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Accommodation demand for near work varies on changes of spectacle vertex distance. Equations relating ocular accommodation, spectacle vertex and working distance are derived. These equations show that increase in vertex distance will reduce demand for ocular accommodation in some conditions only.

A team from the University of Auckland conducted an assessment of vision needs in Tonga in August 1981. A total of 667 people was examined with a mean age of 50.6 years. The vast majority (91.6%) had no spectacle correction for either distance or near. The onset of presbyopia appeared to occur at an earlier age than in European societies and the majority of spectacle prescriptions ordered (77.4%) were for near work. A high incidence of pterygium (23.2%) was detected by the team.

Data from 96 veterans who had been using a closed circuit television (CCTV) for at least 2 years are presented. Most patients (87%) reported continuing use of the CCTV and demonstrated their proficiency in its use. Fifty percent of all patients used an optical aid, as well as a CCTV for near work. These patients did not differ on mean reading speeds for either type of aid, but the CCTV did provide significantly longer reading durations. Neither near nor far visual acuity measures were correlated with performance variables. Linear magnification, working distance, and effective magnification on the CCTV appeared to interact to influence CCTV reading speed. The data have clear implications for clinical practice.

The correct addition for near vision in presbyopia depends primarily on the amount of available accommodation and secondarily on the selection of the best fixed distance for the near work. In correcting presbyopia, it has been customary among ophthalmologists to give the patient only one test, that is, to determine the addition with which the patient "reads best" or feels most comfortable at the desired distance on the Prince rule. In ophthalmology one has at least three common methods of determining the correct distance refraction, or punctum remotum : (1) retinoscopic examination with cycloplegia, (2) trial case determinations with cycloplegia and (3) the postcycloplegia test. I recommend three methods for measuring the near point refraction, punctum proximum, or accommodation. I believe that the near point in the refraction of presbyopia is as important as the far point. Each of my three tests depends on distinctly different types of thresholds of visual

Practical details with regard to testing for and prescribing telescopic spectacles are discussed, Telescopic spectacles can be successfully used for near work in many cases in which with the ordinary correction the best distant vision obtainable is as low as 20/200. Vanity prevents most patients from wearing telescopic spectacles for distant correction in public. It is usually impracticable to use the two eyes together at the working distance. Absolute accuracy of frame adjustment is essential. Nineteen illustrative cases are briefly described. It is often better to omit the cylindrical correction unless it definitely improves visual acuity. Read before the Cleveland Ophthalmological Club, November, 1929.

The relief of presbyopia with single-vision reading glasses, bifocals, and trifocals has obvious disadvantages. Reading glasses, while very effective for a limited range of distances about the near work position, cause progressive blurring with increasing distance of observation beyond that range. Bifocals and trifocals enable the wearer to see clearly at 1 and 2 intermediate positions, but they have the disadvantage of causing discontinuity of the visual field as a result of the segments and their boundaries. The effects of a discontinuous field, in combination with the abrupt differences in focal power between segments and the surrounding lens, are blurring, distortion, and doubled vision. In some cases there is overlapping of the discontinuous fields within the total field, so that there is always some part of the environment which cannot be seen, while in other cases, though there is no overlapping, there is severe relative displacement of visual areas at

Aim: To study accommodation in relation to different refractive errors, amblyopia and to measure the anatomical changes in the accommodating eye Materials and methods: We studied the amplitude of accommodation (AA) in 150 patients in the age group 11 – 30 years which included emmetropes, myopes, hypermetropes and hypermetropic amblyopes using the Royal Air Force (RAF) rule. The anterior chamber depth (ACD), axial length (AxL) and lens thickness (LT) changes during accommodation were measured using an A-scan. Myopes and hypermetropes were further divided based on the amount of refractive error : < 2D, 2 -4D and > 4D. Results: Corrected low myopes had the highest accommodation amplitude (p < 0.05) followed by emmetropes. Corrected hypermetropes were found to have the lowest amplitude of accommodation (p < 0.05). The amblyopic eye had a significantly low AA compared to the non-amblyopic eye (p < 0.05). ACD decreased (p < 0.05) and LT increased (p < 0.05) during accommodation. The AxL increase was maximum in myopes (p < 0.05) followed by hypermetropes but the change was not significant in hypermetropes (p > 0.05). Conclusion: The amblyopic eye has low amplitudes of accommodation proving the benefit of near adds in amblyopic patients. Prolonged near work might induce myopia in susceptible eyes by increasing the axial length. Key words: accommodation, refractive error, amblyopia, biometric changes DOI: http://dx.doi.org/10.3126/nepjoph.v3i2.5267 Nepal J Ophthalmol 2011; 3(2): 146-150

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If the ocular apparatus of the average child were by nature adapted to the amount and kind of eye-work that he is ordinarily called upon to do, it would not be so necessary for us, as physicians, to consider, as we often do, the details of school hygiene. In spite of the fact that the eyes are the organs, above all others, that are called upon to labor excessively in the effort to obtain an education, they would cause us little or no anxiety if there were any provision in them for an unusual amount of accommodative effort-for excessive focusing for near work in particular. In the great majority of cases the opposite is true. We are all of us born farsighted, i. e., with the vision and visual apparatus of our savage ancestors, and with these eyes we deliberately proceed to the school-work that civilization demands, which, for its easy accomplishment, necessitates quite a different type of eye, viz., shortsighted or myopic globe with an oculo-muscular system in correspondence with it. Happily, quite a few of us run the gauntlet of these dangers to our nervous and digestive apparatus and to our sense organs with little or no damage, but some of us experience ills from which we recover either partially or not at all.

Based on the hypothesis that progression of myopia may result from tension of the extraocular muscles during prolonged convergence in near work, all such cases were treated by dissociating the eyes for near vision through monocular cycloplegia. Detailed report of one case thus treated over a period of eight year?Tis given. The treatment was successful in checking progression in all cases during the time of its use. Read before the St. Louis Ophthalmic Society, January 23, 1931. From the Department of Ophthalmology, St. Louis University School of Medicine.

• Data from the 1971 to 1972 National Health and Nutrition Examination Survey were used to estimate myopia prevalence rates for persons in the United States between the ages of 12 and 54 years. When persons were classified by the refractive status of their right eye, 25% were myopic. Significantly lower prevalence rates were found for male subjects than for female subjects and for blacks than for whites. Myopia prevalence rose with family income and educational level. The importance of income and educational level may result from their association with near work, a factor that has been implicated in the pathogenesis of myopia.

This work is a detailed exposition of a relatively new science, which the authors choose to call the "science of seeing." They make a distinction at the outset between the "science of vision" as practiced by the ophthalmologist, limiting it largely to the correction of optical and muscular anomalies, and the "science of seeing," which takes in all the complex elements involved in the use of visual sense. These include primarily the factors of lighting, but also other elements, such as speed, accuracy and ease of seeing, the causes of general and special fatigue and work efficiency. The whole subject is treated more from the standpoint of the illuminating engineer, and emphasis is placed on the study of man as a "seeing machine." This term and concept predominates throughout. The authors elaborate on the premise that prolonged near work and reduced inadequate (indoor) illumination are the twin curses of modern

Changes in tonic accommodation and tonic vergence were monitored before, during and immediately after a 45 min period of reading adult level text displayed on either a computer monitor or hard copy at 20 cm under binocular viewing conditions. Both tonic accommodation and tonic vergence gradually increased during the reading period, with changes in tonic accommodation occurring more rapidly. The average increases in tonic accommodation and tonic vergence following reading were 0.35 dioptres and 0.38 metre angles, respectively. Decay of both tonic components to the baseline in either light or total darkness occurred within the first 3 min. These results suggest that a moderate period of interrupted reading at a close distance can produce a transient increase in the tonic oculomotor levels.

Progressive myopia may result from an inherited biomechanical weakness of the sclera that allows it to stretch (creep) in response to stress. Increased intraocular pressure could be the mediator of stress produced by the inclined head position and the accommodation/convergence aspects of near work. This paper reviews data that relate to this hypothesis including work on sclera, intraocular pressure, animal models of myopia, and attempts at human treatment. Although the weight of evidence appears to support the proposed notion, no firm conclusion can be drawn due to imperfections in the design of prior studies. A future research agenda is proposed, including a controlled clinical trial of pharmacologically sustained ocular hypotension in young progressive myopes.

To evaluate the need, characteristics and proportion of occupational accurate close work in different socio-economic groups we sent a questionnaire to all 26- and 46-year-old people in the Jyväskylä district. 1 503 (75%) of the 26-year-old subjects and 1 035 (78%) of the 46-year-old subjects returned the questionnaire. 71% of the 26-year-old subjects and 68% of the 46-year-old subjects reported that they need accurate near vision in their daily work. Accurate near vision was needed for reading and writing in 61% in the younger and 55% in the older age group, industrial quality control in 14% in the younger and in 26% in the older age group, Visual Display Unit work in 7% in both age groups, and other accurate close work in 19% in the younger and in 12% in the older age group. The results show that there is a need for accurate near vision in most occupations and indicate that the visual acuity and refraction of the employee requiring occupational accurate near vision should be examined when newly employed and when having problems with near work.

Various environmental factors have been implicated in the etiology of myopia. An attempt was made quantitatively to estimate some such environmental factors, as based on the presence or absence of a family history of myopia. Age range was 10-21 years. The 200 subjects included in the study were further divided according to emmetropia/myopia. The factors studied in the four subgroups were amount of near work done per day, head posture and illumination level while doing near work, acute fevers, chronic illness, acute or recurrent diarrhea, nutritional status, and income levels. A correlation was found between myopia and near work, head posture and income levels.

Physical optics is an exact science. When used for refraction of human eyes, however, it becomes an art, because it deals with two uncertain variables, the examiner and the person examined. It will reflect the reactions of each. No matter how careful and painstaking the examiner and how cooperative the patient, there are many patients who still complain of eye strain. This is due to the fact that some things must be estimated, according to the response of the patient and the judgment of the physician. Many of these unsatisfactory cases result from incorrect estimation of the interpupillary distances for far and near work. The methods of estimating the interpupillary distance (P. D.) are too well known to require much discussion. The most frequently used for distance is the method of squinting first with the right eye and then with the left over the edge of a ruler held in

The classic statement of a difference in form of the ciliary muscle in myopic eyes, from that found in hyperopia, is taken as the starting point for a discussion of differences in accommodation between myopic and hyperopic eyes. An argument is made against the giving of a full correction for near work, in myopia of more than 3 D. The degree of correction should be determined by the prescriber's knowledge of the accommodation, in the individual case. Read before the Section on Ophthalmology of the College of Physicians of Philadelphia, March 19, 1924.

Although myopia is such a common condition and is an important cause of ocular morbidity, surprisingly few articles on the subject are published in the current ophthalmic literature. This collection of articles presented at the Third International Conference on Myopia does something to redress the balance. Subjects discussed were grouped into epidemiology, genetics, oculometry, accommodation, clinical investigations, experimental studies, the complications of myopia, prophylaxis, and treatment. Experimental studies on monkeys, young tree shrews, and chickens suggest that accommodation is a factor in the development of myopia but although there is strong circumstantial evidence that near work is related to the development of myopia in children, other environmental factors cannot be excluded. Even highly heritable features such as anterior chamber depth seem to be affected by environmental factors. If accommodation is a factor, the mechanism whereby it causes an increase in axial length is still unknown. A rise in pressure

To the Editor: —Miss Y. A., aged 18, office clerk, of slight stature, frail physique and attentive and refined disposition, for four years had had the ordinary symptoms of asthenopia, which had been worse for several months. Refraction under complete cycloplegia showed hyperopic astigmia, axes oblique. A full correction was provided, which, to my surprise, gave but little relief. The correction was verified by repeated examinations and the most careful attention paid to the adjustment of the frames, but the symptoms continued. The patient became eccentric and stubborn, at times exhilarated, then depressed, and would exhibit lapses of memory and deportment with an indifference to the usual conventionalities and proprieties. The headaches were intermittent and not caused by near work, but were always increased by it in an attempt at reading, etc., during an attack. Insomnia was present at night, yet she would fall asleep at her work during the

The inability to use apparently healthy eyes for near work, without increasing discomfort or pain, is usually caused by refractive errors, or insufficiency of accommodation. In a series of 500 patients with asthenopic complaints taken consecutively from my records, the symptoms were caused by hypermetropia, astigmatism or presbyopia in 75 to 80 per cent. In 20 to 25 per cent. the asthenopia could not be accounted for in this manner, for either the optic conditions were perfect or, if not, their correction gave no relief. Some of the factors which lead to asthenopia, in the instances not dependent upon optic faults, are suggested by a study of the refractive cases, if we consider them as patients and not merely as the possessors of optically imperfect eyes. The importance of refractive errors varies according to whether we study them either in the patients of our office practice or in the population

WITH reference to the inquiry in NATURE of May 1 (p. 215), the general rule in cases where a person using spectacles wishes to use an optical instrument is, that for telescopes and instruments used for distant objects, use the distance correction; for microscopes and instruments for near work, the near correction should be worn. Care should always be taken to use the centre of the spectacle lens. If no astigmatism is present there is generally sufficient focussing room to enable the observer to dispense with the spectacles. The most comfortable method is to have a cap made for the eyepiece of the instrument with a lens equivalent to that in the spectacle. This should be set as close to the eye-lens as possible, and in cases of astigmatism they should be marked so that the axis may be correctly set. Any good optician will do this at small expense.

The case reported below is considered of interest for the following reasons: 1. Because of the unsuspected serious nature of the condition present, the symptoms being those of iritis, with diminished intra-ocular tension, whereas one would expect those of glaucoma, with increased intra-ocular tension. 2. Because it emphasizes the necessity of enucleating blind eyes which are giving pain, as these may contain life-destroying potentialities. 3. Because it demonstrates theimportance of a pathologic examination of all eyes removed. History. —The patient, D. McA., aged 31, was a core-maker, native of Philadelphia. His father died as result of accident, aged 55; health always good; he used glasses for near work only; eyes were healthy. Mother, aged 55, living and well; uses glasses for near work only. Four brothers and two sisters are living and in good health. Only one brother wears glasses. No family history of ocular disease is obtainable. Patient had

Many theories have been advanced for the etiology of myopia. Some (Arlt, Branner and Heinonen) believe that continued use of the eyes for close work, such as reading and sewing, causes elongation of the globe as a result of compression by the internal rectus muscle. Others believe that the general physical condition of city dwellers is inducive to the development of myopia (Steiger). Some insist that the intra-ocular tension is increased by prolonged near work, with resultant stretching of the posterior pole of the eye, and this accounts for the prescribing of miotics by some ophthalmologists in cases of myopia (Mayer). Levinsohn is the chief protagonist of the view that by persistently keeping the head bent downward in reading and sewing the eyeball is made to stretch in its antero-posterior diameter, the posterior pole bearing the brunt. These views really belong in the category of mechanical influence causing stretching of

Many patients with heterophoria, who appear to have fair to good amplitude of fusion with prisms when fixating on a 3 mm. white-headed pin or light at 25 cm., are unable to maintain fusion when accommodating on small print (300 mm. type for example). These patients, usually young children, are frequently found to be slow readers and manifest an overconvergence on ophthalmographic studies, particularly when shifting their fixation to the next line of print. Patients with this difficulty often improve their ability to sustain fusion for near work with a simple home exercise. The patient is given a horizontal prism rack 1 and an accommodation card 2 (Fig. 1) with letters, numbers, and single E's graduated in size. Holding the accommodation card in one hand and the prism rack in the other (Fig. 2), the patient is instructed to fixate the smallest word, number, or E which he can fuse while

I believe that the entire correction of the astigmatism present in every eye, is a necessity, that is, provided the eye is used at all for near work. If there is no use for a knife there is no need to sharpen it, but just as soon as the eye is used as an instrument for seeing, its refraction must be so adjusted that the ciliary muscle fibers act equally, and not unequally as in astigmatism, to produce a clear, distinct image on the retina.The disturbances of the recti muscles of which we hear so much today are in a great part but a development of nature's effort to allow the tired ciliary muscle some rest by presenting on the retina an image which requires other fibers of the muscle than those previously exhausted, to do an extra share of work, relieving those which have become tired from overuse.

The ideal position of lenses, when there is perfect muscle adjustment of the eyes, is such that the visual axes may cut their optical centers, and that the planes of the lenses may be parallel with the equatorial planes of the eyes. When the visual axes cut the optical centers of the lenses there can be no prismatic effect; and when the plane of the lens is parallel with the equatorial plane of the eye there can be no cylindrical effect. A want of parallelism between the plane of the lens and the equatorial plane of the eye means that there will be a cylindrical effect, for, as is well known, the strength of the lens, at right angles to the axis of tilting, is increased, while along the axis of tilting its power is unchanged. Tilting a lens 45 degrees practically doubles its refractive power for the rays that