Authors
Suetov A.A.1, 3, Boiko E.V.1, 2, Izmaylov A.S.1, Doktorova T.A.1, Ivanov A.A.4
1 St. Petersburg Branch S. Fyodorov Eye Microsurgery Federal State Institution St. Petersburg
2 Department of Ophthalmology North-Western State Medical University named after I.I. Mechnikov St. Petersburg
3 State Scientific Research Test Institute of Military Medicine, St. Petersburg
4 Alkom Medica LLC, St. Petersburg
Abstract
Background. The development of laser systems with automated control of retinal coagulation depth will make it possible to obtain reproducible laser burns of a given brightness on the ocular fundus during treatment. Nevertheless, the problem of correspondence of the brightness of the formed coagulates fixed by video capture to the depth of the formed coagulates in the retinal thickness remains poorly studied.
Objective. To study the correspondence between the brightness of the formed burns recorded by video capture and the depth of retinal coagulation during dose-dependent laser photocoagulation using an automated laser system based on the feedback principle.
Materials and methods. A prototype of an automated system for laser photocoagulation of the retina, consisting of a 0.81 µm diode laser and a video capture module integrated into the optical system of the slit lamp, as well as software that controls laser exposure using the feedback principle. Studies were performed on rabbit eyes (n=20). At spot diameter 200 μm, power 100, 140, 180, 220, 260 and 300 mW and planned coagulation levels 5, 10, 20, 30, 40, 50 and 70%, the actual brightness of the obtained coagulates (%), the correspondence between planned and actual coagulate brightness were studied. The depth of coagulation (% of neuroretina thickness) and its correlation with the actual brightness of coagulates were studied at OCT.
Results. With a planned brightness of 5-10% (grade 1 according to L’Esperance), the actual brightness of the burns was significantly higher, the depth of coagulation on OCT was 20 to 30% of the retinal thickness. At the planned brightness of 20-40% and 5-70% (grade 2 and 3 according to L’Esperance), the actual burns brightness was not significantly different throughout the power range, and the depth of coagulation by OCT was 35-50% and 80-120%, respectively. The coefficient of variation of actual brightness and coagulation depth did not exceed 15% for the whole range of planned brightness and used power, except for cases of planned brightness of 5-10% and power of 220 mW and more. A significant correlation was found between actual brightness and coagulation depth (R=0.96, p=0.001).
Conclusion. During laser coagulation of the retina using a new automated laser system based on the feedback principle, homogeneous laser coagulates are automatically formed, and there is a significant correlation between the depth of neuroretinal coagulation and the brightness of burns recorded by video capture.
Keywords: retina, laser photocoagulation, automated laser system, feedback system.
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