Automatic axial biometry of the whole eye using ultra-long scan depth optical coherence tomography

Abstract

 

Purpose

 

To develop and test novel spectral domain optical coherence tomography (SD-OCT) for automatic axial biometry of whole eye.

 

Methods

 

The system was improved based on our previously reported ultra-long scan depth SD-OCT (Du, et al, Ophthalmology, 2012) by using a CMOS camera and special design optic switch in the reference arm. Using the alternation of 4 reference mirrors, 4 images were acquired. The first two images with two mirrors were used to scan the anterior segment up to 12.57mm with the zero-delay lines placing on the top of the cornea and the posterior surface of the crystalline lens. Overlaying these two images resulted in the enhancement of image quality. The rest two reference mirrors provide the scan depth up to additional 25mm which was enough for imaging the vitreous and retina (Fig. 1). A model eye with known geometric parameters was imaged for verification. Six eyes of 6 human subjects were measured in two separate sessions. The images were processed by a manual method and custom developed automatic software. In addition, these 6 subjects were imaged using IOLMaster for the axial length measurement.

 

Results

 

The measurement of the model eye matched the known parameters and had no statistically significant differences (P > 0.05). The axial length of the eye matched the results by IOLMaster (Table 1). There were no significant differences between two measurements in any measured parameters. The repeatability (CoR) ranged from 0.44% to 3.35%. Compared to manual results, automatic results showed a very small difference in axial length. The largest difference between two methods was the lens thickness.

 

Conclusions

 

We demonstrated the improved OCT system for imaging the whole eye with automatic biometry software. This system may be well suitable for studying the biometric changes in accommodation and the calculation of IOL power.

 

 

 

Keywords: 552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • 549 image processing • 497 development