the eye examination / slit lamp exam

see also:

• ophthalmology
• chemical injuries and burns to the eyes
• welder flash burns - UV keratopathy (photo keratitis)
• Eye injuries
• the eye

• the ability to perform a good eye examination is an important skill for most doctors

• wash hands BEFORE and AFTER touching patient's skin and consider wearing gloves
• detailed relevant history
• brief initial examination of face and the eye to ascertain any obvious pathologies
  • eg. trauma, zoster, HSV skin rash, conjunctivitis, etc.
  • a zoster lesion on tip of nose indicates naso-ciliary nerve involvement and probable ocular involvement
• visual acuity in both eyes
  • usually with patient's usual glasses if they have them
  • patient ideally should be 6m from a reference chart and cover one eye and read out the smallest symbols and that line becomes their acuity score for that eye
    • repeat with other eye
    • record eg. if can read only down to 9m symbols with right eye but could not read two of them with their usual glasses on then this would be R: 6/9-2 (with glasses)
    • if poor performance, consider a pinhole test to exclude refractive errors as the cause
• examine eye under normal light using a slit lamp if available
  • if severely photophobic then apply local anaesthetic drops and try again when settled
  • adjust size of the slit and its orientation to your needs
  • is there chemosis of the sclera, if so is there a pattern to it or is it generalised
    • if pattern is circumferential around the cornea, then it may be episcleritis
    • if it is generalised, there are many causes including glaucoma, conjunctivitis, etc
  • is the pupil reactive
    • a fixed dilated pupil in a painful red eye suggests acute glaucoma
  • is the pupil distorted
    • this suggests penetrating eye injury if new
  • does the lens appear clear
    • it may have cataracts or it may have been injured in a penetrating injury
  • is the anterior chamber normal
    • is there a hyphaema from blunt trauma
    • is there a cloudiness to it suggesting possible uveitis
      • tip: use a narrow slit off-axis in various positions to assess the anterior chamber and cornea
  • now examine the cornea carefully
    • is there a corneal foreign body or a residual rust ring / ulcer from a foreign body that is no longer there
    • are there any obvious pathologies
• if no significant pathology found, consider using flourescein staining and examine with the cobalt-blue light in a darkened room:
  • this will be very sensitive for detecting corneal pathology such as:
    • vertical scratches - these generally indicate a subtarsal foreign body which may still be there
    • corneal foreign body
    • ulcer from a corneal body or superficial trauma
    • other corneal ulcers such as dendritic herpetic ulcers
    • a single linear ulcer suggests a scratch such as from a fingernail or a tree branch
    • evidence of a punctate keratitis
      • if the upper third and lower third are spared, this suggests an exposure keratitis from welding, other UV, or inadequate blinking
      • a more generalised keratitis could indicate other causes such as viral, chemical, contact lens issue, etc
• evert upper eyelid if Hx or exam suggests a subtarsal foreign body
  • most common technique:
    • stand behind patient with a good light source above you and directed onto patient's eye
    • ensure you are wearing the correct glasses for this distance if you need glasses
    • ask patient to look down
    • grab the patient's eye lashes and with a horizontal cotton bud pressed firmly against the upper part of the upper eyelid (above the tarsal plate), lift the eyelashes upwards and hopefully the eyelid and its tarsal plate will evert over the cotton bud
  • the Gary AYTON technique for patients with minimal eyelashes which are impossible to grab onto:
    • apply a small length of 5-10mm wide Transpore tape across the bottom half of patient's upper eyelid then use this to hopefully lift the eyelid over the cotton bud as above
  • sweep with a moist cotton bud and inspect with a magnifying glass
• perform tonometry if available to help exclude penetrating eye injury (pressure may be low) or glaucoma (pressure will be high)
• assess extra-ocular muscle movements
  • painful movements may suggest a retro-orbital condition such as orbital cellulitis, etc
• further specific examinations pending suspected pathology
  • ocular pH if suspect chemical burn - this will need immediate and prolonged eye irrigation until pH normalises
  • visual fields if concern is of visual impairment and possible neurologic cause
  • fundoscopy or retinal camera¹⁾
    • classic direct ophthalmoscope
      • in patients with normal vision, the classic direct ophthalmoscope provides a view of approximately two-disc diameters, equating to about 7mm² of the retina. This view becomes even smaller in patients with high myopia. The average human retina has a surface area of 1204 mm², a clinician would need to examine 172 fields systematically to visualise the entire retina and ensure no significant lesions (up to two disc diameters in size) are missed²⁾
      • even when used by ophthalmologists on patients with pharmacologically dilated pupils, direct ophthalmoscopes show limited sensitivity for detecting common conditions such as hypertensive retinopathy
    • PanOptic direct ophthalmoscope
      • provides a wider field of view (25 degrees), offers an extended working distance and superior optic disc assessment and option of smartphone photography
    • stereoscopic digital fundal cameras
      • have much broader fields of view of 45 degrees
      • pseudo-colour imaging (e.g., multicolour or scanning laser ophthalmoscopy) utilises reflectance at multiple wavelengths (e.g., blue, green, infrared) to construct composite images which enhance contrast and depth resolution across specific retinal layers and is particularly sensitive to subtle structural changes, such as retinal nerve fibre layer defects, cotton-wool spots, vessel sheathing, and early macular pathology but makes the optic nerve appearance interpretation very challenging
      • the integration of automation features, such as auto-focus, auto-alignment, and auto-capture, easy to understand and operate, has further improved usability for non-specialists
      • most modern systems are Digital Imaging and Communications in Medicine (DICOM) compatible which allow incorporation into EMR systems
      • allows non-mydriatic fundus photography (NMFP)
      • some advanced models can offer widefield imaging, autofluorescence imaging, and anterior segment visualisation.
      • optical coherence tomography (OCT) is a non-invasive, high-resolution imaging technique that provides cross-sectional images of the retina
        • the advent of OCT angiography further expanded its utility by enabling dye-free visualization of retinal microvasculature
        • emergency physicians using OCT achieved 69% sensitivity for any abnormality, 100% sensitivity for urgent conditions, and 64% specificity overall, while providers using standard ophthalmoscopy detected no abnormalities³⁾
      • combined OCT–fundus photography systems are now also available
      • table top models perform better than hand held portable models
      • recent miniaturisation of optical systems has enabled the development of compact, portable, and cost-effective devices that could be used in the ED
    • indirect binocular ophthalmoscope
      • the gold standard for fundoscopy and will give better 3D vision to better appreciate cotton wool spots etc than a 2D photograph
  • diagnostic ocular ultrasound POCUS
    • can be used to detect RD, ocular trauma, CRAO, intraocular foreign bodies, vitreous haemorrhage and by measurement of the optic nerve sheath diameter, estimate intracranial pressure
    • however, many of the ultrasound machines used in the ED provide suboptimal imaging of the ocular contents, especially in the hands of ED providers who often do not have the necessary expertise
  • CT orbits if concern for retro-orbital pathology or blow-out fracture entrapping an extra-ocular muscle
• urgent referral to ophthalmology if red flags such as
  • acute vision loss not explained by tears, corneal pathology or visual cortex stroke
  • penetrating eye injury
  • acute glaucoma
  • intra-ocular haemorrhage (except subconjunctival haemorrhage alone which is usually benign)
  • papilloedema
  • concern of retro-orbital pathology
  • history suggestive of retinal detachment
  • unexplained unilateral red eye
  • possible HSV or zoster involvement of the eye