A different view of aesthetic eye health

Change your look by eliminating glasses with lasers
THE REVOLUTION IN REFRACTIVE SURGERY

Jean-Pierre ROZENBAUM, MD Ophthalmic surgeon specializing in refractive surgery
Member of the French National Academy of Surgery

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Introduction

Laser refractive surgery has been practiced since the 1990s. It can correct the majority of visual defects: myopia, hyperopia, astigmatism and, to a certain extent, presbyopia.
Removing corrective lenses not only has a functional, but also a psychological effect. It enhances the look of the eyes.
This has a major positive and energizing effect. Young people feel more self-confident in their contacts with others, and playing sports is easier. Older people feel younger when they don't need corrective lenses to read.
The feminine look, illuminated by make-up, is no longer concealed by corrective lenses.
During the COVID period, we noticed the importance of the gaze in the absence of glasses, when the mask hid part of the face.
Corneal laser refractive surgery involves modifying the curvature of the cornea by a few tens of microns.
The treatment lasts 10 to 15 minutes for both eyes, and is performed under local anesthetic eye drops. 
Depending on the technique, results can be achieved in a few hours or a few days. The choice of technique will depend on the defect to be treated and the patient's ocular anatomy. 
The most important thing is to achieve the visual result and minimize any risk to the patient.
The results of this surgery are excellent and the risks exceptional in experienced hands that respect the contraindications. Rigorous pre-operative examinations will eliminate corneas that are too thin or show signs of fragility, as well as family or personal histories that contraindicate laser refractive surgery.

ANATOMY OF THE CORNEA

The cornea is a transparent tissue that forms the front wall of the eye. Its average thickness is 540 microns. It acts as a high-power converging lens (42 dioptres on average). The power of the cornea is linked to its curvature. There are no blood vessels (avascular). However, there is significant innervation from the Trigeminal nerve.
 A 0.4 millimeter change in the radius of curvature obtained by the laser provides a correction of 2 diopters, and corresponds to a "surfacing" depth of 35 microns.
Today, we offer 3 main types of laser procedure.
  • The Excimer laser, called "PRK" or "TPRK". This is a "surface" laser used to perform photorefractive keratectomy. By acting directly on the surface of the cornea, it corrects the visual defect by slightly shaping the curvature of the anterior surface of the cornea, over a few tens of microns.
  • "The FemtolasikCorneal sculpting is performed after a 100-micron-thick corneal film has been produced, thanks to Femtosecond laser.
  • "Le Smile : uses Femtosecond laser to create a lenticule in the very thickness of the cornea, which will be extracted through a 2-mm buttonhole. The removal of this lenticule will modify the anterior curvature of the cornea.
If the patient presents a contraindication to refractive laser treatment of the cornea, a phake intraocular implant may be proposed.
This is a very thin corrective lens inserted into the eye through a small 3-mm incision and placed in front of the crystalline lens.
This technique can be used to correct very high myopia and astigmatism levels that are inaccessible to laser treatment. There are both good indications and contraindications.

VISION DEFECTS

Vision analysis: we distinguish between distance vision beyond 5 meters (driving, television), intermediate vision at 65 to 80 cm (computer) and near vision at 35 cm.
A vision defect is measured by the strength of the corrective lens needed to correct it. There are 4 types of defect:
  1. Myopia:
Without correction, myopes have difficulty seeing at a distance and little difficulty seeing at close range. With high myopia, they have to get very close to the text. Anatomically, this means that the eye is too long in relation to the curvature of the cornea. The focal point is in front of the retina. Myopic corrective lenses will reduce the apparent size of the eyes, making them appear smaller behind the glasses.
  1. Hyperopia:
The visual discomfort associated with hyperopia increases with age. This defect, which is present from childhood, can go unrecognized for a long time, and is only discovered around the age of 30-40, when there are early difficulties with near and then distance reading.  
 If there is a history of severe hyperopia in the family, children should be examined before the age of 5. High uncorrected hyperopia can lead to a visual development deficit in one of the 2 eyes (amblyopia).
Anatomically, hyperopia corresponds to an eye that is too short in relation to the curvature of the cornea. The point of focus is behind the retina, and the patient must make a constant effort to focus (accommodation), which leads to visual fatigue in intermediate (computer) and close-up reading. Hypermetropic corrective lenses magnify the apparent size of the eyes.
  1. Astigmatism:
This is the result of an ovalized shape of the corneal profile, which ideally has a spherical curvature. This leads to the formation of 2 main focal points. To compensate for this defect, the astigmatic will have to make a constant effort to accommodate between these 2 focal points, an effort that will lead to headaches in the absence of correction.
Astigmatism is often associated with myopia or hyperopia.
  1. Presbyopia:
At birth, the eye has the ability to focus on an image at any distance. This property, called accommodation, is very important in the first years of life, and gradually diminishes. People generally notice difficulty with near vision after the age of 40. However, hypermetropes are affected earlier. The effects of presbyopia increase until around the age of 60, necessitating the use of progressive corrective lenses, which are not always easy to tolerate when you spend a lot of time at the computer.

LASERS AND CORNEAL REFRACTIVE SURGERY

In corneal refractive surgery, there are 2 types of laser with different properties:
  • The Excimer laser which shapes the anterior surface of the cornea using a photoablative tissue effect with impacts of less than 1 millimeter.
  • And the Femtosecond laser which produces cleavage planes with a precision of just a few microns.
1. The 193 nm Excimer Laser 
In use for over 30 years, this laser is used to shape the surface of the cornea and obtain the curvature required to correct the vision defect. It is used in 2 related procedures: K.P.R (photorefractive keratectomy) and T.K.P.R (Trans KPR).
The Excimer laser (UV 193 nm) emits small, juxtaposed spots less than 1 mm in diameter, which are used to obtain the desired curvature by photoablating corneal particles.
  • The very fast frequency of these spots (1000 Hz) enables treatment in less than a minute. The visual defect to be corrected is programmed into the laser's computer.
  • The action of the 193 nm Excimer laser is purely localized to the treated area. The cornea absorbs all the energy, and adjacent tissues are not affected by the laser.
  • To treat myopia, laser sculpting will reduce the curvature of the cornea, while to treat hyperopia or presbyopia, it will increase it.
  • For astigmatism, the oval shape of the cornea is regularized to make it spherical.
Excimer K.P.R and T.K.P.R laser procedure.
The operation is performed under local anaesthetic, obtained by instilling a few drops of tetracaine eye drops. The precise procedure is completely painless. A blepharostat is used to keep the eyelids open. The patient stares at a small spot of light for around 30 seconds. The treatment is carried out under the microscopic control of the surgeon, and a laser-servo tracking system ensures that the patient is correctly fixed and that the treatment is centered.
Treatment takes less than a minute.
Visual recovery and post-operative follow-up
This technique offers the advantage of safety and excellent results. It alters the biomechanics of the ocular wall very little, and is recommended for occupations or sports where there is a risk of trauma. (Police, military, contact sports, etc.). It is also indicated when preoperative analysis reveals an operable cornea whose thickness or regularity are incompatible with the Femto lasik technique.
The disadvantage of this technique is the maximum post-operative pain on day 1, which is like sand in the eyes, but which diminishes from day 2 onwards, as well as the post-operative visual disturbance which lasts about 2 days.
Visual recovery takes a few days. Patients will need to organize their work. A patient operated on Tuesday will generally be able to return to work on the following Monday.
In short, this is a safe and rapid technique, the advantage of which is that it modifies corneal biomechanics very little.
This is the indication of choice for a patient who is operable but has a contraindication to surgery. femtolasik or who practice a profession or sport exposed to traumatic risks.
The results of this technique are excellent, but it has the disadvantage of causing post-operative discomfort and visual recovery within a few days.
Experience shows, however, that patients quickly forget this initial discomfort, given the satisfaction of doing without glasses.

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2/ The Femtolasik 

Lasik was a major revolution in refractive surgery in the 2000s. It offers the advantage of visual recovery within a few hours. Post-operative discomfort, such as the sensation of a foreign body, disappears within a few hours.
Patients can resume their activities without glasses the day after the operation.
Femto lasik requires the use of 2 lasers in the same procedure: the Femtosecond laser and the Excimer laser.
How Femtolasik works
The ultra-short-pulse Femtosecond laser has earned Professor Gérard Mourou the 2018 Nobel Prize in Physics.
The operation is performed under local anaesthetic using an anaesthetic eye drop. It lasts around fifteen minutes for both eyes. The first phase is performed using a femtosecond laser, which produces a 0.1 mm-thick corneal film that remains attached to the cornea by a hinge, in around ten seconds.
This film is pushed back to allow the Excimer laser to shape the corneal curvature. The film is then replaced in its original position, and adheres to the surface within a few hours.
Patients should not rub their eyes after the operation.
The operation takes around 15 minutes and is painless. Each laser phase lasts around 15 seconds.
The major advantage of the Femto lasik technique is rapid visual recovery. Its disadvantage is that it requires a sufficiently thick cornea, as it is more tissue-consuming than PRK, and a corneal shape whose biomechanical fragility must be ruled out by pre-operative topographical analysis.

3. The Smile Femtosecond Laser

This technology, developed in 2004, uses a femtosecond laser to create a lenticule inside the cornea.
This lenticule is extracted through a 3 mm micro-incision.
This painless procedure lasts around 15 minutes for both eyes, and is performed under local anaesthetic via instillation of anaesthetic eye drops.
Removal of this internal lenticule will result in a change in the anterior curvature of the cornea, and visual recovery within a few hours.
The indications and contraindications for this technique are the same as for femtolasik. It is contraindicated for corneas that are too thin or present incompatible irregularities.
This technique is used to treat myopia and is beginning to be used for hyperopia.
The advantages and disadvantages of this technique are linked to the narrowness of the incision.
While this technique spares the afferent nerve branches and limits the risk of untimely post-operative eye rubbing, it is more surgical, requiring the lenticule to be cleaved in the corneal thickness and perfectly removed through the mini-incision.

INDICATIONS AND PRE-OPERATIVE EXAMINATIONS

The results of this surgery are excellent, and accidents are exceptional in experienced hands that respect the contraindications.
Current techniques model the anterior surface of the cornea. This thinning requires careful preoperative examination.
Corneal topography, which assesses the curvature and thickness of the cornea, will enable us to eliminate high-risk patients and select the best indication for operable patients based on these same parameters, as well as their professional occupations and lifestyle.
History contraindicating corneal laser refractive surgery:
  • A family history of keratoconus should be reported, as this constitutes a contraindication. Keratoconus is a biomechanically fragile disease of the cornea.
  • History of ocular herpes
  • Severe dry syndromes (Gougerot-Sjogren's disease).
Temporary contraindications:
  • Evolving visual defects that have not stabilized.
  • Treatment with Roaccutane (isotretinoin), which causes dry eyes.
  • Pregnancy is not an absolute contraindication, but hormonal changes, particularly after the 5th week, should postpone the operation.
In fact, myopia may increase slightly and transiently, leading to a slight overestimation of the visual defect to be treated preoperatively. A tendency to dry eyes can also be observed from the 5th week of pregnancy and during lactation.
However, these phenomena are very limited. A patient who learns of her pregnancy after the operation need not worry. The ophthalmologist will have verified the stability of her visual defect in the pre-operative examination, thus eliminating the risk of over-evaluation.
In the event of dry eyes, instillation of moisturizing eye drops will usually provide a solution.
In the event of pregnancy, it is therefore advisable to postpone the procedure and carry it out a few weeks after the end of any breast-feeding.

WHICH VISUAL DEFECTS CAN BE TREATED?

Developments in laser technology over the past 20-30 years have produced excellent results, enabling patients to dispense with glasses and brighten their eyes. Indications are virtually the same for all procedures.
Because of professional obligations and the desire to regain good vision with limited discomfort within a few hours, the surgeon will first check whether femtolasik or Smile can be proposed. If these procedures are not feasible, T.P.R.K. or P.R.K. will be proposed. Patients with contraindications cannot be operated on using the laser procedure.
The ophthalmologist looks for the optimal solution for the defect to be treated, and the one that is safest for the patient.
  • Myopia from -0.75 diopters to -9.00 diopters: the possibilities will depend on the thickness and curvature of the pre-operative cornea. Myopia is often associated with astigmatism, which is treated at the same time.
  • Hyperopia from +0.50 dioptres to +4.00 dioptres.
  • Presbyopia: presbyopia correction is a compromise that allows the patient to do without corrective lenses most of the time. Numerous laser options are available. Presbyopia treatment is tailored to each patient's needs and lifestyle. The pre-operative examination and discussion with the patient should assess whether the indication meets the patient's expectations, given that it is a compromise. In the event of incipient cataract, cataract surgery should be considered, as it enables presbyopia to be corrected at the same time, in the absence of any contraindications.

IS REFRACTIVE SURGERY SAFE?

  • Contrary to popular belief, the proportion of ophthalmologists performing refractive surgery is higher than in the general population. This shows that professionals have confidence in this type of surgery. (1). The American Society for Cataract and Refractive Surgery in a report published in 2017 showed a patient satisfaction rate of 98%. (4)
  • Pre-operative analysis is essential for eliminating at-risk patients. This technical analysis, combined with the surgeon's experience, will enable us to eliminate high-risk patients and choose the safest laser technique for the patient.
  • It should be stressed that wearing contact lenses is not without danger, since the risk of corneal abscesses, even if rare when the proper precautions are taken, can have a definitive impact on visual acuity by causing permanent corneal scarring.
  • The germs found were Staphylococcus aureus, Pseudomonas Aeruginosa and Acanthamœba (3).
  • Contact lenses should not be worn in swimming pools or showers (amoebiasis).

POSSIBLE SIDE EFFECTS

Ocular dryness, often transient, may occur. This condition requires instillation of moisturizing eye drops. Nocturnal halos around lights may be perceived. These symptoms, often already present in myopic or astigmatic patients, tend to diminish over time.
Corneal laser refractive surgery successfully corrects visual defects and eliminates the need for glasses.
A rigorous pre-operative examination, carried out by ophthalmologists experienced in refractive surgery, enables us to eliminate patients who present particular temporary or permanent risks.
With a track record of over 30 years, this surgery has corrected the refractive errors of over 50 million people worldwide.
Laser refractive surgery enhances the eyes and provides a psychological sense of liberation.
It often has a "booster" effect on personal and professional relationships!

Bibliography

  1. Borderie V. Safety of refractive surgery: a key to its future development. Cahiers d'Ophtalmologie 2020 ;242, 27-29.
  2. Rozenbaum J-P, Saragoussi J-J. Société Française d'Ophtalmologie 2020 report: microkeratomas.
  3. Benhmidoune L. and all: Corneal abscesses on contact lens wear: clinical, microbiological and therapeutic aspects. JFO 2013 ; 36,7 :594-599.
  4. Wen D. et al. Postoperative efficacy, predictability, safety and visual quality of laser corneal refractive surgery: a meta-analysis. Am J Ophthalmol 2017; 178: 65-78.
  5. Rozenbaum J-P. Treatment of regular astigmatism by lasik: Réalités Ophtalmologiques Dec. 2015.
  6. Rozenbaum J-P., Nordmann J-P. Contribution and evaluation of aberrometric treatment with the Meditec MEL 70 laser. JFO 2002; 25, 5: 39-42.
  7. Cochener-Lamard B.: Technological advances in refractive lenticular corneal surgery. AOS. SAFIR 2023.
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