Real-time anterior segment biometry and its relation to accommodative response

Abstract

 

Purpose

 

To determine the dynamic changes of the anterior segment and its accommodative response based on optical coherence tomography (OCT) and autorefractor.

 

Methods

 

An improved system based on our previously reported ultra-long scan depth optical coherence tomography (Du et al, Ophthalmology, 2012) was used with a CMOS camera and custom-designed Badal optometer system. An ultra-long scanning depth of 12.4 mm and an axial resolution of 9 μm in eye (assuming n=1.38) were achieved. A Badal optometer system with double optical path is coupled into the detecting light path to produce the certain stimulation. In each optical path, a Maltese cross fixation target illuminated by a white led is imaged through a relay lens (f=50mm) and a Badal lens (f=75 mm) successively. The virtual image was set at the far point of the eye and a near position in the two optical paths for non-accommodation and a certain ametropia, respectively. The OCT acquires 30 images in total and the led was switched at the 11th frame. The dynamic process of the eye from 0 D to -5.00D was recorded. A commercial autorefractor (Grand Seiko, WAM -5500) was also combined with the optometer system to measure the true accommodation response for the two states at the same accommodative condition. Five emmetropia eyes of 5 subjects (4 males, 1 female, aged from 25 to 32) were detected by the combined system.

 

Results

 

The entire anterior segment of all 5 eyes was successfully imaged and the accommodation response was measured when the Badal optometer switching (Figure 1). An accommodation hysteresis of about 0.4 s was observed. The thickness of crystalline lens increases and the anterior chamber depth and pupil diameters decrease as the accommodative response happening. For one subject, the variations of these parameters associated with the amount of accommodative response. Hence, the exact morphologic changes for a certain accommodative stimulation or response were shown.

 

Conclusions

 

By using the OCT system, autorefractor and switched double optical path optometer, our research demonstrated the quantitative relationship between the morphology of human anterior segment and the accommodative response value in real time.

 

 

Figure 1. Accommodative response curve (top) and the related morphologic parameters from OCT images (bottom) for a 24 year old female subject.

 

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