Long-term intraocular pressure changes in eyes undergone vitreous removal by vitreoretinal surgery

OBJECTIVE: To examine the changes in intraocular pressure and the factors affecting it after vitreoretinal surgeries for epiretinal membrane (ERM), macular hole (MH), and vitreomacular traction syndrome (VMT), and to reveal the relationship between vitreous and intraocular pressure (IOP). MATERIAL AND METHODS: Forty-one eyes of 41 patients who underwent pars plana vitrectomy (PPV) with the diagnosis of ERM, MH, and VMT between January 2007 and April 2009 in the Vakıf Gureba Training and Research Hospital, Ophthalmology Clinic and who were followed up for at least 6 months in the postoperative period were retrospectively analyzed. An IOP between 6-2mmHg was accepted as "normal IOP", ≥22 mmHg was accepted as "high IOP", ≥4 mmHg higher from the fellow eye was accepted as "sustained IOP elevation". Paired t-test, independent t-test, Fisher's exact test, chi-square test, and percentage comparison test were used for statistical analysis. P-value ≤ 0.05 was significant. RESULTS: Twenty-four (58%) of 41 patients were female and 17 (41%) were male. The mean age was 67±9 years (mean±standard deviation) (range 32-87). Vitrectomy was performed for primary (idiopathic) ERM (n=14), ERM secondary to NPDR (n=10), ERM secondary to BRVO (n=2), VMT in the background of NPDR (n=2), idiopathic VMT (n=2), primary MD (n=10) and traumatic MD (n=1). The mean preoperative best corrected visual acuity (BCVA) of the cases was 1.0±0.5 lines on the LogMAR chart. The mean IOP was 15.3±3.2 mmHg in the operated eye and 15.5 ±2.2 mmHg in the fellow eye. Patients underwent 3-port 20G (20 Gauge) PPV (n=12), transconjunctival 23G PPV (n=29), phacoemulsification and intraocular lens implantation (Phaco-PPV) (n=5). BSS (n=12), sterile air (n=16), 20% SF6 (n=8) or 16% C3F8 (n=5) were left in the postoperative vitreous cavity. Iatrogenic peripheral retinal tear occurred in 1 patient, and the periphery of the tear was immediately surrounded by laser. BCVA increased significantly in the first year (p=0.024). The mean preoperative IOP in the vitrectomized eye was 15.2±3.1mmHg, 17.4±5.8mmHg at postoperative 1st month (P=0.018), 16.3±3.6mmHg at postoperative 3rd month (P=0.354), 17.3±2.6mmHg 6th postoperative month (P=0.02), 16.7±2.6mmHg at 12 months postoperatively (P=0.020). While the mean preoperative IOP was 15.2±3.1mmHg in the vitrectomized eye, it was 15.5±2.2mmHg in the fellow eye. There was no significant difference in IOP between the operated and the fellow eye (Independent-samples t-test, P=0.749). At the postoperative 1st month, the mean IOP of the vitrectomized eye (17.4±5.8mmHg) was higher than the fellow eye (15.2±1.8mmHg) (P=0.040). There was no difference between the mean IOP's at the postoperative 3 months (16.3±3.6mmHg vs 14.9±1.9mmHg, P=0.073). At the postoperative 6th month IOP of the vitrectomized eye was significantly higher than the fellow eye (17.3±2.6mmHg vs 15.2±1.71mmHg, p<0.001). At the 12th month, the IOP of the vitrectomized eye was significantly higher than the fellow eye (16.8±2.6mmHg vs 15.1±1.7mmHg, p<0.001). IOP ≥4mmHg higher from the fellow eye was not associated with the gauge of the instrument, etiology of PPV, age, lens status, presence, or the type of the tamponade. CONCLUSION: As the follow-up period increases, there is a significant increase in intraocular pressure compared to the preoperative values of the same eye and the simultaneous IOP of the fellow eye. This increase appears to start earlier in pseudophakic patients. The risk of developing open-angle glaucoma has been reported in patients during follow-ups for longer than four years. Long-term IOP should be monitored more closely in patients who underwent vitrectomy