Dry eye: Challenges in diagnosis and treatment

November 9, 2008

Recent reports from expert panels emphasize the complexity of dry eye disease, reflecting advances in understanding of this disease in the past decade. Along with this new grasp of the condition's complexity, diagnostic and treatment approaches must evolve as well. New tools and methods for diagnosis and treatment have been developed and have entered clinical practice, while others are in the pipeline or still primarily used in research settings.

Recent reports from expert panels emphasize the complexity of dryeye disease, reflecting advances in understanding of this diseasein the past decade. Along with this new grasp of the condition'scomplexity, diagnostic and treatment approaches must evolve aswell. New tools and methods for diagnosis and treatment have beendeveloped and have entered clinical practice, while others are inthe pipeline or still primarily used in research settings.

Speakers at a continuing education symposium provided updates onthese developments in a breakfast meeting held at the AtlantaMarriott Marquis during the American Academy of Ophthalmologyannual meeting.

The 2007 report of the International Dry Eye Workshop (DEWS)provides an encyclopedic, evidence-based review of the presentstate of knowledge about dry eye disease. The result of 3years of collaboration by an international panel, the reportsummarizes current knowledge on the epidemiology, diagnosis, andmanagement of dry eye disease as well as clinical trials andfoundations for future research.

The report's definition of dry eye disease emphasizes that it ismultifactorial, involving the tears and ocular surface, and isaccompanied by increased osmolarity of the tear film andinflammation of the ocular surface. The global features of dryeye include tear film instability, ocular surface disease,chronic pain or irritation, and visual degradation, said PennyAsbell, MD, MBA, professor of ophthalmology, Mount Sinai Schoolof Medicine, New York. Dr. Asbell is also director of Cornea andExternal Diseases and Refractive Surgery.

The DEWS report also includes a dry eye severity grading schemethat outlines four disease stages. The grading is based ondiscomfort, severity, and frequency; visual symptoms;conjunctival injection; conjunctival staining; corneal staining(severity and location); cornea and tear signs; lid and meibomianglands; fluorescein tear breakup time; and Schirmer score. Thisgrading scheme should be a useful aid for clinicians, Dr. Asbellsaid.

She also explained that while a number of tests can be performedto diagnose dry eye, they all have limitations. Current methodsare often neither sensitive nor reproducible, she said, addingthat it is also difficult to accurately diagnose and determineend points for clinical trials. It is also difficult to evaluateusefulness of different medications in the treatment of dry eyedisease.

The ideal test would be minimally invasive and objective, Dr.Asbell said, adding that new approaches, such as cornealpermeability, could be more definitive.

Gary N. Foulks, MD, concurred that caveats must be observed withdiagnostic testing. One test may not be sufficient to diagnose,he explained, and the technique determines the accuracy. He addedthat results of testing must be compared with those of the normalpopulation. Dr. Foulks is Keeney Professor of Ophthalmology,University of Louisville, KY.

Signs and symptoms may sometimes be misleading, but patientcomplaints of visual disturbance and discomfort are oftenreliable indicators of dry eye, Dr. Foulks said.

Dr. Foulks also noted that tools used in dry eye research arebeginning to reach the clinic. These include functional visualacuity, osmolarity testing, conjunctival impression cytology, andmeasures of inflammation mediators in tear film and on the ocularsurface. While not yet available for clinical use, markers ofinflammation could be one of the most valuable in diagnosing dryeye. Testing of functional visual acuity, a technique developedin Japan, also has high potential in the office setting.

Numerous tools are applicable for evaluating ocular surface changes. Staining can be performed with fluorescein, rose bengal, and lissamine green, while conjunctival impression cytology can be used for goblet cell counts, epithelial cell histology, and antigen expression. Inflammation mediators can be measured through tear analysis and brush cytology.

There are several caveats regarding staining, Dr. Foulks said. For instance, fluorescein solution must mix well with the tear and completely cover the ocular surface, while when using rose bengal, it is important to note that the use of topical anesthetic to relieve pain prior to installation can increase staining. With lissamine green, adequate volume must be instilled, a low level of illumination is necessary, and measurements should be taken at least 1 minute after installation but no later than 4 minutes afterward.

Also, clinicians should be aware of the differences in ocular surface staining between healthy eyes and those with dry eye disease. In up to 50% of healthy eyes, staining occurs in the periphery or limbus, and in less than 5% of cases in the central cornea. In eyes with dry eye disease, staining in both the conjunctiva and cornea occurs in a progressive pattern. Dr. Foulks recommended that clinical trials differentiate between central and peripheral staining outcomes and that clinical grading systems be refined.

Francis S. Mah, MD, discussed therapies for dry eye. Medical therapy is used in most cases and can consist of several steps: eliminating exacerbating medications; ocular environment interventions; computer work site interventions; aqueous tear enhancement with topical agents or other means; or medications.

Various medical approaches are available, including artificial tears, low-dose corticosteroids, cyclosporine A, and autologous serum. Oral medications may be appropriate for patients who have dry mouth as well as dry eye.

Over the counter dry eye drops are the most commonly used treatment. Faced with shelves full of products at the store, consumers are often unsure which to choose. Characteristics to look for include minimal blur, comfort upon instillation, even spreading over the cornea, prolonged retention time, and objective and subjective improvement in patient signs and symptoms.

Surgical treatment may be used if medical treatment has been inadequate or is impractical, said Dr. Mah, who is assistant professor of ophthalmology, University of Pittsburgh School of Medicine and director of the Clinical Vision Research Center. For patients with aqueous tear deficiency, surgical options include correction of lid abnormality, punctal or lacrimal occlusion, and tarsorrhaphy for severe cases. In a few severe instances, filamentary keratopathy, topical mucolytic agents, or scleral contact lenses also could be considered.

Regardless of the form of therapy, patient education is essential for improving compliance, and realistic expectations for treatment should be developed. Patients should understand that there is no cure for dry eye; treatment will help but will not eradicate all of their complaints and symptoms all of the time, Dr. Mah said.

This continuing medical education activity was jointly sponsored by the New York Eye and Ear Infirmary and cme², in partnership with Ophthalmology Times, and was supported through an unrestricted educational grant from Alcon Laboratories.

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