Dynamic changes of anterior segment biometry and aberrations during accommodation in real-time

Abstract

 

Purpose

 

To determine the dynamic changes of the human anterior segment and high order aberrations (HOAs) during accommodation based on spectral domain optical coherence tomography (SD-OCT) and wavefront sensor.

 

Methods

 

A scanning depth of 12.4 mm and an axial resolution of 9 μm in eye were achieved by the CMOS based ultra-long scan depth SD-OCT system. The Shark-Harttman wavefront sensor with 32 × 32 microlens array was combined with the OCT system to obtain ocular wavefront aberrations synchronously. A Badal optometer system with dual optical path is introduced to realize the switch from non-accommodation to -3.00 D accommodation at 1.25 second after the start. Thirty frames of anterior segment OCT images were acquired in 6 seconds, and 100 frames of wavefront maps were obtained in 3.5 seconds. The visible fixation was switched from non-accommodative state to accommodative state 1.25 second later. Three emmetropia eyes of three subjects (1 male, 2 female, aged from 25 to 35) were detected by the combined system.

 

Results

 

The dynamic changes of entire anterior segment biometry and ocular wavefront were successfully acquired during the accommodation from 0 D to -3.00 D in real time. As shown in Fig. 1, when the accommodative stimulation was induced by the optometer, the thickness of crystalline lens increases, as well as the anterior chamber depth and pupil diameters decrease. However, the HOAs RMS changes in a complex way. The accommodation process can be divided into two phases: the RMS value increases in phase 1, but decreases on the contrary in phase 2. The RMS finally trends to be stable, indicating the finish of the accommodation. The two-phase dynamic process was found in all three subjects, as listed in table 1.

 

Conclusions

 

Our research demonstrated the feasibility of quantifying the dynamic relationship between the morphology of human anterior segment and the HOAs during accommodation. The two-phase dynamic process of aberrations reveals that the eye overreacts and adjusts immediately during the accommodation.

 

 

Fig 1. Dynamic changes of high-order aberration RMS (top) and the related morphologic parameters of anterior segment by OCT images (bottom) for a subject #3. PD: pupil diameter; ACD: anterior chamber depth; CLT: crystalline lens thickness.

 

 

Table 1. The changes of the anterior segment morphologic parameters and HOAs from non-accommodation to -3D accommodation for three subjects.

 

Keywords: 421 anterior segment • 404 accommodation • 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)