1847] Management of Presbyopia. 199 learn to use either eye indifferently, instead of always trusting to one, although we almost instinctively apply the right eye to a telescope or microscope."-P. 118. Presbyopia-Far-Sightedness-Aged-sight. Although the name of this condition of the eye is (peobus, old) significative of the fact of its usually forming one of the first indications of the approach of age, it is by no means confined to any period of life-many eyes being originally presbyopic as others are myopic. We need not give the general description of the symptoms of the condition as furnished by M. Sichel and Mr. Cooper, nor the marks distinguishing it from cataract and amaurosis set down by the latter; merely observing, in respect to these last, that we are surprised Mr. Cooper dwells upon the diagnostic signs derived from general symptoms, when so simple a one as the trial of the effect of a convex lens would, in the majority of cases, dissipate all doubts. M. Sichel has some valuable observations upon this affection. He dwells much upon the hygienic precautions necessary to be observed by the presbyop. Thus, when engaged in writing, reading, or minute occupations of any kind, he should always place the object as distantly as possible from his eyes, consistently with distinct vision. Having by experiment ascertained what this point really is, he should in future, during all assiduous labours, carefully observe it. In less trying occupations he may exercise his eyes at less distances, so as to accustom them to perceive within their normal focus. In both cases, he must from time to time interrupt his labours, and direct his eyes to the most distant objects within the sphere of his vision. After five or six minutes' intense exertion of the eyes on minute objects, he should cast them towards the walls of the apartment or out of the window. An interruption of this kind of only a few seconds preserves the power of accommodation of the eye, and prevents the enfeeblement of the sight; and in this way M. Sichel has repeatedly seen a commencing amblyopia dissipated. The interruption is very slight, and by habit becomes almost imperceptible. The more closely these directions are observed, the longer will the eyes be preserved without the necessity of resorting to glasses; and the minuter the occupation the more necessary are the precautions. If possible, people who are presbyopic should not choose occupations necessitating an exertion of the eyes on minute objects; and many dress-makers, shoe-makers, tailors, &c., would do much better as domestic servants. M. Sichel particularly alludes to the injury which is inflicted upon the eyes of children by allowing them to bend over their tasks, so as to bring their eyes close to the written characters, instead of obliging them to hold themselves erect, taking care that the letters of the words are sufficiently large for them. Degree of Light required in Presbyopia.-For the purpose of exact vision, and especially for near objects, the presbyopic eye requires a bright light, so that half-lit apartments are very injurious to it. Lamps furnish a much better and more equable light than candles. Coloured glasses, which have been erroneously termed "preservers," should only be employed when the eye is temporarily exposed to the reflection of some exceedingly vivid light. In other circumstances they are very hurtful, by accustoming the eye to artificial darkness, and covering everything with a blackish tint, which prevents objects being accurately distinguished without effort. In this way, amblyopia and photophobia may be induced; and many such cases have been promptly relieved by the prompt removal of the patient from an obscurity to which he had been erroneously consigned. When exposed to very bright reflection, glasses of a light greyish-blue are the most suitable. Glasses in Presbyopia.-It is usually about 40 that the presbyopic eye requires the aid of spectacles. While the sight for distant objects may be even improved, that for near ones, especially if not well lighted, or removed to a distance, becomes impaired. The fixing the eye is likewise painful and fatiguing, and if the irritation go on, it may lead to amblyopia. Before symptoms reach this point we must have resort to glasses, employing them at first only during artificial light or minute occupations. The rules before-mentioned are still to be observed, and especially that of holding objects as distantly as possible from the eyes consistently with distinct vision. In respect to the number of the glass which should be commenced with, it is an error to suppose that this is always the same for the same age, and opticians generally recommend a far too high power, and increase this far too suddenly. Even excellent writers upon affections of the eyes fall into the same error; and thus Mackenzie recommends a 36-inch focus for persons of 40 years of age, and a 30 for those of 45. As the result of numerous experiments, M. Sichel commences with a 72-inch, which in general answers very well for persons who have not yet employed glasses, and who have not delayed resorting to them too long. Frequently, however, and especially in persons younger than 40, 80-inch or 96-inch answer excellently for a long period. In trying spectacles we should be able to discover objects distinctly (but not magnified) at a little less distance than we see them imperfectly without them. All glasses, more or less, destroy the accommodating power of the eye, and that in proportion as they are strong; so that we must be content with a power just sufficient, increase it only by almost insensible gradations, and from time to time dispense with it and fix the, eye on some distant object, and even occasionally employ the unassisted eye for a short time on minute objects held at a distance. In the earliest transitions of size the actual differences are very slight, as from 96 to 84 and 72-inch; but, as we descend, these become more marked, and to prevent their being too abrupt, M. S. employs 66 and 54-inch, recommending the patient to retain each glass as long as possible, and decrease it only six inches at a time. It is an error to say that a change of glasses is always necessary. It often becomes so only because too high numbers have been begun with, and cautions neglected; so that, when we hear a patient complain of his glasses being ineffectual, we must examine whether he has not originally used too powerful ones, and thus induced amblyopia. By employing this slowly graduated scale, M. S. rarely finds a lower number than 48 required; while, when 48 is begun with, a lower one than 36 never succeeds. In very young persons, or where amblyopia complicates the presbyopia, we should never commence with lower than 96, and keep at 80 as long as possible. On Amblyopia (Defective Vision) produced in Presbyopia by the too 1847] On Amblyopia resulting from Presbyopia. 201 assiduous Employment of the Naked Eye.-If a presbyop continues to employ his eyes injudiciously, a condition very difficult to distinguish from incipient amaurosis may be produced. This is presbyopia amblyopia, or amblyopia resulting from presbyopia. The visual disturbance is very great, especially with artificial light or in obscure places, and is characterised by its disappearance under the use of convex glasses. If neglected, an asthenic form of amaurosis results. This species of amblyopia is especially found in engravers, miniature-painters, watch-makers, literary men, dress-makers, &c.; and more particularly in those persons who, having lived in the country, and been accustomed to long sight, afterwards have their eyes suddenly employed on minute objects. It is likewise especially found in those in whom a constitutional debility of the retina is conjoined to presbyopia. In presbyopia, amblyopia is generally the effect of excessive exertion of the eye, while in myopia it usually results from constitutional causes, such as cerebro-ocular congestion, abdominal plethora, &c. This condition has been described by various authors under different names (by Mackenzie, as Asthænopia or weakness of sight, but its true nature has not been appreciated by them, in consequence of the presbyopia having been overlooked. In treating this affection, M. Sichel recommends total or partial abstinence from minute employment, or, at all events, its interruption from every two to ten minutes, according to the gravity of the case, in order that the eyes may be directed to distant objects-applying to them also spirituous, or, if the case is old, stimulating lotions. In this last circumstance, too, blistering the brow and temples, and the use of convex glasses, are indicated. Even when amaurosis has commenced, these measures will usually triumph over it, employing in this case therapeutical means more energetically and glasses more sparingly. As to these last, when the eyes have been sufficiently rested from employment and amelioration has commenced, we may allow the patient several times a day to employ, for a few minutes, glasses strong enough to admit of reading without any fatigue, or without the necessity of looking too close. As the case improves, their refractive power may be diminished. We may here cite a case of temporary presbyopia quoted by Mr. Cooper. "On the 17th of April 1840, a boy, eleven years of age, was brought to Edinburgh from the country for the opinion of the late Dr. James Hunter. Fifteen days previously he was at school in perfect health, when one evening the discovery was made that he could not read common type, nor distinguish accurately any very small or near object. There was neither pain nor symptom of disease in either eye, but the vision of each was equally affected. The general health of the lad was unimpaired, and he had not received any injury either of the eyes or any other part. During the two following days the sight became worse, but after that it had remained stationary. Excepting the administration of some purgatives no treatment had been adopted. Previous to the attack his sight had been extremely good, and he had not been troubled with worms or other ailment since infancy. The eyes, upon examination, appeared perfectly healthy, and the only complaint made was the inability to read common print, or to see minute or near objects; distant objects, he thought, were as distinct as ever (although it was subsequently ascertained that his distant vision was slightly affected). Large type was best seen at 11 inches from the eye; small print could not be read at all; distant objects were ascertained pretty accurately; and the power of the two eyes seemed equal. Concave glasses rendered his sight much less distinct, convex glasses improved it much. Dr. Hunter strictly prohibited the use of spectacles, and prescribed a combination of anthelmintic and tonic treatment, with spare diet and plenty of exercise in the open air. No worms made their appearance. The presbyopia continued until the end of May, when an amendment was perceived which increased daily, and in about ten days the sight was perfectly restored." P. 89. The Employment of Glasses in Amaurosis.-Charlatans have long been in the habit of employing convex glasses in amaurosis, and those practitioners who have followed their example have explained the occasional benefit thence resulting by the excitement of an asthenic retina; but, according to M. Sichel's views, they are only useful when the amaurosis has followed presbyopia. In these cases, even, very convex glasses should not be employed before fully trying the effect of feebler ones. He has long been aware of the modifications which the difference in the length of normal vision impresses on the symptoms. Thus, in the condition of amblyopia from presbyopia, slightly voluminous objects are best seen when held at more or less distance the sight at a distance remaining good although impaired for near objects. In such cases, sight is notably improved by convex glasses. After a long period, however, when the patient's sight becomes shortened to a great extent, glasses are of no use, and the amaurosis is incurable. In myopia the sight, while enfeebling also at a far earlier period, becomes shorter, and convex glasses do not facilitate vision, unless placed very near the eye so as to act as magnifying-glasses, at the same time stimulating, and eventually injuring the retina. Thus, we would expect, as in fact is the case, that, in amaurosis from presbyopia, glasses would prove useful, and the more so as its origin is local-i. produced by fatigue of the organ of vision. Hence they frequently prove of service both in the treatment and the diagnosis of the affection. Strong glasses must not be employed if the case is not a very old one, the presbyopia excessive, the foci of the eyes unequal, or the patient unable to suspend his occupations. It is doubtful if any case of cure of myopia by these means has ever occurred. e. There is a variety of presbyotic amblyopia, however, from which patients derive no benefit from glasses, and on enquiry such persons will have been found to have employed their unprotected eyes long after defective vision had manifested itself. The eye has thus been forced to accommodate itself to minute objects until positively unable to continue to do so. In this case the retina must be allowed to recover itself by repose, and by frequent exercise on large and distant objects, after which the 96-inch focus may be employed. Often, however, stronger glasses will be required, the patient by exertion of the unassisted eye having contracted an acquired myopia. Although this form of amblyopia is usually of slow occurrence, it occasionally comes on rapidly, if the eyes are sedulously employed upon smaller objects than they are accustomed to. This is the case with some children who are too early employed in reading, sewing, &c. Presbyopic amblyopia generally occurs without complications, but it may exist in conjunction with cerebro-ocular congestion, dysmenorrhea, constipation, &c.-conditions which much favour the occurrence of amblyopia in presbyopia. These complications must be removed before recurrence is had to glasses 1847] Consequences of Presbyopia. 203 or local stimuli. It may also be associated with various other diseased conditions of the eye, often rendering their diagnosis very obscure. The complication of presbyopia with conjunctivitis has frequently given rise to the supposition of an amblyopia which has had no existence in fact. Some of the Consequences of Presbyopia.-Among these M. Sichel mentions (1) Ocular Neuralgia as of frequent occurrence. At first occuring only after long exertion of the eyes, it eventually comes on as soon as this is commenced. Any exertion whatever indeed of the eye induces pain, and this may occur when it is quite at rest; and the affection may become complicated with rheumatism or cerebro-ocular congestion. At an early stage, rest and appropriate glasses suffice for the treatment Later, absolute rest is essential, opiates being given internally or veratria applied to the brow-the complications being properly regarded. But all measures are useless unless first absolute rest, and then only the gradual use of the eye, be observed. Both eyes are usually affected, and, when this is not the case, we should examine them and see whether the affection do not arise from their foci being unequal. In rare instances it is induced by the use of strong glasses. (2), Mydriodapsia, or Musca Volitantes.-These almost always arise from a rash use of the organ. In presbyopia they are found when the naked eye is used, or when one eye is fatigued by an inequality of focus. Common as is this affection from the abuse of glasses in myopia, it is rarely produced by the use of convex glasses in presbyopia. The muscæ volitantes must, in regard to prognosis, be carefully distinguished from the fixed darkened spot called scotoma, the sure forerunner of amaurosis. (3), On acquired Myopia, or Presbyopia converted into Myopia.-As the presbyop can only apply his eye in working by forcibly subjecting it to a too short focal distance, we can easily see how assiduous labour under these circumstances may eventually destroy the accommodating power of the eye for the observation of distant objects, and so shorten the focal distance as to induce a secondary myopia. The continuance of such employment tends only to increase it, to which other circumstances also sometimes contribute. Thus, in ignorance of the determining cause, to relieve his uneasiness during the employment of the eye, the person may be recommended to use a concave glass, which only aggravates his condition. We may observe acquired myopia in its simple form; unaccompanied by any weakness of vision-the person having become myopic from the mere exertion of his eyes. This affection comes on slowly, and is rather found in persons who have acquired the bad habit of placing objects too near their eyes, especially by stooping at their work, than in those who have too much employed them. The majority of myopia are so induced. In this simple form the organ of vision is perfect, providing the object be placed at an appropriate distance. When it is not of long-standing, it suffices to gradually increase the distance of the objects from the eyes, and exercises these upon distant ones at frequently-recurring intervals. The use of concave glasses is to be rigorously prohibited; nor should convex ones be employed when there is no complication of amblyopia, the original presbyopia is not excessive, or the |