The Sclera

Sclera

** Also known as the white of the eye, is the opaque, fibrous, protective, outer layer of

fibers. elastic and collagen containing eye the (it forms 5/6 of the anterior outermost layer of the eye).

** It’s formed from interwoven collagen fibrils of different widths lying within a ground substance and maintained by fibroblasts.

** It’s of variable thickness, 1 mm around the optic nerve head and 0.3 mm just posterior to the muscle insertions.

** In adults, the sclera is white.

** In some children, the sclera is blue due to

it’s thinning that shows the pigment cells of

the choroid.

** In the elderly, it maybe yellow due to

deposition of fat.

Anatomy of the Sclera

• The Sclera is divided into 3 layers :

1) The episclera.

2) Scleral stroma.

3) Lamina fusca.

1) Episclera :

• it’s the outermost layer

• Anteriorly the episclera consists of a dense,

vascular connective tissue which lies between

the superficial scleral stroma and Tenon

capsule.

** Tenon capsule : the facial sheath that envelopes the

eyeball and seperates it from the orbital fat.

2) Scleral stroma :

• it’s a dense fibrous tissue with fine elastic fibers.

3) Lamina fusca :

it’s the innermost layer of the sclera , it

continues with the suprachoroidal and

supraciliary lamellae of the uveal tract.

Diseases of the sclera

Episcleritis

• It’s the inflammation of the superficial layer of the

sclera,it’s a common, benign, usually idiopathic,

recurrent and frequently bilateral condition.

• It causes mild discomfort , and it’s rarely associated with

systemic diseases.

• It’s usually self-limiting , but as the symptoms are

tiresome , topical anti-inflammatory treatment can be

given.

• In rare severe cases systemic anti-inflammatory drugs

maybe given.

• And it’s classified into simple and nodular types.

A. Simple Episcleritis

• Simple episcleritis accounts for 3/4 of all cases and predominantly affects females. It has a great tendency to recur either in the same eye, or sometimes both together. The attacks become less frequent and after many years disappear completely.

** Presentation is with redness and mild discomfort

** Signs Redness may be sectoral or diffuse. Often it has an interpalpebral distribution, in contrast with scleral disease which commonly starts in the upper temporal quadrants.

** Treatment If mild, no treatment is required. • Cool artificial tears may be adequate in some cases. • A weak topical steroid for 1–2 weeks is usually sufficient. • Oral NSAIDs are sometimes required for 10 days.

B. Nodular Episcleritis

• Nodular episcleritis also tends to affect young females

but has a less acute onset and a more prolonged course

than the simple variety.

**Presentation is with a red eye typically first noted on waking.

Over the next 2–3 days the area of redness increases in size,

becomes more uncomfortable, but remains in the same

position.

** Signs one or more tender nodules, almost always within the

interpalpebral fissure.

**Treatment is similar to that of simple episcleritis.

Simple episcleritis A.sectoral B.diffuse

Nodular episcleritis

Scleritis

** Scleritis is an uncommon condition characterized by edema and cellular infiltration of the entire thickness of the sclera. It is much less common than episcleritis and covers a spectrum ranging in severity from self-limiting episodes to a necrotizing disease that may involve adjacent tissues and threaten vision.

** It can be associated with collagen vascular diseases, most commonly rheumatoid arthritis.

** It causes intense occular pain, and both inflammatory and ischemic areas may occur in the sclera. ** Scleritis affecting the posterior part of the globe may cause choroidal effusions or simulate a tumor.

** The following may complicate the situation :

*Scleral thinning (scleromlalacia), sometimes with

perforation.

*Keratitis.

*Uveitis

*Cataract formation.

*Glaucoma.

** Treatment may require high doses of systemic

steroids or in severe cases cytotoxic therapy and

investigation to find any associated systemic

diseases.

Infectious scleritis

• Infectious scleritis is rare but may be difficult to diagnose because the initial clinical features may be similar to those of immune-mediated disease. In some cases infection may follow surgical or accidental trauma, severe endophthalmitis, or may occur as an extension of primary corneal infection .

• Causes : 1)herpes zoster. 2)tuberculous scleritis. 3)leprosy. 4)syphilis. 5)lyme disease.

Infectious scleritis

Blue sclera

** Blue discoloration is caused by thinning or

transparency of scleral collagen with

visualization of the underlying uvea.

**Important causes include the following:

1) Osteogenesis imperfecta.

2) Ehlers–Danlos syndrome type VI

3) Marshall–Smith syndrome , Russell–Silver syndrome ,

Hallermann–Streiff–François syndrome.

Osteogenesis Imperfecta

** It is an inherited disease of connective tissue, usually caused by defects in the synthesis and structure of Type 1 collagen. There are multiple types, at least two of which have ocular features.

Yellow Sclera

** It manifests in jaundiced patients, it’s not

due to pigment on the slcera itself but to

accumulation of bilirubin in the vascular

cojunctiva.

Thank you

Hala Shatnawi