Correlation between Corneal Volume and Corneal Biomechanics and Corneal Volume Significance in Staging and Diagnosing Keratoconus.

Purpose: To investigate the relationship between corneal volume (CV) at different zones and corneal biomechanics in keratoconus (KC) along with the significance of CV in diagnosing and staging KC. Methods: This prospective clinical study included 456 keratoconic eyes (Group B) and 198 normal eyes (Group A). Using the topographic KC classification method, Group B was divided into subgroups based on severity (mild, moderate, and severe). The CVs of the 3 mm, 5 mm, and 7 mm zones and biomechanical parameters were obtained by Pentacam and Corvis ST. The diagnostic utility of multirange CVs at different disease stages and severity was determined using a receiver operating characteristic (ROC) curve analysis. Results: The CV of the 7-mm zone had the strongest correlation with A1V, A2T, PD, DA ratio max (2 mm), DA ratio max (1 mm), ARTh, integrated radius, SPA1, and CBI (p < 0.01). The CVs of the Group B subgroups were significantly lower than those of Group A for each diameter range (p < 0.05). There were significant differences between the severe, mild, and moderate subgroups for the 3 mm zone (p < 0.05, all). The 3 mm zone CV exhibited better diagnostic ability in each group for distinguishing KC from the normal cornea (Groups A vs. B: area under the ROC curve (AUC) = 0.926, Groups A vs. B1: AUC = 0.894, Groups A vs. B2: AUC = 0.925, Groups A vs. B3: AUC = 0.953). Conclusion: The CV significantly decreased in keratoconic eyes. Progressive thinning in the 3 mm zone may be a valuable measurement for detecting and staging KC. Combining the CV examination with corneal biomechanical information may effectively enhance the ability to detect KC.

Enhancing the Consistency and Performance of Graphene-Based Devices via Al Intermediate-Layer-Assisted Transfer and Patterning.

Graphene has garnered widespread attention, and its use is being explored for various electronic devices due to its exceptional material properties. However, the use of polymers (PMMA, photoresists, etc.) during graphene transfer and patterning processes inevitably leaves residues on graphene surface, which can decrease the performance and yield of graphene-based devices. This paper proposes a new transfer and patterning process that utilizes an Al intermediate layer to separate graphene from polymers. Through DFT calculations, the binding energy of graphene-Al was found to be only -0.48 eV, much lower than that of PMMA and photoresist with graphene, making it easier to remove Al from graphene. Subsequently, this was confirmed through XPS analysis. A morphological characterization demonstrated that the graphene patterns prepared using the Al intermediate layer process exhibited higher surface quality, with significantly reduced roughness. It is noteworthy that the devices obtained with the proposed method exhibited a notable enhancement in both consistency and sensitivity during electrical testing (increase of 67.14% in temperature sensitivity). The low-cost and pollution-free graphene-processing method proposed in this study will facilitate the further commercialization of graphene-based devices.

Biochemical component analysis of human myopic corneal stroma using the Raman spectrum.

PURPOSE: This study aimed to measure the Raman spectrum of the human corneal stroma lens obtained from small incision lenticule extraction surgery (SMILE) in Asian myopic eyes using a confocal Raman micro-spectrometer built in the laboratory. METHODS: Forty-three myopic patients who underwent SMILE with equivalent diopters between - 4.00 and - 6.00 D were selected, and the right eye data were collected. Corneal stroma lenses were obtained during surgery, and the Raman spectra were measured after air drying. The complete Raman spectrum of human myopic corneal stroma lens tissue was obtained within the range of 700-4000 cm-1. RESULTS: Thirteen characteristic peaks were found, with the stronger peaks appearing at 937 cm-1, corresponding to proline, valine, and the protein skeleton of the human myopic corneal stroma lens; 1243 cm-1, corresponding to collagen protein; 1448 cm-1, corresponding to the collagen protein and phospholipids; and 2940 cm-1, corresponding to the amino acid and lipids, which was the strongest Raman peak. CONCLUSION: These results demonstrated that Raman spectroscopy has much potential as a fast, cost-effective, and reliable diagnostic tool in the diagnosis and treatment of eye diseases, including myopia, keratoconus, and corneal infection.

Solid-State Emissive meso-Aryl/Alkyl-Substituted and Heteroatom-Mixed BOPPY Dyes: Syntheses, Structures, Physicochemical, Redox Properties, and Computational Analysis.

A series of solid-state emissive meso-aryl/alkyl-substituted and heteroatom-mixed bisBF2-anchoring fluorophore incorporating pyrrolyl-pyridylhydrazone (BOPPY) dyes have been developed by a one-pot condensation of ketonized or formylated pyrroles and 2-heterocyclohydrazine as well as the subsequent borylation coordination. Interestingly, the BOPPY dyes with meso-alkyl-substituted groups or oxygen-substituted pyridine moieties exhibit high fluorescence quantum yields (QYs) of up to 79%, the highest solid QY of 74%, and long lifetimes independent of polarity in the available BOPPYs. On the other hand, the BOPPYs with meso-aryl or N-substituted moieties display a high solution QY of up to 93% and slight emission wavelength maxima. However, the S-substituted BOPPY dye exhibited weak fluorescence in all studied solvents, which was attributed to the structural flexibility of the N-C-S bond and different from those BOPPYs with O or N substitution, indicated by quantum calculations. And the significant excited-state structural rearrangement in a polar solvent is further confirmed by femtosecond time-resolved transient absorption spectroscopy. More importantly, those novel and barely fluorescent BOPPYs in acetonitrile show advantageous aggregation-induced enhanced emission and viscosity-dependent activities. These advancements in the photophysical and electrochemical properties of BOPPY dyes offer valuable insights into their further development and potential applications.

Lipopolysaccharide-induced Trigeminal Ganglion Nerve Fiber Damage is Associated with Autophagy Inhibition.

OBJECTIVE: This study aimed to determine whether lipopolysaccharide (LPS) induces the loss of corneal nerve fibers in cultured trigeminal ganglion (TG) cells, and the underlying mechanism of LPS-induced TG neurite damage. METHODS: TG neurons were isolated from C57BL/6 mice, and the cell viability and purity were maintained for up to 7 days. Then, they were treated with LPS (1 µg/mL) or the autophagy regulator (autophibib and rapamycin) alone or in combination for 48 h, and the length of neurites in TG cells was examined by the immunofluorescence staining of the neuron-specific protein ß3-tubulin. Afterwards, the molecular mechanisms by which LPS induces TG neuron damage were explored. RESULTS: The immunofluorescence staining revealed that the average length of neurites in TG cells significantly decreased after LPS treatment. Importantly, LPS induced the impairment of autophagic flux in TG cells, which was evidenced by the increase in the accumulation of LC3 and p62 proteins. The pharmacological inhibition of autophagy by autophinib dramatically reduced the length of TG neurites. However, the rapamycin-induced activation of autophagy significantly lessened the effect of LPS on the degeneration of TG neurites. CONCLUSION: LPS-induced autophagy inhibition contributes to the loss of TG neurites.

Effect of Y-doping on switching mechanisms and impedance spectroscopy of HfOx-based RRAM devices.

Y-doping can effectively improve the performance of HfOx-based resistive random-access memory (RRAM) devices, but the underlying physical mechanism of Y-doping affecting the performance of HfOx-based memristors is still missing and unclear. Although impedance spectroscopy (IS) has been widely used to investigate impedance characteristics and switching mechanisms of RRAM devices, there is less IS analysis on Y-doped HfOx-based RRAM devices as well as devices at different temperatures. Here, the effect of Y-doping on the switching mechanism of HfOx-based RRAM devices with a Ti/HfOx/Pt structure were reported using current-voltage characteristics and IS. The results indicated that doping Y into HfOxfilms could decrease the forming/operate voltage and improve the RS uniform. Both doped and undoped HfOx-based RRAM devices obeyed the oxygen vacancies (VO) conductive filament model along the grain boundary (GB). Additionally, the GB resistive activation energy of the Y-doped device was inferior to that of the undoped device. It exhibited a shift of theVOtrap level towards the conduction band bottom after Y-doping in the HfOxfilm, which was the main reason for the improved RS performance.

Reliability and Stability Improvement of MOS Capacitors via Nitrogen-Hydrogen Mixed Plasma Pretreatment for SiC Surfaces.

We investigated the effect of nitrogen-hydrogen (NH) mixed plasma pretreatment of 4H-SiC surfaces on SiC surface properties, SiO2/SiC interface quality, and the reliability and voltage stability of metal-oxide-semiconductor (MOS) capacitors. The NH plasma pretreatment decreased the incomplete oxide and contaminants on the SiC surface and reduced the density of SiO2/SiC interface traps. Compared with the untreated sample, the dielectric insulating characteristics and reliability of samples pretreated by NH plasma were improved. We also demonstrated that the shift/hysteresis of the flat band voltage (Vfb) and the midgap voltage (Vmg) induced by bias temperature stress for SiC MOS capacitors after NH plasma pretreatment was significantly decreased. Furthermore, the mechanisms of NH plasma pretreatment to improve interface properties and device performances were determined by combining secondary ion mass spectrometry (SIMS) measurements, X-ray photoelectron spectroscopy (XPS), and first-principles calculations. The result indicates that the excessive oxidation at the SiO2/SiC interface was limited due to the reduction in the diffusion of oxygen atoms into SiC caused by the surface Si-H and Si-N; NH plasma pretreatment suppressed the generation of interfacial traps by reducing surface pollutants and passivating surface defects, and some N atoms introduced into the SiO2/SiC interface effectively passivated the interfacial electroactive traps.

Diagnostic value of corneal higher-order aberrations in keratoconic eyes.

PURPOSE: This study aimed to investigate the diagnostic value of corneal anterior, posterior, and total higher-order aberrations in keratoconic eyes. METHODS: We enrolled 94 patients (152 eyes) with mild keratoconus (Group 1), 64 patients (101 eyes) with moderate keratoconus (Group 2), and 32 patients (52 eyes) with advanced keratoconus (Group 3) according to the Amsler-Krumeich classification system; 99 healthy controls (197 normal eyes) were likewise enrolled. Anterior, posterior, and total corneal higher-order aberrations were assessed using a rotating Scheimpflug camera. The 3rd-order and 4th-order root-mean-square values were calculated for higher-order aberrations, including coma, spherical, and trefoil aberrations. Differences between keratoconic and normal eyes were analyzed using Kruskal-Wallis tests. Receiver operating characteristic curves were evaluated for the keratoconus and control groups. RESULTS: The differences in coma 90, coma, trefoil, and spherical aberrations, as well as 3rd-order and 4th-order root-mean-square values, were statistically significant between the keratoconus and control groups for all anterior, posterior, and corneal aberrations. The absolute values of these higher-order aberrations were higher in the keratoconus groups than in the control group and increased with keratoconus severity in Groups 1-3. Coma and 3rd-order RMS values showed excellent sensitivity and specificity for discriminating between normal and keratoconus eyes for all anterior, posterior, and corneal aberrations. CONCLUSION: Coma aberrations and 3rd-order root-mean-square values may be valuable for diagnosing keratoconus. Combining these data with topography information may enable the effective and efficient detection of keratoconus in the future.

Corneal densitometry in bilateral keratoconus patients with unilateral corneal Vogt's striae: a contralateral eye study.

PURPOSE: To investigate corneal densitometry and correlations with corneal morphological parameters in patients with bilateral keratoconus (KC) with unilateral Vogt's striae. METHODS: This prospective contralateral study enrolled 112 patients (224 eyes) with evident KC characteristics (corneal topography with asymmetric bow-tie pattern, inferior steepening), and at least one KC sign (conical protrusion of the cornea at the apex, corneal stromal thinning, Fleischer ring, Vogt's striae) on slit-lamp examination. Corneal densitometry and morphological parameters were measured using Pentacam HR. RESULTS: The mean age was 23.93 ± 6.81 years. Fifty-two (23.22%), 111 (49.55%), and 61 (27.23%) eyes were in mild, moderate, and severe groups, respectively. Corneal densitometry values of the anterior 0-2 mm and 2-6 mm, intermediate 0-2 mm and 2-6 mm, posterior 2-6 mm, and total cornea 2-6 mm were significantly higher in eyes with Vogt's striae (P < 0.05), whereas those of the anterior 6-10 mm, posterior 0-2 mm, and total cornea 6-10 mm were significantly lower in eyes with Vogt's striae (P < 0.05). Anterior 0-2 mm and total cornea 2-6 mm corneal densitometry values were positively correlated with anterior K1 (A-K1), K2 (A-K2), Km (A-Km), Kmax (A-Kmax), anterior corneal elevation, and posterior corneal elevation (P < 0.05), and negatively correlated with central corneal thickness and thinnest corneal thickness in eyes with Vogt's striae (P < 0.05). A-K2, A-Km, and A-Kmax were significantly correlated with the densitometry values of the anterior 0-2 mm and intermediate 0-2 mm in eyes without Vogt's striae (P < 0.05). CONCLUSION: Vogt's striae mainly occur on the anterior and intermediate layers during KC progression.

Improving the Sensing Properties of Graphene MEMS Pressure Sensor by Low-Temperature Annealing in Atmosphere.

The high demand for pressure devices with miniaturization and a wide bearing range has encouraged researchers to explore new high-performance sensors from different approaches. In this study, a sensitive element based on graphene in-plane compression properties for realizing pressure sensing is experimentally prepared using microelectromechanical systems (MEMS) fabrication technology; it consists of a 50 µm thick, 1400 µm wide square multilayer component membrane and a graphene monolayer with a meander pattern. The prepared sample is extensively characterized and analyzed by using various techniques, including atomic force microscopy, Raman spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, COMSOL finite element method, and density functional theory. The sensing performance of the new pressure sensor based on the sensitive element are obtained by theoretical analysis for electromechanical measurements of the sensitive element before and after low-temperature annealing in atmosphere. Results demonstrate that atmospheric annealing at 300 °C enhances the pressure sensing sensitivity by 4 times compared to pristine graphene without annealing, which benefits from the desorption of hydroxyl groups on the graphene surface during annealing. The sensitivity is comparable and even better than that of previous sensors based on graphene in-plane properties. Our results provide new insights into realizing high-performance MEMS devices based on 2D sensitive materials.

Posterior corneal elevation changes and characteristic analysis 1 year after corneal collagen cross-linking for keratoconus.

PURPOSE: To investigate the changes in posterior corneal elevations (PCEs) in the circular areas and local points after corneal collagen cross-linking (CXL) for the treatment of keratoconus. METHODS: Method 1 divided the cornea into 0-2, 2-4, 4-6, and 6-8 mm regions centering on the apex. Method 2 obtained other 34 PCE values of local point that were identified on the nasal, supra-nasal, sub-nasal, superior, inferior, temporal, supra-temporal, and sub-temporal sides of the circle with diameters of 2, 4, 6, and 8 mm, and the apex and thinnest point. RESULTS: Method 1 showed a forward displacement of PCE at 1 month after CXL and then a backward displacement at 3 months. In Method 2, the points on the temporal side of 2 mm and 4 mm showed the same trend. The backward displacements of PCE on the temporal side of 2 mm at 6 months and on the temporal side of 4 mm at 12 months after CXL were both statistically different than those at 1 month after CXL (P < 0.05). No significant forward displacement of PCE was found in all local points in different quadrants at 1 year after CXL. CONCLUSION: The PCEs in circular areas and characteristic points of different diameters in keratoconic eyes after CXL change with time. Local point assessment of the PCE is more clinically significant. In points selected in different quadrants of the cornea, the change in temporal points was more significant after CXL.

Intraocular pressure changes and corneal biomechanics after hyperopic small-incision lenticule extraction.

BACKGROUND: We aimed to compare the intraocular pressure (IOP) measurements by a dynamic Scheimpflug analyzer (Corvis ST), a non-contact tonometer, and an ocular response analyzer after hyperopic small-incision lenticule extraction (SMILE). METHODS: Thirteen patients who underwent hyperopic SMILE in one eye were enrolled prospectively. IOP and corneal biomechanical parameters were measured preoperatively and at 1 week, 1 month, and 3 months postoperatively with a non-contact tonometer (IOPNCT), Corvis ST (biomechanical corrected IOP [bIOP]), and ocular response analyzer (Goldmann-correlated intraocular pressure [IOPg] and cornea compensated IOP [IOPcc]). A linear mixed model was used to compare the IOPs and biomechanical values among methods at each time point. RESULTS: IOPNCT, IOPg, and IOPcc dropped significantly after surgery, with the amplitude being 3.15 ± 0.48 mmHg, 5.49 ± 0.94 mmHg, and 4.34 ± 0.97 mmHg, respectively, at the last follow-up visit. IOPNCT decreased by 0.11 ± 0.06 mmHg per µm of excised central corneal thickness. bIOP did not change significantly after surgery. Preoperatively, no difference was found among the four measurements (P > 0.05). Postoperatively, IOPNCT and bIOP were higher than IOPg and IOPcc. bIOP was independent of cornea thickness at last follow-up visit, whereas it correlated significantly with corneal biomechanics similar to the other three IOP values. CONCLUSION: bIOP is a relative accurate measure of IOP after hyperopic SMILE.

Ultrastructural Changes and Corneal Wound Healing After SMILE and PRK Procedures.

PURPOSE: To compare keratocyte activation, cellular morphologic changes and wound healing after SMILE and PRK procedures using transmission electron microscope (TEM). METHODS: In this study, 22 New Zealand white rabbits (10- to 15-week old) were used. The right eyes of all animals underwent SMILE procedure and the left eyes underwent PRK procedure. Cornea samples taken 1 day and 1 week postoperatively were examined using TEM. RESULTS: Using TEM 1 day after SMILE procedure, the organization of collagen fibers seemed to have been preserved without thermal alterations. Keratocyte activation was observed in the anterior stroma. Disrupted collagen arrangement and debris of cells are visible in the area of damage, and some phagocytic cells and a large number of secondary lysosomes are visible in those cells. At the perimeter zone of the interface, many coenocytes and collagen fragments could be found within the phagocytic cell. One week after SMILE procedure, potential lacuna could be discerned. A large part of the interface of the lenticule extracted had an appearance of clearly being adhered to some mucus secretions. One day after PRK procedure, an irregular epithelial surface was visible using TEM. Keratocytes had been activated and the rough endoplasmic reticulum in those cells had expanded. One week after PRK procedure, the epithelial surface still was irregular and keratinization of the epithelium was still visible in some areas. Corneal endothelium cells were mildly damaged and some vacuoles within the cytoplasm could be discerned. In the anterior stroma, some unhealthy activated keratocytes could still be observed. New collagen fibrils were found present near the activated keratocytes. CONCLUSION: Using TEM, keratocyte activation could still be observed after SMILE compared to after PRK procedure. Fewer cellular ultrastructural changes were seen after SMILE procedure. Unlike in PRK procedure, no damaged epithelium and endothelium were found after SMILE.

[The study of the changes of ultra- microstructure after a momentary action of femtosecond laser with human corneal tissue in vivo].

OBJECTIVE: To observe the changes of pathology and ultra- microstructure of corneal lenticules extracted by femtosecond laser small incision lenticule extraction surgery and to investigate instantaneous damage of photodisruption of femtosecond laser to human corneal tissue in vivo. METHODS: The small incision lenticule extraction surgeries in 25 myopic eyes were performed with Carl Zeiss VisuMax femtosecond laser, and the lenticules were observed by light microscopy, scanning electron microscopy and transmission electron microscopy. RESULTS: Light microscopy showed slight edema in part of the collagen fibers in the cornea lenticule tissue. A thin layer of deep tissue dyeing at the edge of the lenticule was observed on a linear array. In the center of superficial lenticule tissue existed a few bubbles. Under the scanning electron microscope, the anterior surface of the lenticule was found to be relatively smooth, with no obvious tissue bridge. The posterior surface of the lenticule was slightly irregular compared with the anterior surface. Scattered tissue bridges and residual traces of the effect of femtosecond laser photodisruption could be observed. Under the transmission electron microscope, adjacent collagen fiber layers in the corneal lenticule matrix were detected to cross each other regularly, with no breakage of the collagen fibers or separation of the layers. The incision of the collagen fibers on one side of the lenticule was on a linear alinement. It can also be observed that the central part of the lenticule was mildly damaged. However, the stroma cells near the lenticule limbus were severely damaged. Part of the corneal stroma cells were solidified with several shivers, which might be due to the photodisruption. Some of the damaged corneal stroma cells were observed with remnants, while the spaces occupied by part of the corneal cells became fractured. CONCLUSIONS: Obvious damage of the femtosecond laser to the corneal tissue at early stage was not observed. At the edge of the area where femtosecond laser focused, there were mild thermal injury and slight structure change. There were not abnormal appearances of the tissue structure at the non-focus area.

Corneal biomechanical effects: small-incision lenticule extraction versus femtosecond laser-assisted laser in situ keratomileusis.

PURPOSE: To compare the biomechanical properties of the cornea after small-incision lenticule extraction (lenticule extraction group) with those after femtosecond laser-assisted laser in situ keratomileusis (femtosecond LASIK group). SETTING: Tianjin Eye Hospital & Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Tianjin Medical University, Tianjin, China. DESIGN: Prospective comparative case series. METHODS: Corneal hysteresis (CH), the corneal resistance factor (CRF), and 37 other biomechanical waveform parameters were quantitatively assessed with the Ocular Response Analyzer preoperatively and 1 week and 1, 3, and 6 months postoperatively. RESULTS: Each group comprised 40 eyes. The decrease in CH and the CRF was statistically significant 1 week postoperatively compared with preoperatively in both groups (P<.0001). However, the CH and CRF values in the lenticule extraction group were significantly higher than those in the femtosecond LASIK group 3 months and 6 months postoperatively (P<.032). The residual stromal thickness index versus the CRF and CH and the planned lenticule thickness versus the change in central corneal thickness were statistically significant in the lenticule extraction group (r = 0.388 to 0.950, P<.018); no significant correlation was found in the femtosecond LASIK group. In the waveform analysis of the lenticule extraction group, 28 of the 37 biomechanical waveform parameters differed significantly between preoperative values and postoperative values (P<.035). CONCLUSIONS: Both small-incision lenticule extraction and femtosecond laser-assisted LASIK can cause biomechanical changes in the cornea. However, changes in the cornea's viscoelastic properties were less after lenticule extraction than after LASIK. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

[Distribution of corneal densitometry and its correlation with ocular stray light in healthy eyes].

OBJECTIVE: To evaluate and investigate the distribution of corneal density and its Correlation with stray-light value in adult and healthy eyes. METHODS: A prospective study. Human corneal specimens ranging in age between 20 and 49 years, 116 patients (232 eyes) in total, divided into three groups: 20-29, 30-39, 40-49. Pentacam was used to evaluate total corneal average density and corneal thickness at different diameter around the corneal apex, for corneal density were ≤ 2 mm, >2 mm and ≤ 6 mm, >6 mm and ≤ 10 mm, for corneal thickness were 2 mm, 6 mm and 10 mm, C-quant was used for the stray-light value. Software SPSS 17.0 was used for statistical analysis. Independent samples t testing method was applied to compare the corneal densitometry in different gender and between left eyes and right ones, One-way ANOVA was applied to analyze the differences of corneal density in different age groups and diameters. Pearson correlation analysis was applied to assess the correlation in corneal densitometry values of different diameters, between corneal density of different diameters and age, corneal density of different diameters and corneal thickness of different diameters, corneal density of different diameters and stray-light values. RESULTS: Corneal density for ≤ 2 mm, >2 mm and ≤ 6 mm, >6 mm and ≤ 10 mm diameter are 10.1 ± 1.5(8.2-16.7), 9.3 ± 1.3(7.9-14.2), 9.6 ± 1.7(7.3-16.2). Corneal density of >6 mm and ≤ 10 mm diameter in different age groups were 8.9 ± 1.1, 9.3 ± 1.2, 10.7 ± 2.1, there was a statistical difference in these values (F = 28.939, P = 0.000), and there was a positive correlation between corneal density of >6 mm and ≤ 10 mm diameter and age (r = 0.417, P = 0.000), There were no statistical differences in corneal density values of ≤ 2 mm and >2 mm and ≤ 6 mm in different age groups (F = 1.575, 1.436; P > 0.05), and they had no correlation with age (r = 0.002, 0.048; P > 0.05). There was no statistical difference in corneal density in different gender (t = 1.744, 1.647, -1.181; P > 0.05). Corneal density values of left eyes and right ones had positive relationships at the same diameter (r = 0.977, P = 0.000; r = 0.992, P = 0.000; r = 0.933, P = 0.000), and there were no statistical differences (t = 0.124, 0.199, -0.020;P > 0.05). Between corneal density values of different diameter, there are also some positive relationships, >6 mm and ≤ 10 mm and ≤ 2 mm (r = 0.710, P = 0.000), >6 mm and ≤ 10 mm and >2 mm and ≤ 6 mm (r = 0.748, P = 0.000), ≤ 2 mm and >2 mm and ≤ 6 mm (r = 0.973, P = 0.000), relationship between ≤ 2 mm and >2 mm and ≤ 6 mm, >2 mm and ≤ 6 mm and >6 mm and ≤ 10 mm was obvious, and there was statistical difference in them (F = 17.057, P = 0.000) . The ocular stray light value was 0.95 ± 0.19(0.48-1.38), Corneal density values of ≤ 2 mm, >2 mm and ≤ 6 mm and >6 mm and ≤ 10 mm diameter had positive relationships with the stray light value (r = 0.134,0.146,0.159, P = 0.042,0.026,0.016). CONCLUSIONS: Corneal density can be influenced by age, the influence from age infected the corneal density of peripheral more. There was no correlation between corneal density and corneal thickness. There were some influences of corneal density of healthy eyes to the ocular stray light.

[Early outcomes of corneal sensitivity changes after small incision lenticule extraction and femtosecond lenticule extraction].

OBJECTIVE: To evaluate and compare the recovery of central and peripheral corneal sensitivity in the early period after small incision lenticule extraction (SMILE) and femtosecond lenticule extraction (FLEx). METHODS: In this study, 47 cases (87 eyes) which underwent SMILE and FLEx were included. Central, superior, inferior, nasal and temporal corneal sensitivity was measured using a Cochet-Bonnet esthesiometer (Luneau Ophthalmologic) before and 1 week, 1 month, and 3 months after SMILE and FLEx. The results were analyzed with Mann-Whitney test by SPSS13.0 software. RESULTS: There were statistical differences between SMILE and FLEx group in the central, inferior, nasal and temporal corneal sensitivity at 1 week, 1 month and 3 months postoperatively (Z = -5.219, -7.120, -6.735, -7.139, -5.945, -6.644, -7.006, -7.121, -5.262, -3.086, -4.140, -3.523. P < 0.01). However, the superior corneal sensitivity in the SMILE group did not show significant difference (Z = -1.807, P = 0.071) as compared to FLEx group (with exception of 1 week postoperatively). At 1 month and 3 months postoperatively, corneal sensitivity in the superior quadrant were (5.23 ± 0.62) and (5.57 ± 0.57) cm in the SMILE group, and were (4.43 ± 1.20) and (4.85 ± 1.11) cm in the FLEx group. There were statistical differences between these two groups (Z = -2.935, -2.678. P = 0.003, 0.007). In the SMILE group, corneal sensitivity in the central, superior, inferior, nasal and temporal quadrants at 3 months postoperatively was (5.74 ± 0.51), (5.57 ± 0.57), (5.70 ± 0.55), (5.83 ± 0.37), (5.84 ± 0.30) cm respectively, there were no significant differences as compared with preoperative data (Z = -1.255, -0.893, -0.570, -0.630, -0.935. P = 0.209, 0.440, 0.569, 0.529, 0.350). In the FLEx group, corneal sensitivity in the superior at 3 months postoperatively was 4.85 ± 1.11, there was not significant difference compared with preoperative data (Z = -1.095, P = 0.272). There were no correlations between the changes of central corneal sensitivity and central corneal ablation depth, central corneal thickness and preoperative spherical equivalent (SMILE group: r = 0.159, -0.202, 0.106, 0.060. P > 0.05. FLEx group: r = -0.156, -0.059, 0.058, -0.005. P > 0.05) after SMILE and FLEx surgery. CONCLUSIONS: Corneal sensitivity decreases after SMILE and FLEx, and then returns to its original state over time. The decrease of corneal sensitivity after the SMILE was fewer and the recovery was faster as compared with FLEx.

Comparison of corneal sensitivity between FS-LASIK and femtosecond lenticule extraction (ReLEx flex) or small-incision lenticule extraction (ReLEx smile) for myopic eyes.

BACKGROUND: To compare the effect on corneal sensitivity between femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and femtosecond lenticule extraction (ReLEx flex) or FS-LASIK and small-incision lenticule extraction (ReLEx smile) surgery. METHODS: Twenty-seven subjects (54 eyes) underwent FS-LASIK, 22 subjects (40 eyes) underwent ReLEx flex, and 32 subjects (61 eyes) underwent ReLEx smile surgery. Cochet-Bonnet esthesiometry (Luneau Ophthalmologie Chartres, Cedex, France) was used to evaluate corneal sensitivity preoperatively as well as at 1 week and 1 and 3 months after surgery. RESULTS: At 1 week, central, superior, nasal, and temporal corneal sensitivity in the ReLEx flex group was significantly higher than in the FS-LASIK group (P=0.007, 0.004, 0.020, 0.004 respectively) and in the central and inferior areas at 3 months (P=0.002, 0.009 respectively). A higher corneal sensitivity after ReLEx smile surgery was observed in every quadrant at 1 week and 1 and 3 months compared with FS-LASIK surgery (P<0.01). Furthermore, in the ReLEx smile group, there were no statistical differences in the superior and temporal quadrants at 1 month postoperatively compared with preoperatively (5.19 ± 0.61 cm, P=0.198 and 5.64 ± 0.48 cm, P=0.330 respectively) and no significant differences in any quadrant at 3 months. CONCLUSIONS: Postoperative corneal sensitivity was not remarkably changed after ReLEx smile surgery compared with FS-LASIK. This might be because ReLEx is a flapless procedure.