Glaucoma, a silent blindness
Written by:What is glaucoma?
Glaucoma is a degeneration of the optic nerve produced mainly, but not solely, by the increased 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 that its early detection is of utmost importance. Once detected, the treatment must be individualized to achieve a fundamental objective: to stop the progression of the disease. For this purpose there are treatments with different hypotensive drugs, laser therapy and various surgical techniques that allow intraocular pressure to decrease.
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. Some 250,000 Spaniards have glaucoma , although almost 50% remain undiagnosed because it is a disease that does not have symptoms .
This is why there have been many early detection campaigns carried out in recent years and in all of them, intraocular pressure is measured and the state of the optic nerve is evaluated in different ways.
The presence of elevated intraocular pressure is usually related to the damage of the optic nerve that we know as glaucoma. However, there are exceptions: not all patients with elevated eye pressure will develop glaucoma in the future (but ocular hypertension) and not all patients with glaucoma have elevated eye strain (they may have normal-tension glaucoma). Therefore, the early detection of glaucoma can not be limited to the taking of intraocular pressure 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 , recent exploratory techniques have been developed that allow the identification of the disease in advance to avoid as soon as possible the irreversible loss of vision. All of them are part of the usual diagnostic protocol:
The perimetry or campimetry : allows to detect visual defects in the visual field so it has been hitherto fundamental pillar of the diagnosis of glaucoma, since the initial visual loss in glaucoma is detected in the middle periphery and goes unnoticed for the patient. At present we 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 the campimetry and detect the disease in earlier stages we have introduced in our practice other tests such as the short wavelength visual field (PALOC, also called blue-yellow campimetry) and double frequency perimetry (FDT).
Optical Coherence Tomography (OCT) : widely used in retinal analysis, 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 fiber layer of the optic nerve and, after a few minutes' exploration, the thickness of the nerve fiber layer of the retina is defined, allowing us to detect patients affections of very early glaucoma.
Confocal Scanning (Heidelberg Retinal Tomography-HRT II) Positron quantifies the image of the optic nerve and mathematically detects subtle changes in shape and thickness. Thus we obtain a topographic map of the optic nerve in its intraocular portion, known as papilla. This spatial map of high resolution is analyzed by our technicians and registered for later comparisons. In this way we detect changes over time and identify the dreaded progression of glaucoma.
Serial retinographies : these are photomicrographs of the optic nerve papule that allow us to record their appearance to help us in the diagnosis of the disease and its follow-up by comparing different images over the time of disease progression. These photographs can even be stereoscopic (embossed) to aid in better visualization of papilla volumes. They are made with special filters can capture the layer of nerve fibers of the retina and its defects.
