Refractive Errors

Refractive Errors cause the light rays entering the eye to NOT focus on the back of the eye, resulting in blurred vision. They can be grouped as follows:

  • NEARSIGHTED or MYOPIA (one sees better at near)
  • FARSIGHTED or HYPEROPIA (one sees better at far)
  • ASTIGMATISM (both distance and close can be blurred)
  • PRESBYOPIA (poor near vision from age)

NEARSIGHTED or MYOPIA

In the normal eye, light is focused on the retina in the back of the eye. Myopia occurs either because the eyeball is too long, or the cornea (front of the eye) too curved, both cause light to focus in front of the back of the eye (retina), which causes blurred distance vision. Myopia is not a disease, nor does it mean that you have “bad eyes.” There are few perfectly shaped eyes, just as there are few perfectly shaped or aligned teeth. It simply means that you have a normal variation in the shape of your eyeball. Myopia can only be detected by an eye exam. This is especially important with kids, as they may not realize their vision is blurred, because they think everyone sees as they do. 

 
NEARSIGHTED EYE (Focus in front of the retina) and its effect on distance vision


Who is affected by myopia?

Myopia usually begins between the ages of 8 and 12 years and nearly always before the age of 20. Genetics is also a factor. Often the degree of myopia increases as the body grows rapidly, then levels off in the late teens. During the growing years frequent changes in the prescription eyewear may be needed to maintain clear vision. Allthough myopia can begin in the mid to late 20s and level off in the early 30s. The main symptoms are blurred distance vision, headaches, and squinting. A decline in athletic performance can also be an indicator of a visual problem. 

 
Myopia can only be diagnosed with an eye exam, and is treated with glasses, contact lenses or LASIK (for adults)
 

How is myopia treated

As with other refractive errors, glasses are prescribed to help focus light more effectively on the retina. Depending on the degree of myopia, glasses may be needed all of the time for clear vision. If the degree of impairment is slight, glasses may be needed only for activities that require distant vision, such as doing board work at school, driving or watching TV. Contact lenses and LASIK (adults only) are also an excellent options for myopic patients and should be discussed during your examination.

The myopic child

It is important to consider the psychological aspects of eye problems in children. The following tips may be helpful:

  • Avoid referring to the child's eyes as "bad eyes." Instead tell the child that they just bend the light differently and corrective lenses are needed to help focus light rays.
  • Letting the child verbalize concerns may also help adjustment to changing vision.
  • Make the occasion of selecting new frames for lenses a fun time.
  • Consider contact lenses (usually between the ages of 12-14) as a viable option for all myopic patients. Maturity is the main factor if a child should be fit with contacts.

MYOPIA CONTROL

The concept of myopia control (Orthokerotology) has been around for decades. Although there are no confirmed studies, there definitly is long term evidence that certain procedures do curtail myopia progression. The reason studies are so difficult is that you would need to clone and individual. you would need to have one undergo the procedure and the other not and see how they turn out. When we talk about studies, we are talking about apparent trends. Today, there are two modes used. One is with a rigid lens that actually flattens the front of the eye. The attractive atribute is taht the manufacturers recommend wearing this lens while sleeping, and then can go the entire day without glasses or contacts. However, in our experience, there are more complications by when sleeping in lenses. another mode which we favor is the wearing of bifocal soft contact lenses. The therory here is that by not having to focus at near, the eye doesn't elongate thus keeping the myopia in check.

FARSIGHTED or HYPEROPIA

Hyperopia, or farsightedness, is when light to focuses behind the back of the eye (retina). A  farsighted person, can focus well on distant objects more easily than near objects. This can be a undelying source of eyestrain. Just the opposite of nearsightedness, the eye in hyperopia is either too short or the cornea (front of the eye) is not curved enough. Genetics are also a factor. Unlike myopia, farsightness can easily go undected. Because kids have a larger degree of focusing power tha adults, it often goes undetected in a school screening, because they can subconsciously compensate. However, this can be a great source of eyestrain. That is why a comprehensive eye examination is so important. Hyperopia can be the main cause for poor school performance and can only be diagnosed with a complete eye examination.

 
FARSIGHTED EYE; often one can still have 20/20 vision for distance, but can be a source of eyestrain for reading.
 

SYMPTOMS

A person who is farsighted may have trouble concentrating or focusing on objects close up such as a book or a newspaper. After viewing nearby objects for a long period of time, blurred vision, nervousness, tension, and irritability can occur. A person may not enjoy reading, or if the person is a child, poor reading ability (skills) may be the result. With hyperopia the eyes need to exert extra effort inorder to see objects more clearly. This additional focusing effort can cause tension, fatigue, and eystrain. Younger people can overcome this because they have additional focusing ability. It can cause unrealized eyestrain, and can be the sole reason for declined reading skills and poor school performance. It may be the reason that it's battle to make them do their school work.  As one gets older, if the lens of the eye cannot bring objects into focus, blurred vision is the result.


Glasses may take the stress out of school.

TREATMENT

Hyeropia is treated with glasses, contact lenses, and LASIK (for adults). The best option for you depends on your individual lifestyle and needs. During your examination we will ask you a number of questions to help determine the best course of treatment. You may be asked to describe your usual lifestyle or daily activities. If your occupation involves reading fine print for most of the day, correction of the problem might involve different options than might be considered for a person who is not as dependent on near vision. Your lifestyle, occupation, types of recreational activities, and your general health status will give us clues about the what type of treatment will be best for you.

A comprehensive eye examination at the recommended intervals ensures that minor changes in vision can be diagnosed and treated so that your vision will remain as clear and comfortable as possible.

  • ASTIGMATISM (vision can be blurred at both far and near)
  • The front of the eye is shaped like a football, with two different curves, which splits light into two focus points.
  • A person's vision for far and near can both be blurred.
  • There is a genetic tendency to have astigmatism, and it is more prevalent in certain ethnic groups (Hispanic).
  • Moderate to severe astigmatism is usually presents at birth; therefore, an examination is needed between 1-3 years of age.
  • If undetected, a person is at high risk of developing a permanent lazy eye (amblyopia).
  • IT CAN BE EASILY MISSED DURING A SCHOOL VISION SCREENING.
  • It can change during adolescence.
  • Astigmatism is NOT considered an eye disease, just a normal variation in the shape of the eye. The eye is healthy; it just focuses light at two points instead of one.
  • It can be corrected with glasses, contact lenses, or refractive surgery (LASIK).
  • Can be combned with Nearsightedness or farsightedness

Graphic of an astigmatism and its corresponding vision, (shadows or ghost images). Some just complain of blurred vision.
 

SYMPTOMS

  • Difficulty focusing on objects either at distance or close or both.
  • Tired eyes, headache, or eyestrain after distance-vision tasks or reading or computer work
  • Eyes that are red or water
  • Poor reading ability and/or school skills
  • Poor reading comprehension
  • Reluctance to do homework or close-vision tasks
  • Squinting

TREATMENT

As with all the refractive errors, astimatism can be treated with glasses, contact lenses or LASIK (for adults). The degree of astigmatism will be determined during the examination. Some may need to use a correction for distance only, or just for reading. Some may need to wear a correction all the time.  If there is a family history, an eye examination is needed by age two to ensure that the eyes will not develop normally and not result in amblyopia or lazy eye.

PRESBYOPIA

Presbyopia is a condition of vision in which the normally flexible lens inside the eye, due to age, becomes stiff and can no longer change shape to bring clear reading vision. It is usually first noticed when one is subconsciously extending their arms to read. This occurs to everyone and begins around 40 years of age. As we age, body tissues normally lose their elasticity. A familiar sign of that process is wrinkled skin. Our eyes are not immune to that type of change. Likes wrinkles, changes in the eye do not occur overnight but take place gradually over a period of years. When you experience a change in vision, you may feel as though it happened suddenly. A condition such as presbyopia actually develops slowly; it just had not impaired your vision enough for you to notice.


Extending the arms to read may be t
he first indication of presbyopia.

Presbyopia is the inability of the lens to
change shape to bring things
in focus.
 

The lens, an important partner in the process of sight, is responsible for focusing light on the retina. In youth, the lens is flexible; with the help of tiny muscles in the eye, it quickly and seemlessly focuses for both near and distant objects by bending or flattening out when needed to bring a clear focus to the eye. With age and the accompanying loss of lens flexibility, it becomes more difficult for the lens to bend to a greater degree. In addition to a loss in ability to bend, the lens responds more slowly with age. Therefore, it not only becomes difficult for the eye to focus on near objects, which require a greater degree of flexibility. another symptom is the eye also does not adjust rapidly to changes in focus. For example, if you are sitting a reading the newspaper, when you change your gaze to the TV, it may be blurry. Although presbyopia mimicks the symptoms of hyperopia (farsightenes), it is completely different. Presbyopia is caused by a loss of elasticity in the LENS of the eye. It happens to EVERYONE at sometime or another.

SYMPTOMS OF PRESBYOPIA

  • Holding things farther away to read
  • Headaches when reading
  • Difficulty reading menus
  • Thinking newpapers are using smaller fonts
  • Harder to thread a needle, or do small detailed work

TREATMENT

Reading glasses or contact lenses. LASIK is usually not an option. There are other refactive procedures that can replace glasses or contacts. If you do not have other vision problems, such as nearsightedness or astigmatism, you may only need to wear glasses for reading or doing other tasks done at a close range. If you do have other refractive problems, bifocal or progressive addition lenses are often prescribed. Contact lenses are also a preferred option for many people, either bifocals or monovision. With monovision one eye is corrected for distance viewing, and the non-dominant eye is corrected for close work. This works well for many people. Some patients can't tolerate it at all. We can determine that during your examination. Technology in bifocal contact lenses has greatly improved in recent years. If they work properly, you will not even know that they are in your eye.

THE BEST OPTION FOR YOU DEPENDS ON YOUR INDIVIDUAL NEEDS…Our staff and eye doctors may ask you a number of questions to help determine the best avenue of treatment. You may be asked to describe your usual lifestyle or daily activities. If your occupation involves reading fine print for most of the day, different options would be considered than for a person who is not as dependent on near vision. So, your occupation, types of recreational activities, and your general health status will give us the clues about the lenses that would best fit your lifestyle.

 

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