Cotton-wool spots lead to tissue loss and RNFL defect

January 22, 2020

RNFL defects are associated with glaucomatous optic neuropathy and secondary to optic disc drusen.

57-year-old male patient with a 20+- year history of systemic hypertension and diabetes presented to the clinic for refractive care.

He was an insulin dependent diabetic, but he was unsure of his hypertension medication. He reported that his blood sugar levels were between 140 and 200 but that his A1C was unknown.

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Case information

Best-corrected visual acuity was 20/25 in each eye. He had normal extraocular muscle movements as well as full confrontation fields. The anterior segment examination was unremarkable and applanation tensions were 16 mm Hg in each eye.

The color fundus photograph (CFP) of the right eye is shown in Figure 1. There are a few notable features that include hemorrhages and microaneurysms, cotton-wool spots  CWS) as well as a distinct vascular irregularity superior temporal to the optic disc.

Assessment of the diabetic retinopathy was moderate to severe for this patient’s right eye. Alternatively, this would correspond to approximately Level 35 on the Diabetic Retinopathy Severity Scale algorithm.1

Cross-sectional optical coherence tomography (OCT) of the right eye demonstrates normal central macular thickness and contour (Figure 2). Topographic OCT demonstrated thickening of the macula and corroborated clinical evidence of the CWS within the RNFL profile (Figure 3).

The left eye had similar but more extensive diabetic retinopathy manifestations; however, that is not included in this report.

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Follow up 

The patient was observed closely over the next four months, at which point he developed center-involving macular edema of the left eye. 

He was referred to a retina specialist who recommended treatment with anti-vascular endothelial growth factor (VEGF) injections that the patient refused. 

He was followed up in a further three months. The CFP of the right eye from that visit appears in Figure 4. Note that the area where the cotton-wool spot had been now has a retinal nerve fiber layer (RNFL) defect. 

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Discussion 

Ischemia is the pathophysiology behind cotton- wool spots. It is not unreasonable to expect that a sequela may be tissue loss and consequent RNFL defect. This has been documented subsequently from a case as part of the Beijing Eye Study.2

The appearance of a RNFL defect has been associated classically with glaucomatous optic neuropathy as well as secondary to optic disc drusen. These well-known progenitors of RNFL defects may have a similar ischemic etiology to the RNFL defect, in this case. Clinicians should be aware of this possible sequela from cotton-wool spots and investigate every incidence.

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References:

1. Slakter, JS, Schneebaum JW, Shah SA. Digital Algorithmic Diabetic Retinopathy Severity Scoring System (An American Ophthalmological Society Thesis). Trans Am Ophthalmol Soc. 2015 Sep; 113: T9.
2. Zhang L, Xu L, Zhang JS, Zhang YQ, Yang H, Jonas J. Cotton-wool spot and optical coherence tomography of a retinal nerve fiber layer defect. Arch Ophthalmol. 2012 Jul 1;130(7):913.

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