The Eyelids and Cornea

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The eyelids are the site of several tumours and cysts. The main tumours of the eyelid are derived from skin and skin appendages, and are histologically similar to those arising elsewhere in the skin. Cysts may develop from blockage and dilatation of skin appendages and minor glands in the eyelid.

Xanthelasmas, plaque-like, yellow lesions seen in the skin around the eyelids, are collections of lipid-filled histiocytes in the dermis. They may be associated with hyperlipidaemic states.

Conjunctival melanocytic naevi are the most common tumour of the conjunctiva. They are classified in a similar way to those seen in the skin 

Conjunctival papillomas are benign, red polypoid lesions that arise from the palpebral or bulbar conjunctiva; some have a viral aetiology.

Basal-cell carcinomas are common tumours that involve the skin of the eyelid up to the lid margin. They are locally invasive and identical to those arising in other sites.

Squamous-cell carcinomas arise from the skin of the eyelid or, less commonly, from the conjunctiva, where they may be preceded by intraepithelial carcinoma. 

  Malignant melanomas can arise in the conjunctiva or from the skin of the eyelid. Both intraepithelial and invasive lesions are seen, which are like those described in the skin.

Sebaceous gland carcinomas are uncommon but highly malignant tumours arising from the meibomian glands.

Chalzion

Blockage and infection of a meibomian gland causes swelling and acute inflammation of the affected gland. A chalazion is a firm swelling in the eyelid, which bulges under the palpebral conjunctiva. Caused by rupture of a meibomian gland, it histologically consists of a foreign-body histiocytic chronic inflammatory response to lipid-rich material derived from the destroyed gland 

A chalazion represents a histiocytic inflammatory response to lipid material released from damaged meibomian glands.

A chalazion (meibomian cyst) develops from blockage and inflammation of a meibomian gland. At first, lesions are red and tender, but later form firm nodules in the lid. Most resolve with local antibiotic ointment but some require curettage.

Lesions which do not resolve should be regarded with suspicion, as uncommon malignant tumours of the lid may present in this manner.


Proliferation of sub-epithelial support tissues gives rise to pingueculae, which are small areas of yellow thickening of the bulbar conjunctiva. Caused by cumulative exposure to damaging environmental stimuli such as sun, wind and dust, they increase in incidence with age. Similar areas that encroach over the limbus onto the cornea are termed pterygia.

Corneal diseases

The important diseases of the cornea result in structural changes leading to opacification and impairment of visual acuity.

Minor trauma to the cornea can cause painful loss of surface epithelium, termed corneal abrasion. This may be complicated by secondary infection, but in most cases heals with regeneration.

Infective or inflammatory disorders of the cornea, which are collectively termed keratitis, can result in scarring leading to opacification. Infection is most commonly due to viruses (herpes simplex), Chlamydia trachomatis (causing trachoma) and bacteria.

Corneal oedema is caused by loss of, or damage to, corneal endothelium. As the cornea becomes opaque with accumulation of interstitial fluid from failure of endothelial function, blurring of vision occurs. In severe cases, extremely painful bullae form beneath corneal surface epithelium, with secondary superficial scarring.
Corneal diseases commonly cause scarring and loss of visual acuity

The cornea is covered by a non-keratinized squamous epithelium and is composed of a stroma with a lining endothelium. The endothelium is vital to normal corneal function because it actively pumps fluid out of the corneal stroma. The stroma is composed of highly organized parallel layers of collagen. Deposition of abnormal collagen leads to an opaque scar termed a leukoma.

Arcus senilis,} seen as a yellow-white line at the corneal margin, is due to accumulation of lipid in between the corneal stromal lamellae. It is normal with ageing, but is associated with hyperlipidaemia when it arises in young patients.

Squamous metaplasia of the surface corneal epithelium may occur, causing corneal opacification. This is usually secondary to lack of normal lubrication by tears, e.g. in dry-eye syndromes or when diseases prevent eyelids covering the cornea. It can also be caused by vitamin A deficiency.
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