web analytics

Description

The trunk diameter ratio (TDR) for retinal arterioles compares an arterioles actual diameter with that predicted from its branches using the Parr equation (see previous section).


 

Arteriole selection: trunk arterioles >= 80 microns in diameter

 

trunk diameter ratio =

= (observed trunk diameter in microns) / (predicted trunk diameter from its branches)

Ratio

Interpretation

< 1

the trunk is small relative to the branches, either due to constriction of the trunk and/or passive dilatation of the branches

1

the trunk and branches are proportionate (normal)

> 1

the trunk is large relative to the branches, either due to constriction of the branches and/or passive dilatation of the trunk

 

A mean TDR can be calculated for one or both eyes. Sharrett et al calculated the mean using arterioles with a diameter of 80 – 99 microns.

 


To read more or access our algorithms and calculators, please log in or register.