Blood Reflux In Schlemm’s Canal Of Normal Cataract Patients: Simple Way To Identify The Trabecular Meshwork With Healthy Collector Channel Masahiro Maeda1, 2 *, Tetsushi Yasuma1, Mariko Maeda2 1Yasuma Eye Clinic, 2Maeda Eye Clinic, Nagoya, Japan The healthy outflow function of aqueous humor is an essential factor for the successful intraocular pressure (IOP) reduction after bypassing the anterior chamber (AC) to Schlemm’s Canal (SC) in canal surgery. Identifying the trabecular meshwork (TM) is the key for successful canal surgeries, such as Trabectome, iStent and other minimally invasive canal surgeries. Author introduced the intentional IOP lowering technique in Trabectome surgery to emphasize the location of TM with blood reflux. The safety and the percentage of successful identification of TM in this technique in normal controls are not known. Background To investigate the usefulness of blood reflux in Schlemm’s canal to identify the exact location of TM providing for healthy collector channel function To evaluate the safety of this procedure on the corneal endothelium cell density (ECD) Purpose A total of 90 eyes of 90 patients (age 72.0+/- 7.9 years-old, male 46, female 44) who underwent cataract surgeries by a single surgeon (M.M.) between May 2015 and December 2015 at Yasuma Eye Clinic and Maeda Eye Clinic were enrolled in this study.　The first 2 to 4 cataract cases of right eye in each day of surgeries were enrolled because of the limited number of sterilized goniolens.　All patients received and signed informed consent documents as required by the institution’s review board. The study followed the tenets of the Declaration of Helsinki.   Surgical procedure After creating the temporal clear corneal incision, IOP was reduced for 10 seconds by slightly tapping the incision. Care should be taken not touching the corneal endothelium to the iris. AC was deepened again by injecting the balanced salt solution or intracameral anesthesia. Tilt the microscope towards the surgeon, so that the patient’s head is set against the surgeon. TM was examined through the goniolens on the cornea. (Video: http://youtube/VWMcOlR7sT4) Evaluate the blood reflux in SC in simple staining degrees (Figure 1-3) followed by same site cataract extraction and intraocular lens (IOL) implantation. If blood reflux was not seen at the initial examination, TM was re-examined at the end of the surgery just after the hydration of the incision. ECD was compared between preoperative and six months post-op examination. Subject and Methods Inclusion criteria decrease of best-corrected visual acuity due to cataract, no history of glaucoma or ocular hypertension, and open angles (Shaffer grade I or above). Exclusion criteria corneal edema due to endothelial decompensation or opacities such as large pterygia preventing a good gonioscopic view, very shallow anterior chamber, history of glaucoma, ocular hypertension, uveitis, and any kind of ocular surgeries including the pterygium surgery. Grading of SC staining Figure 1. Grade 0: no blood reflux in the SC Figure 2. Grade 1: intermittent blood reflux in the SC Figure 3. Grade 2: continuous blood reflux in the SC No complication was seen during the surgery such as posterior capsule rupture, iris prolapse, and anterior chamber bleeding. Blood reflux in TM was seen in 84 cases (93.3%). Blood reflux was not clearly observed in 2 cases because of TM pigmentation at both initial and final examination. These cases were categorized in Grade 0. Four cases had no blood reflux at initial examination, but 3 of them showed blood reflux at the end of the surgeries. There was no statistical difference between pre- and 6 months post-operative ECD, 2494.9+/-415 and 2492.0+/-283.3 respectively (p=0.82). Results Blood reflux Staining Grade Initial exam. Final exam. Grade 2 57 (63.3%)   Grade 1 27 (30.0%) Grade 0 6 (6.7%) 1 (1.1%) 2 (2.2%) 3 (3.3%) Aqueous humor leaves SC either via collector channels to a complex network of aqueous venous plexuses or Ascher’s aqueous veins. Blood reflux is observed theoretically if IOP is lower than episcleral venous pressure. We utilized this phenomenon to emphasize the TM location, and found that more than 90% cases in presumably normal outflow function expressed blood reflux after lowering the IOP. Blood reflux was not clearly observed in 2 cases because of the pigmented TM. There is a possibility that intermittent blood reflux was hidden just behind the pigmented TM. But this technique is for finding the TM, so we did not confuse TM to other surrounding tissue. There was one case (82 year old female with normal IOP) that did not show blood reflux even at the end of the surgery. We supposed two possibilities for this case. The first is that we observed the TM at the end of the surgery, not just after the IOL implantation. IOP was raised by hydration of the incision to prevent the collapse of the AC. This may lead blood reflux to be disappeared. If we observe the TM just after IOL injection, we may find blood reflux in TM even in this case. The second possible reason is that 10 second was not enough reducing IOP for inducing the blood reflux from complex aqueous venous plexus network. The limitation in this study is its small number of subjects. Discussion Conclusions Blood reflux in SC by lowering the IOP is a simple and safe technique to identify the TM with healthy outflow function. This technique is useful for ab interno canal surgery, not only we can identify the exact target, but also we may be able to apply this technique for determining whether to continue canal surgery or switch to other glaucoma surgeries. References: 1) Kagemann L et al, Visualization of the Conventional Outflow Pathway in the Living Human Eye: Ophthalmology 2012;119:1563-1568 2) Kagemann L et al, 3D visualization of aqueous humor outflow structures in-situ in humans. Exp Eye Res: 2011; 93:308-315   Disclosures The authors have no financial and other relationships relevant to the subject matter of this poster to disclose.