See an ophtalmologist: detection and follow-up
Glaucoma is often a painless and insidious disease that leads to visual disability undetected by the patient until the disease is already advanced. Only an ophthalmologist, through regular exams, can detect and treat correctly glaucoma. Those exams are essential if your tension has risen, if members of your family suffer from glaucoma or if you are more than 40 years old.
1. Tonometry (mesure of intraocular tension)
In order to perform this exam, the cornea is anesthetized with an eye drop and the intraocular pressure is painlessly measured with a small device, the tonometer.
A value above 21 mm Hg is considered abnormal. The tension of the eye can be measured as well with a tonometer with “pulsed air” that projects, without using anaesthetic drops, a small amount of air in the cornea. This method is not very precise.
Your ophthalmologist may perform a gonioscopy if glaucoma is suspected to look at the trabeculum, the zone where aqueous humor leaves the eye to distinguish between open angle and closed angle glaucoma.
3. Exam of the optic Papilla (optic nerve)
With an ophthalmoscope, your ophthalmologist can observe the head of the optic nerve on the back of the eye or the optic nerve head. The colour and three-dimensional configuration of the nerve head will help your ophthalmologist decide whether there are lesions from glaucoma.
When there is a loss of optic nerve fibres, the optic nerve head typically has a depression or abnormal “cup” which is characteristic for glaucoma. The loss of vision is proportional to the severity of the cupping and the disappearance of neural tissue.
Photography of the optic papilla can be very helpful in order to follow the evolution of the disease.
4. Exam of the visual field
In case of glaucoma or suspicion of glaucoma, a visual field will be performed to detect any deficits. Every eye is tested separately. This test allows evaluating the peripheral vision.
This exam is like a video game and tests the peripheral vision by projecting lights. During the exam, the patient looks at a small central target and indicate whether is a light projected in the side visual field is seen by pressing on a button. In this way, a map of the visual field is made.
The exam of the visual field allows detecting glaucoma early before the patient realises there is any alteration of the visual field.
5. Corneal pachymetry
Corneal pachymetry is a painless simple and fast measurement of the thickness of the cornea with the help of an instrument: the pachymeter. The thickness of the cornea is about 540 microns. The corneal thickness affects the measurement of the intraocular tension. A thin cornea causes underestimation of the ocular tension, whereas a thick cornea causes an overestimation. The thickness of the cornea has to be taken under consideration when we measure the ocular pressure.
6. Colour vision
Colour vision is normally intact in glaucoma, unlike cataract or optic neuropathy where there can be troubles on colour perception. Only in very advanced glaucoma with central vision loss, a reduction in colour perception may be present.
7. Automatic analysis of the optic nerve with optic nerve head oct
In certain cases, photos of the optic nerve analysed by a computer to make a topographic map, which can help improve the treatment and follow-up of the disease. This is called optic nerve head OCT.
Depending the gravity of the problem the exams are done 1 to 4 times per year.