Clinical Trial: TTT Versus PDT for Treatment of Choroidal Neovascularization in Age-Related Macular Degeneration

Study Status: Recruiting
Recruit Status: Unknown status
Study Type: Interventional

Official Title: Transpupillary Thermotherapy Versus Photodynamic Therapy Treatment of Occult and Minimally Classic Choroidal Neovascularization in Age-Related Macular Degeneration.

Brief Summary: The purpose of the study is to compare photodynamic therapy to transpupillary thermotherapy as a treatment method for choroidal neovascularization in age-related macular degeneration ( AMD). AMD is a disease affecting the macula, the central area of the retina.There are two main types of AMD. Geographic atrophy ( dry) AMD and neovascular ( wet) AMD. In neovascular AMD, sub-retinal neovascular membranes ( new blood vessels) develop beneath the retina. The new vessels can leak causing haemorrhage that leads to significant visual loss. Photodynamic therapy ( PDT) is a method for treating neovascular membranes without affecting the retina. Photoactive chemicals are injected into the patient and irradiated with light as the pass through the neovascular membranes. This light is strong enough to activate the chemicals, that destroy the blood vessels, but not strong enough to cause damage to the overlying retina. The duration of the treatment is 83s. PDT treatment is effective in predominantly classic subfoveal choroidal neovascularization ( CNV), but was observed to yield no visual benefit in minimally classic CNV during a 2-year follow-up and as to occult CNV the effect was scarce. PDT does have its drawbacks, one of which is the cost. Another is that the patient become highly sensitive to strong light. Transpupillary thermotherapy ( TTT) is a thermic treatment of choroidal neovascularization in AMD. Using a thermal diode laser ( emission 810 nm), transpupillary irradiation of the fundus through a conventinal contact lens is performed. The temperature is elevated < 10 degrees C during a 60s exposure to continuous radiation. The laser power is adjusted to the diameter of the laser beam. In a pilot study, Reichel et al. ( 1999) demonstrated that subfoveal occult CNV could be occluded and visual acuity stabilized in a majority of patients treated with TTT. These results has been confirmed in small series of cases with occult CNV and with minimally ( <50%) classic CNV.

Detailed Summary:

Age-related macular degeneration ( AMD) is a disease affecting the macula, the central area of the retina. There are two main types of AMD. Geographic atrophy ( dry) AMD and neovascular ( wet) AMD. In neovascular AMD, subretinal neovascular membranes develop beneath the retina. The new vessels can leak causing haemorrhage that leads to edema, scarring and significant visual loss. Sub-retinal neovasular membranes are defined as classic, occult and minimally classic according to their apperance on fluorescein angiography. Trials have shown that early laser photocoagulation of classic extrafoveal lesions could delay the loss of vision in a small number of patients. However, most patients present with subfoveal membranes and whilst photocoagulation can limit the extent of subsequent visual loss, it causes immediate loss of central vision due to concurrent destruction of the overlying retina. Photodynamic theray ( PDT) represent a milestone in the treatment of CNV, and marks the start of a new era. Current PDT operates on the basis of principal that makes use of a dye ( verteporfin) which is preferentially retained in proliferating tissue such as CNV, sensitizing the endothelial cells to laser rediation ( 689 nm). Endothelial cells degeneration is mediated by reactive oxygen which intermediates with subsequent platelet activation, and a thrombosis, and temporary or permanent occlusion of vessels is seen in the treated area ( Ghazi et al 2001. The light is strong enough to activate the chemicals, causing them to emit free radicals that destroy the blood vessles, but not strong enough to cause damage to the overlying retina. The duration of the treatment is 83s. PDT is effective in predominantly classic subfoveal CNV, but was observed to yield no visual benefit in minimally clasic CNV during a 2-year follow-up. As to occult CNV PDT was effective in small lesions ( 4 disc areas or less), when there was a recent disease progress
Sponsor: St. Erik Eye Hospital

Current Primary Outcome: Visual acuity, base, 6 weeks, 3 months, 4,5 months, 6 months, 9 months, 12 months, 18 months, 24 months.

Original Primary Outcome: Same as current

Current Secondary Outcome:

  • New vessel growth
  • Retinal thickness


Original Secondary Outcome: Same as current

Information By: St. Erik Eye Hospital

Dates:
Date Received: November 29, 2005
Date Started: June 2003
Date Completion: January 2008
Last Updated: February 2, 2006
Last Verified: June 2004