Eyesight : Spectacles
Alternatives to spectacles: There are four main options available to overcome the disadvantages of spectacles:
Contact Lenses
These are small polymer lenses, which are placed directly over the cornea. They are of two main types — soft and semi soft. Soft contact lenses are pliable and therefore very comfortable, but require utmost meticulous care and maintenance. Infections and allergy (GPC : giant papillary conjunctivitis) are the likely complications. Semi soft lenses (or Rigid Gas Permeable) are rigid and thus, initially, slightly uncomfortable to wear, but they do not require too much care. Complications like infection and allergy are uncommon with these lenses. However, in the Indian context infection, GPC, mishandling, dust and pollution associated conjunctivitis continue to be major causes of contact lens intolerance. Patient compliance is generally not satisfactory relating to the lens care and maintenance schedules.
• High degree of astigmatism cannot be corrected by contact lenses.
• Extended wear lenses are not suitable for Indian conditions.
• Hard lenses are obsolete and should not be used as they prevent oxygen supply to the cornea.
Refractive Kartotomy (RK)?
This is an operation where 4 to 8 (rarely 16) incisions are made on the cornea using a diamond knife. This results in flattening of the complications caused by RK.
Excimer LASER (PRK) technique
Using a computer controlled LASER (mostly Argon Fluoride 193 nm) the surface of the cornea can be reshaped imparting a predetermined curvature. This leads to correction of both myopia and hypermetropia, and also moderate amount of astigmatism, the procedure is short and simple and being computer controlled is highly accurate. The patients suitable for PRK are the ones above 18 years of age, with refractive error between 1 to 6 D and whose error has been stable for the last 1 year. There should not be any other complicating factor or disease in the eye. PRK, although a little expensive, is relatively safe in comparison to RK. The complications are postoperative pain (due to removal of epithelium during surgery), prolonged healing time and need to use steroids, slight corneal haze and late regression of the effect seen in some patients. It is not useful for high refractive errors and high astigmatism.
LASIK is an acronym for Laser Assisted In-situ Keratomileusis.
It combines all the advantages of the above procedures and virtually eliminates all their disadvantages. In LASIK an ultra-thin flap/ layer of cornea is raised using an automated cutting device called the microkeratome, and then Excimer laser is delivered to reshape the corneal stroma (inner layer of cornea) into desired curvature. The flap is repositioned back where it self seals without any stitches.
Tags: color blindness, contact lenses, eye care, poor eyesight