Do you have any medical records about the retinal condition? Also how is his general health, that will also having a bearing on how he can be managed.

As long as visual potential is there, any type of cataract can be operated. So do not worry for the cataract. You need to consult good retina specialist followed by Cataract surgeon.

Please share the prescription of.

Needs a detailed examination by a vitreo retina specialist!

Sir as your father has no vision in one eye I would suggest you even if the other eye has low vision potential you should definitely opt for cataract surgery. It may give some functional vision to him. Having said that first you need to take him for a complete eye check up from a Cataract surgeon and a Retina specialist. That will have include a thorough dilated examination of the eye with B-scan of the eye and all the necessary preoperative investigations to determine the vision potential of the eye. As you already mentioned that the cataract is in critical situation by which I understand that it's an advanced grade 4 or brown / black cataract. There are again some issues like of Lens induced glaucoma occuring in advanced cataracts. So if your Ophthalmologist comes to the conclusion that there is even a small vision potential then you should take a chance of getting his operated for cataract.