Patient Resources

What does 20/20 vision mean?

20/20 vision (the clarity or sharpness of vision) means being able to see what the “normal” human eye can see at a distance of 20 feet without the use of contact lenses or glasses to improve their vision. 20/20 does not necessarily mean perfect vision. 20/20 vision only indicates the sharpness or clarity of vision at a distance.  If you have 20/60 vision, it means that you must be as close as 20 feet to see what a person with normal vision can see at 60 feet.


I have 20/20 vision so do I still need to have regular eye exams?

Even if you have perfect 20/20 vision, it is important to regularly have your eyes checked to make sure your visual acuity and eye health is as good as it can be for as long as possible. There are several factors that contribute to vision or eye problems, so regular eye exams can detect potential problems early and correct them, if needed, before they become more serious.


How often should I have an eye exam?

As you age you should have your eyes examined more often  –  every two to four years, or more frequently if you are 60 years old or more. If you are under 40 years old, you may only need exams every four or five years unless you have ongoing conditions. But as always, follow your doctor’s recommendation. Many eye conditions are treatable or even preventable if detected early.


How often should my child have an eye exam?

The American Academy of Ophthalmology and the American Academy of Pediatrics recommend that the first vision screening be conducted for a newborn prior to being discharged from the hospital. Visual function will be monitored by your child’s pediatrician during well-child exams (usually at two, four and six months of age). If there are any signs of an eye condition, your child may be referred to a pediatric ophthalmologist or pediatric optometrist. Beginning at three years of age (and yearly after five years of age), amblyopia (poor vision in an otherwise normal appearing eye), refractive and alignment screenings should take place. If you notice any signs of decreased vision or misalignment of the eye, contact your eye doctor for a complete eye examination. Often your child’s teacher or school nurse will advise you that your child may be experiencing vision problems.


What does an eye doctor do during a routine eye exam?

We use a number of different tests and procedures to thoroughly examine your eyes. Some of these tests and procedures may include:

  • Reading an eye chart
  • Visual acuity test to measure the sharpness of your vision
  • Color blindness test to check your color vision
  • Retinoscopy to determine an approximate eyeglass prescription
  • Refraction to determine an exact eyeglass prescription
  • Slit lamp exam to evaluate the health of your eyes
  • Visual field test to check for potential blind spots in your peripheral vision

What is legal blindness?

Perfect vision is 20/20. A person is legally blind when their better eye’s best corrected visual acuity is less than 20/200. A person can also be legally blind if their side vision in their better eye is narrowed to 20 degrees or less. Although someone may be legally blind, some vision still may be useful and helpful for everyday life.


What is visual impairment?

If neither of your eyes can see better than 20/60 without improvement from glasses or contacts, you may be defined as visually impaired. In addition, poor night vision, limited side vision, double vision and loss of vision in one eye may also determine visual impairment.


What is low vision?

Low vision is a term describing a level of vision below normal (20/70 or worse) that cannot be corrected with conventional glasses. Low vision is not the same as blindness. People with low vision can use their sight. However, low vision may interfere with the performance of daily activities, such as reading or driving.


What is astigmatism?

Astigmatism is a condition that causes blurred vision due either to the irregular shape of the cornea, the clear front cover of the eye, or sometimes the curvature of the lens inside the eye. This uneven curvature can cause your vision to appear blurred up close and afar.  An irregular shaped cornea or lens prevents light from focusing properly on the retina, the light sensitive surface at the back of the eye. As a result, vision becomes blurred at any distance. Astigmatism is a very common vision condition. In fact most people have some degree of astigmatism. Blurred vision due to astigmatism can be corrected with corrective lenses or contact lenses.


What is nearsightedness?

Myopia, or nearsightedness, means close objects are seen clearly, but vision is blurred when viewing objects at a distance. Myopia occurs if the eyeball is too long or the cornea, the clear front cover of the eye, has too much curvature. As a result, the light entering the eye isn’t focused correctly and distant objects look blurred. This hereditary condition is very common and is usually discovered in childhood and can progress as one ages, and therefore requiring a stronger prescription.


What is farsightedness?

Hyperopia, or farsightedness is a condition which causes up close objects to appear blurry and distant objects are seen clearly. Hyperopia occurs if your eyeball is too short or the cornea has too little curvature, so light entering your eye is not focused correctly. If hyperopia is high enough, it can blur distance vision. This is most common among children and may improve as a person ages. Common signs of hyperopia include difficulty in concentrating and maintaining a clear focus on near objects, eye strain, headaches after close work, aching or burning eyes after long periods of concentration.


What is presbyopia?

Presbyopia is the natural aging of the lens in the eye and the muscles that control the shape of the lens. With age, the eye lens becomes more rigid and loses flexibility affecting the ability to focus on near. Presbyopia usually begins to occur around the age of 40, when glasses or bifocals are prescribed to correct this condition.


How does normal vision develop?

The development of equal vision in both eyes is necessary for normal vision. Newborn infants are able to see, but as during the first months of life their eyes start working together and vision improves. During early childhood years, the visual system changes quickly and vision continues to develop. If a child cannot use his or her eyes normally, vision does not develop properly and may even decrease. After the first nine years of life, the visual system is usually fully developed and usually cannot be changed.

For the first two months of life, an infant’s eyes are not well coordinated and may appear to wander or to be crossed. This is usually normal. However, if an eye appears to turn in or out constantly, have a pediatric ophthalmologist or pediatric optometrist examine your child.


How does the eye work?

When you take a picture, the lens in the front of the camera allows light through and focuses that light on the film that covers the back inside wall of the camera. When the light hits the film, a picture is taken. The eye works in much the same way. The front parts of the eye (the cornea, pupil and lens) are clear and allow light to pass through. The light also passes through the large space in the center of the eye called the vitreous cavity. The vitreous cavity is filled with a clear, jelly-like substance called the vitreous gel. The light is focused by the cornea and the lens onto a thin layer of tissue called the retina, which covers the back inside wall of the eye. The retina is like the film in a camera. When the focused light hits the retina, a picture is taken. Information about this picture is sent to the brain through the optic nerve. This is how we see.