Changes in intraocular pressure and central corneal thickness during pregnancy:a systematic review and Meta-analysis

AIM:To conduct a Meta-analysis for investigating the variations in intraocular pressure(IOP) and central corneal thickness(CCT) during normal pregnancy.METHODS:We searched for clinical trials published up to November 2015 without language or region restrictions in Pub Med,EMBASE,Web of Science,the Cochrane Central Register of Controlled Trials,Ovid,EBSCO,Elsevier,the Chinese Biomedicine Database,Wan Fang,CNKI,CQVIP and Google Scholar.Studies of the ocular changes observed in pregnant women were selected.The main outcomes were assessed by changes in IOP and CCT.RESULTS:Fifteen studies were included.In subgroup analyses,IOP was significantly decreased during the second MD=-1.53,95%CI(-2.19,-0.87);P<0.00001,and third MD=-2.91,95%CI(-3.74,-2.08);P<0.00001 trimesters of pregnancy.CCT was increased during the second MD=10.12,95%CI(2.01,18.22);P=0.01,trimester of pregnancy;moreover,during the third trimester of pregnancy,the CCT displayed an increasing trend,but the difference was not significant MD=5.98,95%CI(-1.11,13.07);P=0.1.CONCLUSION:A decrease in IOP is accompanied by an increase in CCT in the second and third trimesters of a normal pregnancy in women.

Effect of 2% fluorescein on Scheimpflug central corneal thickness measurements

AIM: To assess central corneal thickness(CCT)changes measured with Scheimpflug device following instillation of 2% fluorescein in normal subjects.·METHODS: This was a prospective randomized study of 60 hospital volunteers. After baseline CCT measurements of both eyes of 40 subjects were obtained using Scheimpflug system, a drop of preservative-free2% fluorescein, was instilled in one eye and in other eye,one drop of normal saline(control). Measurements were repeated after 1, 2, 5, 10, 20, 30, 40, 50 and 60min(continuous assessment group). Twenty subjects had baseline CCT taken, then fluorescein was instilled in one eye and measurements were taken at 1min. Ten eyes had saline rinse after 1min and 10 other eyes did not,measurements were repeated at 2min(eye rinse group).· RESULTS: The mean baseline CCT for continuous assessment group was 546.2±32.1 μm(range, 489.0-606.0),control eyes was 546.6±30.7 μm(range, 489.0-602.0). At1 min after fluorescein instillation, CCT significantly increased by 37.0 ±34.0 μm(P <0.001), then decreased gradually, reaching baseline at 60 min. CCT variations were not significant in control group(P >0.05). For eye rinse group, CCT mean differences between baseline and 2min were 18.2 μm(95 % CI:-54.7 to 18.3) with rinse and 26.5 μm(95% CI:-62.9 to 9.9) without rinse; paired sample tests were not significant(P >0.05).·CONCLUSION: The presence of fluorescein increased CCT value to a clinically relevant level of 6.8%. Eye rinse did not significantly reduce the effect at 2min post fluorescein timepoint.

Sirius Scheimpflug-Placido versus. ultrasound pachymetry for central corneal thickness: meta-analysis

Background:To compare the difference in central corneal thickness(CCT)measurements in normal eyes between a rotating Scheimpflug camera combined with a Placido-disk corneal topographer(Sirius,CSO,Italy)and ultrasound pachymetry(USP).Methods:A systematic literature search was conducted for relevant studies published on PubMed,Medline,EMBASE,and the Cochrane Library and ClinicalTrials.gov from inception to August 1st,2019.Primary outcome measures were CCT measurements between Sirius and USP.A random effects model was used to pool CCT measurements.Results:A total of twelve studies involving 862 eyes were included in this meta-analysis.The meta-analysis found CCT measurements between Sirius and USP to be statistically significantly different(P<0.0001).The mean difference between Sirius and USP was-11.26μm with a 95%confidence interval(CI)(-16.92μm,-5.60μm).The heterogeneity Was IP=60%(P=0.004).Conclusion:CCT measurements with the Sirius Scheimpflug-Placido topographer were statistically significantly lower than USP.However,it may be argued that the mean difference of 11.26μm is not a clinically significant difference.

Sirius Scheimpflug–Placido versus ultrasound pachymetry for central corneal thickness:meta-analysis

Background:To compare the difference in central corneal thickness(CCT)measurements in normal eyes between a rotating Scheimpflug camera combined with a Placido-disk corneal topographer(Sirius,CSO,Italy)and ultrasound pachymetry(USP).Methods:A systematic literature search was conducted for relevant studies published on PubMed,Medline,EMBASE,and the Cochrane Library and ClinicalTrials.gov from inception to August 1st,2019.Primary outcome measures were CCT measurements between Sirius and USP.A random effects model was used to pool CCT measurements.Results:A total of twelve studies involving 862 eyes were included in this meta-analysis.The meta-analysis found CCT measurements between Sirius and USP to be statistically significantly different(P<0.0001).The mean difference between Sirius and USP was−11.26μm with a 95%confidence interval(CI)(−16.92μm,−5.60μm).The heterogeneity was I^(2)=60%(P=0.004).Conclusion:CCT measurements with the Sirius Scheimpflug-Placido topographer were statistically significantly lower than USP.However,it may be argued that the mean difference of 11.26μm is not a clinically significant difference.

Impact of corneal parameters on intraocular pressure measurements in different tonometry methods

AIM: To evaluate the impact of central corneal thickness(CCT) and corneal curvature on intraocular pressure(IOP) measurements performed by three different tonometers. METHODS: IOP in 132 healthy eyes of 66 participants was measured using three different tonometry techniques: Goldmann applanation tonometer(GAT), Pascal dynamic contour tonometer(DCT), and ICare rebound tonometer(RT). CCT and corneal curvature were assessed. RESULTS: In healthy eyes, DCT presents significantly higher values of IOP than GAT(17.34±3.69 and 15.27±4.06 mm Hg, P<0.0001). RT measurements are significantly lower than GAT(13.56±4.33 mm Hg, P<0.0001). Compared with GAT, DCT presented on average 2.51 mm Hg higher values in eyes with CCT<600 μm and 0.99 mm Hg higher results in eyes with CCT≥600 μm. The RT results were lower on average by 1.61 and 1.95 mm Hg than those obtained by GAT, respectively. Positive correlations between CCT in eyes with CCT<600 μm were detected for all IOP measurement techniques, whereas a similar relationship was not observed in eyes with thicker corneas. A correlation between IOP values and keratometry in the group with CCT<600 μm was not detected with any of the tonometry methods. In thicker corneas, a positive correlation was found for GAT and mean keratometry values(R=0.369, P=0.005). CONCLUSION: The same method should always be chosen for routine IOP control, and measurements obtained by different methods cannot be compared. All analysed tonometry methods are dependent on CCT;thus, CCT should be taken into consideration for both diagnostics and monitoring.

Comparing corneal outcome between femtosecond laser-assisted cataract surgery and conventional phaco surgery in Fuchs’endothelial dystrophy patients:a randomized pilot study with 6mo follow up

AIM:To compare the corneal outcome in Fuchs’endothelial dystrophy(FED)patients between femtosecond laser-assisted cataract surgery(FLACS)and conventional phaco surgery(CPS).METHODS:This was a randomized controlled study comparing one eye surgery by FLACS and the contralateral eye operated by CPS(stop and chop technique)in FED patients.Central corneal thickness,corneal light backscatter,corneal densitometry,and central corneal endothelial cell count and hexagonality(noncontact endothelial cell microscope),and corrected distance visual acuity(CDVA)were assessed preoperatively and at day 1,40,and 180 postoperatively.RESULTS:Totally 31 patients(16 women)were included.At day 40 postoperatively,the mean endothelial cell loss(ECL)was 23.67%by FLACS and 17.30%by CPS(P=0.53).At day 180 postoperatively,ECL was 25.58%in FLACS and 21.32%in CPS(P=0.69).Densitometry data in all layers and all annuli from anterior layer to posterior layer in annuli 0-2,2-6,6-10 and 10-12,total densitometry with all layers and all annuli was performed.A significant difference was found in 6-10(posterior layer)at day 1 with-1.42 grayscale units(GSU;95%CI:-2.66 to-0.19,P=0.02).In 10-12(anterior layer,central layer and all layers)at day 40 were significant different with 7.7(95%CI:1.89 to 13.50,P=0.009),3.97(95%CI:0.23 to 7.71,P=0.03),4.73 GSU(95%CI:0.71 to 8.75,P=0.02),respectively.In the remaining parameters we found no difference between the two groups(P>0.05).Three CPS eyes suffered from corneal decompensation.CONCLUSION:There is no significant difference in corneal outcome between FLACS and CPS.Endothelial cell density and pentacam corneal outcome may be inadequate as outcome parameters in FED patients.

Changes of lactate dehydrogenase in corneal edema after cataract surgery treated with trans-corneal oxygenation therapy

AIM:To investigate the changes in levels of the lactate dehydrogenase(LDH)enzyme in corneal edema after cataract surgery with trans-corneal oxygenation therapy.METHODS:This pre-post design study design conducted on 15 patients with corneal edema after cataract surgery and receiving trans-corneal oxygenation therapy.Tear sample(using Schirmer paper,from the inferior fornix of the conjunctiva)was carried out prior to trans-corneal oxygenation therapy,on the day 2(D2)and day 5(D5)postoperatively before and after trans-corneal oxygenation therapy.Visual acuity[VA(Log MAR)],corneal endothelial density,central corneal thickness(CCT),and coefficient of variation corneal endothelial(Co V)were recorded.The value of LDH was measured using ELISA.The difference in mean LDH value before and after trans-corneal oxygenation therapy,between two groups were analyzed using Wilcoxon signed rank test.RESULTS:There was a decrease in LDH tear concentration at D2(pre vs post:1127.54±497.09 vs 696.91±489.49;P=0.002)and D5(pre vs post:1064.17±677.77 vs 780.28±428.95;P=0.027)after trans-corneal oxygenation therapy as well as decrease in LDH concentration on the D2 compared to D5(P=0.041).The mean CCT was decreased significantly after the administration of trans-corneal oxygenation(pre vs post:632.10±25.66 vs 563.90±51.54;P=0.005).The mean VA and Co V increased significantly after the administration of trans-corneal oxygenation(P=0.001 and P=0.028,respectively).However,there was no difference in mean of corneal endothelial density(P=0.814).CONCLUSION:Trans-corneal oxygenation therapy is associated with significant decrease of tears LDH levels in post cataract surgery with corneal edema.It is accompanied by clinical improvement such as significant reduction of CCT.

Agreement of intraocular pressure measurement with Corvis ST,non-contact tonometer,and Goldmann applanation tonometer in children with ocular hypertension and related factors

AIM:To access the agreement of intraocular pressure(IOP)values obtained from biomechanically corrected tonometer[Corvis ST(CST)],non-contact tonometer(NCT),and Goldmann applanation tonometer(GAT)in children with NCT measured-IOP(NCT-IOP)values of 22 mm Hg or more,and related factors.METHODS:A total of 51 eyes with NCT-IOP≥22 mm Hg in children aged 7 to 14y were examined and IOP was measured by CST,NCT,and GAT.Based on GAT measured IOP(GAT-IOP),ocular hypertension(OHT)group(≥22 mm Hg,24 eyes)and the non-OHT group(<22 mm Hg,27 eyes)were defined.We compared the agreement of the three measurements,i.e.,CST measured IOP(CST-IOP),GAT-IOP,and NCT-IOP,and further analyzed the correlation between the differences in tonometry readings,central corneal thickness(CCT),axial length(AL),optic disc rim volume,and age.RESULTS:Compared with the OHT group,thicker CCT,larger rim volume,and higher differences between NCTIOP and GAT-IOP,were found in the non-OHT group.The differences between CST-IOP and GAT-IOP were lower than the differences between NCT-IOP and GAT-IOP in both groups.The mean differences in CST-IOP and GAT-IOP were 1.26 mm Hg(95%limit of agreement ranged from 0.1 to 2.41 mm Hg,OHT group)and 1.20 mm Hg(95%limit of agreement ranged from-0.5 to 3.00 mm Hg,non-OHT group),and the mean differences in NCT and GAT were 3.90 mm Hg(95%limit of agreement ranged from-0.19 to 9.70 mm Hg,OHT group)and 6.00 mm Hg(95%limit of agreement ranged from 1.50 to 10.50 mm Hg,non-OHT group).The differences between CST-IOP and GAT-IOP were not related to CCT,age,and AL in both groups;while the differences between NCT-IOP and GAT-IOP were related to CCT in the OHT group(r=0.93,P<0.001)and to CCT and AL in the non-OHT group(r=0.66,P<0.001,r=-0.81,P<0.001).CONCLUSION:The accuracy of NCT in the diagnosis of pediatric OHT is low.The agreement of CST-IOP and GATIOP was significantly higher in children with and without OHT than in those with NCT-IOP and GAT-IOP.Therefore,CST can be used as a good alternative for IOP measurement in children.The impacts of CCT and AL on NCT measurement need to be fully considered when managing childhood IOP.

Destructive effects on endothelial cells of grafts in cytomegalovirus DNA-positive patients after keratoplasty

AIM:To investigate corneal graft survival rate and endothelial cell density(ECD)loss after keratoplasty in cytomegalovirus(CMV)positive patients.METHODS:This was a retrospective cohort study.We analyzed the clinical data of patients who underwent viral DNA detection in aqueous humor/corneal tissue collected during keratoplasty from March 2015 to December 2018 at the Peking University Third Hospital,Beijing,China.To further evaluate the effect of CMV on graft survival rate and ECD loss,patients were divided into three groups:1)CMV DNA positive(CMV+)group;2)viral DNA negative(virus-)group,comprising virus-group eyes pairwise matched to eyes in the CMV+group according to ocular comorbidities;3)control group,comprising virus-group eyes without ocular comorbidities.The follow-up indicators including graft survival rate,ECD,ECD loss,and central corneal thickness(CCT),were analyzed by Tukey honestly significant difference(HSD)test.RESULTS:Each group included 29 cases.The graft survival rate in CMV+group were lowest among the three groups(P=0.000).No significant difference in donor graft ECD was found among three groups(P=0.54).ECD in the CMV+group was lower than the virus-group at 12(P=0.009),and 24mo(P=0.002)after keratoplasties.Furthermore,ECD loss was higher in the CMV+group than in the virus-group in the middle stage(6-12mo)postkeratoplasty(P=0.017),and significantly higher in the early stage(0-6mo)in the virus-group than in the control group(P=0.000).CONCLUSION:CMV reduces the graft survival rate and exerts persistent detrimental effects on the ECD after keratoplasty.The graft ECD loss associate with CMV infection mainly occurrs in the middle stage(6-12mo postoperatively),while ocular comorbidities mainly affects ECD in the early stage(0-6mo postoperatively).

The precision and agreement of corneal thickness and keratometry measurements with SS-OCT versus Scheimpflug imaging

Purpose:To assess the repeatability and reproducibility of swept-source optical coherence tomography(SS-OCT)and Scheimpflug system and evaluate the agreement between the two systems in measuring multiple corneal regions in children.Methods:Pachymetric and keratometric maps for both systems were evaluated.Central,midperipheral and peripheral corneal thickness(CT),keratometry and astigmatism power vectors were recorded.The three outcomes yielded by the same observer were used to assess intraobserver repeatability.The differences in the mean values provided by each observer were used to evaluate interobserver reproducibility.Within-subject standard deviation,test-retest repeatability(TRT)and coefficient of variation(CoV)were used to analyze the intraobserver repeatability and interobserver reproducibility.Paired T-test and Bland-Altman were used to appraise interdevice agreement.Results:Seventy-eight eyes of 78 children were included.The CoV was≤2.12 and 1.10%,respectively,for repeatability and reproducibility.TRT and CoV were lower for central and paracentral CT measurements than for peripheral measurements.The SS-OCT device generated higher precision when acquiring CT data,whereas Scheimpflug system showed higher reliability when measuring corneal keratometry.Although the CT readings measured using SS-OCT were significantly thinner than Scheimpflug device(P<0.001),the central and thinnest CT values were still of high agreement.The interdevice agreement of keratometry measurement was high for the central corneal region and moderate for the paracentral and peripheral areas.Conclusions:The precision of CT measurements by SS-OCT was higher,while the reliability of keratometry measurements by the Scheimpflug system was higher in children.Apart from the measured values in the central corneal region,the thickness and keratometry readings should not be considered interchangeable between the two systems.

The precision and agreement of corneal thickness and keratometry measurements with SS-OCT versus Scheimpflug imaging

Purpose:To assess the repeatability and reproducibility of swept-source optical coherence tomography(SS-OCT)and Scheimpflug system and evaluate the agreement between the two systems in measuring multiple corneal regions in children.Methods:Pachymetric and keratometric maps for both systems were evaluated.Central,midperipheral and peripheral corneal thickness(CT),keratometry and astigmatism power vectors were recorded.The three outcomes yielded by the same observer were used to assess intraobserver repeatability.The differences in the mean values provided by each observer were used to evaluate interobserver reproducibility.Within-subject standard deviation,test-retest repeatability(TRT)and coefficient of variation(CoV)were used to analyze the intraobserver repeatability and interobserver reproducibility.Paired T-test and Bland-Altman were used to appraise interdevice agreement.Results:Seventy-eight eyes of 78 children were included.The CoV was≤2.12 and 1.10%,respectively,for repeatability and reproducibility.TRT and CoV were lower for central and paracentral CT measurements than for peripheral measurements.The SS-OCT device generated higher precision when acquiring CT data,whereas Scheimpflug system showed higher reliability when measuring corneal keratometry.Although the CT readings measured using SS-OCT were significantly thinner than Scheimpflug device(P<0.001),the central and thinnest CT values were still of high agreement.The interdevice agreement of keratometry measurement was high for the central corneal region and moderate for the paracentral and peripheral areas.Conclusions:The precision of CT measurements by SS-OCT was higher,while the reliability of keratometry measurements by the Scheimpflug system was higher in children.Apart from the measured values in the central corneal region,the thickness and keratometry readings should not be considered interchangeable between the two systems.

Comparison of Goldmann applanation tonometry,rebound tonometry and dynamic contour tonometry in normal and glaucomatous eyes

AIM: To compare the intraocular pressure(IOP)measurements obtained with the rebound tonometry(RT), dynamic contour tonometry(DCT) and Goldmann applanation tonometry(GAT) in normal and glaucomatous eyes and investigate the effects of central corneal thickness(CCT) and corneal curvature(CC) on IOP measurements.METHODS: One hundred and twenty-four eyes of 124 subjects were enrolled in this cross-sectional study.Fifty-six of participants were healthy individuals and 68 of them were glaucomatous patients. IOP was measured on each subject always in the same order, ICare RT-Pascal DCT-GAT, after a minimum interval of 10 min between measurements. CCT and CC were measured using a rotating Scheimpflug camera before the IOP measurements in all subjects. One way repeated measures ANOVA, Pearson correlation coefficient and regression analysis, and Bland-Altman analysis was used for the statistical assessment.RESULTS: Mean IOP for all enrolled eyes was 16.00±3.80 mm Hg for GAT, 16.99 ±4.91 mm Hg for RT, and20.40 ±4.44 mm Hg for DCT. Mean differences between GAT and RT was-1.75±3.41 mm Hg in normal(P <0.001)and-0.37 ±3.00 mm Hg in glaucomatous eyes(P =0.563).Mean differences between GAT and DCT was-4.06 ±3.42 mm Hg in normal(P < 0.001) and-4.67 ±3.12 mm Hg in glaucomatous eyes(P <0.001). GAT and RT were significantly positive correlated with CCT in normal(r2=0.101, P =0.017 and r2=0.331, P <0.001, respectively) and glaucomatous eyes(r2=0.084, P =0.016 and r2=0.123,P =0.003, respectively). DCT was also significantly positive correlated with CCT in normal eyes( r2=0.179,P =0.001) but not in glaucomatous eyes(r2=0.029, P =0.165).All tonometers were unaffected by CC.CONCLUSION: IOP measurements by RT and DCT were significantly higher than GAT. DCT has highest IOP measurements among these tonometers. RT was most influenced tonometer from CCT although all tonometers were significantly positive correlated with CCT except DCT in glaucomatous eyes. CC did not influence IOP measurements.

Comparison of postoperative anterior segment changes associated with pars plana vitrectomy with and without vitreous base shaving

AIM:To compare changes in anterior segment topography and axial length(AL)evaluated with Pentacam and IOL Master after pars plana vitrectomy(PPV)performed with and without vitreous base shaving.METHODS:This prospective study included patients who underwent PPV or phacoemulsification+PPV(Phaco+PPV)for various indications.Patients who underwent total posterior hyaloid detachment and excessive vitreous base shaving with scleral indentation were referred to as complete PPV(c-PPV).The patients whom posterior hyaloid was separated as far as the posterior arcades and vitreous base shaving with scleral depression was not performed were classified as the partial PPV(p-PPV)group.All patients underwent detailed ophthalmologic examinations preoperatively and lwk,I,and 3mo postoperatively.Changes in the anterior chamber depth(ACD),anterior chamber volume(ACV),iridocorneal angle(ICA)f central corneal thickness(Cd),and keratometric measurements(K1 and K2)were evaluated with Pentacam HR.Changes in the AL measurements were analyzed with IOL Master.RESULTS:A significant increase in ACD was observed in c-PPV cases(P=0.02),but this increase was not significant in the p-PPV group(P=0.053).In contrast,ICA increased significantly in the c-PPV group(P=0.02)but decreased in the p-PPV group(P=0.09).BCVA was significantly improved in the c-PPV group from week 1(P<0.001)while the increase in the p-PPV group reached significance at 3mo(P=0.035).Cd increased in the first week and later returned to baseline in both groups.No significant differences in the other parameters were observed between the groups,and there were no significant changes in intraocular pressure,ACV,AL,K1 or K2 values(P>0.05 for all).CONCLUSION:Incomplete posterior hyaloid excision and not removing the vitreous base in PPV surgeries may create a more stable anterior chamber,thus preventing the downward movement of the lens-iris diaphragm,and may cause ciliary body retraction,thereby reducing ICA.Awareness of these effects can provide some amount of guidance to physicians in selecting the appropriate PPV procedure and preempting surgical complications.