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Before laser correction, certain pre-operative eye examinations and measurements must be carried out. These examinations and measurements are made with modern and highly sophisticated ophthalmic equipment which give us important information about the parameters of the eye, especially the cornea that will be sculpted. The examinations and measurements are of utmost importance because the result is directly dependent on the consistency and precision with which we make these measurements.
An essential pre-requisite for these measurements and the laser to be carried out is for contact lenses to have been completely removed for at least 10 (ten) days.
Thus, it is necessary for the myopia or hyperopia, or astigmatism that will be corrected with laser to be measured with precision. Objective refractive measurements are obtained with auto kerato-refractometers and subjective measurements are acquired with visual acuity measurements.
The corneal topography is possibly the most important preoperative examination. At the Athens Eye Hospital various topographical machines are used to cross-check the information.
The ORBSCAN machine allows us to evaluate and measure both its anterior and posterior surface, to rule out diseases that have contraindications to surgery (e.g. keratoconus) as well as estimate its thickness. The pachymetry measurement is a very important as this indicates the limit to which we can sculpt with the laser.
Zywave technology for wavefront analysis. This technology allows us to study the eye as a whole optical system and to measure the total refractive-power taking into account even the various visual "flaws" of each eye called aberrations. The wavefront analysis enables us to input this data into the laser's computer and the laser individually sculpts the cornea, correcting any refractive flaws giving the best possible results with minimal tissue removal.
The newest topography, PENTACAM gives us similar information to the ORBSCAN, but with greater accuracy as it analyzing more areas on the cornea. The PENTACAM is used by our hospital for individualized correction, especially in high and irregular astigmatism, sculpting the cornea based on information from the topography (topo-guided).
Another important technology used at the Athens Eye Hospital is the Ocular Responce Analyser (ORA). This technology analyzes the elastic properties of the cornea and gives important information on corneal disease predisposition, such as keratoconus, which is contraindicated, and glaucoma.
The excimer laser used to sculpt the cornea creates a cool beam (cool and not thermal laser), which can break molecular bonds in a process known as "photo ablative decomposition" resulting in the sublimation of the cornea.
The most important feature of the excimer laser is its remarkable precision. Each pulse of the laser has the ability to remove 0.25 microns of tissue, e.g. 1 / 200 of a human hair.
At the Athens Eye Hospital we have the latest generation Allegretto 400Hz Wavelight flying spot excimer laser.