The Sclera Sclera Also known as the white

The Sclera

Sclera ** Also known as the white of the eye, is the opaque, fibrous, protective, outer layer of the eye containing collagen and elastic fibers. (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.

Nodular episcleritis Simple episcleritis A. sectoral B. diffuse

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) 2) 3) Osteogenesis imperfecta. Ehlers–Danlos syndrome type VI 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