Abstract Details Title Observation of Angular Deformity of a Straight Line Topic Neuro-ophthalmology/Neuro-otology Presentation(s) P1 - Poster Session 1 (5:30 PM-6:30 PM) Poster/Presentation Number 4-016 Objective This simple study was designed to assess the human eye's perception of a line as either straight or non-straight using bent lines in a survey format. Background This fundamental principle of human perception could have wide-reaching effects. One such example could be the diagnostician’s ability to see a pathological bend in a bone on a radiograph. Could a small bend of 1° cause a pathology that would be missed by the human eye on imaging? How often should radiologists use superimposition of an apparatus to detect what appears to be straight or deviated? To answer these questions there must be a knowledge of what angle of deviation the human eye can normally see. Design/Methods The survey was created using 20 questions made from a random sample of 49 possible deviated lines with 0.5° degree increments of deviation from 0°-6°, 10°, and 30°. Results The survey showed that all 109 respondents could determine that an angle above 2.5° was non-straight consistently. Below this, the accuracy of the respondents depended directly on the degree of deviation with the lowest angle (0.5°) having 29.36% and the highest angle (2.5°) having 98.62% of the respondents determining that the line was non-straight. Conclusions Between 1° and 1.5° of deviation is where the largest jump occurs (from 46.79% to 86.24%). These findings suggest that the normal human eye can accurately distinguish angles of 2.5° and above from straight lines 100% of the time, but has poorer perception at lower angles. Authors/Disclosures Bradley J. Tishman PRESENTER No disclosure on file No disclosure on file