Central retinal vein obstruction and axial length.

The axial lengths of 24 consecutive adult eyes with unilateral central retinal vein obstruction (CRVO) were compared with those of contralateral unaffected eyes and those of a control population. The lengths of the two eyes of persons with a unilateral CRVO were not significantly different. By contrast, eyes of persons with CRVO averaged 0.67 mm (approximately 2 diopters) shorter than their control counterparts (P = .03). This anatomic difference may be a factor in the development of CRVO.

Peripheral proliferative retinopathies.

The cases of 100 consecutive persons (156 eyes) seen with peripheral proliferative retinopathy were reviewed in a retrospective fashion. Associated systemic and ocular diseases included sickling hemoglobinopathies (49%), branch retinal vein obstruction (20%), diabetes mellitus (9%), sarcoidosis (4%), intravenous drug abuse (4%), the ocular ischemic syndrome (1%), pars planitis (1%), Coats' disease (1%) and retinitis pigmentosa/retinal detachment (1%). In ten (10%) patients no obvious cause for the development of new blood vessel growth could be ascertained.

Renin and aldosterone at high altitude in man.

Measurements have been made of hormonal changes relevant to salt and water balance during prolonged exposure to hypoxia to improve our understanding of the syndrome of acute mountain sickness. We have attempted to delineate the detailed inter-relationships between the renin-aldosterone and the vasopressin systems by a metabolically controlled study, involving an orthostatic stress (45 degrees head-up tilt) and an injection of a standard dose of ACTH to test adrenal responsiveness. Three Caucasian medical students underwent a 7-day equilibration at 150 m (Lima, Peru), followed by a 6-day sojourn at 4350 m (Cerro de Pasco, Peru) and a final 7 days at 150 m. Measurements were made of sodium and potassium balance, body weight and the 24-h renal excretion of vasopressin, cortisol and aldosterone 18-glucuronide. These variables showed little change, except for that of aldosterone 18-glucuronide, which fell sharply at altitude and rebounded even more sharply on return to sea level. At altitude, basal plasma levels of renin activity and aldosterone fell, and the response to orthostasis was attenuated, but the fall of plasma renin activity, as compared to plasma aldosterone, was delayed; on return to sea level this dissociation was exacerbated with the return of normal renin responsiveness lagging behind that of aldosterone. We suggest that unknown factors which dissociate the orthodox renin-aldosterone relationship, other than the activity of the angiotensin I-converting enzyme, are operative on exposure to hypoxia.