The anatomical and functional relationship between allergic conjunctivitis and allergic rhinitis

Abstract

There are numerous anatomic connections between the allergic conjunctivitis and allergic rhinitis. The most obvious reason is the physical connection via the nasolacrimal apparatus. However, a closer look at innervation, circulatory, lymphatic, and neurogenic systems reveals much more than a physical connection. The eye is richly innervated by parasympathetic nerves that enter the eyes after traveling in conjunction with the parasympathetic input to the nasal cavity. Parasympathetic innervation governing the tear film and nasal secretion can intersect at the pterygopalatine ganglion. Neurogenic inflammation affects both the eye and the nose as evidenced by the presence of the same neurogenic factors. Venous flow is in the SOV area connecting the eye and the nose, once thought to be without valves. In the past, this thinking is the basis for concern about the danger triangle of the face. Recent literature has shown otherwise. Although valves are present, there are still pathways where bidirectional flow exists and a venous connection is made. The most likely area for venous communication is the pterygoid plexus and cavernous sinus. The venous flow and connections also offers a pathway for allergic shiners. Understanding the mutual connections between the nasal mucosa and the ocular surface can also affect treatment strategies.

Keywords: Allergic conjunctivitis; cavernous sinus; naso-ocular reflex; nasolacrimal; neurogenic inflammation; ocular allergy; pterygoid plexus; pterygopalatine ganglion; rhinitis.

Figure 1.

Ocular surface and nasal innervation. The majority of the innervation to both the nasal and the ocular surface originates or passes through the pterygopalatine ganglion. (Modified from Ref. 71).

Figure 2.

Neurogenic inflammation conjunctiva for allergic conjunctivitis (AC). (1) Histamine release binds to H1–4 receptors of mast cell and sensory nerves within the substantia propria of the conjunctiva (H3 receptors have not yet been identified in the eye to date). (2) Responses such as itch are elicited in the cortex. (3) Subsequent release of neuropeptides substance P (SP), calcitonin gene–related peptide (CGRP), vasoactive intestinal peptide (VIP), and other neurotransmitters. (4) Binds to receptors on the same (autocrine) and nearby (paracrine) mast cells, resulting in more histamine release. (Modified from Ref. .)

Figure 3.

Venous system between the ocular surface and the nose. The valves (V) are shown in the figure. Arrows depict the blood flow. (Modified from Ref. .)