Eye assessment

Eye anatomy

• Ethmoid bone paper thin and most likely sinus wall to break in blunt eye trauma or be perforated due to sinusitis with spread to orbit
• Arterial supply of orbit and eye is ophthalmic artery, first major branch of intracranial portion of internal carotid artery
• Central retinal artery is the first intra-orbital branch of the ophthalmic artery and courses through the optic nerve
• Venous drainage of the eye and orbit is through the ophthalmic veins, which drain into the central retinal vein
• Ophthalmic veins drain to the cavernous sinus with no valves (hence spread of infection from face)

• Layers of the eye
  • Bulbar conjunctiva continuous with the palpebral conjunctiva on posterior surface of eyelids
  • Episclera – Contains blood vessels that nourish the sclera
  • Sclera – Collagenous protective coating of eye, thinnest (and most prone to rupture) at rectus muscle insertion
  • Cornea – Attached to sclera at limbus
    • Epithelium (5-6 cell layers thick)
    • Bowman layer
    • Stroma
    • Descemet membrane
    • Endothelium
  • Uveal tract
    • Iris, ciliary body and choroid (vascular pigmented layer of eye between sclera and retina)
    • Supplies nutrition to eye and assists in accommodation and pupil constriction
  • Lens separates aqueous humor in anterior chamber from vitreous humor in posterior part
  • Retina
    • Sheet of neural tissue containing rods and cones lining posterior 2/3 of inner surface of globe extending anteriorly to the ciliary body

History

• Sudden, painless, monocular vision loss with AF or carotid stenosis = central retinal artery occlusion
• Characterise discomfort as pain (aching, burning, throbbing), pruritis or foreign body sensation
• Flashing lights or veil suggest retinal detachment
• Document tetanus status and boost accordingly
• PMHx
  • Contact lenses risk bacterial corneal ulcers
  • Chronic ophthalmic medications can cause chemical conjunctivitis or inflammatory corneal changes
  • Diabetes or chronic hypertension with acute isolated 6^th nerve palsy (Abducens – lateral rectus palsy) suggests ischaemic cranial neuropathy
  • Monocular diplopia if artificial lens suggests lens dislocation

Examination

• VA with/without glasses +- pinhole (18G needle through card)
  • VA is determined by smallest line in which half of letters correct
  • If <20/200, figure counting at 1m, perception of hand motion at 1-2 ft or light perception can be used
• Confrontational visual fields
• EOM
• Pupillary reactions
• Lids and adnexa
• Conjunctiva and sclerae
• Cornea
• Anterior chamber
• Iris
• Lenses
• Vitreous
• IOP
• Fundoscopy

• Involuntary horizontal nystagmus (optokinetic nystagmus)
  • If thick black and white horizontal lines 1 inch apart are moved side to side in patients vision, cannot help but have horizontal nystagmus
  • Presence of this excludes blindness (hysterical blindness test)
  • Use thick black horizontal lines 1 inch apart on cardiac monitoring paper held 1ft from patient
• EOM
  • CN III – All others
  • CN IV – Superior oblique
  • CN VI – Abducens – Lateral rectus

• EOM impaired by restricted movements e.g. Graves, entrapment, myositis
• CN palsy can be due to stroke, myaesthenia gravis, HTN, tumors, aneurysms, infections and trauma
• Resolution of diplopia with covering of one eye suggests pathology of EOM or its innervation
• Dominant movements by each muscle
  • Up and out – Superior rectus
  • Down and out – Inferior rectus
  • Lateral – Lateral rectus
  • Medial – Medial rectus
  • Up and in – Inferior oblique
  • Down and in – Superior oblique

• CN III palsy – Classic down and out position with partial ptosis and mydriasis (pupil dilatation) as carries parasympathetic fibres to pupil
• CN IV palsy – Failure to move eye in and down
• CN VI palsy – Failure to move eye laterally

• Pupillary testing
  • Size, shape and reaction to light
  • Teardrop if acute blunt or penetrating trauma with rupture of iris
  • Traumatic mydriasis
  • Assess under dim light for RAPD (Marcus-Gunn pupil)
    • Equal in size before testing and then both constrict equally, light swung to other eye and affected eye will dilate (due to impaired light penetration to CNS for any reason)
    • Will not cause resting anisocoria
• Anisocoria
  • Physiological anisocoria is defined as <1mm difference maintained throughout constriction/dilatation
  • Serious causes to consider include oculomotor nerve palsy, Horner syndrome, iris ischaemia, brain herniation and stroke
  • Drug-related anisocoria can arise from inhaled anticholinergics or topical sympathomimetics/anticholinergics
  • Can be due to abnormal miosis of one pupil or mydriasis of the other
  • Anisocoria which is more pronounced in darkness suggests a fixed miotic pupil due to inhibition of dilatation
  • Anisocoria more pronounced in light conditions suggests mydriasis due to inhibition of constriction
  • Tonic pupil (Adie’s tonic) presents with unilateral mydriasis and reduced light reflexivity but preserved (and often exaggerated) tonic pupillary constriction with accommodation

• RAPD
  • Specific for anterior afferent visual pathway as get equal pupils at rest indicating intact efferent pathway and consensual light reflex
  • Do not put down to the presence of a cataract

• Slit lamp
  • Straight ahead
  • Adjust vertical beam of light to full height of the cornea with width of 1mm
  • Examine conjunctivae for follicles (allergic and viral conjunctivitis), chemosis (subconjunctival fluid oedema), injection, discharge, trauma and foreign bodies
  • To examine cornea, rotate light source 45 degrees and look in layers
    • Inspect epithelium for abrasions, ulcers, oedema and foreign bodies
    • Examine stroma for oedema, scars, lacerations
    • Examine endothelium for precipitates (WCC on endothelium = iritis) and lacerations
• Assess depth of anterior chamber with lateral penlight shadowing if shallow

• Corneal stromal scar

• Corneal endothelium precipitates

• Assess anterior chamber
  • Shorten slit lamp beam to 1mm height and shut off room lights
  • Select high magnification swing
  • Move focus inward halfway between iris and cornea with pupillary aperture as black backdrop
  • Snowflakes will be visible = Cells
  • Flare looks light headlights through fog through aqueous humor and suggests increased aqueous protein characteristic for iritis
  • Check for hyphaema and hypopyon
• Assess iris for pupillary irregularity
• Assess lens for opacification, lacerations or subluxation

• Fluorescein
  • Wood’s lamp or cobalt-blue filter will fluoresce green
  • Always remove contact lenses as will permanently stain them
  • Seidel and corneal ulcerations/abrasions
• Fundoscopic examination
  • One drop of 1% tropicamide for Caucasian patients and this + 2.5% phenylephrine for all others
  • Size, shapre and sharpness of optic disc and borders
  • Cup:disc ratio (should be 0.3-0.5)
  • Size ratio of arteries to veins (2:3)
  • Nicking of arteries and veins (HTN)
  • Texture and colour of retina or vessels
  • Colour and size of macula
  • Measure any lesions in optic disc widths

• PanOptic
  • Focus on something 10 feet away with light off
  • Turn on, set to green line and adjust to maximum brightness
  • Maximum view when eye cup compressed by 50%

Cup:disc ratio

• Normal <0.3
• >0.5 = Glaucoma

Isolated dilated pupil

• DDx
  • Traumatic mydriasis
  • Contralateral Horner’s
  • Adie’s tonic pupil
  • Acute glaucoma
  • Pharmacological
  • Isolated third nerve palsy (rare)

Adie’s tonic pupil

• Kind of the opposite to Horner’s
• Isolated parasympathetic palsy after the ciliary ganglion with unilateral dilated pupil
• 70% of patients are female
• Affects accommodation so get intact distant vision with poor near vision
• 50% recover at 2 years

Isolated 3^rd nerve palsy

• Pupil involvement suggests compressive PCA or basilar tip aneurysm (need urgent imaging)
  • Parasympathetic fibres run on periphery of nerve
• Pupil sparing suggests intrinsic vascular pathology (HTN, diabetic) as vessels run on outside of nerve and central neurons are most at risk of ischaemia

Papilloedema

• Swollen optic disc
• Raised ICP of any cause (takes time to develop though)
• Usually bilateral (unilateral extremely rare)
• Signs
  • Venous engorgement
  • Loss of venous pulsation
  • Haemorrhages over and/or adjacent to optic disc
  • Blurring of optic disc margins
  • Elevation of optic disc
  • Paton’s lines (radial retinal lines cascading from optic disc)

Last Updated on June 1, 2023 by Andrew Crofton