On the Possibility of Femto-DALK Performing in Open Globe Eye Injury with Corneal Localisation

Lamellar Keratoplasty

'Big Bubble' deep anterior lamellar keratoplasty (DALK) is becoming an accepted corneal transplantation technique for keratoconus and other anterior stromal corneal pathologies that spare the Descemet's membrane (DM) and endothelium. However, it is not always possible to conclusively recognise formation and identification of the 'Big Bubble'. We describe the surgical technique of DALK called 'Double Bubble' technique that allows the surgeon to definitely and immediately identify the formation of an adequate big bubble. DALK was performed using the 'Double Bubble' technique in twelve eyes of twelve patients with corneal stromal pathologies (keratoconus, 9 eyes; macular corneal dystrophy, 2 eyes; postinfectious keratitis corneal stromal scar, 1 eye) at the Royal Victorian Eye and Ear Hospital, Melbourne. Big bubble was successfully formed in 10 eyes. Maximum-depth deep lamellar keratoplasty was performed in two eyes. There were no instances of intraoperative perforation of the DM. All grafts were clear at last follow-up. Best-corrected visual acuity of≥20/40 was achieved in all the cases at last follow-up (6-12months). 'Double Bubble' DALK helps in identification of the big bubble and has the potential to increase the success of standard 'Big Bubble' DALK in patients with corneal stromal pathologies sparing the DM and endothelium.

Purpose. To determine the optimal channel parameters in the deep layers of the corneal stroma when performing deep anterior lamellar keratoplasty (DALK), providing the maximum frequency of air bubble formation, under the control of intraoperative optical coherence tomography. Material and methods. The study was performed at 30 patients (30 eyes) with a diagnosis of stage III keratoconus. The average age of patients is 31±7 years. All patients were divided into groups consisting of 10 patients, depending on the choice of the topographic orientation of the channel for pneumodissection in the deep layers of the corneal stroma when performing DALK: 1st group – the channel is located towards the center of the cornea; 2nd group – the channel is located paracentral to the temporal side; 3rd group – the channel is located paracentral to the nasal side. In all cases, DALK was performed with a femtosecond laser Femto LDV Z8 (Ziemer, Switzerland). The length of the formed femto channels were variable and amounted to 1.0, 1.5, 2.0, 2.5 and 3.0 mm in each group. Results. The use of intraoperative OCT demonstrated that in all 30 cases the depth of the channel for pneumodissection corresponded to preoperative calculations and amounted to 97±5µm to DM. It was found that the bedding of the channel at a distance of 100µm to the descemet membrane (DM) and its paracentral orientation is characterized by a greater frequency of formation of the «Big Bubble» in comparison with its central orientation: 3rd group – 90% and 2nd group – 80% against 1st group – 60% of cases. The study of the effect of the length of the channel for pneumodissection on the ease of formation of the "Big Bubble" demonstrated that more attempts are required to inject sterile air when channels of 2.0, 2.5, 3.0 mm being used than with short channels of 1.0, and 1, 5 mm (average 3 attempts versus 1.5 attempts, respectively). Conclusion. The paracentral orientation of the location of the channel for pneumodissection is accompanied by a higher percentage of formation of the "Big Bubble" than the central location of the channel. Manual extension of femtochannels having length of 1.0, 1.5 mm, directly with a microsurgical spatula 30G followed by inserting a metal cannula into the channel minimizes the number of attempts to inject sterile air, that facilitates the formation of the "Big Bubble". Performing DALK applying the function of intraoperative OCT allows to control the accuracy of all stages of the operation, including the stage of formation of a large air bubble. Performing DALK with the applying of the function of intraoperative OCT allows to control the accuracy of all stages of the operation, including the stage of formation of a large air bubble. Key words: deep anterior lamellar keratoplasty, Big Bubble, channel for pneumodissection

Purpose:To describe a quick and simple “small-bubble” technique to immediately determine the success of attaining complete Descemet’s membrane (DM) separation from corneal stroma through Anwar’s “big-bubble” technique of deep anterior...

Comment On: Predictors of Bubble Formation and Type Obtained With Pneumatic Dissection During Deep Anterior Lamellar Keratoplasty in Keratoconus

Evaluation of outcomes of big-bubble deep anterior lamellar keratoplasty in cases with post-keratitis and post-traumatic corneal scars. Interventional case series. Patients with corneal stromal scarring secondary to healed infectious keratitis or trauma were recruited from the Corneal Clinic of the M. M. Joshi Eye Institute, Karnataka, India between August 2007 and December 2009. All patients underwent big-bubble deep anterior lamellar keratoplasty surgery. Best-corrected visual acuity, as well as intra- and postoperative complications. Big-bubble deep anterior lamellar keratoplasty was performed in 36 patients (25 males, 11 females) with post-infectious keratitis (n = 22) and post-traumatic (n = 14) corneal stromal scars sparing the Descemet's membrane and endothelium. Mean age was 39.7 ± 11.3 years (range: 22-58 years). Although a big bubble was achieved in all eyes (100%), intraoperative perforation of the Descemet's membrane occurred in six eyes (16%) during stromal dissection. Two cases required conversion to penetrating keratoplasty. A double anterior chamber occurred in the immediate postoperative period in three cases (8.3%). Raised intraocular pressure was seen in one eye. Mean preoperative best-corrected visual acuity (0.03 ± 0.04) improved significantly at the end of 6 months follow-up postoperatively (0.43 ± 0.20; P < 0.01, Wilcoxon signed-ranks test). Corneal stromal graft rejection was noted in two cases (5.5%) during the first 3 months after surgery. Graft failure occurred in two cases (5.5%). Deep anterior lamellar keratoplasty using the big-bubble technique is a viable option in cases with post-infectious keratitis and post-traumatic corneal stromal scarring with normal Descemet's membrane and endothelium.

AimThe most popular technique for deep anterior lamellar keratoplasty (DALK) is the ‘big bubble’ (BB) technique wherein air is injected in the cornea to create a bubble that separates Descemet's...

ABSTRACTPurpose: To determine the factors associated with the formation of different types of big bubble (BB) during DALK.Methods: In this retrospective study, 322 consecutive eyes of 307 patients with corneal stromal disorders who underwent DALK between January 2014 and June 2017 were included. Age, sex, corneal pathology, visual acuity, corneal curvature, corneal thickness, and adverse events were recorded. The main outcome measure was the success of BB formation with respect to the corneal pathology.Results: Type-1 BB was achieved in 147 eyes (45.7%), whereas type-2 BB was formed in 109 eyes (33.9%). The overall success rate of BB formation was 82.9%. Type-1 BB formation in keratoconus patients was significantly higher than type-2 BB (83.8% vs 2.6%, p < 0.001). In contrast, type-2 BB formation was significantly higher than type-1 BB (61.0% vs 15.6%, p < 0.001) in patients with corneal scars. Type-1 BB was more likely to be seen in patients with superficial corneal scarring, granular, and lattice dystrophies, while corneas with deep scarring and macular dystrophy had more type-2 BB. The type of bubble was not associated with age and gender of the patients.Conclusions: The overall success of big-bubble (BB) deep anterior lamellar keratoplasty (DALK) depends on the preoperative corneal pathology. Type −1 BB was more commonly seen in keratoconus patients whereas type-2 BB was observed in patients with deep corneal scars and other corneal pathologies affecting deeper layers of corneal stroma.

ABSTRACTAim: To describe the “small bubble” technique to immediately determine the success of attaining complete Descemet’s membrane (DM) separation from corneal stroma via Anwar’s “big bubble” technique of deep anterior...

A case report. A 32-year-old male with previous hydrops developed severe corneal scarring with a break in DM visible on OCT scanning. A modified DALK procedure was perform consisting of a 400µm, 8.5mm Anterior lamellar cap with a 4.5mm posterior lamellar disc, denuded of endothelial cells and containing a DM skirt.Initially, manual dissection of the and anterior 400µm of corneal stroma was performed using a modified Melles technique. The residual posterior lamellar was assessed and found to have significant residual scarring. A central 4mm optical window was performed through the posterior lamellar over the visual axis.The donor tissue was cut using a 350µm microkeratome head. The anterior cap was trephined to 8.5mm and set aside. The posterior lamellar was placed in a punch block, and the endothelial was removed using a silicone tipped cannula. The removal of endothelial cells was confirmed using trypan blue dye. A posterior lamellar graft with a 4.0mm stromal bed and a 4.5mm DM skirt was fashion using a peeling and double punch technique. The posterior lamellar graft was inserted into the optical window such that the DM skirt provided a bridge to the donor corneal endothelium. The anterior cap was sutured with a double continuous suture of 10-0 monofilament nylon. An inferior peripheral iridotomy was created, and an air bubble filling the anterior chamber was left at the end of the case. The preoperative visual acuity (VA) was hand movements. Full attachment of the posterior lamellar was seen at all time-points from week one onwards. Central corneal pachymetry continued to reduce for 12 weeks. One year after the operation, with sutures in, the best spectacle-corrected VA was 6/12. The corneal graft was clear, and no rejection episodes occurred. Endothelial cell repopulation of the donor DM could be observed with specular microscopy. The presence of DM promotes endothelial migration and healing. Modifications to traditional DALK surgery, in which DM is used to promote endothelial healing, are a viable alternative to penetrating keratoplasty. This method eliminates the risk of allograft endothelial rejection and allows a 'regenerative' for DALK to be used, offering a new modality of treatment in patients with healthy reserves of endothelial cells and deep posterior lamellar scarring.

PurposeTo define optical coherence tomography (OCT) characteristics of type-1, type-2, and mixed big bubbles (BB) seen in deep anterior lamellar keratoplasty.MethodsHuman sclero-corneal discs were obtained from UK (30) and Canada (16) eye banks. Air was injected into corneal stroma until a BB formed. UK samples were fixed in formalin before scanning with Fourier-domain (FD-OCT). One pair of each type of BB was scanned fresh. All BB obtained from Canada were scanned fresh with time-domain (TD-OCT). For each OCT machine used, type-1 BB from which Descemets membrane (DM) was partially peeled, were also scanned. The morphological characteristics of the scans were studied.ResultsFD-OCT of the posterior wall of type-1 (Dua's layer (DL) with DM) and type-2 BB (DM alone) both revealed a double-contour hyper-reflective curvilinear image with a hypo-reflective zone in between. The anterior line of type-2 BB was thinner than that seen with type-1 BB. In mixed BB, FD-OCT showed two separate curvilinear images. The anterior image was a single hyper-reflective line (DL), whereas the posterior image, representing the posterior wall of type-2 BB (DM) was made of two hyper-reflective lines with a dark space in between. TD-OCT images were similar with less defined component lines, but the entire extent of the BB could be visualised.ConclusionOn OCT examination the DM and DL present distinct features, which can help identify type-1, type-2, and mixed BB. These characteristics will help corneal surgeons interpret intraoperative OCT during lamellar corneal surgery.

PurposeTo study the dynamics of big bubble (BB) formation in eyes with advanced keratoconus (KC) during deep anterior lamellar keratoplasty (DALK).MethodsA retrospective review of medical records and videos of DALK surgeries performed during the period from January 2013 to December 2019 on keratoconic eyes. Eyes with formed BB, in the presence of a relatively clear stroma, were included. We studied the following parameters the location of BB commencement, duration from the start of the bubble until complete formation, and the pattern of air passage during the formation process.ResultsA total of 37 eyes met the inclusion criteria. Type 1 BB was formed in 22 eyes with a mean formation time of 1.9 ± 1.1 seconds and a mean bubble diameter of 7.6 ± 1.1 mm. Type 1 BB started in the center as a small dome expanding centrifugally with preceding localized stromal whitening in 19 eyes and without whitening in three eyes. Type 2 BB was formed in 14 eyes with a mean formation time of 0.3 ± 0.12 seconds and a mean bubble diameter of 7.4 ± 1.8 mm. Type 2 BB started in the center in 13 eyes and the mid periphery in one eye, through either direct access to the plane between Descemet’s membrane and the pre-Descemet’s layer in six eyes, or preceded by a small intrastromal bubble in eight eyes. Mixed bubble was observed in one eye, which started as a small central Type 1 BB followed by the rapid formation of a Type 2 BB.ConclusionEyes with KC are associated with central commencements of both Type 1 and Type 2 BB during DALK. Duration of BB formation was significantly faster in Type 2 BB, with most starting as a small intrastromal bubble before air gain access to the plane between DM and stroma.

To analyze the reasons for intraoperative perforation of Descemet's membrane during deep anterior lamellar keratoplasty (DALK) during the learning curve. DALK was attempted in 35 eyes of 33 patients with pathologies involving the corneal stroma and sparing of Descemet's membrane (DM), including patients with keratoconus, corneal stromal dystrophies and healed keratitis. The surgical plan included complete removal of the corneal stroma using the "big bubble" technique for exposing Descemet's membrane followed by grafting of a full-thickness corneal stromal lenticule. DALK was converted into full-thickness penetrating keratoplasty in eight eyes (23%), which included patients with keratoconus (n = 6), macular corneal dystrophy (n = 1) and healed keratitis (n = 1). Main reasons for conversion were perforation of the DM due to excessive air injection (four eyes) and improper surgical maneuvers (three eyes). One case had deposits on Descemet's membrane upon exposure of the DM. A successful penetrating keratoplasty could be performed in all eight eyes. During the learning curve, excessive air injection and inappropriate surgical maneuvers may complicate a DALK resulting in conversion to penetrating keratoplasty.

To describe the feasibility and outcomes of intraoperative optical coherence tomography (OCT)-guided, femtosecond laser-assisted deep anterior lamellar keratoplasty in which the lamellar and tunnel cuts were completed by laser. The Ziemer Z8 system was used to scan the corneas intraoperatively and guide the stromal lamellar and tunnel cuts created by the laser. Thirty porcine eyes and 3 human cadaver globes were used to evaluate the accuracy of laser-created intrastromal tunnels and the feasibility of achieving big-bubble pneumatic dissection. The tunnel distance above the Descemet membrane (Dt-dm) was set at 100 and 130 μm, and the accuracy of laser cut was assessed by anterior segment OCT and histological sections. Fourteen patients with keratoconus or corneal scars were then included to evaluate the clinical outcomes. The deviation from the targeted Dt-dm was 5.5% to 8.6% and 0.7% to 9.8% for the 100 and 130 μm groups, respectively. The achieved thickness had a significantly and positively strong correlation with the targeted thickness (r = 0.86; P < 0.001). In all cases, the anterior stromal lamella was removed without difficulty, except in the patients with corneal scars in whom some remaining stromal fiber attachments were observed. A type 1 big bubble was successfully achieved in all patients. We present the accuracy and clinical outcomes of femtosecond laser-assisted, intraoperative OCT-guided deep anterior lamellar keratoplasty, in which controlled lamellar and tunnel cuts at desired depths were performed by laser in one step, and a successful big bubble was achieved.

To report the achievement rate of bare Descemet membrane (DM) dissection with the help of microbubble incision technique in eyes with failed big bubble formation and to investigate the mechanism of the microbubble rescue technique through ex vivo imaging of human cadaver corneas. This retrospective clinical study included 80 eyes of 80 patients that underwent deep anterior lamellar keratoplasty (DALK). In 22/80 (27.5%) cases, big bubble dissection failed. After puncturing the microbubbles, viscodissection helped to achieve separation of DM from the remaining stroma. In addition, an ex vivo study with human cadaver cornea specimens, gross photography, and anterior segment optical coherence tomography imaging was accomplished ex vivo to explore the mechanism of this method. Microbubble dissection technique led to successful DALK in 19 of 22 cases of failed big bubble. Microperforation occurred in 3 eyes. Deep anterior lamellar keratoplasty was completed without any complications in 2 out of the 3 eyes with microperforation. In 1 eye, conversion to penetrating keratoplasty was required. Microbubble-guided viscodissection achieved 95.4% (21/22) success in exposing bare DM in failed big-bubble cases of DALK. Anterior segment optical coherence tomography imaging results of cadaver eyes showed where these microbubbles were concentrated and their related size. Microbubble-guided DALK should be considered an effective rescue technique in achieving bare DM in eyes with failed big bubble. Our ex vivo experiment illustrated the possible alterations in cornea anatomy during this technique.