Swept-source intraoperative optical coherence tomography for real-time detection of anterior segment membranes during cataract surgery: a case series

Abstract

Background

Visualization of delicate membranous structures during cataract surgery is often limited under conventional surgical microscopes, particularly when tissues are transparent or obscured. This study aimed to evaluate the intraoperative visualization of delicate membranous structures during cataract surgery using swept-source intraoperative optical coherence tomography (SS-iOCT).

Methods

This retrospective observational case series was conducted at the ophthalmology center of a Grade-A tertiary hospital in China. Six eyes of six patients [mean age, 55.3 years; 5 males (83.3%)] undergoing cataract surgery were included in the case series. The cases included Descemet’s membrane detachment, cataract with exfoliative material, traumatic cataract, and age-related cataract. A microscope-integrated SS-iOCT system was used to obtain real-time, depth-resolved, cross-sectional images during surgery.

Results

SS-iOCT successfully captured high-resolution images of all eyes (100%), revealing subtle membranous structures undetectable under the surgical microscope. The system delineated fine separation planes, penetrated opaque media to reveal hidden lesions, identified posterior capsule ruptures, and visualized transparent structures, including the anterior hyaloid membrane. In five of the six eyes (83.3%), the intraoperative findings directly influenced the surgical strategy, enabling procedural modifications that enhanced safety and accuracy.

Conclusions

SS-iOCT expands the intraoperative field of view, providing real-time recognition of subtle pathological and normal anterior segment membranes beyond the capacity of surgical microscopes. These actionable insights may guide surgical decision-making and support safer, more precise cataract surgery.

Introduction

The accurate intraoperative identification of membranous structures in the ocular anterior segment during cataract surgery is critical but often challenging. This challenge is especially pronounced in eyes with trauma, mature white cataracts, or corneal opacities (1-3). Under such conditions, surgical microscopes provide limited resolution of delicate membranes, rendering their recognition largely dependent on the surgeon’s experience. Consequently, intraoperative complications involving membranes, such as Descemet’s membrane detachment (DMD) and posterior capsule rupture (PCR), may go undetected (4), thereby increasing the risk of adverse surgical outcomes.

Intraoperative optical coherence tomography (iOCT) provides high-resolution, cross-sectional imaging of the anterior segment, allowing surgeons to visualize delicate membranous structures that often remain hidden under conventional en-face surgical microscopes (5-9). However, earlier iOCT systems were limited by shallow scan depths, restricted scan ranges, slow acquisition speeds, and insufficient tissue penetration through opaque media (10). These limitations compromised image quality and hindered continuous real-time guidance during cataract surgery, limiting the role of earlier iOCT in facilitating the intraoperative recognition of membranous abnormalities.

Swept-source iOCT (SS-iOCT) addresses these limitations. With faster acquisition speeds, increased scan depths and widths, and improved tissue penetration, SS-iOCT enables the reliable, full-field visualization of the anterior segment in real time. These technological advances provide cataract surgeons with an enhanced tool for detecting subtle membranous structures, minimizing intraoperative blind spots, and improving surgical safety.

In this case series, we report on six eyes of six patients undergoing cataract surgery in which SS-iOCT successfully identified anterior segment membranous abnormalities or anatomical structures that were inconspicuous or ambiguous under en-face surgical microscope. These cases underscore the clinical value of SS-iOCT in the real-time visualization of delicate structures, facilitating improved surgical decision-making and optimizing intraoperative assessment. We present this article in accordance with the AME Case Series reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2025-aw-2237/rc).

Methods

Patients

The SS-iOCT system was routinely used in all cataract surgeries performed by our medical team. This study retrospectively analyzed six intraoperative videos from cataract surgeries. All the enrolled patients underwent routine cataract surgery at the Eye Center of the Second Affiliated Hospital, School of Medicine, Zhejiang University. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board (IRB) of the Second Affiliated Hospital, School of Medicine, Zhejiang University (No. IR2024426). Given the retrospective nature of the study and the use of anonymized clinical data, the requirement for written informed consent was waived by the Institutional Review Board. A certified and clinically approved SS-iOCT device, integrated into the surgical microscope, was used in this study for routine intraoperative imaging during standard ophthalmic procedures.

Data collection

Intraoperative imaging was performed using a commercial digital SS-iOCT-integrated surgical microscope (FO-313, TowardPi Medical Technology Co., Ltd., Beijing, China). The system operated at a central wavelength of 1,060 nm with a scan speed of 100,000 A-lines per second. The B-scan imaging protocol (2,048×1,536 pixels) covered a depth of 12.0 mm and a width of 16.0 mm, with an axial resolution in air of 7.9 µm (7). The clinical data of the patients, including their baseline characteristics, preoperative evaluations, intraoperative findings, and postoperative outcomes, were systematically reviewed.

The preoperative and postoperative assessments included best-corrected visual acuity (BCVA), corneal endothelial cell density (ECD), and intraocular pressure (IOP). Postoperative evaluations were conducted at 1 month (±1 week). ECD measurements were obtained using a specular microscope (EM-4000, Tomey Corporation, Nagoya, Japan), while IOP was measured with a non-contact tonometer (NIDEK NT-530P, NIDEK Co., Ltd., Gamagori, Japan).

Results

Patient characteristics

In total, six cases (Patients 1–6) were included in the analysis. The baseline demographic and clinical characteristics of the patients are presented in Table 1. Table 2 provides a summary of the patients’ clinical diagnoses, alongside the membranous abnormalities and anatomical structures identified intraoperatively using SS-iOCT.

Table 1. Patient demographics and clinical characteristics.

Parameters	Value (n=6)	P value
Demographics
Age (years)	55.33±23.36
Gender (male)	5 (83.3)
Eye (right)	3 (50.0)
BCVA (LogMAR)		0.045*
Preoperative	1.07±0.97
Postoperative	0.58±0.78
ECD (cells/mm2)		0.066
Preoperative	2,437.00±649.57
Postoperative	2,261.20±549.52
IOP (mmHg)		0.269
Preoperative	14.65±4.08
Postoperative	12.07±1.81

Data are presented as the mean ± standard deviation or n (%). *, P<0.05 was considered statistically significant and analyzed using the paired t-test. BCVA, best-corrected visual acuity; ECD, endothelial cell density; IOP, intraocular pressure; LogMAR, logarithm of the minimum angle of resolution; mmHg, millimeters of mercury.

Table 2. Summary of membranous abnormalities and structures detected by SS-iOCT during cataract surgery.

Cases	Membranous structures	Diagnosis	Visualization under the surgical microscope	Visualization under SS-iOCT
1	Elevated corneal epithelium-Bowman’s layer	Metabolic cataract, diabetes	1A: visible. A localized corneal epithelial bulge with distinct margins appeared, but the separation plane was indiscernible	1B: visible. Elevation of the corneal epithelium-Bowman’s layer was revealed, clearly demonstrating separation from the underlying stroma
2	Detached Descemet’s membrane	Complicated cataract, chronic uveitis	2A: invisible. DMD could not be recognized due to corneal edema	2B: visible. A focal DMD was identified at the site of the side-port incision, characterized by a limited area of separation, shallow detachment, and a folded morphology
3	Anterior capsule with lamellar separation and superficial split	Complicated cataract, true exfoliation syndrome	3A: partially visible. The anterior capsule split was visible, but the specific capsule layer involved could not be distinguished	3B: visible. Lamellar separation of the anterior capsule with a superficial split was shown with an intact underlying layer of the anterior capsule
4	Curling of the anterior capsule edge	Traumatic cataract	4A: invisible. The anterior capsule curling was obscured due to a dense corneal scar	4B: visible. Curling of the anterior capsule edge was revealed
5	Ruptured posterior capsule	Traumatic cataract	5A: partially visible. A possible PCR was suggested under the surgical microscope, but the rupture margins and associated vitreous involvement were indistinct	5B: visible. The margins of the PCR and the related vitreous prolapse into the anterior chamber were more clearly delineated
6	AHM	Age-related cataract	6A: invisible. AHM and its separation forming Berger’s space could not be visualized	6B: visible. The posterior capsule and AHM were identified as separate structures, with their separation forming Berger’s space

AHM, anterior hyaloid membrane; DMD, Descemet’s membrane detachment; PCR, posterior capsule rupture; SS-iOCT, swept-source intraoperative optical coherence tomography.

SS-iOCT-based recognition of ocular anterior segment membranous structures

Corneal membrane identification

Patient 1, who had a metabolic cataract complicated by diabetes, presented with a localized, blister-like corneal elevation with well-defined margins under the surgical microscope (Figure 1A). SS-iOCT was employed to clarify the plane of suspected corneal detachment that could not be resolved under surgical microscope. Despite its apparent prominence, the exact plane of separation could not be determined. Notably, SS-iOCT revealed that the detachment lay precisely between the corneal epithelium-Bowman’s layer and the underlying stroma, resulting from fluid accumulation during irrigation (Figure 1B).

Figure 1.

Surgical microscopic view (A) and corresponding SS-iOCT image (B) demonstrating a corneal epithelial-Bowman’s layer elevation caused by irrigation fluid accumulation. SS-iOCT, swept-source intraoperative optical coherence tomography.

Patient 2, who had a complicated cataract secondary to chronic uveitis in a quiescent phase, presented preoperatively with mild corneal edema, Descemet’s membrane folds, peripheral anterior synechiae, and posterior synechiae of the pupil. SS-iOCT imaging was performed to detect and characterize possible DMD obscured by corneal edema. Intraoperatively, a focal DMD was observed adjacent to the side-port incision. SS-iOCT vividly delineated the detachment in a folded configuration with sharply defined margins, features that remained imperceptible under the surgical microscope (Figure 2A,2B).

Figure 2.

Surgical microscopic view (A) and corresponding SS-iOCT image (B) showing a localized DMD. DMD, Descemet’s membrane detachment; SS-iOCT, swept-source intraoperative optical coherence tomography.

Lenticular membrane identification

Patient 3, who had a complicated cataract, exhibited a visible split in the anterior capsule under the surgical microscope; however, it was unclear whether this finding represented true capsular splitting or superficial exfoliative changes (Figure 3A). To clarify the underlying structural basis of the anterior capsular abnormality, SS-iOCT was employed for intraoperative cross-sectional assessment. SS-iOCT imaging showed a hyperreflective superficial layer consistent with exfoliative material, with a focal defect and partial separation from the underlying intact anterior capsule, excluding true multilayer capsular splitting and providing real-time confirmation of capsular integrity (Figure 3B).

Figure 3.

Surgical microscopic view (A) and corresponding SS-iOCT image (B) revealing exfoliative material on the anterior lens capsule. SS-iOCT, swept-source intraoperative optical coherence tomography.

Patient 4, who had been diagnosed with a traumatic cataract following ocular trauma caused by impact from a fabric bag, presented with a shallow anterior chamber, anterior capsule rupture, lens cortex prolapse, and a sutured oblique, irregular corneal laceration. Dense corneal scarring significantly compromised the microscopic field of view (Figure 4A). SS-iOCT was used to investigate the integrity and configuration of the anterior capsule in the setting of poor visualization due to corneal scarring. SS-iOCT cross-sectional imaging successfully captured the curling of the ruptured anterior capsule edge, which could not be visualized under the surgical microscope (Figure 4B).

Figure 4.

Surgical microscopic view (A) and corresponding SS-iOCT image (B) illustrating curling of the anterior capsule edge in a patient with a central corneal scar. SS-iOCT, swept-source intraoperative optical coherence tomography.

Patient 5, who had a traumatic cataract secondary to a wooden stick injury sustained some two decades earlier, exhibited posterior synechiae and lens opacity. During surgery, PCR occurred following lens nuclear removal, and the precise delineation of the rupture margins under the surgical microscope proved challenging (Figure 5A). The clinical objective was to assess posterior capsule integrity and detect vitreous prolapse following intraoperative PCR. SS-iOCT provided precise visualization, clearly showing two distinct ruptured posterior capsule margins, along with hyperreflective vitreous strands extending anteriorly toward the incision, consistent with vitreous prolapse (Figure 5A), definitively confirming the extent of the posterior capsule defect (Figure 5B) and guiding immediate surgical management.

Figure 5.

Surgical microscopic view (A) and corresponding SS-iOCT image (B) demonstrating a PCR with anterior vitreous prolapse. PCR, posterior capsule rupture; SS-iOCT, swept-source intraoperative optical coherence tomography.

Anterior hyaloid membrane (AHM) identification

In Patient 6, who had been diagnosed with an age-related cataract, SS-iOCT enabled the clear visualization of the posterior capsule and the AHM. Following lens removal, the separation between these structures corresponded to Berger’s space, a feature that was not visible under the surgical microscope (Figure 6A,6B). SS-iOCT was applied to explore Berger’s space and AHM anatomy, which typically cannot be visualized intraoperatively.

Figure 6.

Surgical microscopic view (A) and corresponding SS-iOCT image (B) visualizing the posterior capsule and AHM, with SS-iOCT clearly delineating their separation corresponding to Berger’s space. AHM, anterior hyaloid membrane; SS-iOCT, swept-source intraoperative optical coherence tomography.

Discussion

Our case series demonstrated that SS-iOCT substantially expanded the intraoperative field of view, effectively addressing the limitations of conventional surgical microscopes. Surgical microscopes provide a magnified en-face perspective; however, their ability to resolve delicate or subsurface membranous structures is limited. Such membranes are often difficult to visualize en-face, and the limited depth of surgical microscopes hinders simultaneous focus across all relevant planes (11). Conversely, SS-iOCT, which employs a longer-wavelength laser source, provides extended scan depth, a wide field of view (7,10), and high acquisition speed (6,12), enabling comprehensive cross-sectional imaging of the ocular anterior segment from the corneal surface through to the posterior lens capsule (7). In our case series, this enhanced imaging capability also enabled the intraoperative identification of the AHM, a structure that typically cannot be visualized under surgical microscope. The seamless integration of SS-iOCT cross-sectional images directly into the microscope oculars allowed surgeons to maintain uninterrupted focus on the operative field, eliminating the need to refer to an external display. These advantages establish SS-iOCT as a powerful adjunct for surgical visualization, especially of fine membranous structures.

The ability of SS-iOCT to delineate subtle membranous planes was particularly evident in two illustrative cases. In one patient presenting with an intraoperative corneal bulla, a surgical microscope alone was insufficient to determine the exact plane of separation. Conversely, SS-iOCT clearly visualized a separation between the epithelium-Bowman’s layer and the underlying stroma during watertight closure of the corneal incision. This precise information led to the direct modification of the incision closure technique, optimizing surgical management. In another patient, SS-iOCT revealed a fine, superficial hyperreflective layer overlying the anterior capsule, separable from the deeper capsular structure, suggesting the presence of exfoliative material rather than intrinsic capsular splitting. The real-time visualization of this delamination enabled the surgical team to adjust the capsulorhexis approach with greater accuracy, thereby reducing the risk of intraoperative complications. Clinically, the recognition of occult capsular splits is critical, as failure to identify such splits can result in partial capsulorhexis masquerade, predisposing the eye to radial tears or the double-rhexis phenomenon (13-15). In both instances, the utility of the SS-iOCT findings went beyond diagnosis, directly guiding intraoperative decision-making and enhancing procedural safety. Consistent with previous findings, iOCT provided additional or inconsistent information compared with the surgical microscopes in nearly half of the anterior segment procedures (16).

Equally important, SS-iOCT demonstrated clear advantages in situations in which corneal opacity limited direct visualization. In one patient with chronic uveitis and a secondary cataract, dense corneal edema at the incision site obscured a localized DMD that became apparent only on SS-iOCT imaging. This real-time detection prompted the modification of the corneal incision technique, which effectively minimized further detachment and reduced the risk of postoperative corneal decompensation (17-22).

In the broader context of uveitic cataract surgery, anterior segment optical coherence tomography (AS-OCT) has been shown to be valuable in identifying posterior and peripheral anterior synechiae, assessing corneal edema, and detecting capsular abnormalities such as inflammatory membranes or capsular fibrosis—features that may be difficult to detect appreciate under a surgical microscope alone. By revealing these subclinical or obscured anatomical changes, AS-OCT imaging can aid in surgical planning in uveitic eyes by identifying the presence and extent of synechiae, guiding incision placement, and informing strategies for altered capsular support. Thus, consistent with previously reported applications of AS-OCT in uveitis, the present case series underscore its adjunctive role in enhancing intraoperative awareness and procedural safety in complex inflammatory cataracts (23).

In another patient with a traumatic cataract complicated by a central corneal scar, a nearly transparent, curled anterior capsular flap, imperceptible under the surgical microscope, was visualized on SS-iOCT. The identification of this otherwise hidden flap guided adjustments to the capsulorhexis and capsular bag manipulation strategy, thereby preventing extension of the tear and preserving capsular support. These examples underscore how the enhanced penetration capability of SS-iOCT, compared with earlier-generation iOCT, enabled visualization through opaque media, revealing critical subsurface lesions in real time with both accuracy and reliability.

In our series, SS-iOCT also proved indispensable in evaluating posterior capsule integrity. In a patient with a traumatic cataract, PCR was attributable to prior ocular injury. The rupture margins were poorly visible under the conventional surgical microscope. However, SS-iOCT cross-sectional imaging clearly delineated the discontinuity, confirming both the boundaries and the extent of the rupture in real time. Further, SS-iOCT identified associated vitreous prolapse, prompting immediate anterior vitrectomy as part of the intraoperative management. It also provided critical information for determining the intraocular lens (IOL) implantation strategy in the context of compromised capsular support. This capability is particularly clinically relevant in eyes with corneal opacity or edema, during prolonged surgical procedures, or in situations in which the triamcinolone-assisted visualization of vitreous is insufficient or inconclusive. In such scenarios, vitreous prolapse may be subtle or intermittently obscured under the surgical microscope, increasing the risk of delayed recognition and subsequent complications.

By providing the depth-resolved, real-time visualization of vitreous strands, SS-iOCT offers an additional safeguard for the timely detection of vitreous involvement following PCR. The real-time identification of PCR also highlighted a major safety advantage of SS-iOCT. Consistent with previous studies in pediatric and complex cataract cases, iOCT has been shown to detect capsular defects that are otherwise invisible to surgeons, leading to the modification of intraoperative strategies in a significant proportion of procedures (24,25). Compared with earlier-generation iOCT, which often lacked sufficient depth penetration to visualize posterior capsule abnormalities, SS-iOCT enabled the precise delineation of rupture margins and provided a reliable, actionable basis for intraoperative decision-making in our cases.

Finally, SS-iOCT provided unique insights into normal anatomical structures that are typically undetectable under conventional surgical microscope. In one patient with an age-related cataract, following phacoemulsification and prior to IOL implantation, SS-iOCT clearly delineated an intact AHM immediately posterior to the capsule, thereby defining Berger’s space. This structure is generally invisible intraoperatively due to its transparency; however, SS-iOCT enabled the real-time confirmation of its integrity. To the best of our knowledge, this is among the first reports of the intraoperative identification of an intact AHM during cataract surgery using SS-iOCT, highlighting its potential to broaden intraoperative anatomical assessment. The detection of an intact or disrupted AHM is clinically significant, particularly in cases of PCR, as disruptions at the posterior capsule–AHM interface may increase the risk of anterior vitreous prolapse and subsequent vitreoretinal complications (2). Conversely, in eyes with an intact posterior capsule, the intraoperative detection of separation between the AHM and the capsule remains an interesting observation, but further investigation is needed to determine its clinical significance.

SS-iOCT artifacts

SS-iOCT provides high-resolution, depth-resolved intraoperative imaging; however, recognition of potential artifacts and image distortions is essential to avoid misinterpretation, particularly in complex or inflammatory eyes. Mirror artifacts, caused by strong corneal or iris reflections, may obscure angle or iris structures, and mimic pathological findings such as anterior chamber cysts or adhesions. Shadowing artifacts are commonly observed when dense keratic precipitates, synechiae, surgical instruments, or even eyelashes interfere with the OCT beam, limiting the visualization of posterior structures (23).

Additional optical artifacts include saturation artifacts and specular reflections, in which hyperreflective surfaces such as the tear film cause signal oversaturation or glare from the pupillary margin or iris surface that distorts anatomical details. Scatter-related artifacts, including sunray or starburst patterns, may generate radial hyperreflective lines that interfere with tissue signals, while volume scattering from inflammatory debris or nodules can create diffuse hyperreflectivity and complicate structural interpretation (23).

Signal loss and reconstruction errors may also occur due to media opacity (e.g., corneal edema or cataract), suboptimal positioning, blinking, or motion during acquisition. In addition, Y-scan reconstruction from stitched X-scans may misrepresent dynamic anterior segment configurations, particularly during iris movement. These limitations are especially relevant in eyes with compromised optical clarity, such as those with uveitis or corneal edema (23).

Awareness of these artifacts and careful correlation with the surgical context and en-face microscopic view are essential to distinguish true anatomical abnormalities from imaging artifacts. Thus, SS-iOCT should be used as an adjunctive tool, with its findings integrated into surgical microscopic assessment rather than considered in isolation (23).

Limitations

Despite providing valuable insights, this study had several limitations. Its descriptive design, small sample size, and absence of a control group limit the generalizability of the findings. The interpretation of SS-iOCT images remains partly subjective, and instrument-related shadowing can persist despite enhanced tissue penetration. Additionally, the high commercial cost and limited accessibility of SS-iOCT may hinder its broader adoption. Future prospective, randomized studies are essential to determine whether these technological advances result in measurable improvements in surgical outcomes. Further research should also aim to identify the specific clinical scenarios, such as intumescent cataracts, corneal scars, or eyes at heightened risk of PCR, in which patients would derive the greatest benefit from real-time SS-iOCT guidance, thereby optimizing intraoperative decision-making and patient safety.

Conclusions

Together, these cases demonstrate that SS-iOCT represents a significant advancement over conventional iOCT systems, offering full-field improvements such as greater scan depths, expanded imaging ranges, and faster acquisition speeds, enabling real-time visualization that enhances intraoperative assessment and decision-making (26). Notably, image acquisition was successful in all six eyes, corresponding to a feasibility rate of 100%, with feasibility defined as the ability of SS-iOCT to consistently obtain usable images throughout surgery. Moreover, clinically meaningful information was obtained in five of the six cases, yielding a utility rate of 83.3%, with utility defined as the proportion of cases in which SS-iOCT directly influenced the surgical strategy (16). These findings underscore the potential of SS-iOCT to provide actionable guidance in both complex and routine cataract cases. However, it should also be noted that SS-iOCT was adjunctive rather than mandatory in most of the described situations, and its use should be tailored to intraoperative needs.

Supplementary

The article’s supplementary files as

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. This study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Institutional Review Board of the Second Affiliated Hospital, School of Medicine, Zhejiang University (No. IR2024426). Given the retrospective nature of the study and the use of anonymized clinical data, the requirement for written informed consent was waived by the Institutional Review Board.

Data Sharing Statement

Available at https://qims.amegroups.com/article/view/10.21037/qims-2025-aw-2237/dss

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DOI: 10.21037/qims-2025-aw-2237