How Much Does The Average Baby Weight At 34 Weeks The Physics Of Contact Lenses

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The Physics Of Contact Lenses

Contact lenses are used to correct vision and are placed on the cornea. They perform the same corrective function as normal glasses. However, in comparison, it is very light weight and invisible for all purposes. Contact lenses help shape the image on the retina by refracting or refracting light entering the eye.

Earlier contact lenses were made of glass, and were scleral lenses. A scleral lens is a large contact lens that covers the entire sclera – the outer white layer – of the eye. These disposable lenses can only be worn for short periods of time. With the development of PPMA – polymethyl methacrylate – in the 1930s, the plastic was first used in contact lenses. They are, in fact, hybrid scleral lenses, made from a combination of two, glass and plastic, in 1936.

In the 1950s, smaller contact lenses were developed that covered only the cornea rather than the entire eye.

Types of visual impairment

One of the main uses of contact lenses is to correct visual defects. Common disabilities are Myopia, Hyperopia, Astigmatism and Presbyopia.

  • Myopia – is an eye defect in which the image of the object is formed in front of the retina. During this visual impairment, you can see near objects, but not distant objects, which appear blurry. This defect is known as eye disease. It is a common disorder, and more than 25 percent of adults in the United States suffer from it. The defect can be corrected by using a concave lens.
  • Hyperopia – also known as Hypermetropia, and the image of the object is formed behind the retina. Distant objects are clearly visible, and near objects seem blurry. Hyperopia is more commonly known as farsightedness, and more than 13 percent of children in the United States, ages 5 to 17, have it. The defect can be corrected by using a convex lens.
  • Astigmatism – This occurs when the eye has more than one focal point, on different meridians. Astigmatic people cannot see fine details, and need cylindrical lenses to correct their impairment. Nearly 34 percent of American children between the ages of 5 and 17 have this disorder.
  • Presbyopia – This is a deterioration, which comes with age, generally after the age of 40. Bifocal contact lenses are used to correct this defect.

A lens used to correct vision

In normal vision, the light from the object hits the cornea and is focused on the retina. Due to some mistakes, sometimes the light from the object is not focused on the retina, but either in front of it, or behind it. To correct this refractive error, contact lenses are used to focus on the retina.

The type of contact lens used depends on the type of vision loss, and the amount of refractive error involved. The intensity with which light moves to focus on the retina is measured in diopters (D).

Myopia occurs when light is focused in front of the retina, because the eyeball is longer than normal. To correct this damage, which is also called eye disease, concave lenses are used. This lens is thinner in the middle, and helps to move the focus forward, towards the retina.

To correct this visual impairment, the curvature of the concave lens is determined by measuring it in diopters. The greater the number of diopters, the greater the visual defect. In myopia, the diopter number is preceded by a minus sign (-), which indicates that the focus is short on the retina.

In hyperopia, light is focused outside the retina. Hyperopia is also known as farsightedness, because distant objects are clearly seen with this impairment. The eyeball is shorter than normal, and a convex lens is used to correct this lack of vision. The contact lenses used are thicker in the middle, and help restore focus to the retina.

In this case too, the curvature required for the convex contact lens is determined by measuring in diopters. The diopter number is preceded by a plus sign (+), indicating that the focus is outside the retina.

Lenses used to correct myopia and hyperopia are classified as spherical contact lenses.

When the shape of the cornea is irregular, the light from the object falling on the cornea is focused at more than one point. This distortion of the image is called astigmatism. Special lenses need to be adjusted, based on individual image manipulation. These lenses are known as toric lenses.

Although toric lenses are made of the same material as spherical lenses, they are specially designed to fit each individual’s difficulty. These lenses have different curvatures, being thicker in some places and thinner in others. These lenses are designed to correct astigmatism and myopia or hyperopia, if needed.

To correct presbyopia, special bifocal lenses are needed, because people who suffer from it require correction of nearsightedness and farsightedness. In such lenses, either the correction for close-up damage is placed in the center of the lens, with the distance correction on the outside, or vice versa.

Types of Contact Lenses

The first lens is a rigid lens that does not absorb water. This prevented oxygen from entering the cornea of ​​the eye, causing irritation and other discomfort.

Then came soft contact lenses made of hydrogel, which allow oxygen to pass through them to the cornea. These lenses became known as ‘breathable’ contact lenses. This allowed contact lenses to be worn well and for a long time. Currently there are:

Wear glasses every day, which are removed at night.

Long-wear lenses that can be worn for extended periods of time without removing.

Disposable lenses that can be thrown away after a day, a week, or a few weeks.

In addition, there are contact colors, which are designed for cosmetic purposes.

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