LACHRYMAL APPARATUS. 1477 



Glaucoma is a disease due to excessive intraocular tension which, unless re- 

 lieved, progressively increases until the eye is destroyed, and which almost always 

 involves the other eye. The abnormal tension is the result of disturbance in the 

 outflow of the intraocular fluid. This fluid is an exudation from the blood-vessels of 

 the ciliary body. From the posterior chamber the fluid passes through the pupil to 

 the anterior chamber. It then escapes in the angle formed by the iris and cornea 

 by passing through the lymph-spaces in the ligamentum pectinatum and by diffusion 

 reaches the canal of Schlemm. Thence it passes out by the anterior ciliary 

 veins. Obstruction in the path of this current occurs usually either in the lymph- 

 channels of this region, or at the pupil from adhesion of the whole pupillary margin 

 to the lens, or from occlusion of the pupil by inflammatory exudate, in iritis. 



Iridectomy frequently gives relief in both varieties ; in the former by opening 

 up the lymph-spaces near the corneal angle of the anterior chamber, the incisions 

 being carried well into this angle ; in the latter by making a new opening for the 

 current between the posterior and anterior chambers. 



The symptoms, like the cause, may be explained largely upon an anatomical 

 basis. The venae vorticosse pass obliquely through the sclerotic and are therefore 

 compressed and obstructed by the distension. Their blood is then compelled to 

 escape through the anterior ciliary veins, which penetrate the sclerotic more at a 

 right angle, and are consequently distended. CEdema of the cornea results causing 

 a superficial haziness. The cornea is insensitive from paralysis of the anterior ciliary 

 nerves. Usually the anterior chamber is shallow because the lens and iris are pushed 

 forward by the obstructed fluid behind, and the ciliary nerves being paralyzed the 

 pupil is dilated and immobile, giving a staring expression. The optic disc is at first 

 hyperaemic, and is consequently markedly depressed from the intraocular tension, 

 giving rise to one of the most important symptoms, pathological cupping of the disc, 

 or the glaucomatous cup. The great pain in glaucoma is due to compression of the 

 sensory nerves of the ciliary body and iris against the unyielding sclera. The 

 distended retinal veins can be seen through the ophthalmoscope. 



A condition analogous to glaucoma, hydrophthalmos, occurs in children, and is 

 either congenital or acquired very early in life. Unless relieved it almost always 

 produces blindness. 



THE LACHRYMAL APPARATUS. 



The lachrymal apparatus consists of the gland secreting the tears, situated in the 

 anterior and outer portion of the orbital cavity, and the system of canals by which 

 the tears are conveyed from the mesial portion of the conjunctival sac to the inferior 

 nasal meatus. 



The lachrymal gland (glandula lacrimalis), resembling in shape and size a 

 small almond, consists of two fairly distinct parts the superior orbital portion and the 

 inferior palpebral or accessory portion. The former occupies the fossa lacrimalis in 

 the frontal bone and is the larger portion. It measures 20 mm. in length, 12 mm. 

 in breadth and reaches from the edge of the superior palpebral muscle, along the 

 upper margin of the orbit to the suture between the frontal and malar bones. The 

 upper convex border is attached to the periosteum of the fossa by means of a number 

 of bundles of connective tissue, which are inserted into its capsule. Below, it rests 

 upon a fascial arch, which runs from the trochlea to the fronto-malar suture. 



The lower or palpebral portion of the gland, glandula lacrimalis inferior, is 

 somewhat smaller than the upper and separated from the latter by the fascial 

 expansion already mentioned. Its lower concave surface rests upon the fornix of 

 the conjunctiva, extending laterally almost to the outer canthus. 



The ducts from both portions of the gland are exceedingly fine, those from the 

 upper portion, from three to six in number, passing downward through the inferior 

 portion. Some of the ducts from the lower gland join those coming from above ; 

 others run independently, in all about a dozen ducts opening into the conjunctival 

 sac along a line just in front of the fornix. In structure the glands correspond to 

 the tubo-alveolar type, and resemble the serous glands in their general character. 

 The acini of the lower portion are separated by robust septa of connective tissue, 

 which contain considerable lymphoid tissue. 



