Vision loss linked to caffeinated coffee in new study
http://www.examiner.com/article/vision-loss-linked-to-caffeinated-coffee-new-studyMedline Plus writes that caffeine is a bitter substance which is found in coffee, tea, soft drinks, chocolate, kola nuts, and certain medicines. Caffeine has many effects on the body's metabolism, which include stimulating the central nervous system. This can result in making you more alert and give you a boost of energy. For the majority of people, the amount of caffeine in two to four cups of coffee a day is not harmful.
However, consuming too much caffeine can make you restless, anxious, and irritable. Too much caffeine may also cause insomnia and cause headaches, abnormal heart rhythms, or other problems. And if you stop using caffeine, you could get withdrawal symptoms. It has been found that some people are more sensitive to the effects of caffeine than others and they should limit their use of caffeine.
In a paper published on October 3, 2012 The Association for Research in Vision and Ophthalmology, Inc. (ARVO) has reported: "New study links caffeinated coffee to vision loss." A new study has suggested caffeinated coffee drinkers should limit their intake in order to reduce their chances of developing vision loss or blindness. Heavy caffeinated coffee consumption has been found to be associated with an increased risk of developing exfoliation glaucoma, which is the leading cause of secondary glaucoma worldwide, according to a scientific paper which has been published in Investigative Ophthalmology & Visual Science.
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thanks for the article! 
No question that overdosing on coffee can have short-term ill effects: Insomnia, irritability, depression, cardiac arrhythmias, GI upsets ... but none of the long-term effects (such as the blindness discussed in this article) have every been replicable.
I have not read this study. I will though, as I do drink a lot of coffee.
However, as you can tell from my subject-line, I am not unbiased about this, and all of the previous "coffee causes harm" studies which have not panned out make me skeptical of this one.
For example, one of the best done ones came out in the late sixties which showed a strong and close association between coffee drinking and pancreatic cancer (I think it was in Lancet).
It was well enough done that it worried me for over a decade until attempted replications failed. It was finally determined that the positive correlation was a result of confounding variables (cigarettes and alcohol as I recall).
There are now several current studies which show a reduction in the onset and severity of certain dementias in inverse correlation with the amount of coffee consumed (the more coffee, the less dementia). These are new enough that they have not been adequately replicated.
The Middle Path: Nothing in Excess
