What is the role of surgery in the treatment of choroidal neovascularization (CNV)?

Updated: Jan 07, 2019
  • Author: Lihteh Wu, MD; Chief Editor: Andrew A Dahl, MD, FACS  more...
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Answer

The Macular Photocoagulation Study (MPS) proved the efficacy of laser photocoagulation in the treatment of CNV secondary to ARMD, POHS, and idiopathic causes.

The goal is to completely obliterate CNV.

Partial treatment of CNV is not beneficial when compared to observation. Extrapolate these results to other conditions that are complicated by CNV on a case-by-case basis. Many patients and their physicians choose not to elect immediate loss or several lines of vision in an attempt to have a very modest visual improvement in 18 months. Extrapolation of MPS results to CNV secondary to myopia probably is not indicated in juxtafoveal CNV. Cases of enlargement of laser scars through the fovea with subsequent visual loss have been reported.

PDT uses light-activated drugs and nonthermal light to achieve selective destruction of CNV with minimal effects on the surrounding normal tissues. Randomized clinical trials have shown that PDT with verteporfin is effective in reducing visual loss in certain eyes with CNV secondary to ARMD. In eyes with at least some classic CNV, treatment with verteporfin reduced visual loss. Subgroup analysis revealed that eyes with a classic component of greater than 50% fared much better than those eyes with a classic component of less than 50%. In eyes with a classic component of less than 50%, no difference existed in visual loss between the eyes treated with placebo and the eyes treated with verteporfin. [48] Another study reported that therapy with verteporfin for occult CNV secondary to ARMD was effective in slowing the progression of visual loss. However, such benefit was only seen after the second year of follow-up. Subgroup analysis revealed that eyes with a visual acuity of 20/50 or worse or eyes with lesions smaller than 4 disc areas in size had a better outcome. Further analysis of the data revealed that lesion size rather than lesion composition is a strong predictor of visual benefit following PDT with verteporfin. [49] Despite all the encouraging initial results, PDT provides marginal benefit. Most eyes will continue losing vision, though at a slower rate, and only 15% of eyes will manifest some visual improvement. PDT in combination with intravitreal triamcinolone, bevacizumab, or ranibizumab may have better visual outcomes than PDT alone in patients with ARMD.

High-speed ICG confocal angiography guided laser photocoagulation of feeder vessels is reportedly beneficial in selected patients with exudative ARMD but remains unproven.

Uncontrolled studies have recommended surgical excision of subfoveal CNV via pars plana vitrectomy. The goal is to remove CNV but to leave the underlying RPE and choriocapillaris intact. Surgical excision of type 2 CNV would be more beneficial than type 1 CNV. Pilot studies resulted in substantial numbers of patients with worse vision, many with unchanged vision, and a small number with apparent improved vision. The current rhetoric is that stabilization may occur with surgery. [50] The Submacular Surgery Trial (SST), a randomized multicenter prospective trial sponsored by the National Eye Institute (NEI), confirmed that submacular surgery in eyes with CNV secondary to ARMD generally does not have a good visual outcome. [51] In addition, with CNV secondary to idiopathic causes and POHS, submacular surgery offers a modest benefit in eyes with a baseline visual acuity of 20/100 or worse.

Two surgical methods to translocate the fovea have been developed to treat subfoveal CNV. The previously subfoveal CNV is now juxtafoveal or extrafoveal; then, standard laser photocoagulation or PDT can be performed without damaging the fovea. Caution is warranted because high rates of retinal detachment, proliferative vitreoretinopathy (PVR), macular holes, recurrent CNV, cystoid macular edema (CME), and hemorrhage have been reported.

Low-dose radiation therapy has been effective in inhibiting neovascularization in different tissues. A randomized clinical trial reported better visual outcomes in eyes with exudative ARMD receiving radiation therapy of 24 Gy given in 6 fractions of 4 Gy each compared to observation. [52] However, other trials do not support radiation therapy as a treatment alternative in eyes with CNV secondary to ARMD. Long-term effects are unknown, and radiation retinopathy is definitely a concern.


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