OPERATION OF MYOPIA
What is myopia?
- How long has been used the operation of myopia?
What are the motives of the candidates to the operation of myopia?
- Which are the contra-indications?
- Which are the examinations to be practised?
- The intervention by LASIK is the most practised technique and most recent. Of what does consist it?
- Which are the advantages of the LASIK compared to the Excimer laser of surface (PRK), still very practised intervention?
- What is laser excimer of surface (Photo Refractive Keratectomy or PRK)?
This technique of laser was the first used since 1993. It consists in reorganizing the cornea by directly applying the laser to the surface of the eye after withdrawing its surface layer (epithelium). The operation is practised under local anaesthesia, it is painless. Its duration is short (a few minutes). The surgeon starts by withdrawing the epithelium by scraping or after application of alcohol. It has access to a deeper layer then, the stroma which accounts for 90% thickness of the cornea, to which the laser excimer will be applied with a high degree of accuracy. Each impact withdraws a thickness of cornea of 0,2 microns (thousands of millimetres) on a surface from 1 to 2 millimeters. The number of impacts is calculated by computer and varies according to the importance of the anomaly to correct. To correct myopia, the center of the cornea will be dug on a surface from 5 to 7 millimeters (optical zone) and a 120 microns depth to the maximum. The cornea becoming less convex let the luminous rays reach the retina. Myopia is thus corrected.
The PRK is effective to correct low or average myopias up to 6 diopters and the astigmatisms up to 3 diopters.
Disadvantages of the laser excimer of surface are the pains which can exist during 48 hours time that the epithelium pushes back completely and in the possibility of one cicatricial veil likely to delay visual recovery. This veil is generally tiny but in rare cases, it can be dense enough to obstruct the vision during several months. In the event of insufficient correction, a new intervention is possible after stabilization of the result of the first intervention (one year). The other side effects and risks are the same ones as for Lasik.
After the intervention with the excimer laser, the wearing of glasses filtering the ultraviolet rays is necessary during several weeks in the case of solar exposure.
A particular technique of PRK is called LASEK. After rising of a surface flap of the cornea made up of the epithelium, then impacts of laser are applied to the surface of the cornea. The epithelium is replaced at the end of the intervention. A lens-bandage is then applied. The studies show that the LASEK is comparable with the PRK in the field of the pain, visual recovery, and the results. It requires a particular instrumentation and it is more delicate to realize. The LASEK thus does not seem to bring a notable benefit compared to the PRK.
PRK and LASEK can advantageously be replaced by the new technique of Lasik with femtosecond laser.
A new method of Lasik using only the laser ("All laser Lasik") is practised only in some American and European centers. It uses Intralase FS (Femtosecond laser).
In the traditional technique of Lasik, the laser excimer will reorganize the cornea in its depth to correct the visual defect. However, before the action of this laser, one uses a small plane with a metal blade to cut out a flap which is inclined to have access to the depth of the cornea which will be treated. The cutting of this flap is the most delicate time of the intervention. Even in expert hands, the thickness and the diameter of this flap cannot be constant with one intervention to the other and complications of cutting flap are likely to occur being able to involve a delay of visual recovery and sometimes a certain degree of loss of permanent vision.
The "All laser Lasik" procedure replaces the microkeratome by one femtosecond laser. This laser replaces the blade completely. The femtosecond laser emits light waves ultra short of which the duration is 10 power -15 second i.e. thousand million times shorter than the flash of an electronic camera. (the femtosecond, is compared with one second, equivalent the 10 minutes compared with the duration passed since the creation of the universe). It creates gas microbubbles resulting from the vaporization of corneal tissue right under surface, of 3 microns (3 thousandth of millimeter). These thousands of juxtaposed bubbles allow the creation of a corneal flap of very sharp thickness, cut out perfectly with the programmed depth. This laser involves much less tissue side effects.
- What brings "All laser Lasik" ?
Traditional Lasik with microkeratome remains an excellent technique with good results and rare complications.
"All laser Lasik" with femtosecond laser uses, as for it, two successive lasers (femtosecond laser and excimer laser) with an increased cost, price of progress and safety. It brings a certain number of advantages which make a major technological progress:
- a safety increased for those which consider a refractive surgery by Lasik but are rejected by the use of the plane. The level of vacuum used during the phase of aspiration being lower, the intervention is more comfortable. Certain possible complications are also eliminated (complications of cutting) or decreased (displacement of the flap, symptoms of ocular dryness). The eyes with particular anatomical conformation, small, are easier to treat.
- an increased sharpness: the thickness of the flap and its size are much more accurate. The possibility of creating a fine flap of quality makes it possible to cover the subjects which have one too thin cornea to be able to benefit from traditional Lasik. Indeed, the flap raised with the femtoseconde laser can be much thinner (80 microns instead of 160 microns), then making it possible to treat a greater thickness of cornea with the excimer laser thus a stronger myopia.
- an increased quality of result: with the femtosecond laser, a more significant group of patients reaches the maximum vision thanks to less induction of astigmatism and aberrations. The possibility of carrying out greater optical zones of treatment makes it possible to decrease side effects . Lastly, the number of reinterventions for insufficient correction is decreased.
- This technique is particularly interesting for hypermetropes presbyopes, strong short-sighted and strong astigmatisms.
- What are the councils for the intervention?
- It is about a simple surgical act, not requiring hospitalization nor general anaesthesia. You will come to a private clinic a few moments before the intervention. The surgeon will take care of all to explain you.
- You will see a small red light above you which will be used like a benchmark and the surgeon will ask you to stare it to align the laser beam. You will have to stare during the whole intervention this red light. To keep staring this is very simple. If you see a a little vague image or which moves, it is normal, stay in the medium of the red spot even if it is diffuse and very blur. If you see a green spot do not bother because it is intended by the surgeon.
- It is very important to concentrate on the fact of maintaining the head in its initial position without moving the chin.
- a field of protection will be placed on your face. Keep the two eyes open under the field.
- Your eye will be held opened by a spacer; this will prevent you from blinking.
- If you move, if your staring is not satisfactory, do not fear anything: the device of eye-tracker stops the laser automatically the time that you take again staring. But the regularity of the corneal treatment is better when the eye is motionless (the majority of the patients make it very well).
- What is the Lasik procedure :
- First of all the surgeon put a succion ring which will maintain your eye. You will feel a pressure on the eye but no pain. The sight disappears or decreases during 30 seconds. That is completely normal.
- Is the operation painful?
- No. The anaesthesia is local by instillation of 3 eye drops before the intervention which will get a total insensitivity. The intervention proceeds under operational microscope, you will not feel any pain and will not see the instruments. The intervention is not painful. You should not be contracted and have an excessive anxiety. You should not move abruptly during the operation. Do not cross the legs, keep the arms along the body. Do not speak during the operation.
- How long does the intervention last?
20 minutes per eye, approximately. The duration of the laser lasts a few ten seconds. If the surgical act is short for the patient, the preparations, on the other hand, take much more time because of their extreme meticulousness and of the many tests of safety to be carried out. The stay in the private clinic (examinations and intervention) lasts 1 hour, 2 hours if the 2 eyes are operated. In this case you will join the waiting room then the operated eye will be examined before operating the second.
- How do the postoperative continuations occur?
- the patient is often surprised of astonishing facility with which the intervention occurred. At the end of the intervention, he can go back to his residence, preferably accompanied because of the premedication. The residence time at the private clinic is usually of one hour.
The operational continuations are simple, often limiting themselves at most to a whimpering and a feeling of foreign body, of sand in the eye during a few hours. The following day there is almost no symptom anymore and the usual activity can be taken again.
Precautions must be taken to avoid any risk of infection: to stop the wearing of the lenses a few days before the intervention; the washing of the hair must be careful, the swimming pool is contra-indicated during 2 to 3 weeks.
- Which are the usual symptoms after the intervention by Lasik?
- the following day there is usually no symptom anymore. However it can exist, sometimes, one of the following phenomena: discomfort, ocular embarrassment, light pain, burns, feeling of foreign body during two days. Redness, sensitivity to the light, whimpering, during one week. Ocular dryness, dazzling, difficulties of leading the night for one month.
- the most common feeling is the dryness of the eye, to avoid by the instillation of artificial tears during several weeks especially the evening when sleeping.
- Warn your ophthalmologist of the event of disorders, in particular if the initial symptoms reappeared after one period of lull.
- How will the vision evolve ?
On the following day, the vision is very clearly improved. A blur can persist in vision from far with feeling of unfolding of the images. The vision takes a few days before being stabilized. Difficulties with the reading, night eye trouble are possible during first postoperative days. The reading is sometimes difficult by the eye operated especially at the subjects close to forty. Then quickly, in a few days, the vision improves to become good from far like from near, all the more quickly as the starting myopia was low and the patient younger.
- Which visual result one can expect ?
The sharpness of the final result is as much better as the anomaly to be corrected is weak. The best results are obtained in low and average myopias from 1 to 6 diopters in front of, in theory, being corrected completely or quite completely. Often, the patient even feels a visual benefit compared to the vision he had before with his correction. Very appreciable fact, for the large short-sighted ones, the intervention present a visual advantage compared to the glasses: there is indeed one significant improvement of the visual field restoring an image of the objects closer to reality.
It is however difficult to ensure that the correction of myopia will be total as of the first intervention. Indeed, especially for strong myopias higher than 6 diopters or in the event of astigmatism, a small myopia or an astigmatism can persist. The vision will be very clearly improved, but one cannot certify that the patient from the start will be corrected with 200/200. The patient obtains a sufficient improvement then to recover an autonomy in the current daily acts without the assistance of glasses.
The result of the operation is definitive, stability settles between 1 to 3 months, with, during this time, a period of weak fluctuations dependent on the importance of myopia, the type of laser, the parameters used, the age and of the characteristics of cicatrization specific to corneal tissue.
The final result can be evaluated after 1 to 3 months, a possible complementary intervention to approach the optimal result will be planned at this time. The reintervention is then easy, without having to carry out a new cutting, by raising the corneal flap and by applying a few seconds of laser again.
The long-term result is stable without change of the vision.
- Which will be the visual result in the case of the myope presbyope (after 45 years)?
One can obtain a customized result to waiting of each one. For this reason it is desirable, in the myope of more than 45 years, not to operate both of eyes the same day and to await one week at least the result of the first eye. The intervention of the second eye will come to improve either the vision from far or the reading according to desires of the patient.
If myopia is corrected perfectly on both of eyes the wearing of glasses for the reading is felt usually around 45 years as at the majority of the nonshort-sighted individuals. Also it is often preferable to correct an eye completely and to leave a little myopia on the second at the people close to forty what makes it possible to delay or avoid presbyopia, while preserving a good vision from far. This technique, called monovision, is very well tolerated by the majority of the patients when it is moderate, ensuring a good visual comfort in many situations. In all the cases, the operated sees much better without glasses in the everyday life. Auxiliary glasses can be useful from far for particular circumstances requiring a maximum vision like fast automobile control, the reading of posters at a certain distance or for the prolonged reading, the reading of the small letters or in reduced luminosity. The success of this monovision can be anticipated into preoperative by the wearing of lenses. It is not desirable to exceed 1,50 diopter of difference between the two eyes to maintain a stereoscopic vision. It is necessary to take account of the occupation of the subject. The lasik is the surgical technique of choice because it allows a fast recovery in the event of nonsatisfactory result.
It should be noted that to preserve a small astigmatism if there exists into preoperative allows to compensate for presbyopia.
- What can one make in the event of insufficient visual result (under or over-correction)?
During the preoperative examination, it is possible to have a good idea of the probable result without guaranteeing the result because there are reactions and differences in cicatrization which know individual variations. In certain cases, the final result will be evaluated after 1 month, a possible complementary intervention will be planned at this time after stabilization of the vision. The reintervention to refine the vision is then easy by raising the corneal flap, without having to carry out a new cutting, and by applying a few seconds of laser again.
If this reintervention is not allowed by the thickness of the cornea, a small pair of glasses or lenses can help in circumstances requiring a very good vision from far like fast automobile driving, the reading of subtitles or posters at a certain distance. One can note that the driving licence B in France, for example, requires a vision without glasses minimum of 120/200 on an eye and 40/200 of the other.
It is always possible, if needed, to wear contact lenses after Lasik under the same conditions as before the intervention.
- Can one correct the astigmatism?
Astigmatism is an abnormality of curve of the cornea which presents an oval form instead of being round. It involves a vague vision from all the distances, from near like from far. The astigmate does not perceive contrasts clearly. The astigmatism involves a lengthening of the vertical, horizontal or oblique lines and the confusion of close letters like the H M and N or the 8 and the 0. It can cause an ocular tiredness or headaches.
The astigmatism up to 6 diopters can be corrected in a satisfactory way with the lasers of last generation. If the astigmatism is significant, one cannot guarantee the complete correction in only one intervention. The LASIK is the technique of choice because of the facility of recovery in the event of insufficient correction, the possibility of correcting significant or complex astigmatisms.
- Which adverse reactions can one meet after the intervention with the LASIK?
On an aesthetic level, the intervention does not leave any visible trace.
The subjects choosing the operation often have an intolerance with the lenses of contact because of a corneal dryness. The moderate ocular dryness is not a contra-indication with the intervention but one will have to expect to have an increase in the symptoms during a few months. After the intervention, it is very frequent to test symptoms of ocular dryness: feeling of dry eyes, sand, sensitivity started by the wind, dust, the cold, more rarely vague visual. This feeling is temporary. It can be treated by the instillation of artificial tears or ointment sometimes during several weeks.
Even if the vision is 200/200 it can exist a modification of the quality of the vision related on the oedema and the cicatricial rehandling of the interface. It is of very variable repercussion according to cases, the more marked that myopia to be corrected was stronger and the smaller zone of treatment. It can be a question of an impression of veil, of a reduction in the sensitivity of contrasts, of a night dazzling, a perception of halos around the lights the night (for instance, caused by the headlights of cars during night driving), of a reduction in the capacity of adaptation to the brutal changes of lighting (entered and left tunnel for example). These disturbances are seldom and usually disappear in a few weeks or months.
- How to optimize the result ?
- The quality of the result and safety can vary according to the material used. A specialized center only devoted to the interventions by Lasik, makes it possible to benefit from the most recent technological advances of a material regularly maintained, tested, and updated as well as involved looking after staff, pledge of safety and reliability.
- corneal topography Orbscan is obligatory to detect the contra-indications.
- All the lasers do not give the same quality of vision. The laser using sweeping by spots brings reliability, precision, safety. It must include a system of eye-tracker making it possible to limit the risk of bad centering.
- It is the same for the microkeratome which must be the most recent model. A new blade should be useful only for the intervention of one eye.
- Better, the femtosecond laser is the most modern technique replacing the cutting of the flap to the microkeratome. It is used in some American and European centers, bringing an additional safety and a better quality of results.
- Simplicity of the intervention for the patient and speed of visual recovery do not mean surgical simplicity. The technical control of the surgeon and his experiment are essential for the quality of the result. There is an undeniable surgical training which makes it possible to obtain better results as it is tested more. Its operational protocol of corneal replanning is determined by a program which is strictly personal but established according to its former results.
- The surgeon must be ready to practise all the existing interventions. A surgeon that only practise one technique will tend to propose only that one. Whereas a specialised surgeon in refractive surgery chooses the intervention which is the most safe, which will be more appropriate for each case, and to treat the incidents and complications which could occur.
- Which risks can one meet with the LASIK?
Risk zero does not exist in surgery even if the complications of Lasik are extremely rare.
The surgeon depends on mechanics; he must have a perfect command of the devices used and check it before each intervention. He must stop the intervention if there is a technical problem, the patient must be informed of this possibility (insufficient ocular tension, blocking of the microkeratome, irregular or incomplete cutting of the flap...) the intervention can be generally deferred of a few months after satisfactory cicatrization of the cornea.
The lasik requires an equipment very sophisticated and of excellent quality. The microkeratome which realizes corneal cutting was conceived more than twenty years ago and benefited with the wire from the time of many improvements which currently lead to reliable and reproducible models. The insufficient quality of the first microkeratomes could involve trouble of irregular cutting and deteriorations of form and transparency of the cornea with consequences on the quality of the vision (astigmatism sometimes responsible for a reduction of the vision, fortunately generally moderate, of difficult treatment). This possibility became very rare with the last microkeratomes, of a great reliability, thus offering a great safety.
The cutting of the flap to the microkeratome is now replaced in some American and European centers by a femtosecond laser which makes it possible to remove quite all the problems of cutting.
The off-centring of the treatment involves side effects being able to require a surgical recovery: one can have a duplicated vision, a deformation of the images. This risk is reduced considerably by the best lasers having one " eye tracker" which allows, thanks to an infra-red camera, automatic continuing of the glance by the laser beam even in the event of unvoluntary movements of the eye. If the patient moves, the laser stops automatically and this system keeps in memory the exact position of the treatment. The surgeon centres the eye and continues the intervention where it was stopped.
One should not rub the eye nor practise violent sports during the operational continuations not to mobilize the flap. A reintervention can, exceptionally, being necessary in the event of displacement of the flap to position it back. This incident is not serious if it is treated quickly, and can occur during the first hours after the intervention.
A postoperative inflammation can generate a fuzzy vision. It disappears in the very majority from the cases with local an anti-inflammatory drug treatment.
The infection of the cornea is a very exceptional but serious complication with formation of an abscess and a corneal opacity being able to obstruct the vision. The instillation of antibiotic eye drops, hygienic rules, and the post-operative monitoring making it possible to detect an infection beginner and to start the suitable treatments are the best guarantees against a serious corneal infection. An abnormal redness, a visual fall must make consult urgently. The frequency of an infection is rarer after intervention than at the time of the wearing of lenses of contact.
The cicatrization of the surface cornea (epithelium) can be abnormal. It can suffer from the cutting of the flap, source of erosion. The cells can heal too slowly or in an irregular way.
An infiltrate of cells of the epithelium under the flap can require a reintervention for washing these cells.
The regular or irregular astigmatism due to a irregularity of the surface of the cornea, can result in a visual blur, a double vision. Generally corrected by glasses or lenses of contact. Seldom, it can be responsible for a reduction of best corrected acuity. The cicatrization of the cornea, sometimes long, can reduce this astigmatism. A reprocessing is possible.
The appearance of an ectasia (convexity of a too fine cornea) is seen when the digging of the cornea was too significant or when the cornea was pathological (kératocône).
- Can other interventions correct myopia?
Radial keratotomy consist in practising four incisions on the surface of the cornea, levelling this one, according to a provision in ray of wheel, saving a central optical zone. One can also correct the astigmatism by arciforms or tranverses incisions. Thanks to some drops of anaesthetic eye lotion, the intervention is completely painless and fast. The operational continuations are light. On the following day the vision is very clearly improved. It is the oldest intervention of the myopia whose retreat is more than 20 years old. It made it possible to treat a great number of people with remarkable results but this practice has considerably been reduced to the benefit of the PRK and the LASIK. The radial keratotomy can be currently reserved for low myopias lower than 3 diopters for which the process of 'mini radial keratotomy' is safe.
The installation of rings is a relatively complex technique of limited indication: low myopias until with 3 dioptres without astigmatism. It consists in introducing two plastic rings into the thickness of the peripheral cornea. Its interest is to be reversible and adjustable by a change of the diameter of the ring. The reversibility of the result being rarely the motivation of the myope wishing to be operated, this technique can find an indication with the approach of presbyopia as individuals are slightly handicapped by their small myopia and until there hostile with interventions with the final result. Side effects are possible: halos, dazzling, deformation or fluctuation of the vision. The ring is slightly visible in the eye.
- Can the large short-sighted ones benefit from other techniques?
- The CUSTOMIZED LASIK
The aberrometry is an examination measuring the aberrations, visual imperfections of the eye, which is an imperfect optical system. One distinguishes the aberrations from second order or low degree (myopia, astigmatism, hypermétropia) and the preoperative or postoperative aberrations of high degree. These post-operative aberrations are especially significant at the short-sighted operated involving side effects in low brightness in particular the halos and the dazzling. The goal of the cutomized lasik is to reduce these aberrations for a better quality of vision. It addresses to approximately 5% patients who have aberrations unusually high before the intervention.
- The INSTALLATION OF AN INTRAOCULAR LENS makes it possible to correct the highest myopias and hypermetropias.
95% of myopias, up to 10-12 diopters can benefit from the LASIK or the PRK. Beyond this limit, these techniques are not compatible anymore with a good visual quality. There is however a real handicap especially if the contact lenses cannot be carried. With an intraocular implant, the visual result will be of an excellent quality. It is about a heavier surgery, on general anaesthesia sometimes under local anaesthesia.
One carries out a small incision of the eye to insert the implant. The intervention is painless. Visual recovery is fast, in a few days. The sharpness of the correction is usually excellent. On the other hand, there is no correction of the astigmatism.
Several types of implants can be used. Each implant has its advantages and its disadvantages:
- If the implant is in front of the iris (anterior chamber lens) or clipped with the iris (Artisan), it will be necessary to supervise the cornea during years by a cellular counting. Indeed, in the case of a contact between the edges of the implant and the cornea, exceptional with the new models, can occur a rarefaction of the cells of the posterior face of the cornea. The implant must then be withdrawn. The implants do not correct the astigmatism or partially for some.
Mise à jour: 2015