There was no device to grade visual function in patients with retinitis pigmentosa (RP). We have therefore developed an instrument capable of measuring and quantifying the visual capabilities, and here present the results from patients with RP. In total, 118 eyes of 59 patients, 26 men and 33 women, with RP were studied. Seven eyes had hand movement (HM) and eight had light perception (LP) vision, and the others had better visual acuity. The Low Vision Evaluator (LoVE) consists of a pair of goggles with white, light-emitting diodes as the stimulus, a control box, an on-off button to signal the detection of the stimulus, and a printer for permanent records. There are 15 luminance levels of stimuli (combination of 5 intensities and 3 durations). The stimuli are delivered in a random sequence with an audio signal presented 0.3 seconds prior to the light stimulus. Each eye was tested separately, and each stimulus magnitude (intensity x duration) was presented 3 times for a total of 27 stimuli per eye. With 6 catch trials (audio signal without a light stimulus), a total of 60 trials were examined in a full examination. The conventional visual acuity and kinetic visual fields were determined. 59 patients had different visual acuities that ranged from no light perception (NLP) to 1.5 vision, and visual field sizes that ranged from 0.0001 to 3.96 steradians. The visual acuity and visual field size were significantly correlated with the LoVE score (r=0.58 and 0.64, respectively; p<0.01). These results indicate that the LoVE is capable of grading the visual function of RP patients with various visual acuities and visual fields. The testing procedures are simple for the patient and examiner, and this instrument can be used to assess the effectiveness of medical and surgical therapy.