The purpose of this study is the development of a physiologic endpoint using a novel technology that would provide an objective, easy to use and more sensitive assessment of VIPN in children and adolescents. The ability to more easily detect and monitor VIPN, even before it is clinically evident, would facilitate optimizing the dosing of vincristine for maximal disease response while minimizing the risk of lifelong functional deficits affecting quality of life. This approach would also enable the development of specific therapies to minimize or eliminate the occurrence of VIPN in children and adolescents. This is a single site study that aims to develop a novel device to evaluate and characterize vincristine-induced neuropathic pain. The investigators will enroll patients with ALL following the Delayed Intensification (DI) phase of treatment. At each study visit, the investigators will evaluate the nPRD as well as the TNS-PV. The nPRD will inform the neuropathy index which will be used to compare to the TNS-PV. We anticipate a correlation between the two.

Inclusion Criteria:

• 6-18 years of age at the start of the study, are receiving vincristine in DI (clinical study population) and are willing and able to provide informed consent or assent to study participation.

Exclusion Criteria:

• have eye pathology which precludes pupillometry, are hemodynamically unstable, or are pregnant.

30 patients and 10 healthy volunteers will be enrolled for this study.