What is FDT perimetry?

FDT perimetry (English acronym for Frequency Doubling Technology) is a technology that examines the sensitivity of a particular population of retinal neuronal cells, called type "My" (representing 3.5% of the total retinal nerve cell). These cells are the first cells to suffer and lose their function in the event of damage from glaucoma.

What is the purpose of FDT perimetry?

It is used to evaluate any alterations or deficit in the normal field of vision caused by certain eye diseases, including glaucoma. It is usually required for patients with suspected glaucoma who’ve had normal results of the conventional visual field examination.

How is the exam performed?

The patient sits in a chair and rests his head on a machine. The patient is blindfolded on the left eye and given a remote control to press every time he/she sees a grid projected on the screen of the machine (a set of black and white bars, projected in a certain portion of your field of vision). It is important that the patient moves a black dot along the screen of the machine to facilitate the examination and make it more reliable by cooperating. After examining the right eye, you proceed the same way with the left eye. The test result is ready in minutes.

Which patients can undergo the exam?

All patients can undergo this exam: it is quick and easier than the conventional visual field examination.

Is FDT perimetry painful or dangerous?

The exam is painless and not dangerous.


Preparation standards


The exam does not require any special preparations: the patient is not required to fast; however, the patient is required not to put any eye drops before or during the exam. The patient should always carry their glasses with them, because if the visual defect exceeds a certain size the test is conducted with the help of their glasses.