Examination of the optic nerve

EXAMINATION OF THE OPTIC NERVE-Dr Akshay Nayak

Headings to consider in general

1. Visual acuity

2. Colour vision

3. Field of vision

4. Pupillary reaction

5. IOP

6. Ophthalmoscopy

7. Slit lamp

8. Fluorescein angiography

9. X ray/ct skull,pns,orbit

10. Visually evoked potential{vep}

11. OCT

Signs of optic nerve dysfunction

• Reduced Visual Acuity

• RAPD

• Dyschromatopsia

• Diminished light brightness sensitivity

• Diminished contrast sensitivity

• Visual field defects

Pupillary Reflex Pathway

Grades of RAPD and Causes

• +1 – initial constriction followed by early release of affected pupil

• +2- no movement initially, followed by pupillary release

• +3- immediate pupillary dilation

• +4- amaurotic eye( no light perception)

Causes-

1. Optic neuropathy

2. Extensive Retinal Damage

3. Amaurotic Eye

Visual Field Examination

1. Confrontational Visual Field Examination

2. Tangent Screen test or Bjerrum screen

3. Automated Perimetry

• Normal fields extend – approximately-

100deg temporally, 60deg nasally, 60deg superiorly and 70deg inferiorly

• Blind Spot dimension-horizontally- 7-8 *vertically 10-11 *

Visual field assessment

• Colour Vision- Ishihara and Hardy-Rand Rittler

• Contrast sensitivity- Sloan chart and Pelli Robson chart

• BINOCULAR VISION AND STEREOACUITY

o ACUITY IN BINOCULAR VISION> UNIOCULAR – due to cortical summation of visual input from both eyes

• Stereoacuity

Visual Evoked Potential• Principle-electrical activity of visual cortex recorded due to retinal

stimulation

• Used in optic neuropathy especially when associated with demyelination

• Technique-

• Flash of light(flash vep)

Merely tells light is perceived

• Checkerboard(pattern vep)

Timing of onset of response is more important

Delay- retrobulbar neuritis(persists even when vision returns to normal)

EXAMINATION OF A CASE OF PAPILLOEDEMA

Symptoms-

Systemic-headache, vomiting,convulsions etc

Ocular

• NIL , transient or persistent blurring of vision , diplopia, ocular deviation

• Visual acuity and pupillary reactions are NORMAL for a long time.

• Fundus• Early

o Blurring of disc margin and hyperemia

• Established-bilateral and equal

o Peri papillary retinal oedema

o Linear or flame shaped hemorrhages

o Circumferential retinal folds

o Venous pulsation is ABSENT

• Chronic

o Disc oedema is +4.0D.

o Vessels disappear in the swollen and hyperaemic disc

o Hard exudates at macula

• Late

o Sheating of blood vessels,pallor and waxy discoloration of disc

o Post pappiloedematous optic atrophy replaces hyperemic disc

• FIELD CHANGES

• EARLY- enlargement of blind spot

• LATE- peripheral constriction

FUNDUS FLUORESCEIN ANGIOGRAPHY

• Diffuse fluorescence of head(due to retention of dye in retinal veins and oedematous fluid over disc)

Fundus fluorescein angiography of the left eye with papilloedema. A rapid series of fundus photographs follow the intravenous injection of a fluorescent contrast agent. In true disc swelling, the frames (A – D) show progressively increased intensity and area of fluorescence at the disc. This shows fluorescein leakage from the oedematous disc.

EXAMINATION OF A CASE OF OPTIC NEURITIS

• Symptoms

1. Sudden loss of vision

2. Light in room appears dim in affected eye

3. Generally unilateral

4. Scotoma

5. Pain on movement of eye

6. Loss of color vision

• Signs

1. Reduced visual acuity

2. Reduced/Faulty Color vision

3. Depth perception is faulty

4. Pupils- Size is normal in spite of loss of vision

RAPD

Consensual and near reflexes maybe normal

Fundus

• Early- No change or slight hyperemia of disc.

• Fully developed- elevation of disc but not more than +3D

Physiological Cup is lost

Linear or superficial hemorrhages

Severe—Macular star

SLE- Vitreous haze in front of disc

• Late- pale disc, margins remain blurry, vessels narrow and sheated.

Post neuritic optic atrophy

Diagnosis of retrobulbar neuritis

Examination of an eye with optic atrophy

• TO Diagnose-

1. Pallor of disc

2. Decreased vision

3. Pupillary changes

4. Field changes

5. Defective colour vision

Special types of Optic Atrophy

• Temporal Pallor-

Architecture of disc is normal.

Congenital anomalies of disc and macula, cerebromacular degeneration, retrobulbar neuritis etc

• Segmental Pallor- One segment adjacent to juxtapapillary choroiditis

• Altitudinal pallor

Ischemic optic neuropathy

• Bow tie pallor

Chiasmal , retrochaismal and pre-geniculate lesions

Bitemporal hemianopia

Temporal pallor in optic atrophy

Band or bowtie atrophy of the optic disc indicates the presence of a lesion in the contralateral optic tract involving crossed retinal fibers nasal to the fovea

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