Phototherapy Effective for Pigment Epithelial Detachments

Laird Harrison

September 10, 2021

Photodynamic therapy (PDT) beats high-density subthreshold micropulse laser for treating pigment epithelial detachments (PEDs) in chronic central serous chorioretinopathy (CSC), researchers say.

The finding, from a subanalysis, adds to the conclusions of the PLACE trial, which showed better reduction of subretinal fluid with PDT. In addition, it highlights the importance of a treatment that has been hampered by a shortage of the drug verteporfin (Visudyne).

"I think this does indicate that half-dose PDT might be a solution for treating PEDs in chronic central serous chorioretinopathy, as well as other diseases with a thickened choroid background," said Helena Feenstra, a researcher at Leiden University Medical Center, Leiden, the Netherlands. She presented the findings at the European Society of Retina Specialists (EURETINA) 2021 meeting, which was held online.

Although most cases of acute CSC resolve spontaneously, about 15% entail chronic accumulation of subretinal fluid. Over time, this can cause irreversible damage to photoreceptors, impairing visual acuity.

PDT and micropulse laser are the two most common treatments for CSC. Both are used off label in most countries. Until the PLACE trial, published in 2018, there were few if any head-to-head comparisons of the two.

In the PLACE trial, 80 patients each received either PTD or micropulse laser. The mean age in both groups was 49 years. In the PTD group, 75% were men; in the micropulse laser group, 86% were men.

To reduce the risk for adverse events in the PTD group, the researchers injected half of the dose of the photosensitizer verteporfin that is injected when PTD is used as a treatment for neovascular age-related macular degeneration (nAMD),

Sixty-seven percent of patients treated with PTD had no subretinal fluid 7–8 months after treatment. By contrast, 28.8% of patients treated with micropulse laser had subretinal fluid in that time frame. The difference was statistically significant (P < .001).

The patients who received PDT also had better retinal sensitivity on microperimetry, and they had better visual acuity 6–8 weeks after treatment, though this faded to insignificance after 7 months.

"I would say PDT is the leading treatment, and micropulse laser was like a rising star; there was a lot of hope around it," said Dinah Zur, MD, head of the Center for Retinal Degenerations at Tel-Aviv Sourasky Medical Center, Tel Aviv, Israel, who was not involved in the study. "And PLACE very clearly showed that PDT is way superior to micropulse laser."

In this subanalysis, Feenstra and her colleagues compared the pigment epithelial detachments between the two groups. Healing the pigment epithelial attachment is crucial because it is the point through which fluid leaks.

At baseline, the researchers found a macular PED in 76.9% of the total patient population and a PED within 1500 μm of the foveal center in 37.5%.

The highest macular PED and the highest foveal PED both decreased more in the PTD group than in the micropulse laser group at both follow-up intervals. The decrease in highest height for the foveal PED was only significant at the first follow-up.

Table. Changes at 7–8 Months

  Highest height, macular PED, μm Highest height, foveal PED, μm
PDT -12.0 -15.0
Micropulse laser -3.0 -3.0
P value .012 0.065

 

No adverse events occurred with either treatment.

Feenstra pointed out that the findings only apply to PEDs in CSC, not PEDs that occur with other disease conditions. But the finding suggests that research into PDT could be useful.

The finding reinforces what clinicians have understood about PDT since the PLACE trial was published, said Zur. "It confirms that it is superior in treating the leakage point of the disease."

She said she was not surprised that the long-term visual acuity results were not significantly different between the two groups. CSC causes damage to photoreceptors that cannot be healed through either treatment. For this reason, patients are often disappointed because their vision does not improve, she noted. But healing the PEDs should stop the progression of the disease.

The finding highlights a challenge in treating CSC: a worldwide shortage of verteporfin. The drug was produced in high quantities when PTD was a primary treatment for nAMD and was therefore in demand, said Zur. Now that nAMD is mostly treated with antivascular endothelial growth factor drugs, verteporfin has become difficult to obtain.

Pharmaceutical treatments have also been shown to fall short, Zur said. "We are left with empty hands as physicians."

Zur and Feenstra have disclosed no relevant financial relationships.

European Society of Retina Specialists (EURETINA) 2021: Abstract 8034. Presented September 9, 2021.

Laird Harrison writes about science, health, and culture. His work has appeared in magazines, newspapers, and online publications. He is at work on a novel about alternate realities in physics. Harrison teaches writing at the Writers Grotto. Visit him at lairdharrison.com or follow him on Twitter: @LairdH.

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