How to use an Ophthalmoscope

Being able to use an ophthalmoscope confidently is very important to junior doctors, especially when identifying eye emergencies. In this article, we will go through the steps of eye examination using an ophthalmoscope.

When is ophthalmoscopy used?

In clinical practice, ophthalmoscopy is commonly performed for posterior segment diseases affecting the vitreous, macula, retina or optic nerve. Potentially, ophthalmoscopy could also be used to examine the anterior segment by adjusting the dioptre to +10D to provide a magnified view. Nonetheless, anterior segment diseases are usually examined using slit-lamp, or simply a pen touch and blue light (using an ophthalmoscope or slit-lamp).

Here are some examples of posterior segment diseases:

  • Vitreous – Vitreous haemorrhage, posterior vitreous detachment, retinal detachment
  • Optic nerve – Open-angle glaucoma, optic nerve swelling/papilloedema
  • Macula – Age-related macular degeneration
  • Retina – Central retinal artery occlusion, central retinal vein occlusion, hypertensive retinopathy, diabetic retinopathy

History

Asking the following questions in history taking can support your ophthalmoscopic findings when diagnosing posterior segment diseases.

  • Any sudden onset painless loss of vision?
    • This is more suggestive of the aforementioned acute posterior segment diseases.
    • Loss of vision accompanied by pain is usually caused by anterior segment, periorbital or orbital pathologies.
  • Is the loss of vision permanent or transient?
    • Permanent loss of vision is suggestive of structural disease (e.g. retinal detachment).
    • Transient loss of vision indicates underlying vascular insufficiency or neurological problem (e.g. transient ischaemic attack, migraine or raised intracranial pressure).
  • Any sudden painless loss of vision associated with trauma to the eye?
    • Trauma can cause vitreous haemorrhage or retinal detachment, which can lead to loss of vision.
  • Any sudden onset flashes or floaters?
    • Usually associated with posterior vitreous detachment and more importantly retinal detachment.
  • Any curtain like visual field defect?
    • Usually caused by retinal detachment.
  • Any slow progressive peripheral visual field loss (tunnel vision)?
    • This is suggestive of open-angle glaucoma.
  • Any sudden greying of the vision for a few seconds, or known as transient visual obscuration (TVO)?
    • This is associated with raised intracranial pressure.
  • Any symptoms associated with raised intracranial pressure?
    • E.g. nausea, vomiting, headache, symptoms worse on waking/coughing/bending, pulsatile tinnitus.
  • Any similar episodes in the past?
    • When, how often, to what extent, etc.

Instrument parts

Aperture settings

There are usually 8 different aperture settings that can be used for different examination purposes.

  • Small-light – Used pupils are very constricted in a well-lit room, reduces corneal glare
  • Medium-light – Used in pupils are not dilated in a dark room
  • Large-light – Used when dilating drops are administered, gives a wider field
  • Half-light – Used when visual axis is partially obscured by pathology, e.g. cataracts or lesion, therefore light can pass through the clear portion of the pupil without causing any reflection
  • Red-free light – Green light, used when examining vasculature, retina would appear in black and white
  • Blue light – Used after fluorescein staining to inspect for any corneal dryness, abrasion or ulcer
  • Slit beam – Used when inspecting for any contour abnormalities on cornea, lens and retina 
  • Grid – Used when estimating the distance between lesions
Dioptre settings

The ophthalmoscope has a carousel of lenses with different dioptre, ranging from +10 to -10. Positive dioptre values (1-10) are displayed in green/black on the dioptre indicator, and negative dioptre values (1-10) are displayed in red.

A more positive value means the viewing lens is more convex, so the focus point will be focused closer to the examiner’s eye. Therefore, when examining patients with hypermetropia, whose focal point is further away from the examiner’s eye, a more positive dioptre setting should be used.

On the other hand, a more negative value means the viewing lens is more concave, so the focus point will be focused further away from the examiner’s eye. Therefore, when examining patients with myopia, whose focal point is closer to the examiner’s eye, a more negative dioptre setting should be used.

Prepare yourself & the patient

Begin your examination by explaining the procedure to the patient, remember to warn the patient that the bright light may dazzle them for a short period of time. If you and/or the patient wears eyeglasses, remove them. Have your patient sit down in a chair and instruct the patient to fixate on a distant target in front of them so that they don’t move their eyes during the examination.

Next, check whether your ophthalmoscope is working by turning it on and check if the light works. Gather all the drops you require for your examination (e.g. short-acting dilating drops, fluorescein dye).

If you decide to dilate the patient’s eye, which is preferred in order to be able to examine the fundus more clearly, dilating drops should be administered at least 15 minutes before performing ophthalmoscopy and after you have assessed patient’s visual acuity, field and pupillary light reflexes.

It is important to tell the patient that the drops may blur their vision and increase their sensitivity to bright lights, which can last up to 4 to 6 hours. Therefore, they should not drive or operate any heavy machines until they have regained their normal sight.

External inspection of the eye

Inspect the eye systematically, from anterior to posterior, using naked eye and pen torch prior to performing ophthalmoscopy.

  1. Eyelid – Inspect for lid positions, and lid margins for any lesions, redness, oedema and crusting.
  2. Eyelashes – Inspect for positions, any loss and inturning of eyelashes.
  3. Lacrimal apparatus – Inspect for bulges near the canaliculi, signs of infection or inflammation, redness, swelling, discharge, and lacrimal puncta eversion or stenosis.
  4. Conjunctiva – Inspect for any conjunctival (generalised dilated inflamed blood vessels) or circumciliary (dilated inflamed blood vessels around the limbus) injections in all positions of gaze, subconjunctival haemorrhage, chemosis (oedema), discharge, lesions and lacerations.
  5. Cornea – Inspect for lens transparency, curvature, and surface for any ulceration, abrasion and vascularisation.
  6. Anterior chamber – Inspect for any hyphaema (blood) and hypopyon (pus).
  7. Iris – Inspect for any irregularity, heterochromia, presence of nodules and blood vessels.
  8. Pupil – Inspect for pupil position, symmetry, size and shape.

Prepare to perform ophthalmoscopy

Dim the light in the room for examination. Select the appropriate aperture option for your examination according to your environment and patient’s pupil size. Reset the ophthalmoscope dioptre value to 0 (which is the baseline) using the focusing wheel, and gradually adjust the dial to correct patient’s and your refractive error, until you can focus on the patient clearly from a distance.

The dioptre (D) value should equate to the total amount of refractive error of the patient and you. For instance, if the patient’s refractive error is -4, then dial it to -4 lens. If the patient’s refractive error is -4 and yours is +4, then keep it at 0 D. When a patient does not know his/her refractive error, the viewing lens could be gradually adjusted to bring the image into focus.

It is best to examine the patient’s left eye with your left hand holding the ophthalmoscope against your left eye; vice versa. Rest your index finger of the examining hand on the focusing wheel so that you can adjust the dioptre value throughout the examination to change the focus.

Red reflex

Stand at one arm’s length, wedge the ophthalmoscope against your cheek with hand, direct the light on the patient’s eye 15° temporal from the patient’s line of sight to look for any red/orange reflection from the pupil. Any markedly reduced/absence of red reflex could be suggestive of corneal scarring, cataract or vitreous haemorrhage.

Re-assess the cornea, iris and anterior chamber

To complete the external examination of the eye, we will assess the cornea, iris and anterior chamber again but more closely using the ophthalmoscope (with the viewing lens dialled to +10 to act as a magnifier).

Warn the patient that you are going to move closer to them to examine their eye further. Following the red reflex until you are standing close to the patient (around 3-5cm from patient’s eye) and continue to maintain 15° temporal from the patient’s line of sight. With one hand holding the ophthalmoscope, gently place your other hand on their forehead with your thumb resting on the patient’s supraorbital ridge. Slowly adjust the dioptre dial again until you can focus clearly on the anterior chamber for further assessment.

When assessing the conjunctiva and the cornea for any dryness, dendrites, ulcers or abrasions, apply fluorescein dye (0.5% or 1%) to the eye for staining and use the blue light setting on the ophthalmoscope for examination.  

Picture showing corneal dendrites after fluorescein staining:

Picture showing corneal ulcer after fluorescein staining:

Assess the fundus

Adjust the focus of the ophthalmoscope again by further decreasing the dioptre dial towards 0 (or the total amount of refractive error of the patient and you). Begin by identifying the optic disc and assess its characteristics, commonly known as the 3 “Cs” (Colour, Contour, and Cup).

  • Colour: A normal disc should be creamy pink to orange as it is well-vascularised; paleness suggests atrophy.
  • Contour: It should be well demarcated and sharp; blurriness suggests optic disc swelling (unilateral) or papilloedema (bilateral and in the context of raised intracranial pressure).

Picture showing optic disc swelling:

  • Cup: This refers to the central paler part of the disc; assess the cup:disc ratio (CRD) by estimating the vertical height of the disc and the cup.
    • CDR normally is <0.3 but sometimes there could be a physiologically large cup.
    • Comparing the CDR between the two eyes could help distinguish a normal or a pathological cup (>0.2 difference in CDR between two eyes is suspicious of pathological changes such as glaucoma).

Next, examine the macula and the fovea by asking the patient to look directly into the light. The macula is an avascular dark disc situating temporally to the optic disc; the darker centre of the optic disc of the fovea. Inspect for any abnormalities, such as ‘cherry red spot’, drusen, exudate and haemorrhage.

Picture showing cherry red spot, attenuated blood vessels and pale retina, indicating central retinal artery occlusion (CRAO):

Picture showing drusen in the macula, which is a common finding in early age-related macular degeneration:

image 7
From AAFP

Finally, assess the vascular arcades and retina. Divide the retina into 4 quadrants according to the principle vessels, and examine in an anti-clockwise fashion as outlined below:

  1. Superior nasal
  2. Inferior nasal
  3. Inferior temporal
  4. Superior temporal

Examine each arcade and the background retina of respective quadrant carefully, starting from the optic disc to the peripheries. The background retina colour usually correlates with patient’s skin and hair colour, i.e. pale retina in patients with light skin and blonde hair, umber shade in patients with dark skin and black hair. You can ask the patient to look in different directions to extend your field of view.

  • Acute findings: vitreous haemorrhage, posterior vitreous detachment, retinal detachment, pale retina, embolus/infarct, tortuous veins.
  • Other findings: venous beading, arteriolar narrowing, arteriovenous nipping, copper/silver wiring, neovascularisation, hard/soft exudates, dot and blot/flame haemorrhage.

Picture showing vitreous haemorrhage:

Picture showing posterior vitreous detachment (Weiss’s ring in the vitreous cavity):

Picture showing retinal detachment:

Picture showing optic disc swelling, tortuous veins, cotton wool spots and retinal haemorrhage, indicating central retinal vein occlusion (CRVO):

Picture showing retinal changes related to diabetic and hypertensive retinopathy:

Repeat the assessment on the other eye.

Document your findings

Record your findings using diagrams. Fundic images are upright so draw your findings as you see them, i.e. patient’s right eye findings are usually documented on the left side of the medical notes.

References & Further Reading

Written by Dr Charlotte Ho (FY1)
Reviewed and edited by Mr Darren S J Ting (Post-CCT Clinical Research Fellow)
Uploaded by Aos Al-Hassani (Y3 Medical Student)

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