Bilateral Idiopathic Corneal Ring Opacity (Ascher Ring)

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doi: 10.62055/rmykuzqexpfw

ABSTRACT

BACKGROUND

Bilateral idiopathic ring-shaped opacification of the midperipheral corneal stroma – often referred to as Ascher ring – is an extremely rare finding reported only sparsely in the literature.

CASE REPORT

An asymptomatic 90-year-old man stated that “mysterious rings” had been discovered in his eyes by a past provider and, despite consultation with a specialist, the diagnosis proved elusive. Slit lamp evaluation revealed a thin, symmetrical, white-gray annulus of the anterior corneal stroma that circumscribed the pupil in each eye. The patient was diagnosed with Ascher ring.

CONCLUSION

Ascher ring is not visually significant and requires no treatment. Early recognition of this unusual entity may prevent unnecessary diagnostic workup.

Keywords: Ascher, circle, midperipheral, cornea, stroma

INTRODUCTION

Ring-shaped corneal opacities manifest in various conditions and situations, including infectious and non-infectious immune responses, drug-induced deposits, metabolic diseases, hematological disorders, stromal degenerations and dystrophies, arcus senilis, posterior embryotoxon, and laser-assisted in situ keratomileusis (LASIK) flaps.¹ This case presents a patient with Ascher ring, an exceedingly rare diagnosis, and provides an overview of the limited literature on the subject.

CASE REPORT

A 90-year-old Caucasian male noted that his past eye doctor had discovered “rings” in his eyes several years prior. The doctor had referred him to a specialist for a second opinion, but no diagnosis had been made.

The patient’s ocular history was significant for bilateral cataract extraction as well as laser retinopexy for an operculated hole in the right eye. He had no history of contact lens wear. His medical history was significant for prediabetes, hypertension, hyperlipidemia, stage III chronic kidney disease, congestive heart failure, vitamin B12 deficiency, anemia, asthma, chronic obstructive pulmonary disease (COPD), sleep apnea, gastroesophageal reflux disease (GERD), hypothyroidism, gynecomastia, prostate cancer for which he had undergone radiation treatment, restless leg syndrome, and chronic post-traumatic stress disorder (PTSD). He took the following medications: metoprolol, simvastatin, furosemide, potassium chloride, nitroglycerin, cyanocobalamin, ferrous sulfate, levothyroxine, montelukast, tiotropium/olodaterol, melatonin, pantoprazole, tamsulosin, magnesium, docusate, gabapentin, and simethicone. He was allergic to or had suffered adverse reactions to penicillin, terazosin, and contrast media in the past.

Best corrected vision was 20/20 in each eye. Intraocular pressure was 15 mmHg in the right and left eyes by rebound tonometry. Slit lamp biomicroscopy revealed a centrally located, horizontally oblong white-gray oval ring of the anterior corneal stroma approximately 5 mm in diameter (Figure 1). The thickness of the ring was roughly 0.5 mm. The corneal tissue inside the ring appeared normal. There was an age-appropriate amount of peripheral arcus senilis. There were no keratic precipitates, pigment, or guttae on the endothelium. The anterior chambers were deep and quiet without cell or flare. There were posterior chamber intraocular lenses in each eye. Dilated fundus examination showed posterior vitreous detachment bilaterally. The optic nerves were pink and healthy, with cup-to-disc ratios of 0.20 in the right eye and 0.40 in the left. There was a slight tuft of glial tissue on the left optic nerve. The maculae were flat, with a few pinpoint drusen in the left. There was an operculated hole in the right peripheral retina well-demarcated by laser barricade. All other exam findings were normal.

Figure 1 Anterior segment photos of each eye.

The differential diagnosis was narrowed by considering the clinical appearance and ocular history of the patient. The regularity of the rings initially suggested an iatrogenic mechanical process, however the patient had not worn contact lenses or undergone any ocular surgery or procedure which might explain their presence. Infectious causes, such as Acanthamoeba keratitis or herpetic keratitis, were immediately dismissed given the bilateral, asymptomatic presentation over multiple years. Wessely immune rings fade over time and often have less discrete demarcations between healthy and infiltrated tissue as they resolve. Cogan syndrome typically affects young adults and there were no signs of inflammation. Chrysiasis, argyrosis, and Wilson disease produce pigmented deposits. The clinical presentation did not match arcus senilis, a lysosomal storage disorder, or Schnyder corneal dystrophy. After careful review of the patient’s presenting signs and medical history, he was diagnosed with Ascher ring.

DISCUSSION

Bilateral idiopathic stromal ring opacities were first described by Ascher in 1964² and are only sparsely reported in the literature.³ They appear as centrally located white-grey lesions with distinct borders, but the presentation can vary. They are most often bilateral, but one unilateral case has been reported.⁴ Usually there is a single ring per eye, but a case of 4 concentric rings in each eye has been published.⁵ Rings may range in size from 4-10 mm in diameter and possess a band of constant thickness less than or equal to 0.5 mm. The shape of the rings is circular, oval, or oval with a slight deviation.^6,7 Their contours are smooth. The opacification is occasionally reported as granular^8-10 and is confined to the stroma, either from the anterior stroma to a variable depth, or full thickness of the cornea. In several descriptions the stromal profile is V-shaped, widest towards Descemet’s membrane and narrowest toward Bowman’s.^6,9 The central cornea within the ring is normal, except in one unusual case that presented with scattered linear grayish streaks.⁶

No clear demographic pattern has been established for Ascher ring within the limited cases available in the literature. There appears to be no age or sex predilection, although no pediatric cases have been published. The age of the youngest patient at time of diagnosis was twenty five⁸ and the oldest, our patient, was 90 years old.

Ascher ring is typically an incidental finding. Vision is unaffected and the patient is asymptomatic. Corneal sensitivity is normal. Extended observation of patients with Ascher ring has not revealed change over time. One patient was followed for 9 years, another for 7 years, and two for 5 years without detectable progression.^10-12

No cause for this finding has been determined. An immunological etiology is unlikely given the lack of central stromal disturbance in most cases of Ascher ring and the extended time course the rings remain unchanged. Several cases report the ring being absent on a previous exam, then appearing at a subsequent visit,^8,13 suggesting the condition is not congenital. Although a non-central asymptomatic thin corneal opacification might be initially overlooked or not documented in a busy clinic, Melles et al. described a patient examined by them at age 11 after unilateral ocular trauma, then subsequently by another eye doctor annually over 12 years. The patient was then referred back to Melles et al. for a symptomatic posterior vitreous detachment, and then again 2 years later after corneal rings were diagnosed. It is unlikely that both providers overlooked the presence of pre-existing corneal rings over that extensive time period. Additionally, the distinct lack of pediatric cases in the literature further argues against a congenital etiology.

Ascher ring has alternatively been suggested as a corneal dystrophy⁵ and a corneal degeneration.⁶ The bilateral, symmetric, and non-vascularized presentation suggests a dystrophy. However, the apparent onset later in life of Asher ring supports a degeneration instead. If dystrophies tend to be centrally located while degenerations are peripheral, then the midperipheral location of Ascher ring sits somewhere in between. Finally, although the clinical characteristics of Ascher ring might generally favor a designation of dystrophy over degeneration when choosing between the two, no similar finding among family members has been uncovered and no genetic marker ever identified.

Various authors have proposed that material may have been deposited after diffusion over a gradient.^1,10,12 Using the results of confocal microscopy, Nguyen et al. hypothesized that the rings were comprised of extracellular microdeposits of uncertain origin and their apparent stability, among other factors, suggested altered collagen fibril formation.¹⁴ Our patient, in his ninth decade of life, with many systemic comorbidities and an extensive list of medications, may not provide many clues to further elucidate the etiology of this unusual finding.

CONCLUSION

Ascher ring does not produce symptoms, affect vision, or require treatment. Its etiology remains idiopathic. Early recognition and careful diagnosis may prevent unnecessary workup and patient alarm. Given its benign prognosis and low prevalence, perhaps an individual with Ascher ring might take some pride in this unique facet of their eyes.

REFERENCES

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2. Ascher KW. [An unusual corneal ring]. Ber Zusammenkunft Dtsch Ophthalmol Ges. 1964;65:44-46. German.
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10. Caroline PJ, Melles GR. Two cases of bilateral, stromal ring opacity of the cornea. Cornea. 2001;20(2):237-238. doi:10.1097/00003226-200103000-00029
11. Bopp S, Laqua H. [Corneal Ascher ring. A ring-shaped stromal corneal opacity]. Klin Monbl Augenheilkd. 1991;198(3):201-204. German. doi:10.1055/s-2008-1045952.
12. Silvestri A, Boisjoly H. Bilateral corneal ring opacity of unknown origin. Cornea. 2003;22(1):86-87. doi:10.1097/00003226-200301000-00022
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Benjamin Graham, OD, FAAO, ABCMO

Sacramento VA | Mather, CA

Dr. Graham received his doctorate from the University of California, Berkeley School of Optometry and completed a residency at Togus VA in Maine. He practiced full-scope medical Optometry at Ophthalmic Consultants of Boston and then UCLA Stein Eye Institute before joining the Sacramento VA.