54 SURGICAL APPLIED ANATOMY. [Chap. iv. 



considerable. The symptoms of glaucoma are all 

 explained by the effects of the abnormal tension. Thus, 

 the ciliary nerves are compressed against the unyield- 

 ing sclerotic, and give rise to intense pain, while the 

 disturbance in their function shows itself in the fixed 

 and dilated pupil and in the anaesthetic cornea. 

 Perhaps the first parts to suffer from compression are 

 the retinal blood-vessels, and the effect upon them will 

 be most obvious at the periphery of the retina, i.e., 

 at the extreme limit of the retinal circulation. Hence 

 follows that gradually narrowing of the visual field 

 which is constant in glaucoma, while the pressure 

 upon the optic nerve produces those flashes of light 

 and other spectra which occur in the disease. The 

 weakest part of the sclerotic is at the disc at the 

 lamina cribrosa. This part rapidly yields under the 

 pressure, and so produces the " glaucomatous cup." 

 Pressure in the opposite direction pushes the lens 

 forward, and thus narrows the anterior chamber ; 

 while the general interference with the ocular circula- 

 tion is shown in the distended vessels that appear 

 upon the globe. 



The eyelids. The skin over the eyelids is ex- 

 tremely thin and delicate, and shows readily through 

 its substance any extravasation of blood that may 

 form beneath it. Its laxity, moreover, renders it very 

 well adapted for certain plastic operations that are 

 performed upon the part. Its loose attachments 

 cause it to be readily influenced by traction, and the 

 shrinking of cicatrices below the lower lid is very apt 

 to draw that fold away from the globe, and so produce 

 the condition of eversion of the lid known as ectropion. 

 The contraction of the conjunctiva after inflammatory 

 conditions, or after it has been subjected to destructive 

 agencies, is prone, on the other hand, to curl either lid 

 inwards towards the globe, and to thus produce entro- 

 pion. The lids present many transverse folds ; one of 



