Preservation of photic blink reflex in Leber's hereditary optic neuropathy.

PURPOSE To examine whether the early response of photic blink reflex (PBR) is spared in patients with Leber's hereditary optic neuropathy (LHON). METHODS Twenty-six patients with bilateral optic neuropathy (visual acuity < or = 0.1) and central scotomata were divided into LHON group with one of three mitochondrial DNA mutations at nucleotide position of 3460, 11778, or 14484 and non-LHON group without them. Latencies of the PBR early response and those of the electrically evoked blink reflex (EBR) response were compared among the 26 patients and 20 healthy volunteers. RESULTS In controls, average latency of the PBR response was 50.3 +/- 2.4 msec and was in accordance with previous reports. Ten of eleven patients with LHON had normal PBR responses, whereas 12 of 15 controls without LHON had abnormal responses (P = 0.0005). Latencies of EBR responses were normal in all but one patient with LHON. CONCLUSIONS The afferent fibers of the PBR early response, as well as those of the light reaction, are reported to terminate presumably in the pretectum. Together with the reported evidence of the preserved light reaction in patients with LHON, we presume that W retinal ganglion cells may project common afferent fibers of these two neuronal pathways and may be preferentially spared in patients with LHON.