discovering dry eye
Allergies or Dry Eye?
BY BARBARA CAFFERY, OD, MS, FAAO
It is now time for buds to appear on the trees, the sun to shine and the temperature to climb. Most of our patients will be in better moods as the season changes in the Northern Hemisphere. When the heat goes off indoors, the
When the heat goes off indoors, the dryness will decrease and some symptoms of dry eye will dissipate. However, the new spring growth adds to the mix of anterior segment symptoms. It requires our diligent clinical skills to determine: dry eye, allergy or both?
Patient history is important in making your diagnosis. The most common form of ocular allergy is seasonal allergic conjunctivitis (SAC). Symptoms like ocular itching, tearing and burning begin once pollens and antigens appear. Dry eye patients have less seasonal variation. They present with symptoms of discomfort, dryness and irritation, and are less likely to report itchiness as a primary symptom.
The inflammatory responses of these two conditions also differ. SAC is a prototypic type I anaphylactic hypersensitivity reaction. Patients suffering from this disease have elevated levels of IgE in their tears, and we have found serum and pollen in their tear films. Also present are elevated levels of histamine and eosinophil major basic protein.
The most common inflammatory form of dry eye disease is Sjögren's syndrome. In this disease, specific T and B inflammatory lymphocytes invade the lacrimal gland.
Recent investigations of inflammatory markers in milder dry eye cases suggest that the ocular surface is inflamed by more than just dryness. Prostaglandins and cytokines have been analyzed but are difficult to clinically measure and characterize.
Investigate, Observe, Diagnose
The clinician must lead with the history and use clinical observations to determine the cause of the ocular surface symptoms. Allergic patients demonstrate excess mucous in the tear film that may be copious. Staining may be present in the nasal conjunctiva due to vigorous rubbing. Corneal staining is not common except where the patient has rubbed mucous strands into the epithelium. There may be limbal follicles and significant folliculosis of the superior and inferior tarsal plates.
Dry eye patients have some debris in the tear film but are less likely to have copious mucous strands. Fluorescein and rose bengal typically reveal nasal and temporal staining of the conjunctiva. Inferior corneal staining reveals blepharitis and meibomian gland dysfunction. The Schirmer tear test is definitive in that dry eye patients will have less than 10mm of secretion in five minutes.
Treat Me Right
There are both differences and similarities in dry eye disease and SAC. Use your diagnosis to make the correct treatment choices and manage patients well.
Allergic patients need to avoid the allergen as much as possible. Cold compresses reduce symptoms, and flushing the eyes with cold saline can reduce the pollen load on the surface of the eye. Vasoconstrictors and allergy medications can manage the problem well.
Dry eye patients require hot compresses to promote meibomian gland secretions. Saline flushes can help those who awaken with gritty sore eyes. Lubricants help promote tear film stability.
The red herring is that patients with dry eyes can also experience allergic conjunctivitis, and may even be prone to seasonal conditions because of their inability to flush the ocular surface. Diagnosis and management of these patients is a tricky issue. Welcome to springtime in the Northern Hemisphere!
Dr. Caffery has practiced optometry in Toronto, Canada, in a group setting dedicated to contact lens and tear film research since 1977.