Detailed information on the status and function of photoreceptors in the retina is decisive for the evaluation of disease course and therapy monitoring. Newly developed gene therapeutic approaches make it necessary to develop precise and sophisticated diagnostic methods, especially regarding detection of early stages of hereditary retinal degenerations in very young patients. Fundus-controlled perimetry, two-color threshold perimetry, spectral sensitivity measurements and dark-adaptometry are highly informative parameters but are only partly suitable or of no use in young children below the age of 6 years. Chromatic pupillometry tests are valuable tools for detecting numerous dysfunctions of the retina, in particular, if full-field electroretinography testing is not able to display sufficient retinal function (e.g., advanced RPE65 retinal dystrophies). This diagnostic method requires a minimum of compliance, but only if the patient can wear specialized goggles with infrared cameras aimed to monitor the pupil reaction to stimuli.