Biomechanics in DALK: Big bubble vs manual lamellar dissection / Biomecânica no DALK: grande bolha versus dissecção manual lamelar

ABSTRACT Purpose: The present study's aim was to compare the biomechanical properties of corneal tissue in patients who underwent deep anterior lamellar keratoplasty (DALK) surgery, with successful big bubble formation and manual lamellar dissection, during failed big bubble formation. Methods: This retrospective comparative study included 60 eyes from 60 keratoconus patients who previously underwent DALK surgery. These patients were categorized as big bubble (+) or big bubble (−) based on the success or failure of big bubble formation during the surgery. The big bubble (+) group included 42 eyes, while the big bubble (−) group had 18 eyes. Moreover, the patients were regrouped as 0.25 mm and 0.50 mm to evaluate the effects of the disparity between donor and trephine punches on the biomechanical properties of the cornea. These biomechanical properties, characterized by corneal hysteresis and the corneal resistance factor, were measured using the Ocular Response Analyzer 12 months after the surgery. Results: There was no statistically significant difference between the big bubble (+) and big bubble (−) groups in the biomechanical properties of the cornea (corneal hysteresis: 10.06, 10.25; p=0.716/corneal resistance factor: 10.15, 10.07; p=0.805, respectively). In addition, pachymetry results were not statistically different between the two groups. Multivariate regression analysis revealed that corneal hysteresis and corneal resistance factor were positively associated with central corneal thickness (p<0.001/r2=0.506; p<0.001/r2=0.561, respectively). However, the study did not demonstrate a relationship between any of the punch sizes and corneal hysteresis or between the punch sizes (p=0.673) and the corneal resistance factor (p=0.643). Conclusions: The corneal hysteresis and corneal resistance factor values were similar in big bubble and manual lamellar dissection after DALK. Thus, manual lamellar dissection was not a disadvantage considering the cornea's biomechanical properties.

RESUMO Objetivo: O objetivo do estudo foi comparar pa râmetros biomecânicos corneanos de pacientes com cirurgia de ceratoplastia lamelar anterior profunda com formação bem-sucedida de bolha e dissecção lamelar manual, frente à falha de formação da grande bolha. Métodos: Este estudo comparativo retrospectivo incluiu 60 olhos de 60 pacientes com ceratocone submetidos à cirurgia de ceratoplastia lamelar anterior profunda. Os pacientes foram agrupados como grande bolha (+) e grande bolha (-) de acordo com o sucesso da formação da grande bolha durante a cirurgia. O grupo grande bolha (+) incluiu 42 olhos, enquanto o grupo grande bolha (-) tinha 18 olhos. Além disso, para a avaliação dos efeitos da disparidade entre alterações individuais nas propriedades biomecânicas da córnea, reagrupamos os pacientes em 0,25 mm e 0,50 mm. Parâmetros biomecânicos da córnea, caracterizados por histerese corneana e fator de resistência corneana foram medidos com o ORA 12 meses após a cirurgia. Resultados: Não houve diferença estatisticamente significativa entre os grupos grande bolha (+) e grande bolha (-) em relação aos parâmetros biomecânicos da córnea (histerese corneana: 10,06, 10,25, p=0,716/fator de resistência da córnea: 10,15, 10,07, p=0,805, respectivamente). Além disso, os resultados de paquimetria não diferiram estatisticamente entre os dois grupos. A análise de regressão multivariada demonstrou que a histerese da córnea e o fator de resistência corneana estavam associados positivamente com a espessura corneana central (p<0,001/r2=0,506, p<0,001/r2=0,561 respectivamente). No entanto, o estudo não revelou associação entre qualquer um dos tamanhos de punção e histerese corneana, bem como entre os tamanhos de punção e o fator de resistência corneano (p=0,673, p=0,643). Conclusões: A histerese da córnea e os valores do fator de resistência da córnea foram comparáveis com formação de grande bolha e dissecção manual lamelar na ceratoplastia lamelar anterior profunda. Assim, a dissecção manual lamelar não foi uma desvantagem, considerando os fatores biomecânicos da córnea.

Effect of accelerated corneal crosslinking on ocular response analyzer waveform-derived parameters in progressive keratoconus / Efeito do crosslimking corneano acelerado nos parâmetros derivados da forma de onda do analisador de resposta ocular no ceratocone progressivo

ABSTRACT Purpose: To evaluate the effect of accelerated corneal crosslinking on corneal biomechanics with an ocular response analyzer in patients with progressive keratoconus. Methods: In this retrospective study, 50 eyes of 45 patients with progressive keratoconus who underwent accelerated corneal crosslinking were evaluated with ocular response analyzer waveform parameters before and one year after corneal crosslinking. Paired two-tailed Student's t-test was performed to compare the parameters before vs. after corneal crosslinking. Results: Mean patient age was 17.6 ± 3.6 (range 9-25) years. A significant increase was observed in p1 area, p2 area, h2, and dive2 values. No significant difference in corneal hysteresis, corneal resistance factor, or other waveform-derived parameters was observed at one year postoperatively. Conclusion: For estimating the effect of accelerated corneal crosslinking on corneal biomechanics, parameters such as p1 area, p2 area, h2, and dive2 are more sensitive than corneal hysteresis and corneal resistance factor. These results may help us to find out which corneal crosslinking method is most effective for stiffening the cornea.

RESUMO Objetivo: Avaliar o efeito do cross-linking corneano acelerado na biomecânica corneana com analisador de resposta ocular em pacientes com ceratocone progressivo. Métodos: Neste estudo retrospectivo, 50 olhos de 45 pacientes com ceratocone progressivo submetidos à cross-linking corneano acelerado foram avaliados com os parâmetros da forma de onda do analisador de resposta ocular antes e um ano após o tratamento com cross-linking corneano. O teste t de Student pareado bicaudal foi realizado para comparar os parâmetros antes e depois do cross-linking corneano. Resultados: A média de idade dos pacientes foi de 17,6 ± 3,6 (variação de 9 a 25) anos. Um aumento significativo foi observado nos valores de p1area, p2area, h2 e dive2. Nenhuma diferença significativa foi encontrada na histerese da córnea, fator de resistência da córnea ou outros parâmetros derivados da forma de onda foi observada em um ano de pós-operatório. Conclusão: Para estimar o efeito do cross-linking corneano acelerado na biomecânica corneana, parâmentros como p1area, p2area, h2 e dive2 são mais sensíveis que histerese da córnea e fator de resistência corneana. Esses resultados podem nos ajudar a descobrir qual método cross-linking corneano é mais eficaz no enrijecimento da córnea.

Corneal properties and glaucoma: a review of the literature and meta-analysis / Propriedades da córnea e glaucoma: revisão da literatura e meta-análise

ABSTRACT Purpose: Studies have suggested that corneal biomechanical properties influence intraocular pressure (IOP) measurements, namely central corneal thickness (CCT) and corneal hysteresis (CH). The present study aimed to investigate the associations of CH and CCT with glaucoma development. Methods: We performed a review of the literature and meta-analysis of observational studies (2006-2016) that included both adult glaucoma patients and controls and reported CCT and CH as outcomes. Nineteen studies were conside red eligible, and the mean difference (MD) between groups (patient and control) for both variables was used for statistical analyses. Results: A total of 1,213 glaucoma and 1,055 healthy eyes were studied. Quan titative analysis suggested that CH was significantly lower in the glaucoma group than in the control group (MD=-1.54 mmHg, 95% CI [-1.68, -1.41], P<0.0001). Additionally, CCT was significantly lower in the glaucoma group than in the control group (MD=-8.49 µm, 95% CI [-11.36, -5.62], P<0.001). Conclusion: Corneal properties appear to differ between glaucoma patients and healthy controls. Our results emphasize the importance of corneal biomechanical properties in IOP interpretation and should support further studies on the influence of CH and CCT in glaucoma screening and diagnosis.

RESUMO Objetivo: A literatura sugere que as propriedades biomecânicas da córnea, nomeadamente a espessura central da córnea (ECC) e a histerese corneana (HC), influenciam a medição da pressão intraocular (PIO). Este estudo teve como objetivo investigar a associação entre a ECC e a HC e o desenvolvimento de glaucoma. Métodos: Revisão da literatura e meta-análise. Foram incluídos estudos observacionais, publicados entre 2006 e 2016, que integrassem um grupo controle e um grupo de pacientes com glaucoma em que estes dois grupos apresentassem, igualmente, a ECC e a HC como parâmetros. Dezenove estudos foram considerados elegíveis e a diferença média (MD) daqueles parâmetros nos dois grupos foi utilizada para análise estatística. Resultados: Estudaram-se um total de 1.213 olhos com glaucoma e 1.055 olhos saudáveis. A análise quantitativa revelou que a HC é significativamente mais baixa no grupo de doentes com glaucoma quando comparada com o grupo controle (MD=-1,54 mmHg, intervalo de confiança de 95% [-1,68-1,41], P<0,00001). A ECC foi, também, significativamente mais baixa no grupo glaucoma quando comparada com os indivíduos saudáveis MD=-8,49 µm, intervalo de confiança de 95% [-11,36, -5,62], P<0,001). Conclusão: Os pacientes com glaucoma parecem possuir propriedades corneanas diferentes das que apresentam os indivíduos saudáveis. Os resultados enfatizam a importância das propriedades biomecânicas da córnea na interpretação da PIO e devem contribuir para novos estudos sobre a influência da HC e da ECC no rastreio e diagnóstico do glaucoma.

Effect of corneal biomechanical properties on surgically-induced astigmatism and higher-order aberrations after cataract surgery / Efeito das propriedades biomecânicas da córnea no astigmatismo induzido cirurgicamente e nas aberrações de alta ordem após a cirurgia de catarata

ABSTRACT Purpose: To investigate the relationship between biomechanical properties of the cornea and postoperative refractive changes in patients with low-level astigmatism after cataract surgery. Methods: This prospective study recruited patients undergoing cataract surgery involving 2.8-mm superior incisions. Biomechanical properties of the cornea were evaluated preoperatively using the Ocular Response Analyzer, and corneal profiles were evaluated using a Scheimpflug system (Pentacam HR). Topographic astigmatism, total corneal aberrations (TCA) and higher-order corneal aberrations (HOCA) analyses were performed preoperatively and during 1- and 3-month postoperative exams. The incidences of surgically-induced astigmatism (SIA) and HOCAs were calculated using vector analyses. Associations of the preoperative biomechanical properties of the cornea with SIA and HOCAs were evaluated. Results: This study included 28 eyes of 28 patients. The preoperative corneal hysteresis (CH) was 8.68 ± 1.86 mmHg, and the corneal resistance factor (CRF) was 8.66 ± 1.61 mmHg. At the 1-month postoperative evaluation, significant changes were observed in HOCAs (p=0.023), TCAs (p=0.05), astigmatism (p=0.02), and trefoil (p=0.033); in contrast, differences in coma (p=0.386) and spherical aberration (SA) were not significant (p=0.947). At the 3-month visit, significant changes were only observed in TCAs (p=0.02) and HOCAs (p=0.012). No relationships between the preoperative corneal hysteresis and corneal resistance factor and postoperative SIA and HOCA were identified, other than a positive correlation between the 3-month postoperative incidence of corneal hysteresis and spherical aberration. Conclusions: Despite the observed lack of relationships of preoperative biomechanical properties of the cornea with SIA and postoperative aberrations (except for SA), further studies involving larger patient groups are needed to explore the unexpected refractive deviations after cataract surgery.

RESUMO Objetivo: Investigar a relação entre as propriedades biomecânicas da córnea e as mudanças refrativas pós-operatórias em pacientes com baixa astigmatismo após a cirurgia de catarata. Método: Neste estudo prospectivo, recrutamos os pacientes submetidos a cirurgia de catarata com incisões superiores de 2,8 mm. As propriedades biomecânicas da córnea foram avaliadas no pré-operatório pelo Ocular Response Analyzer (ORA, Reichert, EUA) e o perfil corneano foi avaliado por um sistema Scheimpflug (Pentacam HR, Oculus Optikgeräte, GmbH). As avaliações do astigmatismo topográfico e das aberrações corneanas de alta ordem (HOCA) foram feitas no pré-operatório e no 1º e 3º mês pós-operatório. O astigmatismo induzido cirurgicamente (SIA) e aberrações corneanas de alta ordem foram calculados pela análise vetorial. Associações das propriedades biomecânicas da córnea no pré-operatório com astigmatismo induzido cirurgicamente e aberrações corneanas de alta ordem foram avaliadas. Resultados: O estudo foi realizado em 28 olhos de 28 pacientes. A histerese corneana (CH) pré-operatória foi 8,68 ± 1,86 mmHg, e o fator de resistência da córnea (CRF) foi de 8,66 ± 1,61 mmHg. No pós-operatório de 1 mês houve mudanças significativas aberrações corneanas de alta ordem (p=0,023), aberração total (p=0,05), astigmatismo (p=0,02) e trifóglio (p=0,033), mas as diferenças em coma (p=0,386) e aberração esférica (SA) foram insignificantes (p=0,947). No terceiro mês, a única mudança significativa foi em RMS total (p=0,02) e aberração total (p=0,012). Não houve relação entre histerese corneana e o fator de resistência da córnea pré-operatórios e astigmatismo induzido cirurgicamente e aberrações corneanas de alta ordem pós-operatórios, além de uma correlação positiva entre o histerese corneana e o aberração esférica do 3º mês pós-operatório. Conclusões: Apesar de não haver relação entre as propriedades biomecânicas pré-operatórias da córnea e astigmatismo induzido cirurgicamente e aberrações (exceto SA) após a cirurgia em nosso estudo, são necessários mais estudos com grupos de pacientes maiores de explicar os erros refrativos inesperados após a cirurgia de catarata.

Excimer laser phototherapeutic keratectomy in conjunction with mitomycin C in corneal macular and granular dystrophies / Ceratectomia fototerapêutica com excimer laser em conjunto com mitomicina C em distrofias granular e macular da córnea

ABSTRACT Purpose: To evaluate the visual outcomes, recurrence patterns, safety, and efficacy of excimer laser phototherapeutic keratectomy (PTK) in conjunction with mitomycin C (MMC) for corneal macular and granular diystrophies. Methods: The patients were divided into two groups. Group 1 included patients with macular corneal dystrophy (MCD) that caused superficial corneal plaque opacities, and Group 2 included patients with granular corneal dystrophy (GCD). Patients in both groups were pre-, peri-, and postoperatively evaluated. The groups were compared in terms of uncorrected visual acuity (VA), best spectacle-corrected VA, presence of mild or significant recurrence, and time of recurrence. Results: Eighteen eyes (nine with MCD and nine with GCD) of 18 patients (10 men and eight women) were included. PTK was performed for each eye that was included in this study. The mean ablation amount was 117.8 ± 24.4 µm and 83.5 ± 45.7 µm in MCD and GCD, respectively, (p=0.18). The postoperative improvement of the mean VA was similar between the two groups before recurrences (p>0.43) and after recurrences (p>0.71). There were no statistically significant differences in the recurrence rate and the recurrence-free period for any recurrence type. Conclusion: PTK was an effective, safe, and minimally invasive procedure for patients with MCD and GCD. PTK in conjunction with MMC was similarly effective for both groups in terms of recurrence and visual outcomes.

RESUMO Objetivo: Avaliar os resultados visuais, padrões de recorrência, segurança e eficácia da ceratectomia fototerapêutica (PTK) por excimer laser em conjunto com mitomicina C (MMC) em distrofias macular e granular da córnea. Métodos: Os pacientes foram divididos em dois grupos. Grupo 1 incluiu pacientes com distrofia macular de córnea (MCD) que causaram opacidades superficiais corneanas em placa e o grupo 2 incluiu pacientes com distrofia corneana granular (GCD). Todos os pacientes em ambos os grupos foram avaliados no pré, per e pós-operatório. Os grupos foram comparados em termos de acuidade visual (VA) não corrigida, VA melhor corrigida por óculos, presença de recorrência leve ou significativa e o tempo de recorrência. Resultados: Dezoito olhos de 18 pacientes (10 homens e 8 mulheres) foram incluídos no estudo, 9 olhos com MCD e 9 olhos com GCD. Um procedimento de PTK foi realizado em cada olho incluídos neste estudo. A quantidade média de ablação foi 117,8 ± 24,4, 83,5 ± 45,7 µm de MCD e GCD, respectivamente, (p=0,18). A melhora pós-operatória da acuidade visual média foi semelhante entre os dois grupos antes de as recidivas (p>0,43) e após as recidivas (p>0,71). Não houve diferença estatisticamente significativa na taxa de recorrência ou do período livre de recorrência para qualquer tipo de recorrência. Conclusão: PTK foi um procedimento eficaz, seguro e minimamente invasivo para pacientes MCD e GCD. PTK em conjunto com MMC é igualmente eficaz para ambos os grupos em termos de recorrência e resultados visuais.

Change in corneal biomechanical properties and influence factors in population with myopia / 中华实验眼科杂志

Background Corneal refractive surgery has significant effects on corneal biomechanical properties.However,there are few study on large scale population with corneal biomechanical properties in the myopic population before corneal refractive surgery.Objective This study was to evaluate the change of corneal biomechanical properties and influence factors in myopic eyes using ocular response analyzer (ORA).Methods A prospective cohort study was carried out in Beijing Tongren Eye Center from April 2010 to January 2011.Corneal hysteresis (CH) and corneal resistance factor (CRF) were detected using ORA in 1 792 eyes of 896 myopic subjects who were going to receive corneal refractive surgery under the informed consent.According to different spherical equivalent (SE) the eyes were grouped into-0.25-＜-3.0 D group,-3.0-＜-6.0 D group,-6.0-＜-9.0 D group,-9.0-＜-12.0 D group,-12.0-＜-15.0 D group and ≥-15.0 D group and according to different central corneal thickness (CCT),the eyes were grouped into ＜500 μm group,500-＜550 μm group,550-＜600 μm group and≥600 μm group.The CH value and CRF value in different SE groups or different CCT groups were compared,and the factors influencing CH and CRF were analyzed by Pearson correlation analysis.Results The mean CH and CRF value were (9.84±1.52)mmHg (1 mmHg =0.133 kPa) and (10.46±1.71) mmHg,respectively in the myopic eyes.The CH values were (10.35±1.53),(10.07±1.55),(9.81±1.46),(9.71±1.59),(9.35±1.55) and (9.23±1.28) mmHg in the-0.25-＜-3.0 D group,-3.0-＜-6.0 D group,-6.0-＜-9.0 D group,-9.0-＜-12.0 D group,-12.0-＜-15.0 D group and ≥-15.0 D group,respectively,showing a significant difference among the groups (F=20.69,P＜0.01),and the CH values in the-6.0-＜-9.0 D group,-9.0-＜-12.0 D group,-12.0-＜-15.0 D group and ≥-15.0 D group were significantly lower than those in the-6.0-＜-9.0 D group,-9.0-＜-12.0 D group (all at P＜0.01).There was no significant difference in the CRF values among different SE groups (F =0.65,P =0.49).CH and CRF values were increasing with the raise of CCT,with evidently differences among the CCT＜500 μm group,500 μm ≤ CCT＜550 μm group,550 μm≤ CCT＜600 μm group and CCT≥ 600 μm group (CH:F=110.99,P＜0.01;CRF:F =84.35,P＜0.01),and the CH and CRF values were significantly higher in the 550 μm ≤ CCT＜600 μm group and CCT ≥600 μm group than those in the CCT＜500 μm group (all at P＜0.01).CH showed a positive correlation with SE (r =0.24,P＜0.01),and no significant correlation between CRF and SE (r =0.03,P =0.20).The CH and CRF showed the positive correlations with the CCT (r=0.42,0.57,both at P＜0.01).In addition,CH and CRF values increased as the increases of SE,corneal curvature (CC) and CCT values,with the regression equation of CH =-7.87+0.08SE+0.16CC+0.02CCT (R2=0.26,P＜0.01) and CRF=-11.42+0.14CC+0.03CCT (R2=0.34,P＜0.01),respectively.The CH and CRF did not change with the age and gender in the subjects.Conclusions Corneal biomechanical properties including CH and CRF were positively correlated with CCT,CC and SE.

Correlations between the deformation parameters measured by Corvis ST and corneal morphology parameters in myopic patients / 中华实验眼科杂志

Background The novel dynamic biomechanical device Corvis ST can measure a variety of corneal deformation parameters and record the dynamic process of cornea deformation.Understanding various corneal deformation parameters is of important clinical significance for morphological and functional prediction for myopic eyes in corneal refractive surgery.However,the range and meaning of corneal deformation parameters in myopic eyes are still unknown.Objective This study was to establish the range of corneal defamation parameters by Corvis ST and explore its clinical significance in myopic eyes.Methods A descriptive study was designed under the approval of Ethic Committee of Tianjin Eye Hospital and informed consent of patients.This study protocol complied with Helsinki Declaration.Four hundred and seventy-seven eyes of 257 myopic patients who were going to receive corneal refractive surgery were included in Tianjin Eye Hospital from June 2014 to January 2015.The corneal deformation parameters including the first applanation time (1st A-time),first applanation lengh (1 st A-length),first applanation velocity (1 st A-velocity),second applanation time (2nd A-time),second applanation length (2nd A-length),second applanation velocity (2nd A-velocity),highest concavity time (HC-time),highest concavity deformation amplitude (HC-DA),highest concavity peak distance (HC-PD),highest concavity radius (HC-R),non-contact intraocular pressure (IOPnct) and the central corneal thickness (CCTst) were measured by Corvis ST.Corneal structural parameters including CCT and corneal curvature were measured by 3-D anterior segment analysis system (Pentacam),and corneal biomechanical parameters including corneal resistance factor (CRF),corneal hysteresis (CH),intraocular pressure mimic Goldmann (IOPg) and intraocular pressure of corneal compensation (IOPcc) were measured by Ocular Response Analyzer (ORA).The distributions of the data were tested with the Shapiro-Wilk test and 95％ confidence intervals (CI) were calculated.The correlations of the variables were evaluated by Pearson correlation coefficient and Spearman rank correlation coefficient.Multiple linear regression was used to analyze the changes of 1st A-time,2nd A-time and HC-DA with corneal morphology and biomechanical parameters.Resnlts Only 1st A-time,2ndA-time,HC-time,HC-DA,CCTst and IOPnct showed the normality distribution in corneal deformation parameters.The positive correlations were found between 1st A-time,1st A-length,2nd A-length,2nd A-velocity,HC-R with CCT (r=0.338,rs=0.129,rs=0.282,rs =0.374,r=0.306,all at P＜0.01),while 1st A-velocity,2nd A-time,HC-D and HC-PD showed the negative correlations with CCT (rs =-0.235,r=-0.130,r=-0.259,r=-0.226,all at P＜0.01).CRF and CH showed positive correlations with 1st A-time,2nd A-length,2nd A-velocity,HC-time,HC-R and negative correlations with HC-PD,△A-length (all at P＜0.05).1st A-time,2nd A-time and HC-DA changed with CRF and IOPcc with the regression formations of 1st A-time =6.185+0.066CRF+0.034IOPec (F=300.123,P =0.000),2nd A-time=23.397-0.074IOPec-0.044CRF (F=227.979,P=0.000) and HC-DA =1.523-0.017IOPcc-0.017CRF (F=152.662,P=0.000).The CCTst,IOPst and IOPnct values by Corvis ST were significantly lower than CCT by Pentacam ([548.23±26.31] μm,IOPg ([15.02±2.72]mmHg and ([16.02-±2.56]mmHg) by ORA respectively (t =11.00,2.919,6.815,all at P ＜ 0.01).Conclusions The corneal deformation parameters by Corvis ST can quantitatively describe corneal biomechanical properties in myopic eyes.Both IOP and the corneal steep curvature of the 3 mm center area (K2) affect the deformation response of cornea.The reliability of Corvis ST in the measurement of CCT and IOP remains to be further studied.

Characteristics of the cornea in patients with pseudoexfoliation syndrome / Características da córnea em pacientes com síndrome de pseudoexfoliação

ABSTRACT Purpose: To quantify the morphological alterations in corneal nerve fibers and cells in patients with pseudoexfoliation syndrome (PEX) and their relationship with the presence of hyperreflective endothelial deposits observed using in vivo confocal microscopy. Methods: One eye each of 37 patients with PEX and 20 age-matched healthy control subjects was evaluated by in vivo corneal confocal microscopy. Patients with PEX were further classified into two groups: those with and without hyperreflective endothelial deposits. We evaluated the densities of basal epithelial cells, anterior and posterior stromal keratocytes, and endothelial cells and structure of sub-basal nerve fibers. Results: The mean anterior and posterior stromal keratocyte and endothelial cell densities and corneal sub-basal nerve plexus variables were significantly lower in patients with PEX compared with those in healthy control subjects. The mean basal epithelial cell density did not significantly differ. Conclusion: Eyes with PEX presented decreased corneal sub-basal nerve plexus variables and cell densities in all corneas, except for the mean basal epithelial cell density. Further, a trend of lower corneal sub-basal nerve plexus measurements in patients with hyperreflective endothelial deposits compared with those without endothelial deposits was observed.

RESUMO Objetivo: Quantificar as alterações morfológicas nas fibras nervosas e nas células da córnea em pacientes com síndrome de pseudoexfoliação (PEX) e sua relação com a presença de depósitos endoteliais hiper-refletivos, observados por meio da microscopia confocal in vivo. Métodos: Trinta e sete olhos de 37 pacientes portadores de PEX e 20 olhos de 20 indivíduos saudáveis, pareados por idade, foram avaliados por meio da microscopia confocal de córnea. Os pacientes com PEX foram classificados em dois grupos: pacientes sem depósitos endoteliais hiper-refletivos e pacientes com depósitos endoteliais hiper-refletivos. Células basais epiteliais, ceratócitos do estroma anterior e posterior, e densidades celulares endoteliais assim como a estrutura das fibras nervosas sub-basais foram avaliadas. Resultados: A média de ceratócitos do estroma anterior e posterior, as densidades celulares endoteliais, bem como as variáveis de plexo nervo sub-basal foram significativamente menores nos pacientes com PEX em comparação com indivíduos saudáveis. A densidade celular epitelial basal não diferiu significativamente. Conclusões: Os olhos com PEX apresentaram diminuição das variáveis do plexo do nervo sub-basal e das densidades celulares em toda a córnea, exceto na camada basal das células epiteliais. Além disso, foi notada uma tendência para valores mais baixos nas variáveis do plexo do nervoso sub-basal em pacientes com depósitos endoteliais hiper-refletivos em comparação àqueles sem depósitos endoteliais.

Corneal strength change and keratocan expression of corneas during the healing of penetrating injury in rabbits / 中华实验眼科杂志

Background Corneal walleye formation is a result of excessive corneal wound healing.Controlling the corneal trauma or excessive healing reaction after operation of penetrating corneal trauma is a focus in the study of corneal wound healing.Objective This study was to investigate the changes of corneal strength and the expression of keratocan,a marker of corneal stroma,after corneal penetrating injury operation,and to determine the optimal removal time of corneal suture.Methods Full-thickness incisions of 5 mm along the vertical diameter were done at the central cornea on 80 eyes of 80 six-month-old New Zealand rabbits in this study.Then the incisions were interruptedly sutured with 10-0 nylon thread to establish the corneal wound healing models.Each 4 rabbits were sacrificed in 1 week,2,3,4,5,6,7,8 weeks after operation,respectively,and the central corneal stripes were prepared with the size of 7 mm×5 mm.The mean maximal strength of the corneal bands was measured by uniaxial tensile test with electroforce3220-AT biomachanics machine.Then,each 6 whole corneas were obtained at the above time points,and the dynamic changes of keratocan mRNA expression in the specimens were detected by reverse trancription PCR (RT-PCR).The care and use of the animals followed the rules of ARVO.Results The mean maximal strength of corneal stripes was 0,(1.007 ± 0.041),(1.991 ± 0.034),(2.512 ± 0.030),(3.630 ± 0.049) and (4.935 ± 0.004)M Pa in 1 week,2,3,4,5,6 weeks after modeling,and the corneal strength values from 3 weeks through 6 weeks were significantly enhanced in comparison with the value at the adjacent before timepoint (q =6.35,7.54,8.21,5.86,all at P＜0.01).The relative expression levels (absorbance) of keratocan mRNA in the corneas were 0.869±0.015,0.779 ± 0.065,0.621 ± 0.027,0.460 ± 0.018,0.393 ± 0.057 and 0.255 ± 0.045 in 1 week,2,3,4,5,6 weeks after operation,and each value was lower than that of the adjacent before timepoint (q =5.24,5.61,7.49,4.75,5.47,all at P＜0.01).The intensity of corneal stripes and the expression levels of keratocan mRNA in the corneas were stable in 7 weeks and 8 weeks after operation.Conclusions The dynamic change of corneal strength during the repair of penetrating corneal injury is associated with the down-regulation of keratocan in cornea.Rabbit cornea reaches a maximal strength capacity in 6 weeks after penetrating injury,therefore,it is the optimal time to remove suture.

Técnica para diagnosticar o ceratocone / Best waveform score for diagnosing keratoconus

PURPOSE: To test whether corneal hysteresis (CH) and corneal resistance factor (CRF) can discriminate between keratoconus and normal eyes and to evaluate whether the averages of two consecutive measurements perform differently from the one with the best waveform score (WS) for diagnosing keratoconus. METHODS: ORA measurements for one eye per individual were selected randomly from 53 normal patients and from 27 patients with keratoconus. Two groups were considered the average (CH-Avg, CRF-Avg) and best waveform score (CH-WS, CRF-WS) groups. The Mann–Whitney U-test was used to evaluate whether the variables had similar distributions in the Normal and Keratoconus groups. Receiver operating characteristics (ROC) curves were calculated for each parameter to assess the efficacy for diagnosing keratoconus and the same obtained for each variable were compared pairwise using the Hanley–McNeil test. RESULTS: The CH-Avg, CRF-Avg, CH-WS and CRF-WS differed significantly between the normal and keratoconus groups (p<0.001). The areas under the ROC curve (AUROC) for CH-Avg, CRF-Avg, CH-WS, and CRF-WS were 0.824, 0.873, 0.891, and 0.931, respectively. CH-WS and CRF-WS had significantly better AUROCs than CH-Avg and CRF-Avg, respectively (p=0.001 and 0.002). CONCLUSION: The analysis of the biomechanical properties of the cornea through the ORA method has proved to be an important aid in the diagnosis of keratoconus, regardless of the method used. The best waveform score (WS) measurements were superior to the average of consecutive ORA measurements for diagnosing keratoconus.

OBJETIVO: Testar se a histerese corneana (CH) e o fator de resistência corneano (CRF) podem discriminar olhos com ceratocone e avaliar se a média de duas medidas consecutivas apresenta desempenho diferente da medida única com a melhor waveform score para diagnósticar o ceratocone. MÉTODOS: Foram realizadas medidas do ORA de um olho por indivíduo, selecionados aleatoriamente a partir de 53 pacientes normais e de 27 pacientes com ceratocone. Dois grupos foram considerados: a média (CH-médio, o CRF-médio) e melhor waveform score (CH-WS, CRF-WS). O teste de Mann-Whitney U-teste foi utilizado para avaliar se as variáveis apresentaram distribuições semelhantes entre os grupos. As curvas (ROC) foram calculadas para cada parâmetro para avaliar eficácia no diagnóstico e as obtidas para cada variável foram comparadas usando o teste de Hanley-McNeil. RESULTADOS: CH-médio, CRF-médio, CH-WS e CRF-WS diferiram significativamente entre os grupos (p<0,001). Já as áreas sob a curva ROC para CH-médio, CRF-médio, CH-WS, e CRF-WS foram 0,824, 0,873, 0,891, 0,931, respectivamente. CH-WS e CRF-WS obtiveram AUROCs significativamente melhores do que CH-médio e CRF-médio (p=0,001 e 0,002). CONCLUSÃO: A análise das propriedades biomecânicas da córnea através do ORA demonstrou ser um método auxiliar importante no diagnóstico de ceratocone, independente do método utilizado. As melhores medidas waveform score foram superiores à média das medições consecutivas para o diagnóstico de ceratocone.