PDT causes transient impairment of retinal function

[MyVisionTest]

Photodynamic therapy (PDT) results in transient functional
deterioration in the retina, according to a new study.

Photodynamic therapy with verteporfin temporarily closes choroidal
neovascular complexes via the release of oxygen free radicals. This
process also liberates angiogenic and inflammatory agents that may
increase vascular permeability and perpetuate CNV activity after
treatment. It is thought that PDT may result in collateral damage to
normal choroidal blood vessels surrounding the CNV at the time PDT is
performed. Reduced-fluence PDT attempts to reduce the risk of vision
decline following PDT by cutting the dose of verteporfin, decreasing
the laser energy, and other measures designed to minimize collateral
damage.

This was a prospective interventional case series. Twenty-two patients
with age-related macular degeneration (AMD) with unilateral choroidal
neovascularization (CNV) were examined using Fourier transform-based
spectral retinal imaging (SRI), Heidelberg retinal flowmeter (HRF),
and multifocal electroretinogram (mfERG) before and 1 week and 1 month
after PDT. Eleven fellow eyes without CNV and 11 control eyes of 11
age-matched healthy volunteers were also investigated. Eleven of 22
patients with neovascular AMD were retreated using verteporfin PDT and
examined using a protocol similar to the one used for the first
treatment.

Oxygen saturation levels in the macula of eyes with neovascular AMD
were significantly higher than those in normal control eyes (P =
0.026) but were not significantly higher in eyes with nonneovascular
AMD. Oxygen saturation levels decreased 1 week after a single
treatment (P = 4.59 × 10-3) and retreatment (P = 0.0134) and
recovered to baseline levels at 1 month follow-up (P > 0.05). HRF
demonstrated reduced mean blood flow at 1 week after single treatment
(P = 9.22 × 10-4) and retreatment (P = 0.0307). One month after PDT,
mean blood flow tended to show recovery. There was a similar decrease
in mfERG amplitude 1 week after treatment, but the logarithm of
minimum angular resolution (logMAR) vision was stable or improved
throughout follow-up.

The investigators conclude that oxygen saturation levels, mean blood
flow, and mfERG amplitude decreased 1 week after PDT treatment in both
single treatment and retreatment groups. Although logMAR vision is
stable or improved, our data showed transient functional deterioration
in the retina after PDT treatment.

Retina. 2009 Nov-Dec;29(10):1450-6

http://www.ncbi.nlm.nih.gov/pubmed/19816240

======================
ABOVE IS A PLAIN TEXT REPRODUCTION OF A NEWS STORY THAT APPEARS ON
MYVISIONTEST.COM. ANY HYPERLINKS, IMAGES, TABLES, OR OTHER
ENHANCEMENTS HAVE BEEN REMOVED. TO VIEW THE ORIGINAL VISIT THE BELOW
LINK.

http://www.myvisiontest.com/newsarchive.php?id=1035