Binocular Vision Assessments

Different than a standard test

Binocular vision assessment is not part of the standard eye test – so what is it and why is it so important?

We are all familiar with an eye test, which measures if you have ‘20/20 sight’ and if you need glasses or contact lenses. But, the eyes are very complex, and deeper and more comprehensive tests can be provided by specific eye doctors.

Early detection through regular screenings is key to managing and mitigating the effects of glaucoma.

Binocular vision assessments are a series of tests used by eye care professionals to evaluate how well your eyes work together as a team. This is crucial because proper binocular vision ensures that both eyes can focus on an object simultaneously, providing a single, clear, and cohesive image. These assessments help detect any issues with eye alignment, coordination, and depth perception.

Common Assessments

  1. Cover Test:
  •  Purpose: To check for any misalignment of the eyes (strabismus).
  • Procedure: The patient focuses on an object while one eye is covered. The examiner observes the uncovered eye for any movement, which would indicate that it had to adjust to maintain fixation on the object. This test is done for both near and distance vision.
  1. Near Point of Convergence (NPC):
  • Purpose: To assess the ability of the eyes to work together while focusing on a close object.
  • Procedure: The patient is asked to focus on a small object as it is slowly moved towards their nose. The point at which the patient sees double or one eye deviates outward is noted.
  1. Stereopsis Test:
  • Purpose: To measure depth perception, which relies on proper binocular vision.
  • Procedure: The patient wears 3D glasses and looks at special images (often dot patterns or shapes). They are asked to identify which part of the image stands out or appears closer.
  1. Phoria Test:
  • Purpose: To detect latent deviations of the eyes (phorias), which might not be apparent when both eyes are open but could cause symptoms like eye strain or double vision.
  • Procedure: Similar to the cover test, but it specifically measures the tendency of one eye to drift when the other eye is covered.
  1. Worth 4-Dot Test:
  • Purpose: To evaluate the presence and extent of binocular vision.
  • Procedure: The patient wears red-green glasses and looks at a panel with four lights (one red, two green, and one white). How many lights the patient sees helps determine if both eyes are working together.
  1. Maddox Rod Test:
  • Purpose: To measure the degree of misalignment between the eyes.
  • Procedure: The patient looks at a light through a Maddox rod, a lens with multiple red or white stripes. The way the light appears to the patient helps the examiner assess alignment issues.

Why Binocular Vision Assessments are Important

  • Detection of Amblyopia: Known as “lazy eye,” amblyopia is often related to binocular vision issues.
  • Strabismus Diagnosis: Early detection of misaligned eyes can prevent long-term vision problems.
  • Prescribing Prisms: If a patient has difficulty with binocular vision, prisms in glasses can help align the images seen by both eyes.
  • Management of Convergence Insufficiency: Difficulty focusing on close objects can be managed with specific exercises or lenses.
  • Improving Visual Comfort: Reducing symptoms like eye strain, headaches, or double vision during activities like reading or using a computer.
  • Tracking difficulties: this can cause challenges with reading and is easily treated with vision training. 

These assessments are typically performed during a comprehensive eye exam, especially if a patient presents with symptoms like double vision, eye strain, or difficulties with depth perception. Early detection and treatment of binocular vision problems can significantly improve visual comfort and overall eye health.