With the development of novel instruments and techniques, vitreoretinal surgery has been more and more widely used in the recent 50 years to treat a large variety of retinal pathology, such as retinal detachment, macular holes, epiretinal membranes, and proliferative vitreoretinopathy. Despite the accumulation of surgical experience, complications are still not rare in clinical practice, and some of which may have severe consequences. IOP elevation is one of the most common postoperative complications in vitreoretinal surgery. High IOP causes pain and discomfort in patients, more severely, the functionality of the eye may be permanently damaged. Therefore, a close monitor of IOP after vitreoretinal surgery is an important and routine examination in clinic. The incidence of postoperative IOP elevation has been reported as 3.6% to 22.2%; within 48 h, up to 40% of patients experienced an increased IOP [1-3]. Several risk factors have been related with high IOP after vitreoretinal surgery, such as the procedure of the surgery, the application of tamponade and the primary diseases of the patients [1,4,5]. However, these observations were conducted in different clinical studies separately; the data were collected from few hours to 1 day, or 1 month in the postoperative period [1,4-6]. The purpose of this study was to determine the incidence and rick factors of elevated IOP in the early stage (day 1, 2, 3, 4-7) after vitreoretinal surgery.

Patient cohort

Medical histories obtained from 150 patients (87 males and 63 females) undergoing vitreoretinal surgery between March, 2012 and December 2012 in Tongji Hospital were retrospectively reviewed. The average age was 50.1 ± 6.5 years (age range 3 to 79 years). As to the primary diseases, 14 eyes were oclular injuries, 36 eyes were PDR, 25 eyes were vitreous hemorrhage caused by retinal vascular diseases, 18 eyes were RRD with PVR grade ≥ C2, 88 eyes were RRD with PVR grade glaucoma or had family history of glaucoma, iris neovascularization, uveitis, prior intraocular surgery and penetrating eye injuries. All surgeries were performed by a single, experienced vitreoretinal surgeon. All the patients received 20G or 23G pars-plana vitrectomy (PPV). According to the intraoperative situation, additional procedures, such as scleral buckling, phacoemulsification with or without intraocular lens implantation, endolaser retinal photocoagulation, and endotamponades were performed during PPV. Endotamponades included balanced salt solution (BSS), gas (C3F8) and silicone oil. Operations ended up with normal IOP. Informed consent was obtained from all patients in this study.

IOP assessment

IOP was measured by Goldmann applanation tonometry on day 1, 2, 3, 4-7 after vitreoretinal surgery [6]. The average of 3 measurements was recorded.

Definition of IOP elevation

IOP elevation was defined as IOP ≥ 24 mmHg and prospective indication for treatment postoperatively was defined as ≥ 30 mmHg [7,8].

Follow-up and treatment for IOP elevation postoperatively

Patients were followed up at one week, 2 weeks, 4 weeks, 6 weeks, 2 months, 3 months, 6 months and 12 months. Examinations included best-corrected visual acuity (BCVA), IOP, anterior segment detection by slip lamp and fundus examination via indirect ophthalmoscopy. Eyes with IOP ≥ 30 mmHg were treated with topical or systemic antiglaucomatous medication, anterior chamber paracentesis, laser iridoplasty, and inferior iridectomy [9]. Oil removal with or without concurrent glaucoma surgery may be required in eyes with uncontrolled high IOP after silicone oil injection.

Statistical analysis

Statistical analyses were performed with SPSS 19 software (IBM, Armonk, NY, USA). Parametric data were presented as mean ± standard deviation (SD). Chi-square tests were used to compare the categorical data. P<0.05 was accepted as statistically significant.

Vitreoretinal surgery is an effective treatment for a large variety of retinal pathology. Despite the application of novel instruments and techniques, as well as the accumulation of surgical experience, complications are still not rare in clinical practice. IOP elevation is a common postoperative complication following vitreoretinal surgery. High IOP not only causes pain and discomfort in patients, but also impair the functionality of the eye. Several risk factors of high IOP after vitreoretinal surgery have been mentioned in different clinical studies separately [1,4,5]. This study systemically analyzed the incidence and rick factors of elevated IOP in the early stage (day 1, 2, 3, 4-7) after vitreoretinal surgery (Tables 3-5).

Table 3: The incidences of early IOP elevation in eyes performed vitrectomy combined with or without cataract surgery.

Table 4. The incidences of early IOP elevation in eyes performed vitrectomy combined with or without scleral buckling.

Table 5: The incidences of early IOP elevation after 20G or 23G PPV.

We found that most patients experienced high IOP at day 1 (57.40%) and day 2 (25.93%) postoperatively. In Han’s prospective study, around 60% of patients had an acute IOP rise within 2 days of PPV [10]. Possible mechanisms of IOP elevation included inflammation response, pupillary block, ciliary body edema and hemorrhagic complications [10,11]. Prolonged IOP elevation Longstanding increased IOP may occur if patients did not receive appropriate early intervention at this stage.

Several risk factors have been related with high IOP after vitreoretinal surgery, such as the primary diseases of the patients, the application of tamponade, and the procedure of the surgery [1,4,5]. We found that the incidences of elevated IOP between different primary diseases had no statistical difference. However, patients with PDR and RRD with proliferative vitreoretinopathy (PVR) grade ≥ C2, had higher rates of IOP elevation. Actually, Muether’s group reported that patients with PDR traction RD and primary RRD were at high risk for long-standing increased IOP [1].

Emulsification of the silicone oil and gas filling may also lead to early IOP rise [5,12,13]. We found that the incidence of IOP elevation with intraocular tamponade of C3F8 was significantly higher than simple vitrectomy, while with silicone oil, the difference was not significant. Therefore, silicone oil injection did not increase the rate of postoperative IOP elevation in the absence of emulsification. While the use of expanding gas tamponade may lead to increased IOP through iridocorneal apposition or pupillary block.

Hasegawa’s group showed that combined cataract surgery was a risk factor for IOP elevation [4]. However, another study reported that phacoemulsification could easily adjust and control IOP to reduce complications during and after the vitreoretinal surgery [14]. We found that combined cataract surgery in vitrectomy did not affect the incidence of early postoperative IOP elevation. Considering cataract surgery may be more challenging after vitrectomy, removing the lens with or without intraocular lens implantation can be performed if it is needed during surgery.

Placement of a scleral buckle intraoperatively was mentioned as a risk factor in early postoperative IOP elevation of vitreoretinal surgery [10]. However, our data showed that scleral buckling in vitrectomy did not affect the incidence of high IOP. The different results may be explained by the variety of the primary diseases of the patients and the experiences of the vitreoretinal surgeon. We also compare the incidences of early high IOP after 20G and 23G PPV. Results suggested that 20G PPV increased the rate of early postoperative IOP elevation.

In Zhang’s study, IOP was statistically significantly lower in the early stages after 23G PPV because of choroidal detachment [15]. However, we did not detect this complication in the follow-up of our patients. Again, the inconsistence of the results implicated the complex impact factors in early postoperative IOP elevation of vitreoretinal surgery.

In conclusion, early IOP elevation is a common complication after vitreoretinal surgery. IOP measurement after vitreoretinal surgery is important to monitor and prevent unintentional high IOP. The risk factors of early IOP elevation include the 20G pars-plana vitrectomy and C3F8 injection. Early treatment of IOP may prevent IOP spike to protect the vison.