dry%20eye%20syndrome
DRY EYE SYNDROME

Dry eye syndrome is a clinical condition wherein the patient experiences ocular and conjunctival irritation due to decreased tear production and/or excessive tear evaporation.
It is associated with increased osmolarity of the tear film and inflammation of the ocular surface.

Goal of treatments are to relieve symptoms of patients, to improve visual acuity & quality of life of patients, to restore ocular surface & tear film to normal homeostatic state and to correct the underlying defect.

Diagnosis

  • Etiopathogenic classifications:
    • Aqueous tear-deficient dry eye, also known as tear-deficient dry eye or lacrimal tear deficiency
      • Secondary to failure of lacrimal tear secretion
      • Subdivided into Sjogren syndrome, which is an autoimmune disorder, or non-Sjogren syndrome, which may be secondary to lacrimal gland insufficiency, lacrimal duct obstruction, or reflex hyposecretion
  • Evaporative dry eye has normal lacrimal secretory function but causes excessive loss of water from the exposed ocular surface
    • May be secondary to intrinsic factors (eg meibomian gland dysfunction, eyelid aperture disorder or lid/globe incongruity, blink disorders) or extrinsic factors (eg ocular surface disease, contact lens wear, vitamin A deficiency, topical drug preservatives)
  • Results in symptoms that may potentially damage the ocular surface
    • Hyperosmolar tear activates release of inflammatory mediators into the tears which may eventually result in decreased sensation of the cornea, decreased reflex activity, loss of goblet cells, & reduced production of mucin
    • Patients w/ moderate to severe dry eye syndrome (DES) may have reversible squamous metaplasia & punctate erosions of the ocular surface epithelium
      • Severe DES may rarely cause ocular surface keratinization, microbial keratitis, corneal neovascularization, ulceration, perforation, scarring, or severe vision loss

Classification of Dry Eye Syndrome (DES)

  • Based on combination of symptoms & signs
  • Indefinite classification due to overlapping characteristics at each level
  • Mild DES has symptoms of irritation, itching, soreness, burning, or intermittent blurring of vision
    • Complicated to diagnose due to inconsistent symptoms & signs, & relatively low specificity & /or sensitivity of clinical tests
  • Moderate DES has increased discomfort & frequency of symptoms, & more consistent visual dysfunction
  • Severe DES has increased to constant frequency of symptoms & visual dysfunction

History

  • Important to inquire about the following which may predispose or contribute to dry eye syndrome (DES):
    • Duration of symptoms
    • Use of medications (eg artificial tears, eyewash, ophthalmic or oral antihistamines, glaucoma medications, ophthalmic vasoconstrictors, diuretics, hormones, antidepressants, cardiac antiarrhythmic drugs, isotretinoin, beta-adrenergic antagonists, chemotherapeutic drugs, or any drug w/ anticholinergic effects)
      • >4-6x/day use of preserved eye drops may contribute to DES
      • A study found that angiotensin-converting enzyme inhibitors are associated w/ lower risk for DES
    • Ocular history including contact lens wear & care, allergic conjunctivitis, ocular surface disease (eg herpes simplex or varicella zoster virus infection, Stevens-Johnson syndrome, aniridia, ocular mucous membrane pemphigoid)
    • Systemic history such as smoking or exposure to 2nd-hand smoke, dermatological diseases, frequency of facial washing, atopy, menopause, systemic inflammatory diseases (eg Sjogren syndrome, graft vs host disease, rheumatoid arthritis, systemic lupus erythematosus, scleroderma), trauma, chronic viral infections (eg hepatitis C, human immunodeficiency virus), radiation of the orbit, or neurological disorders (eg Parkinson’s disease, Bell’s palsy, trigeminal neuralgia)
    • Ocular surgical history (eg keratoplasty, cataract surgery, keratorefractive surgery) or nonocular surgery (eg bone marrow transplant, head & neck surgery, trigeminal neuralgia surgery)
      • Refractive surgery disrupts corneal innervation & may contribute to aqueous deficiency
    • Occupations like those that require sustained visual attention (eg working at a microscope or computer) or those performed w/ upward or horizontal gaze (eg computer use)
      • May result in decreased blink rate & increased evaporation
      • Upgaze widens the palpebral aperture that exposes the ocular surface more to evaporation
    • Nutritional factors such as low intake of vitamin A or omega-3 fatty acid, or diet w/ high ratio of omega-6 to omega-3 fatty acids which may predispose to DES

Physical Examination

  • Includes measurement of visual acuity, external examination, & slit-lamp biomicroscopy to record the signs of dry eye, to evaluate the severity of decreased aqueous tear production &/or increased evaporative loss, & to identify possible causes of eye irritation
    • Inspect the skin for possible signs of scleroderma or rosacea; eyelids for abnormal secretions, entropion or ectropion, incomplete closure, infrequent blink, eye lid lag or retraction, proptosis, adnexa for enlargement of lacrimal glands; or hands for possible signs of rheumatoid arthritis, Raynaud phenomenon & splinter hemorrhages underneath the nails
    • Assess function of cranial nerves V (trigeminal) & VII (facial)
    • Slit-lamp biomicroscopy should examine the tear film, eyelashes, anterior & posterior eyelid margins, puncta, conjunctiva, & cornea

Laboratory Tests

  • Useful in confirming the diagnosis but often poorly correlate w/ symptoms
  • Evaluate the tear film instability, ocular surface damage, & aqueous tear flow
  • Tear film break-up time (TFBUT) test is the time that lapsed between the last blink & the appearance of the 1st break in the fluorescein-stained tear film
    • Used to evaluate the tear film stability
    • Localized anterior basement-membrane abnormality may be considered if tear break-up in the same area is recurrent
    • Abnormal result is considered when TFBUT is <10 seconds which may be seen in both aqueous tear deficiency & meibomian gland disease
  • Ocular surface dye staining uses fluorescein, rose bengal, or lissamine green dyes
    • Evaluates the ocular surface
    • Fluorescein dye stains area of the corneal & conjunctival epithelia w/ disruption of intercellular junctions that are adequate to allow the dye to penetrate into the tissue
      • Mild staining may be seen in normal eyes especially in the morning
      • Blotchy or exposure-zone punctate staining is consistent w/ dry eye syndrome (DES)
    • Rose bengal stains the ocular surface cells that are deficient in mucous coating & debris in the tear film
    • Lissamine green stains similar to that of rose bengal dye but is well tolerated as fluorescein dye
      • Not to be used in evaluating corneal epithelial disease
    • Viral keratoconjunctivitis & medicamentosa shows diffuse staining of the cornea & conjunctiva
    • Staphylococcal blepharitis, meibomian gland dysfunction, or lagophthalmos shows staining on the inferior cornea & bulbar conjunctiva
    • Superior limbic keratoconjunctivitis presents w/ staining on the superior bulbar conjunctiva
    • Aqueous tear deficiency is usually observed to have staining on the interpalpebral cornea & bulbar conjunctiva
  • Schirmer test is used to assess aqueous tear production or flow
    • May be done w/ or w/o anesthesia to measure reflex tearing or w/ anesthesia to measure basal tearing by minimizing ocular surface reflex activity
    • Schirmer test w/ anesthesia is considered abnormal if the result is ≤10 mm
    • Usually has variable results, hence, should not be used as the only criterion to diagnose DES
      • Isolated abnormal result may be nonspecific but consistent low result highly suggests aqueous tear deficiency
  • Fluorescein clearance test or tear function index are used to assess clearance or turnover of tears on the ocular surface
    • Evaluates aqueous tear production, tear volume, & tear drainage
    • More correlated w/ the severity of ocular irritation symptoms & corneal fluorescein staining than the Schirmer test
    • Delayed clearance is associated w/ high tear cytokine concentration which may contribute to chronic inflammation
  • Lacrimal gland function test
    • Measures lactoferrin, the most numerous tear protein being secreted by the lacrimal gland
    • Low lactoferrin concentration is noted in patients w/ Sjogren syndrome & other causes of lacrimal gland dysfunction
  • Tear osmolarity test has been shown to be more sensitive in diagnosing & grading the severity of DES as compared to corneal & conjunctival staining, TFBUT, Schirmer test, & meibomian gland grading
  • Other tests:
    • Videokeratography may be used to objectively diagnose & evaluate the severity of DES, screen patients prior to laser-assisted in situ keratomileusis (LASIK) & identify their post-LASIK chronic DES risk
    • Impression cytology is a less invasive alternative to ocular biopsy that is used to determine abnormalities like goblet cell loss & squamous metaplasia
  • Specific tests in patients w/ underlying conditions:
    • SSA, SSB, ANA, RF for Sjögren syndrome
    • Anti-thyroid peroxidase antibody, antithyroglobulin antibody, B-scan sonogram to assess extraocular muscle thickness for thyroid eye disease
    • Serum lysozyme, angiotensin-converting-enzyme inhibitor (ACE), chest computed tomography (CT) scan to determine the extent of disease, conjunctival biopsy for sarcoidosis
    • Conjunctival biopsy w/ light microscopy, immunofluorescent or immunohistochemical studies for cicatricial pemphigoid

Screening

Questionnaires

  • Eg Ocular Surface Disease Index (OSDI), McMonnies Dry Eye Questionnaire, Canadian Dry Eye Epidemiology Study (CANDEES) Questionnaire, Dry Eye Epidemiology Projects (DEEP) Questionnaire, Women’s Health Study Questionnaire, NEI-Visual Function Questionnaire (NEI-VFQ), Dry Eye Questionnaire (DEQ) & Contact Lens Dry Eye Questionnaire (CLDEQ), Dry Eye Disease Impact Questionnaire (DEDIQ), Ocular Comfort Index (OCI)
  • Used to evaluate the effects of treatments or to grade the severity of the disease, screen individuals for clinical research, or to study the natural history of disease for epidemiologic research
  • Usually contains clinician-based or other diagnosis of dry eye, frequency or intensity of symptoms, effect of symptoms on daily activities, effect of environmental triggers on symptoms, effect of treatment on symptoms, etc
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