Effect of Pulse Duration on Size and Character of the Lesion in Retinal Photocoagulation

Abstract

Short-duration focal pattern grid macular photocoagulation for diabetic macular edema: four-month outcomes".

Functional rescue of experimental ischemic optic neuropathy with αB-crystallin

“…[5][6][7][8]10,11,17 After rose bengal (1.25 mM in PBS, 2 ml per g body weight) injection via tail vein, the ON head was exposed to 20 light spots (frequency doubled Nd:YAG laser, Pascal, OptiMedica, Santa Clara, CA, USA), each with 100 mm diameter (equivalent to 39 mm on the nerve), at a power of 35 mW and duration of 500 ms. We delivered small laser spots at low power and shorter duration circumferentially around the ON head in order to focus more precisely while covering the entire ON head. The degree and extent of whitening due to ischemia 18 are similar to that of the Bernstein model in our direct comparison. As reported previously, 5,8 application of the laser in the absence of rose bengal did not cause significant ischemia.…”

Optimal current and future treatments for diabetic macular oedema

“…This may result in fewer secondary complications including loss of visual field and other psychophysical parameters associated with function of second-and third-order retinal neurons, which are typically preserved. 13,14 It has been established that shorter pulse duration burns have a resultant smaller diameter footprint on the retina, both laterally and axially, than longer duration burns with calculated axial retinal injury of 70 mm for 10 ms burns contrasted with approximately 220 mm for a 100 ms burn. 13 Fundus auto fluorescence and Fourier-domain optical coherence tomography in patients undergoing diabetic laser photocoagulation with 10 and 20 ms patterned short-duration burns suggest that gradual retinal lesion enlargement or 'creep' does not occur with shorter burns and that there may actually be progressive shrinkage rather than enlargement of these burns over time.…”

“…13,14 It has been established that shorter pulse duration burns have a resultant smaller diameter footprint on the retina, both laterally and axially, than longer duration burns with calculated axial retinal injury of 70 mm for 10 ms burns contrasted with approximately 220 mm for a 100 ms burn. 13 Fundus auto fluorescence and Fourier-domain optical coherence tomography in patients undergoing diabetic laser photocoagulation with 10 and 20 ms patterned short-duration burns suggest that gradual retinal lesion enlargement or 'creep' does not occur with shorter burns and that there may actually be progressive shrinkage rather than enlargement of these burns over time. There may also be preservation and/or remodelling of the outer retinal layers including filling in of initial defects in photoreceptors, presumably by sliding from adjacent areas in pre-clinical models for smaller-sized burns of 200 mm or less, that may favourably affect VEGF distribution in the retina and visual field loss.…”

Can photoreceptor loss also account for changes in pupil size following panretinal photocoagulation?

“…3 The extent of retinal damage generated by PRP is dependent upon the laser beam's diameter, power, and duration. 4 Even though the exact power of the used beams was not specified by the authors, it is conceivable that a light-intensity photocoagulation such as the one they have used, especially with conventional PRP, might have inflicted structural and functional damage not only to the photoreceptors, retinal pigment epithelium, and choroid, but also to the retinal nerve fiber layer and inner retina as well, 4,5 possibly altering the photoreceptive and integrative capabilities of ipRGCs and increasing pupil size under various conditions of illumination. Furthermore, it would be of great benefit if the authors could clarify whether the non-studied/untreated eye was also exposed to light during the direct pupillometric measurement and whether anisocoria was observed.…”