Lids, lacrimal system, orbit, and ocular adnexa
Adnexal disease rewards systematic anatomy. The exam asks you to localise a lesion to a lid layer, a lacrimal segment or an orbital compartment, and to separate conditions that are dangerous, such as orbital cellulitis or sebaceous carcinoma, from those that are merely troublesome.
Eyelid
Layers are skin, orbicularis, orbital septum, levator aponeurosis and Müller muscle (upper lid), capsulopalpebral fascia (lower lid), tarsus and conjunctiva. Ptosis is aponeurotic (high crease, good levator function), myogenic, neurogenic, mechanical or congenital. A chalazion is a lipogranuloma of a meibomian gland; a hordeolum is acute infection. Involutional entropion and ectropion follow lid laxity. Any lesion with madarosis, ulceration or lash loss needs biopsy; sebaceous carcinoma masquerades as chronic blepharitis.
Lacrimal
Epiphora is assessed by tear meniscus height, fluorescein disappearance and syringing. A soft swelling below the medial canthus that regurgitates on pressure is a mucocele from nasolacrimal duct obstruction; a unilateral progressive adult obstruction needs imaging to exclude tumour. Congenital obstruction usually resolves with massage by 12 months, then probing, intubation, and dacryocystorhinostomy.
Orbit
Preseptal cellulitis spares eye movements and vision; orbital cellulitis causes proptosis and painful movement with risk of cavernous sinus thrombosis, so image and give intravenous antibiotics. Dysthyroid orbitopathy follows severity grading: smoking cessation and lubricants when mild, steroids or radiotherapy when active and moderate to severe, decompression for compressive optic neuropathy.
Worked example
A 2-year-old with a swollen lid after an upper respiratory infection, no proptosis and full eye movements. Reasoning: there are no orbital signs, so this is preseptal cellulitis; oral antibiotics and review, imaging only if proptosis or restricted movement develops.
Traps
Missing a pupil-involving third nerve palsy hidden behind a ptosis; treating all epiphora as dry eye; failing to biopsy a recurrent chalazion in an older adult, where sebaceous carcinoma is the diagnosis not to miss.