In Combined Vitrectomy, Choroidal Structure Changes

Both choroidal vascularity index (CVI) and choroidal thickness (CT) increase following combined phacoemulsification and pars plana vitrectomy (PPV) with epiretinal membrane (ERM) and internal limiting membrane (ILM) peeling, according to a study published in BMC Ophthalmology. Previous studies have shown an increase in CVI and CT after cataract surgery and a decrease after PPV; however, the effects of combined surgeries on these choroidal parameters were unknown.

This retrospective study included 52 eyes of 26 patients (age, >50 years; 8 men) with cataracts and unilateral ERM who underwent combined vitrectomy and cataract surgery. All patients were evaluated between April 2020 and November 2021.

The eyes with ERM were allocated to group 1, and the fellow eyes were allocated to group 2. All eyes underwent ophthalmological examination, which included intraocular pressure (IOP) measurement, best corrected visual acuity (BCVA), axial length (AL) measurement, and fundus examination. All eyes were also imaged with spectral domain optical coherence tomography (SD-OCT) at baseline, 1 week, 1 month, and 3 months after the combined vitrectomy and phacoemulsification. For each visit, a 9 mm horizontal scan crossing at the center of the fovea was selected and exported for further analysis.

Choroidal thickness was measured manually, at the center of the fovea, and at 1.5 mm and 3 mm from the center at each side. Central macular thickness (CMT) was measured manually between the ILM and the RPE at the foveal center. The team exported the image into ImageJ and used a previously described image processing method to detect the total choroidal area (TCA), the luminal area (LA), and CVI, which was determined by calculating the ratio between LA and TCA.

Baseline CVI was significantly lower in the ERM group when compared with the fellow-eyes group (P =.011). After the combined vitrectomy and cataract surgery, the CVI was significantly increased at 1 week, 1 month, and 3 months (P =.007, P <.001, P =.049, respectively).

The study authors found thinner baseline subfoveal, 1.5 mm, and 3 mm nasal choroidal thickness in the ERM eyes than these of the fellow eyes (P =.023, P =.036, and P =.025, respectively). Choroidal thickness was significantly increased in the foveal center at 1 month, in the nasal 1.5 mm and 3 mm and temporal 3 mm locations at 1 week and 1 month postoperative, and in the temporal 3 mm at 3 months. Choroidal thickness decreased significantly from 1 week to 3 months postoperative in the subfoveal, temporal 1.5 mm, and nasal 1.5 mm locations.

CMT of the ERM eyes was significantly thicker at baseline when compared with the fellow eyes, and decreased in thickness significantly at 3 months postoperative.

Upregulation in the expression of pro-inflammatory cytokines in the choroid occurs after phacoemulsification and is also seen after PPV, according to the researchers.    

“Therefore, the upregulation of proinflammatory cytokines and the decreased IOP after surgery might cause an increased CVI/CT after combined vitrectomy,” according to the researchers. “Though the cause of ERM recurrence is unclear, greater surgical trauma and subsequent postoperative inflammation might increase the recurrence rate.”

The limitations of the study include a small sample and a short period of follow-up time.