The Acute Red Eye in the Elderly
Robert J. Campbell MD, MSc and William G. Hodge MD, PhD, FRCSC, University of Ottawa Eye Institute, Ottawa, ON.
The differential diagnosis of the red eye involves structures ranging from the periorbita, lids and conjunctiva, to the surface sclera and episclera, to the cornea and uvea and to acute angle closure glaucoma. The history and physical examination can usually differentiate these entities from one another. The most important part of the examination is the visual acuity, which can usually distinguish the serious red eye from more benign causes.
Key words: orbital cellulites, conjunctivitis, blepharitis, keratitis, acute glaucoma, red eye.
An acute red eye often causes much anxiety for patients and physicians alike. For the clinician, this stems from the fact that the underlying diagnosis may range from innocuous, minor problems to potentially sight-threatening etiologies. Moreover, while in many cases specific clinical signs are present that can greatly help in the differential diagnosis, they are often subtle and may require specialised equipment not readily available in many clinical settings. However, armed with an appropriate understanding of the potential causes, a thorough history and some readily available clinical signs, the non-specialist clinician can make a sound diagnosis and initiate appropriate therapy or make a timely referral.
Clinical Approach
The key to making a proper diagnosis, as always, rests on an appropriately thorough history and a careful physical examination. Perhaps the most important element of the history is the presence of a recent decline in visual acuity. Additionally, the onset, duration and laterality of the red eye must be determined and the possibility of trauma should be explored carefully. Important associated features include pain, burning sensation, foreign body sensation, itching, and discharge which may be watery, mucoid or purulent in nature. The patient's medical and ocular histories may be very relevant, particularly histories of allergy, upper respiratory tract infection or recent ophthalmic surgery. Finally, the use of topical medications is an important historical element.
Physical examination should begin with a careful assessment of visual acuity using the patient's appropriate distance refractive correction or a pinhole aperture. Next, one can proceed "from outside to in", beginning with an examination of the periorbital and orbital tissues while paying special attention to any signs of proptosis and ocular motility deficits. The globe itself may then be examined beginning with the conjunctiva, noting the predominant focus of vessel injection--forniceal or circumcorneal, focal or diffuse. The presence of discharge may be noted in the fornices or on the lids. The cornea may be examined both with white light and, ideally, with fluorescein and cobalt blue illumination as well. Finally, the iris and pupil should be examined. In particular, the ease with which iris details can be viewed provides an index of corneal clarity. The size, shape and reactivity of the pupil also furnish important diagnostic clues. Elements of the history and physical examination that increase the likelihood of a serious disorder are highlighted in Table 1.
Important Elements of the Differential Diagnosis
Armed with clues from the clinical history and physical examination, we can proceed to a logical anatomical and mechanistic breakdown of the causes of the red eye (clinical entities summarised in Table 2). From a mechanistic viewpoint, the eye will assume a red appearance whenever there is an increased presence of blood in or under the normally transparent conjunctival membrane. This blood may be intravascular, may be in dilated blood vessels that have become congested secondary to inflammation or may be a consequence of increased venous pressure. Alternatively, this blood may be extravascular in the form of