As the name suggests, the condition produces a “conical” corneal shape and this altered shape results in poor visual function. In a related condition termed pellucid marginal degeneration, the shape is even more seriously distorted. Occasionally, the two conditions can occur together.

These are genetically determined conditions and often manifest between the ages of 10 and 20 years. Although the condition is usually present in both eyes, it can sometimes affect them unequally. After the onset, the condition usually progresses during the next 10 to 15 years, although this can vary from person to person.

Persons with this condition often have allergic tendencies – hay fever, asthma, or skin allergies. Relatives may have a similar problem or high, unusual refractive errors. The initial symptom is blurred vision, often not correctable fully with spectacles, and or a frequent change of spectacle power.

In the initial stages, better vision can be obtained with the use of rigid gas permeable contact lenses- although often in the moderately advanced conditions, special lenses are required to achieve a comfortable fit. If the condition advances further, then customized scleral contact lenses may help improve vision. In pellucid marginal degeneration, crescentic corneal tissue excision can help restore corneal shape and vision.

Diagnosis of the condition requires the use of special instruments like corneal topographers, to measure the corneal shape and pachymetry to estimate corneal thinning. In moderate disease, the newer option of collagen cross-linking (C3R) to stiffen the cornea, can slow or arrest disease progression. Dr Srinivas K Rao is a pioneer in this technique with more than 400 cases done thus far. A recent advance with this technique is the use of an Accelerated approach to cross linking, which can shorten the treatment time from 1 hour to 30 minutes, thereby greatly increasing patient comfort.