In‐vivo scanning of Ascher intrastromal corneal ring opacity

Case report

An 80‐year‐old man was seen with abnormal corneal appearances. He was asymptomatic with no previous ocular, medical or drug history. Visual acuities were 6/6 in both eyes unaided; with ocular examination revealing bilateral 0.1 mm wide white intrastromal corneal ring opacities 7.8 mm and 7.7 mm in diameter in the right and left eyes, respectively (fig 1). Corneal sensation was normal with no evidence of thinning, scarring or vascularisation. The remaining ocular examination was normal. Blood tests for lipid, protein and autoimmune markers were normal. Corneal pachymetry and topography was unremarkable. Cross‐sectional imaging of the cornea with anterior segment optical coherence tomography (Visante OCT, Carl Zeiss Meditec, Inc., USA) revealed opacification affecting the entire thickness of the stroma (fig 2). Confocal microscopy (HRT II/Rostock Cornea Module; Heidelberg Engineering GmbH, Germany) of the ring opacity revealed microdot extracellular deposits within the corneal stroma (fig 3). The epithelium and endothelium of the cornea appeared normal. Ocular examination of the patient's sister was unremarkable, with another sister unavailable for examination. There has been no progression with over 12 months follow‐up with the patient remaining asymptomatic.

Figure 1 Right eye: intrastromal corneal ring 0.1 mm in width, 7.8 mm in vertical diameter.

Figure 2 Optical coherence tomography of left cornea: highly reflective deposits are seen throughout the entire thickness of the corneal stroma.

Figure 3 Confocal microscopy of left cornea (depth 352 μm): microdeposits are visible as sparkling corpuscles spread within the extracellular tissue of the stroma. Collagen is seen located in the centre of the image with surrounding keratocytes.

Comment

Originally reported by Ascher¹ in 1963, intracorneal rings are rare;²,³,⁴,⁵,⁶,⁷,⁸ occurring both unilaterally or bilaterally, varying in both ring width and diameter in patients 25–80 years of age. Haematological and autoimmune investigations have been normal and family members have not been affected. Pachymetry and specular microscopy have been unremarkable.³,⁴ Bopp and Laqua⁵ described minute greyish dots distributed within outer stromal layers forming an arcus lipoides‐like circular band on biomicroscopy. In contrast, Melles et al.⁶ could not detect corneal deposition on biomicroscopy but commented on acoustic reflectivity similar to corneal tissue.

We performed optical coherence tomography, which demonstrated the full thickness involvement of the corneal stroma. Confocal microscopy of the ring opacity revealed the presence of highly reflective extracellular opacities located within the affected stroma.

Hypotheses for their aetiology include an unknown corneal dystrophy or degeneration.⁶ Bron² suggested that the rings represent an immunological reaction, with stromal damage at the site of previous antigen–antibody interactions, although their discreteness and stability would argue against this. The appearance of the rings, particularly on confocal microscopy, would suggest that they represent anomalous exogenous or endogenous extracellular microdeposits in the corneal stroma. Their apparent stability, discrete positioning in the midperipheral cornea and lack of any associated infiltrative or inflammatory response is possibly suggestive of altered collagen fibril formation.