OPTICAL COHERENCE TOMOGRAPHY (OCT) AND ITS PRINCIPLE

BY Ashish chaudhari

Introduction

OCT is an imaging device used to high resolution cross section images of retina.

Non contact device with 3-D imaging Analogous to ultrasonography Measures reflected lights from

different layers of retina. Indications: CME,ARMD, CSR,

macular holes, PVD,ERM ,SRF ……

Principle

Based on low coherence interferometryBasic Parts of OCTLight sourceBeam splitterReference mirrorDetector ClassificationTime-domain OCT (TD OCT)Spectral domain OCT ( SD OCT)

TD OCT

Beam splitter

moving

SD OCT

Difference between TD and SD OCT TD OCT SD OCT

1. Based on reflectometer

2. Early version3. Slow and mechanical4. Moving reference mirror5. Resolution approx. 400 A-

scans per second6. Poor Image

1. Based on fourier transformation of spectrometer analysis

2. New version3. Faster and non mechanical4. Stationary reference mirror5. Resolution approx. 40,000

A-scans per second6. Better image

A Normal retina