Sir,

Asteroid hyalosis is a benign vitreous disease with a minimal impact on visual function. Its prevalence among normal individuals is ∼1%1 and may be higher among diabetic patients. Occasionally, clinicians feel stress while observing the eyes with severe asteroid hyalosis because asteroid bodies are brightly shining on the microscopic light. A previous report referred that asteroid hyalosis was the cause of 8.5% of ungradable colour photographs in the cohort.2

Case report

An 80-year-old man was followed up after the treatment of glaucoma at Kyoto University Hospital. He had type 2 diabetes and presented for yearly fundus examinations. On the basis of these findings, the patient was diagnosed with moderate non-proliferative diabetic retinopathy, although the presence of bilateral severe asteroid hyalosis prevented detailed observation (Figure 1a). In 2012, the right eye had exhibited signs of a small pre-retinal haemorrhage. Fluorescein angiography was performed, and it revealed bilateral neovascularisation (Figure 1b). The patient was treated with pan-retinal photocoagulation (PRP), however, the resulting laser scars could not be assessed effectively by slit-lamp biomicroscopy owing to the obstructing presence of the asteroid hyalosis. The laser scar did appear as an area of hyperfluorescence when imaged using wide-field fundus autofluorescence (FAF) (Figure 1c). The evidence provided by these FAF images allowed us to perform additional photocoagulation as necessary (Figure 1d).

Figure 1
figure 1

(a) Wide-field colour photographs and (b) fluorescein angiography obtained before treatment. (c) Wide-field autofluorescence during pan-retinal photocoagulation. The red circle denotes the absence of the laser scar. (d) Wide-field autofluorescence after additional laser treatment.

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Comment

The results of examinations at our institution have shown that fluorescein angiography (FA) and optical coherence tomography (OCT) images are better suited compared with colour photography or indirect microscopy for imaging eyes with asteroid hyalosis. FA and OCT imaging utilise specific wavelengths of light and are less affected by asteroid hyalosis than are conventional imaging approaches such as colour photography or indirect microscopy, both of which utilise white light.3, 4 The Optos 200TX (Optos PLC, Dunfermline, UK) used for autofluorescence imaging at our institution utilises green light with a wavelength of 532 nm and detects the emitted signal with a detector calibrated for detection at 570–780 nm. The use of a single wavelength may reduce reflection by asteroid bodies.

Wide-field FAF therefore represents a non-invasive tool with which to localise laser scars and thereby inform the practice of PRP. This tool will be extremely valuable in the treatment of individuals with proliferative diabetic retinopathy and severe asteroid hyalosis.