STEPTRACKERSPECIAL SENSES | PATHOLOGY + MICROBIOLOGY + ANATOMY | HIGH-YIELD REVIEW

Eyelid, Conjunctiva & Cornea

The red eye from the outside in — lids, conjunctiva and cornea — and the clues that separate harmless from sight-threatening.

FOCUS ON
Red eye with normal vision, no pain → conjunctivitis: viral (watery, preauricular node), bacterial (purulent, lids stuck), allergic (itch, bilateral). Red eye with pain, photophobia or ↓ vision → cornea, uvea or glaucoma. Contact lens wearer with a corneal ulcer → Pseudomonas. Neonatal conjunctivitis by day: chemical, gonococcal, chlamydial.
DISORDER
CAUSE · MECHANISM
FEATURES
CLUE · TREATMENT
Hordeolum (stye)
Acute S aureus infection of a lid gland (external: Zeis/Moll; internal: meibomian)
Painful, red swelling at the lid margin
Warm compresses
Chalazion
Blocked meibomian gland → lipogranuloma (sterile)
Painless, firm nodule within the lid
Recurrent in same spot → biopsy (sebaceous carcinoma)
Blepharitis
Lid-margin inflammation; staphylococci, seborrhea, rosacea, Demodex
Crusting lashes, burning, red lid margins
Lid hygiene
Viral conjunctivitis
most common
Adenovirus (pharyngoconjunctival fever); very contagious
Watery discharge, gritty feeling, starts one eye then both; preauricular lymph node
Supportive; hand hygiene
Bacterial conjunctivitis
S aureus, S pneumoniae, H influenzae, Moraxella
Thick purulent discharge, lids stuck shut in the morning
Topical antibiotics
Allergic conjunctivitis
Type I hypersensitivity (mast cells)
Bilateral itching, tearing, chemosis; atopic history
Antihistamine/mast-cell stabilizer drops
Neonatal conjunctivitis
Day 1: chemical (silver nitrate) · days 2–5: N gonorrhoeae · days 5–14: C trachomatis
Gonococcal: hyperpurulent, risk of corneal perforation · chlamydial: may be followed by pneumonia
Erythromycin prophylaxis · systemic ceftriaxone / oral erythromycin
Trachoma
C trachomatis serotypes A–C; repeated infection
Lid scarring → inturned lashes (trichiasis) → corneal scarring
Leading infectious cause of blindness worldwide
Infectious keratitis
Bacteria (Pseudomonas with contact lenses), HSV, fungi (plant trauma), Acanthamoeba (lens + tap water)
Pain, photophobia, ↓ vision, corneal opacity/ulcer
Emergency · HSV: dendritic ulcer on fluorescein
Corneal abrasion
Epithelial scratch (foreign body, contact lens)
Pain, tearing, foreign-body sensation; fluorescein-staining defect
No patching for lens wearers (Pseudomonas)
Pinguecula · pterygium
UV-induced elastotic degeneration of conjunctiva
Pinguecula: yellow nodule beside cornea · pterygium: wedge of tissue growing onto the cornea
Sun, wind, dust exposure
Keratoconjunctivitis sicca
↓ tear production (Sjögren, age, anticholinergics) or ↑ evaporation
Dry, gritty, burning eyes; worse at day's end
Schirmer test · artificial tears

Mechanism — sorting the red eye

Red eye
→
Vision normal, no painConjunctivitis, subconjunctival hemorrhage
Pain, photophobia, ↓ visionKeratitis, uveitis, acute glaucoma

Conjunctivitis redness is maximal peripherally; ciliary flush (redness ringing the cornea) points to deeper disease — uveitis, keratitis or glaucoma.

Conjunctivitis compared

TYPE
DISCHARGE
KEY SYMPTOM
CLUE
Viral
Watery
Grittiness
Preauricular node, URI
Bacterial
Purulent
Lids stuck shut
Often one eye first
Allergic
Watery, stringy
Itch
Bilateral, atopy
Gonococcal
Hyperpurulent
Rapid onset
Newborn day 2–5, adults with urethritis
Chlamydial
Mucopurulent
Chronic follicles
Newborn day 5–14

How it's tested

COMMON CONFUSIONStye vs chalazion: both are lid lumps. Stye = acute, painful, infected; chalazion = chronic, painless, granulomatous.
THE TRAPNever give topical steroids for a red eye of unknown cause — they worsen HSV keratitis and fungal infection and raise intraocular pressure.
YOUR APPROACHVision + pain + photophobia → superficial or deep → discharge type → exposure (contact lenses, newborn, plants) → organism → treatment.

If you see… think…

Painful red lump at the lid margin → hordeolum (S aureus)
Painless firm lid nodule for weeks → chalazion
Watery red eye, sore throat, preauricular node → adenovirus conjunctivitis
Itchy watery eyes every spring → allergic conjunctivitis
3-day-old with copious purulent eye discharge → gonococcal ophthalmia neonatorum
10-day-old with conjunctivitis, later staccato cough → Chlamydia trachomatis
Contact lens wearer with painful corneal ulcer → Pseudomonas keratitis
Branching ulcer on fluorescein staining → HSV keratitis
Keratitis after rinsing lenses in tap water → Acanthamoeba
Wedge of conjunctiva growing onto the cornea in a fisherman → pterygium