Effect of corneal cross-linking on biomechanical changes following transepithelial photorefractive keratectomy and femtosecond laser-assisted LASIK.

Purpose: To evaluate the change in corneal biomechanics in patients with postoperative ectasia risk when combining two common laser vision correction procedures (tPRK and FS-LASIK) with cross-linking (in tPRK Xtra and FS-LASIK Xtra). Methods: The study included 143 eyes of 143 myopic, astigmatic patients that were divided into non-cross-linked refractive surgery groups (non-Xtra groups, tPRK and FS-LASIK) and cross-linked groups (Xtra groups, tPRK Xtra and FS-LASIK Xtra) according to an ectasia risk scoring system. The eyes were subjected to measurements including the stress-strain index (SSI), the stiffness parameter at first applanation (SP-A1), the integrated inverse radius (IIR), the deformation amplitude at apex (DA), and the ratio of deformation amplitude between apex and 2 mm from apex (DARatio2mm). The measurements were taken preoperatively and at 1, 3, and 6 months postoperatively (pos1m, pos3m, and pos6m). Posterior demarcation line depth from the endothelium (PDLD) and from the ablation surface (DLA) were recorded at pos1m. Results: SP-A1 significantly decreased, while IIR, deformation amplitude, and DARatio2mm increased significantly postoperatively in all four groups (p < 0.01)-all denoting stiffness decreases. In the FS-LASIK group, the changes in IIR, DA, and DARatio2mm were 32.7 ± 15.1%, 12.9 ± 7.1%, and 27.2 ± 12.0% respectively, which were significantly higher (p < 0.05) compared to 20.1 ± 12.8%, 6.4 ± 8.2%, and 19.7 ± 10.4% in the FS-LASIK Xtra group. In the tPRK group, the change in IIR was 27.3 ± 15.5%, significantly larger than 16.9 ± 13.4% in the tPRK Xtra group. The changes of SSI were minimal in the tPRK (-1.5 ± 21.7%, p = 1.000), tPRK Xtra (8.4 ± 17.9%, p = 0.053), and FS-LASIK Xtra (5.6 ± 12.7%, p = 0.634) groups, but was significant in the FS-LASIK group (-12.1 ± 7.9%, p < 0.01). After correcting for baseline biomechanical metrics, preoperative bIOP and the change in central corneal thickness (△CCT) from pre to pos6m, the changes in the IIR in both FS-LASIK and tPRK groups, as well as DA, DARatio2mm and SSI in the FS-LASIK group remained statistically greater than their corresponding Xtra groups (all p < 0.05). Most importantly, after correcting for these covariates, the changes in DARatio2mm in the FS-LASIK Xtra became statistically smaller than in the tPRK Xtra (p = 0.017). Conclusion: The statistical analysis results indicate that tPRK Xtra and FS-LASIK Xtra effectively reduced the biomechanical losses caused by refractive surgery (tPRK and FS-LASIK). The decrease in corneal overall stiffness was greater in FS-LASIK than in tPRK, and the biomechanical enhancement of CXL was also higher following LASIK than after tPRK.

Cranioplasty for Skull Defects With Polypropylene Abdominal Wall Mesh.

OBJECTIVE: Cranioplasty is a well-established common surgery in the practice of neurosurgery and craniofacial surgery. In young patients, complete skull defect closure by bone splitting may be troublesome due to the difficulty to obtain enough bone area. In such cases, sometimes the authors need to use allografts, which may not be widely available in rural practice. In this study, the authors present the series of cranioplasty with polypropylene mesh, which is widely used in abdominal wall closure. PATIENTS AND METHODS: Nine patients with depressed compound skull fracture were treated by performing this technique. Selection criteria were: compound depressed skull fractures in which bones were fragmented in a way not able to be reconstructed with and leaving a skull defect, small-sized or relatively medium-sized skull defects, and skull defects not located on the sharp curvatures of the skull which needs firm bended meshes. All patients were male and their ages ranged between 8 months and 36 years.The skull bone defect was reconstructed with polypropylene abdominal wall mesh, which was sutured circumferentially with the galeal tissue. RESULTS: Skull defects were successfully treated in all patients. The follow-up period ranged from 4 to 13 months. One patient with a history of alcoholism and neglectance developed a wound infection after 3 weeks of surgery. This patient was treated successfully with intravenous antibiotics without the need to remove the mesh. There were no complications in the remaining 8 patients. CONCLUSIONS: Polypropylene mesh is a cheap and effective material for the reconstruction of small-sized or medium-sized skull defects. It can be a good alternative in rural practice and/or low economic communities, when other cranioplasty materials are not available.

Long-term Effects of Riboflavin Ultraviolet-A-Induced CXL With Different Irradiances on the Biomechanics of In Vivo Rabbit Corneas.

PURPOSE: To evaluate the long-term effects of ultraviolet-A corneal cross-linking (CXL) with different irrandiances on the biomechanical properties of rabbit corneas and the corresponding changes in stromal microstructure. METHODS: The study involved the left eyes of 85 healthy white Japanese rabbits, randomly divided into five groups (n = 16 to 18 each). After removing the epithelium, the first four groups were exposed to riboflavin (0.22% concentration by volume) and ultraviolet-A (370 nm) at different CXL irradiations but with the same total dose (5.4 J/cm2). The four groups were defined as standard CXL (SCXL; 3 mW/cm2 for 30 minutes, n = 17), accelerated CXL1 (ACXL1; 9 mW/cm2 for 10 minutes, n = 16), accelerated CXL2 (ACXL2; 18 mW/cm2 for 5 minutes, n = 17), and accelerated CXL3 (ACXL3; 30 mW/cm2 for 3 minutes, n = 17). The control group (n = 18) was treated with riboflavin without ultraviolet-A exposure. Nine months after CXL, 10 corneas from each group were tested ex vivo under inflation, and the tangent modulus (Et) was estimated using an inverse analysis process. The remaining six to eight specimens in each group were examined by electron microscopy to determine the mean fibril diameter and interfibrillar spacing. RESULTS: The SCXL and ACXL1 groups showed statistically significant differences in Et at all stresses (0.005, 0.010, and 0.015 MPa) analyzed compared to the control group (all P < .01), but the differences were non-significant in the ACXL3 group (P = 1.000, .785, and .679, respectively). For the ACXL2 group, there was no statistical difference in Et under the low stress of 0.005 MPa (P = .155), but the differences became significant at 0.010 and 0.015 MPa when compared with the control group (all P < .05). CONCLUSIONS: CXL had a significant effect on corneal biomechanics in both standard and accelerated procedures. However, standard CXL was the most effective, and this effectiveness decreased gradually with increasing ultraviolet-A power intensity. [J Refract Surg. 2022;38(6):389-397.].

Effect of Mydriasis-Caused Intraocular Pressure Changes on Corneal Biomechanical Metrics.

Purpose: To evaluate the dependence of biomechanical metrics on intraocular pressure (IOP). Methods: 233 refractive surgery patients were included in this study-all were examined 3 times with the Corvis ST before and after dilation, and the differences (∆) in the main device parameters were assessed. The data collected included the biomechanically corrected IOP (bIOP), the central corneal thickness (CCT), and six dynamic corneal response (DCR) parameters, namely DA, DARatio2mm, IIR, SP-A1, CBI, and SSI. Participants were divided into three groups according to the changes in patients' bIOP after mydriasis. Results: Intra-operator repeatability was generally high in most of the DCR parameters obtained before and after dilation. The mean changes in bIOP and CCT after dilation were -0.12 ± 1.36 mmHg and 1.95 ± 5.23 µm, respectively. Only ∆DARatio2mm, ∆IIR, and ∆CBI exhibited a statistically significant correlation with ∆CCT (p < 0.05). The changes in all DCR parameters, especially ∆DA and ∆SP-A1 were also correlated with ∆bIOP (p < 0.01)-a 1-mmHg change in bIOP was associated, on average, with 5.612 and -0.037 units of change in SP-A1 and DA, respectively. In contrast, the weakest correlation with ∆bIOP was exhibited by ∆SSI. Conclusion: Most corneal DCR parameters, provided by the Corvis ST, were correlated with IOP, and more weakly with CCT. Changes experienced in CCT and IOP should therefore be considered in studies on corneal biomechanics and how it is affected by disease progression and surgical or medical procedures.

Cranioplasty for Skull Defect With Polypropylene Abdominal Wall Mesh.

ABSTRACT: Cranioplasty is a routine procedure in the practice in neurosurgery and craniofacial surgery. For the closure of the cranial defect, it may be difficult or impossible to split the bone sufficiently to obtain enough bone for complete closure of the defect in younger children. Thus, sometimes there is the need to use allografts, which may not be widely available in rural practice. We present 2 cases of cranioplasty with widely available and used polypropylene abdominal wall mesh. To add rigidity to the construct, the mesh was organized in a multilayered fashion. Postoperative follow-up showed good functional and cosmetic results.

Primary Posterior Fossa Hydatid Cyst in a Child.

ABSTRACT: A 7-year-old boy referred to our emergency department complaining of headache, nausea, vomiting, dizziness, generalized fatigue, ataxia and diplopia. Neurological exam showed bilateral papilledema and ataxic gait. Routine blood test, plain chest x-ray and abdominal ultrasonography were normal. Brain computed tomography (CT) scan and magnetic resonance imaging (MRI) revealed well-defined intra-axial unilocular cystic lesion in the left cerebellar hemisphere, causing mass effect on brain stem and fourth ventricle with associated tonsillar herniation and mild obstructive hydrocephalus. The authors started the treatment with Albendazole and the patient was operated with left sub-occipital craniotomy. Cyst was delivered with intact capsule. Postoperative period was uneventful and patient's symptoms improved totally after 1 week. Histopathologic examination confirmed the diagnosis of hydatid cyst.

Castleman Disease: An Unusual Cause of an Isolated Neck Mass.

ABSTRACT: A 15-year old female patient was complaining from swelling in the left side of the neck since 3 months. Physical examination showed palpable and mobile left supraclavicular neck mass in the carotid triangle, uvula deviation to the left side and normal vocal cords position and function. Neck imagings showed well-defined, well-encapsulated left neck mass in the left carotid sheath pushing the internal jugular vein anteriorly and the common carotid artery posteriorly. The mass was extending from the level of C4 superiorly and the supraclavicular region inferiorly. Patient was operated with left anterior approach and circumferential dissection and enucleation was performed. Post-operative period was uneventful and devoid of any complications or deficits. Histopathological examination revealed Castleman disease.

Extra-axial cerebellopontine angle cavernoma: A case report and review of literature.

BACKGROUND: Extra-axial cavernomas at the cerebellopontine angle (CPA) are rare clinical entity that can radiologically mimic several lesions encountered at this location. CASE DESCRIPTION: A 36-year-old female patient referred to our emergency service with acute decreased level of consciousness and vomiting. Neurological examination showed Glasgow Coma Scale of 12 with downbeat nystagmus of the right eye. Brain computed tomography scan and magnetic resonance imaging showed multilobulated extra-axial mass lesion located in the right CPA. The lesion was with various signal intensities in T1- and T2-weighted images suggestive of hemorrhages of different ages. T2 gradient echo sequences showed multiple sinusoid-like channels and diffuse hemosiderin deposition. These figures were compatible with cavernous malformation. The patient was operated by retrosigmoid approach. Dissection of the mass from the trigeminal, facial, vestibulocochlear, and lower cranial nerves was performed and total resection of the tumor was achieved. Histopathological examination confirmed the diagnosis of cavernoma. CONCLUSION: Although CPA cavernomas are very rare, they should be considered for differential diagnosis when evaluating CPA lesions preoperatively for better intraoperative management and postoperative outcomes.