Ocular biometry is a diagnostic technique that allows the ophthalmologist to know parameters and dimensions of certain parts of the eyeball.
This test is essential to know if a patient is a candidate to perform a cataract operation or a refractive surgery with intraocular lens implant.
Ocular biometry is a simple procedure that lasts a few minutes and does not require any type of preparation.
En Área Oftalmológica Avanzada we explain below what this diagnostic test consists of and how it is carried out.
What is eye biometrics?
The ocular biometrics is an examination that is performed to know different ocular parameters, such as the length of the eyeball, the measurement of the corneal curvature and the depth of the anterior chamber, the structure that is between the cornea and iris.
Ocular biometry is a simple test that does not cause any type of pain and calculates the measurements of the eye according to the behavior of light or ultrasound that go through the structure of the eyeball.
Types of ocular biometry
There are two different methods to perform an ocular biometry:
Optical biometry
Optical biometry, or IOL Master 700, is carried out through the projection of two light beams on the eyeball.
As the beams pass through the structures of the eye, the length between one part and another can be measured.
With this type of ocular biometrics you can obtain the axial length of the eye, the depth of the anterior chamber, the curvature of the cornea and the corneal diameter.
During the test five measurements are made to then take an average value of them. Optical biometrics is the method most used by ophthalmologists and offers the following advantages:
- There is no direct contact with the eye
- It is not necessary to use anesthesia or dilate the pupil.
- Measurement is very fast.
- No risk of infection
- The measurement system detects automatically if it is the right eye or the left eye. This considerably reduces the margin of error.
- Provides very accurate measurements, unless there are opaque spots around Cataracts or bleeding.
ultrasonic biometry
This type of biometry is carried out through a high frequency ultrasound beam that is directed through the cornea by direct physical contact or by immersing a probe in an aqueous environment generated through a bowl special for this purpose.
When ultrasounds pass through the ocular structure, they emit echoes that provide an image known as an echogram.
Through a series of calculations the ophthalmologist can obtain the space traveled by ultrasound from one structure to another. The total sum of the space results in the axial length of the eyeball.
Contact method
To perform an ultrasonic eye biometry the patient must sit in an armchair with a straight head. It is necessary to use topical anesthesia (in the form of drops) because the test is done by direct physical contact with the eye.
Once the patient is anesthetized, the ultrasound probe is placed perpendicular to the cornea to begin the echo and obtain at least five measurements of the eyeball.
Immersion method
It is done using topical anesthesia and stretching the patient on a stretcher.
The ophthalmologist will place, on the eye to be examined, a plastic cylinder filled with a fluid in which the probe will be submerged.
During the test, the patient must focus on the probe so that the measurements are made correctly.
This method of ultrasonic biometry is very accurate to obtain lengths in eyes with opaque media caused by cataracts.
When is an ocular biometry necessary?
Ocular biometry is performed when the ophthalmologist needs to know the measurements of the structures of the eye to determine the power of the intraocular lens that must be implanted in cataract surgery.
An ocular biometry is also performed to know the measurement of the inner chamber of the eye.
In these cases, the main objective of the test is that the ophthalmologist can decide if it is better to place a intraocular lens in front of the lens or in front of the iris during a refractive surgery.
Do you still have doubts about ocular biometry? In Área Oftalmológica Avanzada We are looking forward to meet and solve them. Contact us as soon as possible!
