Glaucoma is a group of eye diseases defined by progressive damage to the optic nerve, the bundle of fibers that sends visual information to the brain. This damage is most often associated with elevated pressure inside the eye, known as intraocular pressure (IOP). The core question of whether this condition can be limited to one eye has a clear answer: it is possible for glaucoma to be present in one eye while the other remains healthy.
Yes, Glaucoma Can Affect One Eye
The presentation of glaucoma, whether unilateral (one eye) or bilateral (both eyes), depends heavily on its underlying cause. Glaucoma is broadly categorized into Primary Glaucoma and Secondary Glaucoma. Primary glaucoma, such as Primary Open-Angle Glaucoma (POAG), is the most common form and typically has no identifiable external cause, often running in families. Because this form is linked to systemic or genetic risk factors, it affects both eyes, though the damage may progress unevenly.
Secondary Glaucoma occurs when an external event or a localized medical condition triggers the rise in intraocular pressure and subsequent optic nerve damage. This localized trigger allows the condition to be confined entirely to one eye. For instance, an injury or inflammation that only affects one eye will create a unilateral condition. Secondary Glaucoma is the primary reason for a unilateral case.
Specific Forms of Glaucoma That Are Unilateral
Secondary Glaucoma can be isolated to a single eye because the cause is localized. Trauma-induced glaucoma develops following a significant blunt or penetrating injury to the eye. Such an injury can directly damage the eye’s drainage system, the trabecular meshwork, causing it to become less efficient at filtering fluid and leading to a pressure spike only in the injured eye. This damage can manifest immediately or even years after the initial incident.
Inflammatory or uveitic glaucoma occurs when inflammation blocks the fluid drainage channels. If the inflammation is confined to one eye, the resulting pressure increase will be unilateral. Neovascular Glaucoma is triggered by the growth of abnormal new blood vessels across the drainage angle, often due to localized retinal problems like a retinal vein occlusion. These new vessels mechanically obstruct the outflow of fluid, leading to high pressure specific to that eye.
Steroid-induced glaucoma is often unilateral, particularly when corticosteroid eye drops are prescribed for a condition affecting only one eye. Some individuals are considered “steroid responders,” meaning their intraocular pressure rises significantly when exposed to the medication. If the steroid is applied to one eye, the pressure elevation and resulting glaucoma will only occur in that eye.
Monitoring the Unaffected Eye
Even when a clear, localized cause points to a unilateral diagnosis, the unaffected eye still requires careful monitoring. This is because a person with glaucoma in one eye often possesses underlying risk factors that could affect both eyes over time. The unaffected eye is considered “at risk” and is managed proactively to prevent future damage.
Monitoring involves a series of diagnostic tests performed regularly to detect the earliest signs of optic nerve stress. Ophthalmologists will perform tonometry to measure the intraocular pressure, watching for even subtle elevations that may signal the beginning of a problem. They also conduct visual field testing to map out the peripheral vision, looking for subtle blind spots that the patient may not yet perceive.
Optical Coherence Tomography (OCT) provides detailed images of the optic nerve head and the Retinal Nerve Fiber Layer (RNFL). This imaging allows the eye care professional to measure the thickness of the nerve fibers, as thinning in the RNFL can be one of the earliest indicators that glaucoma is starting to develop. Consistent follow-up and testing, often every three to six months, ensure that any change is caught immediately, allowing for prompt treatment to preserve vision.