Video narration
Your young patient is back for another refraction: the cylinder has shifted again, and retinoscopy shows a scissoring reflex. That is a clue to abnormal corneal shape, not a diagnosis by itself. The prescription is not the disease. Progressive corneal change is. In keratoconus, the cornea thins and steepens, producing irregular astigmatism and increasingly distorted vision. Corneal tomography maps that shape, helping you identify and monitor the ectasia; refraction tells you how the altered optics affect vision, not whether the disease is progressing. One refraction is a snapshot; compare corneal shape over time to establish progression. That distinction changes what you do next. Glasses or contact lenses correct the optical effect, but they do not stabilize the cornea. Look for progression. Corneal collagen cross-linking-a treatment that stiffens corneal tissue-can stabilize progressive keratoconus, though it does not restore the shape already lost.