Some people who watched the World Cup this summer ended up with headaches and strained eyes.

And it had nothing to do with how their team did — or how much booze they drank during the matches. Some of those who watched the games on ESPN’s 3-D telecasts say they suffered headaches and eyestrain. But those who complained about the ailments said both problems decreased over time. The network announced its 3-D research from its telecasts in June and July. It involved over 1,000 testing sessions. The research also showed that those who watched in 3-D said they enjoyed watching the games better with the extra dimension of depth than traditional 2-D.