Luke has a difficult task in determining the aetiology of the blindness in this passage, the possible causes being legion. However, the Apostle John gives us a number of clues.

We know that the man was blind at birth or soon afterwards as testified by the people and his parents. The blindness appears to have been total, obliging him to beg. There are no associated physical defects recorded and in particular no evidence of mental retardation as witnessed by his gracious but firm handling of the Pharisees. His parents appear healthy and Jesus tells us that his blindness was not due to any particular sin of his or theirs.

Common causes of neonatal blindness include bacterial infection, particularly gonococcal ophthalmia neonatorum acquired from the mother during birth. This is unlikely however as his parents were not recorded as being particular sinners.

Birth anoxia leading to cortical blindness or severe CNS infections such as meningitis are improbable as he appears normal otherwise physically and mentally. This would also rule out many uncommon syndromes.

Bilateral congenital glaucoma, which often presents at birth and is more common in males, is a possibility as are severe congenital cataracts. Leber's amaurosis, a retinal degeneration, is another possibility although in this condition the eyes look normal and so the obvious effect of the miracle would have been less.

One of the many varieties of congenital maldevelopment of the eyes, especially severe microphthalmos is very likely, the eyes appearing rudimentary - the size of a pea.

Luke favours this diagnosis as it would most vividly illustrate the spiritual truth that we all are densely blind spiritually - and that Jesus Christ alone has the power to give sight to those who are helpless in themselves.

If there is little or no stimulation of the occipital cortex during the first seven years of life then the ocular dominance columns fail to develop and the child can never regain sight even if the initial problem is cured. This is therefore an astounding miracle. Not only were the eyes healed but the patient's ocular dominance columns were rewired and given seven years of experience within a few minutes.