How do you perform a phoria test?

A phoria (or latent deviation) only appears when binocular viewing is broken and the two eyes are no longer looking at the same object. The unilateral cover test is performed by having the patient focus on an object then covering the fixating eye and observing the movement of the other eye.

How do you do a phoria test?

Move the lens dial and instruct the patient to tell you when one image lines up above the other (horizontal testing) and when the images line up side by side (vertical testing). The expected norms for phoria testing are 1pd of exophoria at distance (1pd) and 3pd of exophoria at near (3pd) for every patient.

Which test is used to detect a phoria?

The cover-uncover test is generally performed first. The cover-uncover test is useful to identify a tropia and differentiate it from a phoria. The test is done by using an opaque or translucent occluder to cover one eye. The occluder is held in front of the eye for a few seconds and then removed.

How do you perform an ocular motility test?

You are asked to sit or stand with your head up and looking straight ahead. Your provider will hold a pen or other object about 16 inches or 40 centimeters (cm) in front of your face. The provider will then move the object in several directions and ask you to follow it with your eyes, without moving your head.

What is a normal phoria?

Mean estimates of phoria in adults range from 3 to 5 prism diopters (pd) of exophoria (divergent misalignment) at near viewing distances (33 or 40 cm), and from 0 to 1 pd for a distant target (6 m).

How do you explain phoria to a patient?

A phoria is a misalignment of the eyes that only appears when binocular viewing is broken and the two eyes are no longer looking at the same object. The misalignment of the eyes starts to appear when a person is tired, therefore it is not present all of the time.

What is a Decompensating phoria?

Any latent binocular misalignment that becomes symptomatic is considered to be a phoria that has “decompensated.” Symptoms of decompensated esophoria may range from simple headache to severe asthenopia and diplopia.

How do you perform a unilateral cover test?

The unilateral cover test is performed by having the patient focus on an object then covering the fixating eye and observing the movement of the other eye. If the eye was exotropic, covering the fixating eye will cause an inwards movement; and esotropic if covering the fixating eye will cause an outwards movement.

How do you do a confrontation test?

Confrontation visual field testing involves having the patient looking directly at your eye or nose and testing each quadrant in the patient’s visual field by having them count the number of fingers that you are showing. This is a test of one eye at a time.

How do you do a 4 dot test worth?

With both eyes open, a patient with normal binocular vision will see four lights. If the patient either closes or suppresses an eye they will see either two or three lights. If the patient does not fuse the images of the two eyes and sees double (diplopia), they will see five lights.

How do you measure phoria with a prism?

To determine the associated phoria, add prism in the appropriate direction until the patient reports that the arrow is aligned with the center line. At distance, the American Optical vectographic slide is commonly used to determine the associated phoria.

What is lateral phoria?

Lateral Phoria Test measures different tests for muscle balance between two eyes. Features: Measures vertical balance between the two eyes. Measures in steps of 1 diopter. Identifies if there is esophoria (one eye turns inward compared to the other)

How do you test Fusional reserves?

Fusional reserves are easy to assess using a prism bar, and with some keen observation can become an objective measure of your patient’s ability to maintain the correct balance of convergence and divergence at near.

How do you write prism on a prescription?

Two Criteria for Determining Prism



The formula: Prism needed = 2/3(phoria) – 1/3(compensating fusional vergence). So, if a patient has 6∆ exophoria and base-out (BO) to blur is 6∆, the prism needed would be 2/3(6) – 1/3(6), or 4 – 2. You would prescribe 2∆ base-in (BI), since deviation is exophoria.

Can convergence insufficiency cause headaches?

Convergence insufficiency refers to a common near-vision problem that interferes with your ability to read and work at close distances. As with strabismus, convergence insufficiency can cause chronic headaches.

What are normal Fusional reserves?

The fusional reserves are the maximum amount the eyes can converge (positive fusional reserves, measured with base out prism) or diverge (negative fusional reserves, measured with base in prism) while still maintaining BSV. As the image doubles, the break point is reached.

How do you record fixation disparity?

Objective fixation disparity (oFD) is defined as the oculomotor vergence error that can only be measured with eye trackers, i.e. oFD = V – V0 . This is the difference between the vergence angle in binocular vision (V, red line in Fig.

What is NRA and PRA?

The two tests of positive relative accommodation (PRA) and negative relative accommodation (NRA) measure the maximum ability to stimulate accommodation while maintaining binocular single vision. These two tests can also help with indirect evaluation of fusional vergence.

What are Fusional ranges?

The prism fusion range (PFR) or fusional vergence amplitude is a clinical eye test performed by orthoptists, optometrists, and ophthalmologists to assess motor fusion, specifically the extent to which a patient can maintain binocular single vision (BSV) in the presence of increasing vergence demands.

What is normal phoria at near?

Normal results for near phoria generally fall slightly on the exo side, with a mean of 3 exophoria and a standard deviation of 5 indicating 68% of the population lie between 2 esophoria and 8 exophoria.

How do you do the Maddox rod test?

Youtube quote:And you have no diplopia and no ophthalmoplegia you'll see the light right on top of the line. But if you have a hypertropia the light will be either above or below the line.

What is sensory fusion?

Sensory Fusion



It is the ability to appreciate two similar images, one with each eye and interpret them as one. Single visual image is the hallmark of retinal correspondence.

What are the grades of BSV?

Binocular single vision (BSV) is the ability to use both eyes together to achieve a single fused percept, even in the presence of disparity of the image seen by each eye. It is divided into five grades: simultaneous perception, superimposition, sensory fusion, motor fusion, and stereopsis.

What does it mean if my child has a Anisometropia?

Anisometropia means that the two eyes have a different refractive power, so there is unequal focus between the two eyes.