Ординатура / Офтальмология / Английские материалы / Jaypee Gold Standard mini Atlas Series Lasik_Aragawal, Jacob_2009

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abnormalities on the front and back surfaces, such as found in keratoconus.

Figure 1.11C shows refractive display for the patient in Figure 1.11A. It is commonly used when evaluating patients for elective vision correction. Figure 1.11D shows topometric display for the patient in Figure 1.11A. It is most commonly used when fitting contact lenses. Figure 1.11E shows that when considering a patient for refractive surgical correction, look at the relationship between the four maps on the refractive display. This illustrates a suspicious “two point touch” where the posterior elevation corresponds to a mild anterior elevation. This patient had low pachymetry, but the pachymetry map was otherwise normal, symmetrical around the center. Figure 1.11F shows an example of a “three point touch” where the elevation on the posterior and anterior surface corresponds to a steep area on the curvature map. Figure 1.11G is an example of a classic ectasia following excimer ablation for high myopia, where all four maps show characteristic signs of ectasia. Figure 1.11G shows that astigmatism manifests as a “saddle” pattern on the posterior surface. Figure 1.11I shows a pachymetry map of a patient with keratoconus. Note the displacement of the thinnest point, and the overall reduction of corneal thickness.

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trained to carry out the examinations. It is possible to chose the axis to be explored or carry out an automatic 360° exploration along the four meridians.There is an optical target that can be focused or defocused with positive or negative lenses. Natural accommodation can be stimulated and anterior segment modifications during accommodation can be explored in vivo

Until recently, measuring the depth of the anterior chamber and checking the endothelium cell count with a specular microscope were considered sufficient when performing phakic implants. With the development of techniques such as the OCT, surgical indications can be streamlined and a regular check-up of the anterior chamber following such an intervention is mandatory. Figure 1.12A, shows a posterior chamber ICL inserted in a patient over the age of 45 having developed cataract and severe optical problems. Although the ICL has been placed in the posterior chamber, on the endothelial safety scale we note that the edges of the optic are approximately 1mm from the endothelium. This distance is insufficient as it has been proved that a minimum safety distance of 1.5 mm is necessary between the edges of the lens’ optic and the endothelium.

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Figure 1.13: Concept of eye tracking for more accurate corneal ablations during movements of the eye new eye tracking technology can trace eye movements by detecting displacement of the pupil. In microseconds the eye tracking computer can move the treatment spot of an excimer laser beam appropriately to compensate for these eye movements. For example, laser beam (LA) is treating an area of the cornea when the eye is in position (A). Suddenly, during treatment, the eye moves slightly to the left to position (B). The eye tracking computer detects the movement of the pupil to the left (dotted circle) and commands the laser to track left (LB) the same amount, within microseconds. Thus the laser continues treating the same area of the cornea as desired before the eye movement took place. Such technology

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3.Monocular infrared pupillometers associated with corneal topographers. They provide more reliable and consistent measurements than portable pupillometers, and some of them measure some pupillary dynamic changes with different light conditions.

4.Binocular infrared pupillometers. Today these instruments are the most reliable ones to assess pupil size under different, set light conditions. They compensate for theoretical changes in pupil size due to accommodation thanks to a simultaneous measurement for both eyes. Some of them truly provide a dynamic measurement of changes in pupil size related to illumination.

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interview is essential in screening potentially “dangerous” patients (e.g. Is the medical history significant for AIDS, diabetes or arterial hypertension?) and to improve future patient’s compliance by means of building a good patientdoctor relationship.

To be a good candidate for vision correction surgery, patient must meet the physical, health and age criteria for the particular surgery (Laser In Situ Keratomileusis LASIK, Laser Epithelial Keratomileusis LASEK, Photorefractive Keratomileusis PRK, clear lens exchange, epikeratoplasty-epikeratophakia, laser thermal keratoplasty LTK, astigmatic keratotomies, implantable contact lenses-phakic intraocular lenses, conductive keratoplasty CK to treat presbyopia, …).

The refractive candidate must fully understand the procedure and be aware of the risks and possible side effects. Limitations for refractive surgery can be ophthalmologic and general. Medical history is important in estimating patient’s suitability for surgery: All refractive procedures have ocular, physical, health and age criteria.