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A Vision Screening is No Eye Exam

By

L. E. Leguire Ph.D., MBA

Program Director

Ohio Amblyope Registry

A vision screening, usually performed by a school nurse, doctor’s assistant or layperson, is often undertaken in a school setting or pediatrician’s office.  A vision screening usually involves having the child perform one or more eye tests.  The vision screening eye tests may include observation of the child’s eyes (e.g., Are they red? Is there discharge?), a visual acuity test to determine the smallest letters on an eye chart that can be correctly identified (e.g., 20/20) and sometimes may include an eye muscle balance test, such as the cover-uncover test, to assess eye alignment.

An eye exam is performed by an eye doctor, an Ophthalmologist or Optometrist, and involves inspection of the eyes, a visual acuity test, eye muscle balance test, as well as examination of the inside of the eyes following pupil dilation.  The eye exam also may include a measurement of the pressure inside the eye for assessment of glaucoma, a visual field test and a refractive error measurement to determine the need for glasses.  Eye exams may vary somewhat, in terms of eye tests performed, depending on the eye doctor and your medical history.

In children, a vision screening is usually performed to detect a vision loss and is not designed to determine the cause or reason for the vision loss (i.e., diagnosis).  For example, a vision screening will measure visual acuity in a child and if visual acuity is reduced or abnormal the child is referred to an eye doctor for a comprehensive dilated eye exam and determination of the reason for the reduced visual acuity, like amblyopia.  A diagnosis is not part of a vision screening - it only identifies if a vision problem is present.  In addition, a vision screening does not provide for therapy.  Typically, a diagnosis and therapy are provided by an eye doctor.

There are other differences between a vision screening and an eye exam.  In terms of detecting whether a vision problem exists, a comprehensive eye exam by an eye doctor is more likely to detect a vision problem than a vision screening.  For example, a vision screening may be 90% accurate in terms of finding a vision problem in a child but that also means that 10% of vision problems will not be identified and will be missed by a vision screening alone.  In addition, a comprehensive dilated eye exam by an eye doctor will detect certain eye problems before they create a vision loss, and thus would be missed by the vision screening.

Finally, it is important to note that children are, well, clever.  They will do everything possible to pass a vision screening particularly, as it seems, in a school setting.  This might include memorizing the letters on the eye chart or peaking around the object, like an index card, used to cover one eye while assessing vision in the other eye.  In general, vision screening personnel may not have actual training in performing a vision screening or may not be a stickler for details often required to ensure that a vision screening is performed with the greatest care and accuracy.  In an eye doctor’s office, trained and experienced personnel ensure that the eye tests are performed accurately and they are more likely to spot children attempting to “cheat” on the eye tests.

Vision screenings play an important role in public health policy and provide a first line of defense against vision problems that cause other problems like poor school performance.  Vision screenings can be used to assess for vision problems in a large number of children in a relatively short period of time.  In addition, when resources are limited, vision screenings are better than no vision assessment at all.  It is important, however, to recognize that a vision screening is not an eye exam and doesn’t take the place of a comprehensive eye exam by an eye doctor.  Just because your child passes a vision screening doesn’t mean that the child doesn’t need a comprehensive eye exam by an eye doctor.  If your child has never seen an eye doctor or hasn’t seen an eye doctor in more than two years, please consider taking you child in for a comprehensive eye exam.  Treatment and cure of childhood eye problems is usually easier when they are caught early.  And, by all means, if your child fails a vision screening it is very important to take your child to an eye doctor for a comprehensive eye exam - the sooner the better.

This web site is funded by The Ohio Department of Health, Bureau of Child and Family Health Services, Save Our Sight Program.