Lamellar Keratoplasty Research Articles

Microsporidial stromal keratitis: treatment outcomes, clinical manifestations, confocal microscopy and histopathology findings: a retrospective observational study

ObjectiveMicrosporidial stromal keratitis (MSK) is an uncommon disease. Only several case series have been reported. We aimed to describe the clinical manifestations, histopathology and treatment outcomes of MSK.Methods and analysisRetrospective...

Trends in infectious adverse events after elective optical keratoplasty (PK, EK, and ALK) - Ten years' analysis from an eye bank.

To report the clinical profile and donor characteristics of post-optical keratoplasty adverse events notified at an eye bank. Between January 2013 and December 2022, 37,041 donor corneas were utilized for keratoplasty, of which 16,531 were used for penetrating keratoplasty (PK), 12,171 for endothelial keratoplasty (EK), and 1356 for anterior lamellar keratoplasty (ALK). EK included 10,956 Descemet stripping automated endothelial keratoplasty (DSAEK) and 1215 Descemet membrane endothelial keratoplasty (DMEK). The adverse events reported within the first 6 weeks of optical keratoplasty were analyzed for donor-related parameters. A total of 41 (0.11%) recipients had post-keratoplasty infections. Of these, 33 occurred after EK (29 after DSAEK, and four after DMEK), two after ALK, and six after PK. The clinical presentation was keratitis alone in 16 eyes and associated with endophthalmitis in 25 eyes. The organisms isolated were gram-negative bacteria in 26 eyes, fungus in eight eyes, gram-positive bacteria in four eyes, mixed infection in five eyes, and microbiology inconclusive in seven eyes. The majority (78%) of the gram-negative infections were due to multidrug-resistant organisms. Most (88%) donor corneas were harvested from hospital premises. The most common cause of donor mortality was trauma. The median duration of presentation from surgery was 4.46 (range: 1-30) days. The death to preservation time was 4.18 (1.5-7.65) hours. The death to utilization time was 3 (2-4.7) days. The overall risk of infectious adverse events after keratoplasty was 0.11%, ranging from 0.08% to 0.36%. Most (80.4%) of the adverse events occurred after EK. The majority (78.9%) of the adverse events were of bacterial etiology, of which gram-negative infections (68.4%) were the most common. The trends and microbiological spectrum of organisms associated with infections should be thoroughly documented in eye banks to gain insights and formulate guidelines on the management of adverse events.

Outcomes of Corneal Transplantation for Herpetic Keratitis: A Narrative Review.

Herpes simplex virus (HSV) is one of the most common etiologic agents of corneal disease and a significant cause of corneal blindness worldwide. Although most cases can be successfully managed with medical therapy, HSV keratitis associated with visually significant stromal scarring often requires corneal transplantation for visual rehabilitation. While penetrating keratoplasty (PK) represented the traditional keratoplasty technique, the past few decades have seen a shift towards lamellar keratoplasty procedures, including deep anterior lamellar keratoplasty and mushroom keratoplasty. This paper describes the current surgical techniques and perioperative antiviral prophylaxis regimen for herpetic keratitis and reviews their postoperative clinical outcomes.

Tomographic and topographic predictive factors of big bubble formation during deep anterior lamellar keratoplasty in keratoconus

PurposeTo identify preoperative predictors of big bubble (BB) formation during deep anterior lamellar keratoplasty (DALK) in patients with keratoconus (KC).MethodsDesignRetrospective cohort study in an Italian tertiary centre.Study populationConsecutive patients with...

Assessment of Generative Artificial Intelligence (AI) Models in Creating Medical Illustrations for Various Corneal Transplant Procedures.

This study aimed to task and assess generative artificial intelligence (AI) models in creating medical illustrations for corneal transplant procedures such as Descemet's stripping automated endothelial keratoplasty (DSAEK), Descemet's membrane endothelial keratoplasty (DMEK), deep anterior lamellar keratoplasty (DALK), and penetrating keratoplasty (PKP). Methods: Six engineered prompts were provided to Decoder-Only Autoregressive Language and Image Synthesis 3 (DALL-E 3) and Medical Illustration Manager (MIM) to guide these generative AI models in creating a final medical illustration for each of the four corneal transplant procedures. Control illustrations were created by the authors for each transplant technique for comparison. A grading system with five categories with a maximum score of 3 points each (15 points total) was designed to objectively assess AI's performance. Four independent reviewers analyzed and scored the final images produced by DALL-E 3 and MIM as well as the control illustrations. All AI-generated images and control illustrations were then provided to Chat Generative Pre-Trained Transformer-4o (ChatGPT-4o), which was tasked with grading each image with the grading system described above. All results were then tabulated and graphically depicted. The control illustration images received significantly higher scores than produced images from DALL-E 3 and MIM in legibility, anatomical realism and accuracy, procedural step accuracy, and lack of fictitious anatomy (p<0.001). For detail and clarity, the control illustrations and images produced by DALL-E 3 and MIM received statistically similar scores of 2.75±0.29, 2.19±0.24, and 2.50±0.29, respectively (p=0.0504). With regard to mean cumulative scores for each transplant procedure image, the control illustrations received a significantly higher score than DALL-E 3 and MIM (p<0.001). Additionally, the overall mean cumulative score for the control illustrations was significantly higher than DALL-E 3 and MIM (14.56±0.51 (97.1%), 4.38±1.2 (29.2%), and 5.63±1.82 (37.5%), respectively (p<0.001)). When assessing AI's grading performance, ChatGPT-4o scored the images produced by DALL-E 3 and MIM significantly higher than the average scores of the independent reviewers (DALL-E 3: 10.0±0.0 (66.6%) vs. 4.38±1.20 (29.2%),p<0.001; MIM: 10.0±0.0 (66.6%) vs. 5.63±1.82 (37.5%), p<0.001). However, mean scores for the control illustrations between ChatGPT-4o and the independent reviewers were comparable (15.0±0.0 (100%) vs. 14.56±0.13 (97.1%); p>0.05). AI is an extremely powerful and efficient tool for many tasks, but it is currently limited in producing accurate medical illustrations for corneal transplant procedures. Further development is required for generative AI models to create medically sound and accurate illustrations for use in ophthalmology.

Surgical Strategies to Manage Stromal Interface Irregularity Following Deep Anterior Lamellar Keratoplasty.

The purpose of this study was to describe the various surgical approaches to manage stromal interface irregularity following deep anterior lamellar keratoplasty (DALK). This interventional case series included patients requiring repeat keratoplasty procedures for stromal interface opacity and/or irregularity following DALK. The following surgical techniques with the aim of restoring transparency and regularity of the central optical zone and improving visual acuity in eyes that underwent unsuccessful DALK were performed: 1) simple anterior lamellar graft exchange, 2) repeat DALK with pneumatic dissection, 3) repeat DALK with deepening of manual lamellar dissection, 4) small diameter stripping of the central stroma-endothelium-Descemet complex and its replacement with a new endothelial lamella, and 5) 2-piece microkeratome-assisted mushroom penetrating keratoplasty. Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), slit-lamp examination, tonometry, and anterior corneal tomography were evaluated preoperatively, as well as 3, 6, and 12 months after surgery. Intraoperative and postoperative complications were recorded. Preoperative BCVA was less than 20/200 and improved to 20/40 or better in all cases, reaching 20/20 in 1 patient. Corneal clarity was restored in all eyes, and no recurrence of underlying disease was observed. No intraoperative or postoperative complications were reported. This case series describes several successful surgical approaches to improve the transparency and regularity of stromal interface obtained after a DALK procedure; the choice of the technique should be customized for the single eyes to still maintain the advantages of lamellar or minimally invasive grafts.

Interpretable Machine Learning-Based Risk Score for Predicting Ten-Year Corneal Graft Survival After Penetrating Keratoplasty and Deep Anterior Lamellar Keratoplasty in Asian Eyes.

To predict 10-year graft survival after deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) using a machine learning (ML)-based interpretable risk score. Singapore Corneal Transplant Registry patients (n = 1687) who underwent DALK (n = 524) or PK (n = 1163) for optical indications (excluding endothelial diseases) were followed up for 10 years. Variable importance scores from random survival forests were used to identify variables associated with graft survival. Parsimonious analysis using nested Cox models selected the top factors. An ML-based clinical score generator (AutoScore) converted identified variables into an interpretable risk score. Predictive performance was evaluated using Kaplan-Meier (KM) curves and time-integrated AUC (iAUC) on an independent testing set. Mean recipient age was 51.8 years, 54.1% were male, and majority were Chinese (60.0%). Surgical indications included corneal scar (46.5%), keratoconus (18.3%), and regraft (16.2%). Five-year and ten-year KM survival was 93.4% and 92.3% for DALK, compared with 67.6% and 56.6% for PK (log-rank P < 0.001). Five factors were identified by ML algorithm as predictors of 10-year graft survival: recipient sex, preoperative visual acuity, choice of procedure, surgical indication, and active inflammation. AutoScore stratified participants into low-risk and high-risk groups-with KM survival of 73.6% and 39.0%, respectively (log-rank P < 0.001). ML analysis outperformed traditional Cox regression in predicting graft survival beyond 5 years (iAUC 0.75 vs. 0.69). A combination of ML and traditional techniques identified factors associated with graft failure to derive a clinically interpretable risk score to stratify PK and DALK patients-a technique that may be replicated in other corneal transplant programs.

Influence of Opacity Depth on Big Bubble Formation During Deep Anterior Lamellar Keratoplasty in Corneal Stromal Scars.

To identify the key preoperative predictors of big bubble (BB) formation during deep anterior lamellar keratoplasty in patients with corneal stromal scars (CSS). This retrospective cohort study included consecutive patients with CSS after infective keratitis who underwent BB-deep anterior lamellar keratoplasty between January 2021 and July 2023 at a tertiary referral center. Topographic and tomographic data were collected to compare the rates and types of BB formations. Anterior segment optical coherence tomography (AS-OCT) was employed to assess the maximum depth of opacity by dividing the stroma into 3 zones of equal thickness: anterior (stage A), mid (stage B), and posterior stroma (stage C). Multivariate logistic regression analysis was performed to identify the potential preoperative predictors of bubble formation. Pneumatic dissection was achieved in 13 of 33 eyes (39.4%), with 11 BB type 1 eyes (33.3%) and 2 BB type 2 eyes (6.1%). According to AS-OCT grading, bubble formation was more frequent with CSS involving more superficial stromal layers (P <0.032). In the eyes with stage C, bubble formation failed 12 out of 14 times (85.7%, P <0.026). Spearman correlation showed that bubble formation was inversely associated with the AS-OCT grading (rho = -0.443, P = 0.001). After logistic regression analysis, AS-OCT grading was found to be the sole factor that predicted bubble formation (coeff. -1.58, confidence interval 95% -3.03 to -0.12, P = 0.034). Depth of opacity in CSS was the key determinant for predicting the success of pneumatic dissection, as advanced AS-OCT stages are strongly associated with BB failure.

Repeat Femtosecond-Assisted Anterior Lamellar Keratoplasty for Recurrence of TGF B I Dystrophy in Eyes After Previous FALK.

To report the management of recurrent TGF BI dystrophy after prior femtosecond-assisted anterior lamellar keratoplasty (FALK) with repeat FALK. Clinical and histopathological study of 2 eyes of 2 patients with a recurrence of TGFBI dystrophy. Patient 1 had Reis-Buckler corneal dystrophy, and patient 2 had granular corneal dystrophy GCD type 1. Patient 1 had FALK 8 years ago, when she was 23 years old. Patient 2 had FALK 7 years ago at the age of 24 years. Slit-lamp examination showed recurrence in the subepithelial layer of the anterior lamellar graft as confluent chalky white granular deposits. Anterior segment optical coherence tomography highlighted the deposits in the subepithelial region of the anterior lamellar graft. The anterior lamellar graft with deposits was removed and replaced with another graft created using femtolaser dissection of a healthy donor. The parameters for femtosecond laser-assisted donor dissection was similar to the size and depth as the previously used donor. The best-corrected visual acuity was restored to 20/30 in patient 1 and 20/25 in patient 2. The histology of the anterior lamellar graft showed eosinophilic deposits between the epithelium and the Bowman layer in both samples. In addition, the corneal sample from patient 2 revealed Bowman layer breach at some places and few deposits at 1 edge of the lamellar graft. Repeat FALK with a healthy donor is effective in the management of recurrence of deposits. The histology of the recurrence in the anterior lamellar graft revealed eosinophilic deposits predominantly between the epithelium and Bowman layer.

Evolving Trends in the Diagnosis and Management of Keratoconus Over 3 Decades.

To report the trends in the clinical presentation, diagnosis, and management of keratoconus (KC) in patients presenting to a multitier hospital network over 33 years. This retrospective study included patients with KC presenting from 1987 to 2020. Patients with KC in at least 1 eye were included. The data of 20,576 patients included in this study were retrieved from the electronic medical record database. Data on patient demographics, ocular diagnosis, contact lens usage, and surgical history were collected and exported for analysis. Descriptive statistics and chi square test were used for statistical analysis. A total of 20,576 KC cases were seen from 1987 to 2020. Mean age at diagnosis reduced from 29.3 years (1987-1991) to 22.2 years (2016-2020). Adults (76.64%) were commonly affected with a majority being male (61.25%). Use of contact lenses increased from 4.34% (2002-2006) to 11.23% (2016-2020). Of the total number of surgical interventions, collagen crosslinking (CXL) constituted more than 1/5th (22.28%) between 2007 and 2011, which increased to more than half between 2012 and 2016 (53.61%) and almost 3/4th (72.53%) between 2017 and 2020. Advances in lamellar surgery have led to more patients undergoing deep anterior lamellar keratoplasty (DALK) as compared with penetrating keratoplasty. In the last 8 years, 17.2% patients underwent surgery and the most common was CXL (14.77%) followed by DALK (1.72%) and penetrating keratoplasty (1.04%). We report the trends in the clinical presentation and management of KC over 3 decades. In the last 33 years, advances in diagnostics have helped diagnose KC earlier. Contact lenses and advances in CXL have reduced the number of keratoplasties in KC, DALK being more common.

TACSTD2 in gelatinous drop-like corneal dystrophy: variant functional analysis and expression in the cornea after limbal stem cell transplantation

Gelatinous drop-like corneal dystrophy (GDLD) is a rare autosomal recessive eye disease. GDLD is characterized by the loss of barrier function in corneal epithelial cells (CECs) and amyloid deposition due to pathogenic variants in the TACSTD2 gene. Limbal stem cell transplantation (LSCT) has been suggested as an effective therapeutic alternative for patients with GDLD. However, despite LSCT, amyloid deposition recurs in some patients. The pathogenesis of recurrence is poorly studied. We present the case of a patient with GDLD. Genetic analysis revealed a homozygous deletion, NM_002353.3:c.653del, in the TACSTD2 gene. Functional analysis in a cell model system revealed the loss of the transmembrane domain and subcellular protein mislocalization. The patient with GDLD underwent direct allogeneic LSCT with epithelial debridement followed by deep anterior lamellar keratoplasty 10 months later due to amyloid deposition and deterioration of vision. Taken together, the results of transcriptome analysis and immunofluorescence staining of post-LSCT corneal sample with amyloid deposits obtained during keratoplasty demonstrated complete restoration of wild-type TACSTD2 expression, indicating that donor CECs replaced host CECs. Our study provides experimental evidence that amyloid deposition can recur after LSCT despite complete restoration of wild-type TACSTD2 expression.

Outcomes of Donor Corneas of Different Thicknesses From Endothelial Keratoplasty in Deep Anterior Lamellar Keratoplasty for Keratoconus.

To evaluate the outcomes of divided residual donor corneas obtained from endothelial keratoplasty in keratoconus with deep anterior lamellar keratoplasty (DALK). In this retrospective, comparative, clinical study, 103 keratoconic eyes that underwent DALK were enrolled; 67 eyes received thin grafts from Descemet stripping automated endothelial keratoplasty, and 36 received thick grafts from Descemet membrane endothelial keratoplasty. Baseline and postoperative central corneal thickness (CCT), inferior corneal thickness, uncorrected distance visual acuity, corrected distance visual acuity, corneal astigmatism, mean keratometry, biomechanical properties, and complication rates were measured. Six months after transplantation, the group receiving thin grafts had a CCT of only 455.1 ± 43.0 μm, whereas that of the group receiving thick grafts was 546.7 ± 44.2 μm. Both CCT and inferior corneal thickness in the thin group were significantly lower than those in the thick group (measured with Pentacam at 36 months, P < 0.001) and remained throughout the 5-year follow-up period. Both procedures had comparable postoperative logarithm of the minimum angle of resolution UDVAs, logarithm of the minimum angle of resolution corrected distance visual acuity, astigmatism, and mean keratometry values (36 months; P = 0.335, 0.286, 0.680, and 0.365, respectively). Corneal biomechanical analysis revealed that the thin group had a significantly higher stiffness parameter at the first applanation than the thick group at the 2-year follow-up (P = 0.036) while other parameters were equivalent. The outcomes of keratoplasty with donor tissue are comparable regardless of the thickness of the graft, which suggests that transplantation with either type of the split corneal procedure for DALK in patients with keratoconus is feasible.

Clinical profile and outcomes of rejection after deep anterior lamellar keratoplasty in keratoconus.

To report the clinical features and management outcomes of rejection after deep anterior lamellar keratoplasty (DALK). The clinical features, indications, predisposing risk factors, management, and outcome of six eyes of six patients with rejection after DALK were analyzed retrospectively. The median time of rejection from the day of surgery was 12 (range 3-36) months. Median duration of symptoms was 4 (range 2-28) days. The indication for DALK was keratoconus in all eyes. The clinical features at presentation included graft haze, vascularization, and melt at the graft-host junction. The risk factors noted were noncompliance to steroids in all eyes, vernal conjunctivitis (four eyes), and eccentric graft (one eye). The rejection episode reversed with topical steroids in all eyes and intravenous methylprednisolone in one eye. One eye developed secondary fungal keratitis after initial recovery and one eye had a second episode of rejection 3 months later, which resulted in progressive vessels and lipid keratopathy in the visual axis. The median best corrected visual acuity was 20/40 (range 20/30-20/200). Severe stromal rejection can present with graft melt. Repeat episodes of rejection can occur on sudden cessation of topical steroids. Prompt recognition of clinical signs and symptoms with timely management helps in quick reversal of the rejection episode. Reversal of graft rejection results in good visual outcomes.

Different Thicknesses of Acellular Porcine Corneal Stroma on Prognosis of Fungal Corneal Ulcers Treated by Lamellar Keratoplasty: A Five-Year Retrospective Study.

To compare the prognosis and efficacy of acellular porcine corneal stroma (APCS) with different thicknesses for the treatment of fungal corneal ulcers by lamellar keratoplasty (LKP). A total of 52 patients who underwent LKP with APCS for the treatment of fungal corneal ulcers were included in this retrospective study. Patients were divided into 2 groups according to the different thicknesses of APCS (0.30 ± 0.05 mm, L2 group, n = 20; 0.40 ± 0.05 mm, L3 group, n = 32). Observation indicators included best corrected visual acuity, graft transparency, corneal neovascularization, ocular irritation symptoms, corneal epithelial healing time, graft survival, central corneal thickness at 1 year after surgery, and postoperative complications. Compared with the L3 group, the L2 group had better postoperative best corrected visual acuity and graft transparency (P < 0.001), less corneal neovascularization (P < 0.001), and lower incidence of complications (P < 0.05). There were significant differences in ocular irritation symptoms between the 2 groups (P < 0.05) at 3 and 6 months postoperatively, which might be related to the higher recurrence rate and graft rejection rate in the L3 group. The comparison of postoperative epithelial healing time also showed significant differences in 2 groups (P < 0.01). The 1-year survival rate was up to 63.5% in both groups, with no significant difference (P < 0.05). However, the risk of transplantation was less in the L2 group. Both APCS thicknesses could provide adequate central corneal thickness at 1 year after surgery (P > 0.05). APCS was safe and effective in the treatment of fungal corneal ulcers by LKP. Thinner grafts should be preferred for LKP for fungal corneal ulcers to reduce the risk of grafting.

Endothelial keratoplasty in integrity-damaged iridolenticular diaphragm

The review presents methods for performing endothelial keratoplasty (EK) in patients with endothelial corneal dysfunction, combined with discontinuities of the iridolenticular diaphragm as reflected in the PubMed, Scopus and eLibrary reference databases for the period ending in 2022. EK performed according to a variety of techniques allows achieving good clinical and functional results and reducing the risk of complications at different stages of treatment of patients with endothelial insufficiency. Another important advantage of EK as compared to penetrating keratoplasty is the fact that it can be repeated multiple times, which is relevant for patients with severe combined pathologies. Considering the plethora of modifications of posterior lamellar keratoplasty and transplantation of the Descemet's membrane and endothelium for cases with combined damages of the integrity of the iridolenticular diaphragm, the number of affected patients may be even more numerous than presented in the publications reviewed. The variety of literature data shows that the search for a universal technique of EK to be performed on patients with various disorders of the iridolenticular diaphragm is likely to continue.

A Retrospective Analysis of Corneal Dermoid.

Corneal dermoid is a congenital benign tumor and ocular malformation, often diagnosed at birth or in early childhood. Its treatment and long-term prognosis remain under-researched, necessitating further investigation. This study aims to investigate the epidemiological and clinical characteristics of corneal dermoid, evaluate the efficacy of different surgical methods, and identify factors influencing treatment outcomes. A retrospective analysis was conducted on the clinical data of 58 patients treated for corneal dermoid at our hospital from 2017 to 2021. Patients' demographic information, tumor characteristics, surgical methods, and postoperative outcomes were collected and analyzed. Descriptive statistics, independent sample t-test, chi-square (χ 2) test, and Spearman correlation analysis were used to evaluate the distribution characteristics and intergroup differences of corneal dermoid. The average age of the patients was 6.3 years, with 55.2% being male and 44.8% female. The right eye was affected in 63.8% of cases, with the temporal limbus being the most common site (75.9%). Pathological examination revealed tumors covered by squamous epithelium, containing hair follicles, sebaceous glands, adipose tissue, and fibrous tissue; some cases also had cartilage and glandular tissue. Surgical methods included corneal dermoid excision (100%), lamellar keratoplasty (37.9%), amniotic membrane grafting (31.0%), and autologous limbal stem cell transplantation (8.6%). None of the 50 followed up patients experienced tumor recurrence. Postoperative vision improved in 58.0% of patients, with more females (61.9%) experiencing visual impairment compared to males (38.1%) (χ²=4.711, p=0.030). This study analyzed 58 corneal dermoid patients treated from 2017 to 2021, focusing on epidemiological and clinical characteristics, surgical efficacy, and treatment outcomes. It identified common pathological features and effective surgical methods, with no tumor recurrence in followed up patients. The study highlights the need for further research with larger sample sizes and longer follow-up periods.

Pediatric keratoconus in a tertiary eye hospital in Eastern province, Saudi Arabia: Patient characteristics and management outcomes.

This study investigates pediatric keratoconus in a tertiary eye hospital in Eastern Province, Saudi Arabia, aiming to understand the presenting features and treatment outcomes in this high-prevalence region. The research addresses pediatric keratoconus clinical profile and management strategies. A retrospective cohort study was conducted from 2022 to 2023, reviewing medical records of pediatric keratoconus patients. Demographic data, clinical characteristics, risk factors, presenting symptoms, and treatment outcomes were recorded. Severity staging was performed based on Amsler-Krumeich's classification. The study included 218 eyes from 109 pediatric keratoconus patients, with 65% of male and 35% of female patients. Decreased vision was the most common symptom (92%), and risk factors included a family history of keratoconus (9%) and vernal keratoconjunctivitis (6%). Stage 1 was the most frequent in both age groups (<14 years and ≥ 14 years). Treatment strategies included corneal collagen cross-linking (CXL), hard contact lenses, corneal rings, deep anterior lamellar keratoplasty (DLK), and penetrating keratoplasty. Significant improvements were observed in visual acuity, refractive errors, and tomographic parameters following these interventions. This study provides valuable insights into pediatric keratoconus in Saudi Arabia, emphasizing the importance of early diagnosis and interventions for better outcomes. Larger, multicenter prospective studies are essential for a comprehensive understanding of pediatric keratoconus and its optimal management. The findings contribute to the knowledge base and guide future research to improve patient quality of life.

One-Step Intraoperative Optical Coherence Tomography Guided Tunnel, Mushroom Femtosecond Laser Big Bubble Deep Anterior Lamellar Keratoplasty.

The aim of our study is to investigate the feasibility and outcomes of using a femtosecond laser (FSL) platform (Ziemer LDV Z8) for deep anterior lamellar keratoplasty (DALK), enabling the creation of mushroom-shaped graft-host junctions, lamellar cuts, and intrastromal tunnels, to facilitate the big bubble, in one step. We included wet lab experiments on nine porcine eyes to assess the laser accuracy and cuts depth using an anterior segment (AS) OCT. This was followed by an interventional prospective case series on 10 eyes with variant corneal pathologies. The Z8 system, with in-built intraoperative optical coherence tomography (iOCT), guided corneal scans and directed the cuts. ASOCT showed visible mushroom configurations, lamellar cuts, and tunnels. Deviations from the target were 1.6%, 2.6%, and 3.5%. Anterior lamellar removal was easy in all clinical cases, including corneal scarring. The intrastromal tunnel was found at the preset location and the mushroom configuration was acquired. A big bubble was achieved in all cases. Type 1, 2, and 3 bubbles were formed in eight, one, and one case, respectively. We describe a new approach to DALK in which the in-built iOCT-guided FSL enables safe, precise, controlled, and reproducible desired cuts in one step. The preliminary clinical outcomes were favorable.

Design and Evaluation of an Eye Mountable AutoDALK Robot for Deep Anterior Lamellar Keratoplasty.

Partial-thickness corneal transplants using a deep anterior lamellar keratoplasty (DALK) approach has demonstrated better patient outcomes than a full-thickness cornea transplant. However, despite better clinical outcomes from the DALK procedure, adoption of the technique has been limited because the accurate insertion of the needle into the deep stroma remains technically challenging. In this work, we present a novel hands-free eye mountable robot for automatic needle placement in the cornea, AutoDALK, that has the potential to simplify this critical step in the DALK procedure. The system integrates dual light-weight linear piezo motors, an OCT A-scan distance sensor, and a vacuum trephine-inspired design to enable the safe, consistent, and controllable insertion of a needle into the cornea for the pneumodissection of the anterior cornea from the deep posterior cornea and Descemet's membrane. AutoDALK was designed with feedback from expert corneal surgeons and performance was evaluated by finite element analysis simulation, benchtop testing, and ex vivo experiments to demonstrate the feasibility of the system for clinical applications. The mean open-loop positional deviation was 9.39 µm, while the system repeatability and accuracy were 39.48 µm and 43.18 µm, respectively. The maximum combined thrust of the system was found to be 1.72 N, which exceeds the clinical penetration force of the cornea. In a head-to-head ex vivo comparison against an expert surgeon using a freehand approach, AutoDALK achieved more consistent needle depth, which resulted in fewer perforations of Descemet's membrane and significantly deeper pneumodissection of the stromal tissue. The results of this study indicate that robotic needle insertion has the potential to simplify the most challenging task of the DALK procedure, enable more consistent surgical outcomes for patients, and standardize partial-thickness corneal transplants as the gold standard of care if demonstrated to be more safe and more effective than penetrating keratoplasty.

Глазной тканевой банк и фемтотехнологии как основа развития кератопластики

Abstract Eye tissue bank and femtotechnologies as fundamentals for keratoplasty development E.V. Boiko, I.E. Panova, A.V. Titov, Ya.I. Masian, A.A. Varavka, D.R. Mirsaitova, O.D. Yagmurov S. Fyodorov Eye Microsurgery Federal State Institution, Saint Petersburg Branch, Saint Petersburg, Russian Federation I.I. Mechnikov North-Western State Medical University, Saint Petersburg, Russian Federation Saint Petersburg State University, Saint Petersburg, Russian Federation Bureau of Forensic Medical Examination, Saint Petersburg, Russian Federation Purpose.To evaluate development of keratoplasty in the St. Petersburg branch, taking into account eye tissue bank opening and femtotechnologies intergation. Material and methods. A retrospective analysis of the structure and quantity of keratoplasty in combination with femtosecond laser was carried in Saint Petersburg branch of S. Fyodorov Eye Microsurgery Federal State Institution. Data were analyzed regarding 2-time intervals: from 1990 to 2019 and from 2019 to 2022. Results.Between 1990 and 2019, 1367 corneal transplantations were performed (an average of 46 transplantations per year). Penetrating keratoplasty had a leading position in the structure – 1159 operations (84.8%). At the same time, the lamellar keratoplasty segment took only 15.2% (208 operations), and femtosecond laser was used only in 1% of operations (14 operations). In the period from2019 to 2023, 674 keratoplasty were performed, percentage of penetrating keratoplasty decreased to 50.8% (343 operations), and number of lamellar keratoplasty cases increased to 49.2% (331 operations). Femtosecond laser was used in 73.4% of operations (495 operations). Conclusion.Based on the results of a retrospective analysis, the advantages of eye tissue bank opening and a femtosecond laser integration into the work of the St. Petersburg branch were determined. Key words:eye tissue bank, femtosecond laser, keratoplasty