[Alterations in nocturnal melatonin secretion in patients with optic neuropathies]

To study nocturnal melatonin suppression induced by exposure to light in patients with bilateral optic neuropathies.

Observational, prospective case control study. Twenty patients were included in this study and distributed in 3 groups: Group A (n=5, Healthy Control Subjects), Group B (n=10, Experimental Patients) and Group C (n=5, Blind Control Subjects). LogMAR best-corrected visual acuity, standard automated perimetry mean deviation, retinal nerve fiber layer thickness by Optical Coherence Tomography and multifocal electroretinograpy (mfERG) were used to evaluate the changes. Melatonin was analysed in the saliva by radioimmunoassay after exposure to light (600 lux for 1 hour) (nocturnal melatonin suppression test).

Statistically significant differences between the groups were found. No changes in the mfERG results were detected. The nocturnal melatonin suppression test was positive in all cases in Group A, 50% in Group B and none in Group C.

Half of the patients with optic neuropathies and severe visual loss were shown to suffer significant melatonin regulation anomalies, probably due to the dysfunction of the intrinsically photosensitive retinal ganglion cells (ipRGC).