Abstract
To report the frequency of hyphema after PRESERFLO® MicroShunt (PMS) surgery using double-step knife in patients with glaucoma and to investigate its relationship with the tube insertion position. Glaucoma patients who underwent PMS surgery were reviewed. Hyphema was defined as visible hemorrhage in the anterior chamber. The insertion position of PMS was confirmed via gonioscopy. Patient backgrounds in the hyphema and non-hyphema groups were compared, and the course of visual acuity (VA), intraocular pressure (IOP), and time to resolution of hyphema were investigated. 65 of 66 eyes were eligible for consideration. Hyphema had occurred in 23 (35%) eyes. At the end of surgery, anterior chamber bleeding was observed under the microscope in 8 of 23 cases (35%). The tube fixation position was on the scleral spur (25 eyes), on the trabecular meshwork (27 eyes), on the Schwalbe line (10 eyes) and on the corneal side (3 eyes). There was no significant difference of the site of tube insertion between the two groups. All cases of hyphema spontaneously resolved within a few weeks, with stable IOP and recovered VA. It is worth noting that in PMS surgery using the double-step knife, hyphema may occur high frequency even if the tube insertion site is accurately positioned. Patients should be informed of the risk of hyphema before the surgery.
Subject terms: Eye diseases, Outcomes research
Introduction
Trabeculectomy with mitomycin C (MMC) has stood as the gold standard for glaucoma surgery for over 20 years, serving as a versatile technique suitable for various types of glaucoma with guiding the aqueous humor under the anterior conjunctiva1–3. However, this technique comes with several complications that can diminish visual acuity (VA), such as overly low IOP due to over-filtration with shallow anterior chamber, hypotonic maculopathy4or choroidal detachment, and anterior chamber hemorrhage (hyphema), in the early postoperative period5. The issue of hyphema is particularly significant as it can impact not only VA but also bleb morphology management6 in neovascular glaucoma. However, concerns about similar outcomes exist not only for non-neovascular glaucoma but also other glaucoma following trabeculectomy.
Recently, the PRESERFLO® MicroShunt (formerly known as InnFocus MicroShunt7, InnFocus was acquired by Santen Pharmaceutical Co., Ltd., Osaka, Japan in 2016) (PMS), has emerged as a new drainage device for filtration surgery. This device allows the redirection of aqueous humor from the anterior chamber into the subconjunctival space by inserting a tube into the anterior chamber8–10. Although already in use in Europe, Canada, and some Asian/Pacific nations, PMS became available in select Japanese medical institutions (primarily university hospitals) as of February 2022. PMS includes an inert, biocompatible resin called poly(styrene-block-isobutylene-block-styrene) (SIBS)11, which boasts flexibility and high thermal durability. The device is an 8.5 mm long tube with a beveled tip, a 350 μm outer diameter, 70 μm inner diameter, and lacks a valve in its lumen. The tube features an overall length and inner diameter that take into consideration the regulation of IOP, prevention of tube occlusion, and risk of low IOP12. A fin structure (1.1 mm wide and 1.0 mm length) situated in the middle of the PMS ensures the device’s stability in the scleral pocket while anchoring the tube tip towards the anterior chamber. In addition to the purpose of securing the tube itself, the fin also serves to seal the scleral incision wound and prevent leakage from around the tube. In rabbit eyes implanted with SIBS glaucoma drainage implants, no encapsulation of the tube was observed at 6 months postoperatively, and aqueous humor outflow was observed, indicating that the implant is highly biocompatible13.
Although hyphema can arise due to bleeding from the angle during this perforation, the incidence of hyphema linked to PMS may be less than that of trabeculectomy, as the former lacks procedures with bleeding risks, such as iridectomy or scleral block removal. Instead, insertion of PMS into the anterior chamber is guided through a 25-gauge needle14–21or a 27-gauge needle16. Potential causes include bleeding of PMS from the scleral bed, reflux hemorrhage from the trabecular meshwork, and bleeding from the ciliary body. Early postoperative hyphema is associated with filtration surgery in 3.9–56% of trabeculectomies5,22–24 but only 3.5–20% of PMSs14–21.
In Japan, a unique scalpel called the double-step knife (MANI, Inc., Tochigi, Japan) is employed instead of a needle to create the scleral pocket and the tunnel leading to the anterior chamber during certain procedures. This tool, used not only in Japan but also in Australia and New Zealand, was manufactured with the aim of reducing the surgical time (one less step to change tools) and it is believed that using the double-step knife allows for improved precision, as it can be used to enter the anterior chamber in a single step.
The cause of the hyphema associated with PMS, although less than with trabeculectomy, is currently unknown. One valuable approach to understanding the cause of hyphema in relation to PMS is by confirming the tube’s insertion position within the angle, considering the possibility of reflux hemorrhage from Schlemm’s canal. However, there has yet to be a report confirming the actual insertion position through gonioscopy. This study focuses on the frequency of hyphema after PMS using a double-step knife, and exploratively investigated the relationship between the insertion site of the tube confirmed by gonioscopy and hyphema. Therefore, the effectiveness of the surgery and safety aspects other than anterior chamber bleeding are not the main subjects of this study.
Results
In all, 66 consecutive eyes underwent PMS surgery. The distribution of disease types was as follows: primary open-angle glaucoma (POAG; 52 eyes, 79%), secondary glaucoma (8 eyes, 12%), childhood glaucoma (4 eyes, 6.1%), and pseudoexfoliation glaucoma (2 eye, 3.0%). One eye was excluded from analyses due to corneal opacity, resulting in 65 eyes that were examined. Of these, gonioscopic examination determined the tube’s fixation position to be on the scleral spur side in 25 eyes (38%), on the trabecular meshwork in 27 eyes (42%), on the Schwalbe line in 10 eyes (15%), and on the corneal side in 3 eyes (4.6%) (Fig. 1a-d).
Fig. 1.
Tube insertion position after PRESERFLO® MicroShunt. The tube insertion sites are represented as follows: (a) scleral spur side, (b) trabecular meshwork, (c) Schwalbe line, (d) corneal side, respectively.
Postoperatively, 23/65 eyes (35%) exhibited hyphema: Grade 1 in 22 cases (Fig. 2), Grade 2 in one case (Fig. 3), and no instances of Grade 3. At the end of surgery, anterior chamber bleeding was observed under the microscope in 8 of 23 cases (35%). Hyphema was observed on the first postoperative day in 20 cases, while it occurred on the second day or later in 3 cases. A comparative analysis of patient backgrounds between the hyphema and non-hyphema cohorts is presented in Table 1. No significant differences in any factors between these two groups were identified. The mean IOP on the first postoperative day in the hyphema cohort was 9.8 ± 6.6 mmHg, and there was no significant difference compared to the mean IOP in the non-hyphema group (7.8 ± 2.8 mmHg) (P = 0.085).
Fig. 2.
Grade 1 hyphema after PRESERFLO® MicroShunt insertion. Hyphema fills less than one-third of the anterior chamber.
Fig. 3.
Grade 2 hyphema after PRESERFLO® MicroShunt insertion. Hyphema fills between one-third and one-half of the anterior chamber.
Table 1.
Comparison of patient background between hyphema group and non-hyphema group after PRESERFLO® MicroShunt surgery.
| Hyphema group n = 23 |
Non-hyphema group n = 42 |
P-value | |
|---|---|---|---|
| Age (years) | 63.6 ± 12.9 | 65.3 ± 13.5 | 0.62 |
| Tube inserting position (eyes) |
scleral spur 8 trabecular meshwork 13 Schwalbe line 2 cornea 0 |
scleral spur 17 trabecular meshwork 14 Schwalbe line 8 cornea 3 |
0.19* |
| Gender (male / female) | 9 / 3 | 17/ 14 | 0.31 |
| Laterality (right / left) (eyes) | 10 / 13 | 26 / 16 | 0.20 |
|
Insert portion (temporal / nasal)(eyes) |
17 / 6 | 25 / 17 | 0.29 |
|
Lens status (phakia / IOL / aphakia) (eyes) |
10 / 13 / 0 | 21 / 20 / 1 | 0.63* |
|
Surgical procedure (single / triple) (eyes) |
21 / 2 | 35 / 7 | 0.56 |
| Past glaucoma surgery (eyes) |
None 18, Exp. 2, MIGS 1, SLT 2, Trab 0 |
None 29, Exp. 2, MIGS 4, SLT 0, Trab 7 |
0.073* |
| Preoperative IOP (mmHg) | 21.5 ± 6.9 | 23.0 ± 8.1 | 0.44 |
| Preoperative medication score (number) | 3.2 ± 1.2 | 3.4 ± 1.1 | 0.48 |
| Past history of internal medicine (number) | None 16, HT 6, others 1 | None 27, HT 12, others 3 | 0.31* |
| Use of anticoagulant or antiplatelet drugs (number) | 3 | 5 | 1.0 |
*chi-squared test, IOL: intraocular lens, IOP: intraocular pressure, SLT: selective laser trabeculoplasty, MIGS: minimally invasive glaucoma surgery, Exp.: Ex-PRESS drainage implant, Trab: trabeculectomy, HT: hypertension.
The patient with Grade 2 hyphema, he was on anticoagulant therapy and had a history of controlled systemic hypertension. The platelet count was lower than the normal range in one case in the hyphema cohort (Grade 1 hyphema, 12,7 × 104/µL) and one case in the non-hyphema cohort (11.9 × 104/µL). In hyphema group, in 7 out of 23 cases, VA remained mostly unchanged even after bleeding. However, the remaining 16 cases experienced a decrease in visual acuity associated with bleeding. Its resolution occurred spontaneously within several weeks (it took up to 22 days for the hyphema to be absorbed, based on the date of examination), and VA reverted to the preoperative state in most cases. In a case where IOP increased to 38 (Case No. 8), flushing of the tube lumen was performed to relieve the obstruction (Table 2). Except for this one case, IOP management remained favorable.
Table 2.
A Time course of intraocular pressure and visual acuity until the disappearance of hyphema after PRESERFLO® MicroShunt surgery.
| Patient Number | Pre-ope. | POD 1 |
POD 2 |
POD 4 |
POD 5 |
POD 7 |
POD 8 |
POD 9 |
POD 10 |
POD 12 |
POD 13 |
POD 15 |
POD 20 |
POD 22 |
|
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | IOP | 18 | 8 (+) | 9 (+) | 9 (+) | 8 (-) | |||||||||
| VA | −0.08 | 0.82 | 0.40 | 0.22 | 0 | ||||||||||
| 2 | IOP | 28 | 10 (+) | 9 (+) | 10 (-) | ||||||||||
| VA | 0 | 0 | 0.046 | 0 | |||||||||||
| 3 | IOP | 16 | 6 (+) | 7 (+) | 7 (+) | 11 (+) | 10 (-) | ||||||||
| VA | 0.15 | 0.52 | 0.3 | 0.15 | 0.15 | 0.22 | |||||||||
| 4 | IOP | 24 | 7 (-) | 4 (+) | 5 (-) | ||||||||||
| VA | 0.15 | 0.3 | 0.52 | 0.52 | |||||||||||
| 5 | IOP | 27 | 6 (+) | 6 (+) | 8 (+) | 8 (+) | 6 (+) | 8 (-) | |||||||
| VA | −0.08 | 1.9 | 1.8 | 1.8 | 1.8 | 1.52 | 1.52 | ||||||||
| 6 | IOP | 17 | 5 (+) | 5 (+) | 8 (+) | 6 (-) | |||||||||
| VA | 0.15 | 1.9 | 0.82 | 0.52 | 0.52 | ||||||||||
| 7 | IOP | 21 | 10 (+) | 5 (+) | 14 (-) | ||||||||||
| VA | −0.08 | 0 | −0.08 | −0.08 | |||||||||||
| 8 | IOP | 18 | 10 (-) | 10 (+) | 38 (+) | 11 (+) | 10 (-) | ||||||||
| VA | 0.7 | 1.7 | 0.82 | 1.7 | 1.7 | 0.82 | |||||||||
| 9 | IOP | 15 | 7 (+) | 7 (+) | 7 (-) | ||||||||||
| VA | −0.08 | 0.15 | 0.22 | 0.097 | |||||||||||
| 10 | IOP | 28 | 8 (+) | 9 (+) | 8 (+) | 10 (+) | 8 (-) | ||||||||
| VA | 0.4 | 1.9 | 1.9 | 1.9 | 1.8 | 0.7 | |||||||||
| 11 | IOP | 28 | 7 (+) | 6 (+) | 7 (+) | 10 (-) | |||||||||
| VA | −0.08 | 0.22 | 0.15 | 0.097 | 0 | ||||||||||
| 12 | IOP | 12 | 5 (+) | 7 (+) | 6(-) | ||||||||||
| VA | 0 | 0.70 | 0.40 | 0 | |||||||||||
| 13 | IOP | 19 | 5 (+) | 9 (+) | 8 (-) | ||||||||||
| VA | 0.70 | 1.0 | 1.0 | 0.52 | |||||||||||
| 14 | IOP | 18 | 13 (+) | 11 (+) | 11 (+) | 11 (-) | |||||||||
| VA | −0.08 | −0.08 | 0 | −0.08 | −0.08 | ||||||||||
| 15 | IOP | 17 (+) | 7 (+) | 10 (+) | 9 (+) | 10 (-) | |||||||||
| VA | 0 | 0.22 | 0.046 | 0 | 0 | ||||||||||
| 16 | IOP | 16 | 9 (+) | 7 (+) | 10 (-) | ||||||||||
| VA | 0.30 | 0.52 | 0.40 | 0.40 | |||||||||||
| 17 | IOP | 32 | 6 (+) | 6 (+) | 6 (+) | 6 (+) | 11 (-) | ||||||||
| VA | 1.0 | 1.70 | 1.10 | 1.05 | 1.10 | 1.10 | |||||||||
| 18 | IOP | 18 | 6 (+) | 6 (+) | 6 (-) | ||||||||||
| VA | 0 | 0.22 | 0.22 | 0.15 | |||||||||||
| 19 | IOP | 20 | 7 (+) | 6 (+) | 8 (+) | 10 (-) | |||||||||
| VA | 0.52 | 2.0 | 2.0 | 1.0 | 0.70 | ||||||||||
| 20 | IOP | 17 | 7 (+) | 6 (-) | |||||||||||
| VA | −0.08 | 0 | −0.08 | ||||||||||||
| 21 | IOP | 15 | 4 (-) | 7 (+) | 7 (-) | ||||||||||
| VA | −0.08 | 0 | 0 | 0 | |||||||||||
| 22 | IOP | 35 | 11 (+) | 14 (+) | 13 (+) | 13 (+) | 10 (-) | ||||||||
| VA | 2.0 | 2.0 | 2.0 | 2.0 | 2.0 | 2.0 | |||||||||
| 23 | IOP | 36 | 6 (+) | 7 (+) | 7 (+) | 9 (-) | |||||||||
| VA | 0.52 | 0.4 | 0.15 | 0.15 | 0.10 |
IOP: intraocular pressure, VA: visual acuity (logMAR), POD: post operative day, (+) or (-) indicated with or without hyphema, respectively.
Discussion
Hyphema during the early postoperative phase of filtration surgery can compromise VA and detrimentally impact quality of life (QOL). In trabeculectomy, the most frequently identified sources of postoperative hyphema are the iris (including the ciliary body), vessels in Schlemm’s canal transects and scleral vessels. A main characteristic that distinguishes PMS from traditional trabeculectomy is its minimally invasive nature. The procedure entails only a conjunctival tenon incision and tunnel formation, omitting the steps of scleral flap creation, scleral block resection, and iridectomy. Therefore, while PMS may have a lower incidence of hyphema compared to trabeculectomy, there has been no specific study focusing on hyphema to date. Furthermore, there has been no rigorous confirmation of the tube insertion site after PMS using gonioscopy, and as a result, there had been still insufficient research on the potential relationship between hyphema and the insertion site. In the present study, employing the double-step knife for PMS surgery, adopted in Japan, resulted in a hyphema rate of 35%. In this investigation, gonioscopy was used to confirm the tube insertion site in all participants, no relationship could be found between the tube insertion site and the presence of hyphema. In the group with hyphema, there were no cases with poor IOP management in the short term. However, the long-term effects remain unclear, so careful observation is necessary to understand its potential impact.
Previous studies have documented hyphema frequency (without detailed grading) as a postoperative complication alongside IOP management of PMS. Most research has reported the utilization of a 25G or 27G needle for anterior chamber puncture. In a prospective study, 6/104 eyes (5.8%) experienced hyphema using a 25G needle15; other studies reported it in 1/8 eyes (13%) using a 25G needle 17and 2/23 eyes (8.7%) using a 1 mm wide Mani knife for scleral tunnel creation and a 25G or 27G needle for anterior chamber puncture16. A comparative study of trabeculectomy (26 eyes) and PMS (26 eyes) reported hyphema frequencies of 8% and 0%, respectively, using a 1 mm wide Mani knife for scleral tunnel creation and a 25G needle for anterior chamber puncture14. Retrospective studies have rates of 4.7% with a 25G needle18, 3.5% with a triangular-bladed knife for scleral tunnel creation and a 25G needle for anterior chamber puncture, 4.8% 20 and 20% 21 using a 1 mm wide Mani knife for scleral tunnel creation and a 25G needle for anterior chamber puncture. All of these studies only published the number of hyphema as a secondary evaluation. Thus, no studies had conducted on the location of tube fixation at the iridocorneal angle, in addition to the discussion of the cause of hyphema and patient background/medical history.
We exclusively used the specialized double-step knife, from the inception of the scleral tunnel to the final anterior chamber puncture. The precise source of PMS-induced bleeding remains undetermined, potential causes could include bleeding from the scleral bed via a scleral tunnel, which is created by a double-step knife. Characterized by a 0.5 mm leading edge and a peak width of 1.0 mm at the fin fixation, this knife possesses blades on both sides (Fig. 4), enabling the simultaneous incision of the left and right scleral tunnel floors. Although introducing PMS into the scleral tunnel augments its diameter, the resultant incision displays slight concavity (Fig. 4). This makes it more likely that the anterior chamber will receive blood from the scleral bed. Utilizing a needle would arguably reduce the likelihood of bleeding at these sites because only the leading edge of the sclera is incised. In a previous study, we used a needle to create the scleral tunnel and recorded no cases of hyphema17.
Fig. 4.
Cross-sectional view of the sclera following tunnel creation. Cross-section A: Tunnel width of 500 μm, tube diameter of 350 μm, with potential small spaces observed on both the left and right sides. Cross-section B: Tunnel width of 1,000 μm, with small spaces discernible on either side, as well. In both cases, the double-step knife incises the scleral bed, leading to bleeding (denoted by red dots) in the small spaces on both the left and right scleral beds, which may subsequently drain into the anterior chamber.
Another hypothesis included the reflux bleeding from the superior scleral artery adjacent to the puncture site of the tube. Near the corneal limbus, a major perforating branch derived from the anterior ciliary artery runs towards the intramuscular circle, and it is possible that this artery could be injured during perforation of the sclera with a double-step knife. However, in supporting this hypothesis, there are many aspects that are not known, such as where the perforating branches are distributed of the sclera. Moreover, we did not examine the insertion site with gonioscopy during surgery, we cannot make a definitive conclusion.
As anterior chamber puncture is a blind procedure, there is a potential risk of injuring the ciliary body, particularly if the puncture is positioned closer to the scleral spur side. In our research, we undertook gonioscopic evaluations to ascertain the tube fixation site in all participants. Of the 23 hyphema cases, PMS was anchored to the trabecular meshwork in 13 instances and positioned nearer to the scleral spur side in the remaining 8 cases. This suggests that hyphema might manifest even when PMS is accurately embedded into its designated fixation site on the trabecular meshwork.
It seems that the possibility of “reflux hemorrhage from Schlemm’s canal” was also considered as a potential factor. Regarding some cases where anterior chamber hemorrhage was observed on POD2, not on POD1, was likely attributable to the red blood cells floating in the anterior chamber on POD1 or a transient episode of hypotony between POD1 and POD2. Early postoperative gonioscopic examinations (using a goniolens) were avoided due to their invasive nature. Using anterior segment OCT to confirm the tube insertion site is a valid method. However, there is currently no consensus on angle segmentation, making precise evaluation of the insertion site challenging. Throughout the surgery and postoperatively, no bleeding was observed from the lumen of PMS. We also found no blood clots around the tube insertion site using a gonioscope in the cases presented.
In this study, anterior chamber bleeding was observed at the end of surgery in 8 cases, which could be attributed to inflow from the scleral bed or retrograde bleeding from episcleral arteries adjacent to the tube puncture site. Although this bleeding was not observed at the end of surgery in the remaining 15 cases, it is suggested that retrograde bleeding from Schlemm’s canal near the tube insertion site may have occurred due to postoperative hypotony a few hours after surgery. While accurately identifying the origin of hyphema the day after surgery remains challenging, this hypothesis seems plausible at present.
Although the direct comparisons of hyphema prevalence from the previous studies are not possible, a relatively high percentage of hyphema occurrences were observed in our study. The main difference from reports in other countries is primarily attributed to the method of creating the scleral tunnel, so we would assume that there is some relationship between the method of scleral tunnel creation and the frequency of hyphema. While some studies have suggested a possible link between anticoagulant consumption and intraocular hemorrhage subsequent to filtration surgery25–27, we did not find such an association. Further, in this study, we did not investigate coagulation factors, including PT-INR (Prothrombin Time-International Normalized Ratio), which remains a future task.
Hemorrhage could occur from the angle insertion site or from damage to the vessels in the scleral bed, resulting in similar bleeding. However, since we were unable to track the temporal changes in the first few postoperative hours, this remains speculative. In Japan, the use of PMS became available in 2022, and now, after a year has passed, the overall number of procedures is still relatively low. Therefore, it is necessary to investigate this further with a larger number of cases, including a history of previous surgeries. The primary surgical candidates for PMS are predominantly patients with POAG. Thus, the number of cases, such as secondary glaucoma, included in this study was still limited. As we move forward, a gradual increase in cases beyond POAG will allow us to explore differences among various disease types. Additionally, regarding anterior chamber bleeding, it is necessary to explore the advantages of PMS in terms of safety, based on the assumption that the risk and severity of occurrence might be lower compared to Trab.
Through the use of a distinctive double-step knife, we discovered that hyphema could develop in specific patients even when the tube was accurately anchored during operation. Due to the unexpectedly high frequency of hyphema when using the double-step knife, we have presented this investigation as a cautionary note. Further research is required to identify which demographic may be more prone to hyphema occurrence. After hyphema, visual acuity recovered in most cases within a few weeks, and there was almost no impact on IOP management. It is necessary to inform patients undergoing PMS surgery that there is a certain likelihood of postoperative hyphema, which may be accompanied by a transient decrease in visual acuity, and discussions regarding the technique of anterior chamber puncture might prove beneficial.
Materials and methods
All patients who received PMS surgery at Yotsuya Shirato Eye Clinic (Tokyo, Japan), due to inadequate IOP control or glaucoma progression between October 2022 and March 2023 were included in the study. This retrospective study adhered to the Declaration of Helsinki and received approval from the institutional ethics committee (approval ID: RSC-1811RB01). All patients provided written informed consent. Two glaucoma specialists (SS, MA) performed all consecutive surgeries. The inclusion criteria encompassed patients of both genders aged 20 years and older, who underwent PMS surgery, including simultaneous procedures, within the designated timeframe. No restrictions were imposed based on prior history of glaucoma surgery. Eyes with corneal opacity that hindered gonioscopy evaluation were excluded.
The surgical procedure entailed the following steps: injection of local anesthetic beneath the conjunctiva, followed by a fornix-based approach on the superior-temporal or superior-nasal side. After scleral coagulation, MMC (0.5 mg/mL for 1.5 min) was applied over the sclera. The MMC was subsequently washed off with a balanced salt solution (BSS), after which the path for PMS insertion into the anterior chamber was established using the dedicated double-step knife (Mani, Inc., Tochigi, Japan) (Fig. 5).
Fig. 5.
Shape of the double-step knife apex corresponding to the PRESERFLO® MicroShunt body. The leading portion is 500 μm wide, while the fin-fixed part measures 1,000 μm in width. A line is marked 4.5 mm from the tip, indicating the length of penetration into the sclera. After creating the scleral tunnel, the tube is inserted into the anterior chamber so that the fin in the middle of the PRESERFLO® MicroShunt tube is fixed at exactly 1,000 μm in width. The length of the tube exiting into the anterior chamber is roughly around 1 mm.
At a distance of 3 mm from the limbus, the knife was inserted to the 4.5 mm marker. This design ensures that the fin is positioned 3 mm from the ring and the tube’s distal length is precisely 3.0 mm. This results in approximately 1.5 mm of the tube protruding into the anterior chamber, which makes the tube tip visible. The fins of the tube were then confirmed to be firmly seated and fixed in the sclera. After confirming aqueous humor drainage from the distal end of the PMS, the tenon and conjunctiva were sutured using 10–0 nylon (Mani, Inc., Tochigi, Japan), ensuring that the distal end remained unobstructed. Following surgery, patients were prescribed corticosteroids and antibacterial eye drops to be used four times daily.
The presence or absence of hyphema was confirmed from the day after surgery, and the tube fixation position were assessed via gonioscopy (Goldmann type 3-mirror lens, Ocular Instruments, USA) within several months for all patients. The center of tube lumen location was categorized as on the scleral spur side, the trabecular meshwork, the Schwalbe line, or the corneal side (Fig. 6). Hyphema was characterized as visible hemorrhage sediment in the anterior chamber. Instances of mere suspensions of red blood cells in the anterior chamber, devoid of sediment, were not classified as hyphema. Hyphema severity was delineated into three grades based on slit-lamp examination28: Grade 1 (less than one-third of the anterior chamber), Grade 2 (between one-third and one-half of the anterior chamber), and Grade 3 (one-half or more of the anterior chamber).
Fig. 6.
PRESERFLO® MicroShunt insertion sites at the iridocorneal angle. They indicates, ① the scleral spur, ② the trabecular meshwork, ③ the Schwalbe line, and ④ the cornea, respectively.
Slit-lamp and fundus evaluations were included in every medical examination. IOP was measured using a calibrated Goldmann applanation tonometer (Haag-Streit, Wedel, Germany) during working hours after application of a topical anesthetic in the sitting position. VA was evaluated using the Landolt ring chart based on refraction readings.
Primary analyses focused on the occurrence and severity of hyphema after PMS. Secondary analyses compared patient background data, such as age, sex, eye side, insertion location, surgical procedure (single or triple), preoperative IOP, preoperative medication score, past history of internal medicine and usage of antiplatelet/anticoagulant medications, between hyphema and non-hyphema cohorts using the Student’s t-test. We also conducted a chi-squared test to determine whether there was an association between the insertion site and the presence of hyphema. Pre-surgery platelet counts were compared to normal reference values (male 13.1∼36.2, female 13.0∼36.9 [×104/µL]) (based on the value of SRL, SRL, Inc., Tokyo, Japan). Within the hyphema group, the IOP and VA trajectory were tracked until hyphema resolution, verified via medical records. All statistical evaluations were conducted using JMP Pro (version 17.0, SAS Institute, Cary, NC, USA) software. P < 0.05 was deemed statistically significant.
Author contributions
Conceptualization: S.S.; Methodology: S.S. Formal analysis and investigation: R.S.; Writing - original draft preparation: R.S.; Writing - review and editing: R.S., M.A., S.S.; Funding acquisition: N/A; Supervision: M.A., S.S.
Data availability
The data are not publicly available due to their containing information that could compromise the privacy of research participants.
Declarations
Competing interests
The authors declare no competing interests.
Conflict of interest
All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.
Footnotes
Publisher’s note
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