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LASIKor Laser-assisted in situ keratomileusis - commonly known as laser eye surgery or laser vision correction.
Refractive Corrective Surgery
astigmatism
Hyperopia
myopia
Facts
LASIK surgery performed by ophthalmologist. Reshaping of the cornea of eye done by laser or microkeratome. LASIK provides permanent alternative to eyeglasses or contact lenses. Till 2009 28 million LASIK procedures had been performed worldwide. Photorefractive keratotomy (PRK) is another corrective surgical
procedure for refractive errors in eye. People with very thin cornea or very high myopia cannot undergo
LASIK or PRK but can get implantation of phakic intraocular lens.
Risk
The potential risks and effectiveness were evaluated by the British National Health Institute for Health and Clinical Excellence in 2006 and it was stated “current evidence suggests that photorefractive surgery for the correction of refractive errors is safe and efficacious for use in appropriately selected patients.”
Surveys of LASIK in 2008 reports satisfaction of 92 to 98 percent. Data from 1998 till 2008 showed 95.4 percent patient satisfaction (American Society of Cataract Refractive Surgery).
Moris Waxler, former FDA official involved in LASIK approval claimed that procedure had a failure rate of more than 50%. But the same was denied by the FDA.
Small percentage of patients may need another surgery. And some may require to use glasses or contact lenses even after treatment.
Presbyopia: A condition in old age in which one or both the eyes show diminished ability to focus on near objects. This may be due to loss of elasticity of the crystalline lens.
A type of Lasik called Presbylasik, can prove helpful for correctionof visual acuity in presbyopia.
Risks
Loss of vision due to infection: The risk of vision loss due to infection is greater in contact lens wearers(1:2,000) than in infection from
LASIK( 1:10,000)
Higher-order aberrations: these are visual problems requiring special diagnosis and cannot be corrected with normal spectacles.
There has been observed correlation between size of pupil and aberration, occurring more at night when size of pupil is greater.
Light passes from the edge of flap and gives rise to aberrations that are spherical in nature.
Aberrations have also been proposed to be pre-operative and have very small size of the order of micron and could not be corrected with
laser beam which are nearly 1000times larger (0.65mm)
Dry eyes: few patients experience a dry eyes after LASIK. Although this condition may be temporary but it can develop into a dry eye
syndrome. Treatments: Artificial tears, Prescription tears, Punctual occlusion.
Punctual Occlusion: technique of plugging the tear(puncta) duct with collagen or silicone device and preventing drainage of eye.
Some patients may not experience any relief despite treatments and develop permanent dry-eye syndrome.
Individuals with pre-existing dry-eye conditions such as Sjogren’s syndrome should not be treated with LASIK.
Halos, starbursts and bright lights are experienced by some post-LASIK patients. The widening of pupil in low light conditions cause it to be largerthan the flap. The stromal changes in the passage of light cause visual distortion of light experienced in form of halos.
The pre-operative examination of eyes for wider pupils can reduce risk of this complication.
Other complications include Flap complications (0.244%) displaced or folded flaps, epithelial ingrowth).
The risk dexreases with increased physician experience. Slipped flap- when corneal flap detaches from the rest of the cornea. Patients
are given sleep goggles to prevent them for dislodging the flap during sleep. Short operation time decreases this risk as the flap does not dry easily.
Traumatic flap dislocations have been reported even after 7 years of LASIK. Flap interface particles: various sized particles with different reflectivities
(38.7% cases). Infection: (0.4% cases) Post-LASIKcorneal ectasia: a condition where cornea bulges forward after
LASIk resulting in irregular astigmatism.
Subconjuctival haemorrhage: Reportedly in 10.5% cases. Corneal scarring: permanent problems with cornea’s shape making it difficult
to wear contact lenses. Retinal Detachment: reportedly in 0.36% cases. Uveitis: 0.18% Decrease in atmospheric pressure at higher altitudes has not been
demonstrated as highly dangerous to post LASIk patients but some people experience myopic shift at very high altitudes.
Complications may be categorised as pre-operative, intra-operative, early post-operative or late post-operative. According to UK National Health Service, these occur in less than 5% cases.
The risks andbenefits of the LASIK refractive procedures should be weighed based on the personal value system and bias should be avoided through not getting influenced by other’s having undergone the procedure.
The procedure consists Creating a thin flap Folding it to enable remodelling of underlying tissue with laser Repositioning the flap
Pre-operative proceduresPatients who used soft contact lenses are required to stop wearing them from 5 to 21 days before the surgery.Those wearing hard contacts should stop wearing them 6 weeks prior to the surgery. The duration should be increased by 6 more weeks for every 3 years of wearing hard contacts. The cornea should be sufficiently avascular before the surgery. The contacts which prevent oxygen supply to cornea lead to neo-vascularisation and this can cause greater bleeding, pain in surgery.
Patient’s eye prescription should be stable or at least one year prior to surgery. The patient’s cornea are examined with a pachymeter to their thickness. Using low-power lasers, a topographer creates a topographic map of cornea.
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