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

Effect of choroidal blood perfusion and natural convection in vitreous humor during transpupillary thermotherapy (TTT)

During retinal surgical treatment often the gel-like vitreous humor is replaced by aqueous substitutes. A two-dimensional computational model is developed for simulating transpupillary thermotherapy (TTT) process in a human eye under post-retinal treatment. The model accounts for natural convection in vitreous humor and the choroidal blood perfusion. Time dependent and steady state forms of Pennes bio heat transfer and the natural convection governing energy equations are solved using finite volume formulation. The results for steady state and at the end of 60 s of the laser irradiated TTT process show that flow in vitreous humor is significant. The velocity contours indicate strong natural convection on the upper half of the vitreous chamber. Compared with the stationary vitreous case, the peak temperature in retina during TTT, drops by 15 K and 12.5 K due to natural convection flow in the vitreous humor under steady and transient states, respectively. The choroidal blood perfusion also reduces the peak retinal temperature by 6 K and 1.5 K in steady state and transient cases, respectively. The vitreous humor convection enhances heat transfer in the regions adjacent to the laser spot. The temperature rise and the associated thermal damage in the neighboring regions resulting from the flow of vitreous humor is presented.

Age-related macular degeneration revisited--piecing the puzzle: the LXIX Edward Jackson memorial lecture

PURPOSE

To present the current understanding of age-related macular degeneration (AMD) pathogenesis, based on clinical evidence, epidemiologic data, histopathologic examination, and genetic data; to provide an update on current and emerging therapies; and to propose an integrated model of the pathogenesis of AMD.

DESIGN

Review of published clinical and experimental studies.

METHODS

Analysis and synthesis of clinical and experimental data.

RESULTS

We are closer to a complete understanding of the pathogenesis of AMD, having progressed from clinical observations to epidemiologic observations and clinical pathologic correlation. More recently, modern genetic and genomic studies have facilitated the exploration of molecular pathways. It seems that AMD is a complex disease that results from the interaction of genetic susceptibility with aging and environmental factors. Disease progression also seems to be driven by a combination of genetic and environmental factors.

CONCLUSIONS

Therapies based on pathophysiologic features have changed the paradigm for treating neovascular AMD. With improved understanding of the underlying genetic susceptibility, we can identify targets to halt early disease and to prevent progression and vision loss.

Relationship between intensity of reflected light and temperature increase: assessment of fundus pigmentation for transpupillary thermotherapy

PURPOSE

To develop a new device for measuring reflected light during diode-laser irradiation in transpupillary thermotherapy (TTT) and to assess the correlation between fundus pigmentation, the measured intensity of reflected light, and the increase in fundus temperature.

METHODS

We developed a device to measure reflected light by modifying a slit-lamp-mounted 810-nm diode-laser delivery system used clinically for TTT. The diode laser was used to irradiate test charts with various degrees of reflectance in in vitro experiments, and the fundus of nonpigmented or pigmented rabbits in in vivo experiments; then, the intensity of the reflected light and the temperature increase at the target were measured. The retinal sections were also examined histologically.

RESULTS

There was a significant negative correlation between the intensity of the reflected light and the temperature increase in the target that depended on the degree of reflectance of the charts or the pigmentation of the rabbit eyes. On histopathologic examination, the extent of the changes in the irradiated retina after TTT was clearly different between pigmented and nonpigmented rabbits.

CONCLUSIONS

Correlations between fundus pigmentation, the intensity of reflected light during diode-laser irradiation, and the temperature increase in TTT were demonstrated in vitro and in vivo. Our results suggest that measurement of the intensity of reflected light should be helpful for modulating the laser power in TTT according to the degree of fundus pigmentation.

Long term results after transpupillary thermotherapy in eyes with occult choroidal neovascularisation associated with age related macular degeneration: a prospective trial

AIM

To evaluate long term results after transpupillary thermotherapy (TTT) in eyes with exudative age related macular degeneration.

METHODS

In a prospective clinical study eyes with occult or predominantly occult choroidal neovascularisation and no pretreatment were scheduled to have a TTT with a power of 630 mW. Visual acuity for far and near distances as well as contrast sensitivity were evaluated 6, 12, and 24 months postoperatively and statistically analysed.

RESULTS

47 eyes fulfilled the inclusion criteria. Overall, 70% of the patients showed an improved (14%) or had unchanged (56%) ETDRS vision after 24 months. Reading vision was stabilised (51%) or better (5%) in 56% of the eyes at this time. However, the increasing number of eyes with severe deterioration resulted in a significant decrease of both parameters over time (p = 0.0002 and p = 0.0003, respectively). Contrast sensitivity could be maintained (70%) or improved (9%) in 79%. Statistical analyses indicated a trend but no significant decrease over time (p = 0.056).

CONCLUSION

Although in the majority of patients far and near distance acuity could be stabilised on average a significant decrease over time after TTT was observed. Statistical comparison of months 12 and 24 showed no further deterioration.

Transpupillary thermotherapy for occult subfoveal choroidal neovascularization: a 1-year, prospective randomized pilot study

PURPOSE

To evaluate the 1-year effect of transpupillary thermotherapy (TTT) on occult choroidal neovascularization membranes (CNV).

METHODS

In this prospective, randomized, controlled pilot study of 28 patients with occult or minimally classic (< 10%) neovascularization membranes with a diameter less than 4500 microm, 19 patients were treated with TTT, while nine received sham treatment. Outcome measures were membrane diameter, visual acuity and reading ability.

RESULTS

The median age of patients randomized to TTT was 78 years (range 24 years); that of patients randomized to sham was 79 years (range 9 years). There was no difference regarding membrane diameter at baseline between the two groups; the median membrane diameters were 3400 microm (range 2400 microm) in the TTT group and 3200 microm (range 2300 microm) in the sham group (p = 0.639). Visual acuity (VA) was similar, with a median of 0.2 (minimum-maximum 0.08-0.5) in the TTT group and a median of 0.16 (min-max 0.10-0.32) in the sham group. A total of 21 patients were followed for 1 year, 13 in the TTT group (2.7 treatments/patient) and eight in the sham group. Membrane diameter increased in both groups, by a median of 350 microm (range 1600 microm) in the TTT group and 800 microm (range 1700 microm) in the sham group (p = 0.414), respectively, and there was a loss in VA of > or = 15 letters in 5/13 patients (38%) in the TTT group compared with 2/8 patients (25%) in the sham group (p = 0.266). Reading ability deteriorated equally over time in both groups. Seven patients were lost to follow-up due to reluctance to continue in the study (n = 4) or development of a classical component > 50% (n = 3) requiring photodynamic therapy (PDT).

CONCLUSION

The results from this randomized, prospective pilot study of TTT for occult CNV did not indicate that TTT has a beneficial effect on visual outcome 1 year after treatment compared with the visual outcome that results from the natural course of the disease. The small study size limits statistical power and results from large control studies are needed.

[Transpupillary thermotherapy for occult choroidal neovascularizations]

PURPOSE

This contribution describes the results of transpupillary thermotherapy (TTT) for age-related exudative macular degeneration (AMD) with regression.

PATIENTS AND METHODS

In exudative AMD with occult choroidal neovascularization (CNV), transpupillary thermotherapy (TTT) was performed using a diode laser (Iridex) in unselected patients. Before therapy and 1, 3, and 6 months after the initial treatment the patients were examined clinically. Additionally threshold testing in the 10 degrees field (Humphrey) and fluorescein angiographies were documented at all check-ups.

RESULTS

With respect to vision, differences in the slope of the regression lines between small, medium, and large CNV were significant (p<0.001). The slope of the regressions lines was significant except for small CNV. Regarding the 10 degrees field (Humphrey), there were no statistical differences in the slope of the regression lines (p=0.867).

CONCLUSIONS

Transpupillary thermotherapy with small CNV did not show a statistically significant decrease of VA. Thus, in clinical terms early treatment of occult CNV with TTT seems to be able to prevent a further loss of visual acuity.