Sclera

Last revised by Dr Daniel J Bell on 29 Nov 2021

The sclera (plural: scleras or sclerae) is the fibrous, opaque white, coat of the eye. It functions to protect the intraocular contents. 

Outermost coat of the trilaminar globe. Anteriorly continuous with the cornea. Posteriorly perforated by the optic nerve at the lamina cribrosa

The sclera is an alymphatic organ.

Anteriorly supplied by the long ciliary nerves. Posteriorly supplied by the short ciliary nerves

The sclera may be divided into three histological layers:

  1. episclera
    • outermost, loose connective tissue layer, connected to the Tenon capsule
    • rich vascular supply from anterior ciliary arteries
  2. scleral stroma
    • dense fibrous tissue intermingled with fine elastic fibers
    • irregular arrangement of type I and III collagen responsible for its opacity
  3. lamina fusca
    • innermost layer with melanocytes
    • weakly related to the choroid

Ultrasound and CT are not useful modalities. 

  • readily used in clinical practice to measure scleral thickness, monitor therapeutic response in scleritis treatment
  • quantitative measurements obtained 
  • useful in the diagnosis of posterior scleritis and episcleritis 
  • T1-weighted sequences, sclera appears as the hypointense rim of the globe 

The word derives from medical Latin, itself from the Greek sklera "the hard (membrane)," feminine form of skleros "hard".

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