A study on the effects of 532 nm continuous laser combined with photodynamic therapy versus 595 nm pulsed dye laser on a chicken comb model of vascular malformation

Abstract Objective: To explore the effects of 532 nm continuous laser combined with photodynamic therapy (PDT) versus 595 nm pulsed dye laser (PDL) on a chicken comb model of vascular malformation. Study design: Ninety adult male chickens were divided into three groups (A, B and C). One comb side of the chickens was taken randomly as the treatment side, and the other side as the self-control side. Group A was irradiated once with a 532 nm continuous laser after a single intravenous injection of hematoporphyrin monomethyl ether (HMME). In group B treatment side of combs was irradiated once with a 595 nm pulsed dye laser (PDL). In the control group C, the combs were treated neither with photosensitizer nor with irradiation. Results: Compared with the self-control sides, part of the treated combs were blanched after HMME-PDT while the histopathology showed an absence of erythrocytes and the vessel lumina were obliterated, leaving the normal overlying epidermis completely intact. At the same time selective destruction of the capillaries in the target area and obvious reduction of vascular vessel number were seen (p<0.01). In nine cases (30%) treatment was completely ineffective resulting in a total effective rate of 70% (21 cases). No scar formation was observed at all. After PDL treatment most of the treated combs were blanched while histopathology showed an absence of erythrocytes and the vessel lumina were obliterated, leaving the overlying epidermis with slight injuries and scabs. Here again, destruction of the capillaries in the target area and obvious reduction of vascular vessel number (p<0.01) were obtained. The total effective rate was 93% (28 cases); in two cases scars occurred. The combs of the control group showed no change compared with self-control sides (p>0.05). Conclusion: In the chicken comb model it was shown that both 532 nm HMME-PDT and 595 nm PDL treatment could damage capillaries in the superficial dermis of combs. The 532 nm HMME-PDT had fewer side effects compared with 595 nm PDL, but the inefficiency rate of 532 nm HMME-PDT group was higher than the 595 nm PDL group. No significant difference was observed in the macroscopic and histopathological results of both groups (p>0.05).