Turning the operating room into a mixed-reality environment: a prospective clinical investigation for cerebral aneurysm clipping.

OBJECTIVE: The overall aim of this study was to demonstrate the potential benefit of a novel mixed-reality-head-mounted display (MR-HMD) on the spatial orientation of surgeons. METHODS: In a prospective clinical investigation, the authors applied for the first time a new multicamera navigation technology in an operating room setting that allowed them to directly compare MR-HMD navigation to standard monitor navigation. In the study, which included 14 patients with nonruptured middle cerebral artery aneurysms, the authors investigated how intuitively and effectively surgical instruments could be guided in 5 different visual navigation conditions. RESULTS: The authors demonstrate that multicamera tracking can be reliably integrated in a clinical setting (usability score 1.12 ± 0.31). Moreover, the technology captures large volumes of the operating room, allowing the team to track and integrate different devices and instruments, including MR-HMDs. Directly comparing mixed-reality navigation to standard monitor navigation revealed a significantly improved intuition in mixed reality, leading to navigation times that were twice as fast (2.1×, p ≤ 0.01). Despite the enhanced speed, the same targeting accuracy (approximately 2.5 mm, freehand tool use) in comparison to monitor navigation could be observed. Intraoperative planning strategies with mixed reality clearly outperformed classic preoperative planning: surgeons scored the mixed-reality plan as the best trajectory in 63% of the cases (chance level 33%). CONCLUSIONS: The incorporation of mixed reality in neurosurgical operations marks a significant advancement in the field. The use of mixed reality in brain surgery enhances the spatial awareness of surgeons, enabling more instinctive and precise surgical interventions. This technological integration promises to refine the execution of complex procedures without compromising accuracy.

Stromal remodeling and lenticule thickness accuracy in small-incision lenticule extraction: One-year results.

PURPOSE: To prospectively characterize the stromal thickness changes during the first year after myopic small-incision lenticule extraction using spectral-domain optical coherence tomography (SD-OCT). SETTING: Department of Ophthalmology, Kepler University Hospital, Linz, Austria. DESIGN: Prospective case series. METHODS: This study evaluated eyes that had small-incision lenticule extraction to treat myopia or myopic astigmatism. A high-resolution SD-OCT system (RS 3000 Advance) in conjunction with a custom image-segmentation algorithm was applied to directly measure stromal thickness within the central 5.0 mm corneal zone. Measurements were obtained preoperatively and postoperatively at 1 day, 1 week, 6 weeks, 3 months, 6 months, and 1 year. RESULTS: The study enrolled 42 eyes of 21 patients. The mean surgical refractive correction was -4.94 diopters ± 1.75 (SD). Postoperatively, the stromal thickness showed a significant decrease during the first 6 weeks, which amounted to a mean of 10.4 ± 6.3 µm at the apex (P < .001). Subsequently, the central stroma thickened by a mean of 8.8 ± 5.9 µm up until the 1-year follow-up (P < .001). One year postoperatively, the mean observed central stromal thickness reduction was 18.7 ± 5.7 µm smaller than the planned lenticule thickness. This difference was smallest 6 weeks postoperatively (mean 9.8 ± 7.8 µm). CONCLUSIONS: Significant anatomic changes in the corneal stroma were detected during the first year after small-incision lenticule extraction. The achieved lenticule thickness was systematically lower than planned, and the mismatch was more pronounced with higher lenticule thickness. Refractive outcomes did not appear to be influenced by lenticule thickness accuracy.

Corneal Epithelial Remodeling Induced by Small Incision Lenticule Extraction (SMILE).

PURPOSE: To assess the reactive changes of the corneal epithelial thickness (ET) profile induced by small incision lenticule extraction (SMILE) for treatment of myopia. METHODS: This prospective observational study included 46 eyes of 23 patients that were scheduled for myopic SMILE. High-resolution spectral-domain optical coherence tomography (SD-OCT) and a custom image segmentation algorithm were applied to measure corneal ET at multiple time points within the central 5-mm zone. Postoperative ET alterations were correlated with treatment parameters and refractive outcomes. RESULTS: Mean age was 33 ± 6 years and mean spherical equivalent of surgical refractive correction was -4.78 ± 1.75 diopters. The average ET (averaged over the central 5-mm zone) increased from 52.3 ± 3.6 µm preoperatively to 57.7 ± 5.1 µm 6 months postoperatively (P < 0.01). Average ET was 101.9% of the preoperative thickness at 24 hours postoperatively, 103.2% at 1 week, 106.7% at 6 weeks, 109.3% at 3 months, and 110.4% at 6 months postoperatively. The epithelial thickening response could be modeled by an exponential recovery function and stabilized after 3 months. The extent of epithelial hyperplasia was highly dependent on the magnitude of the induced refractive correction (P = 0.002). CONCLUSIONS: In this initial study of corneal ET remodeling after myopic SMILE, significant epithelial thickening was detected as a function of the extent of surgical refractive correction. Moreover, the epithelial remodeling response to the corneal refractive change appeared to decrease with higher age. In our hands, the observed epithelial changes did not appear to affect the refractive outcome of SMILE. (ClinicalTrials.gov number, NCT02614625).

Semiautomated SD-OCT Measurements of Corneal Sublayer Thickness in Normal and Post-SMILE Eyes.

PURPOSE: To test the reliability of a novel algorithm for measuring corneal epithelial thickness (ET) and stromal thickness of normal eyes and post-small incision lenticule extraction (SMILE) corneas with spectral-domain optical coherence tomography. METHODS: In this prospective observational study, a customized semiautomated software algorithm was developed and applied to measure corneal ET and stromal thickness along the horizontal corneal meridian. Measurements were performed by 2 examiners in a randomized fashion on a sample of 40 eyes with previous SMILE for treatment of myopia and a control group composed of 40 normal eyes. The intrauser repeatability and interuser reproducibility were analyzed by calculating typical indices including the coefficient of variation and intraclass correlation coefficient. Corneal sublayer thickness profiles were compared between normal and post-SMILE eyes. RESULTS: In both groups, coefficients of variation were 3.2% or lower and intraclass correlation coefficients were 0.929 or higher indicating excellent reliability of the measurement method. Central ET was on an average 6 µm greater in post-SMILE corneas (58.8 ± 5.4 µm) compared with normal eyes (52.8 ± 4.0 µm), with P < 0.01. Also, there was greater interindividual variability in ET in post-SMILE corneas and their horizontal epithelial profile seemed to show a lenticular appearance. CONCLUSIONS: Highly favorable indices of measurement reliability were achieved for this novel method of measuring corneal sublayer pachymetry not only in normal eyes but also in eyes with previous SMILE. The corneal ET profile was significantly altered in post-SMILE eyes compared with normal corneas.

Introducing a new parameter for the assessment of the tear film lipid layer.

PURPOSE: The differential diagnosis of dry eye syndrome is still a challenging task. The purpose of this study was to understand the relationship between a novel, objective clinical parameter, the "corrected lipid layer stabilization time," and commonly performed clinical tests for dry eye patients. METHODS: Data were obtained from a prospective clinical study with 59 patients of different subjective severity, as determined with the Ocular Surface Disease Index (OSDI). The dynamics of the tear film lipid layer were made visible through a white light source and were stored digitally. Because the distance between the upper and lower eyelid affects the lipid layer dynamics and varies significantly between subjects, the distance of the eyelids was determined and used to correct the lipid layer stabilization time. The resulting parameter was compared with common clinical procedures. RESULTS: The corrected lipid layer stabilization time has a highly significant correlation with tear film breakup time (Spearman r = -0.485, P < 0.01), Schirmer test without anesthesia (r = -0.431, P < 0.01) and with the Ocular Surface Disease Index (r = 0.498, P < 0.01). It also correlates with the lissamine green staining score (r = 0.379, P < 0.05), but shows no correlation with the osmolarity of the tear film. Without the correction for the eyelid opening, the correlations decrease considerably. CONCLUSIONS: These data suggest that the diagnostic value of the lipid layer stabilization time for the assessment of the severity of dry eye syndrome increases considerably when it is corrected by the distance of the eyelids.