How do you calibrate a keratometer?
Procedure
- Place a sheet of white paper over the back of the keratometer.
- Turn on the instrument.
- Rotate the eyepiece fully counterclockwise.
- While keeping both eyes open, turn the eyepiece in the clockwise (plus) direction until the crosshairs come into sharp focus, then stop.
How accurate is keratometer?
The reliability of the keratometry depends on the repeatability, reproducibility and on the validity of the keratometry measurements. In our study, the COR of the mean keratometric power was ±0.21 D for the auto keratometer, ±0.20 D for the manual keratometer, ±0.32 D for the Pentacam, and ±0.22 D for the IOL master.
How is the calibration of a manual keratometer checked?
Measure the test sphere. If the reading on the horizontal and vertical measuring drums matches the designated diopter value of the sphere (plus or minus an eighth of a diopter), then you are finished! You have checked the calibration of the keratometer and it has been found to be accurate.
What is the normal range of keratometer?
Results: The average K was 43.57, with a range of 38.25 to 50. The average axial length was 24.04, with a range of 18.4 to 31.91. More than 90% of K values were between 40.5 and 46.5; and more than 90% of the axial lengths were between 22.5 and 26.5 mm.
What is the principle of keratometer?
It is based on the fact that anterior surface of the cornea acts a convex mirror and size of the image depends on the curvature of the cornea. So, image size is varied with the curvature of the cornea. Helmholtz Doubling Principle Keratometer: Here, two rotating prisms are present and create an angle with each other.
How does keratometer work?
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.
What is K1 and K2 in Keratometry?
Keratometric changes with cycloplegia. K1: flat meridian of the anterior corneal surface, K2: steep meridian of the anterior corneal surface.
What does the keratometer actually measure?
1. A keratometer. This device measures the curvature of the anterior corneal surface based on the power of a reflecting surface. It does this by measuring the size of an image reflected from 2 paracentral points and utilizes doubling prisms to stabilize the image enabling more accurate focusing.
What does the keratometer measure?
A keratometer. This device measures the curvature of the anterior corneal surface based on the power of a reflecting surface. It does this by measuring the size of an image reflected from 2 paracentral points and utilizes doubling prisms to stabilize the image enabling more accurate focusing.
Is K1 vertical or horizontal?
Abbreviations: pre, preoperative examination; post, postoperative examination; k1, vertical keratometry; k2, horizontal keratometry.
What should I do if my keratometer is out of calibration?
If you find the keratometer to be out of calibration, the instrument should be calibrated by a professional ophthalmic equipment technician.
What is a keratometer used to measure?
A keratometer, also known as an ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, which is used to assess the amount and axis of astigmatism. A very popular and reliable type of manual, one-position keratometer (commonly known as a Bausch and Lombtype keratometer) is shown in Figure 1.
How do I adjust the eyepiece on my keratometer?
If you do not adjust the eyepiece, you may think that your keratometer is out of adjustment when it may not be. Place a sheet of white paper over the back of the keratometer. The white background will better highlight the crosshairs when viewed through the eyepiece. Turn on the instrument. Rotate the eyepiece fully counterclockwise.