TOPIC 2: BV anomalies

Question 1

what is heterophoria?

Answer 1

A condition where both visual axes are directed towards the fixation point but deviate on dissociation (distruption of visual axes).

eyes are disassociated and the visual axis of the eye under cover deviates

It is a latent deviation.

Question 2

what are the 3 classifications of heterophoria

Answer 2

1. Direction of Deviation
   exophoria
   esophoria
   hyperphoria
   hypophoria
   cyclophoria (incyclophoria and excyclophoria)
   *Cyclophoria nearly always co-occurs
   with hyperphoria.
2. Fixation Distance
   Distance VS Near : 6 metres VS ⅓metres or 30-50m
   These are known as the ‘ distance phoria ’ and ‘ near phoria ’ , respectively
3. Compensation
   compensated phoria: asymptomatic

decompensated phoria:
May be symptomatic
Due to abnormal stress in BV

Possible symptoms includes:
Headache, asthenopia, eyestrain, occasional diplopia, blurry vision, photophobia etc

Question 3

what is the standardized recording for phoria?

Answer 3

Size (in Prism Diopters, ∆), Direction of Deviation, Speed of Recovery

Example: 10∆ XP, QR

Question 4

what is heterotropia (strabismus)?

Answer 4

A condition where one or other visual axis is:
-not directed towards the fixation point
-a misalignment of visual axes.
It is a manifest deviation.

Question 5

what are the 6 classification of tropia/strabismus?

Answer 5

1. comitancy
2. direction of deviation
   exophoria
   esophoria
   hyperphoria
   hypophoria
   cyclophoria (incyclophoria and excyclophoria)
   dissociated vertical deviation
3. fixation distance
   Distance VS Near : 6 metres VS ⅓metres or 30-50m
   These are known as the ‘ distance phoria ’ and ‘ near phoria ’ , respectively
4. eye preference
   Unilateral (R/L): Always use the same eye for fixation
   VS
   Alternating: Either eye can be used for fixation
5. frequency/constancy
   Constant: Strabismus present all the time and under all circumstances.
   -Possible asymptomatic, diplopia, asthenopia
   VS
   Intermittent: Strabismus present only sometimes
   -Headache, eyestrain, asthenopia, occasional diplopia
   Increased frequency and severity with increased intermittent diplopia

*useful to enquire about the proportion of time the strabismus is present. This is likely to depend on tiredness and can be highly variable

6. accommodative state
   The angle of the strabismus may vary with the amount of accommodation exerted. In hypermetropes/hyperopes this is an important factor in the treatment.

Fully accommodative: angle of deviation will be fully reduced by refractive correction of hypermetropia

Partially accommodative: angle of deviation will be partially reduced by refractive correction of hypermetropia

Non-accommodative: refractive correction does not appear to change the angle of deviation

Question 6

what is the difference between a comitant and an incomitant deviation?

Answer 6

Comitant Deviations: Same size in all directions of gaze, for a given fixation distance.
Commonly found in patients with congenital or early onset strabismus

Incomitant Deviations: Varying size in different directions of gaze.*
Commonly found in patients with abnormalities of anatomy or functioning of the motor system due to accident or disease (acquired)

It is important to distinguish incomitant deviations from comitant as the management is different and has different priorities. An incomitant deviation of sudden onset is usually caused by trauma or active pathology requiring urgent medical attention.

Question 7

what is the standardized recording for heterotropia?

Answer 7

Size (in Prism Diopters, ∆), Constancy, Affected Eye, Direction of Deviation

Example: 10∆ Constant R XT