LASIK safety

SAFETY AND PRECISION IN LASIK WITH THE WAVELIGHT CONCERTO 500 HZ WAVEFRONT TECHNOLOGY

 

INTRODUCTION

LASIK an acronym for LAser in SItu Keratomileusisis is a method of re-shaping the external surface of the eye [the cornea] to correct low, moderate and high degrees of nearsightedness, astigmatism and far-sightedness. With this method one gets rid of their spectacles or contact lenses. It has been practiced in our country for the last 6 to 7 years. The latest advancement in the LASIK procedure is wavefront-guided LASIK. Wavefront procedures very often leave patients with eyesight better than normal.  In addition the best candidates tend to be those who have undergone older techniques of vision correction and have been dissatisfied with the results.

 

HOW IS WAVEFRONT LASIK DIFFERENT FROM THE STANDARD LASIK

Like our fingerprints, each of our eyes is different and has its own unique shape and visual characteristics. Wavefront Guided LASIK develops individualized software treatment plans for each eye. Unlike the standard LASIK procedure which only corrects refractive errors (myopia, hyperopia and astigmatism) and routinely achieves 20/20 vision, Wavefront LASIK goes beyond just correcting refractive errors to actually improving visual capabilities so you may see better than you did with glasses or lenses before the procedure, hence improving your ‘Visual Acuity’.

The visual system is actually capable of seeing 20/10 or better, that is letters twice as small as the 20/20 letters on an eye chart. Most people cannot see beyond 20/20 because of very subtle imperfections within their visual system. Using the Wavefront technology, it is possible to first map these subtle visual imperfections and then develops a laser treatment plan to correct them.

The key to Wavefront treatment is a device called a Wavefront Analyser or aberrometer. This projects a fine grid of 168 light beams onto the retina and captures its image using a high resolution CCV camera. This image is then compared with one from a normal eye and the difference between the two provides a “Wavefront Map” which is used to program the laser.

This means we can measure both the extent of poor vision and its causes with greater precision than it has ever been possible before.

With standard procedures there may be instances of unpredictable results where subtle internal optic errors, instead of getting treated, are further magnified. This may lead to dissatisfaction after the standard procedure of LASIK. With wavefront LASIK these errors can be corrected to achieve ideal results.

CANDIDATES FOR LASIK

Some of the common reasons why people undergo LASIK are because of contact lens intolerance, cosmetic reasons, social (marriage), tired of wearing glasses, and lifestyle activities that are inhibited due to glasses or lens wear such as outdoor sports like golf, football, water sports or hiking. Spectacles are cosmetically unappealing for some. There is a degree of distortion when looking through the periphery of the glasses, the field of vision is reduced and on leaving a cold room moisture can fog the glasses and blur vision for a few minutes. Hence glasses are unacceptable for certain careers such as the Army, Merchant Navy, Airlines, Air Force, Railways and professional sports.  Contact lenses require attention to hygiene during insertion and removal failing which sight-threatening infections may result.

Wavefront LASIK overcomes all these disadvantages.

With Wavefront guided LASIK it has now become possible to treat a larger spectrum of patients. This procedure particularly helps to have clear vision in dim light, which would have otherwise been difficult with the older procedures. Furthermore, those who have been unhappy with any form of vision correction are candidates for Wavefront guided customised treatments.

 

What is ‘wavefront’ ?

The cornea is ideally supposed to have a smooth curvature. The incident light falling upon it is in the form of a smooth curve, referred to as a ‘wavefront’.  As this smooth wavefront courses through the various parts of the eye and their imperfections, ocular aberrations are induced, which degrades the retinal image quality. An aberration-free eye would result in a smooth wavefront image on the retinal surface, reaching the best optical quality and ‘supernormal’ vision that is often significantly better than 6/6.  Wavefront-guided customized LASIK, also referred to as ‘customized ablation’ performs corrections based on individual wavefront measurements, which potentially increases the chances of better than normal eyesight.

 

Advantages of wavefront- guided LASIK over STANDARD LASIK

Recent studies indicate that

  • 100% patient satisfaction with insignificant side effects or complications.
  • 70% of these patients gained one to two lines of visual acuity more than what was expected from this treatment before the procedure.
  • 16% of wavefront-guided LASIK patients achieved a post–procedure uncorrected visual acuity of 6/3 [3 lines smaller than normal].
  • Wavefront treatment results were found to deliver stable, accurate post-operative results.
  • The incidence of post-operative symptoms such as glare, haloes, decreased contrast sensitivity and poor night vision as with standard LASIK are generally absent or greatly minimized with wavefront treatments.
  • Wavefront-guided treatment has applications in complicated post-refractive surgery (RK, PRK, LASIK) patients (with significant symptoms, decentred treatments) as well as in patients professionally requiring acute vision.

FEATURES OF AN IDEAL LASER

The WaveLight is the ultimate laser for wavefront procedures using the fastest and most sensitive eye tracker in the world [500 Hz] to ensure perfectly accurate and well-centred treatments.

This laser has the quickest treatment time [500 Hz], an important factor in ensuring uniform treatment over the entire surface of the cornea by minimizing dehydration of the cornea and other external influences during the procedure.  Additionally the Concerto customizes corneal shape not only to enhance visual acuity but also to improve contrast especially in dim light conditions.

The highly advanced WaveLight laser uses a ‘Flying Spot’ of 0.9 mm, a necessity to allow for precise placement of laser treatment. This specific treatment leaves nothing to luck or chance. Wavefront procedures very often leave patients with eyesight better than normal [super – vision or eagle vision].

The WaveLight 500 Hz Laser  saves upto 40% of valuable corneal tissue for every dioptre of treatment when compared with other lasers. This results in the doctor being able to treat a higher power range keeping in mind long-term safety as well as treating lower powers with unmatched stability.

FDA COMPARISON OF EXCIMER LASERS

dfa

In the comparison above, that the complaints of glare, night vision problems and fluctuations are very high [upto 50% patients] in one laser [Nidek], while in the rest these are very small and in the Wavelight it is almost negligible.

fda

In this comparison, one can see that as the refractive power [spectacle number] gets higher, the results of accurate 6/6 normal vision fall down with most lasers but the Wavelight results remain above 90%. These results are with the earlier generation of the Wavelight laser ie. 200 Hz. The latest laser of 500 Hz is even more accurate.

 

EVALUATION OF A CANDIDATE FOR THE LASIK PROCEDURE

A complete eye assessment is required to check a patient’s suitability for LASIK.

Tests include refraction, contrast sensitivity, pupil size, pupil reaction, retinal examination, tonometry, pachymetry, aberrometry, topolyzer measurements, topography and tests for dry eye amongst others. Patient counseling is a very significant part of the pre procedure work-up.

LASIK evaluation and screening with the topography and aberrometer determines which of the two procedures standard LASIK or wavefront LASIK would apply for the patient.

 

THE LASIK PROCEDURE

It is a pain- free outpatient procedure that usually takes 5 minutes per eye.

The actual laser treatment usually takes less than a minute. Topical anaesthetic drops are used. During the treatment, an instrument called the microkeratome creates a corneal flap. The computerized WaveLight 500 Hz Excimer laser uses a cool beam of light to gently reshape the cornea so as to alter its curvature to the desired extent.  The flap when replaced on the new corneal curvature allows images to be sharply focused on the retina.  A post-procedure eye examination with the slit lamp is performed and eye drops are prescribed.

 

RECOVERY

An improvement in vision is noticed within 4-6 hours with restoration of functional vision by the next morning. Complete recovery may take upto few weeks. 

 

SAFETY

LASIK is SAFE when performed on a suitable candidate with most of the new generation Excimer lasers. Wavefront-ready lasers are very refined. Millions of patients worldwide, who are Indian by origin, have had LASIK done on them successfully.

 

CONCLUSION

The combination of a highly advanced technology, using a laser that provides the doctor and the patient the highest level of safety, accuracy and reliability in LASIK along with the surgeon’s expertise, performed under International protocols and with International standards of hygiene is what achieves excellent results!

 

Dr ANAND SHROFF, MD