Sunday, October 1, 2023
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Although the evaluation of a glaucoma patient on medical therapy complaining of red eyes may not have the cachet of performing nonpenetrating surgery or laser angle therapy, it is nevertheless an essential component of the successful care and management of patients with this disease. Indeed, red eyes can prove particularly troublesome if they become persistent and therefore affect the tolerability of the agent -- which in turn affects compliance. Poor compliance can result in treatment failure due to a decrease in overall intraocular pressure (IOP) control. Because glaucoma is the second leading cause of blindness worldwide[1] and currently pharmacologic IOP lowering is the first-line therapeutic option for glaucoma, the advent of red eyes in a patient is not uncommon. It is therefore of the utmost importance to be able to identify red eyes, to distinguish the cause of the red eyes -- whether from a true allergic reaction, ocular surface disease, or irritation from the medication itself -- and to act to alleviate the problem so that adherence and treatment efficacy are not compromised.
Hyperemia, or redness alone in clinical terms, is only a sign of a problem, and may be associated with a broad group of ocular diseases or, possibly, be part of a response to allergic inflammation or irritation. Within the eyes, the redness that we see is caused by the vasodilatation of the conjunctival blood vessels against the white background of the sclera.[2] The presentation of red eyes, however, is only a starting point in the diagnostic sleuthing necessary to find and treat its underlying cause. Allergists will generally treat obvious atopic conjunctivitis, but they refer to ophthalmologists for more extensive differential diagnosis.
To make the diagnosis, there are various grading systems available, including standard photographic charts[3] and the Corneal and Contact Lens Research Unit (CCLRU) grading scale.[2] They include verbal descriptions and photographs that illustrate increasing levels of conjunctival hyperemia. Although conjunctival hyperemia is an important clinical sign of ocular disease or inflammation, it is important to note that even a normal eye has a degree of hyperemia; it is more common in males than females; and the area of the nasal bulbar has the highest grading. It is thus the degree of hyperemia, not its presence alone, which separates normal from abnormal.
Hyperemia is a symptom; allergy, on the other hand, refers to a specific process that stimulates inflammation. True allergic (atopic, type I) reactions stem from hypersensitivity to a substance (allergen). There is an antibody-antigen interaction, and a cascade of events follow associated with the release of inflammatory mediators from cells; hyperemia is commonly an outcome of the event. There is some difficulty in distinguishing a true ocular allergy. Grading systems of ocular allergies are not consistent because the presentation and location can be quite variable. The other difficulty is the issue of defining what a true allergy is. Hyperemia, pruritus, folliculosis, and conjunctival allergy have been all or partially included under the umbrella of ocular allergy, and the presence or absence of some of those will influence the measured incidence of allergy in a particular study. For the conjunctival reaction, it may be proper to include all 3 -- hyperemia, pruritus, and conjunctival follicles -- to fully describe the allergic reaction. Periocular dermatitis, a type IV delayed cell-mediated hypersensitivity associated with scaling, crusting, and erythema around the area of involvement, is a clinical diagnosis not requiring a grading system.
The importance of tolerability as it affects adherence to medication usage cannot be underestimated. Therefore, patients with red eyes require a systematic evaluation of symptoms and signs to be successfully diagnosed and treated. A comprehensive ocular-visual assessment should begin with first principles to determine the source of the problem.
Initially, it is essential that problems such as marginal blepharitis, meibomian gland dysfunction, and underlying dry eyes be identified and managed. A significant percentage of glaucoma patients are women older than the age of 50, and this group of patients tends to be much more predisposed to dry eyes.[4] It has also become clear that the use of multiple medications, either because of the medications themselves or the associated preservatives, will aggravate this dry eye condition.[5,6] The use of Schirmer's evaluation, fluorescein, and rose Bengal staining to evaluate the tear film can confirm an underlying dry eye problem. The dry eye can then be managed with the use of nonpreservative tears and gel, and ideal lid hygiene.
Contact type allergies (type IV) have extension of erythema well beyond the lid margin, and can occur with many medications, but tend to be more common with sulfa-based preparations. An underlying problem, blepharitis, is commonly associated with the elderly population, and the earlier the identification and intervention -- with improvement of lid hygiene -- the more rapidly symptoms can be controlled.
A final point of confusion is seasonal allergies. Airborne allergens, including pollen, dust, and molds, cause inflammation on the ocular surface, especially for patients who already have dry eyes. It is imperative that this problem be differentiated from responses to glaucoma medications. This is usually accomplished by attention to the patient's history and transient nature of the symptoms. It then can be treated with appropriate anti-allergic medications not requiring the discontinuation of the patient's ocular medications.
