Preschool Vision Screening: Detecting Eye and Vision Problems in Preschoolers

Vision problems are fairly common in preschoolers: farsightedness (hyperopia), nearsightedness (myopia), a difference in refractive power between the two eyes (anisometropia), “lazy eye” (amblyopia), and other vision problems are correctable, so long as the problem is caught and treated in a timely manner. In fact, if amblyopia is not addressed during the early childhood years, the vision in the affected eye may become permanently harmed.

Surprisingly, many pediatricians do not include vision screening as part of a well-child checkup. The pediatric offices that do include a vision screening often use an eye chart, having the child occlude one eye at a time: many children want to “pass” the exam, and will peek around the paddle used to occlude the eye. The adult conducting the eye exam might not notice the subtle “peeking” or stepping forward to get a clearer view of the eye chart.

Quality vision screening is essential to detect and correct vision problems: there are automated, accurate screening devices which require little participation from the preschooler undergoing the vision screening process.

It is highly important to note that a vision screening program cannot take the place of a comprehensive eye examination. Vision screening procedures only "catch" 2/3 of children with vision problems: the remaining 33% of children screened will pass the vision screening when a vision problem is present. All children should have a comprehensive vision examination by a qualified optometrist or ophthalmologist prior to entering Kindergarten (or the age of 5).

There are several ways to determine the visual acuity of preschoolers. A brief description of the most common methods is listed below:

LEA Symbols Distance Visual Acuity Test: Symbols such as a house, square, circle, and apple are printed on cards. The child is asked to name the symbols at a distance of about 3 feet, using both eyes as a "pre-test." Then the child's left eye is patched, and the card is removed to a distance of 9 feet. The child must name the symbols while using only the right eye. If the child identifies 3/4 of the symbols correctly, the vision screening volunteer will move on to the next card. The process is repeated with the left eye (patching the right eye). This test is designed to detect problems with distance vision (myopia) or astigmatism in at least one eye. This test may not detect farsightedness.

HOTV Distance Visual Acuity Test: Instead of pictographic symbols, the letters H, O, T, and V are used. The procedure for testing is identical to the LEA Symbols test. This test is designed to detect myopia or astigmatism. Farsightedness may be missed with this test.

Random Dot E Stereoacuity Test: This test is designed to verify the child is capable of three-dimensional vision. The letter "E" is presented, alongside a random dot pattern and a stereoscopic letter "E" embedded within dots. The child wears stereoscopic glasses: if the child is able to identify the card containing the letter "E," the child is capable of three dimensional vision (i.e. both eyes are working together). This test can detect anisometropia (a difference in vision between the two eyes) and amblyopia.

iScreen Photoscreener: This automated screening system requires a child to sit in front of a camera, and look at a red light. The screener fixes the child's gaze in the crosshairs of the photoscreener, then takes an image of the child's eyes. The image is sent to the iScreen company for interpretation. This method can detect eye misalignment (strabismus), myopia, farsightedness, anisometropia, and may also detect astigmatism.

Cover-Uncover Test: The cover-uncover test is designed to detect strabismus. One eye is covered, the child is asked to look at an image, and then the eye is uncovered after approximately 3 seconds. The screener observes any eye drift or re-fixation once the paddle is removed. The procedure is repeated with the other eye.

The Welch-Allyn SureSight^TM Vision Screener is an automated vision screening platform. This is an example of the automated vision screeners used by the Lion’s Club and other volunteer organizations dedicated to saving children’s sight. The vision screener users lights and sound to obtain the child’s attention, and the reading is complete within five seconds. This is especially advantageous when considering the short attention span of most preschoolers! One eye is tested at a time, preventing a child from compensating by “peeking,” a common problem with standard eye-chart screenings. This type of vision screening is non-threatening, as it takes place 14 inches away from the child’s eye. In addition, the screening instrument automatically marks abnormal results, removing the need for interpretation of data by the volunteers.

The Welch-Allyn SureSight^TM Vision Screener has the following referral criteria for children ages 3-5:

• Sphere: < -1.0 or > +2.0 (this indicates the presents of myopia or hyperopia, respectively)

• Cylinder: > 1.0 (this indicates the presence of astigmatism)

• Difference: > 1.0 (this indicates a difference in refractive power between the two eyes)

The Lions Club: The Lions Club states that every preschooler should have their vision screened at the age of three. Conditions such as amblyopia are much easier to correct when the problem is found early. Many Lions Club locations offer free preschool visions screenings for interested preschools or other childcare groups.

The Rotary Club: The Rotary Club is another organization that provides volunteer-based vision screening in certain locations. Check with a local club to determine if this service is offered in a specific area.

InfantSee: the InfantSee program does not address preschoolers, but offers a free comprehensive eye exam to all children under the age of 12 months. Check the main website (linked above) to find providers participating in this program.

Prevent Blindness America offers vision screening training and vision screening services throughout the United States.

A referral on a vision screening test is not a diagnosis. Children who "refer" on a Vision Screening test must be sent to an optometrist or ophthalmologist for a complete vision examination. A full vision exam will take approximately 1½ - 2 hours, and will accurately identify the source of any existing vision problem. Most vision screening programs will provide a list of qualified optometrists and ophthalmologists for follow-up.

In addition, a child who passes a vision screening test should have a complete eye examination prior to kindergarten. Despite the increasing accuracy of many vision screening devices, none can take the place of a comprehensive vision examination by an eye care professional. Some children have "passed" vision screening techniques, only to be found with a significant vision problem later on.

Many children may not display any obvious signs of a vision difficulty, especially when one eye is affected. Some common symptoms of vision problems in preschool aged children include:

• Frequently rubbing they eyes.
• Itchy, watery eyes.
• Closing one eye when exposed to sunlight.
• Sitting extremely close to the television.
• Doesn't pay attention during story time at school ("daydreams").
• Bumps into objects frequently.
• Overly sensitive to light.
• Eyes appear to cross or drift.
• Closes one eye to see better.
• Complains of headaches.
• Has an unusual spot in the eye, evident when looking at photos taken with a flash (instead of the normal "red-eye," a white spot is visible). 

We have a young son with congenital hearing loss, which causes us to be very cautious with regard to his vision. We took him in for the free eye exam, compliments of the InfantSee program, when he was about eight months old. The exam showed healthy eyes which were very slightly myopic, which did not require correction. In fact, his vision was good enough to "pass" a preschool vision screening program through the Lion's Club when he was two years old.

The same vision screening process was repeated when he was three years old. Instead of a thin sheet indicating a "pass" value, we received a thick packed with a "refer" marked on the front page. The local Lion's Club uses the Allyn-Welch SureSight^TM vision screener, and the printout was included on the front page of the report.

The checklist indicated he had referred for myopia and astigmatism: his right eye showed a refractive error of -1.6 with a "cylinder" of +2.6. His left eye, interestingly, showed a farsighted reading of +2.5. The difference between the eyes was a whopping 4.1 diopters, which has the potential to cause amblyopia (permanent loss of vision in one eye due to a big difference in refractive power between the two eyes).

This finding was highly important, as it is critical to address our son's vision needs before his sight is compromised in any way. His comprehensive vision revealed that he had significant amblyopia (lazy eye), and his right eye was legally blind. He now wears glasses and may undergo patching therapy to improve the vision in that eye - he is now correcting to 20/40, which is a significant improvement! While we cannot correct his hearing loss, we can correct (and prevent) his vision loss - this is why preschool vision screening is necessary!