- 1.
What is the definition of dry eye?
A dry eye, or keratoconjunctivitis sicca, is a condition in which the tear film is abnormal and cannot lubricate the anterior surface of the cornea adequately. The resulting changes in the ocular surface can cause ocular discomfort, scarring, and, in severe cases, loss of vision and perforation.
- 2.
Describe the normal tear film
The normal tear film is a 1.0-mm convex band with a regular upper margin.
- 3.
What are the components of the tear film?
The normal tear film is made of three components. The outer layer is a thin lipid layer produced by the meibomian glands, which open along the upper and lower lid margins. The middle layer, the thickest, is composed of aqueous produced from the main and accessory lacrimal glands. The innermost layer is a mucin layer produced by conjunctival goblet cells.
- 4.
What is the function of the outer lipid layer?
It retards evaporation of the aqueous middle layer. If it is dysfunctional, evaporative dry eye will result.
- 5.
What causes dysfunction of the outer lipid layer?
It could be caused by oil deficiency, as in meibomian gland dysfunction (i.e., blepharitis). Also, an abnormal lid contour, as in ectropion or lid tumor, or poor blinking, found in Bell’s palsy, can cause outer lipid layer dysfunction.
- 6.
What is the function of the aqueous middle layer?
It supplies oxygen from the atmosphere to the corneal epithelium, washes away debris, and has antibacterial properties due to IgA, lysozyme, and lactoferrin present within it. If deficient, hyposecretive dry eye results, as found in Sjögren’s syndrome.
- 7.
What is the function of the inner mucin layer?
It covers the villus surface of the corneal epithelium, converting it from a hydrophobic surface to a hydrophilic one, thus allowing the aqueous layer to lubricate the cornea.
- 8.
What diseases of the conjunctiva can cause dry eye?
Conjunctival scarring can injure the goblet cells. Patients with cicatricial ocular pemphigoid, Stevens-Johnson syndrome, chemical burns (especially alkali), and graft-versus-host disease in bone marrow transplantation may have dry eye. Patients with other conjunctival disorders that accompany conditions such as aniridia may also have dry eyes. Vitamin A deficiency can result in the loss of goblet cells. This is becoming more common with the increase in gastric bypass procedures.
- 9.
What is necessary for the normal resurfacing of the tear film?
A normal blink reflex, normal lid anatomy and contour, and a normal corneal epithelium. Of course, a normal tear film makeup is essential.
- 10.
What are the types of dry eye?
Basically, there are three main types:
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Hyposecretive (i.e., Sjögren or non-Sjögren syndrome): The aqueous component is low. Ten percent of severe dry eye patients have Sjögren syndrome. Lacrimal deficiency or obstruction and systemic drugs are other causes.
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Evaporative
- 1.
Extrinsic causes are vitamin A deficiency, topical drugs and their preservatives, contact lens wear, and environmental factors such as low humidity or allergens.
- 2.
Intrinsic factors are meibomian gland dysfunction, eyelid abnormalities (i.e., Bell’s palsy, ectropion) or corneal surface changes such as dellen, and poor blink.
- 1.
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Mixed: This combines features of the other two.
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- 11.
What are the symptoms of dry eye?
Burning, irritation, foreign body sensation, light sensitivity, and blurred vision. Usually, the symptoms are worse in the afternoon and evening and better on awakening. A dry or dusty environment may cause more difficulties in patients with dry eye than in others. Cigarette smoke can be extremely irritating. Symptoms are worse in low-humidity environments, such as those with central air and in an airplane, during prolonged reading or driving with a decreased blink rate owing to increased concentration, and windy conditions.
- 12.
What are the most common signs of dry eye?
In the early stages, ocular symptoms may be more impressive than what is found on the examination. Signs of dry eye include a decreased tear meniscus, debris in the tear film, conjunctival injection, and superficial punctate keratitis and conjunctivitis. Abnormal fluorescein or rose bengal staining of the corneal and conjunctival epithelium in the exposed interpalpebral fissure (at 3 and 9 o’clock) of the lower third of the cornea is often present. The upper half of the cornea is usually spared. In more severe disease, filamentary keratitis can develop as well as corneal scarring. Blepharitis with a frothy tear film may be seen in tandem with dry eye.
- 13.
What is Sjögren’s syndrome?
Sjögren’s syndrome is a triad of dry eye, dry mouth (xerostomia), and a collagen vascular disease. Rheumatoid arthritis is the most common, but systemic lupus erythematosus, Wegener’s granulomatosis, scleroderma, systemic sclerosis, and primary biliary cirrhosis may also be associated. The lacrimal gland acini and ducts are damaged in the autoimmune disease. Ten percent of severe dry eye patients have Sjögren’s syndrome.
- 14.
How do you determine if a patient has Sjögren’s syndrome?
Order anti-Sjögren syndrome A antibody (SSA or anti-Ro), anti-Sjögren syndrome B antibody (SSB or anti-La), rheumatoid factor, and antinuclear antibody. A biopsy of the lacrimal gland may be necessary. Then, refer to a rheumatologist.
- 15.
Who gets dry eye?
Women are more likely to develop this than men, probably in relation to changes in hormone levels. It is also associated with birth control use. Contact lens wearers frequently have problems with dry eye, especially with long histories of contact lens use.
It may be seen in all age groups, but it is most common after 60 years of age. It can occur in patients in their 20s and 30s, but may be overlooked unless patients are specifically questioned about symptoms. LASIK and blepharoplasty can exacerbate underlying dry eye. Radiation treatments can also cause dry eye. Many systemic medications have a side effect of dry eye.
- 16.
What medications may be a cause of dry eye?
Topical eye drops such as those used in glaucoma can cause or worsen dry eye. The medication or the preservative may cause toxicity to the epithelial cells. Aminoglycoside antibiotics (i.e., Neosporin and gentamicin), β-blockers, and pilocarpine are common offenders.
Systemic medications that can decrease tear production include antimuscarinics (scopolamine, Detrol), antihistamines, lithium, diuretics, estrogens (including birth control pills), antihypertensives (β-blockers, α-agonists), antidepressants, chemotherapy agents, antipsychotics, marijuana, and morphine.
- 17.
What stains are used in dry eye diagnosis?
Fluorescein stains corneal and conjunctival epithelial defects. Rose bengal stains mucin and epithelial cells that are dead or devitalized, but still in place, as well as breaks in the tear film on the cornea or conjunctiva. Thus, rose bengal will show earlier, more subtle abnormalities in comparison to fluorescein. Lissamine green stains damaged or devitalized cells, but does not stain healthy cells in contrast to the other two dyes.
- 18.
How do you measure a tear breakup time (TBUT)?
Instill fluorescein into the lower fornix. Ask the patient to blink several times and then stop. The TBUT is the time from the last blink to the development of a dry spot noted by black spots in the fluorescein film. Normal is 10 or more seconds. It decreases with age, but less than 5 seconds is good evidence for dry eye. Meibomian gland dysfunction may show a TBUT of zero.
- 19.
What is Schirmer’s test?
A Schirmer’s test filter strip is placed with the notched edge over the lid margin. The tear film in the lacrimal lake is absorbed over 5 minutes and measured. A normal Schirmer’s test wets the strip 10 mm. Usually, it is done with topical anesthesia so as to not cause reflex tearing.
- 20.
What other tests are done in dry eye patients?
Tear film osmolarity is elevated in patients with dry eye disease as well as other disease states such as bacterial conjunctivitis and meibomitis. Tear lactoferrin levels are low in dry eye disease. MMP-9 is a marker of inflammation and elevated in tears in dry eye disease. Quick and simple in-office tests are available for all of these. Tear meniscus height can be measured with optical coherence tomography. It remains to be seen if the community at large will adopt any of these. They all give evidence to make a diagnosis of dry eye disease as well as objective markers to observe treatment effectiveness or failure.
- 21.
What are the treatments for dry eye patients?
The Management and Therapy Subcommittee of the International Dry Eye Workshop has recommended that treatments be based on disease severity. Dry eye severity is graded from 1 to 4 (see Table 11-1 ). Even if a patient has a normal exam, but describes typical dry eye (level 1), treatment should be instituted. Begin with environmental modifications, stopping any topical and/or systemic medications that might be worsening the symptoms, warm compresses, and blepharitis treatment. Start tear replacement therapy. They are used as needed depending on the patient’s symptoms. Once or twice a day may be fine for some; others may need nearly every hour. Lacrisert is a solid form of artificial tear placed in the lower cul-de-sac that melts over a period of 12 hours. It is seldom used but can be very effective in a small number of patients. Lubricating ointments can be used at night. It will blur vision, but may be necessary during the day if exposure is a significant problem, as in Bell’s palsy.
