It sounds to me like subconjunctival hemorrhage. If your husband is taking any type of blood thinning meds, asprin ect, he is more susceptible to this condition. The tenderness and pain could be caused by dryness of the eye, which can sometimes be helped by using over the counter eye drops. At any rate, eye conditions should be taken seriously. The people in this forum are very informative, but many of us including myself are not doctors and none of us can make a definite diagnosis. Have him see an opthamologist as soon as possible, just in case the condition is serious to prevent any damage to his vision.
I would definatly get this checked out asap b/c i have a small blood vessel in my eye which you can also get from wearing contacts to long that dont get much oxygen to your cornea and a blood vessel will form to deliver the oxygen there, if it grows into the cornea blindness can occur, eye pain is not normal could also be a sign of high BP
Has he ever been to an eye doctor for this? That's the best place to start. There could be lots of reasons for this, some serious, some not. Don't mess around with vision problems. Pain in the eyes ALWAYS merits a thorough exam to be sure.