Which eye disease might Odysseus have had?

When Odysseus finally returned to his beloved Ithaca, he was worried that he would be recognized too soon. To avoid that problem, the goddess Athena promised to change his appearance to make him 'unknown to all mortals'. She 'shrivelled the fair skin on his supple limbs and destroyed the flaxen hair on his head'.

[The goddess Athena]

 I wonder if Odysseus really needed Athena to change his appearance. Remember, Odysseus was away for twenty years, had experienced the siege of Troy and survived several harrowing adventures. He would have aged considerably during that time. Furthermore, the Mediterranean climate with its incessant sunshine, would shrivel anybody's fair skin and we can imagine that the ageing Odysseus would have lost some (or most) of his hair during his long absence. He might even have been bald.

But Athena also promised to 'dim thy two eyes that were before so beautiful, that thou mayest appear mean in the sight of all the wooers, and of thy wife, and of thy son'.

The original text uses the term 'knyzosis' for the condition, which is related to the Ancient Greek verb knúō (κνύω) which means 'to scratch'. Knyzosis thus gave Odysseus' eyes an unpleasant appearance, although without decreasing their vision, and the condition was accompanied by an itchy feeling.

Is it possible to discover the actual eye disease that Odysseus might have had?

It cannot be conjunctivitis which simply results in a temporary reddish or pink eye. Yes, pain, burning, scratchiness, or itchiness may occur, but it doesn't really change your appearance.

A better candidate is blepharitis, characterized by inflammation of the eyelids. This condition may also cause burning, itching, or a grainy sensation when introducing foreign objects or substances to the eye. Blepharitis is not sight-threatening.

When your eyelids are inflamed, they get swollen and, because it also results in scaling, reddening, and crusting of the eyelid, it would have given Odysseus 'an unpleasant appearance'.

All of these changes (shrivelled skin, destroyed hair and eyelid inflammation) would surely make Odysseus unrecognizable.