Ocular biometry is a test that measures the dimensions of the eyeball: the axial length (distance between the anterior and posterior parts of the eye) and the depth of the anterior chamber (part between the cornea and the iris and lens). It is also used to measure the thickness, the curvature and the diameter of the cornea.
This test determines the precise dimensions of the eye where an intraocular lens is to be implanted.
The test must be performed extremely precisely, as it will be used to determine the exact measurement of the intraocular lens to be implanted in the eye.
How is it performed?
Ocular biometrics are performed according to two techniques:
- Ultrasound biometry (ultrasound emitted into the cornea, requiring contact with the cornea and anaesthesia. It is invasive for patients and takes longer to perform by specialists)
- IOL MASTER optical biometry (uses infra-red laser light, is not invasive for patients who feel noting and no anaesthetic or dilating eye drops are required).
Optical biometry is the most commonly used at present, as it provides a more precise calculation except in very specific cases (very opaque lenses).
4 keys to biometry
- It is a painless test.
- Pupil dilation is not necessary.
- You must not wear contact lenses for 48 h beforehand.
- Test duration: 15 minutes.
What diseases can be diagnosed?
This test is necessary for:
- Cataract and presbyopia surgery (lenses replacing the ageing lens).
- In surgery correcting refractive defects (myopia, hyperopia, astigmatism, etc.) with Phakic lenses (that do not replace the lens).
The power of the lens to be implanted is calculated based on its results.