Dr. Sudip Chaudhuri (MD–AIIMS, NEW DELHI) started performing Lasik surgery from 1998. Trained in lasik from Delhi,and refined by Dr Michael Knorz from Germany, He has performed over 10,000 lasik surgeries over the last 20 years.
Has a rich experience of using different lasik machines and microkeratomes over the last 20 years. Currently using Wavelight ex 500 , VIS X , Moria Microkeratome and Femtosecond laser.
The art of lasik that has been mastered today was dreamt long ago and performed by people who have dared. The Excimer laser invented by a team of scientists led by Dr. Mani Bhaumik was put into use to achieve this miracle. The constant effort for refinement and perfection , the hard work of many scientists , technicians and doctors has made it possible to perform the procedure with extreme safety and accuracy. I have an experience of performing over 10000 eyes from 1998 in Delhi (here I learnt LASIK ) , Kolkata,Guahati and Aizawl ( the only lasik centre in Mizoram as of now ). I have used various machines like technolas 117 ,217, z-100 ,nidek . Presently using wavelight ex-500 and vis-x. Among the microkeratomes-hansatome.XP , moria one use plus deserves special mention. Have come across almost all possible complications in lasik. Starting from infections,machine oil leakage,DLK, accidental thick flap (detected in postop OCT) . free flap and half flap etc.Properly managed, sight threatening complication is rare after lasik.
Lasik aims at correcting the power and reduce aberrations so that one can have a better visual quality at dim light conditions reducing glare/halos. Specially designed treatments like wavefront optimized / wavefront guided customized etc are used to achieve this.
Lasik involves 2 steps- making a thin corneal flap and after that the shaping laser reshapes the corneal bed.
Depending on the power,available corneal thickness , preoperative aberration and pupil size the type of surgery is planned. Either a standard procedure/ wavefront optimized procedure that can maintain the postoperative asphericity of the cornea and thereby controls the spherical aberration can be chosen or a wavefront guided procedure can be chosen ( customized ) which tries to reduce all the higher order aberrations like trefoil and coma etc for a better visual performance in dim /dark conditions.
It is important to save corneal tissue as much as possible. The residual corneal thickness must be over 300 microns for safety reasons. Standard lasik surgery removes about 11-12 microns for every 1 dioptre of power it corrects. A customized treatment removes little more tissue approx 15-16 microns per dioptre.
Can be done using a femtosecond laser or using a microkeratome.Both procedures are painless but a sense of intense pressure can be felt in both. The microkeratome flap is comparable to the femtosecond flap and the overall cost of the procedure can be reduced.During the process of flap making the eye pressure is raised and one may not be able to see anything for 10-15 seconds.
Intraoperative measurement of the flap and residual corneal bed is strongly recommended. Either an online pachymetry( as with wavelight ex-500) or a manual ultrasonic pachymetry is used . This procedure may not be very accurate but may help in avoiding surprises/shocks. Present generation antibiotics with better penetration also makes the procedure very safe against infections. Sight threatening complications are rare with lasik provided the safety parameters are followed.
A target light is usually given to look at.Once the laser is locked at the centre of the pupil the laser is ready to be used.laser is absolutely painless.Small eye movements are detected by the tracker and the laser adjusts itself accordingly so that the laser falls on its intended target. Accuracy of a laser machine depends on combination dynamics of the faster tracking speed and laser speed and not the laser speed alone.
Higher intraocular pressure through a longer time period compared to a Microkeratome flap making procedure chance of subclinical injury to the optic nerve.
Difficulty to retreat a patient in case of some power returning. PRK may be the only procedure possible to do. Accuracy of PRK may not be very high and a chance of slight corneal haze is there. IN A MICROKERATOME FLAP IT IS EASY TO RETREAT LIFTING UP THE SAME FLAP.
Difficulty to treat an epithelial in growth if it happens. Femtosecond laser flaps are very tightly adherent and lifting up the old flap may be complicated.
Needs more expertise to handle a Microkeratome properly . Has a definite learning curve Flap thickness may vary slightly +/- 10-15 microns with present generation Microkeratomes. But it may be safer to keep more than 300 microns as residual bed depth. On line measurements and intraop measurements should be done to avoid surprises.
A customized laser procedure may give a better visual outcome . Apart from the power , better correction of aberrations improves the quality of vision particularly at dim illuminations ( measuring preoperative aberrations gives an idea of the existing aberrations inside the eye and its implications ).
An accurate refraction matched with pentacam/oculyzer data and aberrometry data.
(Pentacam/oculyzer)- To rule out keratoconus and its subclinical forms, and gives an idea of maximum power removal possible in that particular eye.(It depends on the residual corneal thickness and the expected changed keratometry value limits-33/34D-49 D).
To assess the types of higher order aberrations.
To rule out lens subluxation and to check the retina for peripheral treatable lesions.
∗Note : GENERAL HEALTH CONDITION like presence of diabetes is also important. Schirmers test to rule out dry eye.