The role of the new wavefront technology in removing spectacle numbers

The role of the new wavefront technology in removing spectacle numbers

 

INTRODUCTION

Mary Jones, a bank executive from Washington D.C., was in Mumbai on deputation from an American bank. Sitting on the computer was drying out her contact lenses and she had developed an allergy to her contact lenses. After surfing on the Internet she read up about how a new technology called ‘wavefront’ was vastly improving quality of vision, night vision and doing away with side-effects caused by earlier laser technologies.

After conducting a series of tests on her eyes, she was shown how the wavefront procedure not only takes off the spectacle ‘number’ but also treats faults in the optical system of the eye, which leads to crisp vision.

She underwent the painless procedure of about 7 minutes an eye. The next morning her sight was ‘normal’ and she read 1 line more than she ever could.

Moiz Bhiwandiwala, a 34-year-old exporter had a very high spectacle prescription 8 years ago. He had heard of the “Russian technique” called Radial Keratotomy, which involves making cuts on the cornea to decrease the number. Not only did his number return but the unequal healing of the cuts led to an asymmetrical shape of the cornea and very severe glare and haloes at night. He heard of the topography-linked customized re-treatment through a friend.

A topography [computerized mapping of the cornea] was done and the irregularities found were fed into the laser through a software link. His irregularities were smoothened out and the cornea returned to its natural shape. Today he is able to drive at night and perform activities requiring fine vision without any difficulty.

These treatments have revolutionized the way laser vision correction treats eyes with numbers through the wavefront procedure or eyes that have undergone past treatment with topography-linked re-treatments. Today’s environment of high visual needs have treatment options that can result in very high standards of vision, sometimes even improving the vision by a line or 2.

Like our fingerprints, each of our eyes is different and has its own unique shape and visual characteristics. Wavefront Guided LASIK develops specific software treatment plans for each eye. Unlike the standard LASIK procedure which only corrects refractive errors (myopia, hyperopia and astigmatism) and routinely achieves normal 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.

 

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. More importantly, the above tests also very accurately help in deciding who are the persons unfit for undergoing laser vision correction.

 

CANDIDATES FOR WAVEFRONT-GUIDED 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 contact lens wear such as outdoor sports like golf, football, water sports or hiking. 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.

 

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 passes through the various parts of the eye and their imperfect optical parts, the wavefront gets distorted, degrading the retinal image quality. A treated eye has much fewer or no optical errors, resulting 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

  • Very near 100% patient satisfaction with very rare side effects or complications.
  • Nearly 60% 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 vision].
  • Wavefront treatment results were found to deliver stable, accurate post-procedure results.
  • The incidence of post-procedure 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 [400 Hz] to ensure perfectly accurate and well-centred treatments.

This laser has the quickest treatment time [400 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 Allegretto 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 0.68 mm HM, 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 Allegretto 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.

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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 Concerto laser is even more accurate.

 

THE LASIK PROCEDURE

It is a pain- free outpatient procedure that usually takes 5-10 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 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 48 hours.

 

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!