The light streak on retinal vessels

The intensity profiles of the central light streak on various sized retinal vessels were measured by a computerized high quality scanning microphotometer. From the fundus photographs in 40 young men 240 arteries and 240 veins were analysed, and light streaks were found on 171 arterial and 170 venous sites. Differences in reflected intensities between arteries and veins and between small and large vessels were studied. In the whole range of vessels measured (50-200 microns) significantly higher intensities were found on arteries compared to veins (P less than 0.01). Large vessels (100-200 microns) reflected the light more intensely than small vessels (50-99 microns) (P less than 0.001). Variations in haemodynamics of flow and in physical properties of the streaming erythrocytes might account for the reflectivity differences between arteries and veins.

The intensity of the light reflex on retinal arteries and veins

Brinchmann‐Hansen¹,

Sandvik

1986

The light reflex in retinal vessels and its relation to age and systemic blood pressure

Brinchmann‐Hansen¹,

Myhre

Sandvik³

1987

The light streak characteristics on retinal vessels were studied by microdensitometry on fundus photographs. We compared the width and the intensity of the reflex in a young group (mean: 19.7-year-old; n = 40) and in an older group (mean: 45.3-years-old; n = 22) of normal subjects. By subgrouping according to age and blood pressure levels, we studied possible effects of these parameters on the light streak. We found higher intensity of reflection from both arteries and veins in the older group (P less than 0.01). This effect seemed mostly related to the age of the subjects. We also registered a relation between systolic blood pressure and intensity of reflection from veins in the young group (P less than 0.03). Optical changes in the vessel walls in the ageing process and intravascular pressure effects on the indices of refraction in the erythrocytes/plasma may account for these findings. The width of the reflex was not found to be related to either the age or the blood pressure level of the subjects.

The effect of hypoxia on the central light reflex of retinal arteries and veins

Brinchmann‐Hansen

Myhre²

1989

Computerized scanning microdensitometry was used on fundus photographs of 40 men (aged 18-23 years) and effects of hypoxia on intensity profiles of the 'light reflex' in 140 arteries and 138 veins were analysed. Changes from sea level to four levels of acute hypoxia of simulated altitude were studied: 8000 feet (ft) (2438 meters) (m), 10,000 ft (3048 m), 12,500 ft (3810 m), and 15,000 ft (4572 m) using a low-pressure chamber. The intensity of the reflex increased at 12,500 ft and 15,000 ft by 24% (P less than 0.05) and 39% (P less than 0.01) in arteries and 50% and 33% in veins (P less than 0.05), respectively. As an overall response from sea level to all four altitudes, the width of the reflex was reduced. The reduction in width was negatively correlated to the diameter of the arteries (P less than 0.0001) and veins (P less than 0.001) at sea level, and the variability of changes was larger in veins (P less than 0.01). Funduscopic light reflected from intravascular blood columns of retinal vessels is thus influenced by hypoxic stress, and 12,500 ft of simulated altitude represents a threshold value of circulatory interest.