Surround Propinquity and Tonic Accommodation

Title Surround Propinquity and Tonic Accommodation
Author, Co-Author Tammy Nguyen, Lawrence Stark
Topic Functional Vision/Pediatrics
Program Number
Ballroom A-B

Purpose: Previous studies have found evidence of a propinquity response, in which subjects accommodated based on perceived proximity of their surroundings despite being in absolute darkness. This study sought to establish the magnitude of the propinquity response in a large sample of young adults, and to determine whether the propinquity response can be predicted by a subject’s initial naïve dark focus in an unknown room.

Methods: Accommodation was recorded using a dynamic infrared optometer (Plusoptix Power-Ref 3). Initial dark focus was measured in 30 young adults, 26 of whom were naïve to the testing room. Dark focus was then measured at five wall distances in the range 0.25–4 D in randomized order. Subjects were initially given no information about the purpose of the study, and were given instructions to look straight ahead during trials. Dark focus was plotted as a function of dioptric wall distance, and the slope of the function used as a measure of the propinquity response.

Results: The mean initial dark focus value was 1.05 D for the 26 naïve subjects, with a range of −0.67 D to 4.19 D and a s.d. of 1.04 D. The propinquity response slope was significantly different from zero (mean +0.097, p = 0.0002; range −0.122 to +0.433). No statistically significant correlation was found between naïve dark focus and propinquity response (r = +0.246, p = 0.226).

Conclusions: Propinquity is a small but significant factor in dark focus measurements. Though it is unlikely to contaminate laboratory measures of tonic accommodation in large subject samples, we cannot discount “responder” subjects who exhibit large propinquity responses. While naïve dark focus does not appear to predict the propinquity response, additional factors such as voluntary accommodation and cognitive task require further investigation.

Affiliation of Co-Authors Southern California College of Optometry at Ketchum