Blurry Vision After Concussion: Why the Eye Exam Is Normal

Why Is My Vision Blurry After a Concussion if Nothing Is Wrong With My Eyes?

A standard eye exam asks 1 main question of each eye: how small a letter can it read, and does a lens make the letters sharper? After a concussion the answer is almost always the same as before the injury. In a meta-analysis of 22 publications on traumatic brain injury without a direct injury to the eye, the pooled rate of lost visual acuity was 0.0%, with the upper end of the confidence interval at 1.1% (Merezhinskaya, 2019). In a chart review of 83 patients under 21 whose symptoms had lasted, all 83 had normal visual acuity, and 89% had a receded near point of convergence, meaning their eyes gave up holding a single image farther from the face than they should (Raghuram, 2019). The exam came back normal because it measures the part that didn't break.

What it doesn't measure is control. The same meta-analysis found accommodative dysfunction, trouble focusing the lens, in 42.8% of people with TBI, and convergence insufficiency, trouble aiming both eyes at a near target, in 36.3% (Merezhinskaya, 2019). A letter chart holds still at 1 distance and lets you read it 1 eye at a time, so it never asks the 2 eyes to work together or the lens to shift.

How common the problem is depends on who was measured, and the numbers shouldn't be blended. Among 103 adults with post-concussion syndrome 2 to 6 months after the injury, 20.4% had symptomatic convergence insufficiency, and those who did carried a higher load of non-visual symptoms too (Nisted, 2024). Among 113 adolescents aged 11 to 17 who were still symptomatic 4 to 12 weeks after a concussion, 70% had at least 1 oculomotor diagnosis, convergence insufficiency and accommodative insufficiency each showed up in 35%, and 47% had more than 1 diagnosis (Scheiman, 2021). At the far end, of 160 people with TBI referred to an optometry clinic because they had vision symptoms, 90% had an oculomotor dysfunction, most often accommodative and vergence deficits (Ciuffreda, 2007). That last figure describes people who were sent for vision problems, so it says how often a vision complaint has a measurable cause behind it, and nothing about concussions in general.

The eyes check out fine, and the trouble sits in how the brain controls them. Why that control can stay off for months is on do concussions heal on their own.

Which Kind of Blur Do You Have?

Blur is 1 word for at least 5 different problems, and the first job in our team's exam is sorting which one you have. Our team walks through all 5 in the video.

Alignment

Both eyes are meant to point at the same target so the brain can lay the 2 pictures on top of each other. When they sit slightly askew, the target lands as a faint split, and a faint split reads as blur. A wider split reads as double. Vergence disorders, the family that covers this, were the most common oculomotor finding in the adolescent study, present in 60% (Scheiman, 2021). The near point of convergence, the closest distance at which the eyes can still hold 1 image, sits farther out after mild TBI: across 12 studies covering 444 people with mild TBI and 881 controls, the pooled effect size was 0.98 (Mani, 2022). So things blur up close first, and in our team's experience the same thing can happen looking far. How the eyes turn in, and what that costs you over a page of reading, is on dizzy when reading.

Before injury After concussion

Replay

Fatigue with movement

Reading and scrolling ask the eyes to jump, land and hold, over and over. As they tire, each landing gets less accurate, and the brain reads an inaccurate landing as blur. That fatigue has been measured: in 26 adults followed from 4 to 14 months after a mild TBI, visual fatigue rose significantly within a single testing session, at both visits (Möller, 2025). If the page is sharp when you start and soft 10 minutes in, this is the pattern.

The neck

Turn your head, pitch it forward, tilt it back, and read the same line. If the line goes blurry with the head move, in our team's view the neck is talking to the central vestibular system and changing where the eyes sit. How the neck reaches the brain is on neck problems and the brain.

Blood flow

The blood that comes up into the brain also comes up into the eye. In our team's view, when that flow blanches or is restricted, 1 eye blurs, and you notice it most by comparing 1 eye to the other. Blur that arrives when you stand up is covered on why vision goes black when standing.

The lens and the pupil

A lens that won't relax after close work, a lens that has lost flexibility, or a pupil that can't engage well will each blur the picture. Focusing can be unstable too. In a published case series, 1 patient's focusing power swung by 1.5 diopters 10 times in 4.2 seconds of recording, 28 months after the injury, and a second had variable blur 7 years after; the authors concluded that focusing stability should be measured in anyone complaining of blurry vision (Houston, 2021). Pupils that don't match or don't react are a different question, covered on pupils different sizes after a head injury.

Why Is It Blurry or Foggy in Just One Eye, and Why Does It Come and Go?

A patient asked our team about foggy vision in 1 eye only, and the first question our team asks is whether that's new. Fog in 1 eye that has always been there is usually the optics of that eye, and that goes to an optometrist or ophthalmologist. Fog that started after a brain injury, and especially fog that comes and goes, is the kind our team wants to see.

In our team's view, the retina is the camera. When the blood flow or the activity behind 1 eye sputters, in the ophthalmic artery or on 1 side of the brain, the picture from that camera fogs, because the retina either isn't getting enough fuel or isn't transmitting cleanly to the back of the brain. That's the clinic's working model, built from what changes the fog in the exam room. The studies on this page measure focusing and eye teaming, not 1-eye fog, so the model is our team's view and hasn't been measured.

Why it comes and goes, and why it's often worse at night or after a screen day, our team thinks of as bandwidth. In the words of 1 of the clinic's videos, "as the system gets tired, the ability to maintain perfusion also gets tired." A lens stuck in an accommodation spasm after hours at a computer does the same thing from the other direction, because it won't relax back to normal vision. Both get better and worse with the state of the system, which is why the fog isn't constant.

That pattern is what makes our team take it seriously. Blur that comes and goes, or changes with movement or head position, is what the clinic looks at hardest after a brain injury. Blur that is steady and the same in every position is more likely a prescription question.

Why Do I See Double After a Concussion?

Double vision is the alignment problem at a larger size. When the 2 eyes land on 2 spots instead of 1, the brain can't overlay the pictures and shows you both. Sharpness is intact in these studies (Merezhinskaya, 2019), which points at the aiming. Vergence disorders were the most common oculomotor finding in adolescents still symptomatic at 4 to 12 weeks, in 60% of them (Scheiman, 2021), and in our team's experience the same eyes that drift apart on a close target are the ones that split a far one when they're tired.

In our team's view, double vision that builds over the day or shows up only when you're tired or reading fits the fatigue pattern. Double vision that is new, sudden or constant after a hit belongs with the red flags under when to see an eye doctor.

How Long Does Blurry Vision Last After a Concussion, and Does It Go Away on Its Own?

Part of it does. The follow-up study that measured 26 adults at 4 months and again at 14 months after a mild TBI found that symptom scores improved, and that 2 functions recovered on their own: vergence facility, the speed at which the eyes switch between near and far, and smooth pursuit, following a moving target. Near point of convergence, near fusion, distance fusion, heterophoria and dynamic visual acuity did not recover over that year (Möller, 2025). People felt better, and several of the measurements didn't move.

Recovered on its own Did not recover

Did not recover between 4 and 14 months

• Near point of convergence. How close a target can come before the eyes stop holding 1 image.
• Near fusion. How much misalignment the eyes can absorb up close and still see 1 image.
• Distance fusion. The same reserve, looking far.
• Heterophoria. Where the eyes rest when they aren't forced to work together.
• Dynamic visual acuity. How sharp things stay while the head moves.

The receded near point looks the same at every age and every distance from the injury. Across the 12 studies in the meta-analysis, the effect didn't differ by age or by how long after the injury people were measured (Mani, 2022). Unstable focusing has been recorded at 28 months and at 7 years, in 2 published cases (Houston, 2021). Light sensitivity runs on its own clock: of 62 people aged 18 to 40 seen at an optometry clinic after mild TBI, half improved over time, most of them after the first year, and the authors suggested tinted lenses may slow that adaptation (Truong, 2014). Light sensitivity has its own page.

So the honest answer to "does it go away" is that some of it does and some of it doesn't, and the parts that don't are the parts worth measuring. Our team's position is that a function that hasn't recovered on its own after months needs a specific input, and finding which one is the work. Why symptoms can last is on do concussions heal on their own.

What Shows Up on a Full Exam That the Eye Exam Misses?

The first is eye movements. In 36 people with post-concussion syndrome examined a mean of 140 days after the injury, performance on anti-saccades, self-paced saccades, memory-guided sequences and smooth pursuit was worse than in 36 matched people with the same injury who had recovered well, and several of the measures that separated them are beyond conscious control (Heitger, 2009). Those movements can't be faked in either direction, which is why our team measures them.

The second is the near point. Of 108 adolescents with symptoms past 28 days, 62% had a concussion-related vision disorder on a comprehensive vision exam, and on eye tracking the near point of convergence break separated the 2 groups, 5.5 cm against 3.9 cm (Master, 2025).

The third is the sorting. A receded near point and convergence insufficiency aren't the same finding. Of the 74 patients with a receded near point in the chart review, 95% had an oculomotor disorder, and within those, 41% had an accommodation problem only, 28% had both accommodation and convergence problems, and 8% had convergence insufficiency alone (Raghuram, 2019). Screening in a physician's office caught convergence and accommodative insufficiency 43 to 63% of the time, depending on the measure (Scheiman, 2021). In our team's reading, a quick near-point check can send you to the wrong exercises, and a negative screen can't clear you.

What a functional exam measures, and what the results change, is on concussion testing: what to expect, and the circuits behind each kind of eye movement are on what part of the brain controls eye movements.

Does Vision Therapy Work After a Concussion?

For convergence insufficiency it works well, and the trial is recent. In the CONCUSS trial of people aged 11 to 25 with symptoms 4 to 24 weeks after a concussion, 88% of those who started office-based vergence and accommodative therapy right away were classed as successful or improved, against 8% of those who waited, and the near point improved 7.9 cm against 1.8 cm (Alvarez, 2026); dizzy when reading covers the trial in more detail. Once both groups had their 16 sessions, no significant difference remained. Of those trial participants, 79% also had an accommodative disorder (Scheiman, 2026), so focusing and teaming usually travel together.

Everyday practice is less tidy. In 2 private practices that saw 218 people after a concussion, 46% of the 175 offered therapy either never started it or never finished it. Of those who completed it, 85% with convergence insufficiency were successful and 15% improved; with accommodative insufficiency, 33% were successful and 67% improved (Gallaway, 2017). Therapy aimed at focusing is less reliable than therapy aimed at teaming, and nearly half of the people sent never get a result at all.

In our team's view, exercises aimed at the eye alone can miss what's driving the blur when the blur moves with your head, your neck or your breath, and that's why the sorting comes first. What the clinic does with what it finds is on post-concussion syndrome treatment.

What Does Our Team Do With the Blur?

Our team uses it. In the clinic, the blur is a marker: change the orientation of the head, change the position of the neck, have you move your arms, breathe differently, vibrate the ear or the toe, and watch what sharpens and what fogs. Each change that moves the blur points at the system that's driving it, and in our team's words, "we can actually use that blurring as a marker to help us understand how to fix it."

You can run a rough version at home. The clinic's advice is to "pick something on a wall that's got a little bit of resolution, you kind of use it like a cheating Snellen chart." Cover 1 eye, then the other, and check back and forth. You may notice 1 eye is much blurrier than the other. Note whether that difference is steady, or whether it comes and goes or changes with movement or head position.

Then, in our team's words, don't overshoot it. "If you got like an astigmatism or something, you get it checked out." A steady difference between the eyes is an optometrist's question. A difference that comes and goes, or changes with movement or head position, is what our team wants to look at for brain injury.

The second home check is a gaze hold. Look about 20 degrees off center and hold there. Our team watches for 2 things: eyes that drift back toward the middle and jump back out, which is the eyes getting weak or tired, and eyes that make small jerks while trying to hold still, called square-wave jerks. They come from different problems, which is why the clinic tells them apart. The warning from the video stands: "if you're cranking your eyes all the way over, you're going to freak yourself out, stop." Stay in a comfortable range. The circuits behind each movement are on what part of the brain controls eye movements.

Neither check is a diagnosis, and neither is a validated test. They're the clinic's advice on what to notice before you come in, and what the full exam measures is on concussion testing: what to expect.

When Should You See an Eye Doctor Now?

Go to the emergency room now for sudden or new double vision, loss of vision in 1 or both eyes, or a pupil that is bigger than the other or doesn't react to light. Pupils different sizes after a head injury covers those rules in full.

See an optometrist first for blur that is steady, was there before the injury, or fits a prescription change. That's the optics of the eye, and it has its own fix.

Get a full oculomotor exam if you're an adolescent with symptoms past 4 weeks. The authors of the adolescent study called it prudent, because office screening underperforms (Scheiman, 2021). Adults 2 to 6 months out carry a roughly 1-in-5 rate of symptomatic convergence insufficiency, and the 2 vision questions on the standard post-concussion questionnaire couldn't detect it (Nisted, 2024), so a normal questionnaire doesn't settle it either.

Blurry Vision After Concussion: FAQ