Anatomy
The scleral stroma is composed of collagen bundles of varying size and shape that are not uniformly orientated as in the cornea, and so are not transparent. The inner layer of the sclera (lamina fusca) blends with the uveal tract. Anteriorly the episclera consists of a connective tissue layer between the superficial scleral stroma and Tenon capsule. There are three pre-equatorial vascular layers:
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Conjunctival vessels are the most superficial; arteries are tortuous and veins straight.
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Superficial episcleral plexus vessels are straight with a radial configuration. In episcleritis, maximal congestion occurs at this level ( Fig. 8.1A ). Topical phenylephrine 2.5% will also constrict the conjunctival and 10% also the superficial episcleral vessels.
Fig. 8.1
(A) Diffuse episcleritis with maximal vascular congestion in the superficial episcleral plexus; (B) scleritis with congestion of the deep vascular plexus
(Courtesy of P Watson – fig. A; S Chen – fig. B)
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Deep vascular plexus lies in the superficial part of the sclera and shows maximal congestion in scleritis ( Fig. 8.1B ); a purplish hue, best seen in daylight, is characteristic.
Episcleritis
Episcleritis is a common, usually idiopathic and benign, recurrent and frequently bilateral condition. Females may be affected more commonly than males, except possibly in children, in whom episcleritis is rare; the average patient is middle-aged. It is typically self-limiting and tends to last from a few days up to 3 weeks, but rarely longer. Associated disease, either ocular (e.g. dry eye, rosacea, contact lens wear) or systemic (e.g. collagen vascular disorders such as rheumatoid arthritis, herpes zoster ophthalmicus, gout and others) has been identified in up to a third of patients seen at tertiary centres, with ocular disease the most common. Infectious causes are very rare but a wide range has been reported. Investigation of recurrent cases is as for scleritis (see later).
Simple episcleritis
Simple episcleritis accounts for 75% of cases. It has a tendency to recur (60%), decreasing in frequency with time. Features often peak within 24 hours, gradually fading over the next few days.
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Symptoms. Redness; discomfort ranges from absent (up to 50%) to moderate and occasionally severe, when scleritis should be excluded. Grittiness is common, and photophobia may occur.
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Signs. More than half of cases are simultaneously bilateral.
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Visual acuity is almost always normal.
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Redness may be sectoral (two-thirds – Fig. 8.2A ) or diffuse ( Fig. 8.2B ). Often it has an interpalpebral distribution, in a triangular configuration with the base at the limbus.
Fig. 8.2
Simple episcleritis. (A) Sectoral; (B) diffuse
(Courtesy of JH Krachmer, MJ Mannis and EJ Holland, from Cornea , Mosby 2005 – fig. B)
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Chemosis, ocular hypertension, anterior uveitis and keratitis are all rare.
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Treatment
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If mild, no treatment is required; cool compresses or refrigerated artificial tears may be helpful.
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A weak topical steroid four times daily for 1–2 weeks is usually sufficient, though occasionally more intensive instillation is needed initially or a more potent preparation can be used with rapid tapering. A topical non-steroidal anti-inflammatory (NSAID) is an alternative, though may be less effective.
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An oral NSAID is occasionally required (e.g. ibuprofen 200 mg three times daily, or occasionally a more potent agent such as indometacin). It is very rare for more aggressive systemic treatment to be required, and this is typically in patients with a known systemic association.
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Nodular episcleritis
Nodular episcleritis also tends to affect females but has a less acute onset and a more prolonged course than the simple variant.
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Symptoms. A red eye is typically first noted on waking. Over the next 2–3 days the area of redness enlarges and becomes more uncomfortable.
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Signs. Attacks usually clear without treatment, but tend to last longer than simple episcleritis.
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A tender red vascular nodule, almost always within the interpalpebral fissure ( Fig. 8.3A ). Occasionally more than one focus is present.
Fig. 8.3
(A) Nodular episcleritis; (B) slit illumination shows that the deep beam is not displaced above the scleral surface
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A slit lamp section shows an underlying flat anterior scleral surface, indicating the absence of scleritis ( Fig. 8.3B ).
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Intraocular pressure (IOP) is very occasionally elevated.
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An anterior chamber reaction may be present, but is uncommon (10%).
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After several episodes inflamed vessels may become permanently dilated.
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It is important to exclude other causes of a nodule such as phlyctenulosis (a phlycten is within rather than beneath the conjunctiva) or a conjunctival granuloma.
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Treatment is similar to that of simple episcleritis but is more commonly indicated.
Immune-Mediated Scleritis
Scleritis is an uncommon condition characterized by oedema and cellular infiltration of the entire thickness of the sclera. Immune-mediated (non-infectious) scleritis is the most common type, and is frequently associated with an underlying systemic inflammatory condition, of which it may be the first manifestation. Scleritis is much less common than episcleritis and comprises a spectrum from trivial and self-limiting disease to a necrotizing process that can involve adjacent tissues and threaten vision. A classification of non-infectious scleritis is shown in Table 8.1 ; recurrences tend to be of the same type, though 10% progress to more aggressive disease.
| Anterior |
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| Posterior |
Anterior non-necrotizing scleritis
Diffuse
Diffuse disease is slightly more common in females and usually presents in the fifth decade.
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Symptoms. Ocular redness progressing a few days later to pain that may radiate to the face and temple. The discomfort typically wakes the patient in the early hours of the morning and improves later in the day; it responds poorly to common analgesics.
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Signs
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Vascular congestion and dilatation associated with oedema. If treatment is started early, which rarely happens, the disease can be completely inhibited.
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The redness may be generalized ( Fig. 8.4A ) or localized to one quadrant. If confined to the area under the upper eyelid the diagnosis may be missed.
Fig. 8.4
(A) Diffuse non-necrotizing anterior scleritis; (B) scleral translucency following recurrent disease
(Courtesy of M Jager – fig. B)
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Secondary features can include chemosis, eyelid swelling, anterior uveitis and raised IOP.
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As the oedema resolves, the affected area often takes on a slight grey/blue appearance because of increased scleral translucency ( Fig. 8.4B ); this is due to rearrangement of scleral fibres rather than a decrease in scleral thickness.
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Recurrences at the same location are common unless an underlying cause is treated.
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Prognosis. The average duration of disease is around 6 years, with the frequency of recurrences decreasing after the first 18 months. The long-term visual prognosis is very good.
Nodular
The incidence of nodular and diffuse anterior scleritis is the same but a disproportionately large number of those with nodular disease have had a previous attack of herpes zoster ophthalmicus. The age of onset is similar to that of diffuse scleritis.
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Symptoms. The insidious onset of pain followed by increasing redness, tenderness of the globe and the appearance of a scleral nodule.
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Signs
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Scleral nodules may be single or multiple and most frequently develop in the interpalpebral region close to the limbus ( Fig. 8.5A ). They have a deeper blue–red colour than episcleral nodules and are immobile.
Fig. 8.5
(A) Nodular non-necrotizing anterior scleritis; (B) slit illumination shows superficial displacement of the entire beam
(Courtesy of P Watson – fig. A)
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In contrast to episcleritis, a slit lamp beam shows an elevated anterior scleral surface ( Fig. 8.5B ).
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Multiple nodules may expand and coalesce if treatment is delayed.
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Instillation of 10% phenylephrine drops will constrict the conjunctival and superficial episcleral vasculature but not the deep plexus overlying the nodule.
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As the inflammation in the nodule subsides, increased translucency of the sclera becomes apparent.
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The duration of the disease is similar to diffuse scleritis.
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More than 10% of patients with nodular scleritis develop necrotizing disease, but if treatment is instituted early superficial necrosis does not occur and the nodule heals from the centre leaving a small atrophic scar.
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Anterior necrotizing scleritis with inflammation
Necrotizing disease is the aggressive form of scleritis. The age at onset is later than that of non-necrotizing scleritis, averaging 60 years. The condition is bilateral in 60% of patients and unless appropriately treated, especially in its early stages, may result in severe visual morbidity and even loss of the eye.
Clinical features
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Symptoms. Gradual onset of pain that becomes severe and persistent and radiates to the temple, brow or jaw; it frequently interferes with sleep and responds poorly to analgesia.
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Signs vary according to the following three types of necrotizing disease.
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Vaso-occlusive is commonly associated with rheumatoid arthritis. Isolated patches of scleral oedema with overlying non-perfused episclera and conjunctiva are seen ( Fig 8.6A ). The patches coalesce, and if unchecked rapidly proceed to scleral necrosis ( Fig. 8.6B ).
Fig. 8.6
Vaso-occlusive necrotizing scleritis with inflammation. (A) Early stage; (B) moderate disease – inflammatory signs are commonly more marked than in these cases
(Courtesy of C Barry – fig. B)
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Granulomatous may occur in conjunction with conditions such as granulomatosis or polyarteritis nodosa. The disease typically starts with injection adjacent to the limbus and then extends posteriorly. Within 24 hours, the sclera, episclera, conjunctiva and adjacent cornea become irregularly raised and oedematous ( Fig. 8.7 ).
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