First Author: H.Tan TAIWAN
Co Author(s): W. Lo W. Chen C. Hseuh S. Chen D. Ma C. Dong
Purpose:
To qualify and quantify structural alterations in keratoconic corneas ex vivo by the use of second harmonic generation (SHG) microscopy and two-dimensional fast Fourier transform (2D-FFT) analysis.
Setting:
National Taiwan Univeristy/Chang Gung Memorial Hospital, Taiwan
Methods:
Two keratoconic and three normal human corneal specimens were imaged with a multiphoton microscope. Forward and backward second harmonic generation imaging (FSHG and BSHG) of corneal stroma was obtained at high resolution and at different depths. The SHG images are further analyzed with 2D-FFT algorithm in order to quantify the texture and orientation changes of collagen fibers.
Results:
Our results show that the abnormality of collagen architecture is found through the whole layer of stroma. 2D-FFT analysis of SHG cornea images provides fiber orientation direction and an aspect ratio (AR) for quantitative measure of fiber direction determination. We find that for keratoconic cornea the average AR values are statistically greater than that of the normal cornea: 1.66±0.42 (Case I keratoconic cornea), 1.72±0.44 (Case II keratoconic cornea) , and 1.34±0.16 (average of three normal human cornea). Furthermore, the fiber direction determined by 2D-FFT analysis of BSHG and FSHG images are strongly correlated for large AR values (AR>2).
Conclusions:
The high correlation between FSHG and BSHG fiber direction for large AR values shows that BSHG imaging can provide qualitative and quantitative information of the extent of structural changes in a keratoconic cornea. The ability to use BSHG for diagnosing and monitoring stroma abnormalities even when cornea transparency is retained demonstrates the clinical potential of our method. FINANCIAL DISCLOSURE?: No
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