Patients guide to contact lens


Contact Lenses are thin curved discs of plastic to be placed on cornea for various reasons

  • to correct and improve defective vision due to refractive error
  • for bandaging the eye after surgery or corneal disease
  • cosmetic benefits e.g. to cover white scarring of the eye or to change the color of the eye as a fashion statementContact lenses are a safe, comfortable, convenient and affordable alternative to spectacles if we ensure proper care and handling of contact lens.

 

Types of Contact Lens:
There are basically two types of contact lenses: Rigid and Soft. Both types come in varying materials with different levels of oxygen permeability. The higher the oxygen permeability the better it is for the eye.

 

Rigid Gas Permeable (RGP) RGP lenses are semi-rigid lenses made usually from acrylate and fluorosilicon, a plastic which allow oxygen through to the eye. They are clinically very good as they allow maximum oxygen to reach the cornea being smaller in size.

They are easy to care for, durable and give good clarity of vision. They can be prescribed for all types of vision correction, including high astigmatism, bifocals, post refractive surgery, therapeutic, and cosmetic for all age groups. Rigid gas permeable lenses are very durable and may last for several years without the need for replacement.In certain cases these lenses are also prescribed for myopia control (orthokeratology).Few doctors practice orthokeratology, the correction of myopia by deliberate overnight flattening of the cornea with tight RGP contact lens, leaving the eye without contact lens or eyeglasses correction during the day.

Soft lenses are made from water-absorbing plastics, which make them pliable and membrane-like for maximum comfort. They are ideal for easy comfort wear and sports as they cannot be easily dislodged from the eye.New silicon based soft lenses allow maximum oxygen to the cornea, enabling overnight continuous wear safely for a month. Soft lenses are available in toric (to correct astigmatism) andbifocal (to correct both distance and near correction). Toric lenses are usually marked with tiny striations to assist their fitting. They are usually more expensive then routine soft lens.

 

Disposable Soft Contact Lens:
Daily, Weekly, Monthly, and Three Monthly- The advantages of this system of prescribing is that, frequent infections due to protein deposits and environmental pollution are almost eliminated, the eye gets more oxygen and simple cleaning systems like multipurpose solutions can be used safely.

Colored Soft Contact Lens:
They are also used for cosmetic purpose to cover corneal scars, as well as to change the colour of one's eyes as a fashion statement. These are as safe as other routine lens if one ensures proper handling and care.

Therapeutic contact lenses:
Soft lenses are often used in the treatment and management of non-refractive disorders of the eye. A bandage contact lens protects an injured or diseased cornea from the constant rubbing of blinking eyelids thereby allowing it to heal.[29] They are used in the treatment of conditions including bullous keratopathy, dry eyes, corneal ulcers and erosion, keratitis, corneal edema, descemetocele, corneal ectasia etc, Contact lenses that deliver drugs to the eye have also been developed.

 

 

Extended Wear contact lens:
These are used for continuous overnight wear. Newer materials, such as silicone hydrogels, allow for even longer wear periods ,are often called as continuous wear (CW). These are increasing in popularity, due to their obvious convenience. Extended- and continuous-wear contact lenses can be worn for such long periods of time because of their high oxygen permeability (typically 5-6 times greater than conventional soft lenses), which allows the eye to remain remarkably healthy. Extended lens wearers may have an increased risk for corneal infections and corneal ulcers, primarily due to poor care and cleaning of the lenses, tear film instability, and bacterial stagnation. The most common complication of extended lens use is conjunctivitis, usually allergic or giant papillary conjunctivitis

 

Handling and care of contact lens:

  • All types of contact lenses should always be kept clean, disinfected and soaked. Lens hygiene is the key to a comfortable wear. All contact lenses accumulate a variety of deposits, from the eye itself whilst wearing them, and from the environment.
  • Daily cleaning by rubbing in the palm of the hand with a surfactant cleaner is important (not applicable for daily disposable ones)
  • Contact lens wearers must take their lens out every night and soak them in fresh multipurpose solution- used for rinsing, disinfecting, cleaning and storing the lenses.
  • Before touching the contact lens or one's eyes, it is important to thoroughly wash & rinse hands with a soap that does not contain moisturizers or fragrances.
  • Long fingernails can damage the lens, so care should be taken.
  • Weekly protein/enzymatic cleaning- used for cleaning protein deposits off lenses,available in tablet form
 

 

Contact Lens Fitting and Trial:
It is always best to get initiated on contact lens under proper care of an ophthalmologist or trained optometrist.Each eye needs to undergo a detailed evaluation and is then accordingly advised which lens would suit him best. Corneal health is verified; ocular allergies or dry eyes are detected to determine a person's ability to successfully wear contact lenses.
The parameters specified in a contact lenses prescription may include:

  • Material (eg. Oxygen Permeability (Dk/L, Dk/t), water content)
  • Base curve radius (BC, BCR)
  • Diameter (D, OAD)
  • Power in dioptres - Spherical, Cylindrical and/or reading addition,Cylinder axis

 

Complications associated with contact lens wear:
Excessive wear of contact lenses, particularly overnight wear, and poor hygiene is associated with most of the safety concerns. Never ignore any redness,itching,watering if you are wearing contact lens and seek advice from the ophthalmologist.

Few complications of contact lens are Giant papillary conjunctivitis-allergic ,Superior limbic keratoconjunctivitis-dry eye ,Corneal abrasion, Corneal ulcer - keratitis etc.These are not common and can be easily avoided with proper handling and care of your lenses.