Investigation of retinal function in chronic systemic hypoxia secondary to cardiac disease in human

Abstract

 

Purpose

 

To study retinal electroretinographic function in chronic systemic hypoxia in patients with cyanotic cardiac disease.

 

Methods

 

The study included 12 patients with cyanotic cardiac disease and 7 healthy subjects, all with normal visual acuity, who underwent clinical examination, fundus photography, infrared photographic retinal vessel oximetry, full-field electroretinography (ffERG) and dark adaptometry.

 

Results

 

In contrast to healthy subjects, who have subnormal full-field electroretinography amplitudes during acute hypoxia, patients with chronic systemic hypoxia (mean oxygen saturation 88 %) had ffERG amplitudes and latencies comparable to those of normoxic healthy subjects (oxygen saturation 95-100%). Thus, the scotopic A-wave amplitude was 251 ± 50.5 µV in patients and 245 ± 68 µV in healthy subjects (p = 0.80). The fractional arteriovenous oxygen extraction was 37 ± 6% and 34 ± 5%, respectively (p= 0.29). There was no significant correlation between A- or B-wave amplitudes or latencies under scotopic or photopic conditions and oxygen saturation (p> 0.05), except that the amplitude of the scotopic A-wave increased with oxygen saturation (R = 0.61, p = 0.035). No microvascular retinopathy signs such as retinal hemorrhages were observed.

 

Conclusions

 

Chronic systemic hypoxia appears to be counter-regulated by physiological adaptation that may hypothetically involve elevated hematocrit, elevated oxygen extraction and increased reliance on glycolysis etc. The elucidation of the mechanisms of adaptation may promote the understanding of conditions such as altitude retinopathy and diabetic retinopathy.