3.1 Frequently Encountered Eye Conditions by Structure & Inflammation Versus Infection

Inflammation versus infection

These are not synonyms and the blueprint asks you to differentiate them.

• Inflammation is the stereotyped tissue response to any insult — trauma, autoimmunity, chemical injury, allergy or infection. Its signs are redness, swelling, heat, pain and loss of function.
• Infection is inflammation caused specifically by a replicating organism — bacterium, virus, fungus, protozoan or parasite.

All infection produces inflammation; most inflammation is not infection. The practical consequence is therapeutic: corticosteroids suppress inflammation but assist replication, which is why steroid monotherapy in herpes simplex epithelial keratitis or fungal keratitis is a serious error.

Lids and adnexa

Conjunctiva and cornea

Conjunctivitis patterns: bacterial gives purulent discharge and lids stuck shut; viral (usually adenoviral) gives watery discharge, follicles, a tender preauricular node and is highly contagious; allergic gives itching, chemosis and papillae. Itching is the hallmark of allergy — the single most reliable discriminator.

Corneal conditions: abrasion (positive fluorescein staining, severe pain, photophobia); recurrent erosion (pain on waking); bacterial keratitis (white infiltrate with overlying defect, hypopyon possible, contact-lens associated); herpes simplex epithelial keratitis (branching dendrite with terminal end bulbs, reduced corneal sensation); herpes zoster ophthalmicus (dermatomal V1 rash, Hutchinson sign); fungal keratitis (feathery margins, satellites, often after vegetable trauma); Acanthamoeba (severe pain out of proportion, ring infiltrate, poor hygiene or water exposure in lens wearers).

Lens, uvea, vitreous, retina and optic nerve

Lens. Nuclear sclerotic cataract causes gradual blur and a myopic shift; cortical cataract causes glare; posterior subcapsular cataract causes disproportionate near blur and glare and is associated with steroid use and diabetes. Ectopia lentis suggests Marfan syndrome (superotemporal subluxation) or homocystinuria (inferonasal).

Uvea. Anterior uveitis presents with ciliary flush, pain, photophobia, a small poorly reactive pupil and cells and flare in the anterior chamber. That constellation is the key discriminator from conjunctivitis, which is not painful, not photophobic and has no anterior chamber reaction.

Vitreous and retina. Posterior vitreous detachment causes floaters and flashes with a Weiss ring; a shower of floaters, a curtain and field loss is a retinal detachment until proven otherwise. Retinal vascular occlusions split cleanly: CRAO is painless, instant, with a cherry-red spot; CRVO is subacute with widespread haemorrhages in all four quadrants and a swollen disc. Diabetic retinopathy progresses from microaneurysms and dot-blot haemorrhages through cotton-wool spots and venous beading to neovascularisation. Age-related macular degeneration is dry (drusen, geographic atrophy) or wet (choroidal neovascularisation with subretinal fluid, haemorrhage, metamorphopsia).

Optic nerve. Optic neuritis is painful on eye movement, in a younger patient, with an RAPD and dyschromatopsia. Non-arteritic anterior ischaemic optic neuropathy is painless with altitudinal field loss in a crowded disc. Giant cell arteritis must be considered in anyone over 50 with jaw claudication, scalp tenderness or amaurosis fugax — it is a same-day referral.

Trauma and triage

A workable triage ladder for phone or front-desk screening:

1. See now — chemical splash (irrigate before anything else), suspected open globe, acute angle closure (pain, nausea, haloes, mid-dilated pupil, hard eye), sudden painless loss of vision, new curtain or shower of floaters, orbital cellulitis, suspected giant cell arteritis.
2. See today — corneal abrasion or foreign body, hyphaema, acute red painful eye with photophobia, new diplopia, contact-lens-related pain.
3. See this week — gradual blur, floaters without curtain, chronic red eye, lid lump.

For a chemical injury the sequence is irrigate immediately with sterile saline or lactated Ringer's, continue for at least 15 to 30 minutes, then check pH and keep irrigating until pH normalises. Do not delay irrigation to take a visual acuity.

Orbital disease and proptosis

The orbit is the one structure a technologist cannot inspect directly, so orbital disease is inferred from displacement of the globe, restriction of movement and changes in the lids. Proptosis — forward displacement of the globe — is the cardinal sign, and the differential splits sharply by age.

In adults, thyroid eye disease is by far the most common cause of both unilateral and bilateral proptosis. It produces lid retraction, lid lag on downgaze, injection over the horizontal rectus insertions, and a restriction that characteristically limits elevation first because the inferior rectus is the muscle most often enlarged. Imaging spares the tendon, which separates it from the tendon-involving inflammation of idiopathic orbital inflammatory syndrome. Chapter 9 covers the forced duction technique that distinguishes this restriction from a nerve palsy; what matters in this content area is recognising the pattern and describing it accurately.

In children, orbital cellulitis is the leading cause of acute proptosis and is usually an extension of ethmoid sinusitis through the paper-thin lamina papyracea. Rapid onset, fever, pain on movement and reduced vision separate it from the far more common preseptal cellulitis.

Other orbital lesions worth recognising on sight:

• Cavernous venous malformation (cavernous haemangioma) — the most common benign orbital tumour of adults. Slowly progressive, painless proptosis, sometimes with an induced hyperopic shift when the lesion indents the posterior globe.
• Orbital lymphoma — a painless, rubbery anterior or superior mass in an older patient, classically visible as a salmon-pink subconjunctival patch.
• Rhabdomyosarcoma — the most common primary orbital malignancy of childhood. Rapidly progressive proptosis in a child, often superonasal so the globe is displaced down and out, and an immediate referral.
• Orbital floor blow-out fracture — periorbital ecchymosis, enophthalmos, numbness in the infraorbital (V2) distribution, and restricted elevation from entrapment of the inferior rectus or the tissue around it.

Two qualifiers change the differential immediately. A pulsatile proptosis, especially with an audible bruit, points to a carotid-cavernous fistula. A proptosis that appears or worsens on Valsalva or when the patient lowers the head points instead to an orbital varix, a venous lesion rather than a solid mass.

Turning a symptom cluster into a structure

Items in this content area rarely name the diagnosis. They hand you a cluster of findings and ask which structure is involved, how urgent it is, or which test you should set up. Four questions resolve most of them.

1. Is there pain, and where? Surface pain with foreign-body sensation is corneal or conjunctival. A deep, boring ache with photophobia is uveal. Pain on eye movement is orbital or optic nerve. Painless points to a vascular event or, in a slow presentation, to a degenerative process.
2. Is vision reduced, and how quickly did it fall? Instant and painless suggests a vascular occlusion. Hours to days suggests inflammation or optic neuritis. Months to years suggests cataract, chronic glaucoma or macular degeneration.
3. Is there discharge, and of what kind? Purulent means bacterial. Watery with follicles and a tender preauricular node means viral. Itch with stringy mucus means allergy.
4. Is the pupil normal? A relative afferent pupillary defect moves the problem to the optic nerve, to a large area of retina, or to the chiasm and tract. A media opacity such as cataract does not produce one, however dense it is.

Add a fifth question to every red eye: does the redness spare the limbus or surround it? Diffuse bulbar redness that fades as it approaches the cornea is conjunctival and usually low urgency. A ciliary flush that is most intense in the ring immediately around the limbus signals intraocular inflammation — iritis, keratitis or acute angle closure — and moves the patient up the urgency ladder straight away.

Describe, do not diagnose

Record what you observe in terms another clinician can act on. "3+ diffuse bulbar injection, mucopurulent discharge, no ciliary flush, cornea clear to fluorescein, VA 20/25" is a usable entry for any examiner. "Conjunctivitis" is a diagnosis outside the technologist's scope, and once it is in the chart it quietly forecloses the examination the ophthalmologist still has to perform. The same discipline governs telephone triage: capture the symptoms and the time course, apply the urgency ladder above, and leave the diagnosis to the physician.