An eye-mountable device, EMD, (100, 200, 620, 670) comprising: an enclosure material (110, 210); a sensor system (135, 235, 305, 500, 550, 600, 650) disposed within the enclosure material, the sensor system including: a first circuit (510, 560, 700, 740) coupled to generate a first signal (514, 564, 730, 770) based on light received at a first photodiode, PD, (512,562,645,695, 710, 750) of the first circuit, wherein the first circuit is configured to provide a first light response profile that is non-linear such that there is a non-linear relationship between a magnitude of the first signal and a level of light received at the first photodiode; and a second circuit (520, 570, 800) coupled to generate a second signal (545, 595, 830) based on light received at a second PD (522, 572, 640, 690, 810) of the second circuit, wherein the second circuit is configured to provide a second light response profile that is linear such that there is a linear relationship between a magnitude of the second signal and a level of light received at the second photodiode, wherein the sensor system is adapted to configure the second circuit based on the first signal so as to change the second light response profile provided by the second circuit; and evaluation logic (540, 590) coupled to the sensor system, the evaluation logic configured to detect, based on the second signal, a direction of gaze by a cornea. an enclosure material (110, 210); a sensor system (135, 235, 305, 500, 550, 600, 650) disposed within the enclosure material, the sensor system including: a first circuit (510, 560, 700, 740) coupled to generate a first signal (514, 564, 730, 770) based on light received at a first photodiode, PD, (512,562,645,695, 710, 750) of the first circuit, wherein the first circuit is configured to provide a first light response profile that is non-linear such that there is a non-linear relationship between a magnitude of the first signal and a level of light received at the first photodiode; and a second circuit (520, 570, 800) coupled to generate a second signal (545, 595, 830) based on light received at a second PD (522, 572, 640, 690, 810) of the second circuit, wherein the second circuit is configured to provide a second light response profile that is linear such that there is a linear relationship between a magnitude of the second signal and a level of light received at the second photodiode, wherein the sensor system is adapted to configure the second circuit based on the first signal so as to change the second light response profile provided by the second circuit; and a first circuit (510, 560, 700, 740) coupled to generate a first signal (514, 564, 730, 770) based on light received at a first photodiode, PD, (512,562,645,695, 710, 750) of the first circuit, wherein the first circuit is configured to provide a first light response profile that is non-linear such that there is a non-linear relationship between a magnitude of the first signal and a level of light received at the first photodiode; and a second circuit (520, 570, 800) coupled to generate a second signal (545, 595, 830) based on light received at a second PD (522, 572, 640, 690, 810) of the second circuit, wherein the second circuit is configured to provide a second light response profile that is linear such that there is a linear relationship between a magnitude of the second signal and a level of light received at the second photodiode, wherein the sensor system is adapted to configure the second circuit based on the first signal so as to change the second light response profile provided by the second circuit; and evaluation logic (540, 590) coupled to the sensor system, the evaluation logic configured to detect, based on the second signal, a direction of gaze by a cornea.