Big-bubble Deep Anterior Lamellar Keratoplasty Research Articles

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

PurposeTo 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).MethodsThis 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.ResultsThe 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.ConclusionCorneal 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.

Spike sign - To predict the formation of big bubble in deep anterior lamellar keratoplasty in advanced keratoconus.

Lamellar surgeries have revolutionized our understanding and practice of keratoplasties. However, the learning curve in deep anterior lamellar keratoplasty (DALK) makes it daunting for novice surgeons. This paper describes a unique intraoperative sign - the radial "spike sign," which heralds the commencement of a big bubble in some cases of advanced keratoconus in eyes that have not undergone any previous surgery. The spike sign was noted during big bubble DALK surgery and was then retrospectively looked for in recorded DALK surgical videos and correlated with the formation of a big bubble. The movement of air after injection was classified into the direct formation of a big bubble, stromal emphysema with no big bubble, and emphysema with the spike sign followed by a big bubble. In total, 104 surgical videos of big bubble attempts were evaluated and classified as such. The spike sign helps reduce the number of unnecessary attempts at big bubble formation during DALK, thus improving surgical outcomes.

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 Robot-Assisted and Manual Cannula Insertion in Simulated Big-Bubble Deep Anterior Lamellar Keratoplasty.

This study aimed to compare the efficacy of robot-assisted and manual cannula insertion in simulated big-bubble deep anterior lamellar keratoplasty (DALK). Novice surgeons with no prior experience in performing DALK were trained to perform the procedure using manual or robot-assisted techniques. The results showed that both methods could generate an airtight tunnel in the porcine cornea, and result in successful generation of a deep stromal demarcation plane representing sufficient depth reached for big-bubble generation in most cases. However, the combination of intraoperative OCT and robotic assistance received a significant increase in the depth of achieved detachment in non-perforated cases, comprising a mean of 89% as opposed to 85% of the cornea in manual trials. This research suggests that robot-assisted DALK may offer certain advantages over manual techniques, particularly when used in conjunction with intraoperative OCT.

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.

Large-Diameter Modified Big-Bubble Deep Anterior Lamellar Keratoplasty in Post–Radial Keratotomy Eyes

To report the outcomes of our modified large-diameter (9 mm) big-bubble deep anterior lamellar keratoplasty (DALK) technique with improved success rates of pneumatic dissection in post-radial keratotomy (RK) eyes. Ospedali Privati Forlì, "Villa Igea", Forlì, Italy. Retrospective case series. Modified big-bubble DALK was performed in consecutive post-RK eyes. The technique included large diameter (9-mm) diameter deep partial thickness trephination based on the thinnest anterior segment optical coherence tomography pachymetry value at 9 mm; air injection through a cannula advanced 2 mm centripetally from the base of the trephination; limited stromal clearance of the central 6 mm optical zone; suturing of a 9-mm anterior lamellar graft prepared by microkeratome dissection. Success rate of pneumatic dissection, corrected distance visual acuity (CDVA), keratometric astigmatism and complications were recorded. 8 eyes of 7 patients were included. Pneumatic dissection succeeded in 7 cases (87.5%). CDVA significantly improved from 0.94 ± 0.43 to 0.14 ± 0.06 logMAR (P <.001). All eyes reached Snellen CDVA ≥ 20/40, while 3 eyes (37.5%) reached ≥ 20/25. At the last follow-up, 5 eyes (62.5%) had a final keratometric astigmatism ≤4 D, while 2 eyes (25.0%) had ≤ 2 D. Big-bubble DALK can be successfully performed in post-RK eyes with our standardized technique.

Outcomes of Conventional 8.0-mm Versus Large 9.0-mm Diameter Deep Anterior Lamellar Keratoplasty for Keratoconus.

The purpose of the study was to compare the clinical outcomes of large 9.0-mm diameter and conventional 8.0-mm big-bubble deep anterior lamellar keratoplasty (DALK). In this comparative, retrospective interventional case series, medical records of 124 cases of large 9.0-mm diameter DALK from January 2017 to December 2019 and 133 conventional 8.0-mm DALK from January 2014 to December 2016 performed by a single surgeon for the indication of keratoconus were reviewed. Main outcome measures were best spectacle-corrected visual acuity (BSCVA), refractive astigmatism (RA), and postoperative complication rates. Postoperative logarithm of the minimum angle of resolution BSCVA did not significantly differ between 9.0-mm and 8.0-mm DALK at any time points. Although the cumulative percentage of eyes achieving Snellen BSCVA of 20/40 or better was comparable between groups (9.0-mm DALK: 93%, 8.0-mm DALK: 90%, P = 0.571), the cumulative percentage of eyes achieving 20/20 or better (9.0-mm DALK: 44%, 8.0-mm DALK: 26%, P = 0.01) and 20/25 or better (9.0-mm DALK: 74%, 8.0-mm DALK: 59%, P = 0.03) was significantly higher in the 9.0-mm DALK group. RA was significantly lower in the 9.0-mm DALK group compared with the 8.0-mm DALK group during all time points ( P < 0.001). The percentage of eyes with RA less than or equal to 4.0 D was significantly lower in the 9.0-mm DALK patients (90%) compared with in 8.0-mm DALK group (72%) ( P = 0.002). Postoperative complication rates were similar between groups. Compared with conventional 8.0-mm DALK, large 9.0-mm DALK can provide superior visual outcomes at higher levels of Snellen BSCVA and significantly lower degrees of astigmatism without an increased risk of immune rejection and graft failure.

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.

Long-Term Outcomes of Big Bubble Deep Anterior Lamellar Keratoplasty in Mucopolysaccharidoses: A Retrospective Case Series and Review of the Literature.

The purpose of this study was to report the long-term surgical and visual outcomes of patients with mucopolysaccharidoses (MPS) after big bubble deep anterior lamellar keratoplasty (BB-DALK). This was a retrospective case series of patients with MPS who underwent BB-DALK at a single academic institution. All patients had corneal clouding secondary to MPS limiting visual acuity for which keratoplasty was indicated. Each patient was evaluated and underwent surgery by a single surgeon. Reported data included age at keratoplasty, sex, MPS type, best spectacle-corrected visual acuity, change in pachymetry, ocular comorbidities, surgical complications, and MPS-related medication use. Outcomes of 12 eyes from 7 patients with MPS type I (Hurler, Scheie, and Hurler-Scheie) are reported using the newest nomenclature. The mean follow-up was 5.58 years (range: 1-10 years). All cases underwent BB-DALK with a type 1 big bubble during the surgery. Two cases (16.6%) required rebubbling because of partial Descemet membrane detachment. One case was complicated by a suture abscess and required a penetrating keratoplasty. No episodes of rejection occurred. Statistically significant improvement in the best spectacle-corrected visual acuity (from a mean 0.85-0.33 logarithm of the minimum angle of resolution, P = logarithm of the minimum angle of resolution 0.0054) and pachymetry (mean reduction of -145.4 μm, P = 0.0018) was observed. BB-DALK seems to be an acceptable long-term surgical option in patients with MPS. Our findings suggest that this technique is reproducible and can achieve clear corneal grafts with good visual results on a long-term follow-up.

Late-onset Descemet's membrane detachment secondary to presumed interface fluid syndrome after uneventful deep anterior lamellar keratoplasty for keratoconus

<br>A forty-year-old male underwent an uneventful big-bubble deep anterior lamellar keratoplasty (DALK) for keratoconus in the right eye. Suture removal was attempted 15 months post-surgery and led to temporal graft host dehiscence that required resuturing of the graft. The patient presented 4 months later with increased intraocular pressure (IOP), graft edema, and nasal Descemet membrane detachment (DMD). IOP control with medication led to reduction and total resolution of DMD and a clear graft. We postulate that the DMD, in this case, was caused by a mechanism similar to the interface fluid syndrome (IFS) that occurs in post-laser<i> in situ </i>keratomileusis (LASIK) eyes and should be considered as a differential diagnosis for DMD following DALK.<br>

Assessment of Corneal Densitometry in Big-Bubble Dissection Versus Manual Dissection Deep Anterior Lamellar Keratoplasty.

The aim of this study was to assess corneal densitometry and visual outcomes after big-bubble deep anterior lamellar keratoplasty (BB-DALK) and manual dissection deep anterior lamellar keratoplasty in patients with keratoconus. This retrospective comparative observational study included 40 keratoconic patients who underwent DALK surgery: 22 eyes had BB-DALK (group I) and 18 eyes had failed BB technique and DALK was completed by manual dissection (group II). Best -corrected visual acuity (BCVA), corneal topographic parameters, residual stromal tissue thickness, and endothelial cell count were recorded at 1, 3, 6, and 12 months postoperatively. Densitometric analysis of different corneal layers and zones was performed using Scheimpflug tomography at each visit; values were recorded and compared between the 2 groups. At 1 and 6 months postoperatively, BCVA was better in group I than in group II, but with no statistically significant difference. At 12 months, the visual acuities became nearly similar in both groups (0.30 ± 0.13 vs. 0.30 ± 0.14 logarithm of the minimum angle of resolution, P = 0.888). Regarding corneal densitometric analysis, the recorded values for the posterior corneal layer were significantly higher in group II compared with group I at 3, 6, 9, and 12 months postoperatively in the 0- to 2-mm zone (P < 0.001) and the 2- to 6-mm zone (P = 0.029, 0.028, 0.001, and <0.001). Manual dissection DALK after failed BB technique may affect the interface stromal reflectivity up to 12 months postoperatively. However, this does not significantly affect the visual acuity in comparison with successful BB-DALK.

Microscope-Integrated Intraoperative Optical Coherence Tomography-Guided Big-Bubble Deep Anterior Lamellar Keratoplasty.

The purpose of this study was to evaluate the feasibility of microscope-integrated intraoperative optical coherence tomography (OCT) for real-time quantitative analysis of surgical planes in big-bubble deep anterior lamellar keratoplasty (DALK). In this interventional case series, intraoperative OCT-guided big-bubble DALK was performed in 16 consecutive eyes of 16 patients with keratoconus. Trephination depth was measured using the intraoperative OCT caliper tool. Aiming for a depth within 150 μm from the endothelial surface, the trephination groove was extended to a deeper plane using a 15-degree blade. Repeat OCT scans were taken to measure residual stromal thickness before insertion of the DALK probe from the bottom of the extended trephination. Caliper measurements, success rate of pneumatic dissection, and complications were recorded. After trephination, residual stromal thickness exceeded 150 μm in all eyes and averaged 257.1 ± 42.5 μm. In each case, the initial trephination groove was extended to a depth within 150 μm from the endothelial surface (118.9 ± 27.1 μm). Big-bubble formation was achieved in 12 eyes (75%). Type 1 bubble was obtained in 11 eyes. Perforation requiring conversion to penetrating keratoplasty occurred in 4 eyes during insertion of the cannula into a residual stromal bed of <100 μm (n = 2; 63 and 75 μm) or layer-by-layer dissection (n = 2). Quantitative analysis of intraoperative OCT scans can be used to assist decision-making on whether to proceed with pneumatic dissection or extend the trephination groove, thereby facilitating insertion of the injection cannula at the desired stromal depth.

Comparison of complications and visual outcomes between big-bubble deep anterior lamellar keratoplasty and penetrating keratoplasty for fungal keratitis.

To compare the postoperative complications and visual outcomes of big-bubble deep anterior lamellar keratoplasty (BB-DALK) and penetrating keratoplasty (PK) for fungal keratitis (FK). This retrospective study included 94 cases of BB-DALK for FK and 161 cases of PK for FK from a tertiary ophthalmology care centre. The most common FK pathogens were Fusarium (n= 84, 32.9%) and Aspergillus (n= 67, 26.3%). The recurrence rates after BB-DALK and PK were 3.2 and 5%, respectively (p= 0.723). The follow-up duration was 31.9± 15.8months in the BB-DALK group and 33.9± 15.0months in the PK group. The immune rejection rate was significantly lower in the BB-DALK group than in the PK group (1.1 vs. 18.6%, p< 0.001), as was the incidence of secondary glaucoma (p= 0.018). Endothelial cell density in the BB-DALK group tended to be stable at postoperative month 6, whereas the PK group still attenuated at a hyper-physiological rate. Postoperative best-corrected visual acuity (BCVA) significantly improved in both groups (p< 0.001). No significant difference between-group was observed in BCVA, refractive cylinder, and spherical equivalent postoperatively. Big-bubble DALK is a useful and safe alternative to PK for medically uncontrolled FK.

Preferred practice pattern and observed outcome of deep anterior lamellar keratoplasty - A survey of Indian corneal surgeons.

Purpose:This study aimed to assess the preferred surgical technique and outcome of deep anterior lamellar keratoplasty (DALK) among corneal surgeons in India.Methods:An online questionnaire-based cross-sectional survey was conducted among members of the Cornea Society of India (CSI) with experience of performing >10 DALK procedure. The responses pertaining to their surgical experience, preferred technique, complications, and outcome of DALK were collected and analyzed.Results:A total of 156 responses were received. In total, 35.9% of participants reported annual keratoplasty of >50, and DALK constituted >25% surgeries for 25% of participants. Ectatic corneal disorder was reported as the most common indication for DALK by 71.6% of the respondents. Big-bubble (BB) DALK (WA-1.82) was the most preferred technique, along with suction trephine (50%) for partial trephination and bottom port cannula (45.5%) for BB formation. On statistical analysis, no difference was observed in the surgeon reported success rate of BB formation with or without anterior lamellar keratectomy (ALK) (χ2 (1,156) = 3.1498, P = 0.08) or paracentesis (χ2 (1,156) = 0.2737, P = 0.60) before stromal air injection, and method of stromal air injection (χ2 (1,156) = 4.7325, P = 0.09). Conversion to penetrating keratoplasty was reported by 16% of participants in >25% cases, while 66.7% reported in <10% cases. Cataract and double anterior chamber were the most common complications. 50% of participants suggested that >20 procedures are required to overcome the learning curve.Conclusion:BB DALK is the most commonly practiced DALK technique, and its success is independent of ALK and paracentesis being performed prior to air injection and method of air injection (cannula/needle).

Modified big-bubble for deep anterior lamellar keratoplasty.

A new technique of air injection is described for big-bubble deep anterior lamellar keratoplasty (DALK) in eyes with keratoconus, along with a comparative analysis of the original technique. Fifty eyes were analyzed in each group. The mean steep keratometry and anterior chamber depth distribution were comparable between the 2 groups. The mean size of type 1 bubble achieved with single air injection (Group 1) was 7.8 ± 0.4 mm (range 6.5 to 8.5 mm), and with sequential air injection (Group 2) was 8.5 ± 0.3 (range 8 to 9 mm) (P < .001). Intraoperative complications of spontaneous bursting of bubble in 1 eye (2%) and peripheral microperforation in 3 eyes (6%) occurred only in Group 1. The modified technique of big-bubble DALK using sequential air injection aided by paracentesis to lower intraocular pressure allowed enlargement of a type 1 bubble in a safe and controlled manner with minimal risk for complications.

Automated digital analysis of intraoperative keratoscopy and its correlation with postoperative astigmatism after big-bubble deep anterior lamellar keratoplasty.

To investigate the correlation between postoperative corneal astigmatism (PCA) and values of intraoperative keratoscopy analyzed with a newly developed automated technique in patients undergoing big-bubble (BB) deep anterior lamellar keratoplasty (DALK). Photographs of keratoscope rings taken at the end of BB-DALK were analyzed using ImageJ for the calculation of "roundness" (R): values = 1 indicate a perfect circle. Pearson's correlation was used to evaluate the relationship between R and PCA that measured 1week (V1), 3months (V2), and 18months (V3), postoperatively. The area under the curve (AUC) of receiver operating characteristic (ROC) curve was used to evaluate the accuracy of R for identifying patients with PCA < 3 diopters (D). The point on the ROC curve nearest to the coordinate (0,100) was used as a cutoff to determine sensitivity and specificity. Data from 121 patients were included. The mean value of R*was 0.93 ± 0.04 (range 0.76-0.99). R showed a significant correlation with PA at V3 (R = - 0.42, P < 0.01). The ROC curve had an AUC of 0.69 (95% CI 0.59-0.79). A cutoff value of R= 0.93 had a sensitivity of 70.3% and specificity of 61.0% for identifying patients with PA < 3D at V3. This new digital analysis of keratoscope rings allows to identify with reasonably good diagnostic accuracy patients with low values of post-DALK astigmatism correctable with spectacles.

Preliminary Results of a Novel Standardized Technique of Femtosecond Laser-Assisted Deep Anterior Lamellar Keratoplasty for Keratoconus.

Purpose To evaluate the feasibility and the initial outcomes of a novel standardized surgical technique of femtosecond laser- (FSL-) assisted big-bubble deep anterior lamellar keratoplasty (BBDALK) for eyes with keratoconus. Methods This prospective interventional case series included 11 consecutive FSL-assisted BBDALK procedures performed for the eyes with keratoconus from September 2019 to December 2019. The FSL was used to create (i) an intrastromal channel incision (1.7 mm in length, 4.6 mm in width, 80% depth, and cut energy of 1.70 μJ) and (ii) a 9.0 mm diameter circular lamellar side cut 65 μm above the endothelium (cut energy of 0.90 μJ) intersecting the intrastromal incision. In the operating room, a blunt dissector was used to open the intrastromal channel incision, through which a blunt spatula was inserted, tangentially advanced towards the center of the cornea, and replaced with a blunt cannula for pneumatic dissection. The subsequent surgical steps did not differ from the conventional technique. Main outcome measures were the success rate of pneumatic dissection and the percentage of intraoperative complications. Results Eleven eyes of 11 patients (6 males and 5 females; mean age: 34.54 ± 13.23 years) underwent FSL-assisted DALK. Using the FSL, both corneal incisions (lamellar side cut and intrastromal channel incision) were successfully created in all cases without the need for repeat docking or additional dissection. Pneumatic dissection with type 1 bubble formation succeeded in all 11 eyes (100%). DALK surgery was completed uneventfully in all cases. Descemet membrane perforation did not occur in any case, and no procedure was converted to penetrating keratoplasty. Conclusion Using standardized FSL parameters for both incision design and cut energy in BBDALK surgery, pneumatic dissection can be achieved in a very high rate of cases with minimal risk of intraoperative complications.

Femtosecond laser-assisted big bubble for deep anterior lamellar keratoplasty.

To assess the utility of a femtosecond laser-assisted stromal channel to assist the creation of a big bubble (BB) for deep anterior lamellar keratoplasty (DALK) surgery in cadaveric corneas. L V Prasad Eye Institute, Hyderabad, India. Experimental study. An attempt to create a BB was made on 10 donor pairs of human cadaveric corneoscleral tissues. The 20 corneas were split into 2 groups: Group A underwent femtosecond laser pretreatment and Group B had conventional manual deep lamellar technique. Laser pretreatment was performed using the VisuMax femtosecond laser system to create a stromal channel using the intracorneal ring segment treatment module for direct insertion of the 27-gauge air cannula for pneumodissection at a predetermined depth. Of the 20 corneas studied, type 1 BB was achieved in 9 of 10 corneas in Group A and in 7 of 10 corneas in Group B. One cornea from Group A had a combined type 1 and 2 BB, whereas no BB was achieved in 1 cornea. Creation of an intrastromal channel using a femtosecond laser at a predetermined depth seemed to be a promising option to increase the chances of achieving a BB when compared with the conventional air injection technique of BB DALK.

Comparison of Corneal Densitometry Between Penetrating Keratoplasty and Deep Anterior Lamellar Keratoplasty in Keratoconus Patients.

Our aim was to compare corneal densitometry values in keratoconic eyes undergoing deep anterior lamellar keratoplasty with the "big bubble" and manual lamellar dissection techniques, as well as penetrating keratoplasty. This retrospective study evaluated the postoperative outcomes of 31 eyes treated with big bubble-deep anterior lamellar keratoplasty, 23 eyes with manual lamellar dissectiondeep anterior lamellar keratoplasty, and 37 eyes with penetrating keratoplasty. Corneal densitometry, best corrected visual acuity, and other corneal tomographic parameters were recorded at 1, 6, 12, and 24 months postoperatively. The groups were compared with respect to the outcomes. There were no significant differences between the groups with respect to the anterior, central, and total corneal densitometry values at 0 to 2 mm and 2 to 6 mm. At 1 month postoperatively, the densitometric value in the posterior corneal layer of the 0- to 2-mm and 2- and 6-mm corneal zones was higher in the manual lamellar dissection-deep anterior lamellar keratoplasty group than in the big bubble-deep anterior lamellar keratoplasty and penetrating keratoplasty groups (P = .001). At 6, 12, and 24 months, the manual lamellar dissectiondeep anterior lamellar keratoplasty and penetrating keratoplasty groups had similar values in both zones in the posterior layer. The difference between manual lamellar dissection-deep anterior lamellar keratoplasty and big bubble-deep anterior lamellar keratoplasty in both zones in the posterior layer was statistically significant at 6, 12, and 24 months postoperatively (P < .05). The best corrected visual acuity of big bubble-deep anterior lamellar kerat oplasty and penetrating keratoplasty groups was better than that of the manual lamellar dissection-deep anterior lamellar keratoplasty group (P = .047). Corneal densitometry values may vary depending on the type of keratoplasty used in keratoconus patients. Higher densitometry values may affect visual quality in keratoplasty patients by decreasing or filtering the light that reaches the retina.

Deep anterior lamellar keratoplasty techniques; predescemetic versus big bubble: Anterior segment optical coherence tomography study

To compare the visual and refractive outcomes and anterior segment optical coherence tomography (AS-OCT) findings of 2different deep anterior lamellar keratoplasty (DALK) techniques in the treatment of advanced keratoconus with and without successful big bubble formation. In this retrospective comparative case series, data from 79consecutive eyes of 69patients who underwent either big bubble (group 1, n: 62) or manual DALK (group 2, n: 17) were analyzed. The visual and refractive results, keratometric values and residual stromal thickness were assessed. Patients were seen at 1, 3, 6 and 12 months after the procedure and 1 month after complete suture removal. A big bubble was successfully obtained in 62eyes (78.5%; group 1) and manual dissection was performed in the 17remaining eyes (21.5%; group 2). The final best spectacle-corrected visual acuity (BSCVA) was 0.38 logMAR and 0.55 logMAR in Group 1 and 2, respectively (P<0.05). At the final visit, BSCVA≤0.30 logMAR was achieved in 80% and 60.8% of eyes in Groups 1 and 2, respectively (P<0.001). Groups 1 and 2 were comparable in terms of mean keratometry: 47.80D±2.81D (range, 41.30D to 54.2D) versus 45.90D±3.62D (range, 41.10D to 53.8 D), respectively; (P=0.56) and keratometric astigmatism: 3.81D± 2.1D (range, 1.0D to 6.20D) versus 3.56D±1.92D (range 1.2D to 6.85D), respectively; (P=0.40) at the final follow-up. The mean residual stromal thickness was 36.90±17.80μm in group 2. The presence of residual posterior corneal stroma when big bubble formation is not successfully achieved in DALK is correlated with lower postoperative visual acuity.