Abstract
Purpose :
Pars plana vitrectomy (PPV) has been reported as a risk factor for primary open angle glaucoma (POAG) but the mechanism of this relationship is incompletely understood. Thinning of the nerve fiber layer (NFL) is a key aspect of POAG diagnosis but can also result from direct retinal injury. We aim to correlate NFL thinning on OCT with peri-operative retinal pathology to investigate if some cases of post-PPV POAG may include a component of direct retinal damage from the underlying retinal pathology or procedural aspects of the surgery.
Methods :
Cases were retrospectively identified from electronic medical records using a diagnosis of POAG or POAG-suspect (GS) within five years of retinal surgery in the affected eye. Retinal pathologies included epiretinal membrane, macular hole, retinal detachment, and retinal tears or ischemia requiring laser. OCT NFL thickness reports were abstracted and areas of NFL thinning for each clock hour were compared to diagrams of pre-op and intra-op retinal pathology overlaid on anatomic NFL tracts. Cases were assessed by two graders and coded as concordant if NFL thinning matched the areas of retinal pathology.
Results :
Of the 344 operative eyes that met inclusion criteria, 15 eyes were diagnosed with POAG and 17 as GS. Concordant NFL thinning and retinal pathology was present in 11/15 (73%) eyes with POAG and 5/17 (29%) eyes with GS. For POAG eyes, mean intraocular pressure at the time of diagnosis was 21.5 (SD 5.2) mmHg in concordant cases versus 28.6 (10.3) in discordant cases (t test p=0.092). For GS eyes, IOP was 15.0 (3.2) and 20.1 (4.1) in concordant and discordant cases, respectively (p=0.026). Of the cases with concordant OCTs, 9/11 (POAG) and 1/5 (GS) had visual field defects that corresponded to areas of retinal pathology. In a combined set of POAG and GS (32 eyes) 16 were concordant and 16 were discordant. Indocyanine green was used in 4/16 concordant cases and 2/16 discordant cases (chi square p=0.82). Intraocular gas was used in 8/16 concordant cases and 2/16 discordant cases (p=0.022).
Conclusions :
Some cases of clinically diagnosed glaucoma after retinal surgery may include NFL thinning due to the underlying retinal pathology or procedural aspects of the surgery. More studies are needed to determine causes of NFL thinning in patients who require PPV.
This is a 2020 ARVO Annual Meeting abstract.