THE EYELIDS AND CONJUNCTIVA. 1441 



the pupil contracts. There will be some drooping of the upper lid due to paralysis 

 of the superior palpebral muscle of Miiller which passes from the under surface of the 

 levator palpebrae muscle to the upper margin of the upper tarsal cartilage, and is 

 supplied by the cervical sympathetic. There will be slight enophthalmos from paral- 

 ysis of a thin layer of unstriped muscle passing across the spheno-maxillary fissure 

 (orbitalis muscle of Miiller). 



The normal pupil will contract for accommodation and convergence to near 

 objects and from stimulation by a bright light. An Argyll- Robertson pupil is one 

 which does not react, either directly or indirectly (consensually) to the influence of 

 light, but contracts promptly on convergence of the visual axes. The exact situation 

 of the lesion is uncertain ; it may involve the fibres which pass from the proximal 

 end of the optic nerve to the oculomotor nuclei ; it may be nuclear in its position ; 

 or it may be in the spinal end of the floor of the fourth ventricle. 



Owing to the relatively large amount of fat and loose connective tissue in the 

 orbit, infection may lead to an extensive orbital abscess, so that an early opening is 

 imperative to prevent disturbance or loss of sight. The muscles may be impaired 

 by the process, leading to the lessened mobility of the eye. The optic nerve may 

 be inflamed with resulting atrophy and permanent impairment of sight, and the other 

 ocular nerves may also be paralyzed. From the exophthalmos the optic nerve may 

 be stretched, although the degree of stretching permitted without disturbing sight is 

 often remarkable. Pus may enter the cranial cavity through the optic foramen, and 

 set up a meningitis or a brain abscess. 



Injuries of the orbital tissues are usually the result of penetration by foreign 

 bodies. The eye has been pried out by the finger, or thumb, on the outer side by 

 insane people, or in fights, the finger being readily forced back of the equator of 

 the globe. There are cases in which the eye has been replaced and vision regained 

 after such accidents, although it is usually lost. 



Fracture of the bony wall of the orbit ordinarily leads to hemorrhage into the 

 soft tissues, showing later under the conjunctiva of the ball (subconjunctival ecchy- 

 mosis). If the neighboring air cavities, as the ethmoidal and sphenoidal sinuses, are 

 involved, emphysema of the orbit may result. The exophthalmos from air behind 

 the eye, can be reduced by backward pressure, the air being forced back into the air 

 sinuses. A collection of blood would not disappear by such pressure. In cases of 

 emphysema the patient should be instructed not to blow the nose, as by that act 

 additional air is forced into the orbit. 



Tumors of the orbit are comparatively common. They may begin in the adja- 

 cent cavities and invade the orbit secondarily. The most important symptom in all 

 cases is exophthalmos. Pain and paralysis from pressure on the nerves, and con- 

 gestion and edema of the lids from pressure on the veins frequently occur. 



THE EYELIDS AND CONJUNCTIVA. 



The eyelids (palpebrae) are two movable folds of integument an upper 

 and a lower strengthened along their free margins by a lamina of dense fibrous 

 tissue, the tarsal plate, and modified on their deeper aspect so that this surface 

 resembles a mucous membrane, the conjunctiva. When in apposition or closed they 

 completely cover the orbital entrance and the eyeball ; at other times, when open, 

 they cover the periphery of the orbit but allow a variable portion of the anterior part 

 of the eye to remain exposed. 



The. palpebral fissure (rima palpebrarum) is bounded, above and below, by 

 the free margins of the lids and at the ends, where the lids join, by two fibrous 

 bands, the median and lateral palpebral ligaments. Of these the inner and 

 stouter springs from the nasal process of the superior maxillary bone and the narrow 

 outer one is attached to the malar bone. The palpebral fissure is an oval cleft of 

 not quite symmetrical form, since the curvature of its upper boundary is somewhat 

 greater than that of the lower ; further, the points marking the summit of the 

 two curves neither correspond to the middle of the arches nor lie opposite each 

 other, that of the upper arch lying nearer the mid-line and that of the lower nearer 

 the lateral wall. Neither is the palpebral fissure strictly horizontal, since the inner 



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