Hrt Findings In The Affected Members Of A Large 11778 Lhon Pedigree in Brazil

Abstract

Abstract: : Purpose:To describe optic disc morphology in the Affected members of a large 11778 Leber’s Hereditary Optic Neuropathy (LHON) Brazilian pedigree with Heidelberg Retinal Tomography (HRT). Methods: Optic nerve morphology of 17 eyes out of 9 affected individuals with LHON were analyzed by HRT. All the individuals were male with a mean age of 35 years and showed very severe optic disc atrophy due to LHON. Eleven parameters of the optic disc were evaluated. Results: Mean visual acuity was 1.74 logMAR. Mean values for each parameter were: optic disc area 2.23 mm² [normal range (n.r.) 1.69–2.82], cup area 0.614 mm² (n.r. 0.26–1.27), rim area 1.616 mm² (n.r. 1.20–1.78), cup/disc area ratio 0.28 (n.r. 0.16–0.47), linear cup/disc 0.51 (n.r. 0.36–0.80), cup volume 0.1 mm³ (n.r. –0.01–0.49), rim volume 0.4 mm³ (n.r. 0.24–0.49), mean cup depth 0.21 mm (n.r. 0.14–0.38), maximum cup depth 0.51 mm (n.r. 0.46–0.90), cup shape measure –0.13 (n.r. –0.27––0.09), mean Retinal Nerve Fiber Layer (RNFL) thickness 0.243 mm (n.r. 0.18–0.31). Conclusion: We provided stereometric analysis of the optic nerve head in 9 individuals with severe optic atrophy as a consequence of LHON. The mean value of each morphological parameter was found to be within normal limits. Particularly, we found in this sample a cupping of lesser amount than reported by Mashima et al in 2003 in his study comparing LHON vs normal tension glaucoma. Also, while RNFL of this population was previously assessed with GDX and found to be always severely reduced, the mean volume of neuroretinal rim, as calculated by HRT, was within normal limits. Our preliminary data support the findings of Tedesco et al in 2003 that the combination of a normal HRT with abnormal GDX is highly suggestive of non–glaucomatous optic neuropathy. However, when dealing with the atrophic stage of an optic neuropathy, the HRT default reference plane, set by the factory at 50 microns below the RNFL at –7° temporally, may lead to underestimation of the cupping and of the loss of neuroretinal rim. Therefore, the issues of reference plane and of its customization, need to be addressed for a correct interpretation of the HRT findings in advanced optic atrophy.#

Keywords: imaging/image analysis: clinical • neuro–ophthalmology: optic nerve • optic disc