This is a study whose focus is on understanding the clinical utility of rectal ultrastructure in detecting colonic neoplasm. The method uses Low-coherence Enhanced Backscattering Spectroscopy (LEBS).

The investigators use an optic probe which is a small device that uses light to assess the colon tissue. This probe will be used to identify subjects who do and do not have precancerous changes in the colon by capturing the light reflected back from the rectal wall and that will be assessed without the need for colonoscopy and bowel preparation (i.e unprepped). This device may detect early cancerous changes in colon tissue with higher accuracy than current tests.

Inclusion Criteria:

- Subjects are eligible if they were scheduled for colonoscopy for colon cancer screening or surveillance

Exclusion Criteria:

• age <50
• personal/family history of colonic neoplasia
• personal history of coagulopathy
• (retrospectively) failure to complete or inadequate colonoscopy
• any patients harboring non-pathoglocially normal rectum (i.e. presence of lesion, inflammation, polyp, adenomas at rectum)

The study population will be obtained in the gastroenterology clinics.

The investigators will assure the confidentiality of all human subjects' data and will adhere to all HIPAA rules by, for example, de-identifying data as appropriate to ensure compliance with human subject confidentiality requirements. The investigators will share research outcomes through conference presentations, and through publications as soon as is feasible after peer review.