One of the most serious consequences of chronic IH is vision loss, which can lead to blindness. Visual symptoms due to elevated intracranial pressure can range from grey spots that appear briefly to blurred or double vision to decreased contrast sensitivity and peripheral field loss. They also include “dim-outs,” in which vision is momentarily lost in one or both eyes, as well as total blindness. These symptoms can indicate papilledema (swollen optic nerves), which is a diagnostic sign of IH.
Regular eye exams to check for papilledema, along with visual field testing are necessary to monitor for any visual changes. Early signs of vision loss can be subtle and not always noticed. An enlarged blind spot is the most common visual field test abnormality with chronic IH. The second most common field defect occurs in the inferior nasal quadrant. Advanced vision loss often requires surgery to save sight.
The most common visual symptoms are:
Transient Visual Obscurations (TVOs): These are often described as momentary grey spots, or a dimming or blackout of vision that occur in one or both eyes, especially after a change in position (such as standing up from a seated position). TVOs are the most frequent visual symptom but are temporary; vision generally returns to the affected eye or eyes after the TVO episode, which lasts approximately 30 seconds to a couple of minutes. They may also be accompanied by pulse synchronous tinnitus.
Blurred vision: Blurred vision may be a direct result of papilledema and swelling in the surrounding retina. It can also be the result of a retinal hemorrhage.
Double vision (diplopia): Double vision can be due to sixth nerve palsy.
Decreased contrast sensitivity: Over time, chronic IH may affect the ability to perceive changes in contrast. Some with IH report examples of this decreased ability, such as the grey or faded out appearance of black text against a white background.
Blindness: Sudden or gradual blindness can occur as a result of severe papilledema. If damage to the optic nerve is extensive, blindness can be permanent. It can also be a rare complication of an optic nerve sheath decompression, the surgery performed to relieve pressure on the optic nerve and save sight. But in many cases, the surgery successfully relieves optic nerve swelling and improves or restores vision.
How does vision loss and blindness occur?
The optic nerve, which is located at the back of each eye, physically connects the eye to the brain. The subarachnoid space surrounds the nerve and continues up to the optic nerve head (also known as the optic disc or papilla) at the back of the eyeball. When intracranial pressure increases in this space, it squeezes the nerve, which impedes blood flow and causes the nerve to swell. Sustained papilledema can damage the optic nerve and lead to vision loss, including blindness.
Papilledema may sometimes be referred to as “swollen discs.” This is a reference to the disc-like shape of the optic nerve head. In the pictures below, a normal, healthy optic disc has clearly defined borders and is opalescent. An optic disc that shows papilledema has borders which are no longer clearly defined. It also appears physically elevated.
2. Moderate Papilledema
1. Normal Optic Disc
4. Severe Papilledema
with Retinal Hemorrhages
3. Severe Papilledema
Is it possible to have chronic IH without papilledema?
Yes. While papilledema may signify intracranial hypertension, not everyone develops it. Anatomy and other physiological factors can influence whether one develops papilledema. Additionally, some who do not initially have papilledema may develop it over time. Papilledema may be an indicator of IH but it is not “the indicator” of IH for every person.
Is it possible to have IH without papilledema and still be at risk for vision loss and blindness?
Yes. Elevated intracranial pressure can still affect the optic nerve. Regular visual exams are important for everyone with chronic IH since initial vision loss can be subtle. Vision field testing is a key tool for detecting any early visual changes.
Visual exams are usually conducted by a neuro-ophthalmologist or an ophthalmologist and consist of two parts: a physical examination of the eyes (including the optic nerves) and vision tests including visual acuity, contrast sensitivity, color vision and very importantly, a visual field test, which is a key tool for detecting any early visual changes.
What are the earliest signs of vision loss?
The most common early sign of vision loss due to papilledema is enlargement of the blind spot, followed by inferior nasal loss on a visual field test. Peripheral vision loss is an early sign, which is not always physically perceived. It is rare, however, for early visual loss to involve central vision.
Is all vision loss permanent?
Much depends on the extensiveness of vision loss and how quickly it is treated. The rule of thumb is the sooner vision loss is detected and treated, the better.