The anterior segment of the eye usually refers to the cornea, iris, and lens. Most of the anterior segment conditions can be diagnosed clinically with a slit lamp.
However, even without a slit lamp, many anterior segment signs can be picked up using a torch together with close observation alone. This is particularly important as many potentially blinding conditions are caused by systemic diseases and it is important to pick these signs up early.
A number of systemic conditions can cause corneal problems.
Rheumatological conditions, in particularly rheumatoid arthritis, can cause a peripheral thinning of the cornea called peripheral ulcerative keratitis. If untreated, this can lead to perforation of the cornea and loss of integrity of the globe. Other examples include systemic lupus erythematosus, Wegener’s granulomatosis and polyarteritis nodosa.
Other autoimmune diseases can also affect the cornea. Steven-Johnson syndrome can cause inflammation of the cornea and conjunctiva in the acute phase, which can result in severe scarring and conjunctivalization in the chronic phase (Figure 1).
Abnormal corneal depositions from systemic diseases or medications can also occur, e.g. Wilson’s disease causing Kayser-Fleischer rings in the cornea periphery (Figures 2 and 3), or patients on amiodarone causing vortex keratopathy.
Kayser-Fleischer rings in Wilson’s disease – the copper deposition first appears in the superior and inferior peripheral cornea. Under slit-lamp, the copper depositions can be seen on the posterior layer of the cornea (the Descemet’s membrane).
The above photo (Figure 4) is from a patient with corneal transplantation. The cornea is an immune-privileged site for transplantation as it has no blood supply. ABO compatibility is not required for transplant. However, rejection can still occur and therefore patients will need long term topical steroid therapy. However, systemic immunosuppressants is rarely required.
The above photo (Figure 5) is from a patient with prolapsed orbital fat. Although alarming at first glance, this is in fact a rather common, benign condition, which is associated with advanced age. The orbital fat prolapses through the orbital septum and appears as a yellowish mass, most commonly at the supero-temporal region. Vision and extra-ocular eye movements are typically NOT affected. Indication for surgical excision of the prolapsed fat is mainly for cosmetic purposes.
Inflammation of the iris – iritis, also referred to as anterior uveitis, can be associated with a number of systemic conditions, the most common being the sero-negative spondyloarthropathies. In uveitis, the signs include ciliary injection, anterior chamber cells, keratitic precipitates on the posterior surface of cornea, and posterior synechiae (adhesion between the lens and iris, Figure 1). A slit lamp is required to detect anterior chamber cells. But for posterior synechiae, it can often be detected by just using a torch.
Posterior synechiae refers to abnormal adhesions between the lens and iris. This sign can be detected without a slit lamp, whereas the hallmark of uveitis – the presence of cells in the anterior chamber – requires a slit lamp.
When there is a severe anterior chamber reaction, hypopyon can be seen (Figure 2). When hypopyon is seen, endophthalmitis must be ruled out. Etiologies include post-intraocular surgery, trauma and endogenous causes.
This is a key feature of endophthalmitis and is an ophthalmic emergency. In this patient there is significant corneal injection, corneal oedema and also pus seen in the anterior chamber (hypopyon).
For endogenous endophthalmitis, it is classically associated with Klebsiella sepsis. The infection will progress rapidly, and aggressive systemic and intra-vitreal antibiotics are required to control the infection. Otherwise, the patient may need an evisceration (removal of all intraocular contents, only leaving a scleral shell) if the infection is uncontrolled.
Ageing is the most common cause of cataracts (Figure 1), but a number of systemic conditions are also associated with development of cataracts, e.g. myotonic dystrophy (Christmas tree cataract, Figure 2), medications (such as anti-psychotics causing stellate cataract) and Wilson’s disease (sunflower cataract).
Figure 1. Nuclear sclerosis cataract – this is the most common form of cataracts which is associated with ageing. The nucleus of the lens has become yellow in colour.
Figure 2. Christmas tree cataract – this type of cataract is associated with myotonic dystrophy.
Subluxation of the lens (Figure 3) is a feature of Marfan’s syndrome. Other causes of lens subluxation include trauma, pseudo-exfoliation syndrome, high myopia, very mature cataract etc.
Figure 3. Lens subluxation – commonly seen in Marfan’s syndrome. In this patient, the zonules can still be seen.