Complete Text (Part 11)

condition is divided into two classes, termed homonymous and heteronymous. In homonymous hemianopsia one-half of the field of vision on corresponding sides is abol- ished. In heteronymous hemianop- sia the median, temporal, upper, or lower portions of the fields are abol- ished. The first form owes its pro- duction to a defect of the transmit- ting apparatus in the optic tract of one side or of the radiating fibres in the occipital lobe, or to a disease-pro- cess destroying the function of the visual area in the cortex of the brain, which is located in the occipital lobe in the region of the angular gyrus and cuneus. (See Fig. 13. ) CO OD b*a Diagram of Decussation of the Optic Tracts (after Charcot): T, senri-decus- sation in the chiasma ; TQ, decussation of fibres posterior to the external ge- niculate bodies (CG); a'b, fibres which do not decussate in the chiasma ; b'a', fibres coming from the right eye, and coming together in the left hemisphere (LOG) ; K, lesion of the left optic tract, producing right lateral hemianopsia ; a, lesion of the left hemisphere (LOG), producing crossed amblyopia (right eye) ; T, lesion producing temporal he- mianopsia ; NjN, lesion producing nasal hemianopsia. What is the cause of nasal and temporal hemianopsia ? Nasal hemianopsia can only be caused by lesion affecting the outer angles of the optic chiasm, compro- mising the nerve-fibres at these points and causing blindness of the temporal halves of each retina. Temporal hemianopsia can be caused only by a lesion affecting the optic chiasm in its anterior or posterior angles, causing blindness of the nasal half of the retina. Defects of the upper or lower halves of the fields of vision in both eyes at the same time are extremelv rare. SYMPATHETIC OPHTHALMIA. 83 What is the line of division between the seeing and blind halves of the fields of vision in hemianopsia? In lateral hemianopsia the dividing-line usually passes perfectly per- pendicularly through the line of fixation, deviating usually toward the blind side about 3° at the point of most acute vision. "What is the field of fixation ? It is a term given to the angular deviation of the eyes which can be produced by the muscles of the eye, enabling the eyes to fix any point in common without double vision. This can be determined by use of the perimeter. Landolt gives the following table of limitation of the field of fixation, arrived at after many tests : Outward, 45° ; downward, 50°; inward, 45°; upward, 43°. A knowledge of the normal field of fixation is of value in determining muscular defects that may exist. What is amaurosis? It is a term signifying loss of vision, and was applied by the old writers to conditions where the cause of loss of vision was obscure. The term at present is used but little. What is meant by the term " amblyopia " ? It signifies a diminution in visual acuteness less in degree than that implied by the term ' ' amaurosis. " It is at present applied to but few conditions. The partial loss of vision which results from confirmed squint is termed amblyopia, and, since it is believed by some oculists to be due to non-use of the eyes, it is termed amblyopia from non-use. What is metamorphopsia ? A condition in which there is distortion of images either from irreg- ular astigmatism or from disease-processes affecting the retina. What is micropsia? An unnatural diminution in the size of the image, due to disease-con- ditions which cause a spreading of the rods and cones. What is megalopsia? The opposite of micropsia : objects appear to be abnormally large. SYMPATHETIC OPHTHALMIA. Define sympathetic ophthalmia. It is a diseased condition produced in a previously healthy eye through the agency of a disease-process which has partly or totally destroyed the fellow-eye. It frequently results from injury to one eye, whereby infec- tious material has been carried into the eye and has there setup an inflammatory process, usually of the nature of an irido-cyclitis. Injuries in the region of the ciliary body are most prone to produce sympathetic 84 THE EYE. ophthalmia, but infectious wounds occurring in any part of the globe may serve to bring about this condition. Suppurative diseases of the eye which result in panophthalmitis seldom produce sympathetic oph- thalmia. Operations for iridectomy and for the extraction of cataract sometimes lead to this disease. The eye first involved is termed the exciting eye, the other the sympathizing eye. What are the symptoms of sympathetic ophthalmia ? The patient first experiences slight difficulty in the use of the eyes, a little pain in the region of the temple, and dimness of vision. The pain gradually increases, dimness of vision becomes more marked, and total blindness often ensues. The first objective sign is often slight peri- corneal injection just below the cornea. Slight pressure in the ciliary region above produces pain. On examining the optic disk it is, in a number of cases, found to be in a condition of commencing papillitis. In the greater number of cases the first evidence of inflammation in the interior of the eye is visible in the his, which is sometimes muddy in appearance ; the free margin of the pupil becomes uneven, and poste- rior synechias form at an early date. With the formation of posterior synechias there is also the throwing out of plastic exudation, the aqueous becomes slightly turbid, and the iris is swollen and thrown into folds. At this stage the fundus of the eye cannot be seen because of the opacities in the aqueous and vitreous humors. The pericorneal injection becomes very marked, pain increases, and the disease goes on to the production of permanent blindness. What is the theory of reproduction of sympathetic ophthalmia ? Older writers were of the opinion that the inflammation took place through the medium of the ciliary nerves, and that it was purely a sym- pathetic process. Recently it has been thought that the infectious ma- terial reaches the sound eye through the medium of the optic nerve- sheaths, and that it is in the nature of a micro-organism. While the theory of infection is the must plausible, it is not yet proven. What is the treatment of sympathetic ophthalmia ? In the greater number of cases, particularly if all vision is lost in the exciting eye, it should be removed. However, in cases where the inflam- mation is well advanced in the sympathizing eye. and some vision remains in the exciting eye. it may be well to allow the exciting eye to remain, as the amount of vision to be obtained in the sympathizing eye cannot be determined with certainty, and the best vision may remain in the eye from which the sympathetic trouble was derived. In addition to enu- cleating the exciting eye. the local application of atropine and the use of hot applications should be commenced early. It is often found that the free administration of the iodide of potash with mercury is very valuable. Patients should be given perfect rest in bed and the eye should be protected from light. GLAUCOMA. 85 What is the duration of sympathetic ophthalmia ? It usually runs a long and tedious course. _ The prognosis is bad even when the case is taken in its early stage. In cases where total occlusion of the pupil has resulted from sympa- thetic ophthalmia some benefit may be derived by the formation of an artificial pupil. GLAUCOMA. What is glaucoma? A name given to a series of symptoms, most prominent among which is an increase in the tension of the globe. How are the different degrees of tension of the globe indicated ? They are indicated by the letter T, preceded by a plus sign when the tension is increased ; by a minus sign when the tension is decreased. The degrees of plus or minus tension are indicated by the numbers 1, 2, and 3 following the letter T. When the tension is normal the sign T N is employed ; when the increase in tension is perceptible and unmistak- able the sign + T 1 is employed ; when of stony hardness the tension is indicated by the sign -f- T 3. The degrees of tension below the normal corresponding to those just described as above the normal are indicated by corresponding figures under the minus sign. The tension is deter- mined by palpation with the fingers. What are the varieties of glaucoma ? They are comprised under two principal heads, primary and secondary. Primary glaucoma has reference to a condition of increase in the tension of the globe, originating in the eye itself without external influence. Secondary glaucoma is the term given to the same condition following an injury or some previous inflammatory process, or occurring as the result of lesions in other parts of the system, as in valvular lesions of the heart. What are the forms of primary glaucoma ? They are usually designated as simple, inflammatory, hemorrhagic, and fulminating or malignant. The term "absolute glaucoma" is applied to a condition where the disease has run its course and absolute blindness has resulted. What are the symptoms of simple glaucoma ? This form of the disease comes on very insidiously, and is usually first brought to the attention of the patient by partial failure of vision. It is unaccompanied by pain. The power of accommodation fails more rapidly in patients subject to this form of glaucoma than in the normal condition. The visual field becomes contracted nasally, the appearance of the^ eye changes but little, the veins in the anterior segment of the sclerotic become somewhat tortuous, and we sometimes notice a bluish 86 THE EYE. tinge of the sclerotic. On examining the interior of the eye with the ophthalmoscope we find that the optic disk is depressed ; the blood- vessels appear to be interrupted at its margin ; pulsation of the retinal arteries on the disk may be noticeable, but if not present may be readily excited by slight pressure on the globe exerted with the finger. The pupil is sluggish and may be slightly dilated. The anterior chamber and cornea often remain normal. What is inflammatory glaucoma?, In this form pain is a pronounced feature. The disease may be chronic in character with occasional exacerbations, during the intervals between which the patient may experience but little discomfort. Great dimness of vision exists during an acute attack, which is somewhat recovered from when the attack passes over. During the inflammation the ocular conjunctiva is congested, the pupil dilated and oval, the anterior chamber shallow, and the cornea hazy. The tension is increased usually to a marked degree. Examination with the ophthalmoscope is often impossible because of the haziness of the cornea and of the media. What are the symptoms of hemorrhagic glaucoma ? They resemble those of inflammatory glaucoma, except that in hemor- rhagic glaucoma there is escape of blood from the vessels of the iris, ciliary processes, and at times from the vessels of the retina and choroid. What are the symptoms of fulminating or malignant glaucoma ? They resemble those of inflammatory glaucoma, except that they are greatly intensified. The tension may reach -f- 3, and sight may be lost in twenty-four hours. What are the symptoms of secondary glaucoma ? They are usually those of inflammatory glaucoma. What are the symptoms of absolute glaucoma ? Total blindness, with increase of tension, with or without pain. What are the causes of glaucoma? Glaucoma is a disease peculiar to old age. Rare cases are on record of its occurrence in children, but the vast majority of the cases take place after the age of forty. It is very frequent in Hebrews, and is supposed to be due to consanguinity. It occurs in the rheumatic and gouty, and these diatheses seem to exert some causative influence. It most fre- quently occurs in hypermetrops, glaucoma in myopia being very rare. In probably every case the disease originates by interference with the escape of the intraocular fluids through the filtration angles of the eye. This may be brought about by a plugging up of the spaces, as sometimes occurs from a deposit of lymph in iritis, or it may be occasioned by a pressing forward of the root of the iris from an enlarged lens, or by sudden pressure against the lens from the vitreous chamber. Priestly THE LENS. 87 Smith is strongly of the opinion that the enlarged, flattened lens present in hypermetrops is chiefly instrumental in the production of primary glaucoma by pressure against the root of the iris, compromising the lymph- spaces at the iris angle.^ In secondary glaucoma, produced by injury to the eye, by a kerato-iritis, by hemorrhage from retinal vessels, as some- times occurs in hemorrhagic retinitis, or by rupture of the lens capsule, any or all of these causes act to compromise the iris angle and to pre- vent the free escape of intraocular fluids. What is the treatment of glaucoma ? It is medicinal and surgical. The medicinal treatment of glaucoma is best applied in primary glaucoma of the milder types. It consists in the use of warm applications and in the instillation of solutions of eserine or of pilocarpine in strength of from \ to 1 per cent. A valuable formula for eserine is the following: R. Eserin. sulph., gr. J ; Solution cocain. hydrochlorat. , 2 per cent., 7> ij. — M. Sig. Instilled into the eye two or three times daily. What is the operative treatment of glaucoma ? That which is found to give most satisfactory results is iridectomy. The iridectomy must be large, and it must be made so as to secure the removal of the iris as closely to its root as is possible. This is applicable in all cases of glaucoma, and should be done early in the disease. Also an operation known as sclerotomy, which consists in passing a Graefe knife through the sclerotic into the anterior chamber, making puncture and counter-puncture as deep in the iris angle as possible, including about one-fifth of its circumference, and cutting outward, leaving a small bridge of scleral tissue to prevent the wound from gaping. This operation, applicable only in the milder forms of glaucoma, is sometimes successful, but must usually be supplemented by an iridectomy. In absolute glau- coma, accompanied with pain, and in some forms of secondary glaucoma, enucleation must be resorted to. THE LENS. What is the crystalline lens of the eye ? It is a transparent, lens-shaped body suspended in the anterior portion of the globe immediately back of the iris. It measures from 9 to 10 mm. in its longest and from 4 to 5 mm. in its shortest diameter. It consists of a semi-solid substance confined in a thin capsule, and serves to focus on the retina rays of light which enter it through the pupil. What is the structure of the crystalline lens ? It is composed of a capsule and lens-substance proper. The capsule consists of a thin, homogeneous membrane which is lined on the posterior surface of its anterior half by epithelial cells from which the lens-fibres 88 THE EYE. are formed. Its posterior half consists simply of the thin homogeneous membrane. To the anterior and posterior portions near the equator are attached the fibres of the suspensory ligament. The lens substance proper is lamellated, the lamellae, which are arranged concentrically, being composed of a single layer pf lens-fibres placed side by side. The fibres and lamellae are joined by an inter-cemcnt substance. The spaces also give passage to lymph-streams which supply nutrition to the different parts of the lens. That portion of the lens formed before birth is com- monly known as the nucleus, that after birth the cortex. The lens-fibres are long and narrow, being larger at each end than in the centre, and are hexagonal on cross-section. The lamellae are arranged so that the ends of the fibres abut on each other in such a manner that a star- shaped figure is formed on the anterior and posterior aspect of the lens, the figure having the shape of an inverted A anteriorly, of an upright Y posteriorly. The lens rests in a fossa in the virteous humor. What is the suspensory ligament? It is a thin, fibrillated membrane which takes its origin from the ora serrata, from the cells of the pars ciliaris retinae, and from the inner layer of cells of the ciliary processes. These fibres pass downward and forward in the form of a membrane, dividing just before reaching the equator of the lens. A portion passes to, and is inserted into, the ante- rior capsule at about 2 mm. from the equator, and a portion passes to the posterior capsule and is inserted in it at about the same distance. The stronger attachment is to the anterior capsule. Some fibres pass through the triangular space which is known as Petit' s canal, and find their attachment to the capsule of the lens. The lens capsule is also known as the zonula of Zinn. It marks the anterior limit of the vitre- ous humor. What constitutes cataract? Cataract is an opacification of the crystalline lens or of its capsule. Fig. U. Nuclear Cataract : 1, section of lens, opacity densest at centre : 2, opacity as seen by trans- mitted light (ophthalmoscope mirror) with dilated pupil ; 3, opacity as seen by re- flected light (focal illumination). The pupil is supposed to be dilated by atropine. What are the most common forms of cataract ? Nuclear, cortical, zonular or lamellar, anterior polar, posterior polar, Morgagnian, mixed, congenital, and traumatic. THE LENS. 89 What is nuclear cataract? In certain forms of cataract the opacity first appears at the nucleus of the lens, and extends from the nucleus to the peripheral portions. What is cortical cataract? In this