Evaluation of blood flow on optic nerve head after pattern scan and conventional laser panretinal photocoagulation

Abstract

To evaluate the changes in the blood flow on retina and the optic nerve head (ONH) after conventional laser treatment and to compare it to that after patterned scanning laser (PASCAL) treatment in patients with severe nonproliferative diabetic retinopathy (S-NPDR).In this prospective, cross-sectional study, the blood flow on retina and the ONH was assessed by laser speckle flowgraphy using the mean blur rate (MBR) in 39 eyes with S-NPDR before, 1, 4, 8, 12 weeks after panretinal photocoagulation (PRP). Of 39 eyes, 17eyes with 17 patients treated by conventional laser and 22 eyes with 22 patients treated by PASCAL.The mean age was 55.5 ± 11.5 years in the conventional laser group, 55.6 ± 11.8 years in the PASCAL group. The MBR-vessel, which can be dominantly expressed as retinal blood flow, was significantly reduced after PRP treated by conventional laser (P < .001), but did not change after PRP treated by PASCAL. The ratio of MBR-vessel to the baseline was significantly lower in the conventional laser group only at Week 1 (P = .045). The MBR-tissue, which can be dominantly expressed as the ONH blood flow, did not significantly change after PRP in the both group. The multiple stepwise regression analysis revealed that the laser burns was an independent factor significantly correlated with the ratio of MBR-vessel at Week 1 to the baseline (β = -0.550, P = .012).The retinal blood flow was significantly reduced during the 12 weeks only after completion of PRP by conventional laser treatment. Our results indicate that short pulse on PRP treatment performed by the PASCAL would not significantly reduce the retinal blood flow.

Figure 1

Representative composite color maps of the MBR as measured by LSFG. (A) Red color indicates a high MBR and the blue color indicates a low MBR. To measure the MBR of the blood flow on the ONH a circle was set around the ONH. (B) A binary formatted image for segmentation between the vessel (white area) and tissue (black area) areas. LSFG = laser speckle flowgraphy, MBR = mean blur rate, ONH = optic nerve head.

Figure 2

Fundus photographs and composite color maps of a xx-year-old woman with S-NPDR. Fundus photograph taken with Optos 200TX showing S-NPDR before (A) and after PRP treated by conventional laser (B). Representative composite color maps of the MBR as determined by LSFG before, after first, second and third session, and 1, 4, 8, and 12 wk after PRP treatment on the ONH (C). There was a significant reduction in the MBR-vessel after the PRP. LSFG = laser speckle flowgraphy, MBR = mean blur rate, ONH = optic nerve head, PRP = panretinal photocoagulation, S-NPDR = severe nonproliferative diabetic retinopathy.

Figure 3

Fundus photographs and composite color maps of a xx-year-old woman with severe S-NPDR. Fundus photograph taken with Optos 200TX showing S-NPDR before (A) and after PRP treated by PASCAL (B). Representative composite color maps before, after first session, and 1, 4, 8, and 12 wk after PRP treatment on the ONH (C). There was no significant reduction in the MBR-vessel after the PRP. MBR = mean blur rate, ONH = optic nerve head, PASCAL = patterned scanning laser, PRP = panretinal photocoagulation, S-NPDR = severe nonproliferative diabetic retinopathy.

Figure 4

There was a significant reduction in the MBR-vessel after the PRP in the conventional laser group (A) and the ratio of MBR-vessel to the baseline in the conventional group was significantly lower than that in the PASCAL group at 1 wk after completion of PRP (B). There was not significantly reduction in the MBR-tissue in the both groups (C) and no significant difference was observed in the ratio of the MBR-tissue throughout the post-PRP period (D). ^∗∗∗P < .001, ^∗∗P < .01, ^∗P < .05. MBR = mean blur rate, PASCAL = patterned scanning laser, PRP = panretinal photocoagulation.

Figure 5

Scatterplot of the ratio of MBR-vessel at Wk 1 to the baseline versus the number of laser photocoagulation burns. The ratio of MBR-vessel at Wk 1 to the baseline was significantly correlated with the number of laser photocoagulation burns in the conventional laser group (r = −0.427, P = .086) (A) and the PASCAL group (r = −0.506, P = .016) (B). MBR = mean blur rate, PASCAL = patterned scanning laser.