The pachymetry is an ophthalmological test that measures the thickness of the cornea, the clear membrane located at the front of the eye.
The cornea generally measures around 500 or 600 microns in the central area, and between 600 and 800 in the peripheral area. It is important to know the thickness of the cornea before certain types of surgery are performed. It is also a factor to be considered in the diagnosis and monitoring of certain corneal diseases or in cases of glaucoma.
How is it performed?
The test is performed using ultrasounds directed at the central part of the cornea, using a probe called a pachymeter (ultrasound pachymetry).
It is also possible to measure corneal thickness using an optical coherence tomography or OCT, which uses a laser for measuring and requires no contact with the surface of the cornea.
4 keys to the pachymetry
- It is a simple test but requires contact with the surface of the eye, which is why anaesthetic eye drops are applied to avoid discomfort.
- It can be performed with the pupil dilated or not dilated.
- Contact lenses should not be worn for more than 7 days beforehand.
- Duration of this test: 5 minutes.
What diseases can be diagnosed?
- Monitoring of patients with glaucoma, as corneal thickness changes the measurement of intraocular pressure, which must be adjusted.
- To prepare for refractive surgery and its post-operative monitoring (operations to correct refractive defects with laser techniques).
- To track the evolution of corneal diseases (corneal oedema, dystrophies, keratoconus, etc.).
- To prepare for and track corneal surgeries (corneal transplantation).