fundoscopy

see also:

• ophthalmology
• American Academy of Ophthalmology's EyeWiki

• fundoscopy can provide important clinical information for many emergency presentations as well as for detection of severity of chronic disease such as hypertension, diabetes, etc, however, it remains under-utilized in the ED for various reasons such as:
  • inexperience of clinicians and lack of confidence in interpretation of findings
  • time factors
  • concerns over use of pupillary dilation drops and their potential adverse effects:
    • precipitation of glaucoma in those who are susceptible
    • blurred vision and inability to drive home from ED
    • impaired neurological exam assessment due to dilated pupils
  • lack of easy to use equipment
  • unlikely to change management eg. if suspect SAH, a CT brain +/- LP will probably be ordered irrespective of fundoscopy findings
  • NB. tearful patients cannot be dilated as they wash the drops out

• acute visual loss or disturbance
• some patients with headache where raised intracranial pressure and possible papilloedema is suspected, or possible optic neuritis as in suspected temporal arteritis

• summarised from https://www.ncbi.nlm.nih.gov/books/NBK221/
• nomenclature:
  • the term temporal is used in describing ophthalmoscopic landmarks and findings, rather than “lateral”; and nasal replaces “medial.”
  • the optical axis is the patient's line of sight, “straight ahead”
  • the background retina is all the retina that is not disk, vessels, or macula
  • estimates of distances are usually described in terms of transverse diameter of the optic disk
• optic disk (the optic nerve head)
  • seen when one looks through the pupil from an angle about 15 degrees temporal to the optical axis
  • normally is sharply demarcated temporally and to a lesser degree nasally and is slightly taller than wide with a paler central optic cup which occupies less than a third of the disk (the cup is enlarged in glaucoma and in high myopia)
  • papilloedema
    • swollen optic nerve-head usually reflecting elevated intracranial pressure HOWEVER visible retinal venous pulsations exclude increased intracranial pressure
  • optic disk pallor / optic atrophy or neuropathy
    • may be due to:¹⁾
      • damage within the eye such as glaucoma, optic neuritis, papilloedema
      • damage along the path of the optic nerve to the brain (tumour, neurodegenerative disorder, trauma, etc)
      • congenital (Leber’s hereditary optic atrophy, autosomal dominant optic atrophy)
• the central retinal artery and vein
  • emerge from the optic nerve and each soon bifurcates into superior and inferior branches
  • each large vessel divides into a nasal and a temporal branch hence there are superior temporal, inferior temporal, inferior nasal, and superior nasal branches
  • the artery/arteriole appears slightly smaller, and distinctly lighter, more orange-red and less purple than the vein/venule
  • the largest veins pulsate slightly and the arteries do not, the reverse of the situation elsewhere in the body
  • complete AV (arterio-venous) crossing change
    • apparent complete obliteration of venous blood columns where they cross arteries more than two disk diameters away from the disk
    • may be due to chronic hypertensive damage even if normotensive, a primary heart muscle disorder or dilated cardiomyopathy
  • Hollenhontplaques
    • embolic atheroma causing occlusion of an arteriolar branch with yellow and refractile plaque visible - usually arise from the aortic arch or a carotid artery
  • tortuous “sausage-link-like” retinal veins
    • may be due to marked hyperviscosity
• the macula
  • this is the area of greatest visual acuuity and is seen as a avascular, dusky area two disk diameters temporal to the disk
• the retinal background
  • the background retinal color will parallel the patient's skin and hair pigmentation, from pale in light-skinned blondes to an umber shade in the darkest black people
  • any yellow, yellow-white, gray, or black interruptions of the background retinal color pattern suggest pathologic exudate, oedema, or scar
    • grayish loss of transparency with local elevation
      • suggests acute retinal oedema
    • “hard, waxy exudate”
      • sharp-edged discoloration in any of a variety of shades of yellow due to lipoprotein deposition resulting from chronic oedema due to either increased permeability (eg. retinitis) and/or increased venous plasma hydrostatic pressure
      • loss of pericytes allows leakage in diabetic vasculopathy
    • “soft exudates, also known as cottonwool spots”
      • gray-white to gray-yellow and show indistinct margins and usually represent infarction of the nerve fiber layer, often due to vasculitides and also commonly occur in AIDS
    • “crumbled cheese and ketchup appearance”
      • suggests CMV infection in patients with AIDS
  • retinal haemorrhages occur in diverse conditions including severe accelerated hypertension, infective endocarditis (including SBE), pernicious anaemia, diabetes, leukemia, subarachnoid haemorrhage (SAH), and disseminated intravascular coagulation (DIC)
  • proliferative diabetic retinopathy

• record baseline pupillary reactions and size
• instill one drop of 1 % (or ½%) tropicamide in each conjunctival sac and instruct patient to keep eyes closed for 5 minutes to ensure maximum contact
• by 30-45 minutes pupils should be dilated and non-reactive
• a failure to regain accommodation within 2 hours or development of eye pain or headache that day consider checking intra-ocular pressures as it may have unmasked glaucoma
• patient should not drive for next 6hrs as mydriasis and paralyzed accommodation create road hazard even with strong sunglasses and even at night
• for inpatients ensure staff are aware that pupils have been dilated to avoid staff panicking with neuro obs

• this is the traditional approach and is the most readily available option in ED and in GP practices
• usually requires dilation of pupils for a reasonable view
  • an ophthalmologist is unlikely to attempt direct ophthalmoscopy without pupillary dilatation
• lower the room lights and remove your and the patient's eyeglasses, but not contact lenses
• show the patient a spot directly ahead on which to fix their gaze
• hold the instrument with the hand ipsilateral to the examining eye
  • use your left eye and left hand to hold the ophthalmoscope for the left fundus and use your right eye and right hand for the right fundus
• forefinger turns the horizontal rheostat and the vertical lens wheel
  • lenses have red numbers for negative diopter values (progressively more distant focusing with higher numbers), black numbers are positive
  • the larger light beam option illuminates a wider field, but the smaller beam option decreases corneal glare
• hold the instrument against your bony orbit, with the bumper ridge against your forehead
• keep your other eye open
• use the lowest light intensity which allows visibility - usually 2/3rds of maximum
• start with your eye 30cm from the patient and at 15deg from their optical axis, set your lens wheel at + 10 diopters and trans-illuminate the pupil and observe reflected red light, the red reflex
• place your contralateral palm on their forehead, with your abducted thumb on their supraorbital ridge, to prevent accidentally bumping brow or eye with the instrument
• slowly move toward the patient, slowly decreasing your diopters toward zero (increasing your focal length) - this will allow you to focus successively on cornea, lens, vitreous, and finally retina at which point you should be 3-5cm from their eye
• adjust focus on a prominent retinal feature as needed:
  • myopic examiners need a negative or red number (unless the patient's refractive error balances the examiner's)
  • aphakic patients require a high positive, often + 10
• for vision of the whole fundus, turn your head and crane your neck, while maintaining a constant relationship between your eye, your hand, and the instrument.
  • a viewing aperture moved 1 mm out of your optical axis can mean loss of half the available field, so make the spatial relations as constant
  • use a consistent approach such as following a vessel to the optic disk, assess it, then move out along the superior temporal artery to the periphery, return to the disk by way of the vein and then repeat for the other quadrants
• total inability to visualize the retina usually means an intervening opacity, commonly a cataract or a vitreous haemorrhage
• inability to visualise retina due to white beam reflection from the cornea can be helped by using a smaller and lower intensity beam and changing your angle

• Welch Allyn Panoptic Ophthalmoscope
  • uses a patented Axial PointSource™ Optics which makes it easier to view through undilated pupils
  • 5X larger view of the fundus vs standard ophthalmoscopes in an undilated eye
  • greater working distance improves comfort for both clinician and patient
  • dynamic focusing wheel allows continuous, smooth action and more precise control
  • aperture filters include Large Spot, Fixation, Red-free, Slit, Cobalt Blue, and Small Spot

• uses an indirect ophthalmoscope, an instrument that has a light attached to a headband, in addition to a small handheld lens
• provides a wider view of the inside of the eye and allows a better view of the fundus of the eye, even if the lens is clouded by cataracts

• similar concept to indirect ophthalmoscopy but using a slit lamp

• patient places face onto camera and follows instructions
• high quality retinal images can be obtained even without dilating pupils
• some have AI analysis built in to detect certain features such as papilloedema