(July 28) -- Depending on your tastes, wearing neckties may be an assault to some folks' vision. According to a new study, wearing them too tightly may harm your own. Researchers say that a too-tight necktie may increase the risk of glaucoma by boosting blood pressure inside the eyes to dangerous levels. Specifically, a tight necktie constricts neck veins and raises the pressure in the eyes. Glaucoma, which afflicts at least 3 million Americans and is the leading cause of blindness in the U.S., usually occurs when pressure in the eyes increases to dangerous levels. In their study, published in the August issue of the British Journal of Ophthalmology, researchers noticed a small but significant increase in this intraocular pressure in men who wore tight neckties. The 40 men studied -- half of them glaucoma patients and the others with no obvious vision-threatening condition -- were observed under three scenarios. When their neckties were tightened for three minutes, intraocular pressure spiked in 60% of the glaucoma patients and 70% of the healthy men. There were no such increases when they loosened their ties for three minutes or while wearing open-collared shirts.