The unnamed child who lived in the US had autism and struggled to eat many foods as he didn't like the texture.
The kid began experiencing eye problems earlier this year, with his vision "darkening" in the mornings and evenings, only improving briefly during the day.
His parents took him to get his eyes checked, but no major issues were discovered.
Within six weeks, he could no longer walk without leaning on his parents for support and frequently stumbled into doors and walls.
One night, he woke up screaming because he couldn't see.
The lad was rushed to hospital, where doctors discovered his poor diet had left him dangerously low on nutrients crucial for healthy eyesight.
Despite supplements and feeding therapy, experts wrote in the New England Medical Journal that the boy's vision loss may be permanent.