Techniques to go without glasses or contact lenses.
Next we will detail and explain the most common options, which depend on some variable factors in each person:
1. Defect graduation, its value and time stability
2. Age.
3. Corneal Thickness
4. Diopter Power of the Cornea.
5. Depth of the anterior chamber.
6. Number of corneal endothelial cells.
7. Tear Absence.
8. Existence of cataract or other eye disease or eyelids.
 
Common Defects,
Hyperopia does not increase. It is normal in childhood and usually decreases till the age of  12.
Myopia does not decrease. It increases when the eye grows, and the most common is to do it half diopter per year. A person is stable when during two years or more has not raised the diopter graduation. In high myopia (more than six diopters) the possibility of eye growth beyond two years is higher than in low myopia, and can do so after age of 10-15 years and up to 45 years. Myopia does not increase during pregnancy unless the two conditions coincide, it is rare nowdays because women have children at ages when myopia hardly worsens.
 
Congenital Astigmatism (existing at birth) corresponds to 95% of astigmatism cases and hardly changes during life. When astigmatism changes in a child or adolescent a corneal disease must be seek.
 
Before surgery we measure the value of the refractive error (default graduation) after the patient has been without wearing contact lenses for about five days and put drops of cycloplegic (eye drops that paralyzes the ciliary body of the eye and therefore accommodation ). This makes that the patient looks bad for 12-24 hours after the visit because he/she can not focus properly. The thickness and power of the cornea of a normal person remain stable throughout life.
 
The depth of the anterior chamber gradually decreases with age. The number of endothelial cells of the cornea decreases naturally with age.It also decreases if there is trauma or surgery of the eye. These cells are responsible for maintaining the corneal tissue dehydrated to be transparent. They must be in good condition and have a minimum number in order to implant an intraocular lens although today we can transplant.
 
We measure the amount of tear that occurs and the tear film before LASIK or PRK.
Refractive surgery by definition is done in an eye having myopia or hyperopia or astigmatism or presbyopia but not in any other disease. If you have any defects such as high-pressure, lens opacity or a deformed cornea or too thin one, surgery may be contraindicated.
The visit, to decide whether a person can be intervened with refractive surgery and which technique we may choose, can last one or two hours or even more than one visit may be needed. A well-operated eye rarely causes problems, but because of its high sensitivity and optical precision surgery must be perfect. Pre-operative visit is as important as the surgery itself. We must explain what goal we want to achieve and not promise results that are not real. Patient expectations must be achieved.
To correct the graduation defects we can modify the natural lens of the eye, the cornea (with LASIK or PRK), or add another in the anterior, posterior chamber of the eye (surgery with phakic lenses) or replacing the crystalline lens (Clear Lens Surgery).
 

Laser Surgery LASIK and PRK

We've been doing Lasik Surgery for 20 years. It is the most common surgery worldwide. The term LASIK is an acronym that comes from Laser Assisted in Situ Keratomileusis, and means modification the curve of the anterior surface of the cornea with a laser. Its main objective is to change the diopter of the cornea and focus the image properly on the retina.
Considerations:

• It is not a reversible process, the removed tissue can not be replaced.
• Normally we operate both eyes in the same session since 2008.
• When the laser energy volatilize the molecular bonds of the corneal tissue during surgery you can smell burning, what is normal.
• If the eye, after surgery, grows, we may need an optical correction for myopia starting again from scratch.  
• We can treat successfully up to 8 diopters of myopia, 6 of astigmatism and 3 of hyperopia  with the machine we have today. Higher values have more undesirable effects of poor night vision and halos around lights.
• The number of diopters to treat depends on the thickness and the radius of the cornea and the pupil size in the dark.
• Years ago we had to re-operate more than 15% of patients because graduation was not sufficiently accurate. Currently only two or three a year. The accuracy has dramatically improved and complications have decreased.
• During surgery we injure corneal nerves and that produces less tear because of lack of stimulation on the surface. The secondary dry eye usually lasts between one and three months but can be more persistent.
• We measure the amount of tear with Schirmer test after anesthetic instillation before surgery. We measure the quality of the tear film with the test BUT (Break Up Time, breaking time teardrop). We dye tear with fluorescein and determine how many seconds it takes to break the film.
• A variation of Lasik is PRK (Photorefractive Keratectomy, removal of corneal tissue with photons with refractive purpose). It is indicated in dystrophies of basal epithelial membrane, superficial opacities or people with high risk of corneal trauma (boxers). It is used the same laser but without the microkeratome. Visual results for two or three months are the same. The recovery is slower.
• After surgery, therapeutic conctact lenses may be prescribed, you wear them several days without remove them at night and they serve as a reservoir of medication and act as transparent protector.
• Complications from the microkeratome (a device that cuts the corneal lenticule 90 to 120 microns thick) have also diminished with new models. In some cases of extreme measures of some parameters, we suggest the convenience of using the femtosecond laser although it is a more expensive procedure.
• The profiles of the optical zone that the current laser forms, are aspherical and optically better, and therefore have less night vision aberrations and are clearer. The refraction stabilization is achieved after two months after surgery.
• Treatment with anti-inflammatory eyedrops, antibiotics and artificial tears without preservatives is essential to achieve a good result.
• To prevent displacement of the lenticule, you dont have to rubb the eyes for 6 weeks after surgery.
• It is essential to wash and perfectly remove makeup before surgery.
• No one in the laser room can carry perfume, colognes or cosmetics containing alcohol. It evaporates and the laser beam does not reach the cornea to collide with air particles: this means that not all scheduled diopters are corrected
• It is very important to keep the time of surgical steps to prevent evaporation of water from the cornea. This causes drying and thinning and makes the laser more effective than desired what ends in different results in diopters than expected.
• During the application of mechanical microkeratome or femtosecond we provoke a suction effect that raises the eye pressure for a few seconds. During this period the patient sees nothing but fully recovers his vision when suction is removed.

Arcuate Incisions:
 
Widely used until twelve years ago, when we were doing a pulse with calibrated diamond scalpels, now returns femtosecond laser for its simplicity and accuracy.  To its credit, with these incisions the visual axis and the optical wide area is not touched. They serve mostly for mixed astigmatism. Lasik devices also treat these astigmatism.
 


 

Surgery with phakic lenses (ICL, Artiflex ...)

Artisan or Artiflex, Ophtec of iridian support, which serve to all refractive defects less presbyopia.




ICL (Staar) placed in front of the lens and behind the iris, usually treats myopia and astigmatism. It is not visible when the pupil is normal.


 

Clear Lens Surgery

Lenses that are implemented within the capsular bag, once emptied the contents of the lens. We can correct all defects included presbyopia.  Usually they are implanted when exists a cataract, after age of 50, in people with graduation defects from far and near, or emmetropic (that do not require optical correction by far) by presbyopia. They are the most used ones and there are many models and types of different materials.