Anterior segment optical coherence tomography and its clinical applications

Assessment of anterior scleral thickness in Turkish open angle glaucoma patients: an anterior segment optical coherence tomography study

BACKGROUND

To compare anterior scleral thickness (AST) in Turkish patients with open-angle glaucoma (primary open-angle glaucoma (POAG) and pseudoexfoliation glaucoma (PEG)) with healthy controls.

METHODS

This prospective study involved 41 patients with PEG, 69 patients with POAG, and 46 healthy controls. We obtained spectral domain anterior segment optical coherence tomography (AS-OCT) images from the nasal and temporal quadrants and made AST measurements of 1 mm (AST), 2 mm (AST2), 3 mm (AST3), and 4 mm (AST4) posterior to the scleral spur (SS). Schlemm's canal (SC) diameter and area measurements were performed using the ImageJ software. The results were compared statistically.

RESULTS

The average ASTs of the groups did not differ significantly (p > 0.05 for each). The analysis of the nasal SC diameter revealed a significant decrease in the POAG group in comparison with the PEG group, with no difference observed between the POAG and control groups (p = 0.038*). The mean nasal and temporal SC area was significantly smaller in the PEG and POAG groups compared with the control group (p < 0.001** and p < 0.001**, respectively).

CONCLUSIONS

There was no significant difference in nasal and temporal AST between groups; however, the SC area was found to be smaller in glaucoma groups compared with healthy controls. The present findings should be supported by further studies.

The role of anterior segment optical coherence tomography in post-cataract surgery Descemet membrane detachment

This review seeks to evaluate anterior segment optical coherence tomography (AS-OCT) in the diagnostic procedure and management of Descemet's membrane detachment (DMD) in cataract surgery. DMD may present diagnostic challenges, particularly in pronounced corneal edema where traditional methods such as slit lamp biomicroscopy may be inadequate in evaluating the corneal layers. The role of AS-OCT in providing high-resolution images in the preoperative, intraoperative, and postoperative phases of cataract surgery is analyzed with a focus on its role in the early diagnosis of DMD and in evaluating the extent, morphology, and topographic localization of DMD allowing for immediate intervention during surgery and precise pneumodescemetopexy procedures where conservative treatment has failed. This review explores the integration of AS-OCT into the standard perioperative diagnostic workflow, highlighting its potential role in the prevention, accurate diagnosis, and prompt management of DMD, a complication of cataract surgery that, while low in incidence, can be highly disruptive when it occurs. The emerging role of artificial intelligence (AI) in AS-OCT analysis of anterior segment conditions and surgical procedures is discussed, though refinement of AI algorithms is warranted.

In Vivo Quantification of Anterior and Posterior Chamber Volumes in Mice: Implications for Aqueous Humor Dynamics

Purpose

Aqueous humor inflow rate, a key parameter influencing aqueous humor dynamics, is typically measured by fluorophotometry. Analyzing fluorophotometric data depends, inter alia, on the volume of aqueous humor in the anterior chamber but not the posterior chamber. Previous fluorophotometric studies of the aqueous inflow rate in mice have assumed the ratio of anterior:posterior volumes in mice to be similar to those in humans. Our goal was to measure anterior and posterior chamber volumes in mice to facilitate better estimates of aqueous inflow rates.

Methods

We used standard near-infrared (NIR) optical coherence tomography (OCT) and robotic visible-light OCT (vis-OCT) to visualize, reconstruct, and quantify the volumes of the anterior and posterior chambers of the mouse eye in vivo. We used histology and micro-computed tomography (CT) scans to validate relevant landmarks from ex vivo tissues and facilitate in vivo measurement.

Results

Posterior chamber volume is 1.1 times the anterior chamber volume in BALB/cAnNCrl mice, that is, the anterior chamber constitutes about 47% of the total aqueous humor volume, which is very dissimilar to the situation in humans. Anterior chamber volumes in 2-month-old BALB/cAnNCrl and C57BL6/J mice were 1.55 ± 0.36 µL (n = 10) and 2.05 ± 0.25 µL (n = 10), respectively. This implies that previous studies likely overestimated the aqueous inflow rate by approximately twofold.

Conclusions

It is necessary to reassess previously reported estimates of aqueous inflow rates and, thus, aqueous humor dynamics in the mouse. For example, we now estimate that only 0% to 15% of aqueous humor drains via the pressure-independent (unconventional) route, similar to that seen in humans and monkeys.

Multimodal corneal imaging before refractive cataract surgery

PURPOSE OF REVIEW

To prospectively review the advances in diagnostics for refractive cataract surgery, focusing on multimodal corneal analysis.

RECENT FINDINGS

The article explores the considerations related to planning refractive cataract surgery, emphasizing its potential to enhance patients' vision performance and quality of life. This review explores preoperative analysis in cataract surgery, focusing on assessing the cornea and ocular surface using multimodal diagnostics, including Placido disk-based corneal topography, Scheimpflug tomography OCT (optical coherence tomography), and biomechanical assessment. Wavefront technology, gene therapy, and artificial intelligence are also relevant in enhancing surgical precision and outcomes. It highlights the importance of preoperative thorough evaluations and technological advancements in ophthalmology.

SUMMARY

The rapid evolution and advancement of technology enable excellent refractive outcomes in most cases following cataract surgery. Consideration of appropriate preoperative factors is essential for achieving the desired postoperative outcome.

Role of Anterior Segment Optical Coherence Tomography in Staging and Evaluation of Treatment Response in Infectious Keratitis

PURPOSE

The aim of this study was to evaluate the role of anterior segment optical coherence tomography during follow-up of infectious keratitis and to assess response to treatment.

METHODS

This was a prospective, consecutive, observational clinical series of cases. Twenty-three eyes of 23 patients with clinically proven fungal keratitis were included in the study. The patients received medical treatment according to clinical diagnosis, and follow-up was performed weekly. Slit-lamp examination and photography, and anterior segment optical coherence tomography were performed at initial and follow-up visits until corneal healing occurred. The main outcome measures included infiltrate depth, width, and density; central corneal thickness; minimal corneal thickness; corneal thickness at the site of the lesion; and stromal thickness at the center of the lesion.

RESULTS

Twenty-three eyes of 23 patients (17 men and 6 women), mean age 42.5 ± 19 (8-66) years, were clinically diagnosed with fungal keratitis. Localization was central in 14 cases and paracentral/peripheral in 9 cases. Healing time was 6 to 12 weeks. Minimal corneal thickness, corneal thickness at the site of lesion, and stromal thickness at the center of lesion, and also infiltrate width and depth changed significantly from the first visit to the healing stage at the last follow-up (0.009, 0.001, 0.007, 0.001, and <0.001, respectively).

CONCLUSIONS

In cases of fungal keratitis, anterior segment optical coherence tomography can provide the clinician with a quantitative assessment of a number of corneal parameters that can be used to determine effectiveness of therapy and confirm complete healing of the lesions that cannot be achieved by clinical evaluation.

In vivo quantification of anterior and posterior chamber volumes in mice: implications for aqueous humor dynamics

Purpose

Aqueous humor inflow rate, a key parameter influencing aqueous humor dynamics, is typically measured by fluorophotometery. Analyzing fluorophotometric data depends, inter alia, on the volume of aqueous humor in the anterior, but not the posterior, chamber. Previous fluorophotometric studies of aqueous inflow rate in mice have assumed the ratio of anterior:posterior volumes in mice to be similar to those in humans. Our goal was to measure anterior and posterior chamber volumes in mice to facilitate better estimates of aqueous inflow rates.

Methods

We used standard near-infrared optical coherence tomography (OCT) and robotic visible-light OCT (vis-OCT) to visualize, reconstruct and quantify the volumes of the anterior and posterior chambers of the mouse eye in vivo. We used histology and micro-CT scans to validate relevant landmarks from ex vivo tissues to facilitate in vivo measurement.

Results

Posterior chamber volume is 1.1 times the anterior chamber volume in BALB/cAnNCrl mice, i.e. the anterior chamber constitutes about 47% of the total aqueous humor volume, which is very dissimilar to the situation in humans. Anterior chamber volumes in 2-month-old BALB/cAnNCrl and 7-month-old C57BL6/J mice were 1.55 ± 0.36 μL (n=10) and 2.41 ± 0.29 μL (n=8), respectively. This implies that previous studies likely over-estimated aqueous inflow rate by approximately two-fold.

Conclusions

It is necessary to reassess previously reported estimates of aqueous inflow rates, and thus aqueous humor dynamics in the mouse. For example, we now estimate that only 0-15% of aqueous humor drains via the pressure-independent (unconventional) route, similar to that seen in humans and monkeys.

Assessment of Schlemm's canal with swept-source optical coherence tomography in Graves' ophthalmopathy

PURPOSE

To evaluate the Schlemm's canal (SC) parameters obtained by swept-source optical coherence tomography (OCT) different in Graves' ophthalmopathy (GO) eyes compared to healthy eyes.

METHODS

This cross-sectional observational study evaluated 64 eyes of 32 GO cases and 56 eyes of 28 healthy controls. The study was conducted between October 2020 and June 2021. SC images were obtained from the temporal limbus of individuals using swept-source OCT. SC length (SCL) and SC area (SCA) were measured. The relationship between SC parameters in the patient group and intraocular pressure (IOP), retinal nerve fiber layer (RNFL) thickness, Graves' disease (GD) duration, and clinical activity score (CAS) was evaluated.

RESULTS

In the GO group, 64 eyes of 32 patients were evaluated, and in the age and gender-matched healthy control group, 56 eyes of 28 individuals were assessed. SC images from 4 eyes of 4 patients in the patient group and 1 eye of 1 patient in the control group were not clear, preventing SCL and SCA measurements for these eyes. SCL and SCA measurements were found to be lower, and IOP and Hertel values were higher in the GO group compared to the healthy controls. However, no significant correlation was observed between SCL and SCA with IOP, RNFL thickness, GD duration, GO duration, or CAS in the GO group. In the GO group, the mean value of SCA was found to be higher in eyes with glaucoma or OHT compared to those without.

CONCLUSION

These findings indicate that SC in GO-affected eyes is shorter and has a smaller area than in healthy individuals. Additionally, higher IOP and Hertel values were observed in the GO group compared to healthy controls. This study suggests that assessing SC using anterior segment OCT could provide valuable insights into the regulation of IOP and the development of glaucoma in GO-affected eyes.

Biometry-Based Technique for Determining the Anterior Scleral Thickness: Validation Using Optical Coherence Tomography Landmarks

Purpose

Considering the potential role of anterior scleral thickness (AST) in myopia and the ubiquitous use of optical biometers, we applied and validated a biometry-based technique for estimating AST using optical coherence tomography (OCT) landmarks.

Methods

The AST was determined across four meridians in 62 participants (aged 20-37 years) with a swept-source OCT and a noncontact optical biometer at a mean ± SD distance of 3.13 ± 0.88 mm from the limbus. The biometer's graticule was focused and aligned with the anterior scleral reflex, which led to the generation of four prominent A-scan peaks: P1 (anterior bulbar conjunctiva), P2 (anterior episclera), P3 (anterior margin of anterior sclera), and P4 (posterior margin of anterior sclera), which were analyzed and compared with the corresponding OCT landmarks to determine tissue thickness.

Results

The AST measurements between biometer and OCT correlated for all meridians (r ≥ 0.70, overall r = 0.82; coefficient of variation [CV], 9%-12%; P < 0.01). The mean difference ± SD between two instruments for overall AST measures was 3 ± 2.8 µm (range, -18 to +16 µm; lower limits of agreement, -89 to +83 µm; P = 0.23) across all meridians. The mean ± SE AST with both instruments was found to be thickest at the inferior (562 ± 7 µm and 578 ± 7 µm) and thinnest at the superior (451 ± 7 µm and 433 ± 6 µm) meridian. The biometer demonstrated good intrasession (CV, 8.4%-9.6%) and intersession (CV, 7.9%-13.3%) repeatability for AST measurements across all meridians.

Conclusions

The noncontact optical biometer, which is typically used to determine axial length, is capable of accurately estimating AST based on OCT landmarks.

Translational Relevance

The high-resolution optical biometers can demonstrate wider application in the field of myopia research and practice to determine AST.

Imaging of the lower punctum with anterior segment OCT in patients with dacryocystorhinostomy who underwent bicanalicular silicone tube implantation

Spectral domain OCT imaging of the lower punctum in cases with silicone tube implantation OBJECTIVE: To record the structural changes in the lower punctum by performing spectral domain anterior segment OCT imaging of dacryocystorhinostomy cases who underwent bicanalicular silicone tube implantation.

METHODS

Thirty eyes of 30 patients who underwent bicanalicular Crawford silicone tube implantation with dacryocystorhinostomy were included in the study. The mean age of the cases was 53 ± 13.96 (24-72). Of the cases, 19 were female and 11 were male, 18 of them were operated on the right eye and 12 on the left eye. The lower punctum images of the cases were recorded with spectral domain anterior segment OCT preoperatively and at the 1st day, 1st month and 6th month after explantation of the silicone tube. In the lower punctum, external punctal width(EPW) and canaliculi depth (CD) were measured.

RESULTS

The mean EPW and CD measurements of the cases in the preoperative period, respectively; 544.90±144.11 µm and 451.70±197.45 µm. First day after silicone tube explantation, EPW was 818.00±186.83 µm and CD was 735.35±337.15 µm, at 1st month EPW was 665.95±142.12 µm and CD was 619.30±212.11 µm and at 6th months EPW was 530±150.29 µm and CD was 558.45±254.37 µm, respectively. Mean EPW values were found to be higher on the first day after extubation than before surgery (p = 0.001). There was no significant difference in the mean EPW values at the first and sixth months after extubation compared to pre-implantation (p>0.05). The mean CD values were higher at the 1st day, 1st month and 6th month after tube explantation than preoperative CD values, they were not statistically significant.

CONCLUSIONS

According to the lower punctum OCT imaging data, silicone tube implantations applied to the canalicular system do not create a structurally significant difference in the lower punctum. The punctal opening gradually decreases after extubation. The decrease in EPW values is more pronounced than the decrease in CD values. Silicone tube implantation was more effective in maintaining canaliculi depth compared to external punctal diameter.

Anterior and posterior imaging with hyperparallel OCT

Hyperparallel OCT (HP-OCT) is a parallel spectral domain imaging technology particularly well-suited to the anterior segment. It uses a 2-dimensional grid of 1008 beams to simultaneously image across a wide area of the eye. In this paper we demonstrate that sparsely sampled volumes captured at 300 Hz can be registered without the need for active eye tracking to produce 3-dimensional (3D) volumes free from motion artefacts. The anterior volume provides complete 3D biometric information, including lens position, curvature, epithelial thickness, tilt, and axial length. We further demonstrate that, with the change of a detachable lens, we can capture high resolution anterior volumes and importantly, posterior volume images for preoperative assessment of the posterior segment. Advantageously, the retinal volumes have the same 11.2 mm Nyquist range as the anterior imaging mode.

Scleral thickness in normal Indian eyes measured using spectral domain anterior segment optical coherence tomography

Purpose

To establish normative data on anterior scleral thickness using the spectral domain anterior segment optical coherence tomography (AS-OCT).

Methods

In total, 200 eyes of 100 healthy subjects underwent AS-OCT scans in the temporal and nasal quadrants. The scleral + conjunctival complex thickness (SCT) was measured by a single examiner. Mean SCT was analyzed for differences across age groups, gender, and location (nasal versus temporal).

Results

Mean age was 46.4 ± 18.3 (21-84) years; male to female ratio was 54:46. Mean SCT (nasal + temporal) of the right eye (RE) was 682.3 ± 64.2 μm in males and 660.6 ± 57.1 μm in females. In the left eye (LE), it was 684.6 ± 64.9 μm in males and 661.8 ± 49.3 μm in females. These differences between male and female for both eyes were statistically significant (P = 0.006 and P = 0.002). The mean SCT of temporal and nasal quadrants in the RE was 678.54 ± 57.50 and 666 ± 66.2 μm, respectively. In the LE, the temporal mean SCT quadrant was 679.6 ± 55.8 μm, and the nasal was 668.6 ± 63.6 μm. Age had a negative correlation with SCT (-0.62 μm/year; P = 0.03), and males had a higher temporal SCT than females (22 μm higher; P = 0.03). After adjusting for age and gender in a multivariate analysis, temporal SCT was significantly (P < 0.001) higher than nasal SCT.

Conclusion

In our study, mean SCT decreased with age and males had a higher temporal SCT. This is the first study to evaluate scleral thickness in the Indian population, and the data can be used as a baseline for comparing variations in scleral thickness in disease.

Anterior segment parameters on optical coherence tomography in healthy South Asian children

PURPOSE

High resolution spectral domain optical coherence tomography (SD-OCT) was used to assess the anterior segment structure parameters in healthy South Asian children.

METHODS

108 eyes of 54 healthy children ≤ 16 years were recruited after a thorough eye exam. The anterior segment analysis was be done by Optopol Revo 80 high resolution SD-OCT. Central corneal thickness (CCT), Angle opening distance (AOD), Anterior chamber (AC) angle, Trabecular iris space area (TISA), Trabecular iris angle (TIA), iris thickness at 2 mm, internal AC diameter and lens vault were evaluated.

RESULTS

Mean age was 11.38 years. Mean IOP was 13.63 mmHg, mean axial length, 22.82 mm, mean spherical equivalent, -0.14 D, mean CCT, 532.6 µm and mean CDR was 0.31. The mean internal AC diameter was 11609.15 µm. The nasal and temporal AC angles was 53.54° and 50.37°, respectively [P = .033]. The nasal and temporal AOD500 were 0.9 mm and 0.85 mm, respectively [P = .629]. The nasal and temporal AOD750 were 1.21 mm and 1.06 mm, respectively [P = .583]. The nasal TIA was 41.75°; the temporal TIA; 40.24° [P = .325]. The nasal TISA500 was 0.33 mm²; the temporal TISA500, 0.31 mm² [P = .012]. The nasal TISA750 was 0. 59 mm²; the temporal TISA750, 0.56 mm² [P = .746]. The nasal iris thickness at 2 mm was 483.54 µm; the temporal iris thickness, 505.8 µm [P = .273]. The mean lens vault was -519.58 µm.

CONCLUSIONS

Our study data depicts the normal anterior segment parameters in healthy Pakistani children.

Clinical Observation of Corneal Endothelial Plaques With Fungal and Bacterial Keratitis by Anterior Segment Optical Coherence Tomography and In Vivo Confocal Microscopy

PURPOSE

Endothelial plaque is an important sign of fungal keratitis and is related to diagnosis, surgical indications, and prognosis. However, bacterial keratitis sometimes involves fibrin formation on the back corneal surface, similar to endothelial plaques. Because corneal infiltration interferes with precise observation of the posterior corneal plaque, distinguishing pathogens with a slitlamp is difficult. We hope to assist clinicians in early diagnosis and timely treatment by observing the connection state of endothelial plaques and the corneal endothelium through anterior segment optical coherence tomography (AS-OCT) and the different forms of endothelial plaques in infectious keratopathy through in vivo confocal microscopy (IVCM).

METHODS

We analyzed 52 patients in the Eye Hospital of the First Affiliated Hospital of Harbin Medical University who were clearly diagnosed with fungal or bacterial keratitis with endothelial plaques. All patients underwent AS-OCT and IVCM on admission.

RESULTS

According to the smear, IVCM, or fungal and bacterial culture results, the patients were diagnosed with fungal (28 patients) or bacterial keratitis (24 patients). AS-OCT in 25 patients diagnosed with fungal keratitis revealed that the corneal endothelium-endothelial plaque boundary was unclear and wavy, and 24 patients had unclear cell boundaries and a large number of compactly distributed inflammatory cells in the endothelial layer according to IVCM. AS-OCT in 23 patients diagnosed with bacterial keratitis revealed clear corneal endothelium-endothelial plaque boundaries, and insufficient endothelial cell boundaries with a large number of visible and scattered inflammatory cell structures were observed through IVCM in 22 patients.

CONCLUSIONS

Corneal endothelial plaque detection by AS-OCT and IVCM can be used for early diagnosis of infectious keratitis.

Measuring Human Corneal Stromal Biomechanical Properties Using Tensile Testing Combined With Optical Coherence Tomography

Purpose: To investigate the ex vivo elastic modulus of human corneal stroma using tensile testing with optical coherence tomography (OCT) imaging and its correlation with in vivo measurements using corneal visualization Scheimpflug technology.

Methods: Twenty-four corneal specimens extracted from stromal lenticules through small incision lenticule extraction were cut into strips for uniaxial tensile tests. In vivo corneal biomechanical responses were evaluated preoperatively using the corneal visualization Scheimpflug technology (CorVis ST). The correlation of the elastic modulus with clinical characteristics and dynamic corneal response parameters were analyzed using Spearman’s correlation analysis.

Results: The mean low strain tangent modulus (LSTM) of the human corneal stroma was 0.204 ± 0.189 (range 0.010–0.641) MPa, and high strain tangent modulus (HSTM) 5.114 ± 1.958 (range 2.755–9.976) MPa. Both LSTM (r = 0.447, p = 0.029) and HSTM (r = 0.557, p = 0.005) were positively correlated with the stress-strain index (SSI). LSTM was also positively correlated with the A1 deflection length (r = 0.427, p = 0.037) and A1 deflection area (r = 0.441, p = 0.031). HSTM was positively correlated with spherical equivalent (r = 0.425, p = 0.038).

Conclusions: The correlation of corneal elastic modulus with A1 deflection parameters and SSI may indicate a relationship between these parameters and tissue elasticity. The HSTM decreased with the degree of myopia. Combining tensile test with OCT may be a promising approach to assess corneal biomechanical properties.

Investigation of the Sectorized Corneal Thickness of Eyes With Corneal Endothelial Dysfunction Using Anterior-Segment Optical Coherence Tomography

PURPOSE

The aim of this study was to investigate the sectorized corneal thickness of eyes with corneal endothelial dysfunction using anterior-segment optical coherence tomography.

METHODS

We retrospectively collected anterior-segment optical coherence tomography data conducted before endothelial keratoplasty on 53 eyes of 53 patients with corneal endothelial dysfunctions including Fuchs endothelial corneal dystrophy, bullous keratopathy (BK) after trabeculectomy, and BK after laser iridotomy and from 18 normal eyes of 18 subjects. The imaging points were divided into 17 sectors. The mean for each sector was calculated and compared with the corresponding superior/inferior and temporal/nasal sectors.

RESULTS

In the normal eyes, the superior sectors were thicker than the inferior and the temporal sectors thinner than the nasal. In the diseased eyes, the superior sectors were thicker than the inferior in all subgroups; however, this tendency was no longer observed after the values were divided by the mean for the normal eyes. No significant differences were found on horizontal comparisons; however, after the values were divided by the mean for the normal eyes, the temporal sectors were thicker than the nasal. When comparing the values between the with-hole and the without-hole sides in the BK after laser iridotomy eyes, the sectors on the with-hole side were thicker than the other side.

CONCLUSIONS

Corneal thickness of endothelial dysfunction was thicker in the superior sectors than the inferior but at a similar level to normal eyes. No significant differences were found for horizontal comparisons but, based on comparison with the normal eyes, the temporal sectors were thicker than the nasal.

The clinical features and the factors affecting visual prognosis in pediatric open-globe ınjuries

PURPOSE

To investigate clinical features and factors affecting visual prognosis after pediatric open-globe injuries.

METHODS

Retrospective study of 223 children with open-globe injury was conducted. Children with final logMAR visual acuity (LVA) > 0.70 were determined as poor-vision group (group 1, n = 108) and those with final LVA ≤ 0.70 as good-vision group (group 2, n = 115). Demographic characteristics (age, gender, and damaged eye), time between trauma and surgery, ocular trauma score (OTS), follow-up time, injury size, initial and final visual acuity levels, injury type (penetrating injury, globe rupture, perforating injury, and intraocular foreign body injury), injury localization (zone 1 = within the corneal and/or limbal area, zone 2 = within the scleral area extending 5 mm back from the limbus, and zone 3 = within the area posterior to zone 2), injury cause [metal objects (fork, knife, needle), broken glass, blunt objects (ball, punch), pen-pencil, and unidentified objects], and accompanying ocular findings of the groups were detected, and comparisons were done. Additionally, effects of age, time between trauma and surgery, OTS, injury size, follow-up time, initial LVA, injury type, and injury zone on final LVA were analyzed in both groups.

RESULTS

Mean age was 9.1 ± 2.0 years. There were 151 males and 72 females. Compared to group 1, group 2 had better initial and final visions (1.21 ± 0.26 vs 0.60 ± 0.28, p < 0.001 for initial LVA; 1.00 ± 0.32 vs 0.30 ± 0.13, p < 0.001 for final LVA), greater OTS (1.72 ± 0.53 vs 3.73 ± 0.61, p = 0.025), and smaller injury size (10.4 ± 3.5 vs 5.8 ± 2.4 mm, p = 0.002). Globe rupture (p = 0.015) and relative afferent pupillary defect (RAPD) (p = 0.037) were higher in group 1, while penetrating injury (p = 0.044), zone 1 involvement (p = 0.038), and metal object injury (p = 0.041) were higher in group 2. Based on multivariate analysis, the presences of globe rupture (p = 0.024) and RAPD (p = 0.035), the involvement without zone 1 (p = 0.042), and the injury without metal object (fork, knife, needle) (p = 0.046) were associated with poor final vision. Final LVA (for group 1 and group 2) was negatively correlated with OTS (r =  - 0.398, p = 0.037; r =  - 0.369, p = 0.040), while positively correlated with injury size (r = 0.412, p = 0.031; r = 0.318, p = 0.046) and initial LVA (r = 0.335, p = 0.043; r = 0.402, p = 0.034).

CONCLUSION

In our study, poor prognostic factors affecting final vision were low OTS, poor initial vision, the presences of globe rupture and RAPD, the large injury size, the involvement without zone 1, and the injury without metal object (fork, knife, needle).

Current research and future prospects of IVOCT imaging-based detection of the vascular lumen and vulnerable plaque

Intravascular optical coherence tomography (IVOCT) is an imaging method that has developed rapidly in recent years and is useful in coronary atherosclerosis diagnosis. It is widely used in the assessment of vulnerable plaque. This review summarizes the main research methods used in recent years for blood vessel lumen boundary detection and segmentation and vulnerable plaque segmentation and classification. This article aims to comprehensively and systematically introduce the research progress on internal tissues of blood vessels based on IVOCT images. The characteristics and advantages of various methods have been summarized to provide theoretical ideas and methods for the reference of relevant researchers and scholars.

Correlation Between Degree of Lens Opacity and the Phacoemulsification Energy Parameters Using Different Imaging Methods in Age-Related Cataract

Purpose

To compare the correlation between degree of lens opacity and the phacoemulsification energy parameter in patients with age-related cataract as determined by slit lamp, 25-MHz ultrasound biomicroscopy (UBM), and Scheimpflug imaging (Pentacam) and to evaluate the application of these three methods to measuring lens opacification.

Methods

This observational study was conducted in 319 patients (381 eyes) with different types of age-related cataract. The average age of patients was 67.3 ± 11.4 years. The degree of lens opacity acquired by slit lamp, 25-MHz UBM, and Pentacam was determined by the Lens Opacity Classification System III (LOCSIII), pixel units calculated by ImageJ, and lens density, respectively. We primarily analyzed and compared the correlation between lens opacity and the cumulative dissipated energy (CDE) values of phacoemulsification.

Results

Cortical, nuclear, and posterior subcapsular (PSC) cataracts were evaluated as follows: LOCSIII grades 3.31 ± 1.42, 3.29 ± 1.49, and 0.91 ± 0.83; pixel units 120.91 ± 22.8, 93.2 ± 15.9, and 99.7 ± 13.0; and lens density 51.8 ± 31.2, 21.2 ± 6.10, and 53.3 ± 35.3, respectively. The CDE values were 12.1 ± 12.4, 13.5 ± 9.11, and 3.93 ± 1.96. In cortical cataract, there was a linear correlation among LOCSIII, pixel units, and CDE value (r = 0.560, r = 0.832, and r = 0.582, respectively; both P < 0.05), but lens density had no correlation with other parameters. In nuclear cataract, there was a linear correlation among LOCSIII, lens density, and CDE value (r = 0.747, r = 0.865, and r = 0.906, respectively; both P < 0.05), but pixel units had no correlation with other parameters. In PSC, only pixel units and LOCSIII showed a correlation.

Conclusions

The various imaging methods offered different advantages in terms of determining lens opacity, a feature related to types of age-related cataracts. Choosing the most suitable imaging method to evaluate lens opacification based on the type of age-related cataract is important for accurately predicting the phacoemulsification parameters for cataract surgery.

Translational Relevance

Determining the appropriate phacoemulsification strategy depends on quantitative analysis of the degree of lens opacity to reduce intraoperative and postoperative complications and to obtain the optimal postoperative visual outcome.

Towards a Connected Mobile Cataract Screening System: A Future Approach

Advances in computing and AI technology have promoted the development of connected health systems, indirectly influencing approaches to cataract treatment. In addition, thanks to the development of methods for cataract detection and grading using different imaging modalities, ophthalmologists can make diagnoses with significant objectivity. This paper aims to review the development and limitations of published methods for cataract detection and grading using different imaging modalities. Over the years, the proposed methods have shown significant improvement and reasonable effort towards automated cataract detection and grading systems that utilise various imaging modalities, such as optical coherence tomography (OCT), fundus, and slit-lamp images. However, more robust and fully automated cataract detection and grading systems are still needed. In addition, imaging modalities such as fundus, slit-lamps, and OCT images require medical equipment that is expensive and not portable. Therefore, the use of digital images from a smartphone as the future of cataract screening tools could be a practical and helpful solution for ophthalmologists, especially in rural areas with limited healthcare facilities.

Swept Source Optical Coherence Tomography Analysis of a Selected Eye's Anterior Segment Parameters in Patients with Pseudoexfoliation Syndrome

Background: Pseudoexfoliation syndrome (PEX) is a systemic, age-related disorder characterized by the production and accumulation of pseudoexfoliation material. To date, detailed characteristics have not been published regarding the iridocorneal angle and cornea in patients with pseudoexfoliation syndrome determined through swept source optical coherence tomography (SS-OCT). Methods: A total of 150 eyes of patients with pseudoexfoliation syndrome (ages 69–86 years) and 166 eyes in a control group (ages 54–79 years) were analyzed. Results: The central corneal thickness in the PEX group was 549.56 μm and was slightly (insignificantly) higher than that of the control group (540.56 µm). The anterior chamber of the eye was visibly shallower in patients with PEX syndrome than in those of the control group (2.49 mm vs. 3.07 mm; p < 0.001). The Fourier analysis parameters of the cornea showed multiple differences between the PEX and control groups. With respect to iris area, the parameters showed statistically significant differences between the PEX and control groups in all four quadrants of the eye. No statistical significance was found in the PEX group for the iridocorneal angle parameters, or corneal and lens parameters depending on gender and age. Conclusions: PEX syndrome is characterized by a significant impact on the anterior eye segment, including higher anterior and posterior keratometric values, lower anterior chamber depth, higher iris thickness, and narrower angle parameters. The characteristic anterior eye segment features of PEX syndrome can be detected using SS-OCT, which could potentially assist clinicians in properly managing the disease.

Paradox of complex diversity: Challenges in the diagnosis and management of bacterial keratitis

Bacterial keratitis continues to be one of the leading causes of corneal blindness in the developed as well as the developing world, despite swift progress since the dawn of the "anti-biotic era". Although, we are expeditiously developing our understanding about the different causative organisms and associated pathology leading to keratitis, extensive gaps in knowledge continue to dampen the efforts for early and accurate diagnosis, and management in these patients, resulting in poor clinical outcomes. The ability of the causative bacteria to subdue the therapeutic challenge stems from their large genome encoding complex regulatory networks, variety of unique virulence factors, and rapid secretion of tissue damaging proteases and toxins. In this review article, we have provided an overview of the established classical diagnostic techniques and therapeutics for keratitis caused by various bacteria. We have extensively reported our recent in-roads through novel tools for accurate diagnosis of mono- and poly-bacterial corneal infections. Furthermore, we outlined the recent progress by our group and others in understanding the sub-cellular genomic changes that lead to antibiotic resistance in these organisms. Finally, we discussed in detail, the novel therapies and drug delivery systems in development for the efficacious management of bacterial keratitis.

Corneal pachymetry by AS-OCT after Descemet's membrane endothelial keratoplasty

Corneal thickness (pachymetry) maps can be used to monitor restoration of corneal endothelial function, for example after Descemet’s membrane endothelial keratoplasty (DMEK). Automated delineation of the corneal interfaces in anterior segment optical coherence tomography (AS-OCT) can be challenging for corneas that are irregularly shaped due to pathology, or as a consequence of surgery, leading to incorrect thickness measurements. In this research, deep learning is used to automatically delineate the corneal interfaces and measure corneal thickness with high accuracy in post-DMEK AS-OCT B-scans. Three different deep learning strategies were developed based on 960 B-scans from 50 patients. On an independent test set of 320 B-scans, corneal thickness could be measured with an error of 13.98 to 15.50 μm for the central 9 mm range, which is less than 3% of the average corneal thickness. The accurate thickness measurements were used to construct detailed pachymetry maps. Moreover, follow-up scans could be registered based on anatomical landmarks to obtain differential pachymetry maps. These maps may enable a more comprehensive understanding of the restoration of the endothelial function after DMEK, where thickness often varies throughout different regions of the cornea, and subsequently contribute to a standardized postoperative regime.

The Value of Anterior Segment Optical Coherence Tomography in Different Types of Corneal Infections: An Update

Anterior segment optical coherence tomography (AS-OCT) is a modality that uses low-coherence interferometry to visualize and assess anterior segment ocular features, offering several advantages of being a sterile and noncontact modality that generates high-resolution cross-sectional images of the tissues. The qualitative and quantitative information provided by AS-OCT may be extremely useful for the clinician in the assessment of a wide spectrum of corneal infections, guiding in the management and follow-up of these patients. In clinical practice, infections are routinely evaluated with slit-lamp biomicroscopy, an examination and imaging modality that is limited by the physical characteristics of light. As a consequence, the depth of pathology and the eventually associated corneal edema cannot be accurately measured with the slit-lamp. Therefore, it represents a limit for the clinician, as in vivo information about corneal diseases and the response to treatment is limited. Resolution of corneal infection is characterized by an early reduction in corneal edema, followed by a later reduction in infiltration: both parameters can be routinely measured with standardized serial images by AS-OCT.

Anterior scleral thickness dimensions by swept-source optical coherence tomography

Clinical relevance: Given the association of scleral characteristics with many ophthalmological diseases, there is an important need to measure the anterior scleral thickness (AST).Background: This study examined the AST by swept-source optical coherence tomography (SS-OCT) in a large healthy population, assessing also the reproducibility of AST measurements and the correlation with different parameters.Methods: Cross-sectional study in 605 eyes of 605 subjects. AST measurements were made in the temporal and nasal quadrants at 1 (AST1) and 3 mm (AST3) from the scleral spur using SS-OCT. These dimensions were then assessed for associations in a multivariate model with the factors age, sex, refractive error, conjunctival-Tenon capsule thickness (CTT), anterior chamber angle (ACA), intraocular pressure (IOP), iris thickness (IT), limbus-sulcus distance (LSD), and ciliary muscle thickness (CMT). The reproducibility of the AST measurements was determined in 30 of the participants.Results: The mean age was 42.6 ± 17.3 years (range 5 to 86 years). The following means were recorded: AST1 was 522.3 ± 65.7 µm (355 to 761) and 558.4 ± 71.5 µm (357 to 889); AST2 was 513.3 ± 67.3 µm (343 to 732) and 574.4 ± 71.6 µm (389 to 789), and AST3 548.8 ± 71.9 µm (356 to 762) and 590.1 ± 76.6 µm (414 to 873) in the temporal and nasal quadrants respectively, being thicker the nasal quadrant (all p < 0.001). A positive correlation was detected between AST and age, sex, temporal ACA and LSD (all p ≤ 0.043), being negative the correlation with CMT (p ≤ 0.044). No correlation was observed between AST measurements and refractive error, CTT and IT (p ≥ 0.064). The reproducibility of AST measurements was excellent (intraclass correlation coefficient ≥0.951).Conclusions: SS-OCT allows for in vivo AST measurements. Our data contained a wide range of measurements, showing an association between AST and age, sex, ACA, LSD and CMT.

Optical coherence tomography and the proximal lacrimal drainage system: a major review

PURPOSE

To provide a major review of the literature on diagnostic and therapeutic implications, techniques, and utility of anterior segment optical coherence tomography (OCT) for the proximal lacrimal drainage system (PLDS).

METHODS

The authors performed a PubMed search of articles published in the English language on anterior segment OCT for the proximal lacrimal drainage system. Data captured include evolution, techniques, diagnostic utility, therapeutic monitoring, outcomes, and limitations. Specific emphasis was laid on addressing the existing lacunae and the current practice patterns.

RESULTS

The PLDS parameters that can be studied by OCT include punctal shape and morphology, external and internal punctum diameters, punctum depth and area, intra-punctal tear meniscus, punctal reserve, punctum-canalicular junction, canalicular diameter at various depths, canalicular depth, canalicular cross-sectional area, canalicular volume, and fluid meniscus characteristics. Normative data is now available from across the globe. Several punctal and canalicular disorders show characteristic OCT features and have adjunctive value in diagnosis. Post-operative OCT imaging can help in monitoring the outcomes of selected surgical procedures and medical therapy. OCT studies have raised doubts about the previous beliefs of vertical canalicular height and the definition of punctal stenosis. OCT dacryography (OCTD) and 3-dimensional punctal and canalicular imaging are promising modalities to further explore the anatomy, physiology, and pathophysiology of the PLDS.

CONCLUSION

Optical coherence tomography techniques are increasingly playing a significant role in diagnosing and managing proximal lacrimal drainage disorders. Further improvements in imaging techniques, better resolution, standardized definitions, and measurements of punctal and canalicular parameters will expand its clinical usage and give impetus to minimally invasive lacrimal surgeries.

Efficacy of Swept-source Optical Coherence Tomography in Axial Length Measurement for Advanced Cataract Patients

SIGNIFICANCE

A major limitation of standard time-domain optical coherence tomography-based biometers (TD-OCT) is an inability to measure the axial length (AL) in advanced cataract. A new device that uses swept-source optical coherence tomography (SS-OCT) allows better light penetration. Hence, a considerable number of cataract patients who failed AL measurement by TD-OCT can be recovered by SS-OCT.

PURPOSE

The purposes of this study were to evaluate the efficacy of an SS-OCT for AL measurement in advanced cataract patients and to identify characteristics of lens opacity that impede the AL measurement.

METHODS

Advanced cataract patients who were unable to obtain AL measurement using a standard TD-OCT-based optical biometer (IOLMaster500; Carl Zeiss Meditec, Jena, Germany) were recruited in this study. The AL was remeasured using SS-OCT (IOLMaster700), followed by measurement with immersion ultrasonography (IU). The percentage of patients who achieved AL measurement by SS-OCT was recorded. The AL obtained from SS-OCT was then verified by comparing with the AL derived from IU. The cataract type of each patient was classified according to standard Lens Opacity Classification III score. The association between characteristics of cataract and successful AL measurement by SS-OCT was analyzed.

RESULTS

Sixty-four eyes that failed AL measurement from TD-OCT were included. Fifty-six eyes (87.5%) were able to be measured by SS-OCT (95% confidence interval, 77.23 to 93.53%). The AL obtained by SS-OCT showed very high agreement with those derived from IU (intraclass correlation coefficient, 0.99). There was no statistically significant correlation between characteristics of lens opacity and the capability of SS-OCT for AL measurement (P > .05). However, there was a trend toward an inability to measure the AL in cataracts with a high grade of lens opacity.

CONCLUSIONS

The efficacy of SS-OCT-based optical biometer was excellent. Of the patients with advanced cataract who failed the AL measurement by TD-OCT, 87.5% could be recovered by SS-OCT. However, there was no specific type of lens opacity associated with a failure of AL measurement using SS-OCT.

Swept Source Optical Coherence Tomography Analysis of the Selected Eye's Anterior Segment Parameters

BACKGROUND

The present study determined the mean reference values of the anterior segment parameters of the selected eye using swept source optical coherence tomography (SS-OCT) in healthy Caucasian participants.

METHODS

A total of 166 volunteers (age 54-79 years), women (n = 92) and men (n = 74), were analyzed. One eye of each subject was randomly selected for anterior segment imaging. The anterior segment of the eye was scanned with CASIA2. The analyzed anterior segment parameters were divided into three groups, namely parameters of the cornea, lens, and angle.

RESULTS

The OCT (e.g., Ks, Kf, pKf, pKs, and central corneal thickness) and Fourier parameters of the cornea were significantly different between females and males. The iridocorneal angle was the smallest in the upper quadrant for all distance from the apex of the angle (250, 500, and 750 µm).

CONCLUSIONS

Therefore, SS-OCT enables the analysis of parameters of the cornea, anterior chamber, lens, and iridocorneal angle, highlighting its clinical utility. Sex-specific differences in the analyzed parameters should be taken into account during the diagnosis of corneal diseases. The configuration of the filtration angle is an important marker during glaucoma diagnosis and drainage implant surgery. Measurements with CASIA 2is characterized by very good repeatability.

Comparison of Femtosecond Laser-Assisted and Ultrasound-Assisted Cataract Surgery with Focus on Endothelial Analysis

Femtosecond laser-assisted cataract surgery has the potential to make critical steps of cataract surgery easier and safer, and reduce endothelial cell loss, thus, improving postoperative outcomes. This study compared FLACS with the conventional method in terms of endothelial cells behavior, clinical outcomes, and capsulotomy precision.

METHODS

In a single-center, randomized controlled study, 130 patients with cataracta senilis received FLACS or conventional cataract surgery.

RESULTS

A significant endothelial cell loss was observed postoperatively, compared to the preoperative values in both groups. The endothelial cell counts was significantly better in the FLACS group in cataract grade 2 (p = 0.048) patients, compared to conventionally at 4 weeks. The effective phaco time was notably shorter in grade 2 of the FLACS group (p = 0.007) compared to the conventional. However, no statistically significant differences were found for the whole sample, including all cataract grades, due to the overall cataract density in the FLACS group being significantly higher (2.60 ± 0.58, p < 0.001) as compared to conventional methods (2.23 ± 0.42).

CONCLUSIONS

Low energy FLACS provides a better result compared to endothelial cell loss, size, and shape variations, as well as in effective phaco time within certain cataract grade subgroups. A complete comparison between two groups was not possible because of the higher cataract grade in the FLACS. FLACS displayed a positive effect on endothelial cell preservation and was proven to be much more precise.

Anterior segment optical coherence tomography scanning protocols and corneal thickness repeatability

PURPOSE

To examine the influence of anterior segment optical coherence tomography imaging protocols on the intraobserver and intrasession repeatability of epithelial, stromal, and total corneal thickness measurements.

METHODS

Repeated anterior segment optical coherence tomography (AS-OCT) images (Spectralis, Heidelberg) were obtained from 15 adults using single 8.3 mm wide horizontal line scans with an average of 2, 10, 20, 30, 50 and 100 B-scans. Volumetric scans consisting of nine 8.3 mm horizontal line scans encompassing a 1.3 mm vertical region were also captured (with 20 B-scans per line scan). Single point thickness measures (at the normal to the tangent of the anterior corneal surface) were compared with thickness measures averaged over the central 6 mm. The impact of B-scan averaging and intraobserver variability were examined for single line scans. For volumetric scans, the impact of the number of line scans upon intraobserver and intrasession variability were calculated.

RESULTS

Intraobserver repeatability did not vary significantly as a function of the number of averaged B-scans per line scan, but was lowest for 20-30 averaged B scans. For volumetric scans, increasing the number of line scans did increase scan duration (p < 0.001), with minimal impact upon the average scan quality index (p = 0.06). Averaging more than 3 line scans did not significantly improve intraobserver or intrasession repeatability for either single point or average thickness measurements.

CONCLUSION

AS-OCT volumetric scans with 3 lines each consisting of 20 B-scans with measurements averaged over a central 6 mm of the cornea provide highly repeatable measures of epithelial, stromal and total corneal thickness (95 % LoA ≤ ±3.2 μm for intraobserver repeatability and ≤ ±3.7 μm for intrasession repeatability). This scanning protocol can provide reliable information when monitoring subtle changes in corneal thickness.

Peripheral Hypertrophic Subepithelial Opacities of Corneal Grafts After Deep Anterior Lamellar Keratoplasty

PURPOSE

To investigate possible underlying etiologies of the development of peripheral graft hypertrophic subepithelial opacities (PGHSO) and to evaluate the effects of these opacities on visual outcomes after deep anterior lamellar keratoplasty (DALK).

METHODS

This prospective, interventional case series enrolled 29 eyes with keratoconus that underwent DALK and developed PGHSO (group 1). The control group consisted of 32 eyes with keratoconus that underwent DALK during the same period and had a clear graft at the final examination (group 2). Possible underlying risk factors for the development of PGHSO were investigated, and postoperative refractive and topographic outcomes were compared between the 2 study groups.

RESULTS

Eyes of group 1 had well-defined elevated peripheral subepithelial opacities of the corneal graft, originating from the donor-recipient junction. The central 4-mm area of the graft was clear in all eyes of this group. Compared with the controls, group 1 had flatter grafts at postoperative month 1 and a longer time interval from surgery to initial suture removal. The 2 study groups were comparable in other investigated factors, including the severity of keratoconus, surgical technique, duration of topical steroid use, and donor quality. No significant differences were observed between the case and control groups in postoperative visual acuity and graft surface regularity.

CONCLUSIONS

Graft flattening during the early postoperative period and prolonged time interval from surgery to initial suture removal might be factors predisposing to the development of PGHSO. This complication did not affect postoperative visual outcomes when the central 4-mm area of the graft remained clear.

Anterior Segment Optical Coherence Tomography: Applications for Clinical Care and Scientific Research

Anterior segment optical coherence tomography (AS-OCT) is a non-contact imaging technique that produces high-resolution images and quantitative measurements of the anterior segment and its anatomical structures. There has been rapid development of OCT technology over the past 2 decades, with the transition from time-domain to Fourier-domain OCT devices. By integrating these advancements in OCT technology, AS-OCT devices have evolved into versatile clinical and research tools for studies of the anterior segment and ocular surface. The primary purpose of this article was to review OCT technology and AS-OCT devices as well as applications of AS-OCT for clinical practice and scientific research. We first describe the different types of OCT technology, how they have been adapted for AS-OCT imaging, and differences between various AS-OCT devices. We then review the applications of AS-OCT for characterizing the anatomical structures of the anterior segment and aqueous outflow pathways, including the anterior chamber angle, trabecular meshwork, and Schlemm canal. We also describe glaucoma-related applications of AS-OCT imaging, which include evaluating patients for static and dynamic biometric risk factors of primary angle closure disease and assessing the efficacy of glaucoma interventions, such as laser peripheral iridotomy and glaucoma surgery. Finally, we review other clinical applications of AS-OCT imaging for detection and management of diseases of the ocular surface, cornea, and lens.