Glaucoma is a progressive eye disease that can be classified as early or mild, moderate, and advanced or severe based on the degree to which the condition has impacted vision and the structures in the eye.
Factors Used to Classify Glaucoma
To classify any case of glaucoma, three factors are utilized: the presence of a visual field defect, changes to the optic nerve, and loss of the retinal nerve fiber layer.
The main symptom associated with glaucoma is visual field loss or constriction. If there is a visual field defect, whether symptoms are present or not, the condition is considered more advanced.
Glaucoma damages the optic nerve and results in changes that can be viewed directly by an eye doctor in an eye exam. These changes may present before any other symptoms.
The retinal nerve fiber layer is the collection of nerves that send information to the optic nerve and the brain. These nerve fibers are damaged in glaucoma and are used as a main marker for diagnosing and classifying glaucoma.
Early or Mild Stage Glaucoma
Glaucoma in the earliest form is classified as early or mild stage. This stage is the first stage when a diagnosis of glaucoma instead of a glaucoma suspect is used.
At this stage, there may be very minor or focal visual field defects. These defects are not likely to result in symptoms of visual field loss.
Also, early optic nerve changes will likely be present at the early stage. These may be enough to diagnose glaucoma based on visualizing the optic nerve changes alone.
In early or mild stage glaucoma, there will be very minimal, if any, loss of the retinal nerve fiber layer.
Treating Early or Mild Stage Glaucoma
In all cases of glaucoma, the treatment consists of medications or surgeries to lower the intraocular pressure.
For a mild case of glaucoma, it is recommended that the intraocular pressure be reduced by at least twenty to thirty percent from the highest pressure it has ever been.
Moderate Stage Glaucoma
Glaucoma that has progressed beyond early or mild stage is considered to be moderate stage glaucoma.
In this stage, there may be large visual field defects in one half of the vision either the upper or lower portion. These defects will likely result in symptoms of vision loss or constriction.
Additionally, moderate glaucoma will present with definite changes to the optic nerve when viewed in an eye exam.
In moderate glaucoma, the retinal nerve fiber layer will show significant loss and damage when tested and evaluated. This damage will correspond to the visual field defect.
Treating Moderate Glaucoma
To treat moderate stage glaucoma, it is recommended that the intraocular pressure be reduced by thirty to thirty-five percent of the highest it has ever been.
While the recommendation is at least thirty percent, many doctors will set a target of reducing the intraocular pressure more than this to prevent risk if there is any further progression.
Advanced or Severe Glaucoma
The most progressed cases of glaucoma are classified as advanced or severe stage glaucoma.
In these cases, there is a high risk of permanent vision loss and blindness.
The visual field defects of moderate glaucoma are seen in both the upper and lower halves, creating a single central island of vision.
In advanced glaucoma, there may also be visual field defects in the central visual field.
The optic nerve will be irreparably damaged and show signs of longstanding high pressure.
The retinal nerve fiber layer will have multiple areas of loss and thinning.
Treating Advanced or Severe Stage Glaucoma
Treating advanced or severe stage glaucoma is the most concerning, given the high risk of vision loss.
While a percent reduction of thirty-five to forty-five percent can be ideal, it is generally considered that intraocular pressure that is typically in the low teens and never greater than eighteen is the most protective from more progression.