The vast assortment of pathologies that cause ocular redness has long been recognized, but clinicians may be neglecting an important evaluation—the redness itself. In this month’s column, we’ll demonstrate the array of vascular patterns, locations and hue of ocular redness indicative of unique ocular conditions.

Allergic Conjunctivitis
Histamine is the primary mediator of the allergic reaction. Following mast cell degranulation, it binds to H1 and H2 receptors on the vascular conjunctival endothelium and induces vasodilation. The redness associated with allergic conjunctivitis generally presents as mild, diffuse pinkness with scleral vessel involvement. The vessel leakage characteristic of allergic conjunctivitis leads to chemosis, which can produce a hazy effect, clouding the degree of redness observed.

Morning Eye Congestion
Fine, linear conjunctival and ciliary vessel dilation may indicate morning eye congestion, which is primarily caused by the low-grade state of inflammation under the lids as we sleep. Allergens, microorganisms and irritants trapped in the closed eye rouse a small-scale immune reaction, wherein leukocytes work to clear the conjunctiva of intruders. The blink ceases with eye closure, but some fresh meibomian and lacrimal secretions still emerge. These are trapped by the lids, and the lactoferrin, lysozyme, lipocalin and immunoglobulin A present in them contribute to innate ocular defense.1 Thus, the eye remains in a state of sub-acute inflammation throughout the night, and its products—swelling and redness—are observable upon waking.2 Recent research by our R&D team at Ora, Inc., led to the development of a new ocular redness scale representative of the redness that is associated with morning eye congestion for purposes of clinical research.

Dry Eye and Contact Lenses
While allergic conjunctivitis is generally accompanied by itching, stinging, chemosis and redness, patients with dry eye will exhibit redness alongside symptoms of burning, grittiness, foreign body sensation and/or photophobia.

Along with variation in symptomatology, the physical characteristics of redness are also unique. Fine horizontal vessel dilation with a mild red color mainly evident in the interpalpebral fissure should prompt the clinician to consider dry eye diagnosis. But, redness associated with contact lens wear is largely present in circumlimbal locations. The amount of redness observed is generally consistent with corneal edema.

Ocular Allergic Reaction
Allergic reaction to topical ophthalmics produces a “beefy” redness in the lower half of the eye. The lower half of the conjunctiva, inferior cul-de-sac and lower lid demonstrate such redness, while the upper portions appear unaffected due to gravitational effect upon instillation of the offending agent.

Marginal Infiltrates
Marginal infiltrates—the leakage of white blood cells in the peripheral cornea—are accompanied by fine vessel dilation, which manifests as localized conjunctival redness. The hue is generally deep pink. Observation of this hallmark pattern of redness merits careful examination of the contiguous limbus for infiltrates.

Bacterial Conjunctivitis
Patients with bacterial conjunctivitis present with superficial vasodilation—especially in the bulbar conjunctiva—and rarely with limbal involvement. Redness accompanying bacterial conjunctivitis generally begins unilaterally, increases in intensity as the disease progresses and is typically observed in conjunction with mucopurulent discharge.3

Severe Ocular Infection
Serious ocular infections (e.g., endophthalmitis, corneal ulceration) also demonstrate distinctive states of ocular redness. In general, redness resulting from these severe infections presents anywhere from a deep, “fire engine” red to near-purple hues. Deep scleral vessel involvement is common.

As we discussed in November’s column (“Recognizing Iritis”), a pink circumlimbal halo surrounding the cornea is a hallmark of iritis. This circumlimbal flush of dilated ciliary blood vessels is a feature of iritis regardless of etiology and should prompt further investigation.

Differentiate Ocular Redness
Despite its long-lived recognition as a clinical sign, the importance of the appearance of ocular redness itself has been overlooked in ophthalmic and optometric examination. Physical distinctions in ocular redness suggest valuable insight into the ocular condition and warrant diligent clinical inspection. Taking the time to characterize the vessel caliber, hue and location of ocular redness is a simple step with the potential to reveal substantial hints of causation. 

1. Sack RA, Conradi L, Krumholz D, et al. Membrane array characterization of 80 chemokines, cytokines, and growth factors in open- and closed-eye tears: angiogenin and other defense system constituents. Invest Ophthalmol Vis Sci. 2005 Apr;46(4):1228-3.
2. Sack RA, Conradi L, Beaton A, et al. Antibody array characterization of inflammatory mediators in allergic and norm al tears in the open and closed eye environments. Exp Eye Res. 2007 Oct;85(4):528-38.
3. Terry RL. Clinical Recognition of Anterior Segment Inflammatory Disease. In: Stapleton F (ed.) Anterior Eye and Therapeutics. Elsevier. Philadelphia; 2003: 1-39.