Biometry is the method of applying mathematics to biology. The term was originally used by Whewell in
the 1800s for calculating life expectancy. The refractive power of the eye primarily depends upon the
cornea, the lens, the ocular media, and the axial length of the eye. When planning for cataract surgery,
in order to achieve the desired post-operative refraction, the required power of the intraocular lens
(IOL) implant can be calculated if the corneal refractive power, media type, and axial length are known.
4 keys to biometry
1. It is a painless test.
2. Pupil dilation is not necessary
3. You must not wear contact lenses for 48 h beforehand.
4. Test duration: 15 minutes.
What diseases can be diagnosed?
This test is necessary for:
Cataract and presbyopia surgery (lenses replacing the aging 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.
Biometry for Intra-Ocular Lens
(IOL) Powerhow can we use the Biometry test?
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 (the part
between the cornea and the iris and lens). It is also used to measure the thickness, curvature, and
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 anesthesia. It is invasive for patients and takes longer to perform by specialists)
• IOL MASTER optical biometry (uses infrared laser light, is not invasive for patients who feel
nothing, and no anesthetic or dilating eye drops are required).
Optical biometry is the most used at present, as it provides a more precise calculation except in very
specific cases (very opaque lenses).