Men should think twice about how tight they wear a necktie because it could increase their chances of developing glaucoma, a group of serious eye diseases.

Research reported in the British Journal of Ophthalmology on Tuesday showed that a tight necktie raises blood pressure in the eye, which is a leading risk factor in the illness that can lead to damage to the optic nerve and loss of vision.

?A tight necktie increases IOP (intraocular pressure) in both normal subjects and glaucoma patients and could affect the diagnosis and management of glaucoma,? said Dr. Robert Ritch of the New York Eye and Ear Infirmary.

Ritch and his colleagues tested the IOP of 20 healthy men and 20 who suffered from glaucoma while they were wearing an open-neck shirt, before putting on a tight necktie and three minutes after loosening it.

Their results showed that 60 percent of the men with glaucoma and 70 percent of the healthy volunteers had an increased eye pressure after wearing a tight necktie.

In addition to raising the risk of glaucoma, donning a tight necktie during an eye examination could lead to a false diagnosis of the illness.

The researchers suspect that a tight necktie constricts the jugular vein, which increases blood pressure and IOP.

The risk of glaucoma, which affects about 3 million people in the United States alone, increases with age.