Transpupillary thermotherapy of subfoveal occult choroidal neovascularization.

Choroidal neovascularization secondary to age-related macular degeneration is a leading cause of vision loss in adults. Although most patients present with occult CNV, treatment has focused on the small percentage of eyes with well-delineated, classic CNV. Transpupillary thermotherapy is a recent advancement in the management of occult CNV. Transpupillary thermotherapy acts in a subthreshold manner by slightly raising the choroidal temperature. A recent pilot study demonstrated that 56% of treated eyes remained stable one year after treatment with only 25% losing two lines of visual acuity. The TTT4CNV study will further evaluate the effectiveness of transpupillary thermotherapy in a randomized, double-blind trial.

Transpupillary thermotherapy for age-related macular degeneration: principles and techniques.

Transpupillary thermotherapy (TTT) is a subthreshold, low irradiance, long exposure duration, large spot size, infrared diode laser protocol. Retinal temperature increases in TTT for choroidal neovascularization (CNV) are substantially lower than those in conventional short-pulse photocoagulation, but they are maintained for 60 seconds to achieve therapeutic results. Treatment power is adjusted for retinal lesion size, chorioretinal pigmentation, macular elevation and media clarity. TTT uses 810-nm diode laser infrared radiation, which has no significant retinal phototoxicity. A parfocal laser delivery system is required to assure uniformity of irradiance across large diameter treatment spots. Relative contraindications for TTT include dense subretinal hemorrhage, prior focal photocoagulation and serous RPE detachment. Adverse events are rare, and include decreased vision and retinal arteriole occlusion. Randomized, prospective multi-center trials are underway to compare the results of TTT for occult CNV in age-related macular degeneration to the natural history of the disorder. Imaging, electrophysiologic or thermometric techniques may ultimately provide intra-operative or post-operative monitoring to assure the adequacy of TTT for CNV, despite the absence of ophthalmoscopically visible lesions.

Ophthalmoscopic contact lenses for transpupillary thermotherapy.

Ophthalmoscopic contact lenses for transpupillary thermotherapy (TTT) must provide effective visualization of retinal treatment sites and transmission of infrared diode laser radiation. Selection and proper use of retinal laser lenses requires knowledge of their lateral magnification, laser beam magnification factor, field of view and resolution. Optical performance is analyzed for Goldmann-type lenses and a series of inverted image lenses of differing magnification. Goldmann lenses have the highest resolution, but inverted image lenses of comparable magnification have 2.5 times or more their field of view. Inverted image lenses of similar magnification can differ in resolution. They require 2-4% more incident laser power to produce the same retinal irradiance as a Goldmann lens, but this difference is small in comparison to other clinical variables. Tilting an ophthalmoscopic contact lens up to 15 degrees causes little distortion in the circularity of the retinal spot formed by a laser beam or difference in retinal irradiance across the spot. Inverted image lenses produce higher anterior segment irradiances than Goldmann-type lenses, but anterior segment injuries are less likely in TTT than conventional visible light, short-pulse retinal photocoagulation because of the comparatively low irradiances used in TTT and the decreased absorption of diode laser infrared radiation in ocular media and melanin.

Transpupillary thermotherapy (TTT) of occult choroidal neovascularization: a retrospective, noncomparative case series of fifty-seven eyes.

PURPOSE: To evaluate the efficacy of transpupillary thermotherapy (TTT) for the treatment of occult choroidal neovascularization. METHODS: A retrospective, noncomparative case series of 57 eyes of 52 patients who presented with occult subfoveal CNV and were treated with TTT. RESULTS: 83% of eyes were either stable (+/- one line) or showed improvement in visual acuity. 83% of eyes showed stabilization of their exudative process after one TTT treatment as evidenced by resorption of subretinal and/or intraretinal exudate or hemorrhage. Nine percent of eyes developed classic CNV during the mean follow-up time of ten months. CONCLUSIONS: TTT appears to stabilize the exudative process in eyes with occult CNV. A prospective, sham-controlled, randomized study (TTT4CNV Clinical Trial) is currently underway to directly compare TTT to the natural history of occult CNV.

Transpupillary thermotherapy for age-related macular degeneration: long-pulse photocoagulation, apoptosis, and heat shock proteins.

OBJECTIVE: To provide a biophysical foundation for using transpupillary thermotherapy (TTT) to manage choroidal neovascularization in age-related macular degeneration (ARMD). METHODS: Retinal temperature rise in laser therapy is proportional to retinal irradiance (laser power/area) for a particular spot size, exposure duration, and wavelength. TTT is a low irradiance, large spot size, prolonged exposure (long-pulse), infrared laser photocoagulation protocol. Results from an experimentally confirmed, finite element model of retinal light absorption and heat conduction are used to analyze laser parameter selection and its consequences. Results from apoptosis, heat shock protein and hyperthermia research are used to examine how chorioretinal damage from clinical procedures might be reduced. RESULTS: Chorioretinal thermal equilibration occurs during long-pulse TTT photocoagulation. Retinal temperature increases are similar in the RPE where laser radiation absorption is significant and in the adjacent neural retina where there is negligible radiation absorption. For parameters used to treat occult choroidal neovascularization in lightly-pigmented fundi (800-mW, 810-nm, 3-mm retinal spot diameter, 60-sec exposure duration), the maximum chorioretinal temperature elevation is calculated to be roughly 10 degrees C, significantly lower than the 20 degrees C temperature elevations measured in threshold, conventional short-pulse retinal photocoagulation. CONCLUSIONS: To achieve a preselected temperature rise, TTT laser power must be increased or decreased in proportion to the diameter rather than the area of the laser spot. Clinical power settings should be adjusted for fundus pigmentation and media clarity because both of these factors affect absorbed retinal irradiance and thus retinal temperature rise. Noninvasive thermal dosimetry currently is unavailable for clinical retinal photocoagulation, but potential thermometric techniques include MRI, liposomal-encapsulated dyes, multispectral imaging or reflectometry, and subretinal or episcleral thermometry. TTT may be useful not only as independent therapy, but also as an adjunct to PDT, antiangiogenic drugs and ionizing radiation therapy in the management of neovascular ARMD. Low temperature, long-pulse photocoagulation is a potential strategy for decreasing neural retinal damage in subsequent TTT or short-pulse photocoagulation and perhaps even for treating glaucoma or retinal degenerations.

Transpupillary thermotherapy of occult subfoveal choroidal neovascularization in patients with age-related macular degeneration.

OBJECTIVE: To evaluate the efficacy of transpupillary thermotherapy for the treatment of occult subfoveal choroidal neovascularization (CNV) in patients with age-related macular degeneration. DESIGN: A retrospective, noncomparative case series. PARTICIPANTS: Sixteen eyes of 15 consecutive patients who presented with occult subfoveal choroidal neovascularization secondary to age-related macular degeneration. INTERVENTION: After informed consent was obtained, 16 eyes of 15 patients were treated with transpupillary thermotherapy. All patients underwent pretreatment fluorescein angiography and were deemed untreatable by the Macular Photocoagulation Study standard. Transpupillary thermotherapy was delivered using a diode laser at 810 nm. A variable spot size of 1.2 mm, 2.0 mm, or 3.0 mm was used depending on the size of CNV. The diode laser was delivered through a contact lens, and treatment was initiated in one spot for 60 seconds' duration at a power range between 360 and 1000 mW. The end point was an area of no visible color change to a light-gray appearance. MAIN OUTCOME MEASURES: In all eyes, outcome was assessed by Snellen chart visual acuity and clinical examination. In 10 of 16 eyes, preoperative and postoperative fluorescein angiography and optical coherence tomography were available. In the remaining 6 of 16 eyes, exudation was measured by postoperative clinical examination alone. RESULTS: Three eyes (19%) showed a two-or-more-line improvement in visual acuity over a period of 6 to 25 months. Mean follow-up was 13 months. Visual acuity remained stable (no change or one-line improvement) in nine treated eyes (56%). The remaining four eyes (25%) showed a decline (equal to one-line worsening or greater) in visual acuity. Fifteen eyes (94%) demonstrated decreased exudation on fluorescein angiography, optical coherence tomography, and/or clinical examination. CONCLUSIONS: Transpupillary thermotherapy shows no deleterious side effects in treating occult subfoveal choroidal neovascularization. A randomized, prospective study is necessary to evaluate treatment efficacy.

Transpupillary thermotherapy.

Hyperthermia has long been recognized as potentially useful in the treatment of human neoplasms. Only recently has technology allowed hyperthermic treatment to be delivered to ocular structures in the form of ultrasound, microwave, or ferromagnetic energy. A novel technique, transpupillary thermotherapy, allows the direct application of hyperthermic energy to posterior segment ocular structures. The treatment of two posterior segment diseases, choroidal melanoma and choroidal neovascularization attributable to age related macular degeneration, are reviewed in this article.