Fundus Examination for Optometrists: Normal Variants, Disc Assessment and DR Grading for Screening
Last updated: November 2026
RPC Rounds for Optometrists · B.Optom study guide
Optometrists are often the first to see a patient's fundus. Knowing what normal looks like, assessing the optic disc systematically and grading diabetic retinopathy for referral prevents blindness from glaucoma, diabetes and retinal detachment.
Ways to look at the fundus
| Method | Field and image | Best for |
|---|---|---|
| Direct ophthalmoscope | About 15× magnification, small field (about 5–10°), upright image | Disc and macula detail; quick screening through undilated pupils |
| Slit lamp with +90 D or +78 D lens | Stereoscopic, inverted, about 30–40° field | Disc assessment (cup and rim), macula, diabetic retinopathy |
| Binocular indirect ophthalmoscope with +20 D lens | Stereo, inverted, wide field (about 45°), about 3× | Peripheral retina: tears, detachment, lattice |
| Fundus photography and OCT | Records and measures | Monitoring, DR screening, glaucoma and macular disease |
Normal and normal variants
- Disc: vertically oval, about 1.5–1.8 mm; pink rim; cup-disc ratio commonly 0.3–0.4; small discs have small or no cups, large discs have large physiological cups.
- Variants that are not disease: myelinated nerve fibres, tilted disc, peripapillary atrophy in myopia, physiological cupping (symmetrical, large disc), choroidal naevus (flat, small, with drusen), tessellated (tigroid) fundus, CHRPE.
- Vessels: artery-to-vein ratio about 2:3; spontaneous venous pulsation is present in most normal eyes (its presence makes raised intracranial pressure unlikely).
Assessing the optic disc for glaucoma
- Estimate disc size (small, average, large).
- Check the neuroretinal rim: the ISNT rule (inferior thickest, then superior, nasal, temporal) usually holds; a thin or notched inferior or superior rim is suspicious.
- Estimate the vertical cup-disc ratio and compare eyes: asymmetry of 0.2 or more is suspicious.
- Look for disc haemorrhages (splinter haemorrhage at the disc margin), RNFL defects (best in red-free light), bayoneting and baring of vessels.
- Use a system such as DDLS, and record a drawing or photograph.
Diabetic retinopathy for screening (ICDR-based)
| Grade | Findings | Action |
|---|---|---|
| No apparent DR | No abnormalities | Re-screen in 1–2 years (yearly in most programmes) |
| Mild NPDR | Microaneurysms only | Re-screen in about 12 months |
| Moderate NPDR | More than microaneurysms but less than severe | Refer non-urgently; review within about 6 months |
| Severe NPDR | 4-2-1 rule: haemorrhages in 4 quadrants, venous beading in 2, or IRMA in 1 | Refer soon (weeks) |
| PDR | New vessels, vitreous or preretinal haemorrhage | Refer urgently |
| Diabetic macular oedema | Thickening or hard exudates near the centre of the macula | Refer; centre-involving DME needs prompt specialist care |
Refer urgently (same day) if you see
- Retinal tear or detachment, vitreous haemorrhage, new flashes and floaters with pigment in the vitreous (Shafer sign).
- Swollen optic discs (papilloedema) or a pale swollen disc in an older patient (giant cell arteritis).
- Central retinal artery occlusion (cherry-red spot), retinal vein occlusion with macular oedema, or proliferative diabetic retinopathy.
- A pigmented choroidal lesion with orange pigment, fluid or thickness (see naevus vs melanoma).
See also the optometrist referral guide.
Practical pearls
- Dilate whenever the view is poor, the patient is diabetic, has new floaters or flashes, or you cannot see the disc well enough to judge it.
- Compare the two discs side by side: asymmetry is often the first sign of glaucoma.
- A flat pigmented lesion in the fundus deserves a photograph today so it can be compared next time.
Where students slip
- Calling a large cup in a large disc glaucomatous, or missing a small cup in a small disc.
- Grading diabetic retinopathy without checking the macula for exudates.
- Relying on direct ophthalmoscopy alone for the peripheral retina in a patient with flashes.
Test yourself: flip cards
Quick quiz
Related: When to Refer: Eye Referral Urgency Guide for Optometrists, Diabetic Retinopathy: Classification and Management for Residents, Disc Damage Likelihood Scale (DDLS), Congenital Optic Disc Anomalies: Hypoplasia, Coloboma, Morning Glory, Optic Pit and More, Choroidal Naevus vs Melanoma: TFSOM-DIM Risk Factors, Imaging and When to Refer. Back to the optometry curriculum.
Key sources
- Wilkinson CP, et al. Proposed international clinical diabetic retinopathy and diabetic macular edema disease severity scales. Ophthalmology. 2003;110:1677-1682
- Jonas JB, et al. Ophthalmoscopic evaluation of the optic nerve head. Surv Ophthalmol. 1999;43:293-320
- College of Optometrists (UK). Guidance for professional practice: referral
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