Lenticular glasses refer to eyeglasses that incorporate a double convex lens. "High plus" lenses were once widely used to treat patients after cataract surgery, while "high minus" lenses were used to treat patients with prescriptions of minus 10 dioptres. Lentincular glasses are now fairly rare due to the existence of other treatments.
"Lenticular" refers to an object with the shape of a lentil seed and comes from the Latin term for lentil, "lenticula." The first known use of this Middle English term appeared around the 15th century. As it applies to lenses, "lenticular" lenses have the a biconvex or double convex shape. A single convex lens extends outward in its centre on one side of the lens. A double convex lens extends outward in its centre on both sides of the lens.
Cataracts and "High Plus" Lenticular Lenses
Glass with "high plus" lenticular lenses once existed as a treatment for individuals who had cataracts surgically removed. Cataracts cause the lens of the eye to cloud over, typically decreasing an individual's ability to see significantly. As cataracts worsen, a surgeon must remove the clouded lens from the eye. Surgeons now implant lenses in the eye after the removal, but prior to this practice, patients received lenticular lens glasses to offset the problems that resulted from no longer having a lens behind the pupil of the eye. These lenticular glasses usually had a thick trifocal lens of 10 to 15 dioptres.
"High Minus" Lenticular Lenses
Glasses with "high minus" lenticular lenses are still manufactured, but rarely. The eyes of an individual with these glasses appear twice as small as they actually are due to the shape of the lens. While "high plus" lenticular lenses have a traditional lenticular shape, with a thick centre and thin edges, a "high minus" lens has the opposite shape. These lenses have thick edges and a very thin centre, and treat those with prescriptions of around minus 10 dioptres or higher. The "high index" lens, a lens made from a material thinner than standard glass, has replaced the "high minus" lens in most instances.
A vision disorder may use the term "lenticular" without referring to a disorder that requires lenticular glasses as a treatment. For example, lenticular astigmatism occurs when the lens of the eye, located behind the cornea, has an irregular shape and causes an inability to focus images on the retina, resulting in blurry vision. The "lenticular" here only refers to the lens of the eye, though, not to the glasses used for treatment. Many eye problems stem from a form of astigmatism, and the glasses worn in treatment have standard convex or concave lenses used to treat farsightedness or nearsightedness, respectively.
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