tear pump function.

8.Why do patients with dry eyes complain of tearing?

Patients tear when they have dry eyes for the same reason that they tear when cutting an onion. Onion fumes cause corneal irritation, which, in turn, causes reflex tearing.

Likewise, abnormalities in the tear film coating the cornea and conjunctiva cause irritation. Tearfilm abnormalities can be caused by a decrease in the overall production of tears or by an imbalance in the composition of the tears. Inadequacies in any of the components of the tears cause a tear-film deficiency that can result in tearing.

9.What is computer vision syndrome?

Computer vision syndrome refers to a group of symptoms including tearing, eyestrain, and pain experienced by computer users. According to the National Institute of Occupational Safety and Health, computer vision syndrome affects some 90% of the people who spend three hours or more a day at a computer. Many of the symptoms relate to corneal exposure and the resultant dryness that occurs when extended time is spent staring at a computer screen.

10.Of what are tears composed?

Tears are composed of three layers. Mucin, made by the conjunctival goblet cells found mainly in the conjunctival fornices, covers the epithelium, ensuring a smooth, uniform tear film. The middle aqueous layer, made by the main lacrimal gland and accessory glands of Krause and Wolfring, provides hydration, oxygen, and nutrients. On the surface is the lipid layer, made in the meibomian, Zeis, and Moll glands of the eyelids. It prevents rapid evaporation of the tears and provides a smooth surface for the eyelids to glide across the cornea with each blink.

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11.How can you determine if a patient produces enough tears?

The volume of tears can be indirectly assessed by visualization of the tear meniscus, the tear layer resting on the lower eyelid adjacent to the globe, which should be approximately 1 mm in height. However, the tear meniscus is also affected by tear drainage. The Schirmer test directly tests production. Gently dry the palpebral conjunctiva with a cotton swab and then place the small, folded end of a 5-mm-wide strip of Whatman No. 41 filter paper into the inferior conjunctival fornix at the junction of the middle and lateral third of the lower eyelid. In 5 minutes, measure the amount of wetting of the filter paper. When performed on an anesthetized cornea, it measures basal tear secretion. A normal result is 10 mm or greater. When performed on a nonanesthetized cornea, it measures both basal and reflex tearing. In this instance, normal wetting is 15 mm or greater.

12.How do you know if the tear composition is inadequate?

A decrease in the tear break-up time or the presence of protein, mucus, or debris in the tears indicates a tear inadequacy. The tear break-up time is the time it takes after a blink to develop a dry spot on the cornea. It is measured by touching the palpebral conjunctiva with a moistened fluorescein strip and observing the tear film through the slit lamp with a cobalt-blue filter. It is important to avoid using other eyedrops mixed with fluorescein, because this will change the composition of the tear film you observe. Once the patient blinks, the time is measured until the tear film begins to break up on the cornea, forming a dry spot. Less than 10 seconds is considered abnormal.

13.What are ectropion and entropion? How do they cause tearing?

Ectropion is an outward rotation of the eyelid margin. Entropion is an inward rotation of the eyelid margin. When either is present, patients tear. This occurs because both can cause corneal irritation with its associated reflex tearing, and both displace the punctum, so tears do not enter the teardrainage system.

KEY POINTS: TESTING PATIENTS WITH CHRONIC TEARING

1. Tear quantity and quality evaluation

2. Evaluation of eyelid position

3. Evaluation of eyelid laxity

4. Probing and irrigation of lacrimal drainage system

14.What causes obstructions of the punctum, canaliculus, or lacrimal sac?

Complete and partial obstructions can occur anywhere in the lacrimal drainage system and may be caused by congenital agenesis, inflammation, infection, autoimmune disease, trauma, malignancy, radiation, and the toxic effects of medication. Here are the more common causes by location:

•Punctal obstructions are most commonly seen in congenital agenesis, herpetic infections, iatrogenic closure in the treatment of dry eyes, and mechanical obstruction in the setting of conjunctivochalasis.

•Canalicular obstructions can occur in one or both canaliculi or in the common canaliculus. These are often acquired from trauma, cicatrizing mucosal diseases such as Stevens-Johnson syndrome and ocular cicatricial pemphigoid, herpetic infections, canaliculitis associated with Actinomyces israelii, chemotherapeutic agents such as 5-fluorouracil and docetaxel, or long-term use of topical medications such as pilocarpine, epinephrine, phospholine iodide, and idoxuridine. Foreign bodies, such as silicone punctal and canalicular plugs, can occlude the canaliculi.

•Lacrimal sac obstructions occur most frequently from scarring as a result of a prior infection. Dacryoliths may develop from infections or chronic use of topical medications. Lacrimal sac tumors are rare.

15.What causes nasolacrimal duct obstructions?

Congenital nasolacrimal duct obstructions are found in 6% of normal newborns, and approximately 90% resolve spontaneously in the first year of life. In adults, primary acquired nasolacrimal duct obstruction is the most common cause of these obstructions. The cause of these is not well understood. However, it is commonly believed that obstruction of the ostium of the duct most likely is caused by inflammation of the lining of the duct and nasal mucosa. Dacryocystitis commonly causes

scarring, which leads to nasolacrimal duct obstructions. Abnormalities in adjacent structures are often associated with these obstructions, such as nasal polyps, sinus disease, trauma, and deviated septa.

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16.How do you evaluate the lacrimal system for obstructions?

Obstructions can occur anywhere in the lacrimal system. Punctal obstructions can be visualized on examination. To determine the presence of an obstruction in the canaliculus, lacrimal sac, and nasolacrimal duct, a dye-disappearance test or a Jones dye test can be performed.

Obstruction in the canaliculus can also be determined directly by probing the canaliculus and feeling for partial and complete obstructions. Irrigation of the system will uncover obstructions in the lacrimal sac and nasolacrimal duct.

Imaging techniques of the lacrimal system, including ultrasound, computed tomographic scans, contrast dacryocystography, and radionuclide dacryoscintigraphy, are rarely necessary.

17.What is a dye-disappearance test?

In the dye-disappearance test, a drop of fluorescein is placed in the inferior conjunctival fornix. After 5 minutes, the amount present in the tear lake is assessed using a cobalt-blue light. The presence of little or no fluorescein indicates a normal functioning system. If most of the fluorescein remains, the system is not functioning properly.

18.What is a primary Jones dye test?

A primary Jones dye test involves placing fluorescein in the inferior conjunctival fornix. A cotton swab is placed under the inferior turbinate at 2 and 5 minutes. If dye is recovered on the swab, the system is patent and functioning well. If no dye is recovered, this indicates a poorly functioning system.

19.What is a secondary Jones dye test?

A secondary Jones dye test is performed when no dye is recovered during the primary test. In a secondary Jones dye test, the inferior fornix is first irrigated to remove all residual fluorescein from the primary test. Clear saline is then irrigated through the canaliculus with a cannula. If fluoresceinstained fluid is recovered from the nose, the fluorescein must have passed freely through the punctum and canaliculus and to the lacrimal sac during the primary Jones test, indicating a partial blockage

of the nasolacrimal duct. If clear fluid is recovered, a partial obstruction or functional disorder of the punctum or canaliculus is indicated. If no fluid is recovered from the nose but instead regurgitates from the adjacent punctum, an obstruction at or distal to the common canaliculus is present.

20.How do you treat obstructions of the eyelid portion of the lacrimal system?

When the punctum is not patent, this can frequently be opened with a sharp probe or cut-down procedure to find the proximal canaliculus. In most patients, placement of a temporary silicone stent is helpful to prevent the punctum from reclosing. This office-based procedure is performed with local infiltrative anesthesia. If the canaliculus is stenotic but not completely occluded, dilation with silicone intubation is typically performed. If the canaliculus is completely occluded, a canaliculodacryocystorhinostomy (CDCR) is performed. In this surgery, a fistula is created between the caruncle and the nasal mucosa and a permanent glass tube (Jones tube) is placed in this tract to maintain its patency. A CDCR can be performed on an outpatient basis under general anesthesia or with monitored sedation.

21.How do you treat obstructions of the nasolacrimal duct?

The majority of lacrimal system obstructions occur in the nasolacrimal duct, which connects the lacrimal sac to the nose. When a nasolacrimal duct obstruction is present, a dacryocystorhinostomy (DCR) is performed. In this procedure, the lacrimal sac is marsupialized to the nasal passages, so the tears can bypass the blocked nasolacrimal duct and drain directly from the lacrimal sac into the nose.

22.Describe acute dacryocystitis.

An acute infection of the lacrimal sac is called dacryocystitis. Patients typically present with a painful, erythematous swelling in the medial canthus just inferior to the medial canthal tendon. A purulent discharge from the punctum can often be seen with gentle pressure on the lacrimal sac. Acute dacryocystitis is nearly always the result of a blocked nasolacrimal duct.

23.What is the appropriate treatment for acute dacryocystitis?

Dacryocystitis is a serious infection that must be treated as an emergency. If not adequately treated, an orbital cellulitis may develop. There is also the potential for the infection to spread intracranially. Appropriate systemic antibiotics should be given, and warm compresses should be applied to the medial canthus. Patients should be watched carefully to assure improvement. After resolution of the acute infection, unless the nasolacrimal duct is patent, a DCR should be performed to avoid recurrent infections.