Diagnostics at the EuroEyes ALZ Eye Laser Center

Autorefractometer:
a computerized vision testing machine used obtain and objective measure the eye’s refractive error. This measurement provides the most accurate prescription for corrective lenses. An autorefractometer is absolutely necessary to determine refractive error in children who are unable to be subjectively refracted by choosing the "better" of a series of corrective lens pairs.

Phoropter:
a device use to measure the subjective refraction is an intensive incremental process by which the most accurate refractive error is determined according subjective visual discrimination data from the patient. This measurement is not as precise as an objective measure (see above), but sufficient for determining the extent to which the error can be corrected with laser surgery.

Slit Lamp:The slit lamp is a microscope with a light attached that allows the doctor to examine your eye under high magnification. This instrument is primarily used to view the anterior structures of the eye such as the cornea, iris, and lens. However, with special lenses, it is possible to examine the vitreous and the back of the eye as well. The instrument’s name is derived from its adjustable light beam. By changing the width of the beam, the doctor can gather important detail about each eye structure.

Automated and Goldmann Perimetry:
Perimetry is the systematic measurement of visual field function. The two most commonly used types of perimetry are Goldmann kinetic perimetry and threshold static automated perimetry. With Goldmann or "kinetic" perimetry, a trained perimetrist moves the stimulus; stimulus brightness is held constant. The limits of the visual field are mapped to lights of different sizes and brightness. With threshold static automated perimetry, a computer program is selected. The most commonly used one tests the central 30° of the visual field using a six degree spaced grid. This is accomplished by keeping the size and location of a target constant and varying the brightness until the dimmest target the patient can see at each of the test locations is found. These maps of visual sensitivity, made by either of these methods, are very important in diagnosing diseases of the visual system. Different patterns of visual loss are found with diseases of the eye, optic nerve central nervous system.

CSO Topography:
The measurement of the dimensions and curvature of the corneal surface. Computerized analysis of corneal topography reveals any distortions of the cornea, such as is keratoconus or corneal scarring, as well as the corneal curvature and meridians of astigmatism. This diagnostic procedure is essential for patients being considered for refractive surgical procedures (such as LASIK) and may even be necessary in the follow-up of some patients who have undergone refractive surgical procedures.

Orbscan Pachymetry:
Corneal pachymetry is the measurement of corneal thickness. Both ultrasonic and optical pachymetry are methods of measuring corneal thickness. Ultrasonic pachymetry is more reproducible, but optical pachymetry is especially helpful in measuring the depth of corneal pathology. Pachymetry is not a new technology; it has been used in routine ophthalmological exams when corneal pathology has been suspected. It is a valid test for many ophthalmological conditions, such as corneal edema, Fuch’s endothelial dystrophy and bullous keratopathy.

Aberrometer Zywave:
The Aberrometer is an instrument which measures the total refractive error of the optical system of the eye. A wave of parallel rays of light is sent into the eye and focused on the retina. Upon exiting the eye, the reflected light ray is sent through an array of lenses and recorded with a very small camera. An eye with ideal vision will reflect the rays of light in a straight wave front. Each deviation of the straight wave represents one diopter, or unit of refraction. After measuring the total refractive error it can then be accurately corrected with laser surgery. Instead of just measuring the lower order aberrations (nearsightedness, farsightedness and astigmatism), the Bausch and Lomb Zywave (shown here) can detect up to 64 different higher order aberrations could be detected and measured.

Ultrasound Pachymetry:
The ultrasound pachymeter (shown here) is designed for measuring the axial length of the eye and the thickness of the cornea. Ultrasound energy is emitted from the probe tip acting as both the transmitter and receiver of ultrasound energy. Some of the energy is reflected back toward the probe in the form of an echo. Measurement data can be calculated based on both the time it takes the echo to travel back to the probe from the eye and the preset converted velocity.

OCP: Non-contact Pachymetry:
Optical Coherence Tomography, or OCT, is a noncontact, noninvasive imaging technique used to obtain high resolution cross-sectional images of the retina. OCT is analogous to ultrasound B-scan imaging except that light rather than sound waves are used in order to obtain a much higher longitudinal resolution of approximately 10µm in the retina. OCT has been shown to be clinically useful for imaging selected macular diseases including macular holes, macular edema, age-related macular degeneration, central serous chorioretinopathy, epiretinal membranes, schisis cavities associated with optic disc pits, and retinal inflammatory diseases. In addition, OCT has the capability of measuring the retinal nerve fiber layer thickness in glaucoma and other diseases of the optic nerve.

Biometry IOL-Master:
The Zeiss Humphrey IOL Master is the first non-contact optical coherence biometer and it allows fast, accurate measurements of eye length and surface curvature, necessary for cataract surgery. A biometer is used to determine the power of the refractive power of IOL to be implanted before surgery. At the ALZ clinic, we use the IOL Master biometer- recognized and acknowledged as the most advanced and accurate machine of its kind in the world – to make this determination. Using this machine, we have seen a level of accuracy in IOL calculations never previously possible in the local setting.

Meso-Test:
This test measures the patient’s night driving fitness by determining night vision with and without glare. LASIK surgery is not recommended for patients who are determined to already have very poor night vision as some LASIK patients report seeing increased glare, halos, and starbursts around lights after surgery.

FDT: Frequency Doubling Technology:
By introducing peripheral optical attractions, or flickering, this technology allows the ophthalmologist to examine and measure the perception and operability of peripheral vision within individual ranges of the retina. FDT allows visual field testing to proceed from the macula to an eccentricity of thirty degrees. Its ability to detect magnocellular pathway deficiencies has made FDT an excellent tool in the management of glaucoma.

Scheimpflug Camera:
Scheimpflug Imaging in Ophthalmology is a technique that allows the assessment of the anterior segment of the eye, from the front of the cornea to the back of the lens, in a sagittal plane. The name dates back to the Austrian national Theodor Scheimpflug, who invented and patented the technique in 1904, in Vienna. The new photographic apparatus he designed found its first applications in the pursuit of military goals. Built into balloons it was used to photograph landscapes for the creation of accurate maps for improved targeting. It was only in the 1970's, when a group of cataract researchers, led by Prof. Otto Hockwin, Bonn, Germany, in collaboration with optical companies developed a Scheimpflug slit imaging device for ophthalmological purposes. The initial prototypes used film as a matrix. Presently Scheimpflug imaging devices are upgraded to digital imaging devices. A Scheimpflug imaging device is not necessary for a clinical diagnosis of cataracts or to indicate the necessity of a cataract operation. But besides documentation of anterior segment findings, it can be very helpful to investigate the time course of cataract development or to detect early changes in clinical studies when cataract is suspected as a possible side effect.

Pentacam Scheimpflug Camera:
The Pentacam images the anterior segment of the eye by a rotating Scheimpflug camera measurement (see above). This rotating process supplies pictures in three dimensions. The center of the cornea is measured very precisely because of this rotational imaging process. The measurement process lasts less than two seconds and minute eye movements are captured and corrected simultaneously. By measuring 25,000 true elevation points, precise representation, repeatability and analysis are guaranteed. Patients with abnormal corneal topography or thickness that may have previously been rejected based on topography alone may be approved for LASIK because of the Pentacam.