Corneal Stiffening by a Bacteriochlorophyll Derivative With Dextran and Near-Infrared Light: Effect of Shortening Irradiation Time up to 1 Minute

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Abstract

Purpose:

The aim of this study is to determine the effect of variation of the exposure time of near-infrared irradiation on corneal stiffening after a bacteriochlorophyll derivative (WST11) with dextran (WST-D) application.

Methods:

One hundred four paired eyes of 3-month-old New Zealand White rabbits were included in this study. Fifty-two eyes (ex vivo n = 34, in vivo n = 18) were mechanically deepithelialized, treated topically with WST-D, and irradiated at 10 mW/cm2 using a diode laser at 755 nm for 1, 5, or 30 minutes. Untreated fellow eyes served as controls. Corneoscleral rings were removed immediately after treatment (ex vivo), or 1 month after treatment (in vivo). Corneal strips were cut and underwent biomechanical stress–strain measurements.

Results:

Ex vivo, the mean tangent elastic modulus was significantly higher in the treatment groups than in the control groups for 1, 5, and 30 minutes of irradiation, respectively, 6.06 MPa, 95% confidence interval (CI, 4.5–7.6) versus 14.02 MPa, 95% CI (10.2–17.8), n = 11, 4.8 MPa, 95% CI (3.9–5.7) versus 15.03 MPa, 95% CI (12–18.1), n = 11, and 7.8 MPa, 95% CI (5.6–10.02) versus 16.2 MPa, 95% CI (13.6–18.9), n = 11; P < 0.001 for all comparisons. In vivo, the mean elastic moduli in the treatment groups were significantly higher for 5 and 30 minutes of irradiation but not for 1 minute of irradiation, respectively, 11.4 MPa, 95% CI (8.5–14.2), versus 17.1 MPa, 95% CI (14.5–19.7), n = 5; P < 0.001, and 9.4 MPa, 95% CI (5.1–13.8) versus 16 MPa, 95% CI (13.1–19), n = 5; P < 0.01, and 11.3 MPa, 95% CI (6–16.6) versus 12.2 MPa, 95% CI (7.5–16.8), n = 5; P = 0.7.

Conclusions:

WST-D/near-infrared treatment using shortened irradiation time (1 minute ex vivo and 5 minutes in vivo) results in significant corneal stiffening, and this might provide an alternative to the currently applied riboflavin/ultraviolet A cross-linking.

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