Big-bubble Technique Research Articles

Long-term Outcomes of Deep Anterior Lamellar Keratoplasty in Macular Corneal Dystrophy—A Retrospective Analysis

Abstract Purpose: To study the long-term outcomes and complications in patients who underwent deep anterior lamellar keratoplasty (DALK) for macular corneal dystrophy (MCD). Methods: This is a retrospective analysis of all patients who underwent DALK in a tertiary eye care hospital in South India from 2011 to 2020. A total of 51 eyes of 33 patients were evaluated. All eyes underwent successful DALK by big bubble technique (32 eyes) or layer-by-layer dissection (19 eyes). Patients were followed up for 18 months to 9 years. Results: There was a significant improvement in vision (uncorrected and best-corrected visual acuity) post-DALK. The best corrected visual acuity after surgery was 0.3 logMAR (20/40) or better in 66.7% of operated eyes. Complications noted during surgery were intra-operative perforation. Post-operative complications include double AC, cataract, raised intraocular pressure, interface vessels and recurrence of the dystrophy. Conclusion: DALK is a safe and viable procedure for MCD management and gives good visual outcomes.

Diamond ophthalmic burr-assisted deep anterior lamellar keratoplasty – Case series

This case series presents a simple technique using the diamond ophthalmic burr (DOB) to perform successful deep anterior lamellar keratoplasty (DALK) in cases where the big-bubble technique is unsuitable or intraoperative Descemet membrane perforation occurs. Five patients underwent DOB-assisted DALK, and postoperative outcomes were evaluated, including best-corrected visual acuity, corneal astigmatism, residual host tissue thickness, and postoperative endothelial cell count. Manual corneal lamellar dissection was performed, followed by DOB-assisted pre-Descemet layer polishing and donor graft attachment using 16 (10-0) Monofilament Nylon sutures. The postoperative visual acuity significantly improved. DOB-assisted DALK is a viable alternative.

Application of intraoperative optical coherence tomography in deep lamellar keratoplasty

Objective: To evaluate the clinical application value of intraoperative optical coherence tomography (iOCT) in deep anterior lamellar keratoplasty (DALK) using the big-bubble technique to bare Descemet's membrane. Methods: Retrospective case series. Clinical data of 92 patients (92 eyes) with monocular stromal corneal diseases who underwent big-bubble DALK in the Eye Hospital of Shandong First Medical University from January 2020 to August 2021 were collected. There were 53 males and 39 females. The average age was (53.2±16.0) years old. All patients underwent iOCT scanning to determine the location and depth of the injection needle after initial removal of the corneal lesion, to observe the integrity of the recipient bed, Descemet's membrane, after complete lesion removal, and to observe the adhesion between the corneal graft and the recipient bed and check folds on the recipient bed after suturing of the corneal graft. The intraoperative perforation of Descemet's membrane, postoperative thickness of the cornea and the recipient bed, visual acuity, and corneal astigmatism were recorded. Results: By iOCT, the thickness of the recipient bed was found to be about 1/2 of the corneal thickness and relatively uniform in all directions in 62 eyes (67.4%), so the sterile air was injected from the center of the recipient bed to separate it from the stromal layer. In 30 eyes (32.6%) with an uneven thickness of the recipient bed, the sterile air was injected from the paracentral area of the recipient bed. Under the guidance of iOCT scanning, 89 eyes (96.7%) did not experience any perforation of Descemet's membrane during surgery. The Descemet's membrane folds in the central 5-mm area of the recipient bed was observed and flattened in 20 eyes with the assistance of iOCT scanning. The postoperative corneal thickness was (578.95±108.26) μm, and the recipient bed thickness was (36.06±23.11) μm. The best corrected visual acuity of all patients at 6 months after surgery was 0.57±0.25 logMAR, which was significantly better than that before surgery (1.61±1.27 logMAR; P<0.001). The average corneal astigmatism at 6 months after surgery was (2.72±2.44) diopters. Conclusions: The application of iOCT scanning in DALK surgery assisted by the big-bubble method can provide safe guidance for surgeons to adopt correct surgical procedures, decrease the risk of Descemet's membrane perforation, reduce the recipient bed folds, and facilitate corneal interlayer adhesion, thereby improving the visual prognosis.

Comparison of Deep Anterior Lamellar Keratoplasty and Penetrating Keratoplasty in Keratoconic Eyes With Previous Hydrops-Related Corneal Scar.

This study aimed to compare the outcomes of deep anterior lamellar keratoplasty (DALK) and penetrating keratoplasty (PK) procedures in keratoconic eyes with a previous hydrops-related corneal scar. In this retrospective study, the medical records of patients who had hydrops-related corneal scarring and underwent keratoplasty surgery were reviewed. Patients treated with DALK were classified as group 1, and patients treated with PK as group 2. Preoperative and postoperative best-corrected visual acuity, central corneal thickness, keratometry (K), and refractive error values of each group were recorded and compared. Seventy-eight eyes (41 in group 1 and 37 in group 2) were included in this study. The mean follow-up period of the patients was 37.7 ± 30.0 months in group 1 and 51.2 ± 29.4 months in group 2 ( P = 0.06). The preoperative and postoperative best-corrected visual acuity and central corneal thickness values were statistically similar in both groups (each P value >0.05). Keratometry values (K1 and mean keratometry) were significantly steeper in group 1 ( P1 = 0.02 and P2 = 0.03, respectively). Descemet membrane perforation was experienced in 7 (4 macroperforation and 3 microperforation; 15.6%) of 45 eyes that planned to perform DALK. These 4 eyes with macroperforation underwent PK and were excluded from the study. When all postoperative complications were assessed, although the total complication rate was 21% after DALK, it was 43% after PK ( P = 0.04). DALK with a big-bubble technique is a feasible surgery in eyes with corneal scarring due to previous hydrops and is comparable with PK in terms of visual and refractive outcomes. This study suggests that DALK, which is safer than PK with less postoperative complication rates, should be the primary surgical option to avoid serious complications in keratoconic eyes with hydrops-related corneal scarring.

Ex vivo demonstration of canine corneal pre-Descemet’s anatomy using pneumodissection as for the big bubble technique for deep anterior lamellar keratoplasty

The recent discovery and characterization of pre-Descemet’s layer (PDL; also termed the Dua’s layer or the Dua-Fine layer) has advanced the understanding of various posterior corneal pathologies and surgeries in human. This study aimed to characterize the ultrastructure of the posterior stroma and interfacial zone of Descemet’s membrane (DM) in canine eyes. Eighteen canine corneo-scleral discs were included. Intrastromal air injection resulted in the formation of type 1 big bubble (BB) in 73% (n = 11/15) of corneas, with a mean diameter of 11.0 ± 1.3 mm. No type 2 BB was created. Anterior segment optical coherence tomography, histology and transmission electron microscopy confirmed that the wall of BB was composed of DM, in contact with remaining stroma (canine PDL; cPDL). The cPDL was populated with keratocytes, of varying thickness of 16.2 ± 4.2 µm in close apposition to the DM, and composed of collagen bundles arranged in transverse, longitudinal and oblique directions. The interfacial zone, between DM and cPDL, showed fibril extension in all three directions, predominantly longitudinal. Irregular extensions of DM material into cPDL stroma were observed. No long-spaced collagen was detected. In conclusion, there exists a well-defined cleavage plane between the posterior stroma and cPDL, with similar but not identical characteristics as in humans, that is revealed by pneumodissection. This adds to our understanding of the anatomy of the posterior most canine cornea, which will have significant clinical impact on posterior corneal surgery and understanding of corneal pathology in dogs.

Elliptical deep anterior lamellar keratoplasty in severe Acanthamoeba keratitis.

Acanthamoeba keratitis (AK) is an intractable infection of the cornea. Penetrating keratoplasty is widely used for the management of severe AK but suffers from complications like graft rejection, endophthalmitis, and glaucoma. Herein, we aimed to describe the surgical technique and the results of elliptical deep anterior lamellar keratoplasty (eDALK) for the management of severe AK. In this retrospective case series, records of consecutive patients with AK poorly responsive to medical treatment who underwent eDALK from January 2012 to May 2020 were reviewed. The largest diameter of infiltration was ≥8 mm and did not involve the endothelium. The recipient bed was made by an elliptical trephine, and big bubble or wet-peeling technique was performed. Postoperative best spectacle-corrected visual acuity, endothelial cell density, corneal topographic data, and complications were evaluated. Thirteen eyes of thirteen patients (eight men and five women, 45.54 ± 11.78 years old) were included in this study. The mean follow-up interval was 21.31 ± 19.59 months (range, 12-82 months). At the last follow-up, the mean best spectacle-corrected visual acuity was 0.35 ± 0.27 logarithm of the minimum angle of resolution. The mean refractive and topographic astigmatism were - 3.21 ± 1.77 and 3.08 ± 1.14 D, respectively. Intraoperative perforation was encountered in one case and double anterior chambers occurred in two cases. One graft developed stromal rejection and one eye developed amoebic recurrence. eDALK can serve as the first-line surgical management of severe AK poorly responsive to medical treatment.

Comparison of visual outcomes, keratometric parameters and biomechanical profiles between deep anterior lamellar keratoplasty with big-bubble technique vs. Melles technique for keratoconus: a retrospective study

ObjectiveComparing results of two different DALK surgery techniques (big bubble vs. Melles) in patients with advanced keratoconus.Designa retrospective comparative clinical study.ParticipantsThis study conducted on 72 eyes of 72 participants.IntroductionThis study designed to compare the results of two different DALK surgery techniques (big bubble vs. Melles) in patients with advanced keratoconus.MethodThirty-seven eyes were treated using the big bubble DALK method, while 35 eyes were treated using the Melles approach. Uncorrected visual acuity (UCVA), best corrected spectacle visual acuity (BCSVA), manifest refraction, keratometric characteristics, contrast sensitivity, corneal aberrations, corneal biomechanical characteristics, and endothelial cell profile are the outcome measurements.ResultsMean UCVA in big bubble group was 0.61 ± 25 LogMAR and in Melles group was 0.89 ± 0.41 LogMAR (p-value 0.043). Mean BCSVA in big bubble group (0.18 ± 0.12 Log MAR) was significantly better than Melles group (0.35 ± 0.16 Log MAR). Mean of sphere and cylinder refraction showed no significant difference between two groups. Comparing the endothelial cell profile, corneal aberrations, corneal biomechanical properties and keratometry had no significantdifferences. Contrast sensitivity reported as modulation transfer function (MTF) showed higher values in big bubble group and differences with Melles group weresignificant. Results of point spread function (PSF) in big bubble group had superiority to Melles group with considerable statistical P value of 0.023.ConclusionWhen opposed to the Melles approach, the big bubble technique generates a smooth interface with less stromal residue, which results in higher visual quality and contrast sensitivity.

Spherical equivalent (SE) outcomes after suture manipulation in post operative deep anterior lamellar keratoplasty (DALK) patients

Introduction: Deep anterior lamellar keratoplasty (DALK) is a successful intervention among other surgical options for treating keratoconus. However after DALK surgery there are other post operative refractive morbidities which affects patient satisfaction. This study analyzes how suture manipulation in post-DALK patients affects the Spherical Equivalent (SE) outcome and whether it’s adhering to the corneal coupling concept.Objective: To determine the pre and post suture manipulations adhered to the concept of corneal coupling and the effect of timing of suture removal on the Spherical Equivalent (SE) outcome.Methodology: This retrospective study involved 40 manipulations in 18 patients who underwent DALK from 2020 to 2021 for keratoconus. All the Surgeries performed by single Consultant Eye Surgeon using big bubble (BB) technique. All grafts anchored using 16 interrupted 10/0 nylon sutures. Data was obtained from hospital and patient records. Objective and Subjective SE, Mean K readings were monitored.Conclusion: Pre and Post suture manipulations adhered to the corneal coupling and there was no statistically significant SE change. Furthermore, it was observed that delaying the removal of sutures resulted in minimal changes in the SE.

Ex Vivo Evaluation of a Pressure-Sensitive Device to Aid Big Bubble Intrastromal Dissection in Deep Anterior Lamellar Keratoplasty.

To develop and perform ex vivo testing for a device designed for semiquantitative determination of intracorneal dissection depth during big bubble (BB) deep anterior lamellar keratoplasty. A prototype device connected to a syringe and cannula was designed to determine depth of intrastromal placement based on air rebound pressure emitted by a software controlled generator. Ex vivo testing of the device was conducted on human corneas mounted on an artificial anterior chamber in three experiments: (1) cannula purposely introduced at different depths measured with anterior segment optical coherence tomography, (2) cannula introduced as per the BB technique, and (3) simulation of the BB technique guided by the device. A positive pressure differential and successful BB were observed only when the cannula was positioned within 150 microns from the endothelial plane. In all successful BB cases (21/40), a repeatable increase in tissue rebound pressure was detected, which was not recorded in unsuccessful cases. The device was able to signal to the surgeon correct placement of the cannula (successful BB) in 16 of 17 cases and incorrect placement of the cannula (unsuccessful BB) in 8 of 8 cases (94.1% sensitivity, 100% specificity). In our ex vivo model, this novel medical device could reliably signal cannula positioning in the deep stroma for effective pneumatic dissection and possibly aid technical execution of BB deep anterior lamellar keratoplasty. A medical device that standardizes big bubble deep anterior lamellar keratoplasty could increase the overall success rate of the surgical procedure and aid popularization of deep anterior lamellar keratoplasty.

Inadvertent Viscoelastic Separation of the Pre-Descemet (Dua) Layer in Deep Anterior Lamellar Keratoplasty With Structural Features Revealed by Polarization Microscopy.

Deep anterior lamellar keratoplasty (DALK) is a corneal transplant technique that removes the host stroma down to either the pre-Descemet (Dua) layer or Descemet membrane. It is most common for the big bubble technique to create a cleavage plane between the posterior stroma and the pre-Descemet layer. This is advantageous because the pre-Descemet layer has been found to be much stronger than Descemet membrane, and makes the procedure easier to perform. In this report, we present an uncommon viscoelastic-related complication of DALK that resulted in excising the pre-Descemet layer and allowing it to be studied using polarization microscopy. DALK was performed using a standard big bubble technique. Postoperatively, a double anterior chamber was found to have been created by the inadvertent passage of an ophthalmic viscoelastic device (OVD) through the pre-Descemet layer. This resulted in the OVD being trapped between the pre-Descemet layer and Descemet membrane. The pre-Descemet layer was then resected in a subsequent operation. The pre-Descemet layer and posterior stroma were studied by polarization microscopy using Sirius Red histochemical staining to elucidate the orientation of the collagen fibers. The pre-Descemet layer is composed of lamellar arrays of collagen that have consistent polarization properties within each layer but show variable polarization of the strands, indicative of anisotropic strand orientation. The degree of variable polarization of the pre-Descemet layer is distinct from the overlying posterior stroma. Injecting an OVD into a big bubble in DALK may result in it being trapped between the pre-Descemet layer and Descemet membrane. The pre-Descemet layer shows alternating layers of varying polarization of collagen. This anisotropic structure helps explain the basis for the additional strength that the pre-Descemet layer is known to have.

Corneal aberrations, densitometry on scheimpflug imaging, and visual acuity after deep anterior lamellar keratoplasty.

To evaluate visual acuity, corneal aberrations, and densitometry post deep anterior lamellar keratoplasty (DALK). Twenty-five eyes of 25 patients who underwent DALK for corneal stromal diseases with normal endothelium were enrolled in a prospective interventional study. Evaluation for corneal aberrations and densitometry postoperatively was performed using Scheimpflug imaging at 6 months. Anterior Segment Optical Coherence Tomography (ASOCT) was done for host-graft morphology. Correlation analysis of postoperative best-corrected visual acuity with corneal aberrations and corneal densitometry (CD) was performed. Big bubble deep anterior lamellar keratoplasty (BB-DALK) was successful in 18 patients, while 7 eyes underwent manual dissection due to failed BB (Big Bubble) technique. The mean BSCVA was 1.35 ± 0.46 logMAR units pre-operatively which improved to 0.36 ± 0.19 logMAR units post DALK at 6 months (P < 0.001). The mean Root Mean Square (RMS) (μm) of the magnitude of total corneal aberrations, HOA and LOA from central 6mm zone of cornea were 14.6 ± 9.2, 4.7 ± 2.9, and 13.8 ± 8.8, respectively. The mean anterior (120μm), central and posterior corneal (60μm) densitometry in 0-2mm zone were 25.8 ± 7.7 GSU, 18.7 ± 4.16 GSU and 10.09 ± 3.9 GSU respectively. A statistically significant correlation of postoperative residual stromal bed thickness, total corneal HOA, LOA, total corneal aberrations, HOA front and posterior corneal densitometry (0-2mm zone) with postoperative BSCVA was found. Though there is a significant improvement in BSCVA after DALK, the quality of vision in terms of aberrometry and densitometry is suboptimal, especially in cases undergoing manual DALK compared to those undergoing big bubble formation.

Relationship between Postoperative Intraocular Pressure and Refractive Outcomes in Patients after Deep Anterior Lamellar Keratoplasty.

Purpose:To study the effect of intraocular pressure (IOP) on refractive outcomes after deep anterior lamellar keratoplasty (DALK).Methods:This retrospective study included eyes which underwent DALK. DALK technique involved either modified Anwar big-bubble if possible or manual anterior lamellar dissection. Our main outcome measures are postoperative IOP and refractive outcomes at postoperative week and months 1, 3, 6, and 12.Results:Fifty-nine eyes of 59 patients were included. DALK was performed for optical (93.2%) and tectonic (6.8%) purposes. 76.3% of the patients had keratoconus. Anwar's big-bubble technique was successful in 30 cases. Linear mixed-model was used to analyze the effect of the highest postoperative IOP measured prior to measurement of postoperative cylinder. Patients with greater maximum postoperative IOP measured had worse postoperative cylinder (P = 0.015) and spherical equivalent (P = 0.012). Those with IOP more than 21 mmHg had worse postoperative cylinder (P = 0.050) and spherical equivalent (P = 0.054). The method of DALK and presence of suture removal were not shown to statistically affect postoperative cylinder.Conclusion:Our study shows a positive correlation between postoperative IOP and worse spherical equivalent and cylinder post-DALK, emphasizing the need for good IOP control with IOP-lowering medication(s).

A novel method of tunnel creation using intraoperative optical coherence tomography-guided deep anterior lamellar keratoplasty.

The big bubble technique has become the technique of choice for performing deep anterior lamellar keratoplasty (DALK) since its inception in 2002. The main challenge with this technique is in achieving a big bubble while preventing inadvertent perforation of the Descemet’s membrane. Although femtosecond lasers have increased the safety, accuracy, and predictability of corneal dissection in DALK, the challenge of achieving a big bubble still exists. To overcome this challenge, Zeimer Z8 Femto LDV has launched a new software module for DALK, which has an added advantage of real-time optical coherence tomography–assisted femtosecond tunnel creation for achieving a big bubble.

Descemet's membrane area and posterior corneal power may predict the Descemet membrane folds after deep anterior lamellar keratoplasty in patients with advanced keratoconus.

To investigate possible predictive topographic characteristics for the development of Descemet's membrane (DM) folds after the uneventful deep anterior lamellar keratoplasty (DALK). A retrospective study included 56 eyes of 56 consecutive patients who underwent uneventful DALK using the big-bubble technique to treat advanced keratoconus. At baseline and each visit, best-corrected logMAR visual acuity (BCVA), slit-lamp findings, endothelial cell density, topographic parameters were recorded. DM area is calculated using morphogeometric modelling. Twelve (21.4%) of them exhibited DM folds, whereas the remaining 44 (78.6%) did not exhibit any DM folds after the surgery. The mean follow-up time was 36.3 ± 16.7 (range, 12-71) months. The mean posterior corneal power was - 13.8 ± 0.6 D in patients with DM folds, whereas - 13.0 ± 0.8 D in those without DM folds (p = 0.016). The mean DM area was 53.6 ± 2.3 (50.9-57.9) mm2 in patients with DM folds, whereas 51.6 ± 1.7 (47.1-53.9) mm2 in those without DM folds (p = 0.001). The ROC curve showed that two best cut-off value for the posterior corneal power and DM area were 13.75 D and 53.8mm2, respectively, to predict the occurrence of DM folds. DALK surgery seems to cause DM folds in patients with large DM area and high posterior corneal power.

Comparison of the effects of femtosecond laser energy on corneal endothelium at two different dissection levels in femtosecond laser-assisted deep anterior lamellar keratoplasty for keratoconus.

The objective of this study is to compare the endothelial safety of femtosecond laser (FSL) energy at two different dissection depths in FSL-assisted deep anterior lamellar keratoplasty (FSDALK) for keratoconus. This prospective double-armed interventional study included 25 eyes from 21 patients with advanced keratoconus who underwent FSDALK (big bubble technique) at a trephination depth of 110µm in group I (11 eyes) and 80µm in group II (14 eyes)-all of which were anterior to the Descemet's membrane (DM). Visual acuity measurement, anterior and posterior segment examination, corneal tomography, and specular microscopy were performed preoperatively and at 3, 6, and 12months, postoperatively. Endothelial cell density, coefficient of variation, percentage of cell hexagonality, and pachymetry were used to evaluate endothelial safety. No statistically significant difference in any of the endothelial safety parameters was found between the two groups. The mean 12-month postoperative endothelial cell loss rate was 17.46% and 12.91% in group I and II, respectively (P = 0.345). Most of the endothelial cell loss occurred during the first 3months after surgery. Group II showed statistically greater improvement in the mean keratometry values at all follow-up visits. The endothelial safety profiles of lamellar FSL cuts at 110µm and 80µm anterior to the DM are comparable. Cuts as deep as 80µm anterior to the DM can be safely applied without causing significant injury to the endothelium. Further studies are needed to compare the endothelial safety profiles of different FSL platforms available in the market. Trial registration PACTR201901615323963. Registered 24 November 2018-retrospectively registered.

Evaluation of deep anterior lamellar keratoplasty for anterior corneal stromal pathology

Settings This study was conducted in Mansoura Ophthalmic Center, Mansoura University, Egypt, during the period from January 2018 to January 2019. Purpose This study aimed to evaluate the visual outcomes, topographic features, endothelial cell densities (ECD), and complications of deep anterior lamellar keratoplasty using big-bubble technique (BB-DALK) in different corneal stromal pathologies. Patients and methods This was a prospective, interventional study that included 24 eyes of 24 patients having corneal stromal pathologies, not involving Descemet membrane (DM) and endothelium. The primary outcome measures were the clinical, visual, and topographic outcomes (uncorrected visual acuity, best-corrected visual acuity, K1, and K2) throughout the follow-up period, whereas the secondary outcome measures were the refractive outcomes, central corneal thickness, ECD, and intraoperative and postoperative complications. Results A total of 21 (87.5%) patients underwent uneventful BB-DALK, and three (12.5%) cases were complicated by intraoperative DM microperforation who developed DM detachment and double anterior chamber (AC) postoperatively. One of them resolved spontaneously and the other two cases required intracameral air injection. Uncorrected visual acuity improved from 1.55±0.26 (logarithm of minimum angle of resolution) preoperatively to 0.63±0.2 1 year postoperatively (P&lt;0.001) and best-corrected visual acuity improved from 1.08±0.11 (logarithm of minimum angle of resolution) to 0.30±0.12 (P=0.017). Refractive cylinder improved from −7.79±1.75 to −2.85±2.01 at 12 months of follow-up (P=0.007). Average K reading changed from 60.00±7.77 preoperatively to 43.43±2.98 postoperatively (P&lt;0.001). Total ECD was 2248.08±431.13 by the end of the first year, with a mean of 8.2% endothelial cell loss. Loosening of the sutures occurred in five (20.8%) eyes between third and sixth months postoperatively. Urrets-Zavalia syndrome occurred in one of the two cases who were complicated with postoperative double AC and required intracameral air injection. Conclusions BB-DALK is an effective and safe technique for treatment of different corneal stromal pathologies sparing endothelium and DM.

Comparison of Endothelial Cell Loss following the Big Bubble versus the Microbubble Incision Technique during Deep Anterior Lamellar Keratoplasty in Eyes with Keratoconus

Introduction. Deep anterior lamellar keratoplasty (DALK) is now becoming an increasingly popular surgical technique in treating corneal stromal pathologies with healthy endothelium. Several advantages of DALK over penetrating keratoplasty (PKP) have been described such as maintenance of globe integrity, absence of endothelial rejection, and a low rate of chronic endothelial cell loss (ECL). ECL following PKP results in 50% cell loss after 2 years from the estimated graft endothelial cell density (ECD). Although there are several reports confirming that ECL following DALK is similar to the physiologic cell loss 2 years after surgery, few reports discussed the surgically induced ECL due to difficulty in preoperative imaging of ECD. Materials and Methods. This prospective, interventional study included 20 eyes of 20 patients, who underwent DALK surgery. 11 eyes underwent DALK using the big bubble technique, while 9 eyes underwent the microbubble technique. Postoperative evaluation was done 3 months after surgery and included best spectacle corrected visual acuity (BSCVA), keratometric readings, and refraction measured using an autokeratorefractometer (Topcon KR800, Japan) and endothelial cell density (ECD) using noncontact specular microscopy (Nidek CEM-530, Japan). Results. Regarding postoperative parameters such as postoperative logMAR visual acuity, postoperative mean K, and postoperative K max, there was no statistical difference found between both groups ( P = 0.754 , P = 0.119 , and P = 0.970 , respectively). Regarding change in specular endothelial cell density and percent change in the specular endothelial cell density, again there was no statistical difference between both groups with P = 0.057 and P = 0.126 , respectively (significance defined as P &lt; 0.05 ). Conclusion. ECD is not affected by failure of the big bubble to form and continuing DALK via the microbubble technique.

Modified deep anterior lamellar dissection for corneal opacity during vitrectomy: case reports

BackgroundTo introduce a modified deep anterior lamellar dissection technique to improve visibility during surgery for vitreoretinal diseases with coexisting corneal opacity.Case presentationTwo patients with retinal detachment and coexisting corneal blood staining or corneal decompensation underwent modified deep anterior lamellar dissections followed by vitrectomy. The modified deep anterior lamellar dissection techniques, unlike the dissection and removal of corneal lamellar in a typical deep anterior lamellar keratoplasty, included the creation and preservation of a deep lamellar corneal flap, the retroillumination to visualize and easily remove the remaining opaque stroma on the Descemet membrane, and the big air bubble technique in the eye with endothelial decompensation. The patient’s own cornea flap was sutured back after vitrectomy was done. The modified dissection techniques provided adequate fundus view during vitrectomy while removing as less corneal tissue as possible and decreasing the surgical complications and the requirement of a fresh cornea. Postoperatively, in case 1, the corneal blood staining was gradually absorbed and the vision improved from light perception to counting fingers. In case 2, even though the cornea remained cloudy and the vision was poor, the cornea endothelial decompensation was stable and asymptomatic. Both retinas were attached after silicone oil removal at 6-month follow-up.ConclusionsThis modified and limited deep anterior lamellar corneal dissection procedure appears to be a useful alternative to penetrating keratoplasty, ophthalmic endoscope and temporary keratoprosthesis during the vitrectomy with coexisting corneal opacity.

Demonstration of Optical Coherence Tomography Guided Big Bubble Technique for Deep Anterior Lamellar Keratoplasty (DALK).

Deep anterior lamellar keratoplasty (DALK) is a highly challenging procedure for cornea transplant that involves removing the corneal layers above Descemet’s membrane (DM). This is achieved by a “big bubble” technique where a needle is inserted into the stroma of the cornea down to DM and the injection of either air or liquid. DALK has important advantages over penetrating keratoplasty (PK) including lower rejection rate, less endothelial cell loss, and increased graft survival. In this paper, we successfully designed and evaluated the optical coherence tomography (OCT) distal sensor integrated needle for a precise big bubble technique. We successfully used this sensor for micro-control of a robotic DALK device termed AUTO-DALK for autonomous big bubble needle insertion. The OCT distal sensor was integrated inside a 25-gauge needle, which was used for pneumo-dissection. The AUTO-DALK device is built on a manual trephine platform which includes a vacuum ring to fix the device on the eye and add a needle driver at an angle of 60 degrees from vertical. During the test on five porcine eyes with a target depth of 90%, the measured insertion depth as a percentage of cornea thickness for the AUTO-DALK device was without any perforation compared to for unassisted free-hand insertion and for assisted free-hand insertion. The result showed a higher precision and consistency of the needle placement with AUTO-DALK, which could lead to better visual outcomes and fewer complications.

Deep anterior lamellar keratoplasty in eyes previously treated with collagen crosslinking for keratoconus: 3-year results

To evaluate the 3-year results of deep anterior lamellar keratoplasty (DALK) using the big-bubble technique in keratoconus patients with previous corneal collagen crosslinking (CXL) treatment. Twenty eyes of 20 keratoconus patients who underwent DALK surgery using the big-bubble technique after CXL treatment between January 2011 and September 2015 were retrospectively reviewed. All patients completed 3years follow-up. Intraoperative and postoperative complications were recorded. Uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), maximum keratometry, keratometric astigmatism and endothelial cell density (ECD) were analysed. The mean interval between CXL and DALK surgery was 47.5 ± 24.0months (mean ± SD). DALK was completed in all eyes. Big-bubble was successfully achieved in 16 eyes (80%), and manual dissection was performed in four eyes (20%). Microperforation occurred in three eyes (15%). Postoperatively, persistent epithelial defect occurred in three eyes (15%). The mean UCVA and mean BSCVA values were significantly improved preoperatively to all postoperative visits (p < 0.001). UCVA was 20/100 or lower in all eyes preoperatively and 20/100 or better in 18 eyes (80%) at 3years; BSCVA was 20/40 or better in all eyes (100%) and 20/20 or better in three eyes (15%), and keratometric astigmatism was lower than 4 dioptres in 14 eyes (70%) at 3years. The mean ECD loss was 6.3 ± 4.4% at 1year, 9.0 ± 6.3% at 2years and 11.2 ± 7.4% at 3years. Previous CXL treatment in keratoconus patients did not cause a negative impact on the visual, refractive and surgical outcomes of DALK surgery using the big-bubble technique. DALK surgery seems to be a safe and effective surgical approach in these patients.