Presbyopia

This is a condition of vision in which the individual has difficulties in focusing on near objects and in reading fine print. The condition is commonly seen after the middle forties due to the diminished power of accommodation from impaired elasticity of the crystalline lens. 

The signs of presbyopia include blurred vision at the reading distance and a need to hold reading material further away. Other symptoms include headache, fatigue, or difficulty concentrating when doing close work. Extra plus power is needed to correct presbyopia. 

 This can be in the form of reading glasses, or bifocals, or progressive lenses. Early myopic presbyopes can be slightly undercorrected at distance to give them some more time before they need a full reading correction. As the focusing ability of the eyes is reduced gradually over time, the near correction must be made stronger periodically. 

 The already hyperopic patient will have earlier trouble with near vision as he becomes presbyopic. If you have just the right amount of nearsightedness, you may be able to simply take off your regular glasses to read. It is like having built-in reading glasses. 

Mono-vision is recommended by many LASIK surgeons for their patients aged 35 years and above who are presbyopic, or who are likely to become so in the near future. The aim of mono-vision correction is to enable the patient to have a close to full range of vision with much reduced dependence on glasses for both distance and near vision. This is achieved by aiming at full or close to full correction in the dominant eye and mild under-correction in the other, non-dominant eye.

Astigmatism

Ideally, the shape of our eye should be round like a soccer ball. When this occurs, all the light rays from an object will meet at a single point on the retina. If a structural defect of the eye occurs, and the resulting shape of the eye is elliptical like an egg, then the light rays from an object will not meet in a single point on the retina. 

The rays appear to spread as a line in various directions and vision can be blurry, distorted, or shadowy at distance or near. Correction for astigmatism is given in the form of a cylinder A cylindrical lens bends light along only one axis as only one of its axes is curved. Astigmatism is corrected by introducing a cylindrical lens of opposite refractive properties. 

 The axis of the cylinder follows the longest axis of the eye. The power of the cylinder is perpendicular to the axis. Example: -1.00 x 180. Patients may have a combination of astigmatism and spherical refractive error. In that case, the physician may correct the problem by combining a spherical lens with a cylindrical lens placed along the appropriate axis. Example: -2.00 / -1.00 x 180 With LASIK refractive surgery, the refractive error of astigmatism can be eliminated and vision restored by changing the cornea shape which is irregular or not smooth, into a cornea which is regular or smooth.

Hyperopia>>>Farsightedness

Hyperopia or Farsightedness is a type of vision in which seeing is clearer at far distances than at near. When the eye is relaxed, the combined powers of its optical elements is not enough to bring things into focus. This is because the image of an object falls behind the retina, and is thus, out of focus. 

The cause of hyperopia is either the length of the eyeball is too short, or the power of the cornea is too weak. If a person has good focusing ability or just a little hyperopia, he may be able to maintain both clear distance and clear near vision. If, on the other hand, a person has poor focusing ability or a high amount of hyperopia, he cannot focus efficiently even for far vision. 

 This person's vision will be blurred for both distance and near, although greater for near. The hyperopic patient will have even more problems with near as he becomes presbyopic. Plus lenses are used to correct hyperopia. It brings the image of an object forward, focusing on the retina, resulting in clear vision. In Asia, there are less hyperopes than there are myopes. Hyperopic also can treatment with the lasik surgery, same like myopia.

Myopia >>> Nearsightedness

Myopia, or nearsightedness, is a type of vision in which seeing is clearer at close distances than at far. In myopia, the image of an object falls in front of the retina and is thus, out of focus. 

The cause of the myopia is either the length of the eyeball is too long, or the power of the cornea is too high. Minus lenses are used to correct myopia. 

This brings the image backward, focusing on the retina, resulting in clear vision. Laser refractive surgery can correct the myopia by altering and changing the curvature of cornea by making it flatter so that the rays of light can be refracted and fall exact with the retina

Human Eyes >> Normal eyes

we have knew that many people can not see the object clearly. They have problem with their eyes. but the other one have good vision. 

 Normal Eyes 

 Normal or perfect vision is the condition in which parallel rays of light are focused exactly on the retina without effort of accommodation. This is termed emmetropia. The optic system responsible for bending the rays of light is the cornea, aqueous, pupil, lens, and vitreous. All of these components which contribute to vision must be transparent, healthy, and functioning properly as a system, to achieve clear and quality vision. As the light strikes the photoreceptor cells of the retina, it transmits neuronal impulses along the optic nerve, via the visual pathway, to the brain for processing. 

 The process of when rays of light enter the eye from an object, pass through the optical system, and fall on the retina is called refraction. The total power from all the components involved in the refraction is measured in Dipoters. If the rays of light and image fall exactly on the retina, then there is no refractive error, and the power needed for correction is zero. 

 The eye is normal because the image is focused exactly on the retina without the effort of accommodation. what obout the someone who have refractive errors so they can not see clearly, 

Today you can undergo to LASIK