Dry eye
Dry eye syndrome (DES) is a condition characterized by insufficient moisture and lubrication on the eye surface, primarily due to a reduced flow of tears from the lacrimal glands. Symptoms often include a scratchy sensation, burning, and in advanced stages, inflammation can affect the cornea and eyelids. Various factors contribute to DES, including age-related decreases in tear production, environmental influences like dry winds or smoke, and extended periods of screen use or driving. Additionally, certain medical conditions such as rheumatoid arthritis and Sjögren syndrome, as well as complications following surgeries like LASIK, can exacerbate the condition.
Treatment options for dry eye may range from simple remedies such as artificial tears to more advanced interventions like inserting punctal plugs or cauterizing the lacrimal puncta to slow tear drainage. Preventive measures, such as consuming omega-3 fatty acids found in dark fleshed fish, are also recommended. Increased public awareness has led to a greater understanding of the condition, and advancements in medical science hold promise for more effective treatments, including potential gene therapies for related eye disorders in the future. Overall, DES is both a common and treatable eye condition that warrants attention for those experiencing its symptoms.
Dry eye
Disease/Disorder
Anatomy or System Affected Outer layers of the eye, with possible effects on clear vision through inflammation; nasal lacrimal duct
Definition Dry eye syndrome (DES), or keratoconjuntivitis sicca, affects the outer layers of the eye, which must be continually moistened by the liquid content of the tears. The normal flow of tears may be reduced as a result of the aging process or various external causes, including wearing contact lenses. DES occurs more among women than among men.
Key Terms
blepharospasm: increased blinking to try to compensate for a lack of moisture on the eye surface
conjunctiva: the transparent tissue that covers the surface of the eye and inner sections of the eyelid; this tissue secretes oils and mucous that, helped by the presence of tears, lubricate the eye
corneal epithelium: the transparent covering of the outer surface of the eye that serves mainly to protect the eye; the cornea can be damaged as a result of DES
lacrimal glands: located (as pairs) in recesses in the skull above each eye, these glands release liquid tears; these are then spread across the surface of the eye when the eyelids blink
tear breakup time: the time between initial tear flow onto the eye surface and the first phase of evacuation of moisture via the lacrimal fossi into the lacrimal sac
Causes and Symptoms
If the eye surface does not receive sufficient moisture and lubrication from the normal flow of tears from the lacrimal glands, a first symptom may be a feeling of scratchiness when blinking. This can be accompanied by a burning sensation. In advanced stages of DES, damage may spread, in the form of inflammation, to the cornea and the eyelids.
The essential cause of DES stems in one way or another from a reduced flow of tears from the lacrimal glands. In addition to a natural decrease in lacrimal gland activity as part of the aging process, external factors (some obvious, like extended exposure to dry wind or smoky conditions) can affect the necessary supply of tears to the surface of the eyes. Eye fatigue after long hours of television viewing, computer use, or driving can contribute directly to the onset of DES.
Several eye diseases are directly or indirectly related to keratoconjuntivitis sicca. The most common is blepharitus, a chronic inflammation of the eyelid. It begins with characteristic eyelid redness but, if not treated promptly, develops into more dangerous conditions involving flaking of the skin and crusting at the lid edges. In advanced cases cysts may develop. Inflammation of the cornea is also linked to DES. Chronic conditions that can increase the risk of DES include rheumatoid arthritis, lupus erythematosus, and Sjögren syndrome, an autoimmune disorder in which tear-producing and salivary glands are destroyed. Dry eye is also a common complication of laser-assisted in situ keratomileusis (LASIK) surgery.
In both moderate and more serious cases of DES, the functioning of the lacrimal drainage system (LDS) can be adversely affected. The anatomy of the LDS, which is linked to the mucosa bearing parts of the conjuctiva, consists of two apertures (lacrimal puncti) at the ends of the eyelids. Soon after the lacrimal glands have released tears onto the eye a “tear breaking point” occurs. Excess liquid tears are taken into the lacrimal puncta, passing through narrow canals into the lacrimal sac, from which liquid flows into the nasolacrimal duct into the nose. Any malfunctioning of this transfer process linked to DES—particularly insufficient moisture moving from the eyes into and through the lacrimal puncta—may call for delicate treatments that are specific to DES (see below).
Treatment and Therapy
Many ophthalmologists favor regular consumption of dark fleshed fish (which contains omega-3 fatty acids), as a natural measure for people seeking to prevent DES. When less serious cases begin, eye dropper application of a prepared solution of artificial tears (sold over the counter at most pharmacies) can provide relief. Such solutions contain a mixture of water, salts, and one or more chemicals such as carboxymethyl cellulose, or hydroxpropyl cellulose. The latter additive has a thickening effect on the precorneal tear film, causing tears to remain longer on the surface of the eye before the draining process described above. Artificial tears lack, however, essential proteins (mainly lysozyme) found in natural tears, so they cannot be fully effective.
Several immune response reactions occurring naturally on the ocular surface, including the synthesis and release by the epithelium of cytokines (soluble proteins, peptides, and glycoproteins) and enzymes that serve as catalysts in combination with chemicals in the outer layers of the eye, are the body’s way of providing soothing effects.
When DES symptoms suggest that natural tears are being evacuated too rapidly via the lacrimal puncti, several treatments may be appropriate. These can involve insertion of specially prepared plugs into the puncta (a process which can be adjusted periodically) or actual shrinkage of the puncti apertures by cauterization and permanent scarring of the surrounding tissue.
Perspective and Prospects
Because DES is mentioned widely in the media (especially television) the general public is much more aware now than in the past of symptoms and preventive treatment of symptoms. As for its more serious potential consequences, recent scientific advances have made it possible to correct eye disorders stemming from advanced keratoconjuntivitis sicca. A notable example is the possibility of corneal transplants to replace damaged corneas.
Ongoing research in the field of molecular cloning and gene transfer techniques suggests that, because the surface of the eye is particularly accessible for skilled surgical intervention, serious eye diseases that initially develop from DES conditions may in the future be treatable by transferring highly selective “foreign” genes into target cells in the epithelial tissue.
Bibliography
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Kao, Winston W. “Particle-Mediated Gene Transfer to Ocular Surface Epithelium.” Lacrimal Gland, Tear Film, and Dry Eye Syndromes 3, Part A, edited by David A. Sullivan, et al. New York: Kluwer Academic/Plenum Publishers, 2002.
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