Vision Therapy Activity: Hart Chart

If you have watched a vision therapy session at one of our offices, you have seen a Hart chart. It is a grid of letters and numbers, nothing more, and it is one of the most-used tools we own: by changing where the chart sits and how the patient works through it, the same piece of card trains three different visual skills.

Key takeaways

• A Hart chart is a grid of random letters and numbers, in a large wall size and a small handheld size.
• Row reading works on tracking and holding your place, the way you do in a book.
• Column jumping works on saccades, the fast eye jumps between two targets.
• The near-far Hart chart works on accommodative facility: changing focus between far and near quickly and clearly.
• A patch, a metronome or a balance surface changes the demand. Focusing measures do improve with therapy; we know of no trial showing that Hart chart work improves eye-movement measures, and the best reading trial was negative.

What a Hart chart actually is

A Hart chart is a square grid of evenly spaced letters and numbers, usually ten rows by ten columns, printed large for the wall and small for the hand. The characters are random, so nobody can coast on memory: each one has to be located, focused and identified before the eyes move on. That plainness is the point. Because the chart is so simple, we can change one variable at a time (where you look, how fast, one eye or two, sitting or standing) and see which part of the visual system is struggling.

The three core Hart chart activities

Row reading, for tracking

The simplest version is to read the chart straight across, row by row, like a book: hold your place across a line, return to the start of the next line without skipping or repeating, and keep going down the grid. This can be done patched or unpatched, depending on the goal for that patient.

Reading is not a smooth glide across a page. The eyes move in quick jumps separated by brief pauses, and those patterns closely reflect what the reader is processing moment to moment (Rayner, 1998). A grid of unrelated letters and numbers strips the language out and leaves the mechanics, which is why we use it as practice and never as a substitute for real reading.

Column jumping, for saccades

Here the patient reads two columns at a time, bouncing back and forth: first letter of the left column, first letter of the right, second letter of the left, and so on. The bouncing is the saccadic demand; keeping track of which letter and column you are on is the tracking demand, layered on top.

You can start with the two outermost columns and work inward, or start with the innermost pair and work outward so each jump gets larger as you go. It pairs naturally with our four corner fixation activity, which trains the same jumps across a much wider spread.

Near-far Hart chart, for accommodative facility

What it addresses: accommodation, acuity, tracking and visual anchoring. Hart charts train the accommodative system, the mechanism that changes focus between distance and near. Specifically they target accommodative facility, the ability to increase and decrease focus on demand. Several binocular vision problems reduce it: some people over-focus and cannot relax, others under-focus and see blur at near.

How to do it: place the larger chart on the wall at eye height. Hold the smaller chart at your normal reading distance while standing or sitting 5 to 10 feet from the far chart. Read the top line on the near chart, shift to the far chart and read its top line, then keep alternating line by line down both charts. The key detail is that each chart must actually be clear before you read it, not blurry-but-guessable.

That far-to-near routine is not just our exercise: it is the classical clinical test of binocular accommodative facility, and researchers validating a new objective instrument used it as their comparison standard, while arguing that the traditional chart test has methodological limits of its own (Vera et al., 2020). We measure with the same task we train with, which is why it shows up so often for patients working on accommodative disorders.

Variations we use, and why

• Patched. Covering one eye makes the activity monocular: useful when one eye needs practice alone, or when we want to see what each eye does unaided. See the role of eye patches in vision therapy.
• Metronome. It sets the rhythm, removes the option of slowing down when the task gets hard, and makes the pace measurable week to week.
• Standing, or on an unstable surface. A balance demand makes the visual system work while the body works too.
• Bigger gaps, smaller print. Moving the far chart back, shrinking the near print or widening the column spacing each raise difficulty along one axis.

What the research does and does not show

Focusing measures do improve with therapy. In the Convergence Insufficiency Treatment Trial, 74% of the 221 children with symptomatic convergence insufficiency also had accommodative dysfunction. After 12 weeks, amplitude of accommodation rose 9.9 D with office-based vergence and accommodative therapy versus 2.2 D with placebo therapy (Scheiman et al., 2011). That program was a defined protocol with home reinforcement measured against a matched office placebo, not an unstructured pile of exercises (CITT Study Group, 2008); for symptoms it produced a successful or improved outcome in 73% of children versus 35% with placebo (CITT Study Group, 2008). A Cochrane network meta-analysis of 12 randomized trials and 1,289 participants, six of them in children, found office-based vergence and accommodative therapy with home reinforcement more effective than placebo in children (relative risk 3.04, 95% CI 2.32 to 3.98), while calling the adult evidence less clear (Scheiman et al., 2020).

The symptom result did not repeat in the larger follow-up trial. In CITT-ART, 311 children were treated for 16 weeks. The clinical signs improved more with therapy than with placebo (near point of convergence 10.4 cm versus 6.2 cm, positive fusional vergence 23.2 versus 8.8 prism diopters), but symptom scores improved by a similar amount in both groups, 11.8 points versus 10.4 (CITT-ART, 2019). The trial’s authors concluded that symptom scores on their own are not a reliable way to judge success, because both groups improved on them. And in every one of these studies the children had convergence insufficiency, worth remembering before generalising the numbers.

A small sham-controlled study points the same direction. In 13 children with impaired relative accommodation, positive relative accommodation fell significantly during a sham phase with non-powered lenses (P = .01), and negative relative accommodation rose significantly once real powered-lens training began (P = .03); the other measure moved the same way in each phase without reaching significance (Sterner et al., 2001). Thirteen children is a very small sample, and only six of them completed each arm, so we treat it as supportive, not conclusive.

Hart charts specifically have only small, uncontrolled studies. Five symptomatic patients who did 7 to 10 weeks of accommodative facility therapy, 5 to 6 sessions of lens flipper and Hart chart work, reported fewer symptoms and measured better on accommodative facility (Ciuffreda & Ordonez, 1998). Ten young adults with progressing myopia trained at home for six weeks, 20 minutes a day and five days a week, using accommodative and prism flippers plus a Hart chart at distance (6 m) and near (40 cm); their Hart chart rate rose from 22 to 33 cycles per minute in the right eye and 22 to 31 in the left (Vasudevan et al., 2009). Neither study had a control group, both were aimed at nearwork-induced transient myopia rather than everyday focusing complaints, and both measured focusing, not eye movements: we know of no controlled trial testing whether Hart chart work improves saccadic or tracking measures.

Two honest limits. For accommodative insufficiency on its own, reported prevalence ranges from under 1% to 61.6% depending on the criteria used, and no high-quality evidence establishes a standard treatment protocol (Hussaindeen & Murali, 2020). And the largest, best-designed test of the reading question was negative: in 310 children, reading comprehension improved 3.7 points with vergence and accommodative therapy versus 3.8 points with placebo (CITT-ART, 2019).

Professional bodies read this differently. A joint statement from the American Academy of Pediatrics, the American Academy of Ophthalmology, AAPOS and AACO holds that vision problems do not cause dyslexia and that evidence does not support eye exercises for learning disabilities (AAP et al., 2009). The optometric position is that vision problems can and often do interfere with learning, and that the goal of care is improved visual function within a multidisciplinary plan (AAO/AOA, 1997).

Our clinical perspective

Here is where we stand at Vision & Learning Center. A Hart chart trains focusing and eye-movement skills. When an evaluation shows a measurable problem in those skills and it matches the patient’s symptoms, we treat it and we re-measure. We do not present a letter grid as a reading program and we do not promise grades. A child who struggles to read needs reading instruction from teachers and specialists, and may also need comfortable near vision so that instruction can land.

The Hart chart is one procedure among many, chosen for a specific finding. See how it fits the wider program in our overview of vision therapy goals and procedures, and how eye-movement work fits patients with ocular motor dysfunction.

If focus takes a moment to clear when your child looks up from a book, or near work brings on headaches and fatigue, that is worth measuring rather than guessing about. Schedule an evaluation or see what a comprehensive developmental vision evaluation includes.