Iterative Methods for the Biomechanical Evaluation of Corneal Response. A Case Study in the Measurement Phase

the number of corneal surgeries steadily grew in recent years and boosted the development of corneal biomechanical models. These models can contribute to simulating surgery by reducing associated risks and the need for secondary interventions due to ectasias or other problems related to correcting other diseases. Biomechanical models are based on the geometry obtained with corneal topography, which is affected by intraocular pressure and material properties. Knowledge of stress distribution in the measurement phase is a key factor for improving the accuracy of in silico mechanical models. In this work, the results obtained by two different methods: prestress method and displacements method were compared to evaluate the stress and strain distribution in a general geometric model based on the Navarro eye geometry and two real corneal geometries. The results show that both methods are equivalent for the achievement of the stress distribution in the measurement phase. Stress distribution over the corneal geometry in the measurement phase is a key factor for accurate biomechanical simulations, and these simulations could help to develop patient-specific models and reduce the number of secondary interventions in clinical practice.

Analysis of Outcomes After Endovascular Abdominal Aortic Aneurysm Repair in Patients With Abnormal Findings on the First Postoperative Computed Tomography Angiography

Purpose: Lifelong follow-up after endovascular abdominal aortic aneurysm repair (EVAR) is recommended due to a continued risk of complications, especially if the first postoperative imaging shows abnormal findings. We studied the long-term outcomes in patients with abnormalities on the first postoperative computed tomography angiography (CTA) following EVAR. Materials and Methods: This is a retrospective study of all consecutive patients who underwent elective EVAR for nonruptured abdominal aortic aneurysm (AAA) between January 2007 and January 2012 in 16 Dutch hospitals with follow-up until December 2018. Patients were included if the first postoperative CTA showed one of the following abnormal findings: endoleak type I–IV, endograft kinking, infection, or limb occlusion. AAA diameter, complications, and secondary interventions during follow-up were registered. Primary endpoint was overall survival, and other endpoints were secondary interventions and intervention-free survival. Kaplan-Meier analyses were used to estimate overall and intervention-free survival. Cox regression analyses were used to identify the association of independent determinants with survival and secondary interventions. Results: A total of 502 patients had abnormal findings on the first postoperative CTA after EVAR and had a median follow-up (interquartile range IQR) of 83.0 months (59.0). The estimated overall survival rate at 1, 5, and 10 years was 84.7%, 51.0%, and 30.8%, respectively. Age [hazard ratio (HR) 1.06, 95% confidence interval (CI) 1.05 to 1.10] and American Society of Anesthesiologists (ASA) classification (ASA IV HR 3.20, 95% CI 1.99 to 5.15) were significantly associated with all-cause mortality. Overall, 167 of the 502 patients (33.3%) underwent 238 secondary interventions in total. Fifty-eight patients (12%) underwent an intervention based on a finding on the first postoperative CTA. Overall survival was 38.4% for patients with secondary interventions and 44.5% for patients without (log rank; p=0.166). The intervention-free survival rate at 1, 5, and 10 years was 82.9%, 61.3%, and 45.6%, respectively. Conclusions: Patients with abnormalities on the first postoperative CTA after elective EVAR for infrarenal AAA cannot be discharged from regular imaging follow-up due to a high risk of secondary interventions. Patients who had a secondary intervention had similar overall survival as those without secondary interventions.

Open Surgical Secondary Interventions are More Durable than Endovascular Interventions for Lower Extremity Bypass Stenosis or Occlusion

Objectives: Lower extremity bypasses often require secondary interventions to maintain patency. Our objectives were to characterize effectiveness of secondary interventions to maintain or restore bypass graft patency, and to compare outcomes of open and endovascular interventions. Methods: We reviewed patients who underwent lower extremity bypass at our institution from 2007 to 2010. We recorded the index bypass and subsequent ipsilateral interventions performed through 2018 or until loss of secondary patency. Patient, procedure, and anatomic data were collected. Endovascular intervention was compared with open/hybrid intervention. For outcome analysis, patency measures were defined relative to the time of the secondary intervention rather than the time of the index bypass. Results: 174 secondary interventions (56 open/hybrid, 118 endovascular; 42 for graft occlusion, and 132 for stenosis) treating 228 lesions in 97 bypasses were available for study. The index bypass was most commonly performed for tissue loss (71.1%), utilized a tibial artery target (57.7%), and used single-segment great saphenous vein (59.8%) rather than alternative vein (32.0%) or prosthetic (8.2%). A higher portion of open/hybrid interventions (51.8%) were done for graft occlusion than endovascular interventions (11.0%, P < .001). Mean follow-up for secondary interventions was 3.5 years. A multivariate Cox proportional hazards model identified female gender, prior MI, anticoagulation, occlusion, and endovascular intervention as predictors of loss of primary patency. Intervention for occlusion predicted poorer primary and secondary patency. Endovascular intervention was associated with poorer primary patency as compared to open intervention and a trend toward poorer secondary patency. Conclusions: Both open and endovascular secondary interventions on lower extremity bypasses are low-risk procedures that offer acceptable patency. Although more commonly performed in the setting of graft occlusion, open surgical interventions show improved durability compared to endovascular interventions. Some patients, including those with occluded grafts, may benefit from more liberal use of open surgical intervention to restore bypass patency.

Graft detachments in endothelial keratoplasty

Graft detachment is the most common complication of endothelial keratoplasty. With the ongoing advancements in the field of endothelial keratoplasty, our understanding of risk factors of graft detachments and its management has been evolving. Various prevention measures have been described in literature including presoaking the donor graft, anterior chamber tamponade, venting incisions, sutures to prevent dislocation of graft. Management of a detached graft involves secondary interventions such as rebubbling, suturing and regrafts. In this review, we discuss graft detachment in different types of endothelial keratoplasty techniques including Descemet stripping endothelial keratoplasty, Descemet stripping automated endothelial keratoplasty and Descemet’s membrane endothelial keratoplasty; with emphasis on incidence, risk factors, preventive measures and their management.

Nellix endovascular aneurysm-sealing system: a single-center experience and review of current evidence

Aims: We report the 6-year results of our use of the Nellix® endovascular aneurysm sealing system. Materials & methods: This is a retrospective review of patients we treated from 2013 to 2019. The outcomes described include technical success rate, mortality, all procedure-related complications, reinterventions, open surgical conversion and secondary sac rupture. Results & conclusions: A total of 68 patients were treated. Mortality was 2.9%. Secondary interventions were carried out for distal embolization (3), stent occlusion (1), pseudoaneurysm (1) and endoleak (5). Open surgical conversion was required in 6.4% of cases. Medium- and long-term complications of EVAS occurred more frequently than expected. Because the durability of endovascular aneurysm sealing is questionable, strict postoperative surveillance of Nellix is crucial to identify features of failure.

Exact matching of trabectome-mediated ab interno trabeculectomy to conventional trabeculectomy with mitomycin C followed for 2 years

Purpose We used exact matching for a highly balanced comparison of ab interno trabeculectomy (AIT) with the trabectome to trabeculectomy with mitomycin C (TRAB). Methods A total of 5485 patients who underwent AIT were exact-matched to 196 TRAB patients by baseline intraocular pressure (IOP), number of glaucoma medications, and glaucoma type. Nearest-neighbor–matching was applied to age. Success was defined as a final IOP of less than 21 mmHg, IOP reduction of at least 20% reduction from baseline, and no secondary surgical interventions. Outcomes were measured at 1, 3, 6, 12, 18, and 24 months. Results A total of 165 AIT could be matched to 165 TRAB. The mean baseline IOP was 22.3 ± 5.6 mmHg, and the baseline number of glaucoma medications was 2.7 ± 1.1 in both groups. At 24 months, IOP was reduced to 15.8 ± 5.2 mmHg in AIT and 12.4 ± 4.7 mmHg in TRAB. IOP was lower than baseline at all visits (p < 0.01) and lower in TRAB than AIT (p < 0.01). Glaucoma medications were reduced to 2.1 ± 1.3 in AIT and 0.2 ± 0.8 in TRAB. Compared to baseline, patients used fewer drops postoperatively (p < 0.01) and more infrequently in TRAB than in AIT (p > 0.01). Secondary surgical interventions had the highest impact on success and became necessary in 15 AIT and 59 TRAB patients. Thirty-two challenging events occurred in TRAB and none in AIT. Conclusion Both AIT and TRAB reduced IOP and medications. This reduction was more significant in TRAB but at the expense of four times as many secondary interventions.