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1. Check on Mono-ocular or binocular ? 

2. Whether the diplopia is horizontal, vertical, or oblique. ? 

3. Whether one of the images is tilted or not?

4. Whether the diplopia is worse in a particular direction of gaze or with near or distant visual tasks?

A) The misalignment can be due to

1. Weakness of one of the EOMs
2. Over action of one of the EOM
3. The muscle is prevented by acting because of a problem with the antagonist
   a. The antagonist fails to relax (ocular neuromyotonia)
   b. Simultaneous unwanted contraction (aberrant reinnervation), or
   c. Restrictive ophthalmopathy (something preventing it from relaxing)

B) It can be by infiltration,

C) It can be by fibrosis of the muscle or muscle getting stuck by some means( eg: blow out fracture)

D) The misalignment need not always due to a eye movement problem

• Failure to keep the eyes in the parallel position due to vestibulo- ocular dysfunction can also produce diplopia  Eg: Skew deviation

Why should the images fall on non-corresponding parts of retina?

The images fall on non-corresponding parts of the retina, because of mis-alignment of the eyes.

This mis-alignment may be in the primary position or when patient looks in to one direction.

Diplopia will not occur in cases of long standing misalignment because brain learns to suppress one image: eg congenital squint. Hence, diplopia is a symptom of a recent acquired misalignment.

Patients with diplopia may not always complain of double vision.

Symptom

Most of the complaints from the patients can be 

1. Dizziness.
2. Imbalance.
3. Defective eye-hand coordination.
4. Overlapping images (ghosting).
5. Difficulty in negotiating stairs.

How you can diagnose diplopia in the above situations?

You can ask the patient to close one eye and ask them whether symptoms that they have disappear.

Diplopia

Detailed examination reveals no obvious extra ocular muscle weakness.

Diplopia is due to failure of fusion of images.

Types of diplopia : There are two types

1. Binocular
2. Uniocular

Uniocular

1.     Diplopia that persists even when patient closes one eye.
2.     Diplopia improves with pin-hole

What are the causes of Uniocular

1. Ocular causes: Example : Refractive errors
2. Occipital lobe lesions
3. Functional cause

Binocular

What is See-Saw Nystagmus?

In see-saw nystagmus one eye moves up + intorts & other eye moves down +extorts

Torsional component is conjugate

Vertical component is dysconjugate

1. Wave form is pendular or jerk

What are the types of See-Saw Nystagmus?

Pendular see-saw nystagmus

Seen in

1. Suprasellar lesion
2. Visual loss
3. Joubert's syndrome

Jerk see-saw nystagmus: (Hemi see-saw nystagmus)

Half cycle is pendular with corrective half cycle jerky

Seen in

1. lesions of INC (caudal thalamus-rostral midbrain)

See-Saw Nystagmus Pathogenesis:

Midbrain

Unilateral inactivation of INC

Sparing of riMLF

Afferent

1. Bitemporal hemianopia.
2. Visual loss-visuo-vestibular fibres
3. Chiasmal miswiring

What are the causes of Acquired Pendular nystagmus ?

1. Acquired Pendular nystagmus can be seen in the following conditions
2. Oculo-palatal myoclonus
3. See-saw nystagmus
4. Oculomasticatory myorhythmia
5. Visual loss
6. Spasmus nutans