Abstract
Purpose :
To determine relationships between accommodation-induced changes in ciliary muscle parameters, peripheral choroidal thickness, peripheral axial length. We hypothesized that changes in ciliary muscle parameters and in choroidal thickness are correlated.
Methods :
There were 29 young adults aged 18 and 27 years. All had good ocular and general health. Measurements of right eyes were made for 0 D and 6 D stimuli to accommodation at both nasal and temporal locations.
Axial length AL was measured with a Lenstar LS 900 biometer (Haag-Streit, Switzerland), with an auxiliary system to allow eye rotation in 10° steps to ±30°. Participants turned eyes without head movement to fixate targets and to make the target “as clear as possible” during measurements. Choroidal thickness CTh was measured with the Nidek RS-3000 Advance spectral-domain (SD)-Optical Coherence Tomography (OCT) in 10° steps to ±30°. For peripheral images, the internal cross target on the capture screen was moved from the centre to 17.25° nasal/temporal positions. Ciliary muscle length CML and maximum thickness were determined by imaging ciliary bodies of right eyes with a Carl Zeiss Meditec Visante OCT and an external fixation target placed at 40° to the instrument axis.
Changes in AL, CTh, CML and CMT with accommodation were denoted as ΔAL, ΔCTh, ΔCML and ΔCMT. For each participant, the three ΔCTh on each retinal side were averaged for comparison with corresponding muscle parameters.
Results :
Nasal ΔCMT and ΔCML mean±SEs were 88±19 and −89±34μm, respectively. Corresponding temporal changes were 82±20 and −111±57μm.
Fig. 1 shows correlations between ΔCTh and ΔCMT on the nasal (r 0.30, p 0.13) and temporal (r 0.31, p 0.19) sides, neither of which were significant. Neither ΔCTh v. ΔCML correlation was close to significance (p 0.87, 0.89).
Fig. 2 shows ΔAL and ΔCTh as a function of visual field position; error bars are standard errors. ΔAL was greater than −ΔCTh at all positions. Maximum changes occurred on-axis Correlations were non-significant at all positions.
Conclusions :
Individual parameters changed in expected directions with accommodation: AL, CMT increased; CTh, CML decreased. However, correlations between changes in parameters were not significant. This may be because of considerable variation between individuals and because individual accommodation responses were not the same for all instruments.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.