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Second-harmonic imaging microscopy of normal human and keratoconus cornea
Naoyuki Morishige1, Andrew J Wahlert, M Cristina Kenney
1The Eye Institute, School of Medicine, University of California Irvine Medical Center, Orange, California.
Investigative Ophthalmology & Visual Science
|February 28, 2007
Summary
Second-harmonic imaging reveals significant differences in corneal collagen organization between normal and keratoconus corneas. This advanced imaging technique highlights structural abnormalities in keratoconus, particularly in the anterior stroma.
Area of Science:
- Ophthalmology
- Biomedical Optics
- Tissue Engineering
Background:
- Keratoconus is a progressive thinning disorder of the cornea.
- Corneal stromal collagen organization is crucial for maintaining corneal shape and biomechanical strength.
- Current methods for assessing corneal structure have limitations.
Purpose of the Study:
- To evaluate the efficacy of second-harmonic imaging in differentiating collagen organization between normal and keratoconus corneas.
- To investigate the detailed 3-D structure of corneal lamellae using this advanced imaging technique.
Main Methods:
- Second-harmonic imaging using a femtosecond titanium-sapphire laser was performed on normal (n=6) and keratoconus (n=13) corneal tissues.
- Three-dimensional (3-D) data sets were collected and reconstructed to analyze lamellar location and orientation.
- Corneal tissue blocks were examined from central and paracentral regions.
Main Results:
- Normal corneas exhibited highly interwoven lamellae, especially in the anterior stroma, with some lamellae inserting into Bowman's layer.
- Keratoconus corneas showed reduced lamellar interweaving and a significant loss of lamellae inserting into Bowman's layer in most cases.
- These structural changes were observed even without breaks in Bowman's layer or scarring.
Conclusions:
- Second-harmonic imaging effectively detects marked abnormalities in anterior corneal collagen lamellar organization in keratoconus.
- The observed structural differences correlate with known alterations in collagen organization and biomechanical properties of keratoconus corneas.
- This imaging modality offers a promising tool for understanding and potentially diagnosing keratoconus.
