Photochromic Lenses

"Photchromic lenses are sometimes referred to as transition lenses, reactalite lenses or sunsensor lenses.
Photochromic lenses darken on exposure to sunlight and protect the eyes from ultraviolet radiation. Excessive exposure can cause permanent damage to the cornea and conjunctiva. Good photochromic lenses block out 100% of the most harmful rays of the sun, 100% of the time, adapting to changes in light and darkening in seconds.

Whilst sunglasses give comfort in very bright conditions by reducing the total amount of light and glare reaching the eye, they are not always convenient in changing light conditions and care must be taken that they meet Standard BS 2724 otherwise they won’t protect the eye from the sun’s damaging ultraviolet rays. In fact, non-UV absorbing lenses can do more harm than not wearing any protection at all because, behind a dark tint, the pupil increases in size allowing the harmful rays through."

Keep an eye on drivers’ sight - India

"An eye test carried out on 1,000 drivers in the city of THIRUVANANTHAPURAM in INDIA gave a less than encouraging result – 560 had defective eyesight.

Drivers’ defective eyesight and their rampant misuse of headlights are fast becoming a hazard for road users and a matter of grave concern for law enforcing agencies.

An eye test carried out by the National Transportation Planning and Research Centre (Natpac) in the city among 1,000 drivers revealed that 560 of them, mostly in the 40-50 age group, had defective eyesight.

According to Natpac scientist T. Elangovan, 10 per cent of the drivers had serious problems like tunnel vision, blurred vision and colour blindness.

According to a senior police official, increase in night time road accidents involving heavy vehicles is mainly due to poor eyesight of the drivers.

Other major culprits are the drivers’ reluctance to dim headlights, misuse of high-beams and use of halogen bulbs in headlights.

Two-wheeler and light motor vehicle drivers often complain that they get blinded by the high-beams used by luxury buses and heavy vehicles, especially those transporting cargo. High-beams are banned in the city. But, all four-wheelers and heavy vehicles prefer to move with the high-beam switched on.

There have also been several instances of two-wheelers and cars colliding with traffic dividers and lamp posts after the drivers are momentarily dazed by the high-beam from the approaching vehicles.

Many vehicles, especially luxury buses, install additional powerful headlights after getting the vehicle registered. The additional lights are removed when the vehicles are taken for CF (Certificate of Fitness) test, Motor Vehicle Department officials say."

Treatment For Squint

"Treatment varies accordingly to the type of squint. An operation is not always needed. The main forms of treatment are:

• Spectacles - to correct any sight problems, especially long sight.
• Occlusion - patching the good eye to encourage the weaker eye to be used. This is usually done under the supervision of an orthoptist.
• Eye drops - certain types of squint can be treated with the use of special eye drops.
• Surgery - this is used with congenital squints, together with other forms of treatment in older children, if needed. Surgery can be performed as early as a few months of age."

What Causes A Squint

"There are several types of squint. The cause is not always known, but some children are more likely to develop it than others. Among the possible causes are the following:


Congenital squint
Sometimes a baby is born with a squint, although it may not be obvious for a few weeks. In about half of such cases, there is a family history of squint or the need for spectacles. The eye muscles are usually at fault. If squint is suspected, it is important that the baby be referred for accurate assessment at the earliest opportunity. Sometimes a baby has what is known as ‘pseudo squint’ which is related to the shape of the face and this does not require any treatment, but a baby with a true squint will not grow out of it and requires careful assessment and due treatment.

Long sight (hypermetropia)
Long sightedness can sometimes lead to a squint developing as the eyes ‘over-focus’ in order to see clearly. In an attempt to avoid double vision, the brain may automatically respond by ‘switching off’ the image from one eye and turning the eye to avoid using it. If left untreated, a ‘lazy eye’ (amblyopia) may result. The most common age for this type of squint to start is between ten months and two years, but it can occur up to the age of five years. It is usually first noticed when a baby is looking at a toy, or at a later age when a child is is concentrating on close work, such as reading.

Childhood illnesses
Squint may develop following an illness such as measles or chickenpox. This may mean that a tendency to squint has been present but, prior to the illness, the child was able to keep his or her eye straight.

Nerve damage
In some cases a difficult delivery of a baby or illness damaging a nerve can lead to a squint."

Squint

"A squint (also known as a strabismus) is a condition that arises because of an incorrect balance of the muscles that move the eyes, faulty nerve signals to the eye muscles and focusing faults (usually long sight). If these are out of balance, the eye may turn in (converge), turn out (diverge) or sometimes turn up or down, preventing the eyes from working properly together.
Squint can occur at any age. A baby can be born with a squint or develop one soon after birth. Around 5 - 8% of children are affected by a squint or a squint-related condition, which means one or two in every group of 30 children. If a child appears to have a squint at any age from six weeks onwards, it is important to seek professional advice quickly. Many children with squints have poor vision in the affected eye. If treatment is needed, the sooner it is started the better the results.
Squint can be a complex condition and not every situation is covered here. Your optometrist will be pleased to give further advice, if needed. Children will benefit from support and encouragement during treatment and you should not be afraid to ask questions which will help you understand the condition. The successful outcome of treatment depends upon everyone co-operating."

High-index and aspheric lenses

"If you need high-powered lenses you can improve the weight or appearance of your glasses with special lens materials and designs. High-index lens materials and aspheric designs mean that lenses can now be made thinner, lighter and better looking than traditional lens types. High-index materials and aspheric lens design make lenses for short sight and long sight thinner and allows more optimal vision through the lens area away from the centre of the lens"

VDU's and Your Eyes - Prescription Glasses

"Only a small proportion of users will need spectacles specifically for working at a VDU and the majority of these will be what is known as presbyopic. Presbyopia affects us all as we get older. Around the age of 45 people begin to find they lose the ability to focus on objects that are close up.

Spectacles with single vision, bifocal or varifocal lenses can all be used successfully for VDU work. Contact lenses are also suitable, but wearers should try to blink regularly which keeps the lenses comfortable.

When you concentrate on the screen for long periods, your normal blinking rate slows down. Presbyopic contact lens wearers may need additional reading glasses.


Reflection-free lenses
Reflection-free lenses are well worth considering for VDU users. Because they eliminate almost all reflections VDU glare is considerably reduced, providing clearer and sharper vision."

VDU's and Your Eyes

"The following precautions can lead to eye strain relief caused by VDU work:

Take frequent breaks
When you work at a VDU your eyes can be focused on the screen for long periods so it is important to take a brief rest and give your eyes a break every 20 minutes or so. You should have sufficient space behind the screen for you to be able to look beyond it and relax your eyes.


Screen settings and position
You should adjust your VDU to levels of brightness and contrast that you find comfortable. Keep the screen clean and free of dust and fingermarks. If possible, position it so that windows or other light sources are to the side rather than in front or behind it – if you can see a window or light unit reflected in the screen, move the VDU until the reflections disappear, or adjust blinds or curtains. The surface of the screen should be between 33 and 100cm from your eyes and if you are working from copy documents these should be placed at roughly the same distance to avoid continual re-focusing.


Lighting
Try to eliminate as much glare as possible from the region around your screen. This is not always straightforward, but as a general rule:

•The office lighting should be set at a level which allows the documents and screen to be read easily. Additional lighting – such as an Anglepoise lamp – may sometimes be necessary to achieve this.

• Avoid an uncurtained window directly in front of or behind your working position

• Any window reflected in the screen should be fitted with blinds or curtains

• Walls and desk surfaces should be non-reflective and neutral in colour

Anti-Reflective Glasses

Use anti-reflective lenses when using/wearing glasses for VDU work. This reduces eye strain."

VDU's and Your Eyes

"Although there is no reliable evidence to suggest that even long-term intensive use of VDUs is damaging to the eyes, it is true that VDU users tend to complain of eye strain more than non-users. This is likely to be due to fatigue through causes such as:

• Insufficient and infrequent rest periods

• Incorrect positioning of the screen and/or documents

• Unsuitable lighting

• Poorly designed work area

• An uncorrected eyesight fault such as long sight, short sight, astigmatism or presbyopia

• The eyes not working together comfortably.

Any of these conditions could lead to fatigue; all can be overcome through good design of the working environment and by regular eyecare."

Hyperopia (long sight), long sighted glasses

Hyperopia also known as long sight is a visual disorder where the focusing power of the eyes is not strong enough. People who suffer from hyperopia or long sight have difficulty seeing up close.

Causes of Hyperopia

Hyperopia or Long sight is where light rays are focused behind the retina, rather than directly on it. Hyperopia is usually caused by a short eyeball or a flatness of the cornea resulting in the inability of the lens to focus the light rays directly on the cornea.

Diagnosis of Hyperopia

Hyperopia can cause headaches, eyestrain and people who suffer form hyperopia may squint or feel fatigued when performing work at close range. This will be indicated by your optometrist when your eyes are tested.

Treatments for Hyperopia

Hyperopia can be corrected with glasses, contact lenses and refractive eye surgery.
The choice of treatment should be discussed with your eye care practitioner. The most suitable form of correction will depend on your prescription and lifestyle requirments."