What do you need to know about ocular biometry?
Ocular biometry is an examination that measures the length of the eyeball. This investigation is used to calculate the strength of the artificial lens to be implanted in the eye of a patient diagnosed with cataract.
Biometry can be ultrasonic or optical. Ultrasonic biometry involves the use of an ultrasonic transmitter, which is attached to the eye using a probe. Optical biometry uses lasers for measurements and contact with the patient’s eye is avoided.
Ocular biometry measures the dimensions of the eyeball: axial length (the distance between the anterior and posterior parts of the eye) and anterior chamber depth (the part between the cornea and iris and the lens). It is also used to measure the thickness, curvature and diameter of the cornea. This test determines the precise dimensions of the eye in which an intraocular lens is to be implanted.
What does ocular biometry involve?
Ocular biometry is performed according to two techniques:
Ultrasound biometry – ultrasound emitted into the cornea, requiring eye contact and anesthesia. It is invasive for patients and takes longer to perform.
IOL MASTER optical biometry – uses infrared laser light, is non-invasive to patients and no anesthetic or dilating eye drops are required.
Optical biometry is the most commonly used today because it provides a more accurate calculation, except in very specific cases (crystalline lenses strongly affected by cataract, very opaque).
IOL MASTER technology uses infrared cameras to capture the unique patterns of the eye. These patterns are then converted into a template, providing automatic near 100% fit rates for the artificial lens.
Recognition scanners work by illuminating the iris with invisible infrared light, detecting and excluding eyelashes, eyelids and specular reflections that usually block parts of the iris.
When is ocular biometry used?
This investigation is necessary for:
Cataract and presbyopia surgery by lens implants (artificial lens that replace opaque or aged natural lens).
Surgery to correct refractive errors (myopia, hypermetropia, astigmatism, etc.) with artificial lens.