Conventional soft lenses, annually replaceable, are best for first-time users. The lens is thicker than the monthly disposable ones, making it easier for inexperienced wearers to identify the right side.
• New users adjust faster to them than to rigid gas permeable (RGP, earlier known as semi-soft) lenses, which are harder and smaller.
• They are cost effective.
• They are easy to fit—they come in two sizes and your optometrist will recommend one that will suit you.
• After about seven months of use, they gather enough protein and lipid deposits to inhibit oxygen flow to the cornea. Even new improved materials typically offer lower oxygen transmission than disposables or RGPs. This can cause discomfort in the long term and inability to continue lens use.
Picture from Jupiter Images
• Unless they are cleaned regularly, microbes can breed, increasing the risk of infections.
• They are difficult to clean.
Rs1,400-2,600 (the higher end of the range also provides protection against ultraviolet rays or dry eyes). Toric lenses (to correct astigmatism) are more expensive.
RIGID GAS PERMEABLES (RGPs)
Though popular when they were first launched, RGP lenses aren’t preferred as much as soft lenses now (the advent of monthly disposables reduces their key advantage—less likelihood of deposits forming). However, they are still used to correct astigmatism and keratoconus (a condition in which the cornea becomes cone-shaped).
• They are widely recommended by ophthalmologists for allowing greater oxygen transmission.
• Unlike soft lenses (up to 65% water content), they do not contain water, nor do they require it to retain their shape; hence they don’t absorb moisture from the eye, reducing the risk of dry eyes.
• There is reduced risk of infection from protein and lipid deposits in the long term.
• They do not absorb materials such as eye make-up.
• They are harder material, so new users take longer to adapt.
• They are small in size—9mm (soft contacts measure around 14mm)—so they readily move around in the eye. Any jerk or sudden movement (rapid blinking, squeezing eyes tightly shut) can shift the lens.
• A number of sittings may be required for fitting.
Tinted lenses are popular among young people—experts connect their popularity to movie stars using them to change eye colour for different roles. However, eye specialists won’t recommend them as they offer low permeability to oxygen and can affect peripheral vision. Experts also doubt the quality of novelty shapes, whcih are mostly of South Korean origin.
• There’s an element of fun: blue eyes one day, hazel the next.
• There’s the novelty factor: cat-eye lenses and those with heart-shaped spaces for the pupils.
• The darker tint along the circumference can obstruct peripheral vision, and is especially inadvisable while driving.
• They usually have a 3mm clear area for the pupil and 7-8mm of tinted area. Pupil diameter varies from person to person, so for those with larger pupils, this could result in “tunnel” vision.
• The pigments can cause allergies in some.
Disposable soft lenses are thinner than annually replaceable ones and more expensive. Monthly disposables are greater value for money than daily disposables, which waste a lot in packaging. However, daily disposables are better for swimmers, occasional users and stage or TV artists who use a lot of eye make-up.
• Greater oxygen permeability makes them more comfortable to use.
• They are less prone to accumulating protein and lipid deposits since there is a limited period of use, so the risk of infections is reduced.
• Once removed from the packaging, monthly disposables must be discarded in 30 days, regardless of how often they are worn.
• Improper care can lead to irritation, allergies and minor infections as they absorb a range of materials that they may come in contact with, including eye make-up.
• They are hard to clean because they absorb things such as eye make-up.
Monthly disposables, Rs3,000- 5,000 for a year’s supply; quarterly disposables, around Rs2,200.
Though overnight lenses are approved for all-night wear up to one month, experts do not advise more than occasional use in India.
• There’s acceptable oxygen transmission to the cornea with eyes closed.
• They are recommended for those who frequently use contacts for longer than 12 hours or spend hours before the computer.
• In India, high air pollution and dust particles act as possible irritants, and prolonged use can induce an allergic response.
• Though the risk of corneal oedema (swelling) is less than with other soft lenses, continual overnight wear may cause redness and irritation.
• They are costlier than most soft contacts.
Rs720 for a box of three lenses (minimum packaging).
BEYOND NORMAL VISION
Therapeutic uses for contact lenses range from bandaging the eye after an injury to treating large differences in magnification. Say you have a -1 dioptre error in one eye, –4 in the other. If you use spectacles, the lens for the higher refractive error shrinks the image significantly while the other lens doesn’t. So you see two different-sized images, leading to double vision. In such cases, contact lenses are better.
Contact lenses are also better for infants. Sometimes lenses are prescribed for babies as young as two months, who can’t be asked to wear glasses!
Orthokeratology or Ortho-K lenses can be used to correct refractive errors temporarily. These work while you sleep, flattening the cornea. Pressure from closed eyelids adds to this. These are only worn while sleeping and the user can go without them during the day. They are not yet popular in India because they only correct errors up to -6 dioptre and are expensive.
LET YOUR EYES BREATHE
The cornea has no blood vessels—it gets oxygen directly from the air. When protein and lipid deposits form on contact lenses over time, they reduce the oxygen transmitted through the lenses. The answer is a diligent cleaning routine.
The need for a regular cleaning routine cannot be stressed enough. The chances of contact lens users contracting infections such as conjunctivitis and corneal ulcer are increased by a lax attitude to cleaning.
How to clean
• Take the lens in the palm of your hand, add cleaning solution and rub up and down 10 times, then side to side 10 times; turn the lens over and repeat.
• Change the solution in the storage case every time you return the lenses to them.
• The storage case can be cleaned easily with a toothbrush and lens cleaning solution.
• Annual replaceable lenses can also be treated with enzyme cleaners. These are over-the-counter pills you simply add to the storage case, and the lenses—with the usual storage solution—are left in overnight.
• Experts recommend that even so-called “no rub” solutions should be rubbed in well (see above) to properly clean the lens.
Between cleaning: Check for scratches on the inner surface of the lens case. Bacteria can lodge in these crevices, so it’s time to get yourself a new case if you see these.
Pharmaceutical company Novartis AG is developing special contact lenses that could help optometrists screen patients for diabetes. The advantages of this new invention include a lower risk of infections (from needles) and early detection of diabetes. After all, optometrists may see a patient as yet unaware of a blood sugar problem.
According to the patent application filed by Novartis, a Switzerland-based company, with the US Patent and Trademark Office in February 2007, “earlier diagnosis and treatment can prevent or delay the costly and burdensome complications of diabetes… The simpler testing method (compared with the oral glucose tolerance test) of measuring fasting glucose should help identify these people so they can benefit from treatment sooner.”
Based on an analysis of tears, these lenses can even indicate whether a person’s glucose levels are only marginally above normal or dangerously high. Dr Aggarwala notes that the invention, which consists of lenses made using a glucose-sensitive material and a kit for determining glucose levels, can help people avoid the sight-threatening changes of diabetic retinopathy (a condition that affects blood vessels in the retina and can go undetected because often there are no symptoms in the early stages).
The invention is currently in patent literature, not on the market.
* All prices are indicative
EXPERTS: Karan Aggarwala, an optometrist, vision scientist and nutrition counsellor who runs Dr Karan’s Vision Care, Gurgaon; Lovely Sharma, an optometrist with Venu Eye Institute and Research Centre, New Delhi.
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Exercise can strengthen eye muscles and provide relief from fatigue, says optometrist Lovely Sharma, but can’t correct faulty vision. Dr Sharma recommends an exercise using stereogram cards. These are printed with an incomplete image (say, half a cat) and take advantage of a curious property of binocular vision—we can only focus on one object at a time. Place the card 25cm from your eyes, hold a pen against it (level with your nose) and focus on the pen as you slowly bring it towards yourself until the image appears complete. Repeat 15-20 times, twice daily, for a month. Chanpreet Khurana
Most nearsighted people and others with weak eye muscles, especially children, tend to develop a slight squint. A synoptophore is a diagnostic/therapeutic tool that can ascertain the degree of squint, exercise the muscles and develop stronger attention mechanisms. It shows you a series of slides. In the first sequence, the patient tries to superimpose two images (say, a joker on one slide, and a gate on the other). The second requires you to “fuse” two images (say, a rabbit holding a bouquet but with the tail missing and a rabbit sans flowers but with the tail intact, to be seen as a single whole image). The third stage tests and improves stereoscopic vision. If your vision is normal, you see a 3D image. This treatment is also used for a lazy eye or a considerable difference in refractive error between the eyes. You’ll need to visit your optometrist for each session. Chanpreet Khurana
Fresh fruit and vegetables eaten raw or only minimally cooked and whole grains maintain healthy vision, says optometrist Karan Aggarwala. Fruits and vegetables are rich in vitamins and minerals and antioxidants that mop up cell-damaging free radicals (produced when glucose is broken down in the body to release energy). Lycopene in tomatoes and watermelon protects against ultraviolet radiation and radiation from TVs and computers, raw spinach prevents some types of cataract and dry macular degeneration. Chanpreet Khurana
Dr Aggarwala also recommends what he calls “reiki for the eyes” daily: Rub palms together for a few seconds. Place over the eyes, centring them in the palms, and rest your head in your hands for 5 minutes. This rests the muscles and may slightly flatten the cornea, which helps those with myopia. He adds that cold compresses (a towel wrung out in ice-cold water) for 5 minutes, twice a day, can soothe minor allergies or irritation, particularly in summer. Chanpreet Khurana