Keratoconus: imaging modalities and management.

Background: Keratoconus (KCN) is characterized by gradual thinning and steepening of the cornea, which can lead to significant vision problems owing to high astigmatism, corneal scarring, or even corneal perforation. The detection of KCN in its early stages is crucial for effective treatment. In this review, we describe current advances in the diagnosis and treatment of KCN. Methods: This narrative review focuses on recent advancements in the diagnosis and treatment of KCN, especially evolving approaches and strategies. To ensure the inclusion of the most recent literature, relevant publications discussing advanced imaging techniques and treatment options for KCN were extensively gathered from the PubMed/MEDLINE and Google Scholar databases. The following index terms and keywords were used for the online search: keratoconus, diagnosis of keratoconus, advances in the diagnosis of keratoconus, topography or tomography, anterior segment optical coherence tomography, treatment of keratoconus, advances in the treatment of keratoconus, collagen crosslinking, intrastromal ring, keratoplasty, and new techniques in keratoconus. Results: Various screening methods such as corneal topography, tomography, anterior segment optical coherence tomography, and assessment of corneal biomechanics have been developed to identify KCN in its early stages. After diagnosis, KCN management focuses on preventing disease progression. Corneal collagen crosslinking is a minimally invasive treatment that can slow or stop the progression of the condition. Recent research has also explored the use of copper sulfate eye drops (IVMED-80) as a noninvasive treatment to prevent the progression of KCN. Current treatment options for visual improvement include scleral lenses, intracorneal ring segments, corneal allogeneic intrastromal ring segments, and deep anterior lamellar keratoplasty. Recently, novel alternative procedures, such as isolated Bowman layer transplantation, either as a corneal stromal inlay or onlay, have demonstrated encouraging outcomes. Artificial intelligence has gained acceptance for providing best practices for the diagnosis and management of KCN, and the science of its application is contentiously debated; however, it may not have been sufficiently developed. Conclusions: Early detection and advancements in screening methods using current imaging modalities have improved diagnosis of KCN. Improvement in the accuracy of current screening or diagnostic tests and comparison of their validities are achievable by well-designed, large-scale, prospective studies. The safety and effectiveness of emerging treatments for KCN are currently being investigated. There is an ongoing need for studies to track progress and evaluate clinicians' knowledge and practices in treating patients with KCN. Artificial intelligence capabilities in management approach considering the currently available imaging modalities and treatment options would best benefit the patient.

Postoperative Astigmatism after Keratoplasty: A Systematic Review Meta-Analysis Based on PRISMA.

Background: The number of corneal transplants is rising, with the aim to treat a spectrum of diseases ranging from dystrophies to corneal opacities caused by trauma or chemical burns. Refractive outcomes after this procedure are often impossible to predict and associated with high levels of astigmatism. However, there are many techniques that affect the reduction of astigmatism and improve the quality of life of patients. Objectives: The aim was to compare the improvement in postoperative visual acuity (logMAR) and amount of corneal astigmatism (Diopters) after corneal keratoplasty in patients who additionally underwent a surgical procedure, which affects the reduction in postoperative astigmatism, and to determine the most effective method. Search Methods and Selection Criteria: A thorough search was carried out across online electronic databases including PubMed, Embrase, Ovid MEDLINE, Scopus, and Web of Science, using combinations containing the following phrases: postoperative astigmatism, post-keratoplasty astigmatism, anterior lamellar keratoplasty (ALK), deep anterior lamellar keratoplasty (DALK), posterior lamellar keratoplasty, endothelial keratoplasty (EK), penetrating keratoplasty (PK), corneal transplant, keratoplasty, refractive surgery, kerato-refractive surgery, laser in situ keratomileusis (LASIK), and femtosecond LASIK. This was to determine all English-language publications that discuss refractive operations for postoperative or post-keratoplasty astigmatism. These bibliographies were searched for English-language publications published between 2010 and 2023. We proceeded to review each detected record's reference list. Data Extraction: Study characteristics such as study design, sample size, participant information, operations performed, and clinical outcomes were all extracted. Data Statistical Analyses: The Comprehensive Meta-Analysis software (version 3.3.070, 2014) was used to perform the analysis. The threshold of 0.05 for p-values was considered statistically significant. All effect sizes are reported as standardized differences (Std diff) in means with a 95% confidence interval (CI) and visualized graphically as forest plots. Publication bias is presented as a funnel plot of standard error by Std diff in means. Four methods were used to evaluate the heterogeneity among the studies: Q-value, I2, chi-square (χ2), and tau-squared. Main Results: We included 21 studies that randomized 1539 eyes that underwent corneal transplantation surgery either by PKP, DALK, or DSEAK techniques. The results showed the most significant improvement in the visual acuity and significant decrease in the corneal astigmatism after laser surgery procedures, like femtosecond-assisted keratotomy after DALK and PKP and LASIK after DSEAK.

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.

The incidence of severe complications in acanthamoeba keratitis: Qualitative and quantitative systematic assessment.

Acanthamoeba keratitis (AK) is a rare, sight-threating corneal infection. The disease is challenging to diagnose and treat, and the amoeba can rapidly encyst, persisting in the tissue and causing recurrences. Medical therapy is conventionally considered the first line treatment, but advanced cases could require more invasive treatments like a "chaud" corneal transplant. We review the incidence of severe complications in patients affected by AK. Of 439 reports screened, 158 met our inclusion criteria. Incidence of severe complications was low, with 2.21 % patients developing perforation, 1 % requiring evisceration/enucleation and less than 1 % developing endophthalmitis. Corneal transplantation was required in 16.68 % of the cases. According to our results, and considering the reported incidences of these complications in other infectious keratitis, AK patients have an overall low risk of developing perforation, endophthalmitis, and enucleation/evisceration. Nevertheless, data available in the literature remain poor, and further randomized control trials are needed to confirm our findings.

Small-diameter acellular porcine corneal stroma for peripheral corneal ulceration treatment.

AIM: To evaluate the clinical efficacy of small-diameter acellular porcine corneal stroma (SAPS) for the treatment of peripheral corneal ulceration (PCU). METHODS: This retrospective clinical study included 18 patients (18 eyes) with PCU between April 2018 and December 2020. All patients had PCU and underwent lamellar keratoplasty with SAPS. Observation indicators included preoperative and postoperative best-corrected visual acuity (BCVA) and transparency of SAPS. The infection control rate in the surgical eye-lesion area was also calculated. RESULTS: Eighteen patients underwent lamellar keratoplasty with SAPS to treat PCU. None of the patients experienced rejection after 6mo (18/18) and 12mo (16/16) of follow-up. The BCVA (0.47±0.30) at the 6mo follow-up after operation was significantly improved compared with the baseline (0.99±0.80), and the difference was statistically significant (Z=-3.415, P<0.05). The BCVA at the 12mo follow-up after operation was not statistically significant compared to the 6mo (Z=0, P=1). With time, the SAPS graft gradually became transparent. At the 6mo (18/18) and 12mo (16/16) follow-up, none of the patients had recurrent corneal infection. CONCLUSION: SAPS is clinically effective in the treatment of PCU, improving the patient's BCVA and reducing the incidence of rejection after keratoplasty.

[Modern techniques and features of selective keratoplasty]. / Sovremennye tekhnologii i vozmozhnosti selektivnoi keratoplastiki.

Selective keratoplasty involves replacing the affected layers of the cornea with similar donor tissue. In case of pathological changes in the middle and posterior stroma, deep anterior lamellar keratoplasty (DALK) is performed. Chronic corneal edema caused by endothelial dysfunction is an indication for endothelial keratoplasty - Descemet membrane endothelial keratoplasty (DMEK) or Descemet Stripping Endothelial Keratoplasty (DSAEK). Compared to penetrating keratoplasty (PK), these operations are characterized by a low risk of damage to intraocular structures and a relatively short rehabilitation period. Complications of selective keratoplasty include the formation of a false chamber between the lamellar graft and the recipient's cornea, ocular hypertension during anterior chamber air tamponade. Persistent epithelial defect can be a sign of primary graft failure in DALK, DSAEK and DMEK. Selective keratoplasty is characterized by a lower incidence of immune rejection than PK. In some cases, DALK can be complicated by corneal changes related to suture fixation of the graft. Long-term postoperative use of topical glucocorticoids can cause ocular hypertension and cataracts.

Large-diameter deep anterior lamellar keratoplasty: A narrative review.

Deep anterior lamellar keratoplasty (DALK) involves the selective replacement of diseased corneal stroma while preserving healthy unaffected endothelium. While DALK has failed to gain widespread popularity, improved visual and refractive outcomes of large-diameter grafts, which patients directly perceive following suture removal, may represent a compelling reason to shift toward DALK. Since the unaffected host endothelium is retained, DALK offers the opportunity to use large-diameter grafts, which reliably achieves maximum visual potential without an increased risk of immune-mediated stromal rejection. In this narrative review, we evaluate the current evidence on large-diameter DALK including surgical technique and clinical outcomes.

Comparison of therapeutic effects between big-bubble deep anterior lamellar keratoplasty and penetrating keratoplasty for medically unresponsive Acanthamoeba keratitis.

PURPOSE: To compare the outcomes of big-bubble deep anterior lamellar keratoplasty (BB-DALK) and penetrating keratoplasty (PKP) in the management of medically unresponsive Acanthamoeba keratitis (AK). METHODS: This retrospective study included 27 eyes of BB-DALK and 24 eyes of PKP from a tertiary ophthalmology care centre. Glucocorticoid eye drops were subsequently added to the treatment plan 2 months postoperatively based on the evaluation using confocal laser scanning microscopy. The clinical presentations, best-corrected visual acuity (BCVA), postoperative refractive outcomes, graft survival, and Acanthamoeba recurrence were analyzed. RESULTS: The AK patients included in the study were in stage 2 or stage 3, and the percentage of patients in stage 3 was higher in the PKP group (P = 0.003). Clinical presentations were mainly corneal ulcers and ring infiltrates, and endothelial plaques, hypopyon, uveitis and glaucoma were more common in the PKP group (P = 0.007). The BCVA and the graft survival rate showed no statistically significant differences between the two groups at 1 year after surgery. However, 3 years postoperatively, the BCVA of 0.71 ± 0.64 logMAR, the graft survival rate of 89.5%, and the endothelial cell density of 1899 ± 125 cells per square millimeter in the BB-DALK group were significantly better than those of the PKP group (P = 0.010, 0.046, and 0.032, respectively). 3 eyes (11.1%) in the BB-DALK group and 2 eyes (8.3%) in the PKP group experienced Acanthamoeba recurrence, but the rates showed no statistically significant difference between the two groups (P = 1.000). In the PKP group, immune rejection and elevated intraocular pressure were observed in 5 and 6 eyes, respectively. CONCLUSION: Corneal transplantation is recommended for AK patients unresponsive to antiamoebic agents. The visual acuity and graft survival can be maintained after BB-DALK surgery. Acanthamoeba recurrence is not related to the surgical approach performed, whereas complete dissection of the infected corneal stroma and delayed prescribing of glucocorticoid eye drops were important to prevent recurrence.

Influence of Donor Factors on Descemet Membrane Endothelial Keratoplasty (DMEK) Graft Preparation Outcome.

Purpose: To determine which donor characteristics, like previous diseases and surgeries, influence the severity of the DM/endothelial lamella preparation prior to DMEK-surgery. Patients and Methods: Retrospective cross-sectional single-center study is presented. Eight hundred and forty-six eyes with DMEK-surgery between 01/2018 and 01/2021 performed at the University Hospital Cologne, Germany, were included. Information regarding the donors' previous diseases and surgeries were provided by a large database of a cornea bank (Multi Tissue Bank Mecklenburg-Vorpommern) and merged with the Cologne DMEK database, which contains information regarding preparation characteristics of the surgeon-prepared graft directly preoperatively. Three preparation groups (easy, difficult and very difficult) were correlated to the donors' previous diseases and surgeries. The following characteristics were used for the assignment in one of the three groups: stripping difficulty, rolling and staining behavior, central and peripheral adherences, tissue fragility and DM-splitting. Results: Significant risk factors for DM-splitting were diabetes mellitus (DMel) type II, heart failure, chronic kidney disease and previous cataract surgery (p=0.022, p=0.012; p=0.047 and p<0.001 respectively). Previous DMel (especially type 2) was significantly associated with the occurrence of central adherences (p=0.009). Several cardiovascular diseases (p-values between <0.001 and p=0.038), DMel type II, chronic kidney disease and previous cataract-surgery were associated with peripheral adherences (p=0.004; p=0.020 and p<0.001 respectively). Furthermore, pseudophakic donor eyes presented a higher degree of fragility of the graft (p<0.001). Age was a significant risk factor for difficult preparation (p<0.001). The staining of the graft was poorer in donors with chronic kidney disease (p=0.037). Conclusion: Donor diabetes mellitus type 2, heart failure, previous cataract surgery, chronic kidney disease and age are associated with a difficult DMEK graft preparation. For every one-year increment in donor age, the odds of having very difficult preparation were increased by 3%. Also, chronic kidney disease predisposes to a poor tissue staining with trypan blue during preparation.

Management of corneal melting after collagen cross-linking for keratoconus: a case report and a review of the literature.

PURPOSE: We describe the management of a case of severe corneal melting after corneal cross-linking (CXL) treated with a staged approach using a conjunctival flap followed by deep anterior lamellar keratoplasty (DALK). METHODS: A 12-year-old male developed severe corneal melting with pending perforation after an accelerated epithelium-off CXL protocol. We initially treated the patient with a conjunctival flap to prevent perforation. Three months later, we performed DALK to restore vision. RESULTS: Conjunctival flap surgery allowed us to avoid corneal perforation and penetrating keratoplasty (PK) à chaud. Once the inflammation had resolved, we recessed the conjunctiva and performed DALK for optical purposes. Twelve months later, the graft was clear and the corrected visual acuity was 20/25 (Snellen). No complications occurred after surgery. CONCLUSIONS: Although CXL is considered a safe procedure, in rare cases it can lead to serious complications, such as corneal haze, infectious and non-infectious keratitis, stromal melting and perforation. Corneal melting and perforation are usually managed by emergency PK. Herein we suggest a staged approach involving an emergency conjunctival flap followed by DALK at a later time that allowed us to avoid PK à chaud.

Pediatric corneal transplantation: techniques, challenges, and outcomes.

Pediatric corneal transplant is a highly demanding and technically challenging procedure for the cornea surgeon in today's era. These cases pose unique challenges in clinical and surgical management. The indications of pediatric corneal transplant can be therapeutic, tectonic, optical, and cosmetic. Pediatric patients undergoing corneal transplants are at a high risk of graft infection, failure, rejection, dehiscence, and amblyopia due to young age, robust immune system, increased incidence of trauma, and compliance issues. The other factors contributing to graft failure can be allograft rejection, secondary glaucoma, corneal vascularization, multiple surgeries, vitreous prolapse, and lack of treatment compliance. A successful corneal transplant in children depends on meticulous preoperative evaluation, uneventful surgery, the expertise of a corneal surgeon, and regular and timely postoperative follow-up. Therapeutic and optical penetrating keratoplasty are the most commonly performed transplants in children. However, with the advancements in surgical technique and management protocol, the current focus has shifted toward lamellar keratoplasty. Lamellar keratoplasty offers early visual recovery and potentially fewer complications. Visual rehabilitation through corneal transplant in otherwise blind eyes can be a boon for the children. Recently, keratoprostheses have been promising in children with multiple graft failures. The current review gives insights into epidemiology, etiology, indications, clinical characteristics, investigations, management options, recent advances, and the future of pediatric corneal transplants. As surgical techniques continue to grow and comprehension of pediatric corneal transplants is improving, we can safeguard these eyes with the best possible anatomical and functional outcomes.

Pseudomonas Keratitis: From Diagnosis to Successful Deep Anterior Lamellar Keratoplasty.

Pseudomonas keratitis is an aggressive form of bacterial keratitis that can have devastating consequences, such as corneal perforation, if not promptly identified and appropriately managed. The aim of this case report is to highlight key clinical features of Pseudomonas keratitis and evaluate the initial and long-term management options for this condition. We report a case of a 32-year-old female who presented with a large corneal abscess and hypopyon following contact lens wear. Corneal cultures confirmed Pseudomonas as the causative organism and she was treated with topical levofloxacin and gentamycin. Following sterilisation of the corneal ulcer, the patient was left with deep stromal scarring, peripheral corneal thinning as well as four-quadrant deep corneal vascularisation. She was listed for deep anterior lamellar keratoplasty surgery to clear her visual axis. We highlight some of the challenges that were faced both intra-operatively and post-operatively and how they were managed.

Sutureless lamellar keratoplasty with lenticule from small incision lenticule extraction for treating limbal dermoid: A case report.

The present study reports the case of a superficial limbal dermoid surgically treated without suture by using a new technique of lamellar keratoplasty with allogenic lenticule from small incision lenticule extraction. The limbal lesion area was circumscribed by a trephine marker and lamellae were peeled off the anterior corneal stroma and sclera. After excision of the dermoid, the liquid on the bed was dried as much as possible and an appropriate stromal lenticule was attached to the implant bed without fibrin glue or suture. A bandage contact lens was applied to fix the graft. During postoperative follow-ups, the anterior segment optical coherence tomography, corneal refractive power, corneal topography and best-corrected visual acuity were examined to evaluate the surgical results. On the first day after the operation, the patient reported tearing and pain at the site. At one week after the operation, the patient reported no discomfort and conjunctival sutures were removed. At one month after the operation, the thickness of the lesion area was similar to that of the adjacent cornea, and the corneal curvature and refractive power of the lesion area were higher than that of the adjacent cornea. At three months after the operation, the patient was satisfied with the cosmetic outcome and no sign of corneal neovascularization, graft rejection or pseudo-pterygium formation was observed. The astigmatic error remained at 2.50 D. The present case provides insights into a potential treatment option for patients who need lamellar keratoplasty and may provide its benefit in contrast to conventional lamellar keratoplasty.

Suture-related complications after deep anterior lamellar keratoplasty for keratoconus.

PURPOSE: The purpose of this study is to determine the incidence of suture-related complications, their risk factors, and effects on the clinical outcomes after deep anterior lamellar keratoplasty (DALK) for keratoconus. METHODS: In this retrospective, comparative, interventional study, the records of consecutive patients with keratoconus who underwent DALK were reviewed for suture-related complications. Univariate analyses were used to identify risk factors for suture complications. We compared groups with and without suture-related complications to evaluate the effects of these complications on clinical outcomes after DALK. RESULTS: Of the 633 DALKs, 438 eyes (69.2%) developed suture complications including loose sutures (32.7%), spontaneous suture rupture (30%), sterile suture abscesses (22.8%), suture tract vascularization (16.4%), suture erosion (10.3%), and suture cheese wiring (6.8%). Vernal keratoconjunctivitis increased the incidence of sterile suture infiltration, premature suture loosening, and suture tract vascularization. Loose suture was observed more commonly in larger graft size, while spontaneous suture rupture was associated with late suture removal. There was no statistically significant difference in postoperative outcomes including visual acuity, refraction, graft rejection, and failure in eyes with and without suture complications. However, suture-related complications were directly associated with sight-threatening ocular morbidities, including graft rejection (39 eyes), ulcer (1 eye), and failure (2 eyes). CONCLUSION: Suture-related complications frequently occurred after DALK for keratoconus. Ocular surface inflammation, large grafts, and late suture removal increased the risk of suture-related complications. While these complications had no negative impact on clinical outcomes in the majority of cases, some of them led to sight-threatening morbidity, underlining the importance of early diagnosis and treatment.

Deep Anterior Lamellar Keratoplasty Using Dehydrated versus Standard Organ Culture-Stored Donor Corneas: Prospective Randomized Trial.

PURPOSE: To compare the outcomes of deep anterior lamellar keratoplasty (DALK) using dehydrated versus standard organ culture-stored donor corneas for eyes with keratoconus. DESIGN: Prospective, randomized, single-center trial conducted in Italy. PARTICIPANTS: Adult patients (age ≥ 18 years) with keratoconus scheduled for elective DALK. METHODS: Patients undergoing successful type 1 bubble pneumatic dissection using a standard DALK technique were randomized during surgery to receive either dehydrated (n = 30) or standard organ culture-stored (n = 30) donor corneas. MAIN OUTCOME MEASURES: The primary study outcome was best spectacle-corrected visual acuity (BSCVA) 12 months after surgery. Secondary outcomes were refractive astigmatism (RA), endothelial cell density (ECD), and complication rates. RESULTS: Postoperative BSCVA did not significantly differ between groups at both time points: mean difference at 6 months was 0.030 logarithm of the minimum angle of resolution (logMAR; 95% confidence interval [CI], -0.53 to 0.10 logMAR; P = 0.471) and at 12 months was -0.013 logMAR (95% CI, -0.10 to 0.08 logMAR; P = 0.764). No significant differences between groups were observed in terms of postoperative RA and ECD at all time points. In the first 3 days after DALK, an epithelial defect was present in 10 patients (33%) in the organ culture cornea group and in 29 patients (97%) in the dehydrated cornea group. Complete re-epithelialization was achieved by day 7 in all patients (100%) in both groups. CONCLUSIONS: The study provides evidence that the use of dehydrated corneas is noninferior to the use of standard organ culture donor corneas for DALK. Corneal tissue dehydration represents a viable solution that can allow long-term cornea preservation and avoid wastage of unused corneas. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Manually prepared lamellae for Descemet stripping endothelial keratoplasty (Pachy-DSEK): comparison of four dissection depths / Lamelas manualmente dissecadas para transplante endotelial de córnea (Pachy-DSEK): comparação entre quatro profundidades de dissecção

ABSTRACT Purpose: This study aimed to compare four depths of manual dissection for the preparation of Descemet stripping endothelial keratoplasty lamellae. Methods: Eye bank corneas were randomized into four groups according to dissection depths: Pachy-100 (incision depth = central corneal thickness-safety margin of 100 µm), Pachy-50 (safety margin of 50 µm), Pachy-0 (no safety margin), and Pachy+50 (incision depth = central corneal thickness + 50 µm). All endothelial lamellae were prepared using a standardized method of manual dissection (Pachy-DSEK). The central, paracentral (3.0-mm zone), and peripheral (6.0-mm zone) lamella thicknesses and incision depths were measured by optical coherence tomography. The 3.0-mm and 6.0-mm zone central-to-peripheral thickness ratios were calculated. Results: Endothelial perforation occurred only in the Pachy+50 group (n=3, 30%). Central lamella's thickness in Pachy-100, Pachy-50, Pachy-0, and Pachy+50 groups measured 185 ± 42 µm, 122 ± 29 µm, 114 ± 29 µm, and 58 ± 31 µm, respectively (p<0.001). The overall 3.0- and 6.0-mm C/P ratios were 0.97 ± 0.06 and 0.92 ± 0.14, respectively. Preoperative donor characteristics were not correlated with most thickness outcomes. The planned incision depth correlated significantly with most lamella's thickness parameters (p<0.001). The overall thickness of the lamella negatively correlated with the planned incision depth (p<0.001, r=-0.580). The best outcome was found in the Pachy-0 group, as 75% of the lamellae measured <130 µm and there was no endothelial perforation. Conclusions: By using a standardized method of dissection, most manually prepared lamellae presented a planar shape. Setting the incision depth to the central corneal thickness did not result in endothelial perforation and a high percentage of ultrathin lamellae was achieved.

RESUMO Objetivo: Comparar quatro profundidades de dissecção manual usadas no preparo de lamelas para transplante endotelial. Métodos: Córneas humanas de treinamento disponibilizadas foram randomizadas em quatro grupos: Pachy-100 (profundidade de incisão = espessura corneana central - margem de segurança de 100 µm), Pachy-50 (margem de segurança de 50 µm), Pachy-0 (sem margem de segurança) e Pachy+50 (profundidade de incisão = espessura corneana central + 50 µm). Todas as lamelas foram dissecadas através um método padronizado e já publicado (Pachy-DSEK). As espessuras das lamelas (centro, zona de 3,0mm e zona de 6,0mm) foram medidas com tomografia de coerência óptica. A razão de espessura centro-periferia foi calculada aos 3,0 e 6,0 mm de diâmetro. Resultados: Perfuração endotelial ocorreu apenas no grupo Pachy+50 (n=3, 30%). A espessura central da lamela nos grupos Pachy-100, Pachy-50, Pachy-0 e Pachy+50 foi de 185 ± 42 µm, 122 ± 29 µm, 114 ± 29 µm, e 58 ± 31 µm, respectivamente (p<0,001). As razões C/P aos 3,0 e 6,0 mm foram de 0,97 ± 0,06 e 0,92 ± 0,14, respectivamente. Os parâmetros de características do doador não se correlacionaram com os resultados de espessura de lamela. A profundidade planejada de incisão se correlacionou com a maioria dos parâmetros de espessura de lamela (p<0,001). A espessura de lamela se correlacionou negativamente com a profundidade planejada da incisão (p<0.001, r=-0,580). O melhor resultado foi observado no grupo Pachy-0, em que 75% das lamelas mediram abaixo de 130 µm e não houve perfuração endotelial. Conclusão: Através de um método padronizado de dissecção, a maioria das lamelas endoteliais apresentou uma configuração planar. O planejamento de profundidade de incisão igual à espessura corneana central resultou em alta porcentagem de lamelas ultrafinas sem ocorrência de perfuração.

Advantages of femtosecond laser in various corneal transplantation procedures: A narrative literature review.

The ability of the femtosecond laser (FSL) to create tissue incisions at desired depth and location with minimal collateral damage to surrounding tissue may offer potential advantages for corneal transplantation surgery. FSL may enable the precise and accurate preparation of both donor and recipient tissue, which can potentially result in enhanced wound integrity, facilitation of wound healing, and improved visual outcomes. Many studies have suggested that FSL may be a viable option in various corneal transplantation procedures, such as, penetrating keratoplasty, anterior lamellar keratoplasty, endothelial keratoplasty, and novel techniques, including Bowman layer transplantation and stromal lenticule addition keratoplasty. In this review, the author presents a brief overview on the application of FSL in various corneal transplantation procedures and discusses the results of studies regarding the safety and efficacy of FSL-assisted corneal transplantation procedures.

Femtosecond laser applications in corneal surgery.

Femtosecond laser (FSL) applications in corneal surgery have increased since its inception. Corneal surgery has undergone a tremendous transformation thanks to the introduction of FSL technology. This laser makes precise, three-dimensional incisions while causing minimal damage to surrounding tissue. This review updates and summarizes current and upcoming FSL applications in corneal surgery, current commercially available FSL, and its respective applications. Refractive surgery applications include laser in-situ keratomileusis flaps, refractive corneal lenticule extraction such as small incision lenticule extraction, astigmatic keratotomy, intracorneal ring segments tunnels for keratoconus including corneal allogenic intrastromal ring segments, and presbyopia treatments with intrastromal pockets for corneal inlays and intrastromal incisions (INTRACOR). Keratoplasty applications include penetrating keratoplasty trephination; superficial and deep anterior lamellar keratoplasty trephination, lamellar dissection, and tunnel creation; posterior lamellar keratoplasty donor and recipient preparation; Bowman layer transplantation donor, and recipient preparation; and stromal keratophakia. Other applications include conjunctival graft preparation in pterygium surgery, and keratopigmentation (corneal tattooing). FSL is a surgical instrument widely used in corneal surgery because it improves reproducibility and safety in many procedures.

Femtosecond laser-assisted corneal transplantation.

Corneal transplantation is the only surgical option to improve symptoms and vision in patients with severe corneal opacification. With the evolution and development of keratoplasty techniques, corneal surgeons can perform customized keratoplasty, with complex graft-host junctions to promote wound healing and accelerate visual rehabilitation. Femtosecond laser (FSL) enable customization of the thickness and shape of the graft has been used for trephination of both donor and recipient corneas and for creating special wound configurations. In this review, we have summarized the intraoperative application and postoperative outcomes of FSL-assisted keratoplasties, including penetrating keratoplasty, anterior lamellar keratoplasty (ALK), deep ALK, Descemet stripping automated endothelial keratoplasty (EK), and Descemet membrane EK. Although FSL allows for the customization and precision in keratoplasty, several concerns, such as cost-effectiveness, limit its wider clinical adoption. Hence, more work is required to weigh the advantages and limitations of the FSL applications in corneal transplantation.