title: Transient reduction in retinal function revealed by multifocal electroretinogram after photodynamic therapy.
abstract: OBJECTIVE
  To evaluate the early changes in retinal function after photodynamic therapy (PDT) by multifocal electroretinogram (mfERG).
  
  
  METHODS
  Prospective interventional case series.
  
  
  METHODS
  Seventeen eyes from 17 patients scheduled for standard PDT with verteporfin were prospectively recruited. Patients' diagnoses included choroidal neovascularization (CNV) secondary to age-related macular degeneration, idiopathic CNV, myopic CNV, polypoidal choroidal vasculopathy, and central serous chorioretinopathy. Serial mfERG recordings were performed before PDT, and at 4 days, 2 weeks, and 1 month after PDT. The first-order kernel N1 and P1 mfERG response from the central 0 to 7 degrees and peripheral 7 to 25 degrees were grouped and analyzed. The mean response amplitudes and peak latencies of the mfERG recordings were compared longitudinally.
  
  
  RESULTS
  There were statistically significant reductions in the mean N1 response amplitude for the central group at 4 days (P =.007) and 2 weeks after PDT (P =.024), in the mean P1 response amplitude for both the central (P =.006) and peripheral (P =.013) groups at 4 days, and for the central group at 2 weeks after PDT (P =.017). There were also statistically significant increases in the mean P1 response latencies at 4 days (P =.004) and at 2 weeks (P =.018) after PDT for the central group and at 4 days after PDT (P =.026) for the peripheral group. At 1 month after PDT, no significant differences in the N1 and P1 mean response amplitudes and peak latencies were observed compared with pre-PDT mfERG.
  
  
  CONCLUSIONS
  Transient impairments in retinal function for as long as 2 weeks after PDT were noticed by reduction in response amplitudes and a delay in peak latencies of mfERG. These findings may explain the common adverse event of subjective visual disturbance early after PDT with normal findings in visual acuity and ophthalmoscopy.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Hong Kong Eye Hospital, 147K Argyle Street, Kowloon, Hong Kong, China.
authors.forename: Timothy Y Y
authors.initials: TY
authors.lastname: Lai
authors.forename: Wai-Man
authors.initials: WM
authors.lastname: Chan
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D000368:Aged; D020256:Choroidal Neovascularization / Q000188:drug therapy / Q000209:etiology; D004596:Electroretinography / Q000379:methods*; D005260:Female; D006801:Humans; D008268:Macular Degeneration / Q000150:complications; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000150:complications; D010778:Photochemotherapy / Q000009:adverse effects*; D017319:Photosensitizing Agents / Q000009:adverse effects / Q000627:therapeutic use; D011166:Porphyrins / Q000009:adverse effects / Q000627:therapeutic use; D011446:Prospective Studies; D012160:Retina / Q000187:drug effects / Q000503:physiopathology*; D012164:Retinal Diseases / Q000139:chemically induced / Q000503:physiopathology*; D000077362:Verteporfin; D014786:Vision Disorders / Q000139:chemically induced / Q000503:physiopathology; D014792:Visual Acuity
chemical_list: D017319:Photosensitizing Agents; D011166:Porphyrins; D000077362:Verteporfin