It is unclear what role vision plays in guiding mouse behaviour, since the mouse eye is of comparably low optical quality, and mice are considered to rely primarily on other senses. All C3H substrains are homozygous for the Pde6b(rd1) mutation and get blind by weaning age. To study the impact of the Pde6b(rd1) mutation on mouse behaviour and physiology, sighted C3H (C3H.Pde6b+) and normal C3H/HeH mice were phenotyped for different aspects. We confirmed retinal degeneration 1 in C3H/HeH mice, and the presence of a morphologically normal retina as well as visual ability in C3H.Pde6b+ mice. However, C3H.Pde6b+ mice showed an abnormal retinal function in the electroretinogram response, indicating that their vision was not normal as expected. C3H.Pde6b+ mice showed reduced latencies for several behaviours without any further alterations in these behaviours in comparison to C3H/HeH mice, suggesting that visual ability, although impaired, enables earlier usage of the behavioural repertoire in a novel environment, but does not lead to increased activity levels. These results emphasize the importance of comprehensive behavioural and physiological phenotyping.