Vision Screening Online Training Program - Questions and Answers Regarding Visual Acuity Screening

Vision Screening Online Training Program

Questions and Answers Regarding Visual Acuity Screening

Q.  There seem to be so many vision charts available, which charts are recommended in the Minnesota Vision Screening Guidelines for children under age 6?

A.  Visual acuity screening in the schools is recommended for children participating in the Early Childhood Screening program and students in grades 1, 3, 5, 7, and 10.  It is also recommended for transfer students, students receiving a special education evaluation, and upon parent, teacher or student request.

For C&TC well child exams, please refer to the C&TC Periodicity Schedule for specific vision screening recommendations by age (Click here for Periodicity Schedule).

The 10 foot  HOTV or the LEA chart with 50% spaced rectangle boxes around each line is the MDH recommendation for children ages 3-6. Following are the MDH approved visual acuity charts.   

Goodlite LEA Symbol Chart

Q. Are there tools available to help me prepare the child for screening?

A. There are other tools available to prepare very young children for vision screening, such as the Lea Puzzle. Young children will feel comfortable with the vision screening and will become familiar with the shapes used in the visual acuity charts by playing with the Lea Puzzle prior to the vision screening.

LEA puzzle.

Q.  What evaluative criterion was used in the development of the Vision Guidelines for these new vision acuity charts?

A. Chart selection was based on scientific research that demonstrated sensitivity, specificity, as well as testability, optotypes, distance, the presence of a 20/25 line, practicality of use and cost, and cultural and disability bias. Various state and federal regulations for screening programs, as well as the federal Head Start Performance Standards, were also reviewed.

Other considerations included in the recommendations for the Vision Screening Guidelines were:

  1. The 10-foot visual acuity charts should have the 10/12.5 line
  2. The charts should not have symbols or optotypes (either letters or symbols) that require functions other than recognition of the optotypes. Some of these charts introduce language or symbols that are not understood by the child or are not culturally sensitive.  This is an important consideration for conducting vision screening programs with New American, immigrant, or culturally and linguistically diverse populations.
  3. Optotypes should blur equally. When a symbol cannot be correctly recognized, the symbols ‘blur to zero’ or transform into circles called "rings" or "balls”.
  4. Ideally, the visual acuity charts should have either a proportional layout (the space above the line is equal to the size of the letter below) or have a linear layout (specific spacing between optotypes but not the lines).  Due to low testability, proportional charts are not recommended as the first choice for children under 5 years old.
  5. To achieve both high standards of testability and sensitivity, the visual acuity charts with the 50% spaced rectangle around each line of letters or symbols are recommended.  These rectangles create a ‘crowding phenomena’, which is considered by the National Institutes of Health’s Vision in Preschoolers (VIP) study as the best strategy to detect amblyopia.

Q.  What visual acuity charts do NOT meet the criteria for inclusion in the MDH Vision Screening Guidelines?

A.  Examples of visual acuity charts not recommended by the MDH for screening children in Minnesota are pictured below:

Visual Acuity Charts not recommended by MDH

Q.  What are the pass criteria for the recommended visual acuity charts?

A.  The pass criteria for:

Children ages 3 - 4 years: 10/20 or better in each eye without a 2-line difference
Children ages 5 years and older: 10/15 or better in each eye without a 2-line difference

Q.  What visual acuity chart is recommended for screening vision in children six years old and older?

A.  The 20 foot Snellen chart or the Sloan Charts are recommended.

The Pass criteria is 20/30 or better without a 2-line difference.  Please note, the addition of the 2 line difference is a change in 2006.  This means that in the pass range, they eyes must at least see lines next to each other (i.e. 20/25 line right eye, 20/20 line left eye).

Snellen Chart No. 600727 Snellen Chart Sloan Chart No. 600725 Sloan Chart

Q.  I know that 20 feet is the ideal distance to test visual acuity for children age 6 and older, I simply do not have the space. What can I do to accommodate these limitations in my facility?

A.  A 10-foot equivalent chart is available from several suppliers that could be used in vision screening environments when space is a factor.  (see below for example)

No. 600723 (Sloan, Linear Spaced Chart) #600723

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