Long term smoking people is easier to get cataract as tobacco contains many harmful substance such as Nicotine. A survey shows that the rate of smoking people getting cataract is double than non smoking people. You can tell your father smoking makes him comfortable in one time, but might do harm to his eyes in life time if he keep on.
Long term smoking can contribute to risks of cataracts and macular degeneration. Besides, smoking is very bad to our liver. If you got some liver problems, your eyes, usually will turn yellow but they should be white. And the risk of developing age-related macular degeneration is greatly increased for people who smoke. Some people with servere age-related macular degeneration even lead blindness.
As we know, smoking will be bad on the health. Like your father who is smoking every day, his eyes will easily feel dry. What's worse, the old aged person will be weak at the immune system of the eyes. That is to say, he may get the eye diseases from the dryness easily.
Well, generally speaking, if you keep smoking, it actually does harm to your health, not only the eyes, but also the body organs. Anyway, in my opinion, you should let your father give up smoking. For long term effects, it can lead to lazy eyes, and hearing loss. As we know that by smoking, it can produce cyanide which is a retinal toxin. And according to some research, Smokers may develop toxic amblyopic problem. And also, it can degrade the night vision. So it can be kind of dangerous.