Refractive Errors

The cornea and lens of your eye helps you focus. Refractive errors are vision problems that happen when the shape of the eye keeps you from focusing well. The cause could be the length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens.

The most common refractive errors are:

  • Myopia, or nearsightedness – clear vision close up but blurry in the distance
  • Hyperopia, or farsightedness – clear vision in the distance but blurry close up
  • Presbyopia – inability to focus close up as a result of aging
  • Astigmatism – focus problems caused by the cornea
myopia

Myopia (or Nearsightedness)

Myopia, or nearsightedness, is a vision condition in which close objects are seen clearly and objects farther away appear blurred. This condition occurs when the eyeball is too long or the cornea has too much curvature thus resulting in distant objects looking blurred.

Myopia begins in school age children, around the age of 8-12 and always diagnosed before the age of 20. Nearsightedness may also develop in adults if they are diabetic or suffer visual stress. Myopia is the most common of the refractive errors, affecting 30% of the US population.

Symptoms
  • blurred distant objects such as a chalkboard in school or the television
Causes
  • Heredity: research shows that myopia is inherited if one or both parents are myopic.
  • Visual stress/disease:
    1. patients may experience myopic symptoms only at night. “Night myopia” may be casing difficulty for the eyes to focus properly due to the low amounts of light
    2. diabetic patients can develop myopia or an early cataract due to variations or changes in blood sugar levels.
    3. patients who work for long periods with near work may experience a false myopia. The blurred distance vision is caused by the over use of the eye focusing with symptoms usually only temporary.
Diagnosing

Myopia is typically diagnosed during school screenings at a young age. If you notice your child is having difficulty seeing the television or other distant objects, you can call our office to set up an examination including:

  • Visual acuity test – looking at letters on a distance chart to determine vision sharpness
  • Refraction test – Dr. Adelson places a series of lenses in front of the eye to measure which lens allows the eye to focus properly
Treatment
  • Glasses
  • Contact Lenses
  • LASIK – laser surgery to change the shape of the cornea by removing a small amount of eye tissue.
  • Other laser vision correction procedures including clear lens exchange – implanting a small lens with the desired correction inside the eye.

Hyperopia (or Farsightedness)

Hyperopia, or farsightedness is a vision condition where distant objects are seen clearly but close objects are blurred. This occurs when the cornea has too little curvature or the eyeball is too short. Farsightedness is typically diagnosed at a later age because the strength of the young eye can compensate for the condition for many years.

Symptoms
  • Headaches or eye strain
  • Blurred close vision
  • Aching or burning eyes
Causes

Heredity – this is typically a condition passed down by parents.

Diagnosing

Hyperopia is not tested during school screenings. You can call our office to set up a full eye examination including:

  • Visual acuity test – looking at letters on a distance chart to determine vision sharpness
  • Refraction test – Dr. Adelson places a series of lenses in front of the eye to measure which lens allows the eye to focus properly
Treatment
  • Glasses
  • Contact Lenses
  • LASIK – laser surgery to change the shape of the cornea by removing a small amount of eye tissue.
  • Other laser vision correction procedures including clear lens exchange – implanting a small lens with the desired correction inside the eye.

In milder cases of farsightedness, you may be able to compensate without treatment.

Presbyopia

Presbyopia is a vision condition where the lens loses its flexibility, thus resulting in difficulty focusing on close objects. Presbyopia usually occurs around the age of 40 and typically is experienced with reading or working on the computer. Presbyopia may seem to occur suddenly, but the loss of flexibility occurs gradually over many years. Presbyopia is a natural part of the aging process of the eye and cannot be prevented.

Symptoms
  • The need to hold books or menus at arm’s length in order to focus
  • Difficulty adjusting from near to distance vision
  • Eye fatigue along with headaches when performing near work
Causes

Age – This differs from myopia, hyperopia or astigmatism in which the shape of the eyeball is the cause. Presbyopia occurs when the lenses in the eyes loses the elasticity, thus the loss of ability to change focus at different distances. Long before symptoms are apparent, the lenses in the eyes begins to lose the ability to flatten and thicken. Symptoms occur only once the loss of elasticity impairs your vision.

Diagnosing

Dr. Adelson will perform a comprehensive eye examination that will include testing for presbyopia. Testing includes:

  • Refraction test – Dr. Adelson places a series of lenses in front of the eye to measure which lens allows the eye to focus properly
  • Visual acuity test – looking at letters on a distance chart to determine vision sharpness
Treatment
  • Reading glasses – typically worn only for near work such as reading.
  • Bifocal glasses – glasses with two points of focus – distance and near
  • Contact Lenses
  • LASIK – laser surgery to change the shape of the cornea by removing a small amount of eye tissue.
  • Other laser vision correction procedures including clear lens exchange – implanting a small lens with the desired correction inside the eye.
Monovision

Monovision is a technique where one eye is corrected for distance vision and the other eye is corrected for near vision. Monovision allows a person to see close objects with one eye and distance objects with the other eye. Monovision is an optical trick to work around the problems of presbyopia. The brain will learn to use the distance focused eye for distance viewing and the near focused eye for near vision. The adaptation takes 1-2 weeks and patients are unaware which eye is focused at near and which at distance.

The common method of achieving monovision is with contact lenses or with laser vision correction procedures by correcting the non-dominant eye for near vision and the dominant eye for distance vision. If you are considering a vision correction procedure, Dr. Adelson may test monovision contact lenses to see if you are happy before permanent correction.

Most of our patients over 40 that have tried monovision are extremely satisfied after becoming accustomed to it.

Astigmatism

Astigmatism is a common vision condition occurs when the cornea is shaped like a football where it has a slightly different curvature in one direction over the other. It often occurs in combination with myopia and hyperopia. Astigmatism is extremely common, most people have some degree of astigmatism. Astigmatism blurs your vision at all distances.

Symptoms
  • Blurred or distorted vision at all distances
  • Eyestrain
  • Headaches
Causes
  • Heredity
  • Lid swellings
  • Corneal scarsor corneal disease
  • Eye injury
  • Surgery
Diagnosing astigmatism

Dr. Adelson will perform a comprehensive eye examination that will include testing for presbyopia. Testing includes:

  • Refraction test – Dr. Adelson places a series of lenses in front of the eye to measure which lens allows the eye to focus properly
  • Visual acuity test – looking at letters on a distance chart to determine vision sharpness
Treatment
  • Reading glasses – typically worn only for near work such as reading.
  • Bifocal glasses – glasses with two points of focus – distance and near
  • Contact Lenses
  • LASIK – laser surgery to change the shape of the cornea by removing a small amount of eye tissue.
  • Other laser vision correction procedures including clear lens exchange – implanting a small lens with the desired correction inside the eye. See details on the toric lens specific for treating astigmatism.

Remember to schedule an annual eye examination to ensure you are in control of any vision changes and to ensure your correction is up to date to provide your best vision. Call us at 866-340-EYES to schedule an appointment or if you have specific questions regarding your correction options.