Abstract
BackgroundTo quantify the development of radiation neuropathy in corneal subbasal nerve plexus (SNP) after plaque brachytherapy, and the subsequent regeneration of SNP micromorphology and corneal sensation.MethodsNine eyes of 9 melanoma patients (ciliary body: 3, iris: 2, conjunctiva: 4) underwent brachytherapy (ruthenium-106 plaque, dose to tumour base: 523 ± 231 Gy). SNP micromorphology was assessed by in-vivo confocal microscopy. Using software developed in–house, pre-irradiation findings were compared with those obtained after 3 days, 1, 4 and 7 months, and related to radiation dose and corneal sensation.ResultsAfter 3 days nerve fibres were absent from the applicator zone and central cornea, and corneal sensation was abolished. The earliest regenerating fibres were seen at the one-month follow-up. By 4 months SNP structures had increased to one-third of pre-treatment status (based on nerve fibre density and nerve fibre count), and corneal sensation had returned to approximately two-thirds of pre-irradiation values. Regeneration of SNP and corneal sensation was nearly complete 7 months after plaque brachytherapy.ConclusionsThe evaluation of SNP micromorphology and corneal sensation is a reliable and clinically useful method for assessing neuropathy after plaque brachytherapy. Radiation-induced neuropathy of corneal nerves develops quickly and is partly reversible within 7 months. The clinical impact of radiation-induced SNP damage is moderate.
Highlights
To quantify the development of radiation neuropathy in corneal subbasal nerve plexus (SNP) after plaque brachytherapy, and the subsequent regeneration of SNP micromorphology and corneal sensation
While iodine-125 and ruthenium-106 (Ru-106) have each been used for plaque brachytherapy [1,2,3,4,5], the advantages of plaques containing Ru-106 as a beta-emitter include a finite range of radiation [6]
No subbasal nerve fibres were visualised in the applicator zone or in the central zone (Figure 3d, e) and very few in the distal zone (Figure 3f )
Summary
To quantify the development of radiation neuropathy in corneal subbasal nerve plexus (SNP) after plaque brachytherapy, and the subsequent regeneration of SNP micromorphology and corneal sensation. The development of small-fibre neuropathy has been investigated using confocal microscopy in diabetic patients [15,16] and in those with Fabry disease [17]. Our group has established 3-dimensional image reconstruction of the cornea, as well as real-time mapping of large-scale 2-dimensional images of the SNP [18]. This methodology permits the quantitative analysis of corneal nerve structures by confocal microscopy [19]
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