Ocular Allergies
Allergy season usually comes upon us... with a vengeance. Mild temperatures usually allow the pollen counts to rise rapidly, resulting in many uncomfortable allergy sufferers.
The allergic response is a hypersensitivity reaction to foreign particles in the air (commonly pollen or mold spores), which lead to the sudden onset of a stuffy nose, respiratory difficulties and watery, itchy eyes. Nasal irritation leads to sneezing and post-nasal drainage can result in sore throats and chronic coughs.
When an allergen (a substance to which you are allergic) comes in contact with your nasal/respiratory mucus membranes or your conjunctiva, it binds to immune cells called mast cells. Once bound, these cells release molecular signals such as histamine, prostaglandins and leukotrienes. These signals quickly promote dilation the surrounding blood vessels and increase the "leakiness" of the blood vessels. The result, extremely simplified, is congestion of the nose and swelling, redness and itching of the conjunctiva. This reaction can occur within minutes of contacting the specific allergen.
Treatment of allergic conjunctivitis can be both preventive and symptomatic. The acute allergic conjunctivitis can be prevented by applying topical drops that help prevent the molecular signals from being released by the mast cells. These chemicals are known as mast cell stabilizers. Cromolyn sodium, Alomide and Alamast are three of the first mast cell stabilizers available in drop form. It is important to note that these medications are not useful for treating acute attacks. They must be used for several days before they begin to protect the eye from an allergic reaction. Newer medications, such as Optivar, Pataday and Alocril, not only stabilize the mast cells, but also act as an anti-histamine. This dual action makes them especially effective. Zaditor and Elastat are new medications that work well and have a similar mechanism of action to Optivar. All of these medications (except Zaditor) require a prescription.
The symptomatic relief of allergic conjunctivitis can be achieved by the use of topical steroid drops, non-steroidal anti-inflammatory drugs (NSAIDS), or topical antihistamines. Steroids are very effective, but can have serious side effects with chronic use, such as cataracts and glaucoma. They are useful in more severe cases. Topical NSAIDS are very safe, and can provide significant relief of symptoms. However, they may not give immediate relief. For this, an anti-histamine is most effective. There are both prescription (Livostin) and non-prescription (Vasocon, Naphcon, and Ocu-Hist) anti-histamine drops available. All types probably work equally well and are safe to use as needed on a chronic basis.
Of course, seasonal allergies are not just an ocular disease, but usually involve the entire respiratory system as well. Thus, systemic treatment with oral anti-histamines, inhaled bronchodilators and nasal sprays is usually required to make the patient comfortable. That is why your primary care physician is first person to turn to for relief from symptomatic seasonal allergies.
