Episcleritis - Clinical Tree

Key Concepts

Simple episcleritis is usually benign and self-limiting.
Simple episcleritis is much more common than nodular episcleritis.
Nodular episcleritis has a well-demarcated, elevated area of inflammation.
Severe discomfort is rare and may represent scleritis.
Appearance is a brick red discoloration.
Cases are most often idiopathic.
Treatment is usually unnecessary with simple episcleritis.

Episcleritis is a relatively benign, self-limiting condition affecting the outer coat of the eye. There are few if any serious sequelae, and it therefore demands little in terms of evaluation and treatment. Clinically, the condition is categorized as either simple or nodular. Nodular episcleritis has a well-demarcated, elevated area of inflamed episcleral tissue. The simple form demonstrates vascular congestion of the episclera but without a discrete nodule.

Episcleritis should not be thought of as simply a mild version of scleritis. These two diseases should instead be regarded as distinct clinical entities, since the implications of the usually harmless episcleritis differ significantly from the more ominous scleritis.

Anatomy

The episclera is comparable to a synovial membrane, allowing smooth movements of the globe as would the synovial tissue in a ball-and-socket joint. The rheumatologic analogy goes further when one considers the higher incidence of scleral and episcleral inflammatory conditions associated with rheumatologic conditions.

The episclera is a fibroelastic structure consisting of collagen bundles, fibroblasts, melanocytes, proteoglycans, and glycoproteins. ^, It has two layers: an outer parietal layer and a deep visceral layer. These two layers are loosely fused by fine connecting fibers. The outer parietal layer, which is the more superficial, is vascularized by the superficial episcleral capillary plexus. This capillary plexus with its uniquely straight and radially oriented vessels helps distinguish this layer from the deep visceral layer ( Fig. 100.1 ). The outer parietal layer fuses with the muscle sheaths. As it approaches the limbus, the outer parietal layer also fuses with conjunctiva and the deep visceral layer of the episclera.

The visceral layer, which is closely adherent to the sclera, contains the deep episcleral capillary plexus. The freely anastomosing configuration of this capillary plexus characterizes this layer. Both the superficial and deep plexuses derive their blood supply predominantly from the anterior ciliary arteries. However, the posterior ciliary arteries do provide some episcleral circulation posterior to the muscle insertions.

While the vascular plexus of the conjunctiva is also somewhat interlacing, it is readily distinguished from the two deeper layers by its free mobility over them.

Incidence

Episcleritis is not a very common condition. The true incidence is difficult to determine, however, since patients often do not seek medical advice for self-limiting, asymptomatic conditions. Williamson has suggested that 0.08% of new hospital visits may be attributable to episcleritis. The Pacific Ocular Inflammation Study, a population based study, found the incidence of episcleritis to be 21.7 cases per 100,000 person years. Data obtained from the Northern California Epidemiology of Uveitis Study found the overall incidence of episcleritis to be 41.0 per 100,000 person years, with an annual prevalence ratio of 52.6 per 100,000.

Several large studies have been conducted that offer significant insight into the characteristics of patients with episcleritis: Watson and Hayreh’s reported cases from the Moorfield’s Eye Hospital (group I), the Sainz de la Maza et al. study from The Massachusetts Eye and Ear Infirmary (group II), Akpek et al. also from The Massachusetts Eye and Ear Infirmary (group III), Jabs et al. from The Wilmer Eye Institute (group IV), the pediatric study by Read et al. at the University of Washington (group V), and the Sainz de la Maza et al. study from Cambridge, Massachusetts, and Barcelona, Spain. Table 100.1 provides an overview of their findings. The adult groups found either no significant sex predilection or a predominance of women affected. The pediatric group demonstrated mostly male involvement. All study groups found the simple variety of episcleritis to be the most common. Sixty-seven percent of simple episcleritis is so-called sectoral, involving only one sector ( Fig. 100.2 ), and 33% have the diffuse variety of simple episcleritis, according to study group I.

TABLE 100.1

Characteristics of Patients With Episcleritis

	Group I ∗	Group II ^†	Group III ^‡	Group IV ^§	Group V ^¶	Group VI ^¶¶	Group VII ^∗∗
Number of eyes	217	127	132	55	18	85	93
Simple/nodular	78%/22%	83%/17%	84%/16%	81%/19%	92%/8%	69%/31%
Sex (% female)	45	74	69	70	17	63.5	60
Average age	Fourth to fifth decade	43 years	43 years	45 years	9 years	47.4	45
Bilaterality	37%	35%	32%	49%	50%	40%
Associated diseases	26%	32%	36%	35%	50%	27%

∗ Data from Watson PG, Hayreh SS. Scleritis and episcleritis. Br J Ophthalmol 1976; 60 :163.

† Data from Sainz de la Maza M, Jabbur NS, Foster CS. Severity of scleritis and episcleritis. Ophthalmology 1994; 101 :389.

‡ Data from Akpek EK, Uy H, Christen W, et al. Severity of episcleritis and systemic disease association. Ophthalmology 1999; 106 :729.

§ Data from Jabs DA, Mudun A, Dunn JP, et al. Episcleritis and scleritis: clinical features and treatment results. Am J Ophthalmol 2000; 130 :469.

¶ Data from Read RW, Weiss AH, Sherry DD. Episcleritis in childhood. Ophthalmology 1999; 106 :2377.

¶¶ Data from Sainz de la Maza M, Molina N, Gonzalez-Gonzalez L. Clinical characteristics of a large cohort of patients with scleritis and episcleritis. Ophthalmology 2012; 119 :43.

∗∗ Data from Homayounfar G, Nardone N, Borkar DS, et al. Incidence of scleritis and episcleritis:results from the Pacific Ocular Inflammation Study. Am J Ophthalmol 2013; 156 :752.

Clinical Manifestations

History

Episcleritis generally has an acute onset, particularly in the simple form. A patient is often able to pinpoint the exact time that a painful episode began. Nodular episcleritis may have a somewhat more insidious onset. However, approximately half of the time, discomfort may not be the presenting complaint, since the condition may be asymptomatic. An area of episcleral painless injection may be noted incidentally.

When pain is present in episcleritis, it is usually a mild discomfort. The terms hot, prickly, and foreign body-like are most commonly used to describe the sensation. It is possible, although quite rare, to have severe pain in episcleritis. If pain of this degree is present, the diagnosis of episcleritis is in question, and one should suspect scleritis.

Photophobia is present in a small number of patients. Tenderness may also be described and is usually localized to the inflamed area. An important historical point is the exclusion of ocular discharge. While infectious conditions typically cause either a purulent or a mucopurulent discharge, episcleritis causes only a watery discharge.

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