Prediction of Descemet Membrane Perforation During Deep Anterior Lamellar Keratoplasty in Patients With Keratoconus With Stromal Scar

Effect of Keratoconus Stage and Classification Parameters on Deep Anterior Lamellar Keratoplasty Outcomes

PURPOSE

The aim of this study was to investigate the effect of the keratoconus (KC) stage according to the Amsler-Krumeich classification system and the parameters used in this classification on deep anterior lamellar keratoplasty outcomes.

METHODS

The preoperative KC stage was determined, and the presence of corneal scarring was noted. The preoperative and postoperative best-corrected visual acuity (BCVA), refractive error, mean central keratometry (K mean ) readings, topographic astigmatism, and minimum corneal thickness (CT) values were recorded. Intraoperative and postoperative complications were also noted.

RESULTS

One hundred thirty-seven eyes (54 eyes in stage 3-83 eyes in stage 4) were included in the study. The mean follow-up period was 42.20 ± 24.36 months. There was no statistically significant difference between stage 3 and 4 KC groups for postoperative BCVA, K mean , CT, spherical equivalent, and topographic astigmatism values (each P value >0.05). The effect of preoperative BCVA, K mean , CT, and refractive error values on postoperative BCVA could not be demonstrated ( P = 0.264). In addition, no statistically significant correlation was found between postoperative and preoperative values (each P value > 0.05). Although intraoperative Descemet membrane perforation and postoperative early suture loosening were observed more frequently in stage 4 KC than in stage 3 KC, the 2 groups were statistically similar for these and other complications (each P value >0.05).

CONCLUSIONS

The preoperative KC stage and the parameters used in classification are not useful in predicting postoperative deep anterior lamellar keratoplasty outcomes. The timing of the surgery should be planned with the awareness that the progression of the disease will not have a negative effect on outcomes.

Main issues in deep anterior lamellar keratoplasty: A systematic narrative review

Deep anterior lamellar keratoplasty (DALK) has emerged as a transformative approach in managing corneal pathologies, notably keratoconus (KC), providing a viable alternative to penetrating keratoplasty (PK). This systematic review explores the intricacies of DALK, comparing its preoperative, intraoperative, and postoperative considerations with PK. Extensive literature searches revealed a wealth of data regarding DALK's advantages and challenges, with an emphasis on graft survival, visual outcomes, and complications. In the preoperative phase, DALK showcases its versatility, catering to a wide spectrum of patients, including those with KC and ocular surface disorders. Intraoperatively, it offers innovative techniques to address emphysema, bubble formation, and Descemet's membrane perforation, all while maintaining a strong focus on patient-centered outcomes. Postoperatively, DALK's lower rejection rates and decreased complications underscore its potential superiority over PK, although unique challenges such as graft failure from nonimmunologic factors demand vigilant management. This comprehensive review not only serves as a valuable resource for ophthalmic surgeons but also sheds light on the evolving landscape of corneal transplantation, highlighting DALK's role as a transformative force in the field.

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

PURPOSE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Double-Docking Technique for Femtosecond Laser-Assisted Deep Anterior Lamellar Keratoplasty: A Retrospective Consecutive Case Series Study of Advanced Keratoconus

PURPOSE

The aim of this study was to report the clinical outcomes and prognosis of femtosecond laser (FSL)-assisted double-docking deep anterior lamellar keratoplasty (DD-DALK) for advanced keratoconus (AK).

METHODS

Records of consecutive patients with keratoconus who underwent FSL-assisted DALK (DD-DALK) were reviewed.

RESULTS

We analyzed 37 eyes from 37 patients who underwent DD-DALK. Sixty-eight percent of eyes had a successful big-bubble formation and 27% had a manual dissection to achieve the DALK deep dissection. Stromal scarring was associated with not achieving a big bubble. Intraoperative conversion to penetrating keratoplasty was conducted in 2 cases (5%). The best-corrected visual acuity improved from a median (± interquartile range) of 1.55 ±0.25 logMAR preoperatively to 0.2 ±0.2 logMAR ( P < 0.0001). The median postoperative spherical equivalent was -5.75 ±2.75 D with a median astigmatism of -3.5 ±1.3 D. BCVA, SE, and astigmatism were not statistically different between patients who underwent DD-DALK and patients who underwent manual DALK. Stromal scarring was associated with big-bubble (BB) formation failure ( P = 0.003). All patients with failed BB requiring manual dissection had anterior stromal scarring.

CONCLUSIONS

DD-DALK is safe and reproducible. The success rate of BB formation is hampered by stromal scarring.

A deep learning approach for successful big-bubble formation prediction in deep anterior lamellar keratoplasty

The efficacy of deep learning in predicting successful big-bubble (SBB) formation during deep anterior lamellar keratoplasty (DALK) was evaluated. Medical records of patients undergoing DALK at the University of Cologne, Germany between March 2013 and July 2019 were retrospectively analyzed. Patients were divided into two groups: (1) SBB or (2) failed big-bubble (FBB). Preoperative images of anterior segment optical coherence tomography and corneal biometric values (corneal thickness, corneal curvature, and densitometry) were evaluated. A deep neural network model, Visual Geometry Group-16, was selected to test the validation data, evaluate the model, create a heat map image, and calculate the area under the curve (AUC). This pilot study included 46 patients overall (11 women, 35 men). SBBs were more common in keratoconus eyes (KC eyes) than in corneal opacifications of other etiologies (non KC eyes) (p = 0.006). The AUC was 0.746 (95% confidence interval [CI] 0.603–0.889). The determination success rate was 78.3% (18/23 eyes) (95% CI 56.3–92.5%) for SBB and 69.6% (16/23 eyes) (95% CI 47.1–86.8%) for FBB. This automated system demonstrates the potential of SBB prediction in DALK. Although KC eyes had a higher SBB rate, no other specific findings were found in the corneal biometric data.

Re-Endothelialization of Bare Stroma after Descemet's Detachment due to Macroperforation during Deep Anterior Lamellar Keratoplasty

Purpose

To report a case with spontaneous re-endothelialization of bare stroma after subtotal detachment of Descemet's membrane (DM) due to macroperforation during deep anterior lamellar keratoplasty (DALK).

Methods

Case report.

Results

A 64-year-old patient underwent DALK for deep stromal scarring secondary to herpetic keratitis. During manual dissection, DM macroperforation occurred, and this was successfully managed intraoperatively and postoperatively. The DM with host posterior stroma remained attached for 10 months when it detached from the bare donor stroma. The cornea remained clear, with uncorrected distance visual acuity (UCVA) of 0.17 logMAR. After graft suture removal 30 months later, he was noted to have regular astigmatism and cataract for which he underwent phacoemulsification with toric intraocular lens implantation. Twenty-four months following his cataract surgery and 58 months following his DALK, his UCVA remains 0.17 logMAR and the cornea remains clear with no evidence of edema. His average specular count at 58 months was 1296 cell/mm² .

Conclusion

This case shows a very good visual outcome with clear cornea at 58 months despite of large DM detachment which happened 10 months following manual DALK with intraoperative macroperforation.

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

PURPOSE

To identify predictors of bubble formation and type during big-bubble deep anterior lamellar keratoplasty (BB-DALK) performed in keratoconus at different stages of severity.

DESIGN

Retrospective Cohort Study.

METHODS

Setting: University Magna Græcia (Catanzaro, Italy); Study Population: Consecutive keratoconus patients undergoing BB-DALK from September 2014 to February 2019.

OBSERVATION PROCEDURE

Keratometric astigmatism, mean keratometry value (K-mean), highest keratometry value (K-max), thinnest point, anterior segment optical coherence tomography (AS-OCT)-based stage of ectasia.

MAIN OUTCOME MEASURES

Rate of bubble formation and type; number and fate of micro-/macroperforation; conversion to mushroom keratoplasty (MK); comparison of parameters in patients with bubble formation vs failure and in type 1 vs type 2 bubble; areas under the curves (AUC) of preoperative parameters for distinguishing between bubble types.

RESULTS

Pneumatic dissection succeeded in 113 of 155 eyes (72.9%), with 100 type 1 bubbles (88.4%), 11 type 2 (9.8%), and 2 mixed-type (1.8%). Microperforations were managed conservatively in type 1 bubbles; macroperforations occurring in both types of bubbles required conversion to MK. Preoperative K-mean and K-max values were significantly higher in eyes in which bubble formation succeeded (respectively, P = .006 and P < .013). Type 1 bubbles formed in eyes with significantly lower age, K-mean, and AS-OCT stages and higher pachymetric values (always P < .029). Age had the highest diagnostic power for discrimination between bubble types, followed by AS-OCT stage, pachymetry, K-mean, and astigmatism (respectively, AUC = 0.861, 0.779, 0.748, 0.700, 0.670).

CONCLUSIONS

Older age and advanced stages of keratoconus were predictors of type 2 bubble formation during BB-DALK that was associated with an increased risk of complications.

Approaches toward enhancing survival probability following deep anterior lamellar keratoplasty

The greatest advantage of deep anterior lamellar keratoplasty over full-thickness corneal transplantation is the elimination of graft failure caused by endothelial rejection. Despite this advantage, a deep anterior lamellar keratoplasty graft can fail because of several factors, such as complications related to the donor-recipient interface, graft epithelial abnormalities, graft vascularization, stromal graft rejection, and recurrence of herpetic keratitis. Increased deep anterior lamellar keratoplasty graft survival is mainly built upon optimization of the ocular surface to provide a hospitable environment for the graft. Any predisposing factors for graft epithelial abnormalities, corneal neovascularization, and preexisting vernal keratoconjunctivitis should be identified and treated preoperatively. Prompt recognition and appropriate treatment of interface-related complications and stromal graft rejection usually result in good anatomic outcomes, with no detrimental effects on vision.

Predictive Factors for Successful Type 1 Big Bubble during Deep Anterior Lamellar Keratoplasty

Objective

Big bubble (BB)-deep anterior lamellar keratoplasty (DALK) has become the reference transplantation technique for corneal stromal disorders. Type 1 BB is the desired aspect but it is not constant. We aimed to determine the predictive factors of type 1 BB success.

Methods

Observational cohort study including 77 consecutive eyes of 77 patients undergoing DALK by one surgeon at a single reference center without any selection. Clinical and spectral domain optical coherence tomography data were collected pre- and postoperatively.

Results

Stromal scars were found in 91.8% of cases and were located in the anterior (90.9%), mid (67.5%), and posterior (36.4%) stroma. Type 1 BB (49.3% of cases) was significantly associated with the absence of scars in the posterior stroma, stage 1-3 keratoconus, and deep trephination. Among eyes with posterior scars, type 1 BB was associated with higher minimal corneal thickness, maximum-minimum corneal thickness < 220 μm, and diagnosis other than keratoconus. Eyes with type 1 BB featured significantly thinner residual stromal bed (22 ± 8 µm versus 61 ± 28 µm), thinner corneas at 12, 24, and 36 months, and better visual acuity at 12 months compared with eyes with no type 1 BB. Conversely, no significant differences between both groups were observed for graft survival, visual acuity at 24 and 36 months, and endothelial cell density at 12 and 36 months.

Conclusion

OCT assessment before DALK is useful for choosing trephination depth that should be as deep as possible and for looking for posterior scars. The BB technique may not be the most appropriate method in keratoconus with posterior scars. Follow-up data do not support the need for conversion to penetrating keratoplasty when type 1 BB cannot be obtained nor does it support the need for performing a penetrating keratoplasty as a first-choice procedure in eyes with posterior stromal scars.

Outcome of deep anterior lamellar keratoplasty patients with intraoperative Descemet's membrane perforation: A retrospective cross-sectional study

PURPOSE

To evaluate functional and anatomical outcome in patients undergoing deep anterior lamellar keratoplasty (DALK) with intraoperative Descemet's membrane (DM) perforation (macro and micro).

METHODS

A retrospective cross sectional study (January 2009 to December 2015) of sixteen eyes of sixteen patients which included nine patients of advanced keratoconus (KC), two patients with paracentral DM scarring post hydrops, KC with Bowman's membrane scarring, macular corneal dystrophy and one patient of advanced Pellucid Marginal Degeneration (PMD). All underwent DALK with intraoperative DM perforation. Big bubble technique was attempted in all except in the two patients with post hydrops DM scar. Preoperative and postoperative best corrected visual acuity (BCVA), astigmatism and endothelial count (EC) were compared.

RESULTS

Postoperative BCVA and astigmatism were found to be better and statistically significant ('p value' 0.00 and 0.003 respectively). BCVA preoperative and postoperative was 1.07± 0.3 and 0.28 ± 0.09 in LogMAR respectively and astigmatism pre and postoperative 4.14 ± 1.5 D and 2.7 ± 0.97 D respectively. Percentage decrease in EC at sixth postoperative week was 7.48% and at sixth month and 1 year postoperative was 15.1%. Two patients developed postoperative double anterior chamber and two patients developed pupillary block glaucoma and all were successfully managed.

CONCLUSION

Not all patients of intraoperative DM perforation (including macro perforation) needs to be converted to penetrating keratoplasty. DALK can be successfully done if the perforation is identified early and managed adequately. This is the only known study which has shown a large series of successful DALK even with macro perforations.

Deep anterior lamellar keratoplasty: A surgeon's guide

Purpose

To review and highlight important practical aspects of deep anterior lamellar keratoplasty (DALK) surgery and provide some useful tips for surgeons wishing to convert to this procedure from the conventional penetrating keratoplasty (PK) technique.

Methods

In this narrative review, the procedure of DALK is described in detail. Important pre, intra, and postoperative considerations are discussed with illustrative examples for better understanding. A comprehensive literature review was conducted in PubMed/Medline from January 1995 to July 2017 to identify original studies in English language regarding DALK. The primary endpoint of this review was the narrative description of surgical steps for DALK, its pitfalls, and management of common intraoperative complications.

Results

A standard DALK procedure can be successfully performed taking into consideration factors such as age, ophthalmic co-morbidities, status of the crystalline lens, retina, and intraocular pressure. Careful trephination and dissection of the host cornea employing appropriate technique (such as big bubble technique, manual dissection, visco-dissection, etc.) suitable for the specific case is important to achieve good postoperative outcomes. Prompt identification of intraoperative complications such as double bubble, micro and macroperforations, etc. are vital to change the management strategies.

Conclusion

Although there is a steep learning curve for DALK procedure, considering details and having insight into the management of intraoperative issues facilitates learning and reduces complication rates.