dry eye dx and tx
When Are Ocular Allergies Dry Eye-Induced?
BY GREGORY J. NIXON, OD, FAAO
Along with all the buds and blossoms on the trees and shrubs, this spring was in full bloom with patients complaining of ocular irritation. While these generalized symptoms are commonly associated with ocular allergy, many of these cases were dry eye-related, especially for contact lens wearers.
Dry Eye-Induced Allergies
One function of the tear film is to dilute and remove environmental antigens and other debris from the ocular surface. When the tear volume is insufficient, antigens are present at a higher concentration and are often not readily cleared from the ocular surface due to impaired tear circulation. Further, if there is rapid tear film breakup time (TBUT), the 50 million mast cells that reside in the conjunctiva will be directly exposed to this high concentration of antigens. Exposure could then trigger the release of histamine and other inflammatory mediators that are responsible for the signs and symptoms of acute ocular allergies.
Differentiating ocular allergies from dry eye is based on many factors, the first of which is patient symptoms. Many of these patients complain of ocular itching and burning.
I often ask patients, "Does it itch more than it burns or burn more than it itches?" I commonly find that patients who complain of itching without other symptoms of ocular irritation such as burning or gritty sensation generally have a primary ocular allergy with an adequate tear film. However, I've found that a great majority of patients who include itching among other ocular irritation symptoms often have a dry eye-induced ocular allergy.
Examining these patients will reveal the characteristic signs of ocular allergies such as diffuse injection of the bulbar conjunctiva and papillary hypertrophy of the palpebral conjunctiva. However, you also may see poor tear quality including tear film debris, reduced TBUT and even increased lens deposition from the excessive tear film debris. It's often unclear whether these tear film findings are the result of ocular inflammation or a contributor to it.
Acute and Chronic Management
Whether a patient's ocular allergy is dry eye-induced or not, the first step is to treat the acute allergic inflammation to address patient symptoms and achieve ocular comfort. You can typically accomplish this by dosing a topical antihistamine/mast cell stabilizer combination medication q.d to b.i.d. or a topical steroid b.i.d. to q.i.d. depending on severity.
These medications should bring fairly quick and substantial relief from ocular itching symptoms. However, if after one week of treatment there are still signs of diminished tear prism, decreased TBUT and inferior third corneal staining, this is likely evidence of an underlying dryness issue that may have instigated or worsened the allergy response.
Like all dry eye patients, the goal of treatment from this point forward should be to maximize comfort and minimize ocular health side effects. This typically requires chronic treatment with a daily or two-week disposable contact lens, combined with an appropriate disinfection system and non-preserved artificial tear supplementation to help maintain ocular surface hydration, contact lens hydration and tear circulation. CLS
Dr. Nixon is an associate professor of clinical optometry and the extern coordinator at The Ohio University College of Optometry. He is also in a group private practice in Westerville, Ohio.