Ticks are particularly common in collared doves and wood pigeons. They will usually be on the head and look like a soft brown lump but their presence is often revealed by the black eye they can cause.
It is important that ticks are removed, – and removed properly – because they inject an anticoagulant into their host’s blood 
, which can cause haemorrhaging and can also affect the nervous system, causing neurological symptoms and often death.
If you find any you will need to ensure that you remove the whole tick including the head which will be buried in the bird’s flesh. If you do not have a tick remover you can use tweezers: position the claws of the tweezers as close as you can get to the bird’s body then gently twist anticlockwise. Dabbing the tick with Frontline first can weaken it and make it easier to remove.
These videos show how to remove a tick:
Treating the pigeon or dove with a course of Baytril (0.1 ml per 100 gms bodyweight of bird) can speed up the healing
Vets are not always able to diagnose tick damage. 
This little dove's vet thought that it might have a ruptured eye and that it would be blind for life.
However, it made a full recovery and was released. The following photographs provided courtesy of his rescuer, SharonSandland, show his progress towards eye recomplete recovery.
Both our blind pigeons were either born that way or lost their sight when they were babies, so they had to learn to identify what was edible and how to pick it up and learn to live with other pigeons. Information of how that was done can be found here:
I have come across a number of pigeons that are missing an eye. One that was born without one eye, some that have lost an eye to a predator, some that have had an infection.
As first aid I wash the eye with warm "sterile saline solution" as sold in Boots.
I will usually take a pigeon with eye problems to the vet, to determine whether antibiotics or surgery is needed.
HOMEOPATHY
Homeopathy can be very effective in the treatment of eye injuries and infections. In her book Homeopathic Treatment for Birds Beryl M Chapman recommends Aconite 6 - given for three or four days - four times a day - only if the eye is inflamed.
If an eye is infected with pus she recommends Euphrasia 3 for three days (this is also recommended for an inflamed eye that does not respond to Aconite). If there is a lot of pus she recommends Argentum Nit 6 instead of Euphrasia, dosage and length of treatment are the same.
RELEASE
The big question is "Can a one eyed bird be released back into the wild?" Technically, yes, because unlike raptors one eyed pigeons will have no difficulty finding and eating food so they will cope in the wild BUT their life expectancy is limited because they will be blindsided by predators, traffic and people that kick pigeons for fun.
When this little dove was brought to us we though that he might have lost his eye...we were wrong!
After a few days of supportive care and antibiotics the dried blood cleared up to show the original damage which didn't look very serious: there was a tiny slit in the lower eye lid, an injury or a tick?
Gradually the undamaged eye emerged .
He made a full recovery and flew off as soon as he had the opportunity !!
A pigeon that appears to be unable to see seed to pick it up or pecks at seed and misses is most likely to be suffering from Pigeon Paramyxovirus.
Pigeon pox can cause the development of lumps and pustules in unfeathered areas around the eyes.
All pigeons are susceptible to pigeon pox but it is common among juvenile wood pigeons which tend to get this disease in autumn. It usually presents itself as pustules on the feet, beak and eyes, 
but it will often affect the pigeon internally. This photo shows the first signs of pox on a juvenile wood pigeon's feet.
Suggested treatments to fight pigeon pox are to strengthen the immune system with echinacia, give vitamin supplements, specially Vitamin A, and administer one pilule of the 30th potency of the homeopathic remedy Arsenicum and one pilule of the 30th potency of the remedy Rhus Tox every two hours for 3 doses each. If you see an improvement, stop dosing.
In wood pigeons this illness tends to become wet or internal and therefore is often fatal...if internal wet lesions develop administer 1 pilule of the 60th potency of the homeopathic remedy Kali Mur and 1 pilule of the 60th potency of the homeopathic remedy Nat Sulph alternately once an hour for three doses, then reduce to once every three hours for three doses...if there is any improvement stop...if there is no improvement continue this treatment for a day.
The photo above shows the beginnings of internal pox in a juvenile wood pigeon.
Photos of Roger the Woodpigeon courtesy of Charlotte Biddle.