Determining Implant Power

Once you are told you will need cataract surgery, you will need to have measurements taken of your eye. These measurements are required to calculate the power of the implant that is placed into the eye at the time of surgery. The types of measurements taken for each patient are determined on severity of the cataract.

The measurements consist of:


Keratometry measures two corneal curvatures, the steepest and the flattest. These measurements give the doctor information about the cornea’s curvature, focusing power and whether astigmatism is present.


Corneal TopographyCorneal topography also measures the corneal curvature assisted by computer analysis. A corneal topographer projects a series of illuminated rings onto the corneal surface, which are reflected back onto the instrument. These reflected rings of light are analyzed by the computer and a topographical map of the cornea is generated. The topographical map and computerized analysis reveals any distortions of the cornea, disease, scarring as well as the corneal curvature.

IOL Master

IOL MasterDr. Tayfour offers a new high tech measurement tool, “The Zeiss Humphrey IOL Master”, a state of the art laser system that evaluates the length of the eye, surface curvature and intraocular lens power.

The IOL Master is very efficient because it allows technicians to take all measurements with complete confidence in the accuracy of the results. The measurements are done without touching the eye and all within a one minute period. There is no need for anesthesia and there is no potential for spread of contamination from the instruments.


Ultrasound utilizes sound waves to form an image of the eye. High frequency sound waves are emitted from a probe. The sound waves travel through the eye, reflect from the eye structures and back to the probe. The probe receives the sound waves and converts them into the image that appears on the examiner’s screen.

Ophthalmic ultrasound is used to measure the parts of the eye, document pathology such as tumors, and examine the inside of the eye.

The A-Scan measurement is most commonly used to measure the eye length to determine the intraocular lens for cataract surgery.