Abstract
Background: :
In animal studies, 5 minutes from infusion, verteporfin is known to be at its maximum concentration in the choroid with almost none in the retina (Haimovici et al., 1997). This reverses as time progresses, and in 2 hours there is no presence of the compound in either choroid or retina. Photodynamic therapy (PDT) for choroidal neovascularization is not adjusted for variability in transit time to choroid and retina: PDT protocol requires a fixed interval between verteporfin infusion and laser activation for all patients. In patients with shorter transit time verteporfin may be transported farther, past choroid and into retina, by the time laser is activated. This may potentially cause damage, however transient, to retina and acute loss of vision.
Purpose: :
To correlate acute visual change after PDT with arm to retina fluorescein transit time.
Methods: :
Transport of fluorescein from arm to retina is employed here as an indirect measure of transport of verteporfin notwithstanding differences in their lipophilicity. Arm to retina transit time for fluorescein prior to PDT and visual acuity change within 7 days of the PDT for dozen consecutive patients treated with PDT for choroidal neovascularization from age–related macular degeneration was reviewed.
Results: :
Arm to retina transit time for each patient was normalized with the average transit time for the entire sample. Patients experiencing an acute loss of vision (regardless of eventual improvement) had an average normalized transit time of less than 1 (0.88) whereas those who either experienced an improvement or no change in vision had an average normalized transit time of greater than 1 (1.1).
Conclusions: :
Besides adjusting for body surface area in verteporfin treatment, correcting for transit time may further enhance the efficacy of PDT for treating choroidal neovascularization. Shorter arm to retina transit times of fluorescein may require shorter interval time between verteporfin infusion and activation of laser to prevent damage to retina. Larger sample size involving several treatment sites is recommended to validate this finding.
References: :
Haimovici et al., Curr Eye Res. 1997 16(2):83–90
Keywords: photodynamic therapy • choroid: neovascularization • age-related macular degeneration