Glaucoma is a group of eye diseases that cause progressive damage to the optic nerve, the structure responsible for transmitting visual information from the eye to the brain. This damage leads to irreversible vision loss, often beginning in the peripheral visual field. A consistently elevated pressure inside the eye, known as intraocular pressure (IOP), is the most significant risk factor for developing this condition. Controlling IOP is the only proven method to prevent the ongoing deterioration of the optic nerve and preserve sight. The primary goal of management is to lower the IOP to a level that halts the disease’s progression.
Understanding Normal Intraocular Pressure
The eye maintains its internal environment through the continuous circulation of aqueous humor, a clear fluid produced by the ciliary body. This fluid flows into the front of the eye and drains out through the trabecular meshwork. Intraocular pressure (IOP) is the balance between fluid production and drainage resistance, measured in millimeters of mercury (mmHg) using tonometry.
For eyes without glaucoma, the typical normal range falls between 10 and 21 mmHg. This range does not guarantee protection, however. A susceptible optic nerve can be damaged even at these levels (normal-tension glaucoma), while some healthy eyes tolerate pressures above 21 mmHg without damage.
Defining Your Individualized Target Pressure
There is no universal “good” eye pressure number for a person diagnosed with glaucoma. Eye care professionals determine a highly personalized “target pressure” or target IOP range. This dynamic goal represents the pressure level expected to stabilize the optic nerve and prevent further vision loss, based on a comprehensive assessment of patient-specific factors.
The most influential factor is the extent of existing optic nerve damage, categorized as mild, moderate, or severe. More advanced damage requires a significantly lower target pressure to slow the disease. For example, a patient with mild glaucoma might aim for a target in the mid-to-high teens (15–17 mmHg), while a patient with severe vision loss may need a much lower target, often in the low teens (10–12 mmHg).
The target is also frequently defined as a percentage reduction from the initial, untreated pressure reading. An initial IOP reduction of 25 to 40% from baseline is often suggested to reduce the risk of progression. Other considerations influence the final individualized target, including the patient’s age, life expectancy, type of glaucoma, corneal thickness, and the past rate of damage progression.
Treatment Options to Reach Target IOP
Achieving the necessary IOP reduction uses a tiered approach, starting with the least invasive methods. Topical medications are the most common first-line treatment. Prostaglandin analogs, such as latanoprost, work primarily by increasing the unconventional outflow of aqueous humor through the uveoscleral pathway.
Other medications, including beta-blockers and carbonic anhydrase inhibitors, decrease the rate of aqueous humor production. If medications are insufficient or poorly tolerated, laser procedures are employed. Selective Laser Trabeculoplasty (SLT) is an office-based procedure that uses low-energy laser light to stimulate the trabecular meshwork, enhancing the eye’s natural drainage capacity.
When the target pressure cannot be maintained with drops and laser, surgical intervention is necessary. Trabeculectomy is the most established surgery, creating a small opening in the eye wall to allow aqueous humor to bypass the blocked drainage system. Glaucoma drainage implants, consisting of a tube connected to a small plate, are an alternative that diverts fluid to a reservoir on the eye’s surface.
Monitoring and Adjusting Glaucoma Management
Glaucoma is a chronic, lifelong condition requiring continuous assessment to confirm the target pressure is effectively protecting the optic nerve. Routine monitoring involves repeated IOP measurements using tonometry to ensure the pressure remains within the target range.
Structural changes are tracked using Optical Coherence Tomography (OCT), which quantifies the thickness of the retinal nerve fiber layer that thins as the disease progresses. Visual field testing is also performed periodically to assess the functional impact of the disease by mapping peripheral vision.
If monitoring reveals the optic nerve is continuing to thin or visual field loss is worsening despite achieving the initial target, the current pressure is too high. In this case, the target pressure must be lowered further, often by adding new medication or moving to a more aggressive treatment like laser or surgery.