Describe the anatomy of the eyelid and the lid margin diseases.

Structure of the Eyelid

• The eyelids are movable folds protecting the globe, spreading the tear film and pumping tears into the lacrimal drainage system.
• Surgically they are divided into an anterior lamella (skin and orbicularis) and a posterior lamella (tarsus and conjunctiva), separated by the grey line.
• The lamellar division IS the key surgical concept: shortage of the anterior lamella causes cicatricial ectropion (the lid is pulled outward), and shortage of the posterior lamella causes cicatricial entropion (the lid is pulled inward). Reconstruction must replace like with like, and at least one lamella must carry its own blood supply

Blepharitis and Lid Margin Disease

• Blepharitis is chronic inflammation of the lid margin, and is among the commonest of all ophthalmic conditions. It is chronic, recurrent and controllable rather than curable — a fact that must be explained at the outset or the patient will judge every treatment a failure
• Anterior blepharitis affects the lash line and is of two kinds: staphylococcal, with hard, brittle, yellow crusts and collarettes around the lashes, lid margin ulceration, and complications of madarosis (lash loss), trichiasis, poliosis and tylosis; and seborrhoeic, with soft, greasy scales, less ulceration, and associated dandruff and seborrhoeic dermatitis
• Posterior blepharitis (meibomian gland dysfunction) affects the gland orifices: capping and plugging of the openings, thickened turbid or toothpaste-like secretion, telangiectasia of the margin, foamy tear film and notching. It is the commonest cause of evaporative dry eye
• Associations — acne rosacea, which should be looked for in every case (facial flushing, telangiectasia, papulopustules and rhinophyma); seborrhoeic dermatitis; atopic eczema; and demodex infestation, which causes cylindrical dandruff at the lash base and is diagnosed by epilating a lash and examining it
• Symptoms — burning, grittiness, itching and crusting, characteristically worse on waking; redness; and intermittent blurring that clears on blinking, from an unstable tear film
• Complications — recurrent stye and chalazion; evaporative dry eye; marginal (catarrhal) keratitis, a staphylococcal hypersensitivity infiltrate with a clear zone between it and the limbus; phlyctenulosis; punctate epithelial erosions of the lower third of the cornea; corneal vascularisation and scarring; chronic conjunctivitis; and contact lens intolerance
• Treatment — lid hygiene is the foundation and the surgery is incidental:
• Warm compresses for 5 to 10 minutes, which melt the inspissated meibomian secretion (its melting point is raised in disease), followed by lid massage to express the glands
• Lid SCRUBS with dilute baby shampoo or a commercial preparation on a cotton bud, applied along the lash line
• These must be done daily and continued long term; the commonest reason for failure is that they are done for a week and abandoned
• Topical antibiotic ointment (chloramphenicol, fusidic acid) rubbed into the lid margin at night for staphylococcal disease
• Oral doxycycline 100 mg for 6 to 12 weeks in meibomian dysfunction and rosacea — acting not as an antibiotic but by inhibiting bacterial lipases and matrix metalloproteinases and altering the lipid composition. Avoid in pregnancy and in children under 12, where erythromycin or azithromycin is used
• Topical steroid in short courses for marginal keratitis and severe inflammation, with the usual cautions; and topical ciclosporin for chronic disease