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Artificial Lighting and Eyesight

Artificial Lighting and Eyesight Workshop and Production Section AIRCRAFT ENGINEERING September, 1940 By G. V. Downer H E preservation of the eyes and the ability keeps opening and closing in the endeavour to adapt to make the best use of them are obviously itself to the continually varying illumination on of the utmost importance to all those th e work. concerned with aviation, whether in connexion with Similarly, if there is much uneasiness in the flying itself or with aircraft production. general illumination (for instance, with individual Defective vision is more widespread to-day than desk lights, or local lighting; of machines) the a t any previous period in history. This is probably illumination of tha t par t of the desk, machine, etc., due t o a variet y of causes arising out of the economic close to the light, is man y times brighter than that conditions and technical developments of modern of the more distant parts, and the iris soon gets life, and the relatively unnatural lives led by so overworked in looking from one part of the work to man y "civilized " people. anothe r or in looking round the room. This is One such cause is undoubtedly the intensification because the iris is only intended by nature to deal wit h th e comparatively slow and occasional changes of the night-time activities, and consequent greatly of brightness occurring in nature, as when the sun increased use of artificial light, which can hardly fail "goe s in " behind clouds, and comes out again, or to put a strain on the eyes, since even the best th e gradual increase or decrease in strength as it artificial lighting is very different in many respects rises or sinks. from the natural conditions of daylight, for which the eyes have been evolved and adapted by nature. compressing or extending the eyball from front to I t will be realized from the above considerations This source of strain, of course, is greatly increased rear so as to adjust the distance between the lens tha t for most purposes indirect lighting is the ideal, by the inadequacy or unsuitability of many artificial and the retina, in much the same way as a camera since the sources are concealed from direct view, so lighting installations. is focused by moving the lens towards or away tha t there can be no glare, there are no appreciable Another factor contributing to the prevalence of from the plate. shadows and, if properly designed, the illumination impaired eyesight is probably the general nervous The retina is a thin transparent layer, about is even throughout, penetrating every corner and tension induced in the majority of people, often enabling every object to be seen clearly and equally 1/5 mm. thick, containing a mass of nerve fibres unconsciously, by the stress and strain of modern well from all sides. and nerve endings, the latter terminating in the life with its greater complexity and speed. sensitive rods and cones, on which light apparently Where indirect lighting is not practicable, the Again, much modern diet, particularly in the produces a photo-chemical reaction leading to lighting should preferably be carried out by com­ towns and cities, consists of processed and denatured excitation of the nerve endings. Altogether the parativel y large areas of comparatively low surface food, which is deficient in vitamins and in the retin a contains abou t 3,000,000 cones and 15,000,000 brightness, so as to reduce glare to a minimum and protective alkaline minerals so essential for keeping rods. The cones are comparatively insensitive in soften shadows. Laylights and luminous panels or the bloodstream pure; consequently many town- weak light but are sensitive to colour in bright artificial windows are preferable to pendan t fittings, bred people suffer from lowered vitality due to an light, while the rods are considerably more sensitive bu t when the latter are used they should be placed impure bloodstream, which affects the whole body t o weak light but give no colour sensation. The comparativel y high so as to be as far above the adversely. This may lead to eye trouble, because fovea contains no rods but is tightly packed with normal line of vision as possible. the blood either fails to nourish the eyes properly cones, while in the remainder of the retina the nerve As most artificial light differs considerably from or, more frequently, because it fails to keep the endings are further apart and there are more rods dayligh t in its colour, or wavelength mixture, it is tissues cleansed from the by-products of metabolism tha n cones. also desirable, wherever possible, to correct this by so that the nerves or muscles of the eye become Night vision is looked after by the rods, the eye suitable filters or other appropriate means, so as to congested and fail to work properly. automaticall y moving the images from the fovea approximat e as closely to daylight as possible, I n view of these and other manifold risks to int o the peripheral region when the light is too otherwise the unnatural colour of the artificial light which the eyes ma y be subjected, coupled with their weak to stimulate the cones ; in which case objects is bound in time to have an adverse effect on the outstandin g importance to engineers and tech­ focused on the fovea would be invisible. Every­ eye. Apart from cases where the work involves nicians, it would seem desirable for all connected thing , therefore, looks grey at night, since the rods colour matching, or for other reasons necessitates with aviation to know something of the structure ar e not sensitive t o colour and fine detail cannot be th e use of "artificial daylight," such colour- of the eye and the mechanism of sight. distinguished owing to the comparatively coarse corrected light is always helpful in avoiding strain The following short account and accompanying structur e of the peripheral retina. where long hours have to be worked by artificial sketch of the right eye as seen from above (Fig. 1), The above gives only a very rough and partial light. may , therefore, be of interest to those not already idea of the structure and operation of the eye, but acquainted with the subject. Othe r factors in the causation of eye-strain can enough, perhaps, to indicate to some extent the The eyeball is approximately spherical, about also be avoided or mitigated in various ways with intricat e and delicate nature of the mechanism of 1 in. in diameter, and comprises three layers, the a little care. For instance, much defective eyesight sight, and to suggest the desirability of taking outer or sclerotic, the middle or choroid, and the appear s to be due to a strained condition of the trouble to avoid unnecessary causes of strain and to inner layer, known as the retina. muscles surrounding the eyes, and this condition is correct, as far as possible, any adverse factors in ver y largely the result of mental strain arising in one The sclerotic layer is white and opalescent except environmen t or way of life. for a transparent portion in front, the cornea. wa y or another from the strenuous conditions of Fo r instance, the extensive use of artificial light modern life. Every endeavour therefore should be Th e choroid or middle layer develops in front into in these times, when many factories are working mad e to relax the eyes as much and as frequently the folds of the ciliary processes and the ciliary night and day, and some are permanently "blacked- as possible. muscle, which latter controls the expansion and out " so tha t artificial light has to be used through­ contraction of the crystalline lens. Immediately in Heading or writing for long hours or continual ou t the 24 hours, renders it highly important to front of this is another extension of the choroid ensure adequate lighting of the most suitable type use of the eyes at one particular focus, often known as the iris, which acts as an automatically throughou t every installation. necessary in technical work, tends to make the adjustabl e curtain for controlling the amount of muscles lose their resiliency and fail to focus the The essential requirements of really good arti­ light admitted to the eye, that part of the lens ficial lighting, for practically all purposes, are; eye correctly for other distances. To counteract exposed by the iris being known as the pupil. this tendency it is desirable to look up and around even distribution, freedom from glare and elimina­ for a few seconds as frequently as the work permits. The inner layer or retina is a continuation of the tion of shadows, or their reduction to a minimum. Fo r example, when reading or writing, it is a good optic nerve, which enters at the back of the eye, These are characteristics of North daylight, which thin g to glance at the opposite wall or out of the and is adapted to receive the images of external is generally recognized as the ideal for most kinds window for a moment, after every few paragraphs. objects within the field of vision. of work, and the best form of artificial light is that Frequen t blinking and closing the eyes for a few Between the cornea and the lens is the aqueous which most closely resembles daylight, since the seconds when possible, also help to relax the nerves chamber and between lens and retina the vitreous purpose of artificial light is to replace daylight when an d muscles and thus to avoid strain. There are chamber making the central body of the eyeball. th e latter is not available and so give the eye the various simple eye exercises and other simple ways Light enters the eye through the cornea, passes nearest possible approaching to the type of light in which tension can be relaxed and weak muscles throug h the aqueous chamber and the lens, the for which it was "designed." strengthened, with a view to avoiding or post­ outer rays being cu t off by the iris, and then through Most factories, drawing offices, etc., are lighted poning as long as possible the resort to glasses. It th e vitreous chamber to form an inverted image on b y numerous direct fittings, which fail to satisfy is not always realized that glasses are only crutches th e retina. an y of the above requirements; for the lighting for the eyes and do nothing to improve their Th e field of exact vision is very limited, being is uneven, being brighter than necessary close under functioning but rather the reverse, for when glasses confined to a small oval depression in the retina th e fittings and much less bright, often not bright are worn the eyes are artificially restricted both in called the fovea, or yellow spot, on which objects are enough, in many intermediate positions. Each focus and in the field of vision, and as a rule stronger accuratel y focused by the lens. The whole of the fitting is a source of glare and the eye cannot avoid glasses are required every two or three years to such glare by looking in another direction, as in the retina, however, is sensitive to light and gives a keep pace with the deterioration of natural vision. case of a single light source such as th e sun, for there large field of hazy vision. ar e fittings in all directions. There is also indirect Defective vision can also be caused by contracted Accommodation, or focusing, is carried out partly glare from reflections of the bright lights in polished neck muscles and slight displacements of the spinal b y the ciliary muscles, which alter the shape of the part s of machinery, in glass partitions or windows, vertebra: at the back of the neck, impeding the lens, and partly by the exterior muscles (1-6 in the or in the smooth surfaces of drawing paper, note­ blood and nerve supply to the eyes. Such cases sketch), whose main function is to turn the eye as a books, etc., the latter often being particularly can often be cured or improved by spinal manipula­ whole in any direction in which it is desired to look. troublesome when using pencil. tion, either Osteopathic or Chiropractic. These muscles consist of the superior and inferior rectus muscles 1 and 2, which direct the eye upwards Again, every source of light produces its own set Finally, it is worth remembering, that the eyes, or downwards, the external and internal rectus of shadows, so that where there are many sources like every other part of the body, depend upon the muscles 3 and 4, which turn the eye from side to ther e are many shadows from every object, and bloodstream both for nourishment and for cleansing side, and the superior and inferior oblique muscles, thes e are liable to be very irritating, confusing and from the waste-products of metabolism, while the which move the eye obliquely. tiring to the eye, especially where there is much condition of the bloodstream depends mainly on movemen t of personnel or machinery; for the iris These six muscles also assist in accommodation by th e diet. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Artificial Lighting and Eyesight

Aircraft Engineering and Aerospace Technology , Volume 12 (9): 1 – Sep 1, 1940

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Emerald Publishing
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Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb030692
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Abstract

Workshop and Production Section AIRCRAFT ENGINEERING September, 1940 By G. V. Downer H E preservation of the eyes and the ability keeps opening and closing in the endeavour to adapt to make the best use of them are obviously itself to the continually varying illumination on of the utmost importance to all those th e work. concerned with aviation, whether in connexion with Similarly, if there is much uneasiness in the flying itself or with aircraft production. general illumination (for instance, with individual Defective vision is more widespread to-day than desk lights, or local lighting; of machines) the a t any previous period in history. This is probably illumination of tha t par t of the desk, machine, etc., due t o a variet y of causes arising out of the economic close to the light, is man y times brighter than that conditions and technical developments of modern of the more distant parts, and the iris soon gets life, and the relatively unnatural lives led by so overworked in looking from one part of the work to man y "civilized " people. anothe r or in looking round the room. This is One such cause is undoubtedly the intensification because the iris is only intended by nature to deal wit h th e comparatively slow and occasional changes of the night-time activities, and consequent greatly of brightness occurring in nature, as when the sun increased use of artificial light, which can hardly fail "goe s in " behind clouds, and comes out again, or to put a strain on the eyes, since even the best th e gradual increase or decrease in strength as it artificial lighting is very different in many respects rises or sinks. from the natural conditions of daylight, for which the eyes have been evolved and adapted by nature. compressing or extending the eyball from front to I t will be realized from the above considerations This source of strain, of course, is greatly increased rear so as to adjust the distance between the lens tha t for most purposes indirect lighting is the ideal, by the inadequacy or unsuitability of many artificial and the retina, in much the same way as a camera since the sources are concealed from direct view, so lighting installations. is focused by moving the lens towards or away tha t there can be no glare, there are no appreciable Another factor contributing to the prevalence of from the plate. shadows and, if properly designed, the illumination impaired eyesight is probably the general nervous The retina is a thin transparent layer, about is even throughout, penetrating every corner and tension induced in the majority of people, often enabling every object to be seen clearly and equally 1/5 mm. thick, containing a mass of nerve fibres unconsciously, by the stress and strain of modern well from all sides. and nerve endings, the latter terminating in the life with its greater complexity and speed. sensitive rods and cones, on which light apparently Where indirect lighting is not practicable, the Again, much modern diet, particularly in the produces a photo-chemical reaction leading to lighting should preferably be carried out by com­ towns and cities, consists of processed and denatured excitation of the nerve endings. Altogether the parativel y large areas of comparatively low surface food, which is deficient in vitamins and in the retin a contains abou t 3,000,000 cones and 15,000,000 brightness, so as to reduce glare to a minimum and protective alkaline minerals so essential for keeping rods. The cones are comparatively insensitive in soften shadows. Laylights and luminous panels or the bloodstream pure; consequently many town- weak light but are sensitive to colour in bright artificial windows are preferable to pendan t fittings, bred people suffer from lowered vitality due to an light, while the rods are considerably more sensitive bu t when the latter are used they should be placed impure bloodstream, which affects the whole body t o weak light but give no colour sensation. The comparativel y high so as to be as far above the adversely. This may lead to eye trouble, because fovea contains no rods but is tightly packed with normal line of vision as possible. the blood either fails to nourish the eyes properly cones, while in the remainder of the retina the nerve As most artificial light differs considerably from or, more frequently, because it fails to keep the endings are further apart and there are more rods dayligh t in its colour, or wavelength mixture, it is tissues cleansed from the by-products of metabolism tha n cones. also desirable, wherever possible, to correct this by so that the nerves or muscles of the eye become Night vision is looked after by the rods, the eye suitable filters or other appropriate means, so as to congested and fail to work properly. automaticall y moving the images from the fovea approximat e as closely to daylight as possible, I n view of these and other manifold risks to int o the peripheral region when the light is too otherwise the unnatural colour of the artificial light which the eyes ma y be subjected, coupled with their weak to stimulate the cones ; in which case objects is bound in time to have an adverse effect on the outstandin g importance to engineers and tech­ focused on the fovea would be invisible. Every­ eye. Apart from cases where the work involves nicians, it would seem desirable for all connected thing , therefore, looks grey at night, since the rods colour matching, or for other reasons necessitates with aviation to know something of the structure ar e not sensitive t o colour and fine detail cannot be th e use of "artificial daylight," such colour- of the eye and the mechanism of sight. distinguished owing to the comparatively coarse corrected light is always helpful in avoiding strain The following short account and accompanying structur e of the peripheral retina. where long hours have to be worked by artificial sketch of the right eye as seen from above (Fig. 1), The above gives only a very rough and partial light. may , therefore, be of interest to those not already idea of the structure and operation of the eye, but acquainted with the subject. Othe r factors in the causation of eye-strain can enough, perhaps, to indicate to some extent the The eyeball is approximately spherical, about also be avoided or mitigated in various ways with intricat e and delicate nature of the mechanism of 1 in. in diameter, and comprises three layers, the a little care. For instance, much defective eyesight sight, and to suggest the desirability of taking outer or sclerotic, the middle or choroid, and the appear s to be due to a strained condition of the trouble to avoid unnecessary causes of strain and to inner layer, known as the retina. muscles surrounding the eyes, and this condition is correct, as far as possible, any adverse factors in ver y largely the result of mental strain arising in one The sclerotic layer is white and opalescent except environmen t or way of life. for a transparent portion in front, the cornea. wa y or another from the strenuous conditions of Fo r instance, the extensive use of artificial light modern life. Every endeavour therefore should be Th e choroid or middle layer develops in front into in these times, when many factories are working mad e to relax the eyes as much and as frequently the folds of the ciliary processes and the ciliary night and day, and some are permanently "blacked- as possible. muscle, which latter controls the expansion and out " so tha t artificial light has to be used through­ contraction of the crystalline lens. Immediately in Heading or writing for long hours or continual ou t the 24 hours, renders it highly important to front of this is another extension of the choroid ensure adequate lighting of the most suitable type use of the eyes at one particular focus, often known as the iris, which acts as an automatically throughou t every installation. necessary in technical work, tends to make the adjustabl e curtain for controlling the amount of muscles lose their resiliency and fail to focus the The essential requirements of really good arti­ light admitted to the eye, that part of the lens ficial lighting, for practically all purposes, are; eye correctly for other distances. To counteract exposed by the iris being known as the pupil. this tendency it is desirable to look up and around even distribution, freedom from glare and elimina­ for a few seconds as frequently as the work permits. The inner layer or retina is a continuation of the tion of shadows, or their reduction to a minimum. Fo r example, when reading or writing, it is a good optic nerve, which enters at the back of the eye, These are characteristics of North daylight, which thin g to glance at the opposite wall or out of the and is adapted to receive the images of external is generally recognized as the ideal for most kinds window for a moment, after every few paragraphs. objects within the field of vision. of work, and the best form of artificial light is that Frequen t blinking and closing the eyes for a few Between the cornea and the lens is the aqueous which most closely resembles daylight, since the seconds when possible, also help to relax the nerves chamber and between lens and retina the vitreous purpose of artificial light is to replace daylight when an d muscles and thus to avoid strain. There are chamber making the central body of the eyeball. th e latter is not available and so give the eye the various simple eye exercises and other simple ways Light enters the eye through the cornea, passes nearest possible approaching to the type of light in which tension can be relaxed and weak muscles throug h the aqueous chamber and the lens, the for which it was "designed." strengthened, with a view to avoiding or post­ outer rays being cu t off by the iris, and then through Most factories, drawing offices, etc., are lighted poning as long as possible the resort to glasses. It th e vitreous chamber to form an inverted image on b y numerous direct fittings, which fail to satisfy is not always realized that glasses are only crutches th e retina. an y of the above requirements; for the lighting for the eyes and do nothing to improve their Th e field of exact vision is very limited, being is uneven, being brighter than necessary close under functioning but rather the reverse, for when glasses confined to a small oval depression in the retina th e fittings and much less bright, often not bright are worn the eyes are artificially restricted both in called the fovea, or yellow spot, on which objects are enough, in many intermediate positions. Each focus and in the field of vision, and as a rule stronger accuratel y focused by the lens. The whole of the fitting is a source of glare and the eye cannot avoid glasses are required every two or three years to such glare by looking in another direction, as in the retina, however, is sensitive to light and gives a keep pace with the deterioration of natural vision. case of a single light source such as th e sun, for there large field of hazy vision. ar e fittings in all directions. There is also indirect Defective vision can also be caused by contracted Accommodation, or focusing, is carried out partly glare from reflections of the bright lights in polished neck muscles and slight displacements of the spinal b y the ciliary muscles, which alter the shape of the part s of machinery, in glass partitions or windows, vertebra: at the back of the neck, impeding the lens, and partly by the exterior muscles (1-6 in the or in the smooth surfaces of drawing paper, note­ blood and nerve supply to the eyes. Such cases sketch), whose main function is to turn the eye as a books, etc., the latter often being particularly can often be cured or improved by spinal manipula­ whole in any direction in which it is desired to look. troublesome when using pencil. tion, either Osteopathic or Chiropractic. These muscles consist of the superior and inferior rectus muscles 1 and 2, which direct the eye upwards Again, every source of light produces its own set Finally, it is worth remembering, that the eyes, or downwards, the external and internal rectus of shadows, so that where there are many sources like every other part of the body, depend upon the muscles 3 and 4, which turn the eye from side to ther e are many shadows from every object, and bloodstream both for nourishment and for cleansing side, and the superior and inferior oblique muscles, thes e are liable to be very irritating, confusing and from the waste-products of metabolism, while the which move the eye obliquely. tiring to the eye, especially where there is much condition of the bloodstream depends mainly on movemen t of personnel or machinery; for the iris These six muscles also assist in accommodation by th e diet.

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Sep 1, 1940

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