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HISTORY AND EVOLUTION OF AUTOREFRACTORS AND KERATOMETERS.
Who's your daddy?
Ernst Abbe: Invented the first refractometer , and many other devices. He was a German physicist and optometrist, and social reformer. Together with Otto Schott and Carl Zeiss, he laid the foundation of modern optics. Abbe developed numerous optical instruments.
Autorefractor Keratometer
There are four main types of refractometers: traditional handheld refractometers, digital handheld refractometers, laboratory or Abbe refractometers, and inline process refractometers.
An auto refractometer or automated refractor is a computer-controlled machine used during an eye examination to provide an objective measurement of a person's refractive error and prescription for glasses or contact lenses. This is achieved by measuring how light is changed as it enters a person's eye.
Common vision problems such as myopia (nearsightedness) or hyperopia (farsightedness) are the result of refractive error. Autorefractors are used to measure the degree of refractive error in the eye, and are suited well toward applications such as differentiating corneal from lenticular aberrations, and assessing pre and post refractive surgery patients. The patient focuses their vision on a fixation target such as a hot-air balloon floating over land. Like many ophthalmology instruments, they have spherical and cylindrical measurement ranges of -30 to +25D/±10D respectively. As the line between autorefractor and keratometer is often blurred, the customer should be aware of systems that have separate measurement ranges for autorefraction and keratometry.
KERATOMETRY
Keratometry is a technique used to measure of the anterior curvature of the cornea, which when damaged or misshapen causes a vision problem known as astigmatism. A keratometer works by reflecting an image off of two points in the cornea, and utilizes the relationship between object size, the size of the image reflected, and the distance between the object and the keratometer. The result is a minimum and maximum curvature value for the cornea. There are two types of keratometers: single position Helmholtz keratometers, which are more common and can adjust image size; and Javal-Schiotz keratometers, two-position machines that adjust object size. Some all-in-one automatic optical test systems include keratometry capabilities, while stand-alone keratometers are typically manual. The latter are often preferred by more experienced ophthalmologists and technicians who can minimize error while subjectively reviewing the surface of the cornea.
HANS HEISS
This brand has 2 models with all in one systems to add lensmeter and phoropter. It can be setup easy and in minutes. HRK8500 & HRK9000 - Both are within budget.
Autorefractometer w / Keratometer /HRK-8500
· REF/KER mode Continuous
· Refractometry and Keratometry
· REF mode Refractometry
· KER mode Keratometry
· CLBC mode Contact Lens Base Curve Measurement
· Cornea vertex distance (VD) 0.0, 12.0, 13.5, 15.0
· Spherical power (SPH) -25.00 ~ +22.00D (VD= 12mm) (0.12 / 0.25D step)
· Cylinder power (CYL) 0.00 ~ ±10.00D (0.12 / 0.25D step)
· Axis 1 ~ 180° (1° step)
· Cylinder indication -, +, MIX
· Pupil Distance (PD) 10 ~ 85mm
· Minimum pupil size Ø 2.0mm
· Cornea curvature radius 5.0 ~ 10.2mm (0.1mm step )
· Cornea power 33.00 ~ 67.50D (Cornea equivalence power=1.3375) (0.05 / 0.12 / 0.25D step)
· Cornea cylinder power 0.00 ~ -15.00D (0.05 / 0.12 / 0.25D step)
· Cornea cylinder axis 1 ~ 180° (1° step)
· Measurement cornea diameter 2.0 ~ 12.0mm (0.1mm step)
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Autorefractometer w / Keratometer /HRK-9000
Touch screen –color lcd- 10 measurements for each eye.
HRK-9000 provides an extensive dioptric measurement range (-25D to +22D), and the radius of curvature for keratometry is 5.0mm to 10.2mm. Easy alignment and friendly operation allows you to measure the refraction and keratometry in sequence, and the results can be validated immediately. Owing to its easy alignment and friendly operation you can measure the refraction and keratometry in a sequence, the results can be checked all at once.
Peripheral corneal curvatures can be measured by having the patient look at the peripheral eye fixation lamps. Measuring the corneal periphery will help you examine irregular astigmatism, and also determine a better fitting for a contact lens
Using the freeze function, measurement of the diameter of the cornea, pupil or hard contact lenses worn by the patient can be performed. By simply touching and dragging the screen with your finger measurements are exactly calculated.
By adopting high resolution VGA TFT-LCD with Touch Screen function, we virtually removed all input keys except the measurement button on the Joystick and chin-rest control switches. Tests are performed rapidly and conveniently by simply pressing a button or the icon indicated on the screen.
By simply touching the icon on the screen results of up to 10 measurements stored in memory can be viewed or printed by the built in thermal auto cut-off printer.
Simply touch the icon on the screen and changed settings can be seen. The touch screen supports interactive setting changes quickly and conveniently saving user time.
When refraction results in an error reading due to an interocular lens or cataract the measurement can be performed with the IOL icon switched 'ON'
The chin-rest is motorized with the use of a switch conveniently positioned for the operator. This makes for simple adjustment of the chin-rest from patient to patient.
Data can be transferred to external devices (personal computer, etc.) via an RS-232 interface. A USB interface is also provided for future compatibility.
Simply touch the -PRINT- icon on the screen and the HRK-9000 will immediately provide a complete printout of the measurement results. An Auto Cutter is provided for convenience.
Reunión virtual con el Dr. Julian Triviño (Colombia)
