The Emerging Controversy of Chronotherapy: Nocturnal Hypotension and Non-Arteritic Ischemic Optic Neuropathy

‘Blindness upon awakening' occurs in a significant proportion of patients with non-arteritic anterior ischemic optic neuropathy (NAION). This observation has lead to a notion that nocturnal hypotension is a significant contributor factor to the development of NAION, as has been proposed in other ischemic events like strokes, myocardial infarction, and ischemic rest pain. Hayreh's 1994 and 1999 prospective studies of NAION reported an extreme dipping pattern in nocturnal systolic blood pressure compared to reported normal values. An extension of this concept has lead to the recommendation that patients who have experienced NAION should avoid taking blood pressure medications at bedtime. Two other studies, however, did not find a similar extreme dipping pattern in NAION patients. Furthermore, mounting evidence in the cardiology literature suggests that nocturnal hypertension is associated with increased risk of cardiovascular morbidity, which has lead to a recommendation for nocturnal antihypertensive dosing, contrary to Hayreh's recommendation. This review will highlight this emerging controversy.