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Wednesday / August 17.
HomemiophthalmologyCustomising Refractive Surgery

Customising Refractive Surgery

This year I was appointed as the Director of the Refractive Surgery Degree Course at Sydney University; the first course of its kind in the world. A reflection perhaps that refractive surgery has finally been accepted as part of mainstream ophthalmology. All feedback from the ophthalmologists who are doing the course has been positive, but one key question continually resurfaces: “How do you decide which operation is best for which patient?”

Deciding on which operation is best for which patient is a fundamental issue in refractive surgery and if the training ophthalmologists are struggling to get their head around the choices available, how can our patients come to terms with the ever increasing number of options?

In this article I will outline my opinion on what works in refractive surgery and what doesn’t; why LASIK is still usually preferred to an intraoperative procedure in but intraocular procedures are becoming a more frequently used option.

My preferences are based where possible on the Evidence Based Medicine but also influenced by 15 years refractive surgical experience and many thousands of procedures performed.

Whilst experience and technical expertise in the surgery is critical to success, the appropriate choice of operation and the correct refraction target requires nuance, judgment and an understanding of the
patient’s individual needs.

First Principles

Refractive Surgery when appropriately performed can provide patients with a significant improvement in their visual function. I never tire of hearing my patients tell me that the surgery has changed their lives and pretty much every day after my surgical list at least one patient will tell me “It’s a miracle”.

Whilst this is very satisfying, it is important to remember that the first principle in medicine is: “Primum non
nocere: First do no evil.”

The unfortunate paradox is that often in order to achieve good we must risk an adverse event. This is true in all surgery whether it be cardiac orthopaedic or refractive eye surgery. Of course in refractive surgery because it is purely elective, the stakes are higher. Consequently, whilst this surgery can not be perfectly safe, it must be as safe as we can possibly make it.. I believe and the evidence shows very clearly that it is.

A question that is often put to me is that if refractive surgery is so safe, why aren’t the doctors and ophthalmologists having it done? In fact they are. Not only have I operated on many other doctors including
ophthalmologists, I have recently had LASIK myself for mild hyperopia and presbyopia and I‘m loving it. In our practices at Chatswood and Bondi Junction, four out of the five surgeons who perform refractive surgery have had LASIK.

In the end each patient must make their own decision and their risk/benefit analysis will vary depending on age, degree of refractive error and the preferred surgical procedure.

The Options

Refractive surgery continues to evolve with exciting new developments becoming available each year. Every new procedure, whether it be laser or lens must be evaluated critically. I have been around long enough to see the next “miracle development” come and go: Conductive Keratoplasty, Thermal Keratoplasty, and
my all time favourite the fully disposable microkeratome “Flapmaker” which looked as if it came straight out of a cornflakes packet and was never used in our practice

The secret is to avoid the hype and adopt only the proven technology. Innovations are essential to improved outcomes but they should be the subject of properly constructed clinical trials. Only when proven should the technology be presented as an option to patients.

When a patient presents for refractive surgery there are two basic surgical choices: A corneal procedure or an Intraocular procedure (Figure 1).

There are two major corneal procedures: LASIK or a Surface Laser Ablation (SLA, ASLA, PRK). LASIK remains the most commonly performed refractive surgical procedure and makes up 75 per cent of my refractive practice. I will use a Surface Laser Ablation in patients where the cornea is too thin or I believe the corneal topography a little suspicious and judge that SLA is safer. SLA can be augmented with mitomycin C 0.02 per cent to reduce haze and increase the degree of myopia that can be treated but this carries its own
inherent risk.

I will treat myopia up to 8D with LASIK although the degree of possible treatment will depend on the corneal
thickness. I like to leave 300 microns of untouched stroma in the bed to reduce the risk of corneal instability
and will always perform intraoperative ultrasound pacchymetry if there is any doubt whatsoever that this level will be approached (Figure 2).

Whilst hyperopia up to 4D can be treated effectively with LASIK, I prefer the increased predictability and
stability of a refractive lens exchange (RLE) in post presbyopic patients with a refractive error of 2D or more. I do not offer myopic patients refractive lens exchange regardless of their age. I believe that at present the evidence is that these patients are at an increased risk of retinal detachment and whilst there is conjecture that older patients with posterior vitreous detachments are free from this risk, I have yet to be convinced.

There are a number of multifocal/pseudoaccommodative IOLs that work quite well in RLE, there is always a
compromise in visual quality. I will rarely use them and prefer to use mono or blended vision in those patients who wish to have both reading and distance vision. I always insist that these patients have
completed a successful contact lens trial which may take some time to assertain the appropriate target refraction. Monovision assessment is an art form in itself and should not be rushed.

Before all the ‘monovision skeptics’ scoff at my position on monovision, I wish to point out that I have a monovision correction myself and at 47, feel no need for glasses at all. My refraction is now plano OD and -1D OS. My binocular unaided vision is 6/4.5 and N5. My stereopsis down the operating microscope is perfect, I can tie my hook on my fishing line and my touch football has improved (all be it from a rather low skill level).

It is critically important however to realise that not everyone is suitable for a monovision treatment and a full distance correction is still often the best choice for presbyopic patients. Clear communication with the
referring optometrist is essential. He/she has been looking after the patient for a long time is often best placed to trial the monovision and advise on the target refraction.

One exciting new development in the management of presbyopia is the Crystalens (Figure 2). It is a true accommodating IOL and initial results in Australia are promising. It has the potential to significantly improve patient function but further follow up is necessary to ensure that the latest version does not have some of the unsatisfactory drawbacks of the earlier models.

For patients who are outside the safe treatment level for a corneal procedure (>-8D and >+4D) and are still prepresbyopic there are numerous phakic IOLs available. None are perfect and I am somewhat circumspect in offering them to patients who must take the time to understand their limitations. With that initial caveat
the results can be phenomenal. With patients having myopia of 11-16D reaching spectacle independence. The Verisyse Iris Clip IOL now comes in a toric version and the new Alcon ‘Cache’ is also proving to be very effective (Figure 3).

Whilst trained to insert the reasonable popular Staar ICL, I have never used this model and was always worried about its propensity to cause cataracts. Recent studies have validated this concern.

Finally it is important to remember that not everyone is suitable for refractive surgery. Sometimes the best option is no surgery at all. This can be very disappointing for the patient but unless the risk/benefit analysis makes absolute sense, glasses and contact lenses remain a very valid and successful alternative.

Conclusion

There is both science and art in refractive surgery. When practiced appropriately it is immensely satisfying for both patient and surgeon. The key to success is an understanding of the patient’s needs and expectations, and being able to match them with the appropriately chosen surgical procedure. As a surgeon and a patient, it has certainly changed my life.

Key Points
  • Deciding which operatioin is best for which patient is a fundamental issue in refractive surgery.
  • Patients’ risk/benefit analysis will vary depending on age, degree or refractive error and the preferred surgical procedure.
  • Proven technology: adopt it, and avoid the hype.
  • Two basic choices: a corneal procedure (LASIK or a Surface Laser Ablation) or an intraocular procedure.
  • IOLS: for patients outside the safe treatment level for a corneal procedure.
Dr. Gerard Sutton is a Clinical Associate Professor of Ophthalmogy at Auckland University, Senior Staff
Specialist at Sydney Eye Hospital and in private practice at The Eye Institute in Sydney.
His areas of expertise are Corneal, Refractive and Cataract surgery. He has published over 50 peer reviewed papers and textbook chapters. He has pioneered a number of surgical techniques in Australia. He was the first surgeon in NSW to insert an Artificial Cornea and the first surgeon in Australia to use the Intacs intrastromal ring for the treatment of Keratoconus and the first to perform LASIK with the Intralase femtosecond laser.
He was also the first surgeon in Australia to perform Penetrating Keratoplasty, Deep Anterior Lamellar Keratoplasty and Descemets Stripping Endokeratoplasty with the femtosecond laser. His research focus continues to be in Corneal and Refractive Surgery with a particular interest in the causes and treatment of Keratoconus.

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