Fundoscopy and Fundus Photography
Fundoscopy (ophthalmoscopy) is the direct examination of the back of the eye: the optic disc, retina, macula, retinal vessels and, with a wide field, the periphery. It shows disease of the eye and signs of systemic conditions (hypertension, diabetes, raised intracranial pressure, infection, and inflammation) in a way that no other part of the body allows. Fundus photography records the findings as an image.
Several methods are used. Direct ophthalmoscopy with a hand held instrument gives an upright, magnified (about 15 times) view of a small area (about 5 to 10 degrees), without need for dilation in a darkened room.
Indirect ophthalmoscopy with a head mounted light and a hand held condensing lens (20 or 28 dioptres) gives a wide field (up to 40 to 50 degrees), a stereoscopic view, and an inverted image, and is the method for the peripheral retina. The slit lamp with a 78 or 90 dioptre lens or a contact lens gives a highly magnified stereoscopic view of the optic nerve and macula.
Fundus photography uses a camera (mydriatic or non-mydriatic) to capture colour images of the retina at 30 to 50 degrees, and wide field and scanning laser cameras capture up to 200 degrees. Smartphone based and hand held cameras are low cost options.
The examination takes 5 to 15 minutes. Dilating drops (tropicamide, with or without phenylephrine) give a wider view and are used for a complete retinal examination. Photographic screening of diabetic eye disease detects sight threatening retinopathy with a sensitivity of about 80 to 95%, and is used in national programmes. Direct ophthalmoscopy by non-specialists is less sensitive, at about 50 to 60% for diabetic changes.
Indications.
- Diabetes: screening and monitoring for retinopathy and maculopathy.
- Hypertension and cardiovascular disease: retinopathy, arteriolar changes, retinal vein and artery occlusion.
- Headache, visual symptoms, and suspected raised intracranial pressure (papilloedema), optic neuritis, or optic atrophy.
- Sudden visual loss, flashes, floaters or a curtain over vision: retinal tears and detachment, vitreous haemorrhage.
- Glaucoma assessment of the optic disc (cup-to-disc ratio, rim loss, haemorrhages).
- Macular disease, retinal dystrophies, and infections (cytomegalovirus retinitis, toxoplasmosis, tuberculosis, syphilis).
- Neonatal screening for retinopathy of prematurity, and red reflex testing in newborns for leukocoria.
- Systemic diseases: sickle cell disease, endocarditis (Roth spots), HIV, and malaria (malarial retinopathy in cerebral malaria).
- Drug toxicity (hydroxychloroquine, ethambutol, vigabatrin) monitoring.
Not applicable when the view is blocked by dense media opacity (dense cataract, vitreous haemorrhage), when ultrasound is used instead.
Contraindications and precautions.
- Dilation is avoided in patients with narrow angles or a history of angle closure, until the angle is assessed, and in those who need neurological pupil monitoring (head injury, stroke, raised intracranial pressure). The undilated view is used, or dilation is done after consultation and documentation.
- Patients are warned about blurred vision and light sensitivity for 4 to 6 hours, and not to drive until it clears.
- Allergy to dilating drops. Systemic effects in infants (phenylephrine).
- A suspected open globe injury: no pressure on the eye, no indentation.
- Photosensitive epilepsy and migraine: bright flashes may provoke symptoms.
- Infection control: instruments are cleaned between patients.
Preparation and technique.
Visual acuity and pupil responses are checked, then dilating drops are given, with 15 to 30 minutes for full effect. In direct ophthalmoscopy, the room is darkened, and the examiner uses the right eye for the patient's right eye and the left for the left, starting at about 15 cm from the patient with the red reflex, then moves close to view the disc.
The disc, cup, vessels, then the four quadrants of the retina and the macula, which is found by asking the patient to look at the light, are examined. In indirect ophthalmoscopy the patient lies back, and the periphery is viewed with scleral indentation as needed.
For photography, the patient looks at a fixation target and the camera captures disc centred and macula centred images in each eye, with at least two fields for diabetic screening.
