Hyperopia is also known as farsightedness. It is a general vision difficulty, affecting almost most of the people. In Hyperopia the eyeball is short from front to back as compared to the normal eyeball, in other words a person can see distant objects very well, but have difficulty seeing objects that are up close.
Exactly why eyeball shape varies is not known, but the tendency for farsightedness is inherited. Other factors may be involved too, but to a lesser degree than heredity.

Hyperopia Symptoms and Signs –

Sometimes Farsighted people have headaches or eyestrain and can strain to see or feel tired when performing work at close range. If you get these symptoms whereas wearing your glasses or contact lenses, you may need an eye exam and a new recommendation.

What Causes Hyperopia?

This vision difficulty occurs when light rays entering the eye focus behind the retina, rather than directly on it. The eyeball of a farsighted person is shorter than usual.
Many children are born with hyperopia, and some of them “outgrow” it as the eyeball lengthens with normal growth.

Sometimes people confuse hyperopia with presbyopia, which also is a difficulty in seeing up close, but have a different cause. If you can see objects at a distance clearly but have trouble focusing well on objects close up, you may be farsighted.

Your eye care practitioner may refer to farsightedness as long sightedness, or by its medical names, hypermetropia or hyperopia. Hyperopia causes the eyes to exert extra effort to see close up. After viewing nearby objects for an extended period, you may experience blurred vision, headaches and eyestrain. Children who are farsighted may find reading difficult.

Hypermetropia is not an infection, nor does it mean that you have “bad eyes.” It just means that you have a variation in the shape of your eyeball. The degree of variation will decide whether or not you will need corrective lenses.

Hyperopia Treatment –

Farsightedness can be cured with glasses or contact lenses to change the way light rays bend into the eyes. If your glasses or contact lens prescription begins with plus numbers, like +2.50, you are farsighted.

You may need to wear your glasses or contacts the entire the time or only when reading, working on a computer or doing other close-up work.

Refractive surgery, such as LASIK or CK, is another option for correcting hyperopia. It might decrease or remove your need to wear glasses or contact lenses

Presbyopia meaning "old person" describes the state where the eye exhibits an increasingly diminished capability to focus on near objects with age.

Symptoms of Presbyopia –

Most people notice are, complexity reading fine print, above all in low light conditions, eyestrain when reading for long periods, blur at near or temporarily blurred vision when transitioning between viewing distances. Many advanced presbyopes complain that their arms have become "too short" to hold reading material at a comfortable distance.

Alike to grey hair and wrinkles, presbyopia is an indication caused by the natural course of aging. It is usually first noticed between the ages of 40-50. The ability to focus on near objects declines all through life.
  
A delayed onset of seeking correction for presbyopia has been found among those with certain professions and those with miotic pupils. In particular, farmers and housewives search for improvement afterward, while service workers and construction workers try to find eyesight correction earlier.

Presbyopia is the diminished ability of the eye to focus on near objects. It usually develops after the age of 40 and is a normal part of the aging process. Reading glasses are the normal treatment for presbyopia although surgery is becoming an increasingly more common option.

Treatment of Presbyopia –

Presbyopia is not usually curable - although tentative steps toward a possible cure suggest that this may be possible - but the loss of focusing ability can be compensated for by corrective lenses including eyeglasses or contact lenses. In subjects with other refractory problems, convex lenses are used. In few cases, the accumulation of eyeglasses to an existing lens prescription is adequate. As the ability to change focus worsens, the prescription needs to be altered so.

Approximately the age of 65, the eyes have typically lost most of their elasticity. On the other hand, it will still be likely to read with the help of the suitable prescription. Some could find it essential to hold reading materials beyond away, or require larger print and more light to read by. People who do not need glasses for distance vision may only need half glasses or reading glasses.

Adjustable focus eyeglasses correct presbyopia by providing on-demand wide field dynamic focus. Spectacles of this type are currently available only under the trade name ‘Trufocals.’ Alternative eyeglasses intended for presbyopes are static. Modifiable focus spectacles, though, are neither static nor zonal; in its place they suggest on-demand adjustable {sometimes called ‘variable’} focus over the entire lens area.

In order to reduce the need for eyeglasses or reading glasses, some people choose contact lenses to correct one eye for near and one eye for far with a method called "monovision". Monovision sometimes interferes with depth perception. There are also newer eyeglasses or multifocal contact lenses that attempt to correct both near and far vision with the same lens.

Controversially, eye exercises have been quoted as a way to delay the onset of Presbyopia.

Amblyopia, or Lazy eye, is a general condition where one eye is weaker than the other. Amblyopia causes the stronger eye to compensate for the weaker eye which often leads the brain to disregard the image the lazy eye sees. If amblyopia is corrected when the child is under the age of 10, the weaker eye can become stronger and reduce degeneration. Even though the best result is achieved if treatment is started before age 5.

The problem is caused by either no transmission or poor transmission of the visual image to the brain for a sustained period of dysfunction or during early childhood.

Amblyopia is a birth defect that causes an opacification of the lens. Even though it may not be identified until later in life, if it isn't detected in the infancy stage, then permanent visual loss is possible. The most common causes for this condition are intrauterine infections, metabolic disorders and genetically transmitted.

Treatments for Amblyopia

Treatment of strabismus or anisometropic amblyopia consists of correcting the optical arrears and forcing use of the amblyopic eye, either by patching the good eye, or by instilling topical atropine in the eye with better vision.

One should also be wary of over-patching or over-penalizing the good eye when treating for amblyopia, as this can create so-called "reverse amblyopia" in the other eye.
Deprivation amblyopia is treated by removing the opacity as soon as possible followed by patching or penalizing the good eye to encourage use of the amblyopic eye.

Eye patching therapy can help improve eyesight if you or your child has been diagnosed with amblyopia or lazy eye by an eye doctor. The key is consistency and daily patching therapy. Patching should be done for 3 to 4 hours every day.

Strabismic amblyopia is treated by clarifying the visual image with glasses, and/or encouraging use of the amblyopic eye with a eye patch over the dominant eye or pharmacologic penalization of it (regularly by applying atropine drops to temporarily paralyze the muscles and weaken vision in the good eye—this helps to prevent the bullying and teasing associated with wearing a patch). The ocular alignment itself may be treated with surgical or non-surgical methods, depending on the type and severity of the strabismus.

 Surgery attempts to support the eyes by shortening, lengthening, or changing the position of one or more of the extra ocular eye muscles and is regularly the only way to achieve cosmetic improvement. Glasses affect the position by changing the person's reaction to focusing. Prisms change the light way and therefore images strike the eye, simulating a change in the eye position.

Early treatment of strabismus and/or amblyopia in infancy can decrease the possibility of developing amblyopia and depth perception problems. Eyes that remain misaligned can still develop visual problems. Although not a cure for strabismus, prism lenses can also be used to give some comfort for sufferers and to prevent double vision from occurring.

Pure refractive amblyopia is treated by correcting the refractive error early with prescription lenses. Vision therapy and/or eye patching can also be used to develop and improve visual abilities, binocular vision, depth perception, etc.

Achromatopsia (ACHM) is the incapability to make out or recognize color. Even though the term might refer to acquired disorders such as color agnosia and cerebral achromatopsia, it naturally refers to an autosomal recessive congenital color vision disorder, also called rod monochromacy and total congenital color blindness. Individuals with the congenital form of this disorder show complete absence of cone cell activity through electroretinography.

Signs and symptoms of Achromatopsia

1. Photophobia
2. Reddened eye, especially adjacent to the iris
3. Ocular and per orbital pain
4. Consensual photophobia (pain in affected eye when light is shone in unaffected eye)
5. Blurred or cloudy vision
6. White blood cells (leukocytes) (resulting in a grey or near-white haze) and protein (resulting in tiny white dots) in the anterior chamber, often called "cells and flare."
7. Synechia (adhesion of iris to lens or cornea)

Causes of Achromatopsia
The two main causes of achromatopsia are –

1. Congenital Achromatopsia -

The well-known causes of the congenital forms of achromatopsia are all due to malfunction of the retinal phototrzansduction pathway. In particular, this type of ACHM seems to consequence from the inability of cone cells to properly respond to light input by hyperpolarizing. Known genetic causes of this are mutations in the cone cell cyclic nucleotide-gated ion channels CNGA3 (ACHM2) and CNGB3 (ACHM3) as well as the cone cell transduction, GNAT2 (ACHM4).

2. Acquired Achromatopsia -

Cerebral achromatopsia is a type of acquired color blindness that is caused by spoil to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina.

Complications of Achromatopsia

Complications of iritic may include the following: Cataract, glaucoma, corneal calcification, posterior uveitis, blindness, band keratopathy, and cystoids macular oedema.

Treatment
Usually there is no treatment to cure color deficiencies. Though, definite types of tinted filters and contact lenses may help an individual to discriminate different colors better. Optometrists can supply a singular red-tint contact lens to wear in the dominant eye. This may enable the wearer to pass color blindness tests for certain occupations. The National Eye Institute is doing research into treating/curing color blindness, and it is now required to donate 5% of its resources to this cause under instruction of the National Institutes of Health.