23 Impact of Visual Impairments on Testing

Visual acuity

• Reading small text. Even if a student is able to read the text, it may be highly demanding, resulting in slower reading, visual fatigue, and avoidance. Reading enlarged text may be easier but may also be slower.

• Accurately seeing small details in pictures, such as the facial expressions of people in the picture (e.g., “Which one shows laughing?”).

• Seeing the difference between small, similar objects or shapes (e.g., a small circle vs. a small square on WISC Figure Weights).

• Tasks that rely on quick visual scanning (e.g., WISC Coding and Symbol Search).

In addition to other aspects of their vision and visual-perceptual skills, we need to consider the student’s familiarity with the material. For example, think about when a child is learning to read. We provide young students with enlarged font as they are becoming familiar with letters and words. A student’s familiarity with the material will make a difference in what they are able to understand visually.

It is important to remember that a student’s visual acuity does not “tell the whole story” of what they are able to see. Consulting with the student’s TVI and reviewing the student’s Functional Visual Assessment and Learning Media Assessment will give you insight into how that student uses their vision.

Depth perception/single-eye vision

Depth perception is important for many aspects of a student’s life. However, a lack of depth perception should not impact a student’s performance on your psycho-educational assessment.

Color vision

Color blindness is a relatively common condition in the general population. Therefore, test publishers will typically consider this when developing their tests. Pearson (publisher of common IQ tests such as the WISC, WASI, WAIS, and WPPSI) published a FAQ (Pearson, 2023), which discusses the various steps they take to ensure the tests are fair for colorblind people. Test manuals should have information about the impact of color vision on their specific test. One area where a psychologist should be particularly aware of the impact of color vision is on “Stroop” type tests, which require the student to name the colors they see quickly. For a student with color blindness, it would be best to skip this type of test.

Loss of vision in the center of the visual field

The center of our visual fields is important for seeing color and fine details. When a student has visual conditions that impact the center of their visual field, they may use a head turn or look at things “out of the corner of their eye” to take advantage of their intact area of vision. The student may not detect the loss of small spots of vision as our brains “fill in” missing information. Because we use the center of our vision to see details clearly, students with significant central visual field loss are likely to have difficulty with some of the same things listed above under “visual acuity.”

Loss of peripheral vision (“tunnel vision”)

Loss of vision in the periphery of the field of vision (sparing central vision) has many impacts on orientation and mobility. In most cases, it is not likely to impact your psycho-educational assessment. However, if the student has a very constricted visual field, using their vision may be highly fatiguing. With a very constricted visual field, students may have difficulty integrating multiple parts of a stimulus picture. For example, if the student cannot keep the entire picture in their field of vision at once and must scan around the page, this increases the working memory load of the task. Rather than being able to see a stimulus and all of the responses at once, the student must scan and hold in mind each one separately.

Other visual field loss

Please see the previous discussion of homonymous hemianopia and its impact on reading. To summarize, right homonymous hemianopia (RHH) impacts the right half of the field of vision of both eyes and left homonymous hemianopia (LHH) impacts the left half of the field of vision of both eyes. In languages read left to right (like English), RHH will have a larger impact on reading, as readers in English scan ahead with their right peripheral vision (Lawrence et al., 2018). LHH can also impact reading as students may get lost between lines of text. RHH and LHH should be considered when interpreting the accuracy and speed of a student’s reading.

It is important to make sure that students with a RHH or LHH are scanning across a page appropriately. For example, if they are consistently making choices from one side of the page versus the other, this may be due to missing information on their affected side.

Students with homonymous hemianopia who have learned to scan across pages well may still show scanning errors when pushed for speed, such as on tasks like the WISC’s Symbol Search subtest. Students may show “false negatives” on this subtest when the target stimuli to search for is on their affected side. In the picture below, there are two symbols on the left (a star and a circle with a plus in it), which are the target stimuli to search for on the right. A student with RHH might make a mistake and choose “No.” When they quickly view the shapes on the left, they miss the shape on the right side (a circle with a plus) and only search for the star. Then, when they scan the shapes on the right, they do not see a match. In this case, the subtest cannot be interpreted as a valid measure of processing speed. Close examination of student errors is essential.

Students with a loss of vision in a single quadrant (e.g., upper right or lower left) of their visual field will likely show less impact on psychology testing. In particular, an upper quadrant field loss should not impact a student’s performance on testing.

Contrast sensitivity

Contrast sensitivity is the ability to detect subtle visual differences between light and dark. It is especially important in conditions with low light or glare. In the psychology assessment, someone with difficulty with contrast sensitivity could have difficulty reading text if written in a light color or placed on a darker background. They may have difficulty seeing their own writing if using a light pencil.

Cortical/Cerebral visual impairment (CVI)

Individuals with CVI may show a variety of visual challenges. You may see difficulty with contrast sensitivity, challenges with visually complex or crowded tasks, trouble focusing visual attention, or fluctuations in visual functioning. In the psycho-educational assessment, the student may have difficulty with efficiently visually scanning a page, especially when it is visually complex. This could include difficulty scanning across multiple choice options, such as on a Matrix Reasoning task. The student might be easily overwhelmed by visually complex materials, including a busy worksheet.

Fatigue

Although not a visual condition, fatigue is an important issue for the evaluator to understand. Fatigue may stem not only from straining to see (eye fatigue) but may also be due to postural fatigue from turning heads and bodies in awkward ways. Children may not fully recognize their own fatigue, so the evaluator must be very alert. Watch for behavioral signs that indicate fatigue has set in, and provide regular breaks. It can be helpful to ask the student’s teacher about their limits before the evaluation and try to stop five minutes before that time limit. A break can be as simple as looking away from the materials while chatting for a few minutes or going for a walk. Purposefully alternating visual and verbal tasks during the assessment also can be helpful.

References

Lawrence, L., Jones, M., & Vernick, A. (2018). Vision after hemispherectomy, TPO disconnection, and occipital lobectomy: An introductory guide. The Brain Recovery Project: Childhood Epilepsy Surgery Foundation. https://epilepsysurgeryalliance.org/wp-content/uploads/2017/06/FINAL-Vision-After-Hemispherectomy-TPO-Disconnection-and-Occipital-Lobectomy.pdf

Pearson. (2023, August 30). Wechsler products: Is color blindness a factor. https://support.pearson.com/usclinical/s/article/WISC-V-Color-Blindness-Accommodations