Contact lenses are thin plastic
discs that rest directly on the cornea.
Advantages of contact
Better correction for certain eye
conditions, such as keratoconus and irregular astigmatim.
Thick glasses reduce the side vision in spectacles because the power is only at the
center. The frame also reduces side vision. This problem is overcome by contact lenses.
No fogging of vision from humidity and perspiration.
Cosmetic approach to eye problems.
Very comfortable for sportsmen.
Use of optical instruments such as microscope and camera becomes easier.
Disadvantages of contact
Cost ineffective due to damage & loss.
Requires special care.
With hard lenses wearing time gradually builds up so strong motivation is required for successful results.
Different Type of Lenses
Rigid Lenses Variety:
All the above three are same except for amount of oxygen passing through it. This is minimum in hard lens and maximum in oxycon lens. Increased oxygen permeability of the lens increases comfort and wearing time.
Rigid lenses over soft lenses
Easy to clean and maintain.
Provides better vision than soft lenses (in some cases).
Rigid lenses over soft lenses
The wearer needs more time to get used to.
Increased number of visits to the optician.
More likely to slip away from the cornea – so unsuitable for active sports.
Dust and foreign bodies caught behind the lens can cause irritation and watering.
Not suitable for part time wearer.
These are made of gel like plastic and absorbs water like a sponge, making lens more comfortable to wear.
More comfortable so fits easily.
Can be worn part time.
Does not pop out so better than hard lenses for active and sports related lifestyle.
Remains centrally located in the eyes.
Dust does not get trapped so comfortable
even in dusty atmosphere.
Requires frequent replacement – at least once in a year.
Needs proper care and cleaning.
Vision may not be as sharp as hard lenses especially with astigmatism. However these days toric soft lenses are
available for astigmatism which are even more expensive.
Soft contact lenses deteriorate over time as they become worn, dirty and accumulate protein deposits that cannot be removed even by elaborate cleaning. This can affect visual acuity and increase discomfort. There are chances of infection of the lens leading to corneal ulcer. These ulcers are difficult to treat and may lead to blindness. Most common organism responsible for ulcer is acanthamoeba.
Disposable contact lenses
Disposable lenses are soft lenses, which are replaced frequently such as daily, weekly, monthly or quarterly.
Someone who wants the best for their eyes should consider the advantages of disposable lenses
Frequent replacement of disposable lenses leads to
less deposits and eye irritation and infection. It is very
suitable for people suffering from ordinary lens related problems.
People with sensitive eyes respond better to disposable lenses, as irritation is almost nil.
Deposits also reduce oxygen permeability of soft lenses and increase the irritation because of insufficient oxygen flow.
Chances of lens related corneal ulcer is minimized
For People who tend to loose contact lenses, disposable lenses are better option as they are comparatively less
For occasional contact lens wearer this is the best alternative because it is cost-effective.
Thus we see that disposable contact lenses are best option as they provide maximum oxygen to the
cornea, keeping the eyes fresh and healthy all day long.
Special Contact Lenses
Toric contact lenses.
Bifocal contact Lenses.
Colored contact Lenses
Extended wear contact lenses
Bandage contact Lenses
Toric contact lenses
These are soft contact lenses with cylindrical power. It is expensive and limited range is available.
Bifocal Contact Lenses
Useful for presbyopes who do not want to wear glasses. It has distance and near segment. When
person looks straight his distance correction comes in optical axis and while reading and near
work the reading portion comes in optical axis.
Colored Contact Lenses
These are of 2 types:
With Clear pupillary area: Used by
nomal persons for cosmetic use. Commonly used by film and drama artists.
people with peripheral corneal opacities.
With black pupillary area: Used for total or central corneal opacities.
Extended Wear Contact Lenses
These are soft lenses that can be used for a week to one month without removing.
Have good vision throughout the day and night,
specially good for high myopes who other
wise feel miserable when get up from sleep.
Save cost and botheration of cleaning the lens.
More likely to catch infection.
Bandage Contact lenses
These are extended wear contact lenses and are used as a bandage in different eye conditions
which causes irritation such as:
Corneal oedema and Bullous Keratopathy.
Recurrent corneal ulcers.
In Small corneal perforations it is used with tissue glue to close perforation.
After eye surgeries: To give relief from surgical discomfort as after Lasik.