Infrared Ophthalmoscopy as Diagnostic Tool for Neurofibromatosis Type 1

Abstract

Purpose: : To assess "choroidal nodules" as a new diagnostic criterium for Neurofibromatosis type 1 (NF1)

Methods: : Between September 2007 and October 2008, we examined 95 consecutive patients (190 eyes) with NF1 and 100 age- and sex-matched healthy controls. Exclusion criteria were media opacity conditioning the fundus oculi examination. Each subject underwent visual acuity (VA) evaluation, complete ophthalmic examination and retinography with a confocal scanning laser ophthalmoscope (SLO) (Heidelberg Retinal Angiograph [HRAII], Heidelberg, Germany) using infrared (IR) (WL 830 nm), autofluorescence (AF) (WL 488 nm excitation, over 500 nm emission) and red free (RF) (WL 488 nm). Frequencies of choroidal abnormalities seen in IR, AF and RF were compared between patients and controls by Fisher’s exact test. The hypothetic diagnostic criterium "IR choroidal involvement" was tested with different settings (number of required abnormalities) by ROC curve, in order to obtain the best accuracy. We compared the accuracy of the proposed new criterium with those of each NIH criteria. P values of 0.05 or less were considered significant.

Results: : The mean age of the 95 NF1 patients was 28 years (range 3-68) and of the 100 healthy controls 30 years (range 4-72). VA and ophthalmic examination showed no differences between the two groups, except for the presence of Lisch nodules in 68 NF1 subjects. IR images showed bright patchy nodules in 79 NF1 patients (82%) and in 7 controls (7%) (P<0.001, Fisher’s exact test). The ROC curve of choroidal involvement showed the best accuracy (0.90; sensibility 0.83; specificity 0.8) when IR nodules are equal or more than 2.

Conclusions: : Choroidal involvement is frequent (82%) in NF1 patients, with prevalence similar to the more represented NIH diagnostic criteria. To date, this is the first large prospective controlled study on this issue. Two choroidal nodules are the threshold for the best diagnostic accuracy. Our data suggest that choroidal involvement may improve screening sensibility if added as new diagnostic criterium.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • genetics • choroid