Fundoscopy (Direct Ophthalmoscopy) Comprehensive Notes

Major Components
• A – Brow rest: stabilises examiner’s hand‐held position, keeps patient’s brow steady.
• B – Light-intensity dial / on–off switch: adjusts beam brightness; lower for photophobic patients, higher for media opacities.
• C – Lens dial: corrects combined refractive error of examiner + patient by rotating lenses of different dioptric powers.
• D – Lens-strength indicator
– Green numbers: plus lenses (hyperopia, $+$ diopters).
– Red numbers: minus lenses (myopia, $-$ diopters).
– Colour coding can vary between manufacturers.
• E – Opacity / fixation filter selector: helps focus on vessels or visualise through corneal/ lenticular haze.
• F – Red-free (green) filter: blocks red wavelengths; enhances contrast of retinal vessels ⇒ arteries vs. veins easier to distinguish, haemorrhages become dark.
• G – Cross-polarising filter: two linear polarisers at $90^\circ$ ; suppresses corneal surface glare, particularly useful with difficult reflexes.
• H – Aperture dial: chooses beam shape & size.
– Default: round, white, no cross-hairs.
– Small aperture: undilated pupils.
– Large aperture: dilated pupils.
– Special shapes (e.g. slit, grid) used after fluorescein, but rarely in routine medical ward work.
Optical Capability
• Field of view ≈ $6^\circ$ (about 1–2 disc diameters).
• Magnification ≈ $15\times$ ⇒ highly detailed but small area.

Hand–eye rule:
• Examine the patient’s right eye with your right eye & right hand.
• Examine the left eye with your left eye & left hand.
⇒ Maintains nose-to-nose alignment, avoids bumping foreheads.
Approach angle:
• Start ~ $20^\circ$ temporal to patient’s visual axis; this brings optic disc into view after you follow vessels nasally.
• Maintain same horizontal plane as the patient’s eye.
Free hand: rest thumb/ side-hand on patient’s brow or cheek ⇒ stabilises distance ≈ 2–4 cm.

Glasses: ask patient to remove; contact lenses may stay.
Explanation (key consent points):
• Need to come very close – “almost touch noses”.
• Light will be bright/ uncomfortable but not painful.
• Will place thumb on forehead for steadiness.
Optimal viewing conditions
• Darken room.
• Pharmacologic dilation if not contraindicated: $1\%$ tropicamide (antimuscarinic) – onset 15 min, lasts 4–6 h; contraindications include shallow anterior chamber/ narrow angles, pregnancy caution, driver advice.

Red Reflex
• Stand ~1 m away; shine light towards pupil.
• Normal: bright orange-red glow.
• Abnormal patterns:
– Obscured/ dull = cataract, corneal scar.
– White/yellow (leukocoria) = retinoblastoma, congenital cataract.
– Absent/ asymmetric = retinal detachment, large strabismus angle.
Fundus Visualisation
• Move in slowly, keep reflex centred until retina comes into focus (use lens dial for clarity).
• Identify major landmarks (see below).

Optic Disc (nasal) – creamy–pink oval with central depression (physiological cup).
Macula/ Fovea (temporal) – avascular, darker, centre of detailed vision; align patient’s gaze directly at light for foveal reflex.
Vascular arcades
• Supero-temporal, infero-temporal, supero-nasal, infero-nasal.
• Arteries narrower, lighter red; veins wider, darker.

Locate: follow a vessel towards where it thickens – usually leads to disc.
Disc margin clarity: blurred in papilloedema, optic neuritis.
• If focus cannot be achieved with multiple lens powers ⇒ consider true swelling rather than refractive blur.
Colour:
• Normal: salmon-pink.
• Pale/ white = optic atrophy (e.g. glaucoma, MS, ischaemic optic neuropathy).
Cup–to–Disc Ratio (CDR)
• Normal ≈ $0.3$ (cup ≈ one-third disc).
• Pathological if >0.5 or asymmetry >0.2 between eyes ⇒ suggests glaucomatous neural loss.

Arterial Changes
• "Silver wiring": broad, reflexive, opaque wall – longstanding hypertension.
• Arterio-venous (AV) nipping: thick artery compresses underlying vein – hypertension.
Venous Changes
• Tortuosity: chronic hyper-glycaemia/ pregnancy.
• Beading, looping: proliferative diabetic retinopathy.
• Neovascularisation (irregular fine vessels) on disc or elsewhere: ischaemic drive (PDR, CRVO).

Haemorrhages
• "Flame-shaped" (NFL layer) – acute hypertension, papilloedema.
• "Dot-blot" (inner nuclear/ outer plexiform layers) – diabetes.
Hard Exudates: lipid residues, yellow with sharp edges – diabetes, HTN.
Soft Exudates (cotton-wool spots): micro-infarcts of NFL – diabetes, HTN, anaemia.
Pigment Changes
• Hyper-pigmentation & bone-spicule pattern – retinitis pigmentosa (RP).
• Hypo-pigmented laser scars – post-photocoagulation therapy (diabetes, retinal holes).

Ask patient to look directly at the light; you’ll briefly see foveal reflection.
Key signs
• Macular oedema: loss of foveal pit, thickening, rings of exudate.
• Drusen: yellow sub-RPE deposits – hallmark of age-related macular degeneration (AMD).
• Pigmentary change: early AMD, medication toxicity (chloroquine).

Hypertension: generalised arteriolar narrowing → silver wiring → AV nipping → haemorrhages/ exudates → papilloedema (Malignant HTN). Fundoscopy offers a non-invasive "window" to systemic vasculature.
Diabetes Mellitus: microaneurysms & dot-blot haemorrhages precede proliferative neovascularisation; timely detection allows laser or anti-VEGF therapy, preventing blindness.
Glaucoma: elevated CDR, bayoneting vessels, disc haemorrhages; optic disc analysis complements tonometry & visual fields.
Neurology: Papilloedema indicates raised intracranial pressure; optic pallor suggests optic neuropathy; retinal emboli may reveal carotid disease.
Paediatrics: Leukocoria differential (retinoblastoma vs. congenital cataract) is life-saving.

Patient dignity & comfort: warn of proximity, offer tissue if lacrimation occurs.
Pharmacologic dilation: discuss transient blurring/ photophobia; document consent; advise against driving until vision clears.
Infection control: disinfect brow rest & lens after each patient; avoid direct contact with lashes.
Equity of access: portable, inexpensive ophthalmoscopes enable screening in low-resource settings, bridging ophthalmic care disparities.

Cannot obtain red reflex: check lens dial set to $0$ dioptres, dim lights further, move slightly off-axis.
Media opacity suspected: use opacity filter setting (E), increase light intensity, attempt different angles.
Small pupil: select smaller aperture, consider pharmacologic dilation unless contraindicated.
Myopic patient – blurry view: dial in minus lenses (red numbers) roughly equal to refractive error.
Hyperopic patient: dial plus (green) lenses.