Variations in appearance of the normal eye

8.1.1

Epicanthus

Bilateral inner canthal nasal folds are very common in Caucasian infants and South and South-East Asians. It can make a child appear strabismic.

8.1.2

Subconjunctival haemorrhage

Whilst a striking appearance, most subconjunctival haemorrhages ( Fig. 8.1 ) are benign. These may be idiopathic or caused by trauma, a sudden increase in blood pressure resulting from heavy lifting, coughing or sneezing or blood thinning medication. No treatment is required, with complete resorption occurring within 21 days. In a large haemorrhage the posterior edge should be identified to rule out retrobulbar haemorrhage. In multiple, recurrent presentations without cause, investigation for blood disorders is appropriate.

8.1.3

Conjunctival epithelial inclusion cyst

These small benign fluid-filled cysts which are easily visible on slit-lamp examination ( Fig. 8.2 ). They occur when conjunctival cells find their way under the basement membrane, proliferate, and create a fluid-filled sphere. They may be idiopathic or commonly seen after trauma or surgery. No treatment is required for small cysts. Larger cysts may cause foreign body sensation that may be alleviated by lubrication. Surgical removal may be considered for very large cysts.

8.1.4

Scleral hyaline plaque

A scleral hyaline plaque ( Fig. 8.3 ) represents a localised hyaline degeneration of the sclera that occurs anteriorly to the medial rectus insertion. The sclera is thinned in this area enabling visibility of the uvea, hence the blue appearance. This condition is asymptomatic and of no consequence.

8.1.5

Axenfeld (intrascleral) nerve loops

The long posterior ciliary nerves travel within the sclera from the posterior segment before turning to branch into the ciliary body. The loops formed by these nerves as they turn into the ciliary body are sometimes visible as grey or purple-grey patches, possibly raised, possibly associated with pigment, typically associated with large veins, and located 3 mm posterior to the limbus ( Fig. 8.4 ). These are an entirely normal finding that should be differentiated from congenital conjunctival melanosis.

8.1.6

Congenital conjunctival melanosis

Relatively common, bilateral, benign, flat, pigmented areas of conjunctiva, typically near the limbus in young, heavily pigmented eyes ( Fig. 8.5 and online), which sometimes are called complexion-associated conjunctival melanosis. The pigmentation is darkest at the limbus with decreasing intensity away from it. It should be differentially diagnosed from the typically unilateral conjunctival naevus (or ‘freckle’).

8.1.7

Palisades of Vogt

Limbal epithelial folds that are arranged radially. They are more easily seen in young heavily pigmented eyes and are most prominent in the lower limbus ( Fig. 8.6 and online). They house limbal epithelial stem cells, which produce epithelial cells to maintain the normal corneal epithelium or replace it in the event of injury.

8.1.8

Posterior embryotoxon

Posterior embryotoxon occurs when the junction between the posterior cornea and the trabeculum (Schwalbe’s line) is thickened, making it more prominent and visible through the cornea on slit-lamp examination ( Fig. 8.7 ). This may be a complete or partial white ring, usually most visible at 3 and 9 o’clock. Posterior embryotoxon occurs in 8% to 30% of normal eyes, so as an isolated finding is of no concern. However, posterior embryotoxon is also associated with a number of anterior segment syndromes including Axenfeld-Rieger syndrome.

8.1.9

Pigment changes in the iris

Little or no pigment gives ‘blue eyes.’ With increasing amounts of pigment, the iris is seen as green, hazel, or brown. People with blue irises have greater light scatter than those with more pigmented irides and may suffer more from disability glare in situations such as driving at night. Variations in pigment can produce wedge-shaped sections of hyper- or hypopigmentation (heterochromia, Fig. 8.8 and online) in one or both eyes. Hyperpigmented spots (naevi or ‘iris freckles,’ Fig. 8.9 and online) are common, but should be monitored using photography for changes owing to the slight risk of malignant melanoma.

8.1.10

Persistent pupillary membrane

These are strands of the embryonic pupillary membrane that remain into adulthood. One end of the strand inserts into the iris colarette and the other is either attached to the anterior lens capsule or floats in the anterior chamber ( Fig. 8.10 is a common example, while Fig. 8.11 is rare).

8.2.1

Dermatochalasis

Dermatochalasis is benign, bilateral drooping of excess upper lid tissue with age that gives the appearance of tired or sleepy looking eyes ( Figs. 8.12 and 8.13 , and online). Cosmetic surgery is sometimes requested. Blepharoplasty or blepharoptosis repair can improve functional vision and may be recommended if the patient reports problems.

8.2.2

Ectropion and entropion

The eyelid is either turned outward (ectropion, see Fig. 8.13 ) or i n ward (e n tropion) owing to loose lids so that the inferior lid margin or puncta are not in contact with the eye. The patient may complain of epiphora or be symptomless. They are common complaints, found in about 4% of older patients and are often associated with dry eye and chronic blepharitis.

8.2.3

Seborrheic keratosis

Seborrheic keratosis is one of the most common benign eyelid tumours in the elderly. Hyperkeratinised, waxy, light grey-brown plaques are found over the eyelids and face and appear to be stuck onto the skin. Typically benign, but their natural history of gradually increasing in size, thickness, and/or pigmentation leads to fears of skin cancer and cosmetic concerns.

8.2.4

Papilloma

Papilloma, the most common benign lesion of the eyelid, is often known as a ‘skin tag.’ They are avascular, epithelial lesions of variable size, shape, and colour (amelanotic to black) with a roughened surface reflecting the redundant epithelial cell growth ( Fig. 8.14 ). Over time, they grow and become attached to the eyelid surface by a stalk (pedunculated, see online figure), so that the papilloma can be moved back and forth. You should reassure the patient and photograph the lesion, which can be removed for cosmetic reasons.

8.2.5

Xanthelasma

Bilateral, flat, light brown/yellow, triangular lipid masses with a nasal base, xanthelasma are typically found on the inner upper eyelids of elderly patients and especially females ( Fig. 8.15 and online). They usually have a familial aetiology, but can be linked with atherosclerosis and high cholesterol and any initial diagnosis of xanthelasma should be referred for further investigation. They often reoccur if removed, so the patient should be warned of this if considering cosmetic removal.

8.2.6

Corneal arcus (previously termed ‘arcus senilis’)

Commonly found, corneal arcus is a bilateral, 1.0 to 1.5 mm wide, greyish-white ring or part ring occurring in the periphery of corneas of older patients that is separated from the limbus by a thin ring of clear cornea, the lucid interval of Vogt ( Fig. 8.16 and online). It is called a corneal arcus rather than a corneal ring as it initially presents as arcs in the inferior and superior poles of the perilimbal cornea before spreading to form a complete ring. The inner edge is typically more diffuse than the sharper outer edge. Its prevalence increases significantly with age after 50 years. It is caused by lipid being deposited in the corneal stroma, having permeated from the limbal blood vessels, which become more permeable with age. Corneal arcus may be a sign of systemic hyperlipidaemias if seen in younger adults and any patient with arcus who is below the age of 50 years should be referred for further investigation.

8.2.7

Concretions

Typically concretions are asymptomatic, small (1 to 3 mm), yellow-white calcium lesions found in the palpebral conjunctiva of the upper and lower eyelid. They can be found in young adults, but are more common in elderly patients. The majority are superficial, hard, and single ( Fig. 8.17 and online). A small percentage of concretions can cause symptoms, likely from corneal irritation.

8.2.8

Limbal girdle of Vogt

The limbal girdle of Vogt is a common, bilateral degenerative condition producing a narrow band of white, crystal-like opacities along the nasal or temporal limbus, typically found in older female eyes ( Fig. 8.18 and online). Two types are described: type I has a perilimbal clear zone similar to corneal arcus and contains numerous holes, whereas type II has neither holes nor a clear zone.

8.2.9

Hudson-Stähli line

The Hudson-Stähli line is a common, corneal orangey-brown iron deposition line found close to where the lid margins meet when blinking. The line is generally horizontal, possibly with a slight V-shape in the middle ( Fig. 8.19 ). It can be continuous or segmented and, although some texts suggest that the prevalence typically matches the age of the patient, many Hudson-Stähli lines are faint and difficult to see under white light so that this high prevalence seems unlikely. However, they become more visible in cobalt blue (see online) or ultraviolet light. For this reason you may first notice it during a slit-lamp examination using fluorescein and cobalt blue illumination. Its aetiology is unclear, with the iron possibly arising from the tears, perilimbal blood supply, and/or caused by UV radiation and the line/vortex pattern being linked with the position of eyelid closure or the growth and repair patterns of the corneal epithelium. Similar corneal iron deposition can occur in orthokeratology patients where the pigment line appears where the corneal changes lead to tear pooling.

8.2.10

Crocodile shagreen

Crocodile shagreen is a polygonal pattern of white or grey opacity in the cornea with an appearance similar to crocodile skin ( Fig. 8.20 ). Peripheral crocodile shagreen is most common with a reported clinical incidence of 13%. The pattern is probably related to the arrangement of corneal fibrils allowing opacities to preferentially occur in some locations. Peripheral shagreen tends to progress towards, but never reaching, the central cornea. It can vary from faint to striking, and whereas the latter may be of concern, vision seems unaffected. No treatment is required, and referral is not appropriate.

8.2.11