Comprehensive Ophthalmology 7th Edition PDF Free Download
ANATOMY OF EYE
This chapter gives only a brief account of the anatomy of eyeball and its related structures. The detailed anatomy of different structures is described in the relevant chapters.
Each eyeball (Fig. 1.1) is a cystic structure kept distended by the pressure inside it.
• Shape. Although, generally referred to as a globe, the eyeball is not a sphere but an ablatespheroid, consisting of twasandifierLspheresfitsed together. rowan is a part of the anterior smaller sphere with a radius of about 7.8 mm and sclera is a part of the posterior larger sphere with a radius of about 12 mm.
• Poles The cat on the maximal convexities of the anterior and posterior curvatures of the eyeball is called the anterior and posterior pole, respectively.
• Equator of the eyeball lies at the mid plane between the two poles (Fig. 1.2). Dimensions of an adult eyeball
• Anteroposterior diameter 24 mm
• Horizontal diameter 23.5 min
• Vertical diameter 23 mm
• Circumference 75 mm • Volume 6.5 ml. • Weight 7 gm Coats of the eyeball The eyeball comprises three enatc- rioter (fihmi is coat), middle (vascular coat) and inner (nen(aus coat). 1. Fibrous coat. It is a dense strong wall which protects the intraocular contents.
Anterior 1/6th of this litmus coat is transparent and is called cornea. Posterior 5/6th !vague part is called sclera. Cornea is set into the sclera like a watch glass. lusstAn of the cornea and sclva is called limbus. Conjunctiva is firmly attached at the Embus. 2. Vascular coat (neat tissue). It supplies nutrition to die cal iuus stt mimes of the eyeball. It consists of three pans, from anterior to posterior, which are: ids, ciliary hady and chnroid. 3. Nervous coat (retina). It is concerned with visual functions and projects to visual cortex through the visual pathway. Segments and chambers of the eyeball The eyeball can be divided into two segments: anterior and posterior. I. Antenorsegment. It includes crystalline lens (which is suspended from the ciliary body by zonules) and structures anterior to it, viz., iris, cornea and two aqueous humour-filled spaces: anterior and posterior chambers.
■ Anterior chamber. It is bounded anteriorly by the backotcornea, and posteriorlyby the anterior surface Wilda and pattofciliatvhotly Tile milletIra chamber is about 24ggiuggpp in the centre in normal adults. It is slightlyshallower in hypernetropes and deeper in myopes, but is almost equal in the two eyes of the same individual. It contains about 0.25 niL of the aqueous humour. It communicates with posterior chamber through the pupil.
■ Posterior chamber. It is atria npilar spare containing 0 00 ml a atimmm humour It Is himorlettanierigrly by the poAlgaqsaggaigatrand part of ciliary body, pouysigth,hy ibtirritalline lens and its zonules, andlgtpallyjwbirjUggusit.