Assessment of Binocular Vision Problems

Vocabulary-style flashcards covering the core 10 clinical tests for binocular vision assessment, including procedural details and expected clinical norms.

Heterophoria

A latent deviation of the eyes that is only present when binocular fusion is broken.

Heterotropia

A manifest strabismus where the eyes are not aligned even when both eyes are open and fusion is not broken.

Unilateral Cover Test (Cover-Uncover)

A procedure where one eye is occluded and the uncovered eye is observed for a refixation movement to identify if a Tropia is present.

Alternating Cover Test

A procedure where an occluder is moved rapidly between both eyes to break binocular fusion and reveal the total deviation (Phoria + Tropia).

Cover Test Expected Norms (Distance)

$1\,PD$ Exo $\pm 2\,PD$

Cover Test Expected Norms (Near at $40\,cm$)

$3\,PD$ Exo $\pm 3\,PD$

Maddox Rod

A red cylindrical lens that converts a white spotlight into a red streak line to subjectively measure the direction and magnitude of vertical or horizontal deviations.

Von Graefe Technique

A subjective measurement performed inside the phoropter using Risley prisms, where a vertical dissociating prism doubles the targets and a horizontal measuring prism is adjusted for alignment.

Near Point of Convergence (NPC)

The distance where an accommodative target moved toward the nose causes one eye to drift outward (Break) or results in single vision restoration (Recovery).

NPC Expected Norms

Break: $\le 5\,cm$; Recovery: $\le 7\,cm$

Jump Convergence

A test where the patient rapidly switches fixation between a distant target at $6$ meters and a near target at $20\,cm$ to observe vergence adjustment speed.

Fusional Reserves (Vergence Ranges)

The measurement of motor vergence energy available to maintain binocular single vision against induced disparity, recorded as Blur, Break, and Recovery.

Negative Fusional Vergence (Divergence)

The vergence energy tested by introducing Base-In ($BI$) prism power.

Positive Fusional Vergence (Convergence)

The vergence energy tested by introducing Base-Out ($BO$) prism power.

Morgan's Norms for BI at Near

$x / 13 / 9\,PD$ (Blur / Break / Recovery)

Morgan's Norms for BO at Near

$17 / 21 / 11\,PD$ (Blur / Break / Recovery)

Vergence Facility

An assessment of the dynamics, stamina, and agility of the vergence system over a $1$-minute period using prism flippers ($12\,PD\,BO$ and $3\,PD\,BI$).

Vergence Facility Norms

$15 \pm 3$ cycles per minute ($cpm$)

Amplitude of Accommodation (AA)

The absolute maximum focusing power of the crystalline lens.

Push-up Method (RAF Rule)

Moving a small target closer to the eye until sustained blur occurs, calculated as $\text{Diopters} = \frac{1}{\text{distance in meters}}$.

Minus Lens Method

Measuring AA by adding minus lenses monocularly to a target at $40\,cm$ until blur occurs; total $\text{AA} = \text{added lens power} + 2.50\,D$.

Hofstetter's Formula for Minimum Amplitude

$$\text{Minimum AA} = 15 - (0.25 \times \text{Age})\,Diopters$$

Accommodative Facility (Lens Flippers)

A test of the ciliary muscle's speed and stamina to accommodate and relax using $\pm 2.00\,D$ lens flippers over $1$ minute.

MAF and BAF Norms

Monocular (MAF): $11\,cpm$; Binocular (BAF): $8\,cpm$

Accommodative Convergence / Accommodation (AC/A) Ratio

The amount of accommodative convergence stimulated for every $1$ diopter of accommodative change.

Calculated AC/A Method Formula

$$\text{AC/A} = \text{IPD(cm)} + \text{Near Demand} \times (\text{Near Phoria} - \text{Distance Phoria})$$

Gradient AC/A Method

Measuring the change in phoria at a fixed distance after introducing an accommodative lens (e.g., $\pm 1.00\,D$).

AC/A Ratio Expected Norms

Between $4:1$ and $6:1$ (Prism Diopters per Diopter of accommodation)

Worth 4 Dot Test

A suppression test using Red/Green filters; seeing $2$ red lights indicates OS suppression, while $3$ green lights indicate OD suppression.

4 Prism Diopter Base Out Test

A test for suppression where a prism is placed over one eye; absence of a diagnostic refixation saccade in the opposite eye confirms suppression.

Stereopsis

Cortical depth perception and the highest level of binocular sensory cooperation.

Stereoscopic Threshold Norm

$\le 40$ seconds of arc ($arcsec$)