What is glaucoma?
Glaucoma is a degeneration of the optic nerve caused mainly, but not only, by an increase in the pressure of the intraocular fluid called aqueous humor. It is a slow and progressive disease that irreversibly damages the nerve fibers of the optic nerve, so its early detection is of utmost importance. Once detected, treatment must be individualized to achieve a fundamental objective: to halt the progression of the disease. For this purpose, there are treatments with different hypotensive drugs, laser therapy and various surgical techniques that allow lowering intraocular pressure.
Early detection of glaucoma
Chronic open-angle glaucoma is the most common type of glaucoma in the general population, accounting for up to 70% of all cases.250,000 Spaniards suffer from glaucoma, although almost 50% remain undiagnosed because it is a disease that has no symptoms.
For this reason, many early detection campaigns have been carried out in recent years and, in all of them, intraocular pressure is measured and the state of the optic nerve is assessed in different ways.
The presence of elevated intraocular pressure is usually related to optic nerve damage known as glaucoma. However, there are exceptions: not all patients with elevated ocular pressure will develop glaucoma in the future (but ocular hypertension) and not all patients with glaucoma have elevated ocular tensions (they may have glaucoma with normal tension). For this reason, early detection of glaucoma cannot be limited to intraocular pressure measurements, but must be accompanied by an in-depth analysis of the optic nerve and its anatomical and functional status.
In the hope of achieving an earlier diagnosis, exploratory techniques have recently been developed that make it possible to identify the disease earlier in order to avoid irreversible vision loss as soon as possible. All of them are part of the usual diagnostic protocol:
Perimetry or campimetry: allows the detection of visual defects in the visual field so it has been until now a fundamental pillar of glaucoma diagnosis, since the initial visual loss in glaucoma is detected in the mid-periphery and goes unnoticed by the patient. We currently use the Humphrey campimeter, with short duration programs that allow in less than 5 minutes to detect minimal visual defects of incipient glaucoma.
In order to increase the sensitivity of campimetry and detect the disease at earlier stages we have introduced other tests into our practice such as short wavelength field of view (PALOC, also called blue-yellow campimetry) and dual frequency perimetry (FDT).
Optical Coherence Tomography (OCT): widely used in retinal analysis, it is a new non-invasive method for the early diagnosis of glaucoma. A near-infrared light beam is used to measure the thickness of the optic nerve fiber layer and, after a scan lasting a few minutes, diagrams of the thickness of the retinal nerve fiber layer are defined, allowing us to detect patients with very early stage glaucoma.
Confocal Scanning Tomography (Heidelberg Retinal Tomography-HRT II): quantifies the image of the optic nerve and mathematically detects subtle changes in its shape and thickness. Thus we obtain a topographic map of the optic nerve in its intraocular portion, known as papilla. This high-resolution spatial map is analyzed by our technicians and recorded for later comparisons. In this way we detect changes over time and identify the dreaded progression of glaucoma.
Serial retinographs: these are microphotographs of the optic nerve papilla that allow us to record its appearance to help us in the diagnosis of the disease and in its follow-up by comparing different images throughout the time of evolution of the disease. These photographs can even be stereoscopic (in relief) to help in a better visualization of the volumes of the papillae. They are made with special filters that can capture the retinal nerve fiber layer and its defects.