A ccommodation 8 5 



known why ; it is not from intra-ocular pressure, for the signs of that 

 affection are wanting. The earliest symptom is astigmatism. 



The choroid is connected with the sclerotic by vessels and nerves, 

 and by delicate fibres which pass across the intervening lymph-space. 

 It is chiefly composed of blood-vessels, with pigment cells for absorbing 

 the diffused rays of light. The external set of vessels are the ciliary 

 arteries, and the venae vorticosas - tributaries of the ophthalmic vein ; 

 the inner coat being composed of an extremely fine network of capil- 

 laries. 



The ciliary processes, sixty or eighty in number, are continuous 

 posteriorly with the choroid, and intervene as a vascular, erectile fringe 

 between the ciliary muscle and the circumference of the lens. In 

 front they blend with the periphery of the iris. Their blood supply 

 is from the vessels of the choroid, and from the anterior ciliary 

 arteries. 



The ciliary muscle is a narrow circle of unstriped fibres which, 

 arising from the line of junction of the sclerotic and cornea, pass 

 backwards to be inserted into the neighbouring part of the choroid. 



Emmetropic (sound) eye ; parallel rays, a, a, come to focus on retina at b ; divergent rays, c, 

 would meet at focus, d, behind retina, but ' accommodation ' brings them to a focus at b. 



(DlXON.) 



Its action is to pull on the ciliary processes, and so to slacken the 

 suspensory ligament and the capsule of the lens, in order that the 

 elastic lens may again expand, and its convexity may be thus in- 

 creased for viewing near objects. Together with the other muscles 

 of accommodation, the internal, superior, and inferior recti, and the 

 sphincter fibres of the pupil, the ciliary muscle is under the control 

 of the third nerve. 



The muscular act is known as 'accommodation 5 ; it is associated 

 with contraction of the pupil, in order that the rays may pass through 

 the most convex, refracting part of the lens only. As the individual 

 can watch distant objects for a long while without tiring, his defect is 

 spoken of as ' long-sightedness.' But when reading small print his 

 eyes become bloodshot and tired, the fatigue of the ciliary muscle ex- 

 pressing itself, perhaps, as ' headache.' 



In the case of the person who is born with the antero-posterior axis 

 too short, the life of the ciliary muscle is one constant struggle to collect 

 and focus the divergent rays. It frequently breaks down in the task 



