A Comparative Study Of Optical Coherence Tomography And Histopathology After Multi-wavelength Laser In Pigmented Rabbits

Objective:To study the correlation between optical coherence tomography and histopa-thology after Multi-wavelength laser in pigmented rabbitsMethod:Thirty-six pigmented rabbits were used in the experiment. The left eye as theblank control group, the right eye as the experimental group.The rabbits were dividedinto three groups. These rabbits were respectively photocoagulated at posterior poleby green,yellow and red laser with laser lesion effect of grade Ⅲphotocoagulatedspots (4*4) in right eyes, and then observed at1h,7d,14d,28d after photocoagulationby OCT and histopathology.Results:1, Histopathological changes: Histopathological changes:1h after all laserphotocoagulation, the retina and choroidal subjected to different degrees of damage.In green laser lesions, changes were mainly resticted to the RPE that was loss ofmuch or all of pigment, the inner and the outer segments of photoreceptors that wereseverely disrupted. Secondly,choroidal capillaries with mild dilatation, and the outernuclear layer with most pyknotic nuclei. In yellow laser lesions, changes were mainlyresticted to choroidal capillaries with obvious expanded, the RPE that was loss ofmuch pigment, the inner and the outer segments of photoreceptors that were severelydisrupted. Secondly, the inner and outer nuclear layers with most pyknotic nuclei. Inred laser lesions, changes were mainly resticted to most choroidal vessels with seriousdilatation. Secondly, RPE and photoreceptor cell layer were mild damaged, the innerand out nuclear layers with much cells loss. Subsequently the proliferation of RPE,Müller cells and fibroblasts repaired the destroyed areas of retina.2,OCT images:1h after three laser photocoagulation, the reflectivity of choroidtissue could not been identifid. Retinal structure and delineation of the individuallayers comprising the retina were lost. All lesions were characterized byhigh reflectivity throughout the full thickness of the neurosensory tissue. The averagethickness of neurosensory layers (μ m) of green, yellow, red laser lesions:265.81±5.39,227.90±6.11,193.76±8.76. In green laser lesions, the RPE layers weremuch thinner or vanished. In yellow laser lesions, the RPE layers were much thinner.In red laser lesions, the continuity of RPE layers were partial interrupted.7d afterthree laser photocoagulation, RPE reflectivity appeared in the neurosensory layers,strong contraction through the full thickness of the neurosensory layers was observed.The average thickness of neurosensory layer(sμm)of green, yellow, red laser lesions:72.68±5.99,99.91±4.65,119.73±5.48. Subsequently, the RPE reflectivity in theneurosensory layers increased continuely, which sheltered choroid tissue reflectivity.Conclusion:1,After photocoagulation, the images obtained from OCT and histopathologyare consistent in whole, however, OCT can't recognize fine tissue changes. Therefore,OCT can be used clinically to follow the development of laser-induced lesions overtime and will provide the basis for laser treatment.2,Laser of different wavelength reach different parts of the fundus. The longerthe laser wavelength, the deeper histological depth in the fudus. The green lasermainly reaches RPE layer, the yellow laser mainly reaches choroidal capillary andRPE layer, the red laser mainly reaches choroid.