Anterior Segment Eye OSCE Examination

Contents

1. Introduction
2. General Inspection
3. Eyelids and Lashes
4. Conjunctiva and Sclera
5. Cornea
6. Anterior Chamber
7. Iris and Pupils
8. Lens
9. Eyelid Eversion
10. Completing the Examination
11. Quiz

Introduction

Wash your hands and don personal protective equipment if appropriate. This examination involves close contact with the patient's face and eyes, so good hand hygiene is essential to avoid transmitting infection between eyes or between patients.

Introduce yourself to the patient and ensure to mention your grade e.g. 3rd year medical student/junior doctor/consultant.

Confirm the patient's details taking 3 points of identification usually; full name, date of birth and NHS/hospital number.

Obtain consent for the examination, explaining what it will entail. Warn the patient that you may need to shine a bright light into their eyes, that this may be a little uncomfortable, and that you may need to gently touch their eyelids.

Ask about pain and any visual symptoms before you begin, and ask whether the patient wears glasses or contact lenses. Contact lens wear is an important risk factor for microbial keratitis.

Gather your equipment: a pen torch, a source of magnification (a slit lamp is ideal, but a direct ophthalmoscope set to around +10 dioptres, an Arclight ophthalmoscope or a magnifying loupe all work at the bedside), fluorescein drops and a cobalt blue light, topical anaesthetic drops if eversion is anticipated, and cotton buds. It is good practice to assess visual acuity with a Snellen chart first, as acuity is the single most important measure of visual function and provides essential context for any anterior segment findings.

Position the patient sitting comfortably, ideally on a chair at the slit lamp, or upright facing you with adequate lighting. Examine in a sequence and remember to assess both eyes for comparison, as many signs are only obvious when one eye is set against the other.

General Inspection

Begin by standing back and observing the patient and the area around them. Note whether they appear comfortable or distressed, and whether they are protecting the eye, holding it shut or shielding it from the light.

Look for photophobia (an aversion to light), which is a feature of anterior uveitis, keratitis and corneal abrasion, as light causes painful movement and spasm of the inflamed iris and ciliary body. Note any watering (epiphora) or discharge: watery discharge suggests a viral or allergic cause, whereas purulent (yellow-green) discharge suggests bacterial conjunctivitis.

Look around the bedside for clues such as an eye patch, contact lens cases or solution, bottles of eye drops, dark glasses (suggesting photophobia) or visual aids. Observe the patient's face as a whole for any obvious asymmetry, swelling or a vesicular rash. A rash in the distribution of the ophthalmic branch of the trigeminal nerve raises the possibility of herpes zoster ophthalmicus, particularly if it involves the tip of the nose (Hutchinson's sign), which indicates a high risk of ocular involvement.

Eyelids and Lashes

Inspect the eyelids and lashes of both eyes, comparing the two sides. Assess the position, symmetry and any swelling of the lids. Generalised lid oedema may be inflammatory (as in periorbital or orbital cellulitis, which is a sight- and life-threatening emergency) or allergic, while a localised swelling is more likely to be a stye or chalazion.

Ptosis is a drooping of the upper eyelid. It may be caused by an oculomotor (third) nerve palsy, in which the eye is also typically 'down and out' with a dilated pupil, or by Horner's syndrome, where the ptosis is partial and accompanied by a constricted pupil (miosis) and reduced sweating (anhidrosis) due to interruption of the sympathetic supply. A fatigable ptosis that worsens through the day suggests myasthenia gravis.

Look at the direction the lid margin faces. In entropion the lid turns inwards, causing the lashes to rub on the cornea (trichiasis) and risking corneal abrasion. In ectropion the lid turns outwards, exposing the conjunctiva and causing watering and dryness.

Examine the lid margins for blepharitis, seen as crusting, redness and scaling at the base of the lashes due to chronic inflammation of the lid margin glands. A localised, tender, red swelling on the lid margin is a stye (hordeolum), an acute infection of a lash follicle, whereas a firmer, non-tender lump within the lid is usually a chalazion, a blocked and inflamed Meibomian gland. Note any lesions on the lid skin that could represent a basal cell carcinoma, particularly those with a pearly, ulcerated or lash-destroying appearance.

Conjunctiva and Sclera

Ask the patient to look up while you gently pull down the lower lid to expose the inferior conjunctiva, then ask them to look in different directions to inspect the bulbar conjunctiva (overlying the white of the eye) and sclera.

Assess the pattern of any redness, as this is one of the most useful localising signs in the red eye. Diffuse redness that is more pronounced peripherally and spares the area around the cornea suggests conjunctivitis. A sectorial patch of redness involving one segment of the eye points to episcleritis; these superficial vessels can be moved with a cotton bud and blanch with topical phenylephrine, which helps distinguish it from deeper inflammation. Redness that is concentrated in a ring around the cornea (ciliary or circumcorneal injection) is more worrying and points to deeper pathology such as anterior uveitis, keratitis or acute angle-closure glaucoma.

A subconjunctival haemorrhage appears as a flat, well-demarcated area of bright red blood under the conjunctiva, with normal vision and no pain. It is caused by rupture of a small conjunctival vessel, often after coughing, straining or minor trauma, and is usually harmless and self-limiting, although it may prompt a check of blood pressure or clotting if recurrent.

Note any chemosis, a boggy, fluid-filled swelling of the conjunctiva that can balloon over the lid margin in marked cases. It reflects conjunctival oedema and is typically seen in allergic conjunctivitis, severe infection or orbital inflammation. While inspecting, also scan the conjunctival and scleral surfaces for any foreign body, abrasion or laceration, particularly after trauma; a full-thickness scleral laceration or a teardrop-shaped, peaked pupil should raise concern for a penetrating (open globe) injury, which requires the eye to be shielded and urgent ophthalmology referral without further manipulation.

Image - A subconjunctival haemorrhage seen as a flat, well-defined patch of bright red blood beneath the conjunctiva, sparing the cornea. Vision and the pupil are unaffected

Creative commons source by Daniel Flather [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Inspect the sclera itself for colour. A diffuse yellow tinge to the sclera indicates jaundice, reflecting a raised bilirubin. A localised area of deep, boring redness with severe pain that may wake the patient at night suggests scleritis, which is frequently associated with systemic autoimmune disease such as rheumatoid arthritis, whereas the milder, more superficial inflammation of episcleritis is usually self-limiting and far less painful.

Cornea

Using your pen torch and magnification, inspect the cornea. A healthy cornea is perfectly transparent and gives a crisp, sharp reflection of the light. Loss of this clarity is significant.

A hazy or cloudy cornea suggests oedema, which occurs when the corneal endothelium fails to keep the cornea dehydrated. This is seen in acute angle-closure glaucoma (where the sharply raised intraocular pressure overwhelms the endothelial pump) and in advanced infection. Look for any white opacity or infiltrate on the cornea, which represents a collection of inflammatory cells and is the hallmark of a corneal ulcer or microbial keratitis, an ophthalmic emergency particularly in contact lens wearers.

Look for foreign bodies on the corneal surface, and assess the smoothness of the surface. A useful bedside test is to shine the torch tangentially across the cornea to throw any surface irregularity into relief.

At the slit lamp the same principle is used more powerfully: the illumination beam is narrowed to a thin slit and directed obliquely so that it cuts an optical section through the clear cornea. This reveals the corneal layers in three dimensions - the surface epithelium, the stroma and the deep endothelium - and lets you judge the exact depth of any ulcer, infiltrate or foreign body.

To detect epithelial defects that are invisible to the naked eye, instil fluorescein drops and examine the cornea under a cobalt blue light. Fluorescein pools in and binds to areas where the protective surface epithelium has been lost, so any defect lights up as a bright green patch. A diffuse or geographic area of uptake indicates a corneal abrasion, while a characteristic branching, dendritic pattern of staining is highly suggestive of herpes simplex keratitis - an important diagnosis to make, as inadvertent treatment with topical steroids can be sight-threatening.

Image - A small corneal ulcer in a contact lens wearer, highlighted by fluorescein staining. The defect in the corneal epithelium takes up the dye and fluoresces, marking the area of epithelial loss

Creative commons source by Iceclanl [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)]

Anterior Chamber

The anterior chamber is the fluid-filled space between the cornea and the iris. With the pen torch, assess its depth and look for any abnormal contents.

A useful bedside manoeuvre is to shine the torch from the temporal side across the front of the eye. In a normal, deep chamber the whole iris is illuminated evenly. If the chamber is shallow, the iris is bowed forwards and casts a crescent of shadow on its nasal side. A shallow anterior chamber is an important finding because it predisposes to acute angle-closure glaucoma, in which the peripheral iris obstructs aqueous drainage and the intraocular pressure rises rapidly. At the slit lamp this is formalised by the van Herick technique: a thin beam is shone at the very edge of the cornea and the width of the peripheral anterior chamber is compared with the thickness of the cornea beside it. The narrower the gap relative to the corneal thickness, the more occludable the drainage angle is judged to be.

Next look closely for inflammatory activity within the chamber. In anterior uveitis (iritis) white cells and leaked protein enter the normally crystal-clear aqueous. With a bright, narrow slit-lamp beam angled into the chamber, individual cells can be seen drifting like dust motes, and a generalised haze of protein - flare - scatters the light in the way a sunbeam is made visible by dust in a room (the Tyndall effect). The number of cells and the degree of flare are graded to quantify the severity of inflammation, and their presence, together with circumcorneal redness, pain and photophobia, is what defines active anterior uveitis.

Look for an abnormal fluid level within the chamber, which settles inferiorly under gravity. A hyphaema is a level of blood in the anterior chamber, usually following blunt trauma to the eye, and warrants urgent assessment because of the risk of raised intraocular pressure and rebleeding. A hypopyon is a level of white, inflammatory cells (effectively pus) and indicates severe inflammation within the eye, such as a sight-threatening microbial keratitis with anterior chamber involvement or severe anterior uveitis (iritis).

Image - A hyphaema, with blood settling under gravity to form a level in the lower half of the anterior chamber, typically following blunt ocular trauma

Creative commons source by Rakesh Ahuja, MD [CC BY-SA 2.5 (https://creativecommons.org/licenses/by-sa/2.5)]

Iris and Pupils

Inspect the iris for its colour and structure before assessing the pupils. A difference in colour between the two irides (heterochromia) can be congenital, but an acquired pale, washed-out iris on one side may accompany Horner's syndrome, especially when present from birth. Then assess the pupils, noting their size, shape and symmetry. They should be equal, central and round.

An irregular or distorted pupil may be due to posterior synechiae, adhesions between the iris and the lens that form in anterior uveitis and give the pupil a notched or scalloped outline. An irregular pupil may also follow trauma or previous surgery. A mid-dilated, oval and unreactive pupil in a red, painful eye with a cloudy cornea is a classic feature of acute angle-closure glaucoma.

Anisocoria (unequal pupils) should prompt you to decide which pupil is abnormal. A small degree of anisocoria is common and physiological; comparing the pupils in bright and dim conditions helps localise the problem. If the difference is greater in bright light, the larger pupil is failing to constrict and is the abnormal one (as in a third nerve palsy or Holmes-Adie pupil); if the difference is greater in the dark, the smaller pupil is failing to dilate and is abnormal (as in Horner's syndrome). A pathologically constricted pupil with partial ptosis suggests Horner's syndrome; a fixed dilated pupil with ptosis and an eye that is 'down and out' suggests an oculomotor (third) nerve palsy, which can be a surgical emergency if caused by a compressive aneurysm.

Assess the pupillary light reflexes. Shine the pen torch into one eye and observe the direct response (constriction of that pupil) and the consensual response (simultaneous constriction of the other pupil). The afferent (sensory) limb of this reflex travels in the optic nerve, while the efferent (motor) limb travels in the oculomotor nerve; because the pathway crosses centrally, light in one eye normally constricts both pupils equally.

Finally, perform the swinging light test to detect a relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil. Swing the torch smoothly from one eye to the other every few seconds. Normally both pupils stay constricted throughout. If one optic nerve or retina is significantly diseased, swinging the light from the healthy eye to the affected eye causes both pupils to dilate, because the reduced signal carried by the damaged optic nerve produces less constriction than the consensual drive that was just removed. An RAPD is an objective sign of significant optic nerve disease (such as optic neuritis or ischaemic optic neuropathy) or extensive retinal disease.

Image - Anterior uveitis (iritis), showing circumcorneal redness. Inflammation in the anterior chamber can lead to an irregular pupil through the formation of adhesions between the iris and lens

Creative commons source by Jonathan Trobe, M.D. [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)]

Lens

The lens sits immediately behind the iris and is the most posterior structure of the anterior segment. It is best examined with the slit lamp, but you can gain useful information at the bedside by assessing the red reflex: hold the ophthalmoscope at arm's length and look through it at the pupil, where a healthy lens transmits a uniform orange-red glow reflected back from the fundus.

A clouding of the lens is a cataract. As the lens loses its transparency it obstructs and scatters incoming light, so the patient typically reports gradually blurred vision and glare. On examination the red reflex is dulled or absent, and a dense cataract may be visible directly as a grey or white opacity within the pupil. Cataract is most often age-related, but it also occurs earlier in diabetes, in chronic uveitis, after long-term corticosteroid use, and following ocular trauma. Bear in mind that the red reflex can also be reduced by anything that obscures the visual axis behind the lens, such as a vitreous haemorrhage or retinal detachment, so a normal-looking lens with a poor reflex still warrants further assessment. An absent red reflex in a child is a red-flag finding that mandates urgent referral, as it may indicate a congenital cataract or retinoblastoma.

Eyelid Eversion

If the history suggests a foreign body (for example a gritty, persistent sensation, or work involving grinding or drilling) but nothing is visible on the surface, you should evert the upper eyelid to inspect the superior tarsal conjunctiva. Foreign bodies frequently lodge here, hidden from view, and continue to scratch the cornea with every blink, producing the characteristic vertical linear abrasions seen on fluorescein staining.

Warn the patient and gain their cooperation, as eversion is uncomfortable and a startled patient may pull away. Instil a drop of topical anaesthetic if available. Ask the patient to look down and keep looking down throughout. Gently grasp the eyelashes of the upper lid, place a cotton bud horizontally across the upper part of the lid, and fold the lid back over the cotton bud to expose the inner surface.

Inspect the everted conjunctiva carefully for any foreign body, follicles or papillae, removing a loose foreign body with a moistened cotton bud if seen. To return the lid to its normal position, ask the patient to look up and the lid will usually flip back on its own.

Completing the Examination

Thank the patient and wash your hands.

Remember to repeat the relevant elements of the examination on the other eye for comparison, if you have not already done so.

Summarise your findings.

To complete the examination, state that you would perform a full eye examination, including formal assessment of visual acuity with a Snellen chart, visual fields, eye movements, colour vision and fundoscopy to examine the posterior segment. You should also measure the intraocular pressure (for example by tonometry) where there is any suspicion of glaucoma, and ideally perform a detailed slit lamp examination. Depending on the findings, suggest relevant further investigations and early referral to ophthalmology, as several anterior segment diagnoses - including acute angle-closure glaucoma, microbial keratitis and a large hyphaema - are sight-threatening emergencies requiring urgent specialist input.

Quiz

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