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What is a Brock String, and How Do We Use It?


4 min


What is a brock string and how we use it

If you were exploring vision training and eye exercises, you might have come across the term ”Brock String”. It’s a simple yet effective tool in vision therapy used to assess and improve a range of visual skills. In this blog post, we’ll explore what Brock String is, how it works, and the benefits it offers for both vision therapy and sports performance.

What is a Brock String?

A Brock String is a low-tech, affordable vision training tool consisting of a string and a series of colored beads. It was developed by Dr. Frederick W. Brock, an American optometrist, in the 1950s. This string has since become a staple in the field of vision therapy and is widely used by optometrists, therapists, and athletes to enhance various visual skills.

For Which Vision Issues Is Brock String Used For?

It is a highly effective tool for vision therapy, commonly employed in addressing various types of convergence issues, including convergence insufficiency.

Children who struggle with reading difficulties or exhibit slow reading tendencies frequently encounter convergence challenges. Furthermore, it is also beneficial for individuals dealing with conditions like amblyopia and strabismus.

How to Use a Brock String?

The Brock String is simple in design but highly effective in training the visual system. It typically consists of a string, around 3-4 feet long (1-1.2m), with several colored beads evenly spaced along it.

One end can be fastened to an object like a doorknob, or it can be grasped by a supervising individual. The other end is held against the tip of the nose. The beads are evenly spaced along the string.

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Step 1: Focus

The person looks at the first bead closest to them. Since the string is anchored at eye level, this brings the bead into focus.

Step 2: Shift

The individual then shifts their gaze to the next bead. The goal is to maintain clear focus on this bead while keeping the other beads in their peripheral vision. Furthermore, the subject should see two strings entering the bead and two strings leaving it, making a large “X”.

Step 3: Continue

The person continues shifting their gaze from bead to bead, alternating between near and far vision, ensuring that all the beads are clear and single.  You should notice the two strings making a “V” toward the bead and crossing exactly at the bead. The two closest beads will be double. 

Steps to follow for brock string exercises.

Benefits of Using a Brock String | Learn to See with Both Eyes Simultaneously

Eye Teaming

The Brock String helps improve eye teaming, also known as binocular vision. It encourages both eyes to work together, which is crucial for depth perception and maintaining a single, clear image.


Accommodation refers to the ability of the eyes to adjust their focus from near to far objects. Using a Brock String challenges the accommodation system, helping it become more flexible and responsive.


Convergence is the ability of the eyes to turn inward to focus on a near object. If you are not converging, then one eye remains looking forward instead of meeting with the other eye. If this is one of your problems, then you may be seeing double. The string helps improve convergence, making it easier to view nearby objects, such as reading or working on a computer.

Brock String and Convergence Insufficiency

An inability or decreased ability to converge the eyes whilst focusing on near objects is described as convergence insufficiency. With the Brock String vision therapy tool, the eyes are forced to work together, improving convergence skills and strengthening the eye muscles.

According to several reports, such exercises can have as high as 80% success rate in alleviating the inability to converge properly

Brock string exercises

Benefits of Brock String eye exercises include improved eye teaming, accommodation, and convergence.

Sports Performance

Athletes use the Brock String to enhance their visual skills, including hand-eye coordination, tracking moving objects, and maintaining focus on a target while being aware of their surroundings. This can significantly improve their performance in sports like tennis, baseball, or golf.


A Brock String is a valuable and straightforward tool for improving various visual skills, including eye teaming, accommodation, and convergence.

It’s widely used in vision therapy to help individuals with vision problems, as well as by athletes seeking a competitive edge in their respective sports.

So, if you’re looking to enhance your visual abilities or seeking to help someone improve their vision, consider giving the Brock String a try. It’s an accessible and effective way to level up your visual game.

Frequently Asked Questions

What is a Brock String, and how does it work?

A Brock String is a vision training tool consisting of a string with colored beads. It’s used to improve visual skills like eye teaming, accommodation, and convergence. The individual focuses on one bead at a time, practicing the shift of their gaze from near to far objects.

Can anyone benefit from using a Brock String, or is it primarily for people with vision issues?

While the Brock String is commonly used in vision therapy to address vision problems, it can benefit individuals with healthy vision as well. Athletes, in particular, use it to fine-tune their visual skills for sports performance.

How often should one use a Brock String for noticeable improvements?

The frequency of use can vary depending on individual goals and needs. In general, consistent practice, even for a few minutes each day, can lead to noticeable improvements over time.

Can you make your own DIY Brock String, or is it better to purchase one?

You can create a DIY Brock String by using a string and colored beads. However, purchasing a professionally made Brock String is recommended for accuracy and durability.

Are there any precautions to consider when using a Brock String?

It’s important to use the Brock String in a well-lit area, take breaks if you experience eye strain, and consult an eye care professional if you have pre-existing eye conditions. Always use it as recommended by a vision therapist or optometrist.

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Why Do We Suggest a Minimum Time of 6 Months for Success?

Based on the data from over 15,000 patients using AmblyoPlay, improvements start within 4 months, while optimal results take anywhere between 6-18 months on average. The duration of required training depends on the patient’s age, the severity of the problem, accompanying diseases, and adherence to the training program.