What Is Keratoconus and How Does It Affect Vision?

Keratoconus is a condition many people have never heard of until they’re diagnosed with it, but it’s a genuine, progressive change in the shape of the cornea that affects vision in ways standard glasses don’t always fully correct.

What actually happens

In a healthy eye, the cornea holds a smooth, even, dome-like curve. With keratoconus, the cornea gradually thins and bulges outward into a more irregular, cone-like shape. That distortion scatters light entering the eye unevenly, producing blurred or distorted vision, increased sensitivity to light, and sometimes ghosting or streaking around lights at night — symptoms that can look a lot like ordinary astigmatism in the early stages.

Why it’s often caught late

Keratoconus typically develops gradually, often starting in the teenage years or early twenties, and progresses over time rather than announcing itself all at once. Because early symptoms can resemble a simple need for a stronger prescription, it’s sometimes mistaken for routine vision changes rather than identified as a distinct corneal condition — which is part of why regular, thorough eye exams matter, since specific corneal mapping can catch it well before it becomes severe.

How it’s managed

In milder cases, glasses or standard soft contact lenses can still provide workable correction. As it progresses, rigid or specialised contact lenses are often needed to create a smooth, even surface over the irregular cornea, since a flexible soft lens simply conforms to the same irregular shape rather than correcting it. In more advanced cases, treatments like corneal cross-linking can help slow or stop further progression, and in the most significant cases a corneal transplant may eventually be considered. None of this is something to self-diagnose from symptoms alone — if vision has been getting subtly harder to correct or night glare feels unusually pronounced, it’s worth raising directly at your next eye exam.