The main symptom is blurred vision even with glasses. Patients usually seek corrective lenses at first for driving or reading. Keratoconus at this stage is difficult to differentiate from other more common vision defects. The glasses prescription increases with time and usually shows high levels of myopia (short sightedness) and astigmatism. (distortion of vision) Some patients have glare driving at night or from sunshine.
If the distortion of the cornea worsens, so will vision. This happens in some patients but in many the condition stabilises. It is not possible to predict whether keratoconus will be progressive or at what rate it will worsen but in general the younger the age and the more severe the disorder when it begins, the more rapidly it is likely to deteriorate.
In advanced cases ‘hydrops’ can occur: this is the sudden onset of discomfort, redness and reduced vision caused by a split in the inside of the cornea. It usually clears after a few weeks but may leave permanent scarring. A ‘proud nebula’ is a small white scar at the tip of the keratoconic protrusion: it may worsen vision and glare and decrease contact lens comfort.