Aging Eyes

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Lighting and theAging Eye

Lighting Design - Assignment One

As humans age we experience various physiological changes to our bodies, such as

deterioration of our vision and hearing, and we also become more susceptible to

diseases. These changes and diseases will affect us in the workplace and may lead to

more accidents among the older workers and also an inability to work properly.

2011

Dominic Spillane

Department of Electrical Engineering, C.I.T.

2/25/2011

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Department of Electrical Engineering

ETC3-C Dominic Spillane 11-02-2011

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IntroductionAs humans age they experience various physiological changes to their bodies, such as

deterioration of their vision and hearing, and they also become more susceptible to diseases.These changes and diseases will affect them in the workplace and may lead to more accidents

among the older workers and also an inability to work properly amongst older workers.

As can be seen in most countries around the world today the average age when people retire

is increasing with the result what the average age of workers has also increased. Older

workers are important in any workplace because of their experience so it is important to

ensure they are both safe and able to work properly in a work environment.

Various things can be done when designing a work place to counteract these changes to our

eyes and ensure they have as little effect as possible on the worker. These include types oflighting used, availing of natural light in the work area, colour of surfaces etc.

Part of an electrical engineers job when designing a building is to design the work area taken

all this into account. This report will look at the effects of ageing on the human eye and how

it affects a workforce. It will also show how these effects can be counteracted when designing

a building.

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The Eye and the Affect Aging has on the Eye

The human eyes are part of a general group of eyes called camera-type eyes (1) and are

made up of different parts. If light reflects off an object and someone is looking at the object

this light will enter their eyes.

The first part of the eye the light will meet is called the cornea. The cornea is a transparent

structure found in the very front of the eye that helps to focus incoming light. The cornea

takes widely diverging rays of light and bends them through the pupil, the dark, round

opening in the centre of the coloured iris. The pupil can expand or contract depending on the

amount of light entering the eye.

The space between the cornea and the iris is filled with a fluid called aqueous humor. Behind

the pupil is the lens which helps to focus light to the back of the eye. Next the light passes

through an interior chamber in the eyeball which is filled with a jelly-like tissue called the

vitreous humor.

The light then hits the retina at the back of the eye. The retina is a membrane containing

photoreceptor nerve cells that lines the inside back wall of the eye. The photoreceptor nerve

cells of the retina change the light rays into electrical impulses and send them through the

optic nerve to the brain where an image is perceived.

Figure 1.0 The Human Eye (1)

The Effects of Aging on the Eye

Vision is often the first sense that is noticeably affected as we age. As humans age our eyes

gradually change and can suffer from different diseases. These changes will have different

effects on a workers vision.

From about the mid 40s the human eyes begin to deteriorate and this will lead to different

problems with a persons vision. As the eye ages the size of the pupil gradually reduces in

size and because the pupil governs the amount of light that can reach the retina, if it reducesin size, a person will find it harder to seen in darker conditions. Also the eye lens yellows and

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becomes thick which will also affect how much light reaches the retina. The light adapted eye

of a 20 year old receives six times more light than that of an 80 year old. In dark adapted

conditions, the 20 year old eye receives about 16 times more light (2).These problems

include:

Night vision problems & adaptability problems the eye will react more slowly tochanges in darkness and light will become less adaptable in the dark.

Glare Sensitivity The eye may become more sensitive to glare because of lightscattering due to an aging lens and cornea.

Colour Vision Colour vision changes cause some reduction of ability todiscriminate blues and blue-greens. This is caused by the yellowing of the eye.

Contrast Sensitivity and FocusingA person may find it difficult to focus on objectsand may have difficulty with the contrast of different colours.

Nearsightednessdifficulty in focusing smaller print.The human eyes become more sensitive to diseases such as tearing, cataracts and floaters fromthis age on too. The following are some of the most common diseases and conditions:

Age-related Macular Degeneration (AMD): Age-related Macular Degeneration is a disease

which causes the eye to lose sharp, central vision, which is needed for clear vision, reading

and driving. It wont lead to total blindness. It normally affects people from their 50s onward.

Figure 1.1 How some with AMD might see.(3)

Cataract(s): The lens of the eye is normally clear but when a person suffers from cataract(s)

the lens becomes cloudy and prevents the person from seen clearly. It occurs slowly with no

pain in the eye. It can cause the person to have difficulty reading and driving.

Figure 1.2 How some with cataracts might see.(3)

Floaters: Floaters are tiny spots or specks that float across the field of vision. They are most

noticeable in well-lit rooms or outdoors on bright days

Figure 1.3 How some with Floaters might see.(4)

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Glaucoma & Retinitis pigmentosa (RP): Glaucoma occurs when there is too much fluid

pressure inside the eye and can cause vision loss and blindness.

Figure 1.4 How some with Glaucoma might see. (3)

Low Vision:People who suffer from low vision find it difficult to do things tasks such as

read, cook, watch TV or write even with glasses, contact lenses and medicine.

Presbyopia: Presbyopia occurs normally from the age of 40 onwards. It causes the sufferer to

slowly lose the ability to see close objects or small print.

Tearing: Tearing occurs when a persons eyes are sensitive to light, wind, or temperature

changes.

Dry eyes: Dry eyes are another age related disease. Dry eyes occur when a persons tearducts

aren't able to provide adequate moisture for their eyes.

The table below shows at what age the eyes are effected and how.

Age Eye Problem

40sPresbyopia (difficulty with near vision focus). Increased risk of dry eye and

computer vision syndrome.

50s Risk increase for cataracts, glaucoma and age-related macular degeneration (AMD).

Presbyopia becomes more advanced. Risk of dry eye increases for women. Average

age for onset of Glaucoma is around 58. (5)

60s

Risk increase for age-related eye diseases. Ability to see in low lighting decreases.

Age-related eye changes cause visual disturbances such as spots and floaters.

70s & 80s

Most people in this age group already have or will cataracts. Colour vision declines,

and visual fields begin to narrow.

Table 1.0 The age at which Human Eyes suffer from different conditions. (6)

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Quality and Quantity of light Required in a

Work AreaWhen design any building an electrical engineer must pay particular attention to the lighting

of the building. This is because the quality of lighting is of extreme importance especially in

a working environment where old employees may be working. If an installation isnt of the

correct luminance then the following symptoms may result:

Symptoms From Too Much Light Include:

Irritation, burning, tearing, and redness of the eyelids. Reduced sharpness of vision and sensitivity to contrast.

Symptoms From Too Little Light Include:

Double vision and headaches. Reduced ability to quickly adjust focus between near and

and far objects.

Reduced sharpness of vision and sensitivity to contrast. Musculoskeletal problems from adapting poor postures

to compensate for the inadequate light.

Table 2.0 Symptoms resulting from incorrect luminance. (7)

There are several different aspects that will affect the quality of lighting a working

environment. The main aspects of lighting that will have an effect on older workers would be

contrast, distribution, glare, luminance and reflectance.

Contrast: is the relationship between the light coming from an object and the immediate

background, such as words on paper. High contrast is important for fine detail work. Using a

black pen in place of a pencil for handwritten copy will increase the contrast and improve thereadability.

Distribution: How the light is distributed by a luminaire is very important in lighting design.

This will affect how much light falls on a surface. Some tasks will require luminaires which

will shine all the light in one area while other tasks will require lights that will distribute light

over a wide area. How the luminance of a light is distributed is important for older workers as

they will require more light than a younger person.

Glare:Glare occurs when there is too much light entering the eye. It will cause discomfort

and impaired vision. Because an older worker requires more light than a young person but

also will suffer more from any increase in glare, when designing an installation, an electrical

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engineer must insure that the installation is of the correct luminance for the task required but

also keep glare to a minimum. There are five main forms of glare:

Blinding Glare: is glare which causes a total loss of vision. Direct Glare: is glare caused by high luminance that is directly visible from aviewers position. Disability Glare: is glare that will reduce a viewers visual performance and

visibility.

Discomfort Glare: is glare which will cause the viewer discomfort but will not willnot impair the viewers vision.

Reflected Glare: is glare which is caused by light reflecting off a shinny or polishedsurface such as glass or water.

Luminance: This is the amount of light giving off by a luminaire. There should not be a great

difference between the luminance levels for a task and that of the surrounding area because

older workers find it harder for their eyes to adjust when going from will lit areas to darker

areas of an installation. Luminance levels for the immediate area surrounding the tasks should

be one third that of the task.

Reflectance: This is how much light that is hitting a surface is reflected by that surface. This

reflectance should be limited as much as possible

An area of huge importance in a working environment is task lighting. The amount required

will depend on the task and the age of the person doing the task. The task lighting should be

set up so workers can clearly see what theyre doing with straining their eyes and helps draw

attention to hazardous operations and equipment (8) .

General Activity Typical Location/

Types of Work

Average

Illuminance Lux

(Lx)

Minimum measured

Illuminance Lux

(Lx)

Movement of people, machine and

vehicles.

Lorry parks, corridors,

circulation routes. 20 5

Movement of people, machine and

vehicles in hazardous areas; rough

work not requiring any perception of

detail.

Construction site clearance,

excavation and soil work,

docks, loading bays,

bottling and canning plants.

50 20

Working requiring limited perception

of detail.

Kitchens, factories

assembling large

components, potteries.

100 50

Work requiring perception of detail. Offices, sheet metal work,

bookbinding. 200 100

Working requiring perception of fine

detail.

Drawing offices, factories

assembling electronic

components, textile

production.

500 200

Table 2.1 Average and minimum measured illuminance published in HSE Gudance Note HS(G)38:Lighting at Work.

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Lighting Design to Accommodate an Aging

work Force

There are different ways in which an engineer can accommodate older workers when

designing a lighting scheme for an installation. The following are just some of the ways to

counteract the above mentioned problems:

Better Task Lighting: The Task lighting is over extreme importance when doing any

installation. Lighting levels for any task should be increased for older works, light levels on

the task should be at least 1000 lx (100 fc) (8). Dimmers and adjustable light fixtures could

be used instead of on off switching so as to allow a work to adjust a light luminance to suit

their needs. For tasks requiring a lot of detail, such as sewing extra lighting such as table

lamps could be included could be installed. In order to reduce shadows from these tablelamps if the worker is right hand the lamp should be placed on the left side and slightly in

front of the person while if they are left handed the lamp should be placed slightly in front

and to the right of the worker. When using suspended luminaires above a work area the

luminaires should be mounted approximately 15 in. (visually demanding) to 24 in. above the

task area.

Reduce Glare: Glare and light reflections can be minimized by changing the position of the

light source relative to the usual line of sight of a worker and also using light-color matte

finishes on walls, ceilings, and floors. Try to avoid dark ceilings as this will increase glare

greatly. When using ceiling mounted lights try to avoid using clear globes or thin diffusers

and insure that the lights are mounted at least 6ft, 8in. above floor level. To reduce glare from

windows use blinds, shades or curtains.

Increase Contrast and Colour Perception: To increase contrast between different levels in

flooring such as steps or ramps use high contrast colours, e.g. red and black. This will help

older workers distinguish between the levels better and reduce incidents in the work place.

Doorframes could also be painted a contrasting colour to the wall to help distinguish between

them. Luminaires can also be positioned to highlight different levels, entrances and exits,

especially on emergency exit routes. Try to avoid traditional incandescent lights as they will

emphasize yellow and red colours and instead use halogen or high-quality fluorescent lamps

which will people older workers distinguish colours better.

Luminaince and Distribution: Natural light should be used where possible and dark areas

should be eliminated, wall lights would be one way of doing this. The light levels in living

environments used by older adults should be increased by at least 50% over those

comfortable for younger people. In general, ambient light levels should be at least 300 lux

(lx) [30 footcandles (fc)]. Illuminance levels should be kept around the same level as older

workers will find it harder to adapt when going from bright areas to dark areas. Where there

are bright areas near dark areas transition spaces should be used.

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ConclusionIt is well known that the more light humans get the happier and more productive they are and

is especially important in any working environment. AS can be seen from the report it very

important for older workers to have good quality lighting in the right quantity. It will lead to a

more happier and productive work force.

Although it may cost the employer extra money to insure the lighting of a working area is

adequate for older workers if the area is of the correct illumination than it will have benefits

for both the employer and employee. The employer will have a happier, productive and more

experienced work force. Also with the correct lighting there should be less costly and time

consuming accidents for the employer to have to deal with. The employee will also benefit as

their eye sight will be better than that of a working in less illuminated working environment.

Also the employee will find that they are happier when there working area is of theilluminance.

This is why as electrical engineers, when designing any working installation the lighting

scheme is extremely important especially where older employees will be stationed. Both the

quality and quantity of light on a task area is of extreme importance to older workers. The

employees shouldnt have to strain their eyes while doing their task and shadows should be

eliminated where possible. Also the area around the task area should be close to the same

luminance levels as that of the task area.

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GlossaryCornea: The transparent, outer "window" and primary focusing element of the eye. The

outer layer of the cornea is known as epithelium. Its main job is to protect the eye.

Iris: This is the part of the eye which is responsible for one's eye colour. It acts like the

diaphragm of a camera, dilating and constricting the pupil to allow more or less light into the

eye.

Pupil: The dark opening in the centre of the coloured iris that controls how much light enters

the eye.

Retina: The membrane lining the back of the eye that contains photoreceptor cells. These

photoreceptor nerve cells react to the presence and intensity of light by sending an impulse to

the brain via the optic nerve. In the brain, the multitude of nerve impulses received from the

photoreceptor cells in the retina are assimilated into an image.

Aqueous humor: The aqueous is the thin, watery fluid that fills the space between the cornea

and the iris (anterior chamber).

Vitreous humor: The vitreous humor is a jelly-like liquid that fills the cavity of the eye.

Physiological: Of, or relating to physiology.

Luminance: Luminance is the amount of visible light leaving a point on a surface in a given

direction. The light leaving the surface can be due to reflection, transmission and/or emission.

Standard unit of luminance is candela per square meter (cd/m 2).

Musculoskeletal: The structures of the body that include bones, joints and surrounding soft

tissue such as the skin, muscles, ligaments, and joint capsules.

Reflectance: Light reflectance of a surface is its property or reflecting light. The measure of

light reflectance is that fraction of the specified incident light, which is reflected by the

surface

Task lighting: Lighting designed for a specific visible operation which requires higher lightlevels; most often characterized by proximity to that task.

Glare: Light sufficiently intense to cause physical discomfort or to reduce contrast below the

level at which detail is discernible.
http://www.stlukeseye.com/popups/cornea.htmhttp://www.stlukeseye.com/popups/cornea.htm

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