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D.–Y. Yu, S.J. Cringle, E.–N. Su, P.K. Yu, M. Humayun, G. Dorin; Laser Induced Changes In Intraretinal Oxygenation . Invest. Ophthalmol. Vis. Sci. 2004;45(13):2341.
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Purpose: To determine whether micro pulsed (MP) laser application has advantages over continuous wave (CW) delivery in achieving more selective retinal photocoagulation and greater control of the oxygenation benefit to the inner retina in the treated area. Methods: Oxygen sensitive microelectrodes were used to measure the oxygen level as a function of retinal depth in same area before and after laser burn in anaesthetised, mechanically ventilated Dutch belt rabbits (n=9). In the avascular region of the rabbit retina the choroid is the only significant source of retinal oxygenation. This removes the possibility of autoregulation of retinal vessels masking any induced changes in inner retinal oxygen availability. Laser lesions were created using a range of power levels from an Iridex OcluLight SLx Diode laser coupled to an operating microscope delivery system. MP duty cycles of 5%, 10%, and 15% were compared with CW delivery in each eye. Results: A highly reproducible correlation between laser parameters, retinal pathology and intraretinal oxygenation changes was found. Both CW and MP delivery were able to increase oxygen delivery from the choroid to the inner retina following damage to the RPE and photoreceptors. Retinal damage following MP delivery with 5% and 10% duty cycles was more selective, with a wider safety range in comparison to CW delivery. At high power levels MP delivery produced less suppression of choroidal oxygen tension than did CW delivery. Conclusions: Partial destruction of RPE and photoreceptors can create a significant oxygenation benefit to the inner retina. MP laser delivery appears to offer advantages in terms of better control of the extent of retinal damage. Further work is aimed at determining photocoagulation parameters that produce an oxygenation benefit to the inner retina, yet preserve useful retinal function in the treated area. Such a technique may offer significant advantages over current treatment regimes for ischemic retinal diseases and diabetic retinopathy.
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