TTT trial is investigating occult CNV treatment

No other effective options exist to treat occult pathologies.

Issue: August 15, 2000

BOSTON — Physicians are enrolling patients to investigate the promising pilot study results of a possible treatment for occult choroidal neovascularization (CNV).

Transpupillary thermotherapy (TTT) could aid patients with subfoveal occult CNV secondary to age-related macular degeneration (AMD), a condition that is not presently treatable.

TTT is a mild form of long-pulse retinal photocoagulation. Surgeons hope that it will provide an effective treatment option because no other option is available.

According to lead investigator Elias Reichel, MD, of the New England Eye Center in Boston, “We’re doing this to confirm our very strong clinical impression,” garnered through a pilot study that TTT will work.

“We now have worldwide experience, with more than 1,000 eyes being treated, suggesting the efficacy of this treatment modality,” Dr. Reichel said.

He has enrolled about one-quarter of the patients needed for the TTT4CNV Clinical Trial.

Inclusion criteria include AMD in patients 50 years or older with visual acuity between 20/50 and 20/400, as determined by Early Treatment for Diabetic Retinopathy Study (ETDRS) testing.

Occult CNV has to have a total lesion diameter of 3,000 µm (2 disc diameters), with CNV underlying or surrounding the center of the macula.

Other criteria include:

Late leakage or fibrovascular pigment epithelium detachment (PED);
Subretinal fluid or exudate;
If present, classic CNV less than 10% of the total lesion diameter;
If present serous PED less than 25% of the lesion;
If present, subretinal hemorrhage less than 50% of the lesion;
If present, subretinal fibrosis less than 25% of the lesion;
No chorioretinal anastomosis; and
No geographic atrophy greater than 0.5 DA within 500 µm of the foveal center.

Exclusion criteria include prior retinal surgery, any ocular surgery within 3 months, taking medicine toxic to the retina, glaucoma, diabetic retinopathy or intraocular pressure higher than 26 mm Hg.

Good pilot results

Dr. Reichel reported preliminary results from a pilot study in the October 1999 issue of Ophthalmology.

He treated 16 eyes in 15 patients with TTT. He used a diode laser with a beam wavelength of 810 nm.

In the pilot study, researchers treated patients between June 1996 and June 1998 (see Ocular Surgery News, “TTT may stabilize subfoveal occult CNV,” January 1, 2000 issue, page 42).

All patients were 55 or older with a mean age of 78, had subfoveal occult CNV secondary to AMD and had best corrected visual acuities between 20/30 and 20/400.

Patients received spot sizes of 1.2 mm, 2 mm or 3 mm, depending on the size of the lesion. Treatment involved one spot for 60 seconds at a power range between 360 mW and 1,000 mW. End points ranged from no color change to a barely detectable light-gray color change.

Dr. Reichel followed the eyes between 6 months and 25 months, with a mean follow-up of 13 months. Eyes improved in vision by two or more Snellen lines in three treated eyes (19%) and stabilized (no change or one line improvement) in nine eyes (56%). Another four eyes (25%) decreased by at least one line of visual acuity.

Also, 15 eyes (94%), including three of the four eyes that had a decline in vision, showed a reduction of subretinal fluid on fluorescein angiography, optical coherence tomography and/or clinical examination. Few side effects were seen.

For Your Information:

Elias Reichel, MD, is an assistant professor of ophthalmology at the New England Eye Center. For more information, or to enroll in this study, Dr. Reichel can be reached at 750 Washington St., Boston, MA 02111; (617) 636-1648; fax: (617) 636-4866.

Reference:

Reichel E, Berrocal AM, Ip M, et al. Transpupillary thermotherapy of occult subfoveal choridal neovascularization in patients with age-related macular degeneration. Ophthalmology. 1999;106:1908-1914.