Anatomy & Function
The conjunctiva is the clear yet highly vascularized mucus membrane that covers the sclera and lines the inside of the eyelid.
The main function of the conjunctival epithelium is to provide a tight barrier to seal the interior of the ocular surface against the entrance of foreign particles. Interestingly, it also has a number of functions related to transport and secretion.
Conjunctival injection (aka hyperemia) is a nonspecific finding caused by dilation of the conjunctival vasculature, which can be induced by a range of conditions. It can range from mild to severe.
In the eye, elastin is predominantly found in the innermost layer of the conjunctiva (the subepithelial lamina propria) and the contiguous episclera. Thus, when we see yellowing of the eyes in patients with jaundice, we should use the term “conjunctival icterus”—”scleral icterus” is a misnomer!
Conjunctival pallor, which is associated with chronic anemia, is best evaluated by pulling down on the lower eyelid and visualizing the anterior and posterior rims of the conjunctiva. Normally, the anterior rim is bright red while the posterior rim has a pale
color (Figure 2). In patients with conjunctival rim pallor, the anterior rim and posterior rim are both the same pale color (Figure 1). If present, conjunctival rim pallor has a positive likelihood ratio of 16.7 for the presence of anemia.