Research progress on the stress-strain index of Corvis ST / 国际眼科杂志(Guoji Yanke Zazhi)

Corneal visualization Scheimpflug technology(Corvis ST)is currently the most commonly used clinical device for assessing in vivo corneal biomechanics. The new parameter stress-strain index(SSI)has been a hot topic of clinical research in recent years, which not only directly reflect corneal biomaterial stiffness, but also closely correlates with the progression of certain diseases. SSI was generated based on the predictions of corneal behavior using finite element(FE)numerical modeling to simulate the effects of intraocular pressure and Corvis ST jets. The SSI algorithm does not change with central corneal thickness(CCT), intraocular pressure, or biomechanically corrected intraocular pressure(BIOP), but it is clearly associated with altered collagen fibres in the corneosclera. The principles of SSI, the relationship between age and SSI, the relationship between axial length and SSI, the relationship between myopia and SSI, and the application of SSI are summarized and concluded.

Evaluation of changes in anterior segment morphology using Sirius Scheimpflug-Placido disk topographer following laser peripheral iridotomy in primary angle-closure disease

Purpose: To assess the morphological changes in the anterior segment following laser peripheral iridotomy (LPI) in primary angle?closure disease (PACD) using Sirius Scheimpflug?Placido disk corneal topographer. Methods: This was a prospective observational study. A total of 52 eyes of 27 patients with PACD who underwent LPI were analyzed for iridocorneal angle (ICA), anterior chamber depth (ACD), anterior chamber volume (ACV), horizontal visible iris diameter (HVID), corneal volume (CV), central corneal thickness (CCT), and horizontal anterior chamber diameter (HACD) 1 week following LPI, using Sirius Scheimpflug?Placido disk corneal topographer. Data analysis was done using Statistical Package for the Social Sciences (SPSS) software version 19.0, and paired t?test was used to assess the statistical significance. Results: Laser peripheral iridotomy was performed in 43 eyes with primary angle?closure suspect (PACS), six eyes with primary angle closure (PAC), and three eyes with primary angle?closure glaucoma (PACG). The analysis of the data showed statistically significant changes in anterior segment parameters of ICA, ACD, and ACV. Post?laser increase in ICA from 34.13° ± 2.64° to 34.75° ± 2.84° (P < 0.041), mean ACD increase from 2.21 ± 0.25 to 2.35 ± 0.27 mm (P = 0.01), and mean ACV increase from 98.19 ± 12.13 to 104.15 ± 11.16 mm3 (P = 0.001) were noted. Conclusion: Significantly quantifiable short?term changes in the anterior chamber parameters of ICA, ACD, and AC volume were seen after LPI in patients with PACD on Sirius Scheimpflug?Placido disc corneal topographer.

Distribution of corneal densitometry in different grades of keratoconus

Purpose: To evaluate the use of Scheimpflug tomography in corneal densitometry (CD) in comparing the stages of keratoconic eyes. Methods: Keratoconic (KC) corneas (stages 1–3 classified according to the topographic parameters) were examined using the Scheimpflug tomographer (Pentacam, Oculus) using the CD software. CD was measured over three different depths (anterior stromal layer [120 ?m], posterior stromal layer [60 ?m], and middle stromal layer between these two layers), and concentric annular zones (0.0 to 2.0, 2.0 to 6.0, 6.0 to 10.0, and 10.0 to 12.0 mm diameter area). Results: The study participants were divided into three groups: keratoconus (KC) stage 1 (KC1) with 64 participants, keratoconus stage 2 (KC2) with 29 participants, and keratoconus stage 3 (KC3) with 36 participants. Comparing CD of all three layers (anterior, central, and posterior) of the cornea over different circular annuli (0–2, 2–6, 6–10, and 10–12 mm) revealed a significant difference in the 6–10 mm annulus between all groups and in all layers (P = 0.3, 0.2, and 0.2, respectively). Area under curve (AUC) was done. It revealed that the central layer showed the highest specificity (93.8%) in comparing KC1 and KC2, whereas CD in the anterior layer between KC2 and KC3 had the highest specificity (86.2%). Conclusion: CD showed increased values in the anterior corneal layer and in the annulus 6–10 mm more than other locations in all stages of KC

Repetibilidade do estudo tomográfico da córnea com Scheimpflug rotacional, em olhos normais, olhos com ceratocone e olhos com ceratocone operados por crosslinking / Repeatability of the tomographic study of the cornea with a rotational Scheimpflug in normal eyes, eyes with keratoconus and eyes with crosslinking for keratoconus

RESUMO Objetivo Avaliar a precisão da tomografia corneana com imagens de Scheimpflug (Pentacam® AXL, OCULUS, Wetzlar, Alemanha) nos padrões de escaneamento com 25 e 50 imagens, verificando sua repetibilidade e reprodutibilidade em olhos normais, com ceratocone e com ceratocone após crosslinking. Métodos Estudo prospectivo, transversal, misto, no qual foram incluídos os pacientes que tinham córneas normais, ou com ceratocone; e não tinham realizado cirurgias corneanas, com exceção do crosslinking. Foram excluídos os pacientes que tivessem realizado outras cirurgias, como implante de anel intracorneano ou transplante de córnea. Foram realizadas três medidas com 25 imagens e três medidas com 50 imagens em cada olho incluído no estudo. Resultados O estudo avaliou 54 olhos de 41 pacientes. Destes, dez (18,52%) olhos eram com córneas normais e sem cirurgia ocular prévia aleatoriamente selecionados de 5 pacientes; 22 (40,74%) olhos aleatoriamente selecionados de 18 pacientes com ceratocone, sem cirurgia ocular prévia; e 22 (40,74%) olhos com ceratocone de 18 pacientes operados por crosslinking. No estudo da repetibilidade, percebemos uma maior variação de valores em todos os índices nos pacientes com ceratocone comparados aos de pacientes com olhos normais, em grande parte dos parâmetros analisados. Conclusão Não houve diferença significativa entre os métodos de escaneamento por 25 e 50 imagens, sendo o escaneamento por 25 imagens mais conveniente. A presença de ceratocone teve impacto negativo na repetibilidade de ambos os tipos de exame, e foi grande a concordância entre os métodos nos três grupos estudados. O coeficiente de repetibilidade permite considerar a relevância clínica dos dados para avaliar a progressão de ceratocone.

ABSTRACT Objective To evaluate the accuracy of corneal tomography with Scheimpflug images (Pentacam® AXL, OCULUS, Wetzlar, Germany) in scanning patterns with 25 and 50 images, by analyzing their repeatability and reproducibility in normal eyes, eyes with keratoconus and with keratoconus after crosslinking. Methods Prospective, cross-sectional, mixed study including patients who had normal corneas, or who had keratoconus, who had not undergone corneal surgery, with the exception of crosslinking. Patients who had undergone surgery for intracorneal ring implantation or corneal transplantation were excluded. Three measurements were performed with 25 images and three measurements were performed with 50 images on each eye included in the study. Results The study evaluated a total of 54 eyes of 41 patients. Of these, 10 (18.52%) eyes had normal corneas, without previous eye surgery, 22 (40.74%) were eyes with keratoconus, without previous eye surgery, and 22 (40.74%) were eyes with keratoconus, with crosslinking for keratoconus. In the study of repeatability, we noticed a greater variation of values in all indices in patients with KC compared to those with normal eyes, in most of the parameters analyzed. Conclusion There is no significant difference between the scanning methods with 25 and 50 images. However, 25 scans has advantages that make it the main method suggested. The presence of keratoconus has a negative impact on the repeatability of both types of examination, and there is great agreement between the methods in the three groups studied. The high repeatability coefficient in some parameters suggests that these data should be used with care in the assessment of keratoconus progression.

Evaluation of corneal biomechanical parameters and related influencing factors in myopic patients by Corvis ST / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To assess the differences in corneal biomechanical parameters and their correlation with other ocular biometric parameters in myopic patients using a corneal visualisation scheimpflug technology(Corvis ST).METHODS: A total of 132 myopic patients who received treatment in the department of refractive surgery of Eyegood Ophthalmic Hospital from May to December 2021 were selected, and the data of right eye were taken. The subjects were classified into low and moderate myopia(-0.50 to -6.00D), high myopia(&#x003E;-6.00D to &#x003C;-8.00D), and super high myopia(≥-8.00D)according to the spherical equivalent(SE). The basic parameters of corneal biomechanical deformation measured with Corvis ST included the amount of corneal displacement at highest degree of concavity(DA), radius of curvature at highest concavity(HCR), and distance between the two peaks of the cornea at highest concavity(PD); stiffness parameters at applanation 1(SP-A1), integrated radius(IR), deformation amplitude ratio(DA ratio), Ambrosio relational thickness horizontal(ARTh), Corvis biomechanical index(CBI). Other ocular biometric parameters measured included SE, intraocular pressure(IOP), axial length(AL), central corneal thickness(CCT), white-to-white(WTW)and retinal nerve fiber layer(RNFL)thickness. The differences in corneal biomechanical parameters were compared among the three groups of myopic patients, and the correlation between corneal biomechanical parameters and other ocular biometric parameters and age was further analyzed.RESULTS: The SP-A1 in the low and moderate, high, and super high myopia groups were 106.8±16.2, 115.6±21.9, and 106.9±11.5, respectively. The SP-A1 in the high myopia group was higher than that in the low and moderate and severe myopia groups(all P&#x003C;0.05). All corneal biomechanics were significantly correlated with CCT(P&#x003C;0.01); all corneal biomechanics were correlated with IOP except ARTh(P&#x003C;0.05); AL was significantly and positively correlated with PD(r=0.270, P=0.002), weakly and positively correlated with HCR(r=0.177, P=0.043), and weakly and negatively correlated with IR(r=-0.183, P=0.036); WTW was positively correlated with PD, DA and DA ratio(r=0.363, P&#x003C;0.001; r=0.252, P=0.003; r=0.200, P=0.02); there was no correlation between corneal biomechanical parameters and age, SE, and RNFL.CONCLUSION: Corneal stiffness was higher in high myopia patients than in patients with low to moderate and super high myopia. IOP and CCT were both important factors affecting corneal biomechanics. Some of the biomechanical parameters also have certain correlation with AL and WTW. As the growth of axial length, the PD of corneal deformation and HCR were larger, and IR was smaller, but HCR and IR had little significance; the longer the WTW, the greater the corneal deformation amplitude. In clinical practice, attention should be paid to the corneal biomechanical parameters in patients with super high myopia.

Agreement study of anterior segment parameters measured by two kinds of ocular biometry based on imaging principle of Scheimpflug / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To compare the differences and agreement of anterior segment biometric parameters of myopic patients measured by domestic Scansys and the imported Sirius based on the principle of Scheimpflug imaging technique.METHODS: In this case series study, 103 cases(103 eyes)that underwent pre-refractive surgery(including small incision lenticule extraction, femtosecond laser-assisted in situ keratomileusis, transepithelial photorefractive keratectomy and implantable contact lens implantation)at Aier Excellent Eye Hospital from May 2022 to October 2022 were recruited. Preoperative keratometry(Km), central corneal thickness(CCT), anterior chamber depth(ACDEndo.), anterior chamber angle(ACA), anterior chamber volume(ACV), white to white(WTW)of patients were recorded.RESULTS: The results of Km, CCT, ACA, and WTW measured by Scansys and Sirius were 42.88(41.54, 44.60)and 42.98(41.56, 44.52)D,(541.52±29.08)and(549.55±29.62)μm, 42.70°±2.67° and 46.63°±5.13°, 12.10±0.60 and 11.98±0.47 mm, respectively, showing the difference was statistically significant(all P&#x003C;0.01). The ACV measured by Scansys and Sirius was 194.26±31.06 and 191.47±25.65 mm3, and ACDEndo. was 3.40(3.17, 3.57)and 3.43(3.19, 3.56)mm, with no statistically significant difference(all P&#x003E;0.05). The range of Km, CCT, ACA, ACDEndo., ACV and WTW values measured by the two instruments was small, with an average difference close to zero, and the points percentage of 95% limits of agreement(LoA)was &#x003C;5%, which is of good consistency.CONCLUSIONS: Scansys and Sirius have small differences and good agreement in the parameters, which can be replaced by each other in clinical practice. Scansys could theoretically be used to extrapolate the implantable contact lens model or could be a new option for anterior segment parameter measurements.

Changes in corneal biomechanics after small incision lenticule extraction and femtosecond laser-assisted laser in situ keratomileusis evaluated by corneal visualization Scheimpflug technology / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To evaluate the changes in corneal biomechanics of patients with moderate refractive error after receiving small-incision lenticule extraction(SMILE)and femtosecond laser-assisted laser in situ keratomileusis(FS-LASIK)using the corneal visualization Scheimpflug technology(Corvis ST).METHODS:Prospective cohort study. A total of 65 moderate myopia patients(65 eyes)who were scheduled to undergo refractive surgery at the Ophthalmic Refractive Surgery Center of the Ningxia Eye Hospital from November 2020 to November 2021 were included in the study, and there were 30 eyes in the SMILE group and 35 eyes in the FS-LASIK group. The changes in corneal biomechanical parameters, including integrated radius(IR), inverse concave radius(ICR), deformation amplitude ratio 2mm(DAR2), stiffness parameter at first applanation(SP-A1), ambrosio relational thickness(ARTh)and the central curvature radius at highest concavity(HC-Radius)were observed by Corvis ST between both groups preoperatively and 1 and 3mo postoperatively.RESULTS: There were no statistical significance in biomechanical parameters between two groups of patients 1 and 3mo postoperatively(P&#x0026;#x003E;0.05). IR, ICR and DAR2 of each groups of patients 1 and 3mo postoperatively were significantly increased than those preoperatively, and SP-A1, ARTh and HC-Radius were significantly decreased than those preoperatively(all P&#x0026;#x003C;0.05). The biomechanical parameters at 1mo and 3mo postoperatively showed no statistical significance(P&#x0026;#x003E;0.05). In addition, a positive correlation was found between central corneal thickness(CCT)and ARTh and SP-A1 of the two groups of patients at 3mo postoperatively(FS-LASIK group: r=0.727, 0.819, SMLIE group: r=0.683, 0.434, all P&#x0026;#x003C;0.05), while a negative correlation was found between CCT and IR and ICR at 3mo postoperatively.(FS-LASIK group: r=-0.697, -0.622, SMLIE group: r=-0.447, -0.491, all P&#x0026;#x003C;0.05).CONCLUSION:For patients with moderate myopia, both SMILE and FS-LASIK can reduce corneal biomechanical stability. Both surgeries showed no significant differences in the effect on biomechanical, and the biomechanical has been stabilized at 1mo postoperatively. A correlation was found between postoperative CCT and ARTh, SP-A1, IR and ICR.

Characteristics of new corneal biomechanical parameters in different degrees of myopia / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To study the characteristics of new corneal biomechanical parameters in different degrees of myopia and analyze the correlation of the new parameter stress-strain index(SSI).METHODS: A cross-sectional study was conducted on 366 adult patients(718 eyes)with different degrees of myopia who received treatment at the First Affiliated Hospital of Dali University from October 2021 to November 2021, aged 18-50 years, and the spherical equivalent(SE)was -0.50～-16.75D. The axial length(AL)of the eye was measured by IOL master, and the new corneal biomechanical parameters, central corneal thickness(CCT)and intraocular pressure(IOP)were measured by corneal visualization Scheimpflug technology(Corvis ST). The subjects were categorized into low myopia, moderate myopia and high myopia groups according to SE. The data were analyzed by ANOVA and Pearson correlation.RESULTS: The ratio of the thinnest corneal thickness to horizontal thickness change rate(ARTh)and SSI were statistically significant(P&#x0026;#x003C;0.001), while the remaining parameters were not statistically significant(P&#x0026;#x003E;0.05). SSI was positively correlated with age(r=0.102, P=0.006), SE(r=0.361, P&#x0026;#x003C;0.001), IOP(r=0.175, P&#x0026;#x003C;0.001), CCT(r=0.098, P=0.009), SPA1(r=0.182, P&#x0026;#x003C;0.001), negatively correlated with AL(r=-0.331, P&#x0026;#x003C;0.001), IR(r=-0.545, P&#x0026;#x003C;0.001)and had no correlation with other corneal biomechanical parameters(P&#x0026;#x003E;0.05).CONCLUSION: With the increase of myopia degree and the elongation of the axial length, the SSI value becomes smaller and the corneal hardness decreases. SSI may be a helpful corneal biomechanical indicator for future research on myopia.

Use of Scheimpflug Tomography and OCT Tomography to Examine Corneal Dimensional and Anterior Chamber Depth before and after LASIK Surgery

Aims: The aim of this study is to compare corneal parameters in: central corneal thickness (CCT), thinnest corneal thickness (TCT), mean radius of curvature (Rm) and anterior chamber depth (ACD) obtained from Pentacam Schiempflug and OCT Tomography imaging which are checked preoperatively and six months postoperatively after LASIK surgery.Methodology: Our sample consisted of 40 eyes. Changes in corneal dimensions were monitored before and after LASIK surgery using scheimpflug tomography (Pentacam HR) and optical coherence tomography (OCT). The parameters measured were CCT, TCT, Rm and the ACD. The results between the two techniques were compared with the Bland-Altman method.Results: During the analysis of the results, a statistically significant difference was observed between the two techniques in terms of the preoperative CCT as well as the TCT both preoperatively and postoperatively.Scheimpflug tomography gives higher values of the CCT than OCT, up to thickness 530nm, while above this it seems that OCT overestimates the thickness of the cornea. Scheimpflug tomography at the TCT seems to give higher values than OCT tomography, up to thickness 520 nm, while above that it seems that OCT tomography overestimates TCT. We have similar results postoperatively for TCT.The two techniques agree on the ACD and the Rm rating.Conclusion: How converging or different the two imaging devices are because it is important for both clinical practice and research may be a point of reference for starting a new research.

Corneal densitometry in patients with arcus senilis and its correlation with serum lipid levels

Purpose: To evaluate corneal densitometry (CD) of patients with arcus senilis (AS) and its association with the serum lipid markers. Methods: This is a cross?sectional, case?control study. The AS diagnosis was made clinically. Forty?five eyes of 45 patients with AS and 38 eyes of 38 age?matched control subjects with no noticeable AS were enrolled in the study. All participants underwent detailed ophthalmologic examination along with corneal Scheimpflug imaging with CD measurement. The evaluated serum lipid markers of the participants included total cholesterol, triglyceride, low?density lipoprotein (LDL), high?density lipoprotein (HDL), and very?low?density lipoprotein (VLDL). The Spearman correlation analysis was used to correlate the serum lipid values and the CD. P < 0.05 was defined as statistically significant. Results: The male to female ratio was 26/19 and 14/24 in the study and control groups, respectively (P = 0.057). The mean age was 59.56 ± 8.7 and 56.47 ± 8.6 years in the study and control groups, respectively (P = 0.117). The mean total CD values in the zones extending from 2 to 12 mm were higher in the study group than in the control group (P < 0.001). The serum HDL level was found to be significantly decreased in the study group compared to the control group (P = 0.048 and Z = ?1.976). There was a significant positive correlation between the serum triglyceride level and the CD value of the outermost zone (10–12 mm) (r = 0.334 and P = 0.025). Conclusion: The CD of patients with AS was found to increase not only in the peripheral zone but also in the cornea’s paracentral zone compared to the healthy controls. The serum triglyceride level should give an insight into the intensity of arcus senilis. The serum HDL levels were decreased in patients with AS

Cataratas en pacientes sometidos a implante de lente intraocular fáquico: una ocurrencia muy poco habitual / Cataract in patients undergoing phakic intraocular lens implantation: an uncommon event

Se presenta el caso de dos pacientes con vault anormalmente bajo luego del implante de lentes intraoculares fáquicos. Se reportan las imágenes de Scheimpflug y retroiluminación que han permitido el diagnóstico temprano.

We present the cases of two patients who developed an abnormally low vault and subcapsular anterior cataracts after phakic intraocular lens implantation. Scheimpflug and retroillumination images are reported

Correlation analysis between corneal biomechanical parameters and high-order aberrations in myopia children / 国际眼科杂志(Guoji Yanke Zazhi)

AIM:To investigate the correlation between corneal biomechanical parameters measured by the corneal visualization Scheimpflug Technology(Corvis ST)and corneal high-order aberrations(HOAs)in children with mild to moderate myopia.METHODS:A cross-sectional study. A total of 255 pediatric patients with myopia enrolled from April to July 2021 in Tianjin Medical University Eye Hospital were continuously collected, and all the right eyes were taken for analysis. Corneal biomechanical parameters were obtained from Corvis ST. Pentacam three-dimensional anterior segment analyzer was used to measure total corneal higher-order aberrations(RMSh), third order aberrations(RMS3)and fourth order aberrations(RMS4).RESULTS:RMS3 was positively correlated with the second applanation time(A2T)(r=0.175, P=0.009)and negatively correlated with the axis length(AL)(r=-0.155, P=0.014). RMS4 was negatively correlated with the highest concavity radius(HCR)(r=-0.165, P=0.009). RMSh was negatively correlated with HCR and AL(r=-0.152, P=0.037; r=-0.175, P=0.005).CONCLUSION:There is a correlation between corneal biomechanical parameters and HOAs in children with myopia. Cornea with higher stiffness and stronger deformation resistance has smaller RMS3, RMS4 and RMSh.

Distrofia polimorfa posterior vista por medio de tomografía Scheimpflug y retroiluminación / Posterior polymorphous corneal dystrophy as seen through Scheimpflug tomography and corneal retroilumination

Se presenta el caso de un paciente de género masculino de 31 años de edad, a quien se le diagnosticó distrofia polimorfa posterior, una entidad poco frecuente, secundaria a alteraciones a nivel de la cresta neural. Si bien la mayoría de los pacientes tiene afectación bilateral, no son raros los casos totalmente unilaterales, como el reportado en el presente artículo.

We present the case of a 31-year-old male patient, who was diagnosed with posterior polymorphic dystrophy, a rare hereditary condition of the neural crest-derived. Although most patients have bilateral involvement, totally unilateral cases, such as the one reported in this article, are not rare

Corneal biomechanical alterations after phacoemulsitication with 2.4mm corneal incision / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To investigate the corneal biomechanical parameters alteration after phacoemulsitication with 2.4mm corneal incision within 1mo by Corvist ST.<p>METHODS: A self control study was performed. Twenty-eight age related cataract patients(56 eyes), who were in accordance with the inclusion criteria, received phacoemulsification with 2.4mm corneal incision from March to September in 2019. Corneal biomechanical parameters were measured preoperatively and postoperatively on 3d, 6d and 30d by Corvis ST.<p>RESULTS: The first applanation length(A1L), the second applanation time(A2T)and corneal thickness(CCT)were significantly different between preoperation and postoperation(<i>F</i>=10.534, 11.655, 14.734; all <i>P</i><0.05). The value of A1L on 3d postoperative was significantly increased than that on the day before operation, 6d and 30d postoperative, while the A2T value was significantly reduced(<i>P</i><0.05). But there was no different in A2L and A2T between preoperation and 6d postoperative(<i>P</i>>0.05). The value of central corneal thickness(CCT)was significantly increased on 3d and 6d postoperative compared with the preoperative parameter(<i>P</i><0.05). The value of CCT got the maximum value on the 3d after surgery, and recovered to the preoperative level on the 30d after surgery. <p>CONCLUSION: Phacoemulsitication with 2.4mm corneal incision change the corneal biomechanical preoperties. The corneal biomechanical parameters are basically recovered in the 30d postoperative.

Novel technique of sutureless glueless intrascleral fixation of single-piece intraocular lens / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To explore single centre results of sutureless intrascleral fixation of single-piece posterior chamber intraocular lens(IOL).<p>METHODS: In this prospective study, 50 aphakia cases were evaluated. Preoperative and postoperative visual acuity, slit lamp and fundus examination, applanation tonometry, keratometry, IOL MASTER measurement, optical coherence tomography(OCT), Scheimpflug imaging were done for an extensive evaluation.<p>RESULTS: All IOLs were successfully implanted at the desired position without intraoperative complications. Postoperative complications included corneal edema(<i>n</i>=2), raised intraocular pressure(IOP)(<i>n</i>=3), cystoid macular edema(CME)(<i>n</i>=1)and decentration(<i>n</i>=2). All were managed to the level of good visual recovery. Surgery videos were retrospectively evaluated in cases of postoperative complications. There was no significant change in corneal astigmatism.<p>CONCLUSION: After extensive 6mo follow up with evaluation of a variety of parameters, our technique of sutureless, glueless scleral fixation of IOL using single-piece IOL has shown favorable results and a potential option in visual rehabilitation.

Aplanamento corneano após DMEK associado a facoemulsificação em paciente com distrofia endotelial de Fuchs, ceratocone e catarata / Corneal flattening after simultaneous DMEK and phacoemulsification in patient with Fuchs endothelial dystrophy, keratoconus and cataract combined

Resumo Descrição de relato de caso de paciente com ceratocone (KC), Distrofia Endotelial de Fuchs (DEF) e catarata concomitantes com descompensação corneana submetido a Ceratoplastia Lamelar Posterior pela técnica Descemet's Membrane Endothelial Keratoplasty (DMEK) associado a facoemulsificação com implante de lente intraocular (LIO). Observou-se aplanamento corneano significativo no pós-operatório e acuidade visual final sem correção de 20/25 . Destaca-se a possibilidade do DMEK como alternativa à Ceratoplastia Penetrante (Penetrating Keratoplasty - PK) em casos de DEF e KC associados. Aplanamento corneano pode ocorrer neste grupo de pacientes, o que pode resultar em imprevisibilidade refracional no cálculo do poder da LIO ao se optar por facectomia combinada. Neste relato, apesar da modificação da curvatura corneana após cirurgia combinada de DMEK com facectomia, a acuidade visual final sem correção foi satisfatória, demonstrando a possibilidade de sucesso desta abordagem na coexistência de DEF, KC e Catarata. Entretanto, a possibilidade de mudança significativa na curvatura corneana deve ser considerada em pacientes com KC, edema de córnea secundário a DEF e catarata, na decisão de cirurgia simultânea ou em dois tempos.

Abstract This is a case report of a patient with concomitant Keratoconus (KC), Fuchs Endothelial Dystrophy (FED) and cataract with corneal decompensation submitted to Posterior Lamellar Corneal surgery (Descemet's Membrane Endothelial Keratoplasty - DMEK) associated with phacoemulsification with intraocular lens (IOL) implantation. Corneal flattening and uncorrected visual acuity of 20/25 was observed in the postoperative period. We reasure the viability of DMEK as an alternative to Penetrating Keratoplasty (PK) in cases of associated DEF and KC associated. Changes in corneal curvature may occur in this group of patients and lead to the possibility of refractive unpredictability in IOL calculation when performing a combined cataract surgery. Despite unexpected corneal flattening, satisfactory final visual acuity was achieved, demonstrating the possibility of success of this approach in the coexistence of the three conditions. Nonetheless, the possibility of corneal curvature changes should be considered in patients with KC and corneal decompensation due to FED in decision making, regarding simultaneous or sequential surgical approach.

Evaluation of Scheimpflug imaging system as an added tool in improving the accuracy of reference marking (as compared to the slit lamp marking system) for toric intraocular lens implantation

Purpose: To assess the role of Scheimpflug imaging in improving the accuracy of reference marking for toric IOL implantation. Methods: In this prospective, randomized, clinical trial all patients with cataract and pre-existing significant regular corneal astigmatism, who required implantation of a toric IOL were included in the study, and patients with any ocular pathology or abnormality were excluded. Patients were divided into two groups: For one group of patients, Group I (GI), reference marking was finalized using slit lamp only, and for the second group, Group II (GII), after slit lamp marking, the reference marks were checked using Goniometer of Scheimpflug imaging. The primary outcome was to determine the axis of toric intraocular lens (IOL) postoperatively (within 1 hour) and compare it with the desired axis of placement. Results: We found a statistically significant difference in the two groups (P < 0.001) suggesting Group II (4 step technique) is better than Group I (3 step technique). Conclusion: Scheimpflug imaging, an extra step preoperatively, is an effective measure to reduce errors in reference marking and thereby improving the refractive outcome of toric intraocular lens.

Diabetes mellitus tipo 2: cambios densitométricos del cristalino / Type 2 diabetes mellitus: lens densitometric changes

La diabetes mellitus es la responsable de la quinta parte de todas las cataratas, el sistema de cámara rotatoria scheimpflug permite estudiar a profundidad los primeros cambios en la densidad de estos cristalinos, estableciendo valores densitométricos en pacientes con Diabetes Mellitus tipo 2, con buena agudeza visual sin retinopatía diabética, y comparar dichos valores con un grupo control sin la enfermedad, desde junio de 2017 hasta marzo de 2018. Métodos: se realizó un estudio comparativo, exploratorio y prospectivo, la población y muestra estuvo compuesta por pacientes que acudieron a la consulta oftalmológica del Hospital Domingo Luciani. Resultados: todos los valores densitométricos fueron mayores en los pacientes con diabetes que en los normales. La mayor diferencia se produce en los valores del núcleo, seguido de la cápsula anterior acercándose a la significancia estadística (p=0,02) y (p=0,01) respectivamente. El 75% de los pacientes con diabetes presentaron cambios importantes en densitometría de la cápsula anterior y el 40% en el núcleo. Conclusiones: la cápsula anterior en pacientes con diabetes de menor edad (50 a 60 años) presentó valores más elevados de densitometría con relación a los controles. En los grupos de 61 a 70 y 71 a 80 los valores fueron menores; se concluye que los cambios tempranos en la cápsula anterior se deben a la diabetes. En cuanto al núcleo se observó en el grupo control un incremento progresivo de la densidad a medida que iba aumentando la edad, pero al agregarse el factor diabetes, aumentaron notablemente los valores, acentuando de esta manera la evolución de la catarata senil. La diabetes altera precozmente la densidad de la capsula anterior y núcleo(AU)

Diabetes mellitus is responsible for one fih of all cataracts, the scheimpflug rotary chamber system allows to study in depth the first changes in the density of these lenses, establishing densitometric values in patients with Type 2 Diabetes Mellitus, with good visual acuity without diabetic retinopathy, and compare these values with a control group without the disease, from June 2017 to March 2018. Methods: a comparative, exploratory and prospective study was carried out, the population and sample was composed of patients who attended the ophthalmological consultation of the Domingo Luciani Hospital. Results: all densitometric values were higher in diabetic patients than in normal patients. The greatest difference occurs in the nucleus values, followed by the anterior capsule approaching the statistical significance (p = 0.02) and (p = 0.01) respectively. 75% of diabetic patients presented significant changes in densitometry of the anterior capsule and 40% in the nucleus. Conclusions: the anterior capsule in diabetic patients with younger age (50 to 60 years) presented higher values of densitometry compared to non-diabetics. In the groups of 61 to 70 and 71 to 80 the values were lower; We conclude that the early changes in the anterior capsule are due to diabetes. As for the nucleus, a progressive increase in density was observed in the control group as the age increased, but when the diabetes factor was added, the values increased markedly, thus accentuating the evolution of the senile cataract. Diabetes precociously alters the density of the anterior capsule and nucleus(AU)

Effects of LASIK on Biomechanical Properties of Human Cornea / 医用生物力学

Objective To study the changes in biomechanical properties of human cornea after laser in situ keratomileusis (LASIK) and predict corneal stiffness after the LASIK surgery. Methods According to the measurement results from corneal visualization scheimpflug technology (Corvis ST), the corneal tangent stiffness coefficient (STSC) and energy absorbed area (Aabsorbed) were calculated. The change patterns of corneal stiffness and viscosity after refractive surgery were analyzed. Results The difference of corneal STSC and Aabsorbed before and after LASIK had a statistical significance (P<0.05). The obtained formula for predicting corneal stiffness after refractive surgery was: Sbefore surgery =1.055bIOPbefore surgery + 0.015CCTbefore surgery，Safter surgery =0.937Sbefore surgery +0.019CCTafter surgery. Conclusions LASIK surgery not only changes corneal thickness, but also reduces corneal stiffness and viscosity. Prediction of corneal stiffness after surgery can provide guidance for the design of clinical surgery and improve the safety of surgery.

A comparative study of viscoelasticity between normal cornea and keratoconus / 生物医学工程学杂志

Study of the mechanical properties of in vivo corneal materials is an important basis for further study of corneal physiological and pathological phenomena by means of finite element method. In this paper, the elastic coefficient ( ) and viscous coefficient ( ) of normal cornea and keratoconus under pulse pressure are calculated by using standard linear solid model with the data provided by corneal visualization scheimpflug technology. The results showed that there was a significant difference of and between normal cornea and keratoconus cornea ( < 0.05). Receiver operating characteristic curve analysis showed that the area under curve (AUC) for , and their combined indicators were 0.776, 0.895 and 0.948, respectively, which indicated that keratoconus could be predicted by and . The results of this study may provide a reference for the early diagnosis of keratoconus and avoid the occurrence of keratoconus after operation, so it has a certain clinical value.