Contact lens Many people wear contact lenses to help image light properly on to the retina. another solution is for a person to wear glasses This places a lens in front of the eye not on the cornea as is the case with contact lenses a recent solution is to use a laser to reshape the cornea. this solution is possible only in some cases
Many people wear contact lenses to help image light properly on to the retina. Another solution is for a person to wear glasses. This places a lens in front of the eye not on the cornea as is the case with contact lenses. A recent solution is to use a laser to reshape the cornea. this solution is possible only in some cases
Astigmatism There are two kinds of astigmatism: 1 12 lenticular and 2. corneal 11 Astigmatism occurs when the sur face of the cornea or of the lens is not perfectly smooth. If, for example, there is a small 10 flat spot on your cornea the image in a certain direction on your retina will not be in perfect focus 3 If the figure on the right was constructed with all the radial lines of equal sharpness and contrast a person without astigmatism would see all these radial lines as perfectly 4 sharp and with the same contrast. The diagram on the right has been fudged to illustrate how it might appear to a person with astigmatism This condition can be corrected with a corneal contact lens or cylinder lens in a pair of spectacles
There are two kinds of astigmatism: 1. lenticular and 2. corneal. Astigmatism occurs when the surface of the cornea or of the lens is not perfectly smooth. If, for example, there is a small flat spot on your cornea the image in a certain direction on your retina will not be in perfect focus. If the figure on the right was constructed with all the radial lines of equal sharpness and contrast a person without astigmatism would see all these radial lines as perfectly sharp and with the same contrast. The diagram on the right has been fudged to illustrate how it might appear to a person with astigmatism. This condition can be corrected with a corneal contact lens or cylinder lens in a pair of spectacles. Astigmatism
Contact Lenses A scleral lens sits on the sclera of the eye. And because the lens is filled with fuid. some of which gets squeezed out when the A corneal lens, which is the type most lens is applied to the eye it is held contact wearer use. floats on a tear in place by a partial vacuun layer of the cornea
Contact Lenses
Corneal Contact Lens a very thin plastic lens, often flexible (soft lenses) floats on a layer of tears on the corneal surface of the eye These lenses can be of the permanent variety or disposable. The permanent variety need to be properly cleaned and cared for The disposable are often worn continuously and the thrown away when removed. Note how the bottom edge of the lens is against the lower eye lid If the wearer looks down, the lens is pushed up a little. This"trick"can be used to provide bifocal contact lenses. These lenses have different powers in the center than in the periphery. When the wearer looks down to read the lens is moved to a new position to facilitate seeing sharply at normal reading distances. If there is an irregularity on the cornea(astigmatism) it is automatically corrected by the combination of the tear layer and the contact lens
A very thin plastic lens, often flexible (soft lenses) floats on a layer of tears on the corneal surface of the eye. These lenses can be of the permanent variety or disposable. The permanent variety need to be properly cleaned and cared for. The disposable are often worn continuously and the thrown Corneal Contact Lens away when removed. Note how the bottom edge of the lens is against the lower eye lid. If the wearer looks down, the lens is pushed up a little. This "trick" can be used to provide bifocal contact lenses. These lenses have different powers in the center than in the periphery. When the wearer looks down to read the lens is moved to a new position to facilitate seeing sharply at normal reading distances. If there is an irregularity on the cornea (astigmatism) it is automatically corrected by the combination of the tear layer and the contact lens
Cylinder lens a cylinder lens is different than a spherical lens which is what one normally sees in spectacles. Although a cylindrical component my be built in to that which appears spherical as can be seen in the left diagram a cylinder lens has power only in one axis. In the left it is the horizontal axis This lens does not refract light in the vertical direction
A cylinder lens is different than a spherical lens which is what one normally sees in spectacles. Although a cylindrical component my be built in to that which appears spherical. As can be seen in the left diagram a cylinder lens has power only in one axis. In the left it is the horizontal axis. This lens does not refract light in the vertical direction. Cylinder lens