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Polarimetric interferometry helps detect preclinical keratoconus changes
The same technology may provide guidance for optimal donor-recipient tissue alignment in corneal transplantation.
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An innovative imaging device that uses polarimetric interferometry to assess the orientation of collagen fibers within the corneal stroma may help detect some of the morphological changes that occur in the preclinical stages of keratoconus, allowing for early diagnosis and proactive treatment.
In addition, it may help optimize the visual results of corneal transplantation by suggesting the optimum alignment of stromal fibrils between the donor graft and the recipient bed.
Lumaxis (Phronema) is the only currently available medical device that images the birefringence properties of the cornea by using polarized light to identify the orientation of collagen fibrils within the stroma, Vito Romano, MD, senior clinical lecturer and consultant ophthalmic surgeon at the University of Liverpool, United Kingdom, said in an interview with Ocular Surgery News.
“It allows us to study these changes for the first time in people with several different conditions. This will open up important new areas of research and directly benefit our understanding of corneal disease in vivo,” he said.
Visualizing pathological changes
In the corneal stroma, the collagen fibers are arranged in regular layers for transparency and to maintain the strength and shape of the cornea. Keratoconus is a condition in which a progressive disruption in the orientation of the collagen fibers causes the cornea to bulge into a cone-like shape that prevents light from focusing on the retina.
“These changes only become evident later in the condition. If it were possible to detect them at an earlier time at the fibrils level, treatment could be offered and would be more effective,” Romano said.
The orientation of the fibers in a healthy cornea is visualized by the Lumaxis as a cross-like pattern. When pathological changes occur within the stroma, the cross pattern starts to modify. As the disease progresses, the center of the cross, which corresponds to the optical axis, moves away from the center and the arms become asymmetric and warp, until the cross pattern is no longer visible. These changes result in a progressive decrease of the optical quality of the cornea.
“This year at the [Association for Research in Vision and Ophthalmology] meeting in Vancouver, we presented a program, developed in Liverpool, able to numerically quantify the variations of the cross design and automatically discriminate between regular and altered corneal morphology, healthy eyes and eyes with keratoconus,” Romano said. “This grading system will allow us to diagnose keratoconus at a very early stage.”
Graft orientation
The way collagen fibers are arranged in the different areas and layers of the stroma determines the shape, transparency and optical quality of the cornea. Corneal grafting as well as refractive surgery and intrastromal implants may disrupt this orderly arrangement, negatively affecting light penetration and therefore quality of vision.
“We are utilizing the information provided by the Lumaxis to learn more on corneal structure and to find ways of potentially optimizing the visual outcomes of corneal surgery,” Romano said. “One lesson we are learning is that the orientation of the donor’s graft may be a factor of primary importance. The alignment of collagen fibers between donor and recipient creates a better path for the light to go through and therefore, theoretically, a better visual quality.”
If proved true, this principle could be applied to Descemet’s stripping endothelial keratoplasty, as well as PK and deep anterior lamellar keratoplasty.
“The idea of graft orientation is not new, but with this new technology, we can now use real-time imaging to scan the cornea of the donor and recipient and ensure that they are aligned during transplantation,” Romano said.
Once the preliminary stages of research are completed, a study will be carried out in patients to assess the clinical relevance of graft orientation for visual acuity. – by Michela Cimberle
- For more information:
- Vito Romano, MD, can be reached at University of Liverpool, Department of Eye and Vision Science, William Henry Duncan Building, 6 West Derby Street, Liverpool L7 8TX, UK; email: vito.romano@gmail.com.
Disclosure: Romano reports no relevant financial disclosures.