Changes of ocular aberration stability after correction with adaptive optics system

Abstract

Background The use of adaptive optics (AO) system in ophthalmic clinic and basic studies has increased in recent years.However, there are few reports on the stability of ocular aberrations after correction. Objective This study was to analyze the stability of aberration after correction by observing the repeatability of ocular aberration measurements. Methods Forty-one postgraduate school students and volunteers who meet the conditions were included from February to April 2014.The Zernike aberration coefficients including astigmatism (Z2-2, Z22), defocus (Z20), trefoil (Z33, Z3-3), coma (Z3-1, Z31), spherical aberration (Z40) and the value of root mean square (RMS) including 3rd-order to 7th-order aberrations, total higher-order aberrations (HOAs) and total ocular aberrations (TOAs) were measured by using AO system.The repeatability and stability of these data after corrected with AO system were analyzed.The repeatability was evaluated by ANOVA, within-subject standard deviation (Sw), repeatability (r) and intra-class correlation coefficients (ICC). The stability was evaluated by the nonparametric Friedman's rank test. Results AO system showed excellent repeatability on Z2-2, Z22, Z20 and TOA RMS (ICC>0.9), good repeatability on Z31, Z33, Z3-3, Z40, 3rd-order RMS, 4th-order RMS, HOA RMS (ICC>0.75), poor repeatability on Z3-1, 5th-order RMS, 6th-order RMS, 7th-order RMS (ICC<0.75). Repeatability (2.77 Sw) values ranged from 0.009 mm (7th-order RMS) to 0.163 mm (Z31). After low-order ocular aberrations were corrected, It was founded that Z2-2, Z22 reached stable state at the 4th second; Z20 was stable at the 6th second; Z3-3and Z33 reached stable state at the 4th second and third second, separately; Z31 was stable from 3rd-second to 9th-second, Z3-3 was stable at the 4th-second.Z40 and HOA RMS were stable at the third second and fifth second, respectively.The Z2-2, Z20, Z22, Z3-3, Z3-1, Z33, Z40 and HOA RMS were significantly different among different time points before and after low-order aberrations correction (all at P<0.05). Z2-2, Z22, Z20 reached stable state at the 4th-second, 3rd-second and 5th-second, respectively; Z3-3, Z33reached stable state at the 2nd-second and 3rd-second, respectively; Z3-1and Z40 reached stable state at the 2nd-second; HOA RMS reached stable state at the 5th-second. Conclusions After correcting the human ocular aberration, different aberrations can reach stable state at different time.The time of Z20, Z22, Z3-3, Z3-1, Z40 reaching stable state after 2nd-order to 5th-order ocular aberrations correction was earlier than those of lower-order aberrations correction. Key words: Adaptive optics; Wavefront aberration; Repeatability; Correction; Stability