The Application Of Double Light Source Optical Coherence Tomography In The Examination Of Retinal Nerve Fiber Layer In Glaucoma Rats

Glaucoma is the second leading blinding eye disease and the first leading irreversible transformation blinding eye disease in the world.The irreversibility of optic nerve damage determines the importance of early detection and diagnosis of glaucoma in prevention and treatment.Optical coherence tomography(OCT)can visually detect the thickness of retinal nerve fiber layer(RNFL)in glaucoma patients.But by the time the thickness of the retinal nerve fiber layer changes,patients often have impaired optic nerve function.It has been proved that the ultrastructure of axons changes earlier than the thickness of retinal nerve fibers.If OCT can detect the changes in the ultrastructure of axons with elevated intraocular pressure in an early and non-invasive manner,it will provide a clinical basis for the early detection and diagnosis of glaucoma,and provide a new idea and a broader field of vision for the further study of glaucoma.Objective:The imaging intensity and thickness of the retinal nerve fiber layer in glaucoma mice were detected by dual light source OCT,and it was concluded that whether the imaging intensity of the nerve fiber layer changed before the thickness change.Early detection of glaucoma before the thinning of the retinal nerve fiber layer can save time for early treatment of glaucoma to avoid irreversible damage to visual function.It lays the experimental foundation for the clinical application of dual light source OCT.Methods:The limbal veins and each scleral aqueous vein of Sprague Dawley(SD)rats were photocoagulated by 532 laser.After three days,the trabecular meshwork was photocoagulated with 532 laser,and the intraocular pressure of rats was rapidly increased after two laser photocoagulations of three days.The damage and changes of retinal nerve fiber layer were observed after one week of high intraocular pressure.The loss of retinal ganglion cells and damage of retinal nerve fiber layer in this rat model of ocular hypertension is similar to the pathological changes in human glaucoma.At present,the light source of OCT is near infrared light.Its principle is to measure the thickness of retinal nerve fibers by measuring the reflectivity of the axons of retinal ganglion cells,namely the retinal nerve fibers.Dual light source OCT increases the scanning light source of OCT,that is,a 532 nm visible light source is added on the basis of infrared light as the inspection light source.According to the changes of the ratio of the imaging intensity of the two light sources,the damage changes of the cytoskeleton of the retinal ganglion cell axon are detected.If this ratio change appears before the thinning of retinal nerve fiber layer and can be detected successfully,it can provide objective and scientific basis for the early detection of glaucoma.Combined with the results of immunostaining,the structure of axon cytoskeleton in retinal nerve fiber layer of glaucoma mice was quantitatively analyzed,and the early changes were confirmed.Immunohistochemical confocal imaging was used to observe the cytoskeletal components of the axons of retinal ganglion cells in glaucoma rat: microtubules(MTs),F-actin,and neurofilaments.Multiple fluorescent stains were used to stain F-actin,MT,NF and nucleus simultaneously in the same tissue.Confocal microscopy was used to examine the distribution of these components in the entire retinal patch.Results:The ratio of the imaging intensity of retinal nerve fibers layer measured by dual-light OCT to that measured by infrared light and blue-green light at 532 nm in glaucoma rat decreased.In addition,the ratio of the imaging intensity of the retinal nerve fiber layer measured by dual light source OCT visible light to that measured by infrared light decreased before the nerve fiber layer thinning.Irregular staining of F-actin,MT,and NF is found in the retinal nerve tracts of glaucoma rat.A network of F-actin is present on the surface and between bundles of RNFL.Complete loss of F-actin and MTs was found in the severely damaged retinal region,while residual tracts of NFs were evident.The irregularity of F-actin staining and nuclear density were significantly increased in RNFL prior to the decrease in RNFL thickness.Conclusion:In glaucoma rat,the decrease in the ratio of the imaging intensity of the nerve fiber layer measured by dual light source OCT visible 532 nm blue-green light to that measured by infrared light appeared before the nerve fiber thinning in glaucoma rat.Dual light source OCT can detect the early ultrastructural changes of cytoskeleton and thickness of retinal nerve fiber layer in glaucoma rat in vivo without invasion.