Acute primary angle closure is an important cause of blindness in East Asia . In China, an estimated 28 million individuals have occludable drainage angles . The risk of developing AAC is three times higher in women than in men . Consistent with this, women comprised 76.5% of our study population. In addition to an effect of race, the incidence of AAC rises steeply with age, which may result from age-related increases in lens thickness, decreased ACD, and an anteriorly moved lens center . A significant proportion of patients with AAC do not respond adequately to medical treatment alone. In such cases, it is important understand how to perform surgery safely and effectively .
Intraoperative procedures, such as corneoscleral wound incision capsulorhexis, cortex aspiration, and insertion of the foldable intraocular lens, are difficult to perform in eyes with a shallow anterior chamber. A shallow chamber poses an increased risk of endothelial cell loss, as the phaco tip is closer to the endothelium during nucleus emulsification . In addition to endothelial cell loss, iris damage, intraoperative pupillary constriction, capsulorhexis tear or capsular rupture, subluxation of lens material, and vitreous loss may occur during the phacoemulsification in AAC because of a shallow anterior chamber and positive pressure . Although limited pars plana vitrectomy is currently considered to be only way to successfully deepen the anterior chamber , vitreous tap using needle aspiration is a simple and effective alternative.
The main risk involved in our technique is the potential for vitreous traction . Some scholars believe that the use of a vitrectomy cutter to remove vitreous decreases the potential for vitreous traction compared to a needle aspiration technique . However, in a large, multicenter study on endophthalmitis vitrectomy, there was no significant difference between vitreous needle aspiration and automated vitrectomy regarding posterior segment complications and the final visual outcome over a follow-up period of 9–12 months . Additionally, our patients were older and had posterior vitreous detachment and liquefaction; therefore, the vitreous fluid could be successfully extracted without vitreous traction and other complications. Furthermore, rapid breakthrough of the vitreous cortex into the liquefied vitreous lacuna during puncture is key to success. In the present study, vitreous puncture with vitreous needle aspiration was performed to remove 0.2 ml of vitreous; because of the small volume of the aspiration, the vitreous could be successfully aspirated in most cases without increasing the risk of retinal traction. Although it could lead to posterior displacement of the lens, this technique deepened the anterior chamber, decreased the IOP and positive vitreous pressure, and reduced the chance of posterior capsule rupture and suprachoroidal hemorrhage.
Considering the cost of the surgery and the potential cardiovascular and respiratory risks, we did not select general anesthesia. Instead, we injected lidocaine under the conjunctiva after topical anesthesia because it did not increase the vitreous and orbital pressures. Furthermore, common needles and syringes were used in the aspiration; there is no need to use expensive vitrectomy supplies. In the developing world, where healthcare institutions impose strict controls on cataract surgery costs, the use of vitrectomy increases the cost. In contrast, our technique reduces the operative time and surgical scope, does not require suturing of the puncture site, and creates favorable surgical conditions for phacoemulsification. Increased anterior chamber space and decreased IOP renders uneventful cataract phacoemulsification possible and reduces the risk of corneal endothelium injury. Consistent with the previous literature , the vitreous was successfully extracted on the first attempt, the phacoemulsification surgery was successfully completed, the postoperative vision was improved, and anti-glaucoma drugs were not required to maintain the IOP within the normal range for all patients in the current study.