Evaluation of corneal endothelium after UVA/riboflavin cross-linking in thin keratoconic corneas

Dear Sir,UVA/riboflavin cross-linking （CXL） has been used clinically applied for the treatment of keratoconus and corneal edema via enhancement of corneal stiffness The safety of the corneal endothelium is of prime importance during CXL treatment. In clinical practice, a corneal thickness （CT） of 400um has traditionally been regarded as the minimum treatable thickness, thereby avoiding damage to the corneal endothelium Although CXL has been applied to thinner corneas, using a hypoosmotic solution onto cornea and inducing edema . CXL safety still needs further evaluation because of lower relative concentration of collagen in the hydrated stroma . This study aims to evaluate the changes of corneal endothelial density （ECD） in cases where the CT is 〈400 um before iatrogenic corneal swelling and CXL treatment.

EXPERIMENTAL STUDY ON THE CORNEAL ENDOTHELIUM OF TRAUMATIC CATARACT

The cell morphology of corneal endothelium in 84 mice with experimental traumatic cataract was investigated with stained corneal buttons. In the experimental group, the boundaries between adjacent corneal endothelial cells were significantly distorted, some cell boundaries manifested degenerative changes that led to coalescence of the cells. The mean density and mean area of endothelial cells of the controls showed significant difference from those of the experimental group during the 12 weeks of observ...

Short term effects of small incision lenticule extraction surgery on corneal endothelium

AIM： To assess the effects of small incision lenticule extraction（SMILE） surgery on the corneal endothelium at1 d to 1mo postoperatively.·METHODS： A retrospective, observational study was conducted on 47 patients（47 eyes） who received SMILE surgery. Patients were grouped according to contact lens wear condition. The corneal endothelium was examined preoperatively and at 1d, 1wk and 1mo postoperatively.The corneal endothelium was analyzed for endothelial cell density（ECD）, percentage of hexagonal cells, and coefficient of variation（CV） of cell size.·RESULTS： There were no significant decrease in the ECD, percentage of hexagonal cells or increase in CV at1 d, 1wk and 1mo postoperatively（P 〉0.05）. However,there was a small increase of ECD by 2.88% in contact lens wearers（78.26±113.62 cell/mm2, P 〈0.05）.· CONCLUSION： SMILE has no significant adverse effects on the corneal ECD and morphology during 1mo follow-up time.

Effect of topical 0.05% cyclosporine A on corneal endothelium in patients with dry eye disease

· AIM: To determine the effect of topical 0.05% cyclosporine A (CsA) on corneal endothelium in patients with dry eye disease. · METHODS: Observational, prospective, case series study. Fifty-five eyes of 29 consecutive patients (9 males and 20 females; median age: 66.8 years, interquartile range: 61 -73.2 years) with moderate -severe dry eye disease were evaluated. All patients were treated with topical 0.05% CsA ophthalmic emulsion twice a day in addition to lubricant eyedrops 5 times a day. The follow- up period was 12 months. Before treatment and at 3 and 12 months post -treatment central corneal specular microscopy was performed. The endothelial cell density (ECD), coefficient of variation of cell size (CoV), and percentage of hexagonal cells (Hex %) were analyzed. ·RESULTS: The median ECDs pre-treatment and at 3 and 12 months post-treatment were 2 352.5/mm 2 (inter- quartile range, 2 178 -2548.5), 2 364/mm 2 (interquartile range, 2 174.25 -2 657.5), and 2 366 cells/mm 2 (inter - quartile range, 2 174.75-2 539.75), respectively (P=0.927, one way ANOVA). The median CoVs pre-treatment and at 3 and 12 months post -treatment were 34.5 (interquartile range, 30 -37), 35 (interquartile range, 30 -38), and 34 (interquartile range, 30.75-38.25), respectively (P=0.7193, one way ANOVA). The median Hex % values pre - treatment and at 3 and 12 months post -treatment were 53 (interquartile range, 47 -58), 54 (interquartile range, 45.75 -59), and 50.5 (interquartile range, 45.75 -58), respectively (P=0.824, one way ANOVA). · CONCLUSION: Treatment of patients with dry eye disease for 12 months with topical 0.05% CsA does not seem to cause substantial changes on corneal endothelium.

Differences in energy and corneal endothelium between femtosecond laser-assisted and conventional cataract surgeries：prospective,intraindividual,randomized controlled trial

AIM： To compare intraoperative phacoemulsification parameters and its effect on the corneal endothelium of eyes undergoing femtosecond laser-assisted cataract surgery（FLACS） versus conventional phacoemulsification（CP） cataract surgery.METHODS： Two hundred eyes from one hundred patients were included in a prospective, non-blinded, randomized, controlled, intraindividual clinical study. One hundred eyes underwent FLACS while their one hundred fellow eyes underwent CP. All surgeries were performed using the Victus？ femtosecond laser platform and Infinity？ Vision System phacoemulsification machine. Primary outcome measure was endothelial cell density 6 mo after surgery. Secondary outcome measures included central corneal thickness（CCT）, average cell area, standard deviation, coefficient of variation and hexagonality before surgery and 6 mo after surgery and endothelial cell density loss during this period were also evaluated. Intraoperative efficiency parameters [cumulative dissipated energy（CDE）, total intraocular surgery time, total ultrasound time, total phacoemulsification time, total torsional energy time, total aspiration time, ultrasound energy, torsional amplitude and fluid required during surgery] were also collated. RESULTS： Data from these patients was not considered for analysis. Data from 92 patients were analysed. Postoperative endothelial cell density（cells/mm2） between groups（2211.88±392.49 CP; 2246.31±403.48 FLACS） was not statistically significant（P=0.869）. Total ultrasound time, torsional energy time, CDE and fluid requirements were significantly lower the FLACS group（P〈0.05）. Other parameters did not show statistically significant difference between FLACS and CP.CONCLUSION： FLACS displays significant improvements in phacoemulsification parameters in comparison to CP. There are no significant differences in corneal endothelium measures between FLACS and CP.

STUDY IN CYTOTOXICITY OF GENTAMYCIN TO CORNEAL EPITHELIUM AND ENDOTHELIUM IN TISSUE CULTURE

A study in cytotoxicity of gentamyein to tissue-cultured bovine corneal endothelial cells and rabbit corneal epithelial cells is reported. When the cultured cells reached confluence, they were exposed to tissue culture media containing gentamycin for 6 hours. We founl that 0.5% gentamycin caused significant damage to corneal epithelial cells---diffuse plasmolysis, with scattered cell necrosis and 5% loss.While corneal endothelial cells were exposed to 1.6 mg/ml gentamycin, extensive cell loss (approximate- ly 15%) was observed. The damaged cells recovered their normal morphology after 24 hours. When the concentration of gentamycin increased twice, serious damage to cells occured. The area of cell loss reached 40%, and the recovery of cellular morphology Was much slower. This study demonstrates that gentamycin potential cytotoxicity to corneal epithelium and endothelium, suggesting that gentamycin should be rationally used in the treatment of ocular diseases.

Transplanting embryonic stem cells onto damaged human corneal endothelium

AIM To investigate whether human embryonic stem cells(hESCs) could be made to attach, grow and differentiate on a human Descemet's membrane(DM).METHODS Spontaneously differentiated hESCs were transferred onto a human corneal button with the endothelial layer removed using ocular sticks. The cells were cultured on a DM for up to 15 d. The genetically engineered hESC line expressed green fluorescent protein, which facilitated identification during the culture experiments, tissue preparation, and analysis. To detect any differentiation into human corneal endothelial-like cells, we analysed the transplanted cells by immunohistochemistry using specific antibodies.RESULTS We found transplanted cells form a single layer of cells with a hexagonal shape in the periphery of the DM. The majority of the cells were negative for octamer-binding transcription factor 4 but positive for paired box 6 protein, sodium potassium adenosine triphosphatase(NaKATPase), and Zona Occludens protein 1. In four of the 18 trials, the transplanted cells were found to express CK3, which indicates that the stem cells differentiated into corneal epithelial cells in these cases. CONCLUSION It is possible to get cells originating from hESCs to become established on a human DM, where they grow and differentiate into corneal endothelial-like cells in vitro.

Hammered silver appearance of the corneal endothelium in Fuchs uveitis syndrome:A case report

BACKGROUND Hammered silver appearance of the corneal endothelium is considered a characteristic change in iridocorneal-endothelial syndrome.Herein we report an interesting case of hammered silver appearance of the corneal endothelium in Fuchs uveitis syndrome(FUS).CASE SUMMARY A 49-year-old man with progressive vision loss in the right eye for one year was admitted to our hospital.The clinical manifestations of the patient’s right eye were mild conjunctival hyperemia,scattered stellate keratic precipitates on the corneal endothelium,normal depth anterior chamber,2+cellular reaction in the aqueous humor,diffuse iris depigmentation,absence of synechia,Koeppe nodules,opalescent lens,and vitreous opacity.FUS and a complicated cataract were diagnosed based on the typical clinical manifestations.The corneal endothelial changes were recorded in detail by slit-lamp examination,specular microscopy,and in vivo confocal microscopy before cataract extraction,revealing a hammered silver appearance of the corneal endothelium in the affected eye,a wide-band dark area,as well as irregular corneal endothelial protuberances and dark bodies of various sizes.Subsequently,the patient underwent phacoemulsification combined with intraocular lens implantation,and his postoperative visual acuity recovered to 1.0.CONCLUSION Hammered silver appearance of the corneal endothelium in FUS,which is considered a more serious manifestation of endothelial damage,is rare and may be caused by many irregular protrusions in the corneal endothelium.

AB086.Influence of the intraocular pressure on the expression of tight junctions in the corneal endothelium

Background:Cells are influenced by their environment.In vivo,the corneal endothelium is subjected to intraocular pressure(IOP).The purpose of this project was to evaluate in vitro,the effect of the IOP on the formation of tight junctions in the corneal endothelium.Methods:Cultivated corneal endothelial cells(P2-P3;n=6 populations)were seeded on devitalized on corneas(n=10 pairs).Native corneas and devitalized corneas were respectively used as positive(n=2 pairs)and negative controls(n=3 pairs).Corneas were placed in artificial anterior chambers and subjected to a hydrostatic pressure between 0.3 and 0.4 psi during 4-5 days.Unpressured control corneas were maintained in cell culture dishes.Pictures of the corneas were taken following the experiment to assess stromal transparency.Morphology,corneal thickness and distribution of ZO-1,n-cadherin,b-catenin,NaK ATPase pump and HCO3-cotransporter were evaluated by electron microscopy,histological staining and immunofluorescences.Results:Pressure treated corneas were more transparent than the controls.Thickness was accordingly reduced by 38.4%±4.9%for cultivated endothelium and 32.2%±2.7%for native endothelium.Negative controls change in transparency and thickness were marginal.Pressure treated cells showed none or at most marginal difference in morphology and expression of ZO-1,n-cadherin,b-catenin,NaK ATPase pump and HCO3-cotransporters and failed to recreate a phenotype similar to native corneas.Pressure however increased cortical localisation of the protein ZO-1 in both cultivated and native endothelium.Conclusions:These results suggest that anterior chamber hydrostatic pressure may enhance endothelial functionality by modulating the distribution of tight junction’s proteins.

The role of corneal endothelium in macular corneal dystrophy development and recurrence

Macular corneal dystrophy(MCD)is a progressive,bilateral stromal dystrophic disease that arises from mutations in carbohydrate sulfotransferase 6(CHST6).Corneal transplantation is the ultimate therapeutic solution for MCD patients.Unfortunately,postoperative recurrence remains a significant challenge.We conducted a retrospective review of a clinical cohort comprising 102 MCD patients with 124 eyes that underwent either penetrating keratoplasty(PKP)or deep anterior lamellar keratoplasty(DALK).Our results revealed that the recurrence rate was nearly three times higher in the DALK group(39.13%,9/23 eyes)compared with the PKP group(10.89%,11/101 eyes),suggesting that surgical replacement of the corneal endothelium for treating MCD is advisable to prevent postoperative recurrence.Our experimental data confirmed the robust m RNA and protein expression of CHST6 in human corneal endothelium and the rodent homolog CHST5 in mouse endothelium.Selective knockdown of wild-type Chst5 in mouse corneal endothelium(AC^(siChst5)),but not in the corneal stroma,induced experimental MCD with similar extracellular matrix synthesis impairments and corneal thinning as observed in MCD patients.Mice carrying Chst5 point mutation also recapitulated clinical phenotypes of MCD,along with corneal endothelial abnormalities.Intracameral injection of wild-type Chst5 rescued the corneal impairments in AC^(siChst5)mice and retarded the disease progression in Chst5 mutant mice.Overall,our study provides new mechanistic insights and therapeutic approaches for MCD treatment by highlighting the role of corneal endothelium in MCD development.

Small-diameter acellular porcine corneal stroma for peripheral corneal ulceration treatment

AIM:To evaluate the clinical efficacy of small-diameter acellular porcine corneal stroma(SAPS)for the treatment of peripheral corneal ulceration(PCU).METHODS:This retrospective clinical study included 18 patients(18 eyes)with PCU between April 2018 and December 2020.All patients had PCU and underwent lamellar keratoplasty with SAPS.Observation indicators included preoperative and postoperative best-corrected visual acuity(BCVA)and transparency of SAPS.The infection control rate in the surgical eye-lesion area was also calculated.RESULTS:Eighteen patients underwent lamellar keratoplasty with SAPS to treat PCU.None of the patients experienced rejection after 6mo(18/18)and 12mo(16/16)of follow-up.The BCVA(0.47±0.30)at the 6mo followup after operation was significantly improved compared with the baseline(0.99±0.80),and the difference was statistically significant(Z=-3.415,P<0.05).The BCVA at the 12mo follow-up after operation was not statistically significant compared to the 6mo(Z=0,P=1).With time,the SAPS graft gradually became transparent.At the 6mo(18/18)and 12mo(16/16)follow-up,none of the patients had recurrent corneal infection.CONCLUSION:SAPS is clinically effective in the treatment of PCU,improving the patient’s BCVA and reducing the incidence of rejection after keratoplasty.

The Corneal Endothelium in Children after Congenital Cataract Surgery--A Comparison of Pre- and Post-Operative Results

Three months after surgery, the research group showed significantly statistical improvement in visual acuity, a statistically significant decrease in corneal endothelial cell density, a statistically significant increase in the percentage of 5 and 8 sided cells and a statistically significant decrease in the percentage of six sided cells. Central corneal thickness and the percentage of 4 and 7 and more than 8 sided did not change in a statistically significant way. Comparing the test group and control group, no statistically significant differences were detected in the examined parameters. The present study also shows that the cornea in the eyes with congenital cataract does not show statistically significant changes in the density and the morphology of the corneal endothelial cells and the thickness of the cornea and in terms of corneal thickness in comparison to the corneas of healthy eyes. Although in corneas undergoing cataract occurs statistically significant changes, the influence of the cornea does not affect the improvement in visual acuity which was also demonstrated in this study.

Effect of mitomycin C on the corneal endothelial cells of Saudi patients with myopia after transepithelial photorefractive keratectomy:a two-armed cohort study

AIM:To study the effect of mitomycin C(MMC)applied during transepithelial photorefractive keratectomy(TPRK)on the corneal endothelium one week(W1)and three months(M3)after surgery and its determinants.METHODS:In this two-armed cohort study conducted in 2022,eyes treated with MMC during TPRK(group 1)were compared with eyes not treated with MMC(group 2).The corneal endothelial cell(EC)count,EC density(ECD;cells/mm2),average(μm2),standard deviation(μm2),coefficient of variation(CV%),ECmax,ECmin,and EC percentage of hexagonality were estimated at W1 and M3.The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables.RESULTS:Group 1 had 26 eyes,and group 2 had 78 eyes.All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2.The MMC usage was not a significant predictor of the change in ECD(P=0.644),change in CV(P=0.374),and change in the percentage of hexagonality of EC(P=0.164)at W1.However,the use of MMC was a significant predictor of changes in CV(P=0.014)and the change in the percentage of hexagonality of EC(P=0.039)at M3.The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices,postoperatively.CONCLUSION:The use of MMC doesn’t affect ECD,CV,and percentage of hexagonality at W1 if other surgical indices are considered.At M3 after operating myopic eyes by TPRK,MMC significantly influence the CV and percentage of hexagonality.The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.

Changes in posterior corneal elevation after small incision lenticule extraction for different myopic diopters

●AIM:To study the changes and effect factors of posterior corneal surface after small incision lenticule extraction(SMILE)with different myopic diopters.●METHODS:Ninety eyes of 90 patients who underwent SMILE were included in this retrospective study.Patients were allocated into three groups based on the preoperative spherical equivalent(SE):low myopia(SE≥-3.00 D),moderate myopia(-3.00 D>SE>-6.00 D)and high myopia(SE≤-6.00 D).Posterior corneal surfaces were measured by a Scheimpflug camera preoperatively and different postoperative times(1wk,1,3,6mo,and 1y).Posterior mean elevation(PME)at 25 predetermined points of 3 concentric circles(2-,4-,and 6-mm diameter)above the best fit sphere was analyzed.●RESULTS:All surgeries were completed uneventfully and no ectasia was found through the observation.The difference of myopia group was significant at the 2-mm ring at 1 and 3mo postoperatively(1mo:P=0.017;3mo:P=0.018).The effect of time onΔPME was statistically significant(2-mm ring:P=0.001;4-mm ring:P<0.001;6-mm ring:P<0.001).The effect of different corneal locations onΔPME was significant except 1wk postoperatively(1mo:P=0.000;3mo:P=0.000;6mo:P=0.001;1y:P=0.001).Posterior corneal stability was linearly correlated with SE,central corneal thickness,ablation depth,residual bed thickness,percent ablation depth and percent stromal bed thickness.●CONCLUSION:The posterior corneal surface changes dynamically after SMILE.No protrusion is observed on the posterior corneal surface in patients with different degrees of myopia within one year after surgery.SMILE has good stability,accuracy,safety and predictability.

Semaphorin 7A impairs barrier function in cultured human corneal epithelial cells in a manner dependent on nuclear factor-kappa B

●AIM:To evaluate the role of semaphorin 7A(Sema7A)and its associated regulatory mechanisms in modulating the barrier function of cultured human corneal epithelial cells(HCEs).●METHODS:Barrier models of HCEs were treated with recombinant human Sema7A at concentrations of 0,125,250,or 500 ng/mL for 24,48,or 72h in vitro.Transepithelial electrical resistance(TEER)as well as Dextran-fluorescein isothiocyanate(FITC)permeability assays were conducted to assess barrier function.To quantify tight junctions(TJs)such as occludin and zonula occludens-1(ZO-1)at the mRNA level,reverse transcriptionpolymerase chain reaction(RT-PCR)analysis was performed.Immunoblotting was used to examine the activity of the nuclear factor-kappa B(NF-κB)signaling pathway and the production of TJs proteins.Immunofluorescence analyses were employed to localize the TJs.Enzyme-linked immunosorbent assay(ELISA)and RT-PCR were utilized to observe changes in interleukin(IL)-1βlevels.To investigate the role of NF-κB signaling activation and IL^(-1)βin Sema7A’s anti-barrier mechanism,we employed 0.1μmol/L IκB kinase 2(IKK2)inhibitor IV or 500 ng/mL IL^(-1)receptor(IL-1R)antagonist.●RESULTS:Treatment with Sema7A resulted in decreased TEER and increased permeability of Dextran-FITC in HCEs through down-regulating mRNA and protein levels of TJs in a time-and dose-dependent manner,as well as altering the localization of TJs.Furthermore,Sema7A stimulated the activation of inhibitor of kappa B alpha(IκBα)and expression of IL-1β.The anti-barrier function of Sema7A was significantly suppressed by treatment with IKK2 inhibitor IV or IL-1R antagonists.●CONCLUSION:Sema7A disrupts barrier function through its influence on NF-κB-mediated expression of TJ proteins,as well as the expression of IL-1β.These findings suggest that Sema7A could be a potential therapeutic target for the diseases in corneal epithelium.

Stromal lenticule addition keratoplasty with corneal crosslinking for corneal ectasia secondary to FS-LASIK:a case series

●AIM:To explore the clinical efficacy and safety of stromal lenticule addition keratoplasty(SLAK)with corneal crosslinking(CXL)on patients with corneal ectasia secondary to femtosecond laser-assisted in situ keratomileusis(FS-LASIK).●METHODS:A series of 5 patients undertaking SLAK with CXL for the treatment of corneal ectasia secondary to FS-LASIK were followed for 4-9mo.The lenticules were collected from patients undertaking small incision lenticule extraction(SMILE)for the correction of myopia.Adding a stromal lenticule was aimed at improving the corneal thickness for the safe application of crosslinking and compensating for the thin cornea to improve its mechanical strength.●RESULTS:All surgeries were conducted successfully with no significant complications.Their best corrected visual acuity(BCVA)ranged from 0.05 to 0.8-2 before surgery.The pre-operational total corneal thickness ranged from 345-404μm and maximum keratometry(Kmax)ranged from 50.8 to 86.3.After the combination surgery,both the corneal keratometry(range 55.9 to 92.8)and total corneal thickness(range 413-482μm)significantly increased.Four out of 5 patients had improvement of corneal biomechanical parameters(reflected by stiffness parameter A1 in Corvis ST).However,3 patients showed decreased BCVA after surgery due to the development of irregular astigmatism and transient haze.Despite the onset of corneal edema right after SLAK,the corneal topography and thickness generally stabilized after 3mo.●CONCLUSION:SLAK with CXL is a potentially beneficial and safe therapy for advanced corneal ectasia.Future work needs to address the poor predictability of corneal refractometry and compare the outcomes of different surgical modes.

Clinical associations of corneal neuromas with ocular surface diseases

Corneal neuromas,also termed microneuromas,refer to microscopic,irregula rly-shaped enlargements of terminal subbasal nerve endings at sites of nerve damage or injury.The formation of corneal neuromas results from damage to corneal nerves,such as following corneal pathology or corneal or intraocular surge ries.Initially,denervated areas of sensory nerve fibers become invaded by sprouts of intact sensory nerve fibers,and later injured axons regenerate and new sprouts called neuromas develop.In recent years,analysis of corneal nerve abnormalities including corneal neuromas which can be identified using in vivo confocal microscopy,a non-invasive imaging technique with microscopic resolution,has been used to evaluate corneal neuropathy and ocular surface dysfunction.Corneal neuromas have been shown to be associated with clinical symptoms of discomfort and dryness of eyes,and are a promising surrogate biomarker for ocular surface diseases,such as neuropathic corneal pain,dry eye disease,diabetic corneal neuropathy,neurotrophic keratopathy,Sjogren's syndrome,bullous keratopathy,post-refra ctive surgery,and others.In this review,we have summarized the current literature on the association between these ocular surface diseases and the presentation of corneal microneuromas,as well as elaborated on their pathogenesis,visualization via in vivo confocal microscopy,and utility in monitoring treatment efficacy.As current quantitative analysis on neuromas mainly relies on manual annotation and quantification,which is user-dependent and labor-intensive,future direction includes the development of artificial intelligence software to identify and quantify these potential imaging biomarkers in a more automated and sensitive manner,allowing it to be applied in clinical settings more efficiently.Combining imaging and molecular biomarkers may also help elucidate the associations between corneal neuromas and ocular surface diseases.

Silicone oil as a corneal lubricant to reduce corneal edema and improve visualization during

AIM:To evaluate the efficacy and safety of silicone oil(SO)as a corneal lubricant to improve visualization during vitrectomy.METHODS:Patients who underwent vitreoretinal surgery were divided into two groups.Group 1 was operated on with initial SO(Oxane 5700)as a corneal lubricant.Group 2 was operated on with initial lactated ringer’s solution(LRS)and then replaced with SO as required.Fundus clarity was scored during the surgery.Fluorescein staining was performed to determine the damage to corneal epithelium.RESULTS:Totally 114 eyes of 114 patients were included.Single SO use maintained a clear cornea and provided excellent visualization of surgical image.In group 1,the fundus clarity was grade 3 in 41/45 eyes and grade 2 in 4/45 eyes.In group 2,corneal edema frequently occurred after initial LRS use.The fundus clarity was grade 3 in 19/69 eyes,2 in 37/69 eyes and 1 in 13/69 eyes(P<0.05).SO was applied in 29 eyes of initial LRS use with subsequent corneal edema,which eliminated the corneal edema in 26 eyes.Corneal fluorescein staining score in group 1 was 0 in 28 eyes,1 in 11 eyes and 2 in 6 eyes,and 40,20 and 9,respectively,in group 2(all P>0.05).CONCLUSION:The use of SO as a corneal lubricant is effective and safe for preserving and improving corneal clarity and providing clear surgical field during vitrectomy.

Ten-year observation of corneal densitometry and associated factors following small incision lenticule extraction

●AIM:To investigate the long-term changes of corneal densitometry(CD)and its contributing elements after small incision lenticule extraction(SMILE).●METHODS:Totally 31 eyes of 31 patients with mean spherical equivalent of-6.46±1.50 D and mean age 28.23±7.38y were enrolled.Full-scale examinations were conducted on all patients preoperatively and during followup.Visual acuity,manifest refraction,axial length,corneal thickness,corneal higher-order aberrations,and CD were evaluated.●RESULTS:All surgeries were completed successfully without complications or adverse events.Ten-year safety index was 1.17±0.20 and efficacy 1.04±0.28.CD value of 0–6 mm zones in central layer was statistically significantly lower 10y postoperatively,compared with preoperative values(0–2 mmΔ=-1.62,2–6 mmΔ=-1.24,P<0.01).There were no correlations between CD values and factors evaluated.●CONCLUSION:SMILE is a safe and efficient procedure for myopia on a long-term basis.CD values get lower 10y postoperatively,whose mechanism is to be further discussed.

Distribution and correlation of refractive parameters in children with different corneal curvatures in southeast China

AIM:To analyze the distribution of refractive status in school-age children with different corneal curvatures(CC)and the correlation between CC and refractive status.METHODS:A total of 2214 school-aged children of grade 4 in Hangzhou who were screened for school myopia were included.Uncorrected distance visual acuity(UCDVA),non-cycloplegic refraction,axial length(AL),horizontal and vertical corneal curvature(K1,K2)were measured and spherical equivalent(SE),corneal curvature radius(CCR)and axial length/corneal radius of curvature ratio(AL/CR)were calculated.UCDVA<5.0 and SE≤-0.50 D were classified as school-screening myopia.According to the different CCRs,the patients were divided into the lower corneal curvature(LCC)group(CCR≥7.92)and the higher corneal curvature(HCC)group(CCR<7.92).Each group was further divided into the normal AL subgroup and the long AL subgroup.The refractive parameters were compared to identify any differences between the two groups.RESULTS:Both SE and AL were greater in the LCC group(P=0.013,P<0.001).The prevalence of myopia was 38% in the LCC group and 44% in the HCC group(P<0.001).The proportion of children without screening myopia was higher in the LCC group(62%)than in the HCC group(56%).Among these children without screening myopia,the proportion of long AL in the LCC group(24%)was significantly higher than that in the HCC group(0.012%;P<0.001).The change of SE in the LCC group was less affected by the increase of AL than that in the HCC group.CONCLUSION:School-aged children in the LCC group have a lower incidence of screening myopia and longer AL.Low CC can mask SE reduction and AL growth to some extent,and the change of AL growth change more in children with low CC than high CC.Before the onset of myopia,its growth rate is even faster than that after the onset of myopia.