Abstract
Purpose :
Individuals with mild traumatic brain injury (mTBI) exhibit significant accommodative abnormalities that can impair their near-work comfort and efficiency. Accommodative insufficiency is widely reported in mTBI patients who show significantly higher accommodative error (AE). Accommodation microfluctuation (AMF) plays an important role in the accommodation steady-state control mechanism. The purpose of this study was to investigate the impact of mTBI on the characteristics of the AMF.
Methods :
Monocular static accommodation was recorded continuously for 1 minute from 54 healthy (age 21-30 years) and 30 mTBI subjects (age 18-33 years) using Power Refractor 3 at 5 accommodative stimulus (AS) levels (0 to 5 D). The accommodative response (AR) data were processed using Fast Fourier Transform to determine the amplitude of high (HFC), medium (MFC), and low (LFC) frequency components of the AMF.
Results :
Consistent with previous reports, the amplitude of LFC increased as the AS increased in both groups (Fig 1a). However, mTBI subjects showed a significantly lower LFC amplitude than that of the control at higher AS levels (3 D – 5 D) (main effect F (1,78.7) = 8.56 (p< 0.01). Similar group effect was also observed for the HFC (F (1,77.9) = 5 (p= 0.028) (Fig 1b). Pairwise comparison revealed that the HFC amplitude was significantly lower in the mTBI than the control group for 2D, 3D, and 4D stimulus levels.There was no significant difference between groups for the amplitude of the MFC. Interestingly, a strong correlation between the AE and the LFC of AMF was revealed for all AS levels (except 0D) in both groups (Fig 2). Lead of accommodation (AE< 0) was associated with higher LFC amplitude, and lag of accommodation (AE > 0) was associated with lower LFC amplitude. No correlation between the AE and MFC or HFC was observed.
Conclusions :
Our data is the first to show impairment of AMF in subjects with mTBI. Both the LFC and HFC showed significantly lower AMF amplitude compared to the control group. The magnitude of LFC was correlated with AE in both groups, suggesting that AMF may be influenced primarily by the changes in the motor output properties of the accommodation plant with increasing accommodation response.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.