25-Gauge anterior vitrectomy via the scleral ap in phacoemulsication combined with trabeculectomy for glaucoma and cataract with extremely shallow anterior chamber

Objective: To observe the safety and ecacy of a surgical technique of 25-gauge anterior vitrectomy via scleral ap in phacoemulsication combined with trabeculectomy for glaucoma and cataract with extremely shallow anterior chamber. Methods: This was a retrospective study composed with 18 eyes of 18 patinets (cid:0) 8 males and 10 females (cid:0) , including 11 eyes with acute angle closure glaucoma, 8 eyes with lens subluxation combined with glaucoma. All patients underwent phacoemulsication, intraocular lens (IOL) implantation, trabeculectomy, and anterior vitrectomy via the scleral ap in cases where conservative managements cannot control intraocular pressure (IOP). The main outcomes were best corrected visual acuity (BCVA), anterior chamber depth (ACD), IOP, slit lamp microscopic examinations, medications, fundus examinations and complications. Results: The average axial length (AL) was 21.5 ± 0.6 mm (range: 20.0 to 23.2 mm). Mean age was 62.3 ± 7.9 years old (range: 46 to 73 years). Mean ACD increased statistically signicant from 0.78 ± 0.43 mm to 2.89 ± 0.41 mm 1 week after surgery (P<0.001). Mean IOP decreased signicantly from 43.28 ± 9.38 mmHg to 16.72 ± 6.28 mmHg (P<0.001). There were no serious complications occurred, such as endophthalmitis, retinal detachment, suprachoroidal hemorrhage, corneal decompensation and malignant glaucoma. Conclusions: 25-Gauge anterior vitrectomy via the scleral ap was a safe and effective technology in glaucoma combined with cataract with extremely shallow anterior chamber.

Conclusions: 25-Gauge anterior vitrectomy via the scleral ap was a safe and effective technology in glaucoma combined with cataract with extremely shallow anterior chamber.

Background
As we all know, glaucoma with crowed anterior chamber and cataract was a challenge for ophthalmologists in surgery,which may lead to a series of complications, such as lens dislocation, corneal endothelial decompensation, iris prolapse, posterior capsular rupture. [1,2] The mechanism of narrow anterior chamber could be aqueous misdirection syndromes. Anterior vitreous displacement forward so that it faced against the ciliary body and lens preventing the normal aqueous humor ow. [3] The posterior pressure increased with the accumulation of aqueous humor in the posterior segment, which leads to the anterior displacement of the iris-lens diaphragm and extremely shallow anterior chamber. [2,4,5] The core of the treatment was to re-establish the anterior chamber to giving more space for surgical operation and create the communication to allow free diffusion of aqueous humor from vitreous to anterior chamber. However, the anterior chamber depth (ACD) cannot be deepened easily though the viscoelastic agents were injected in during surgery. [6] Chandler et al. [7] rst described the technique of vitreous aspiration by an 18-gauge needle via a pars plana incision to reformation of anterior chamber. The technique was later abandoned because of the high incidence of cataract and the risk of retinal detachment. With the development of technology, vitrectomy with microincision has been widely used in ophthalmology in recent years. Previous study have demonstrated the effectiveness of partial pars plana vitrectomy (PPV) in malignant glaucoma. [1] Zhang et al. [8] also veri ed that 23-gauge transconjunctival PPV combined with pars plana lensectomy (PPL) was helpful for glaucoma patients with cataract and shallow anterior chamber.
In our study, we used 25-gauge anterior vitrectomy via the scleral ap in phacoemulsi cation and trabeculectomy for glaucoma combined with cataract with extremely shallow anterior chamber to solve the problem of anterior chamber reformation during the operation. Postoperatively, patients received a standard treatment, including tobramycin dexamethasone eyedrops and nonsteroidal anti-in ammatory eye drops four times a day for 4 weeks. All glaucoma medications were discontinued. Additional therapeutic measures were taken if necessary. Postoperative examinations were arranged 1 week, 1 month and 3 month after the surgery. Additional reviews were scheduled depending on the condition.

Statistical analysis
Data were analyzed using SPSS software version 18.0. Normal distribution was assessed with the Kolmogorov-Smirnov test. A one-way analysis of variance (ANOVA) and LSD t-test was used to analyze the differences among groups. A P-value of < 0.05 was considered statistically signi cant.

Results
The basic information was presented in Table 1. The mean age was 62.3 ± 7.9 years (range: 46 to 73 years). The mean AL was 21.5 ± 0.6 mm (range: 20.0 to 23.2 mm). We observed a signi cant increase in ACD, the preoperative mean ACD was 0.78 ± 0.43 mm, postoperative mean ACD was 2.89 ± 0.41 mm, 2.97 ± 0.26 mm, 3.0 ± 0.29 mm respectively during the follow-up time ( Table 3). The IOP varied from 29.0 mmHg to 58.0 mmHg before operation, with a mean pressure of 43.28 ± 9.38 mmHg. And the IOP was 16.72 ± 6.28 mmHg on the rst week, which decreased signi cantly. IOP was 14.94 ± 5.17 mmHg, 14.28 ± 4.13 mmHg on the rst month, third month respectively. The BCVA was signi cantly improved in all cases which was listed in Table 4. No serious complications happened.  Discussion Glaucoma with extremely shallow anterior chamber and cataract was a complex clinical problem. High IOP and narrow anterior chamber for long time may lead to severe visual impairment, decompensation of the corneal endothelium and increasing the di culties during the surgery, including iris prolapse, capsular rupture, suprachoroidal hemorrhage, crystal dislocation, endothelial damage, malignant glaucoma. [1,9,10] It was showed that cilliary or pupillary blockage resulting in the forward displacement of the lens-iris diaphragm was the main mechanism. [6,11] When medical or laser treatment failed to induce IOP, surgical intervention is necessary. The main focus of the operation was how to overcome the di culties of surgery in the presence of high IOP and extremely shallow anterior chamber.
Chandler rst described the technique of vitreous aspiration by an 18-ga needle via a pars plana incision. [7] As the technology develops, microincisional vitrectomy surgery (MIVS) has been widely used in clinical practice, with the advantages of shorter operation time, faster wound healing, less trauma and reduced postoperative in ammation. Previous studies had com rmed that the e cacy of PPV was effective for softening the eye and deepening the anterior chamber through removing the anterior vitreous. [12][13][14] Sharma et al. [1] described vitrectomy-phacoemulsi cation-vitrectomy in management of malignant glaucoma. He et al. [15] also con rmed that clinical e ccy of modi ed partial PPV and phacoemulsi cation for malignant glaucoma. Zhang et al. veri ed that 23-gauge transconjunctival PPV and PPL was bene t to glaucoma and cataract patients with narrow anterior chamber. [8] In our research, all patients with high IOP and shallow anterior chamber responded no to medical therapy or laser iridotomy required surgical intervention. However, the anterior chamber was di cult to deepen during surgery. At the beginning of surgery, 25-gauge anterior vitrectomy was performed under the scleral ap in order to reduce positive posterior pressure. In this way, the eyeball softened and the anterior chamber deepened signi cantly. According to previous experience, we suggest that the removal of vitreous is about 0.5 ml according to Morgan. [16] Matlach et al. [17] suggested continuing to vitrectomy until the anterior chamber deepens intraoperatively. Then phacoemulsi cation, IOL implantation and trabeculectomy were operated with more space, decreasing the risk of surgery. Anterior chamber was formed and postoperative IOP was well controlled. The mean IOP was 16.72 ± 6.28 mmHg at rst week after surgery and maintained stability. At the last visit, the anterior chamber was remained well with a mean depth of 3.0 ± 0.29 mm. The BCVA was improved in all patients. There were no serious complications occurred, such as endophthalmitis, retinal detachment, suprachoroidal hemorrhage, anterior chamber disappearance, corneal decompensation and malignant glaucoma.
The advantages of this technology were as follows: rstly, it reduced the disturbance of conjunctiva and sclera with faster wound healing and less in ammation. Secondly, the scleral incision required no stitches with less time. Thirdly, it also reduced the incidence of malignant glaucoma. Aqueous uid from posterior chamber could ow into anterior chamber to reduce IOP. Fourthly, only one 25-gauge vitreous cutter was used during vitrectomy. It required no precorneal contact lenses, beroptic illumination probe or infusion, which can be easily operated with anterior segment surgeon. It is hoped that our experience will help to simplify the operation and achieve satisfactory result.