Optic neuropathy causing vertical unilateral hemianopsia after pars plana vitrectomy for a macular hole: A case report

Abstract

Introduction: Recent progress in medical technology has resulted in improved surgical outcomes of pars plana vitrectomy (PPV); with microincision systems, the incidence of procedure-related complications during surgery has been reduced. However, unpredictable visual field defects after PPV remain an unresolved issue. A few reports have shown that damage to the retinal neurofibers owing to dry-up during air/fluid exchange or retinal neurotoxicity of the dye used to visualize the internal limiting membrane (ILM), as well as unintentional removal of retinal neurofibers during ILM peeling, are responsible for such visual field disorders. In this report, we present a case of extensive visual field defect due to optic neuropathy exhibiting vertical hemianopsia after PPV.

Case summary: A 50-year-old woman underwent PPV and cataract surgery for a macular hole and mild cataract under retrobulbar anesthesia with 3.5 mL of xylocaine. At the time of opening an infusion cannula for PPV, the intraocular lens was herniating, with an acute increase in pressure from the posterior eyeball; thus, intraocular pressure configuration level had to be decreased from the default level, whereas the other procedures including 20% SF6 injection were performed without any modification. The macular hole was closed postoperatively. However, the patient experienced nasal hemianopsia, which turned out to be optic neuropathy, as assessed via electric physiological examinations. The pattern of the visual field defect was not typical for glaucoma or anterior ischemic optic neuropathy. Her optic nerve head was pale at the temporal side soon after the surgery, and her blood pressure was low, suggesting that there may have been a congestion of the optic nerve feeder vessels because of the relatively high pressure in the orbit. The space occupancy with xylocaine and extensively stretched and plumped out eye ball with infusion during PPV may have pressed the surrounding tissue of the optic nerve and the feeder vessels.

Conclusion: PPV is safe for most patients; however, individual variations in local and/or systemic conditions may cause complications. Future studies to optimize the surgical condition for each individual patient may be warranted.

Figure 1

Ocular findings before and after the pars plana vitrectomy procedure. Preoperative fundus photography and optical coherence tomography performed on October 29, 2015 showed a macular hole in the patient's left eye (A). The macular hole was closed by February 22, 2016 (B). Goldman perimetry performed on May 16, 2016 (C) showed a nasal vertical visual field defect in her left eye. At this time, there were no right-left differences in the full-field (D) and multifocal (E) electroretinograms. However, the flash visual evoked potential was impaired in her left eye (F).