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Editor,—Very rare, subtle conditions of the cornea may be infrequently reported but can provide valuable insights into the workings and diseases of the cornea. We report an unusual appearance of corneal rings in an asymptomatic patient with no similar abnormalities detected in first degree relatives.
A 56 year old white female emmetrope (20/20 both eyes) presented with photopsia secondary to posterior vitreous separation. Bilateral, thin (<0.5 mm), grey-white, granular but continuous, mid-peripheral stromal corneal ring opacities were incidentally noted (Figs 1 and 2). The rings were 7–8 mm diameter and in cross section were “V”-shaped: widest nearest to Descemet's membrane. The apex, anteriorly, was slightly displaced towards the centre of the cornea. The central and peripheral cornea was clear. Pachymetry and specular microscopy were unremarkable. The remainder of the anterior segment including drainage angle was completely normal. The patient had no previous history of eye disease or trauma.
Apart from bendrofluazide taken for hypertension, she took no other medicines. Systemic examination including hair, skin, and nails, was unremarkable. Full blood count, urea and electrolytes, liver function test, glucose, sedimentation rate, urate, copper, fasting lipids, and autoantibodies were normal. She was found to be heterozygous for factor V Leiden (present in 5% of the population).
Examination of all living first degree relatives (mother aged 89, brother aged 58, son aged 31, daughter aged 27) revealed no corneal abnormalities.
Within the literature we have found a total of six cases of bilateral corneal rings of a similar size and appearance to that which we describe; all without apparent aetiology.1-4 In four cases the rings are reported as predominantly located in superficial or anterior stroma.1 3 4 However, in the two other cases, wedge-shaped ring opacities, most dense over Descemet's membrane are described, a feature common to those we observed.2 The ages of the patients in these reports range from 25 to 80 and all investigations, sometimes exhaustive, were unremarkable. Where family members were examined, none demonstrated similar features and where patients were followed up (2–9 years), appearances remained stable. However, in one report, the rings were not observed during a ophthalmic examination 14 years previously, suggesting that they are not congenital in origin.1
Another report of a unilateral, off-white, anterior stromal, mid-peripheral ring is of note because the patient was found to have elevated serum cholesterol.5 However, the opacity may have been a unilateral arcus.4
Of the six bilateral cases reported, only two describe the ring as wedge-shaped in cross section and predominantly in the posterior stroma2 and closely resemble our case. With so few cases reported, over a wide range of ages, and without affected family members it is unclear whether the condition should be described as a dystrophy or a degeneration. It is important to report such rarities, so that further correspondence and reporting is encouraged which may lend insights into causes of more serious corneal abnormalities.