Comparison of corneal biological parameters between transepithelial and epithelium-off corneal cross-linking in keratoconus

AIM:To evaluate the differences in corneal biological parameters between transepithelial and epithelium-off corneal cross-linking in keratoconus.METHODS:In our prospective clinical trial,40 patients(60 eyes)with progressive keratoconus were randomized to undergo corneal cross-linking with transepithelial(TE group,n=30)or epithelium-off(EO group,n=30)keratoconus.Examinations comprised topography,corneal biomechanical analysis and specular microscopy at 6 mo postoperatively.RESULTS:The keratometer values were not significantly different between the TE and EO corneal cross-linked groups in different periods(each P>0.05).The corneal thickness of the EO group was greater than that of the TE group at 1 wk after the operation(each P<0.05).Regarding corneal biomechanical responses,the EO group showed a longer second applanation length than TE group(P=0.003).Regarding the corneal endothelial function,standard deviation of the endothelial cell size,and coefficient of variation in the cell area,the values of EO group were larger than those of TE group at 1 wk(P=0.011,0.026),and the percentage of hexagonal cells in EO group was lower than that in TE group at 1 and 6 mo(P=0.018,0.019).CONCLUSION:Epithelium-off corneal cross-linking may strengthen corneal biomechanics better than TE procedure can.However,the TE procedure with a lower ultraviolet-A irradiation intensity would be safer for corneal endothelial function.

Reconstruction of Rabbit Corneal Layer Composed of Corneal Fibroblasts and Corneal Epithelium on the Lyophilized Amniotic Membrane

Many researchers have employed the cryopreserved amniotic membrane（CAM） and corneal epithelial cells in the treatment of a severely damaged burned cornea, with corneal epithelial cells cultured on an amniotic membrane （AM）. The lyophilized amniotic membrane（LAM） has a higher graft take and a longer shelf life; it is easier to store and safer because of gamma irradiation. Two Teflon rings（ Ahn＇s supporter） were made for culturing the cells on the LAM, and were then used to support the LAM. To reconstruct a corneal layer composed of corneal fibroblasts and epithelium, the corneal fibroblasts were first cultivated on the stromal side of LAM for five days, foUowed by epithelial cells culture on the epithelial side, by using the air-liquid interface culture. The reconstructed corneal layer composed of corneal fibroblasts and corneal epithelial cells has a much healthier basal layer of corneal epithelium than the reconstructed corneal epithelium, which was got by using only corneal epithelial cells, and resembles the epithelium of normal corneas, without the horny layer. Thus, the reconstruction of the corneal layer by using a LAM is considered to be a good in vitro model, not only for its application in toxicological test kits, but also for transplantation in patients with a severely damaged cornea.

Transplantation of tissue-engineered human corneal epithelium in limbal stem cell deficiency rabbit models

AIM: To evaluate the biological functions of tissue-engineered human corneal epithelium (TE-HCEP) by corneal transplantation in limbal stem cell deficiency (LSCD) rabbit models. METHODS: TE-HCEPs were reconstructed with DiI-labeled untransfected HCEP cells and denuded amniotic membrane (dAM) in air-liquid interface culture, and their morphology and structure were characterized by hematoxylin-eosin (HE) staining of paraffin-sections, immunohistochemistry and electron microscopy. LSCD models were established by mechanical and alcohol treatment of the left eyes of New Zealand white rabbits, and their eyes were transplanted with TE-HCEPs with dAM surface outside by lamellar keratoplasty (LKP). Corneal transparency, neovascularization, thickness, and epithelial integrality of both traumatic and post transplantation eyes were checked once a week by slit-lamp corneal microscopy, a corneal pachymeter, and periodic acid-Schiff (PAS) staining. At day 120 post surgery, the rabbits in each group were sacrificed and their corneas were examined by DiI label observation, HE staining, immunohistochemistry and electron microscopy. RESULTS: After cultured for 5 days on dAM, HCEP cells, maintaining keratin 3 expression, reconstructed a 6-7 layer TE-HCEP with normal morphology and structure. The traumatic rabbit corneas, entirely opaque, conjunctivalized and with invaded blood vessels, were used as LSCD models for TE-HCEP transplantation. After transplantation, obvious edema was not found in TE-HCEP-transplanted corneas which became more and more transparent, the invaded blood vessels reduced gradually throughout the monitoring period. The corneas decreased to normal thickness on day 25, while those of dAM eyes were over 575 mu m in thickness during the monitoring period. A 45 layer of epithelium consisting of TE-HCEP originated cells attached tightly to the anterior surface of stroma was reconstructed 120 days after TE-HCEP transplantation, which was similar to the normal control eye in morphology and structure. In contrast, intense corneal edema, turbid, invaded blood vessels were found in dAM eyes, and no multilayer epithelium was found but only a few scattered conjunctiva-like cells appeared. CONCLUSION: The TE-HCEP, with similar morphology and structure to those of innate HCEP, could reconstruct a multilayer corneal epithelium with normal functions in restoring corneal transparency and thickness of LSCD rabbits after transplantation. It may be a promising HCEP equivalent for clinical therapy of corneal epithelial disorders.

In vitro reconstruction and characterization of tissue-engineered human corneal epithelium with seeder cells from an untransfected human corneal epithelial cell line

AIM: To demonstrate the morphology and structure of in vitro reconstructed tissue-engineered human corneal epithelium (TE-HCEP) with seeder cells from an untransfected HCEP cell line. METHODS: The TE-HCEPs were reconstructed in vitro with seeder cells from an untransfected HCEP cell line, and scaffold carriers of denuded amniotic membrane (dAM) in air-liquid interface culture for 3, 5, 7 and 9 days, respectively. The specimens were examined with hematoxylin-eosin (HE) staining of paraffin-section, immunocytochemical staining, scanning and transmission electron microscopy. RESULTS: During in vitro reconstruction of TE-HCEP, HCEP cells formed a 3-4, 6-7 and 8-10 layers of an HCEP-like structure on dAMs in air-liquid interface culture for 3, 5 and 7 days, respectively. But the cells deceased to 5-6 layers and the structure of straified epithelium became loose at day 9. And the cells maintained positive expression of marker proteins (keratin 3 and keratin 12), cell-junction proteins (zonula occludens-1, E-cadherin, connexin 43 and integrin beta 1) and membrane transport protein of Na+-K+ ATPase. The HCEP cells in TE-HCEP were rich in microvilli on apical surface and established numerous cell-cell and cell-dAM junctions at day 5. CONCLUSION: The morphology and structure of the reconstructed TE-HCEP were similar to those of HCEP in vivo. The HCEP cells in the reconstructed TE-HCEP maintained the properties of HCEP cells, including abilities of forming intercellular and cell-extracellular matrix junctions and abilities of performing membrane transportation. The untransfected HCEP cells and dAMs could promisingly be used in reconstruction HCEP equivalent for clinical corneal epithelium transplantation.

Alcohol delamination of the corneal epithelium for recurrent corneal erosion syndrome

AIM： To evaluate the outcomes of alcohol delamination（ALD） of the corneal epithelium for the treatment of recurrent corneal erosion syndrome（RCES） and to implement a standardized treatment protocol for this condition utilizing evidence based practice and the findings of an internal audit. METHODS： A retrospective analysis of 42 eyes of 40 patients diagnosed with RCES who were treated with ALD between January 2006 and March 2016 was conducted. Patients had 20% alcohol applied to the cornea with the use of a well for 40 s. Patients were reviewed one week later in the Outpatient Department. Outcome criteria were established based on standards from other studies in the medical literature. These included, a treatment success rate of at least 72%（defined as complete resolution of symptoms one month after treatment）, a postoperative complication a rate of 〈5%（mainly infective keratitis, and subepithelial haze）, and the absence of any detrimental effect on visual acuity in ≥95% of patients. RESULTS： The mean age at the time of ALD was 41.17±13.44 y. Patients were followed for an average of 12.8±15.65 mo. The majority were female（52.5%, n=21） and the majority of eyes treated with ALD were left eyes（62.9%, n=26）. Trauma was the primary aetiology in our study population. Treatment was successful in 73.8%（n=31） of eyes and in 75%（n=30） of patients. Recurrence occurred in 26.2% of eyes at a mean of 10.41±12.63 mo post treatment. CONCLUSION： ALD is an efficacious and cost-effective primary surgical intervention for RCES.

Netrin-1 promotes epithelium repair in corneal injury

●AIM:To explore netrin-1 functions on corneal epithelium in vitro and in vivo.●METHODS:In vitro the human corneal epithelial(HCE)cells were treated with serum free DMEM-F12 basic media containing 0,50,100,200,300,500,800,and 1000 ng/mL of netrin-1,respectively.The cells viability was detected by cell counting kit-8(CCK-8).The wound-healing assay was applied to assess the migration proficiency of HCE cells.Flow cytometry was used to analyze the cell-cycle distribution and apoptosis.In vivo,normal c57(6 wk)mice were demarcated with a trephine in the middle of the cornea to produce a 3-mm circular wound.Mice corneas were inflicted no epithelium with a 3-mm wound displayed,but remained the limbal epithelium intact.A blunt scalpel blade was used to remove the corneal epithelian cells,followed by topical netrin-1 application(200 ng/mL),and the group treated by PBS as control.The treated group was injected netrin-1 into the normal c57 mice inferior subconjunctival 4 h before trauma.Mouse corneal inflammation and neovascularization were observed under slit lamp microscope.The apoptosis of corneal cells was determined by TUNEL staining.●RESLUTS:A concentration of 200 ng/mL netrin-1 enhanced 25%of the HCE viability.The relative migration rates were 76.3%and 100%in control and netrin-1 treated group after cultured 72 h.Treated with netrin-1(200 ng/mL)decreased the apoptosis of HCE cells,as well as decreased their percentage from 19.3%±0.57%to 12.7%±0.42%of the total.The remaining wound area was 1.22 mm2 in control group but 0.22 mm2 in the netrin-1 treated group.Exogenous Netrin-1 inhibits apoptosis of corneal epithelial cells of c57 mice.TUNEL-positive cells at the epithelial layer of the corneas of the control and netrin-1 treated c57 mice at 24 h after wounding were 43.3%and 16.7%respectively.●CONCLUSION:Netrin-1 can reduce HCE apoptosis as well as promote its proliferation and migration.Topical application of netrin-1 promotes the injuryed cornea epithelial wound repair and inhibits apoptosis of corneal epithelial cells.These findings may offer potential therapies to repair the defects of corneal epithelial based on netrin-1.

TREM-1 expression in rat corneal epithelium with Aspergillus fumigatus infection

AIM: To investigate the expression of triggering receptor expressed on myeloid cells-1(TREM-1) in the aberrant inflammation within the corneal epithelium at early period of fungal infection.METHODS: A total of 65 Wistar rats were randomly divided into control group, sham group and fungal keratitis(FK) group, in which the cornea was infected by Aspergillus fumigatus(A. fumigatus). After executed randomly at 8, 16, 24, 48 and 72 h after experimental model being established, the severity of keratomycosis in rats was scored visually with the aid of a dissecting microscope and slit lamp. Then corneas in three groups were collected to assess the expression of TREM-1through quantitative reverse transcription-polymerase chain reaction(RT-PCR), immunofluorescence technique and Western blot analysis. The correlation between FK inflammation and expression of TREM-1 was also analyzed.RESULTS: Corneal inflammation scores increased with time after fungal infection(F =49.74, P =0.000). The inflammation scores in FK group were obviously higher than those in sham group on the whole(F =137.78, P =0.000). Levels of TREM-1 in the infected rat corneal epithelium had elevated at 8h and peaked at 48h(P 【0.001,compared with control group). Western blot analysis also showed an obviously elevated TREM-1 level in rat corneal epithelium at 24 h and 48 h after fungal infection.Immunofluorescence technique showed that TREM-1mainly existed in corneal epithelium and infected corneal stoma of rat. TREM-1 protein expression was enhanced after fungal infection. Moreover, severity of FK inflammation was significantly related to TREM-1expression in FK(r =0.942, P =0.000).CONCLUSION: TREM-1 may contribute to amplify theinflammation in the cornea infected with A. fumigatus and play critical roles in the battle against A. fumigatus in the innate immune responses.

Expression of vitamin D receptor and cathelicidin in human corneal epithelium cells during fusarium solani infection

AIMTo observe the expression of vitamin D receptor (VDR) in human specimen and immortalized human corneal epithelium cells (HCEC) when challenged with fusarium solani. Moreover, we decided to discover the pathway of VDR expression. Also, we would like to detect the expression of cathelicidin antimicrobial peptide (CAMP) in the downstream pathway of VDR.METHODSImmunohistochemistry was used to examine the VDR expression in HCEC from healthy and fungal keratitis patients. Real time quantitative polymerase chain reaction (qPCR) was performed to observe the messenger ribonucleic acid (mRNA) change of VDR when immortalized HCEC were challenged with fusarium solani for different hours. CAMP was detected at both mRNA and protein levels.RESULTSWe found out that the VDR expression in fusarium solani keratitis patients' specimen was much more than that in healthy people. The mRNA and protein expression of VDR increased when we stimulated HCEC with fusarium solani antigen (P&#x0003c;0.01) and it could be inhibited by toll like receptor 2 (TLR2) monoclonal antibody. The CAMP expression was decreased because of fusarium solani antigen stimulation (P&#x0003c;0.01).CONCLUSIONThe VDR expression can be increased via TLR2/1-VDR pathway while the CAMP expression is decreased by the stimulation of fusarium solani antigen.

Anti-inflammatory and anti-apoptotic effects of N-acetylcysteine in diabetic rat corneal epithelium

AIM:To characterize the anti-inflammatory and antiapoptotic effects of N-acetylcysteine(NAC)in streptozotocin(STZ)-induced diabetic rat corneal epithelium and human corneal epithelial cells(HCECs)exposed to a high-glucose environment.METHODS:HCECs were incubated in 0,5,50 mmol/L glucose medium,or 50 mmol/L glucose medium with NAC for 24h.Diabetes was induced in rats by intraperitoneal injection of 65 mg/kg STZ and some of these rats were topically administered NAC to corneas with 3 mice per group.We characterized receptor for advanced glycation end-products(RAGE)expression using immunofluorescence,and interleukin(IL)-1βand cleaved caspase-3(CCAP-3)expression using immunohistochemistry.Circulating tumor necrosis factor(TNF)-αconcentration was measured by ELISA and cleaved poly-ADP ribose polymerase(PARP)concentration was quantified by Western blotting.Apoptotic cells were detected using TUNEL assay and annexin V and propidium iodide staining.RESULTS:Diabetic rats had higher expression of RAGE(2.46±0.13 fold),IL-1β,and CCAP-3 in apoptotic cells of their corneas than control rats.The expression of RAGE(1.83±0.11 fold),IL-1β,and CCAP-3,and the number of apoptotic cells,were reduced by topical NAC treatment.HCECs incubated in 50 mmol/L glucose medium showed high concentrations of TNF-α(310±2.00 pg/mL)and cleaved PARP(7.43±0.56 fold),and more extensive apoptosis than cells in 50 mmol/L glucose medium.However,the addition of NAC reduced the concentrations of TNF-α(153.67±2.31 pg/mL)and cleaved PARP(5.55±0.31 fold)and the number of apoptotic cells.CONCLUSION:NAC inhibits inflammation and apoptosis in the corneas of diabetic rats and HCECs maintained in a high-glucose environment.

Central corneal epithelium self-healing after ring-shaped glycerin-cryopreserved lamellar keratoplasty in Terrien marginal degeneration

Dear Sir, I am Dr Yan-Long Bi, from the Department of Ophthalmology, Tongji University Affiliated to Tongji University School of Medicine, Shanghai, China. I write to present a case report of total limbal stem cells deficiency after treatment with ring-shaped lamellar keratoplasty secondary to Terrien marginal degeneration. During 3 years

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.

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.

EFFECT OF HUMAN AMNIOTIC MEMBRANE ON CORNEAL EPITHELIUM AND YAC-1 CELL

Objective To study the effect of the amniotic membrane on enhancing the proliferation ofcorneal epithelia and YAC-1 cell. Methods After the primary culture of the rabbit's corneal epithelia and YAC-1 cells, they were seeded on the upper surface or stromal matrix side of amniotic membrane respectively. The proliferation results were observed by MTT test. Results The amniotic membrane was found significantly enhancing the proliferation of corneal epithelia on the d1 ,d3 , and d5 after culture. The proliferation rate was 28.93% ,23.32% ,23.41 % (P<0 .05) respectively, but the d7 proliferation rate was 20.72% (P> 0.05). On the dl , d3 , d7 after culture , the YAC-1 cells proliferation rate was 34 .87% ,36 .28% ,33 .86% (P< 0.01) respectively. Conclusion Our results demonstrated that the amniotic membrane could enhance the proliferation of both corneal epithelia and YAC-1 cells significantly. Although amniotic membrane has been suggested as an ideal material for reconstruction of ocular surface, special attention should be paid during amniotic membrane transplantation for treating ocular surface lesion resulted from epibulbar tumors.

Regulation of interleukin 33/ST2 signaling of human corneal epithelium in allergic diseases

AIM:To identify the function of ST2 and explore the role of IL-33/ST2 signaling in regulating the pro-allergic cytokine production in human corneal epithelial cells (HCECs). METHODS:Human corneal tissues and cultured primary HCECs were treated with IL-33 in different concentrations without or with different inhibitors to evaluate the expression, location and signaling pathways of ST2 in regulating production of pro-allergic cytokine and chemokine. The expression of mRNA was determined by reverse transcription and real time PCR, and protein production was measured by enzyme-linked immunosorbent assay (ELISA), immunohistochemical and immunofluorescent staining. ST2 protein was detected in donor corneal epithelium, and ST2 signal was enhanced by exposure to IL-33. ·RESULTS:IL-33 significantly stimulated production of pro-allergic cytokines thymic stromal lymphopoietin (TSLP) and chemokine (CCL2, CCL20, CCL22) in HCECs at both mRNA and protein levels. These stimulated productions of pro-allergic mediators by IL-33 were blocked by ST2 antibody or soluble ST2 protein(P 【0.05). Interestingly, the IκB-α inhibitor BAY11-7082 or NF-κB activation inhibitor quinazoline blocked NF-κB p65 protein nuclear translocation, and also suppressed the productions of these pro-allergic cytokines and chemokine induced by IL-33. CONCLUSION:These findings demonstrate that IL-33/ ST2 signaling plays an important role in regulating IL-33 induced pro-allergic responses. IL-33 and ST2 could become novel molecular targets for the intervention ofallergic diseases in ocular surface.

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.

Efficacy of iontophoresis-assisted epithelium-on corneal cross-linking for keratoconus

Corneal cross-linking（CXL） is a noninvasive therapeutic procedure for keratoconus that is aimed at improving corneal biomechanical properties by induction of covalent cross-links between stromal proteins. It is accomplished by ultraviolet A（UVA） radiation of the cornea, which is first saturated with photosensitizing riboflavin. It has been shown that standard epithelium-off CXL（S-CXL） is efficacious, and it has been recommended as the standard of care procedure for keratoconus. However, epithelial removal leads to pain, transient vision loss, and a higher risk of corneal infection. To avoid these disadvantages, transepithelial CXL was developed. Recently, iontophoresis has been adopted to increase riboflavin penetration through the epithelium. Several clinical observations have demonstrated the safety and efficacy of iontophoresisassisted epithelium-on CXL（I-CXL） for keratoconus. This review aimed to provide a comprehensive summary of the published studies regarding I-CXL and a comparison between I-CXL and S-CXL. All articles used in this review were mainly retrieved from the Pub Med database. Original articles and reviews were selected if they were related to the I-CXL technique or related to the comparison between I-CXL and S-CXL.

Evaluation of corneal parameter changes under different accommodative stimuli with Scheimpflug imaging-based tomography

AIM:To evaluate the reliability of measurements of corneal changes with accommodation in healthy eyes using a Scheimpflug imaging-based system and how these measurements distribute in the normal population.METHODS:Prospective,non-randomized,comparative study including 27 healthy subjects(54 eyes),including emmetropia(13 eyes),myopia(17 eyes),hyperopia(4 eyes)and astigmatism(20 eyes)groups.In all cases,a complete eye examination was performed,including the analysis of corneal changes with different accommodative stimuli(+2.00,0.00 and-3.00 D)using the Pentacam AXL system.The investigation was structured in 2 phases:repeatability analysis and characterization of accommodation-related corneal changes in healthy populations.RESULTS:In the repeatability analysis,the index of height asymmetry(IHA)showed the greatest variability with the three accommodative stimuli,being the results for the rest of parameters acceptable.The group of emmetropes showed significant differences with accommodative changes in the position of maximum keratometry(Kmax;P<0.05),whereas in the astigmatism group,significant changes were not only observed in the position of Kmax,but also in minimum corneal thickness(MCT),corneal spherical aberration,and total and low order aberration root mean square(all P<0.05).Likewise,a significant difference was found in the displacement of the X position of Kmax with+2.00 D and-3.00 D in the myopia group(P=0.033)as well as in changes with+2.00 D and-3.00 D in the magnitude of the position vector of Kmax in the emmetropia group(P<0.05).No significant changes were found between accommodative stimuli in the displacement of coordinates of MCT(P≥0.109).CONCLUSION:The position of Kmax and MCT in healthy corneas can change significantly when presenting different accommodative stimuli using the accommodation mode of the Pentacam system,with different trends in these accommodation-related corneal changes between refractive errors.Likewise,the consistency of the measurements obtained with Scheimpflug has been confirmed.

Resistant corneal ulcers in a tertiary care ophthalmic center in Egypt: 10 years epidemiological study

AIM:To investigate the magnitude of problem caused by resistant corneal ulcers and its epidemiological characteristics.METHODS:Patients with corneal lesions were selected and carefully examined and cases with resistant corneal ulcers were further investigated and data were recorded using a specific data sheet designed in hospital.Then,collected data from patients were statistically analyzed.RESULTS:Totally 1939 cases were included in the study,including 816 fungal cases(42.1%)and 1123(57.9%)non-fungal cases.Age of the participants ranged from 18 to 73y.Fungal cases were more common in middle age(35-55y).Men were more affected(53.5%)of cases included in the study.Keratomycosis affected more unskilled personnel(75.1%),large families with small houses(higher crowding index 73.9%),rural(64.5%)residence.Patients with sanitary water sources(34.8%)and waste disposal(24.4%)were less affected.CONCLUSION:Keratomycosis is more frequent in unskilled personnel,rural locations,outdoor water sources and insanitary waste disposal systems.Corneal trauma and contact lens are common risk factors.

Corneal and intraocular pressure changes associated to the circadian rhythms:a narrative review

AIM:To synthesize the current body of research regarding the diurnal variations in intraocular pressure(IOP)and corneal biomechanical and morphological parameters,highlighting their significance in various eye conditions.METHODS:A comprehensive review of studies on the diurnal variations of IOP and corneal parameters was conducted.Tonometry findings from various studies were assessed,including the Goldmann applanation tonometry(GAT)and non-contact tonometers.Data on the variations in central corneal thickness(CCT),corneal curvature,and corneal biomechanics measured by the Ocular Response Analyzer system across different population groups was extracted and analyzed.RESULTS:In both healthy subjects and those with Fuchs dystrophy,IOP and CCT demonstrate marked diurnal declines.GAT remains the gold standard for tonometry,with the highest reliability.However,its measurements are influenced by CCT.Keratoconus patients and those with pseudoexfoliation showed significant diurnal variations in IOP.The biomechanical parameters,especially corneal hysteresis(CH)and the corneal resistance factor(CRF),largely remain stable throughout the day for most of eye conditions,with some exceptions.Notably,the corneal morphology diurnal variation,particularly curvature,yielded mixed conclusions across studies.CONCLUSION:Circadian rhythms significantly influence various corneal parameters,most notably IOP and CCT.Further studies should emphasize standardized approaches larger sample sizes,and delve deeper into less-explored areas,such as the effects of orthokeratology lenses on diurnal biomechanical shifts.

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.