Background: Visual disturbances after high altitude exposure were first reported in 1969. Later, the term "High Altitude Retinal Hemorrhage-HARH" has been used for the ensuing retinal hemorrhages and vascular engorgement.
Case report: A 31-year-old Caucasian male presented to our outpatient department 1 week after climbing Mt. Gosainthan in the Himalayas. He had spent 25 days without oxygen supply above 5000 meters, with a maximum of 8046 meters. He now complained of glare and decreased vision in twilight. Visual acuity was 20/25 OD and 20/20 OS. Ophthalmoscopy revealed intraretinal hemorrhages and tortuosity of dilated arterioles and venoles. After 6 weeks of gradual improvement, visual acuity was 20/20 OD and 20/16 OS with normal visual fields.
Discussion: The hypoxia at high altitude causes increased retinal blood flow and blood volume possibly via autoregulatory mechanisms. Furthermore, retinal venous pressure can be increased by extreme physical exertion and Valsalva maneuvers during mountain climbing. A hypoxic retinal capillary bed exposed to increased retinal venous pressure predisposes to intraretinal hemorrhage. Retinal changes include marked increase of retinal vessel diameter with tortuosity of arterioles and venoles and hyperemia or edema of the optic disc. The intra- or preretinal hemorrhages often spare the macular area. These patients do not experience debilitating symptoms unless vitreous hemorrhage occurs. This may be potentially hazardous when the patient is still in the high mountains. Clinically, all these retinal changes are reversible within weeks. To prevent high altitude retinopathy, ascending slowly and use of supplemental oxygen is recommended.