BASICS

DESCRIPTION

• Xerophthalmia (Greek for dry eyes) is a condition of severe dry eye generally referring to the disease caused by vitamin A deficiency (VAD).

• Other conditions can also be associated with dry eyes (keratoconjunctivitis sicca). (See Differential Diagnosis.)

• Ocular signs of xerophthalmia due to VAD include night blindness, conjunctival and corneal xerosis (dryness), Bitot’s spots, keratomalacia, corneal ulceration, corneal scars, and retinal changes.

• VAD is a major public health nutrition problem in the developing world particularly Southern Asia and Africa. It especially affects young children also causing limited growth, weakened immune defenses, and increased risk of death.

EPIDEMIOLOGY

Incidence

Clinical xerophthalmia is extremely rare in the U.S. and other developed countries.

Prevalence

The WHO reported 2.8 million preschool children with clinical xerophthalmia worldwide accounting for 20,000–100,000 new cases of childhood blindness each year.

RISK FACTORS

• VAD particularly when associated with protein deficiency

– Children aged 1–6 years and pregnant women are especially at risk.

– Patients with AIDS may be at greater risk for VAD.

– Vegan and other severe dietary restrictions may also pose a greater risk for deficiency.

GENERAL PREVENTION

• Adequate vitamin A intake, preferably through a balanced diet

• The Food and Nutrition Board at the Institute of Medicine recommends the following:

– Infants 400–500 μg/day

– Children 300–600 μg/day

– Adolescents and adults 700–900 μg/day

– Women who are pregnant or producing breast milk (lactating) need higher amounts.

PATHOPHYSIOLOGY

• Vitamin A is a fat-soluble vitamin ingested in the diet in two forms: as retinol itself from animal sources or as the provitamin carotene from plant sources.

• Adequate body stores of zinc and protein are necessary for the formation of retinol-binding protein (RBP), without which vitamin A cannot be transported to its target tissues.

– In the retina, vitamin A serves as a precursor to the visual pigments of the photoreceptors.

– It is necessary for conjunctival mucosa and corneal stromal integrity.

• VAD leads to atrophic changes in the normal mucosal surface, with loss of goblet cells, and replacement of the normal epithelium.

ETIOLOGY

VAD

COMMONLY ASSOCIATED CONDITIONS

• Protein deficiency

• Malnutrition

• Immune deficiency

DIAGNOSIS

HISTORY

• A history of malnutrition or malabsorption leading to a VAD state

• Night blindness is an early symptom.

• Dry eyes can usually be diagnosed by the symptoms alone: dryness, foreign body sensation, burning, itching, ocular pain, mucus formation, red eye, visual disturbances, and easily fatigued eye.

• The diagnosis of xerophthalmia is mostly clinical, and a high degree of suspicion is required.

PHYSICAL EXAM

• A slit lamp examination should be performed to diagnose dry eyes and to document any damage to the eye.

• A Schirmer’s test can measure the amount of tears bathing the eye. This test is also useful to determine the severity of the condition. A 5-minute Schirmer’s test, using a standard 5 × 35-mm paper strip, with and without anesthesia showing wetting under 5 mm is considered diagnostic for dry eyes (1)[B].

• A tear breakup time (TBUT) test measures the time it takes for tears to break up in the eye. A breakup time of less than 10 seconds is considered abnormal.

• Abnormal staining of the cornea and conjunctiva with fluorescein or rose bengal 1% is also a useful diagnostic test.

DIAGNOSTIC TESTS & INTERPRETATION

Lab

• Serum vitamin A levels of 35 μmol/dL or less (2)

• Total and holo-RBP (complex of vitamin A and RBP) for serum RBP tend to correlate with measures of serum vitamin A (3)[C].

• Conjunctival impression cytology is a technique useful for detecting preclinical xerophthalmia. It is a noninvasive method of obtaining a specimen to assess the histological appearance of the superficial conjunctival layers.

Pathological Findings

Conjunctival biopsy shows epidermidalization with surface keratinization; a reduction of goblet cell density and squamous metaplasia can also be documented with impression cytology.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis includes other conditions that can be associated with dry eyes (keratoconjunctivitis sicca) such as radiation, Sjögren’ s syndrome, systemic lupus erythematosus, rheumatoid arthritis, scleroderma, sarcoidosis, amyloidosis, hypothyroidism, and the use of some medications including antihistamines, nasal decongestants, tranquilizers, and antidepressant.

TREATMENT

MEDICATION

Oral treatment consists of 200,000 IU of vitamin A in oil followed the next day with an additional dose of 200,000 IU (4)[B]. In the presence of severe corneal disease or malabsorption, the preferable dose is 100,000 IU water-miscible vitamin A intramuscularly followed the next day and every 1 to 2 weeks with an oral dose (5)[B].

ADDITIONAL TREATMENT

General Measures

• Supportive treatment of symptoms usually includes use of artificial tears in the form of eye drops, increasing the humidity of the environment with humidifiers, use of goggles, and wearing wraparound glasses when outdoors to minimize the effects of wind.

• Lacrimal drainage punctal plugs can be used to increase the tear lake.

• Prevention and treatment of secondary bacterial infections from ulcers

• Topical retinoic acid (0.1%) can be used to promote healing; however, this can increase scaring so it should be used with caution (6)[B].

Issues for Referral

• Corneal and conjunctival ulcers, bacterial infections, and corneal melting all require immediate care by an ophthalmologist. Retinal changes also may need to be attended to.

• Associated conditions, such as immune deficiency, malnutrition, and malabsorption syndromes may require subspecialty referral.

SURGERY/OTHER PROCEDURES

• Surgery plays a limited role in xerophthalmia. Keratomalacia (corneal melting) is usually inoperable and mostly residual, visually significant scars are amenable to corneal transplants.

• Many patients in developing countries are generally too weak and malnourished to tolerate surgery.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

• Repeated external ophthalmic and funduscopic exams are warranted to document adequate, sustained healing and prevention of relapses.

• In children, sustained healing of severe xerophthalmia requires addressing the underlying protein deficiency.

DIET

• Vitamin A comes from animal sources, such as eggs, meat, milk, cheese, cream, liver, kidney, cod, and halibut fish oil.

• Vegetable sources of beta-carotene are carrots, pumpkin, sweet potatoes, winter squashes, cantaloupe, pink grapefruit, apricots, broccoli, spinach, and most dark green, leafy vegetables. The more intense the color of a fruit or vegetable, the higher the beta-carotene content. Bioavailability of vegetable sources may be less than that of animal sources.

• Strains of genetically modified rice rich in vitamin A have been developed to help decrease deficiencies in developing countries.

PROGNOSIS

• Response to adequate therapy is quick and often dramatic. Night blindness and corneal signs and symptoms resolve very rapidly particularly in less advanced disease.

• In the absence of severe corneal scarring, visual acuity can be expected to recover completely.

COMPLICATIONS

• Permanent corneal scarring with loss of vision and even loss of an eye from perforation and infection can result from advanced or untreated disease.

• If decreased visual acuity is not addressed in young children permanent amblyopia may develop.

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