The shape of the sclera, or the white part of the eye, can lead to serious complications and even blindness. Unfortunately, current methods for observing the detailed structure of the sclera, including its fibrous makeup, are limited. However, researchers have now employed polarization-sensitive optical computed tomography to effectively examine the density and alignment of scleral fibers in the eyes of living patients. This breakthrough has the potential to improve our understanding of eye diseases and pave the way for better diagnostic and treatment approaches.
Eye diseases are extremely prevalent worldwide, with recent estimates suggesting that one-third oApproximately one-fifth of the global population has some form of vision impairment. Due to the intricate nature of the human eye, the exact cause and characteristics of many eye diseases remain unknown, which limits the options for diagnosis and treatment for affected individuals.
A recent study, available online on March 7, 2024 and published in Volume 142, Number 4 of JAMA Ophthalmology on April 1, 2024, conducted by a team of researchers from Tokyo Medical and Dental University (TMDU) in Japan, has introduced a new type of optical coherence tomography (OCT) to the field. This technique, commonly used in clinical ophthalmology, has been developed for investigative purposes.The focus of this research is to examine the intricate structure of the sclera, the outer white layer of the eyeball. The reason for conducting this study is the limited methods available to eye doctors for studying the detailed features of the sclera in both living patients and specimens. Dr. Kyoko Ohno-Matsui, the lead author, highlights the importance of the sclera, which is made up of collagen fibers and serves a crucial role in protecting the retina, optic nerve, and other nerve tissues in the eye. Any abnormalities in the shape of the sclera can lead to a range of complications that may result in blindness. Up until now, the sclera of living subjects has only been measured in a limited capacity.In terms of thickness, it’s difficult to see details like the orientation of collagen fibers over a wide area of the eye. To address this issue, the researchers created a system for conducting polarization-sensitive OCT (PS-OCT), a method that uses the polarization of light as a way to enhance contrast. “The sclera exhibits a property known as birefringence, which is an optical characteristic where the refractive index depends on polarization. Birefringence is commonly found in fibrous tissues with regularly organized nanostructures, like the sclera,” explains senior author Dr. Tae Igarashi-Yokoi. Therefore, inIn addition to measuring birefringence magnitude for fiber density information, PS-OCT can also reveal the orientation axis of birefringence, which is connected to the alignment of the fiber bundles themselves.”
By using this method, the research team examined the characteristics of collagen fibers in the sclera of patients with high myopia. They also focused on the relationship between myopia and a condition called dome-shaped macula (DSM), in which a specific area in the retina protrudes. Their study involved 89 highly myopic eyes from 72 patients, primarily adults overThe researchers, who are 50 years old, carefully examined the PS-OCT images they obtained and discovered that the sclera has two layers with different structural arrangements. In the inner layer, the fibers extend radially from the optic nerve’s periphery, while the fibers in the outer layer run perpendicular to those in the inner layer. Interestingly, in patients with DSM, the inner layer’s fibers were aggregated and thickened, while the outer layer’s fibers were compressed and thinned. The successful use of PS-OCT to visualize the organization of fibrous tissue in eye structures could have significant implications.The discovery of fiber patterns in the eyes of people with myopia has significant implications for clinical research, diagnostics, and therapeutics. According to senior author Dr. Masahiro Yamanari, recognizing these patterns could provide crucial insights for developing targeted therapies to address scleral abnormalities early and prevent potential damage to the overlying neural tissue, given the common occurrence of scleral pathologies such as DSM and staphylomas in myopic eyes. The hope is that this advancement in PS-OCT technology will lead to medical discoveries that will ultimately help more people protect their vision.
