LASIK: The Final Answer to Refractive Errors
Dr. Mahipal S Sachdev
Senior Consultant Ophthalmology
"Invention" of spectacles was a great achievement at a time when patients with refractive error were severely handicapped or practically blind. Spectacles enjoyed high degree of popularity for a long time, but now their disadvantages viz., cosmetic blemish, restricted field of clear vision, aberrations, obstruction in sports and physical discomfort, are apparent.
A question that always haunts the mind of the ophthalmologists and patients: why depend on prosthesis when it is possible to restore natural vision with all its inherent advantages (not just cosmetic) finds no answer.
Extensive research and technical advancement have produced following alternatives:
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.
REFRACTIVE KERATOTOMY (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 cornea and thus correction of myopia. This adventurous surgery is fraught with complications, viz. perforation of the globe, infections, glare, over or under correction and weakening of the globe making it prone to rupture even by trivial trauma. Although less expensive, RK is not recommended because of its inherent risks. In fact refractive surgery has suffered a serious set back because of the complications caused by RK.
EXCIMER LASER (PRK)
Using a computer controlled LASER (mostly Argon Fluoride 193nm) the surface of the cornea can be reshaped imparting it 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 years. 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 (Laser Assisted In-situ Keratomileusis)
It seems that the final answer to the refractive errors is here. LASIK combines all the advantages of the above procedures and virtually eliminates all their disadvantages. In LASIK an ultra-thin flap of cornea is raised and then Excimer Laser is delivered to reshape the corneal stroma into desired curvature. The flap is repositioned back. The steps are detailed below.
LASIK is performed under topical anesthesia (lignocaine 4%) and the only cooperation required of the patient is to fixate at a blinking light. The steps are:
Comparison of PRK and LASIK
|Range of correction||Low to moderated (2-6 diopter)||Low to high (2-25 diopter)|
|Wound depth||Superficial||20 % depth|
|Postoperative pain||Moderate 24-48 hours||Minimal 12 hours|
|Postoperative medications||3 months possibly more||1-2 weeks|
|Functional vision recovery||3 to 5 days||12-24 hours|
|Visual results fully recognized||3 weeks to several months||1 to 4 weeks|
|Return to work||3 to 5 days||1 day|
|Risk of complications||Low (less surgeon dependant)||Low (more surgeon dependent)|
|Risk of scarring in central cornea||1-2 %||< 1 %|
LASIK is major advance in the field of refractive surgery, which combines efficacy, safety, precision and accuracy. This technique is taking us on the path that, in the past, ophthalmologists feared to tread, towards the goal of unaided natural clear vision.
(Also read Excimer Laser)