Diseases of the External Senses;
including vision, hearing, smell, taste; to these we shall add the diseases of the voice and speech; obstructed deglutition; sterility, and morbid irritability of the generative organs. The derangement of those delicate and precious senses through which we derive such supreme delight; through whose avenues are conveyed into man the first rudiments of all his variegated ideas and knowledge, are important objects of medical scrutiny; notwithstanding very few from these causes are precipitated into the crater of mortality. I could, however, have wished to ascertain from registers, in conformity with my general plan, the proportion of cured and incurable; and especially the average of blind in a community.
Vision.
The principal diseases may be comprehended under opthalmia, fistula-lachrymalis, gutta-serena, cataract, specks on the cornea. I exclude some other natural defects, rather than diseases, such as myops, presbyops; for the cure of which the optician is the best physician.
Opthalmy, or inflammation of the eyes is a frequent complaint: it may be in the exterior membranes of the globe, or in the edges of the eye-lids; or may be a complication of both; it may be in one, or in both eyes; it may be general, partial, external, internal, temporary, chronic, idiopathick, symptomatick: of all which species there are various gradations. In this local malady there is commonly little or no fever; but heat, pain, redness, and inflammation; the vessels of the eyes seem gorged with blood; the anterior portion of the tunica sclerotica, and the conjunctiva, resemble a scarlet cloth, with impediment in vision, intolerance of light, lachrymation. In the inflammation of the cartilaginous ring of the eye-lids or tarsus, there is frequently some remains of small ulcerations in the sebaceous glands. The external is by far the most frequent form of opthalmy; and, under discreet management, is attended with trifling danger: sometimes, however, it is followed by specks on the cornea, or callosity, and blindness; and violent inflammation has extended to the interior parts of the eyes and retina. In the internal inflammation of the choroid and retina, no redness is perceptible externally; but there is excruciating pain, headach, intolerance of light, restlessness, often delirium, in a few instances, insanity: and if not relieved in the course of fourteen days, there is danger of incurable blindness.
Fistula lachrymalis. In this partial inflammation affecting the lachrymal sac and ducts, and obstructing the descent of the tears, or superfluous moisture of the eyes into the nose, this fluid necessarily trickles down the cheeks, and the eye is overflowed with water: on pressure of the internal angle and puncta lachrymalia, there is a discharge of glareous serum, by which the eye-lids, during sleep, are glewed together. The degrees of inflammation and obstruction are various. In the inveterate stages it may terminate in abscess, ulcers, and caries of the contiguous nasal bone.
Gutta-serena, amaurosis; in one or in both eyes, and in various gradations, from obscure vision to cheerless tenebrosity. To a spectator the eyes appear nearly as in health, only that the pupil is dilated and inanimate; the retina insensible to the rays of light, and the iris mute, without corresponding contraction or enlargement: a physiognomist might say, there are no sensitive emanations or magnetick rays emitted through this mental mirror. It attacks suddenly or gradually, and sometimes intermits; but in general it is chronic, and always dangerous; often irremediable: sometimes it is accompanied with headach in the anterior part over the eye-brows.
Cataract may affect one eye, but in general both: it arises from disease or opacity of the crystalline lens obstructing the visual rays in their course to the retina: the consistence and colour of the lens is various, white, pearl, green, yellow; and from these the oculist forms his prognostick: in couching the eye the pearl-coloured is preferred: the white is too soft; the green and yellow incurable; as is also that species wherein the strongest rays of light excite no contraction of the pupil. Cataracts in general are gradual in their formation; weeks, months.
The predisposing and occasional causes of injured vision and of opthalmy, external violence and blows; sudden suppression of perspiration; extraneous bodies or acrids admitted within the eye-lids; acrid metallic fumes, and noxious exhalations; long exposure to confined smoke, especially from wood fires; smoky houses and cottages; acrid collyria; epidemick state of the air, and infection; long continuance of wet weather; long exposure of the eyes to the rays of strong light, to snow, or luminous objects; cold streams of air; suppression of salutary evacuations, or cutaneous eruptions, and of chronic ulcers; acrimony of the blood; interruption to the free return of blood from the head; frequent intoxication: nocturnal studies; long want of sleep, grief, tears; small tubercles within the eye-lids; ulcerated eye-lids; variolous: morbillous; scrophulous; venereal; erysipelatous; rheumatick; catarrhal; intermittent; herpes; cancerous. Of fistula-lachrymalis, inflammation of the lachrymal sac, or ducts. Of gutta-serena, plethora, distention of the vessels of the retina; palsy of the optick nerves, general or partial; diseases of the brain, or of the retina; profuse and suppressed evacuations; excess of venery; chronic headach; ebriety; cachexy; venereal; intermittent; symptomatick in the irregular gout, apoplexy, &c. Of the cataract, opacity of the crystalline lens. The general causes of injured vision, exclusive of opthalmy, may be briefly enumerated; and are long attention to minute objects; weakness of the power to contract the pupil; faults of the globe; defect of the aqueous humour, its impurity or density; opacity of the lens, or of the vitreous humour; the retina callous or too sensible; faults of the optic nerves; contraction, concretion, flaccidity of the pupil; gibbous or convex lens, or too near and flat; dropsical eye; spasm, or palsy of the ocular muscles; diseases and ulcerations of the eye-lids and ciliary glands; ulcers and fistula, specks and scars, in the cornea; films growing from the angle of the eye; the eye-lids inverted, elongated, concreted; various diseases of the brain from internal or external causes.