In the clinical setting, refractive error is corrected by prescribing spectacles or contact lenses on a daily basis. Typically the patient will first undergo autorefraction, in which a computer-controlled machine is used to objectively calculate the refractive error present as a starting point for the subjective refraction test. This machine, however, is cumbersome and not easily transportable abroad. Typically the machine is held up to the patient's forehead and they are asked to look into the machine at a distant object. While they are looking at this object the machine calculates the refractive error. Next, the patient undergoes manifest refraction, a subjective refractive test that requires the use of trial lenses and patient responses to improve the results calculated by autorefraction, resulting in the best corrected visual acuity for that patient and a prescription for the patient to receive spectacles tailored to their need.