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Sir,

Transpupillary thermotherapy (TTT) has recently emerged as a first-line treatment modality for some selected small posterior uveal melanomas.1 This is largely because of the relative ease of performing the procedure on an outpatient basis, reduced costs compared with other modalities and perhaps, most important of all, few side effects and collateral damage depending on the location of the tumour. Currently, tumours posterior to the equator and measuring less than 10 mm in basal diameter and less than 3.5 mm in thickness can be predictably and safely treated with TTT.1 We herein report a patient with a small choroidal melanoma treated with TTT, who shortly after the treatment developed choriovitreal neovascularization that led to a chain of disproportionately severe complications.

Case report

In June 1999, a 63-year-old woman presented with gradual loss of vision in the left eye within 6 months. Except for chronic systemic hypertension, she was in good health. On examination, her best corrected visual acuity was 20/25 in the right eye and 20/60 in the left. Intraocular pressures and anterior segments were within normal limits except for the presence of 2+ nuclear sclerosis in the left eye. Left fundus examination revealed a circumscribed, partially amelanotic choroidal melanoma that measured 6.5 × 6.5 mm2 in basal dimensions and 3.5 mm in thickness (Figure 1). There was no overlying subretinal fluid. We performed TTT with confluent 3 mm spots at 550 mW power, each lasting 60 s. The procedure was repeated 6 months later with the same settings at 600 mW power. The tumour steadily regressed during the following 10 months until the patient presented with a mild vitreous haemorrhage. Her left visual acuity dropped to counting fingers. Choriovitreal neovascularization originating from the tumour was observed (Figure 2). The patient then was temporarily lost to follow-up. When she presented again in June 2001, a dense vitreous haemorrhage precluded any fundus view. A standard three-port vitrectomy was performed with sector endolaser photocoagulation also surrounding the tumour. The neovascular fronds rapidly regressed into fibrotic sheaths while the tumour thickness decreased to 1.5 mm. The visual acuity stabilized at 20/100. No tumour recurrence or metastasis was noted during later follow-up.

Figure 1
figure 1

Choriovitreal neovascularization: overall pretreatment view of the choroidal melanoma that is located 12 mm superior to the optic disc.

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Figure 2
figure 2

Choriovitreal neovascularization. The newly formed vessels extend from the anterior part of the tumour into the vitreous (upper left). The abnormal vessels become apparent as early as the choroidal circulation phase of fluorescein angiography (upper right). The early arterial filling phase demonstrates the full extent of neovascularization (lower left) that leaks profusely in the mid-venous phase (lower right).

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Comments

Infrared thermotherapy induces tumour cell necrosis, probably by disruption of intracellular mitochondria, through raising the local temperature between 45 and 60°C.2 Histopathological studies on eyes following TTT showed necrosis into a depth of 3.9 mm within the tumour and scattered haemorrhages between the necrotic and viable parts.3 However, no evidence of choroidal neovascularization was mentioned in this report. A recent study suggested that occlusion of choriocapillaris occurred in treated areas with choroidal vascular remodelling in 31% of the cases.3 In 10% of the cases, retinochoroidal anastomosis was the most prominent feature.4

Retinal vascular occlusions and retinal traction were identified as the most significant vision-threatening side effects of TTT.5 In fact, an analysis of 256 patients treated with TTT showed that retinal traction (44%) followed by branch retinal vein obstruction (41%) and branch artery obstruction (12%) were the most common complications.1 Neovascularization of the retina was seen in 6% of the cases.1 Other series found a similar incidence of side effects and also reported focal iris atrophy, preretinal fibrosis, cystoid macular oedema, disc oedema, nerve fibre bundle field defects, arteriolar sheathing, vitreous haemorrhage, subretinal and choroidal haemorrhages.5,6,7,8

Retinal neovascularization, as reported in the literature, results from occlusion of retinal vessels leading to ischaemia of the involved area. In our case, there was no retinal vascular occlusion and therefore no retinal neovascularization but choroidal neovascularization that occurred over the tumour suggesting direct damage to Bruch's membrane. Since amelanotic melanomas have poor heat absorption, we used relatively high powers to produce faint grey spots that were necessary to destroy the tumour in our judgement. This might have induced choriovitreal neovascularization. In a patient similar to ours, a chorioretinal anastomosis with a localized intravitreal neovascularization over the treated area developing 1 year after TTT was reported.8 This case was managed by additional TTT and sector panretinal photocoagulation.8 Given the dimensions of the tumour and other favourable associated findings, we had every reason to expect an uneventful tumour regression following TTT. At this juncture, our decision to employ TTT should be questioned. Perhaps a low-energy ruthenium-106 plaque would have been preferable, and we now believe that this would cause considerably less morbidity. This patient once again demonstrates that TTT is not an innocent procedure, and unexpectedly severe complications may develop in cases that initially appear as straightforward or ‘routine’.