Nearsighted, farsighted, astigmatism — the most familiar reason vision is blurry. Here is what each one means, in plain language, with the diagrams that make it click.
Time outside and myopia
A refractive error is simply a mismatch between the length and shape of the eye and the power of its focusing surfaces — the cornea and the lens. Light that should land exactly on the retina lands slightly in front of it or behind it instead, and the image blurs. The three diagrams below show the difference.
Emmetropia is the term used to describe a person’s vision when absolutely no refractive error or de-focus exists — an eye with no visual defects. Images formed on an emmetropic eye are perfectly focused, clear and precise.
When an eye is emmetropic, light rays coming into the eye from a distance come to perfect focus on the retina.
Nearsightedness is a common vision condition in which you can see objects near to you clearly, but objects farther away are blurry. It occurs when the shape of your eye causes light rays to bend (refract) incorrectly, focusing images in front of your retina instead of on your retina.
Nearsightedness may develop gradually or rapidly, and it often worsens during childhood and adolescence. It also tends to run in families — which is one reason a child’s vision is worth checking even when no one has complained about the board at school.
Farsightedness is a common vision condition in which you can see distant objects clearly, but objects nearby may be blurry.
The degree of your farsightedness influences your focusing ability. People with severe farsightedness may be able to clearly see only objects a great distance away, while those with mild farsightedness may be able to clearly see objects that are closer.
Astigmatism is a blurring of vision due to an irregular shape in the cornea or lens. In eyes without astigmatism, the cornea and lens have a more or less similar curvature in all directions. That lets light be focused to a single point on the retina.
People with astigmatism have more curvature in one direction, or meridian, than in another, so light is not able to focus on a single point on the retina. The result is a blurring of vision at all distances — which is why astigmatism can be missed by the assumption that blur is only a distance problem.
Refractive error — myopia, hyperopia and astigmatism — is the most common reason vision is blurry, and it is corrected with glasses or contact lenses. A careful refraction determines the most accurate, comfortable prescription for you, and it is part of every comprehensive examination we do.
We also look beyond the prescription at how the two eyes team and focus together, because the two are connected. Plenty of people see 20/20 on a distance chart and still report blur after a few minutes of reading, words that swim or double, headaches, or a strong urge to stop. Those are eye teaming and focusing problems, and a new pair of glasses on its own does not resolve them. Checking both in one visit is the point of a developmental evaluation.
Care starts with a comprehensive eye examination. Dr. Murray measures the refractive error precisely, checks the health of the eye, and — in the same visit — evaluates eye teaming, focusing and eye movements so the prescription is judged against how you actually use your eyes, not against a chart alone.
From there, the plan may be glasses, contact lenses, or a prescription paired with vision therapy when a teaming or focusing problem is found alongside the refractive error. Examinations are available at our Coconut Creek, Boynton Beach, Boca Raton and West Palm Beach offices. Not sure whether what you are noticing warrants a visit? The free symptom checklist takes a couple of minutes, and our vision problems guide covers what else can look like a learning or attention issue.
What an eye examination measures — eye health, the refraction that determines your prescription, and how the eyes work together.
The extra measurements a contact lens exam adds once the prescription is known: corneal curvature, pupil size and tear film.
Focusing problems that glasses alone do not explain — blur that comes and goes, or comes on after a few minutes of reading.
When the eyes struggle to turn in and stay together at near, print can blur or double even with a perfect prescription.
Blur and doubling have several possible causes. Here is how they are told apart and what each one points to.
The health side of the same visit: the front and back of the eye, checked at every comprehensive exam.
The same question this page answers, written for a curious child or a parent explaining it at the kitchen table.
Once there is a prescription: frames that fit, hold up, and actually stay on a child’s face.
A refusal to wear glasses is sometimes about comfort or fit — and sometimes about what the glasses are not correcting.
What each exam covers, and why a prescription check answers a different question from a developmental evaluation.
An evaluation measures the refractive error and how the eyes work together — at our Boynton Beach and Boca Raton offices.