Scheimpflug Topography Research Articles

Comparison of Toric Intraocular Lens Axis Accuracy between Optical Biometry and Dual Scheimpflug Topography.

To evaluate the accuracy of toric intraocular lens (IOL) axis prediction between two preoperative measurement devices: the optical biometry (IOLMaster 500 or 700) and the dual Scheimpflug topography (Galilei G4). Medical records of 64 eyes from 44 patients who underwent phacoemulsification and posterior chamber toric IOL (Zeiss AT TORBI 709M) implantation between July 2017 and January 2022 were reviewed. All patients underwent preoperative evaluation by optical biometry (IOLMaster 500 or IOLMaster 700) and Galilei G4. The gold-standard axis that minimizes astigmatism was calculated by the online Toric Results Analyzer postoperatively and compared to the preoperative toric IOL axis calculated by the Z CALC online IOL calculator using parameters from either IOLMaster or Galilei G4. The axis error (AE) and the absolute axis error (AAE) between the gold-standard axis and the preoperative calculated axis were analyzed to assess the accuracy of each device. Mean flat keratometry (K) and steep K were 42.99 diopter (D) and 45.61 D in IOLMaster, and 43.04 D and 45.51 D in Galilei G4, which did not show any significant difference. Mean keratometric astigmatism (KA) was 2.62 D in IOLMaster and 2.46 D in Galilei G4, which also did not show any statistical difference. KA axis did not show any significant difference between IOLMaster and Galilei G4. The mean AE and AAE were 0.19° and 6.84° by IOLMaster, and -0.80° and 7.98° by Galilei G4. The AE and AAE by IOLMaster did not show any significant difference compared to those of Galilei G4 (p=0.583, p=0.346, respectively). This study suggests that the Galilei G4 demonstrated a similar level of accuracy to the IOLMaster in predicting the toric IOL axis, based on the gold standard axis provided by the toric results analyzer.

Intraocular Lens Power and Corneal Topographic Change After Pterygium Surgery

PurposeTo investigate the impact of pterygium excision on intraocular lens (IOL) power calculation and corneal astigmatism. DesignsProspective cohort study MethodsWe enrolled 30 eyes with primary pterygium that underwent pterygium excision with a conjunctival autograft. IOL power calculation and keratometry using the IOL Master 700, along with topographic parameters using the Pentacam Scheimpflug topography system, were performed preoperatively and at 1, 3, 6, and 12 months postoperatively. We analyzed correlations between pterygium length/area and IOL power, as well as corneal topographic changes. ResultsThe mean pterygium length was 2.08 ± 0.58 mm, and the mean area was 6.05 ± 2.41 mm2. One year after pterygium surgery, the calculated IOL power values using all formulas were lower than the preoperative values. Pterygia with a horizontal length of 1.73 mm and an area of 4.45 mm2, and those with a horizontal length of 2.25 mm and an area of 6.95 mm2 created 0.5 D and 1.0 D errors in calculated IOL power, respectively (p<0.001). The calculated IOL power values changed significantly from preoperative to six months postoperatively but did not change significantly from six to 12 months postoperatively. Pterygia with a horizontal length greater than 1.83 mm (p<0.001) and an area greater than 5.1 mm2 (p < 0.001) created a 2.0 D error in anterior corneal astigmatism. ConclusionsPterygium causes errors in IOL power calculation, with greater pterygium length/area exerting a larger effect. Cataract surgery with IOL implantation is recommended at least six months after pterygium surgery. In combined case, calculated IOL power should be decreased by 0.5-1.5 D based on the pterygium length/area.

Optical quality of the cornea after Descemet membrane endothelial keratoplasty surgery: early results from Türkiye.

Descemet membrane endothelial keratoplasty (DMEK) is increasingly favored in the treatment of endothelial dysfunction due to its benefits, which include swift visual rehabilitation and recovery, a relatively low rejection rate, and superior refractive stability. In this study, we examined alterations in corneal clarity among patients who underwent DMEK and correlated these densitometry findings with other optical parameters of corneal topography. The study incorporated 35 eyes from 35 patients who had previously undergone DMEK surgery for pseudophakic bullous keratopathy at Ankara Bilkent City Hospital. The results from these patients were compared with those from a healthy control group. The preoperative and postoperative optical parameters of the patients were assessed using Pentacam Scheimpflug topography (Oculus). We observed significant decreases in corneal densitometry in the 0-2 mm and 2-6 mm zones of the anterior, posterior, central, and total layers at the sixth month postoperatively compared to the preoperative period (P<0.05). The corneal densitometry values at postoperative month 6 were elevated in all layers and zones relative to the healthy group (P<0.05). The root mean square of higher-order aberrations in postoperative period was elevated significantly (P<0.001). Six months after operation, the optical quality of the cornea following DMEK surgery did not achieve the level of a healthy cornea.

Efficacy of keratometric values obtained from Sirius topographer® in nidek axial length-scan® for intraocular lens calculation after penetrating keratoplasty.

To evaluate the accuracy of keratometric values obtained from Scheimpflug (Sirius) topography using Nidek AL-Scan optical biometry (OB) for intraocular lens (IOL) power calculating after penetrating keratoplasty (PK). Thirty eyes of 26 patients were included in this study. The demographic information, complete ophthalmic examination, IOL calculation technique, and its effect on final refractive results were evaluated. The mean age of the patients was 52.76 ± 16.20 years. The mean K readings using Nidek AL-Scan OB, mean simulated K (SimK) (3mm), and mean pupillary power (MPP) (4.5mm) K readings using Sirius were 41.92 ± 5.05 D, 42.99 ± 5.78 D, and 43.30±6.23 D (p= 0.515). Both devices correctly calculated IOL power after PK; however, Sirius SimK (3mm) gave the lowest mean absolute error (MAE) results and can be safely used for IOL power calculation.

Commentary: Reliability, repeatability, and accuracy of Sirius topographer in assessing anterior segment morphology following laser peripheral iridotomy in primary angle-closure disease.

Commentary: Reliability, repeatability, and accuracy of Sirius topographer in assessing anterior segment morphology following laser peripheral iridotomy in primary angle-closure disease.

The use of preservative‐free hydrocortisone in the postoperative treatment regimen after trans‐PRK

AbstractPurpose: The purpose of this study was to exhibit the advantages of preservative‐free hydrocortisone in the postoperative treatment regimen of transepithelial photorefractive keratectomy (Trans‐PRK) for the promotion of epithelization and minimalization of early haze appearance.Methods: In this prospective, randomized controlled study, 40 patients who had undergone trans‐PRK were divided into two equal groups, the first group received hydrocortisone (Softacort®, Laboratoires Thea) 2 drops 4 times daily for 7 days and the control group received no complementary medication. Both groups were given: artificial tears 2 drops hourly for 7 days, then administered every 2 h for 21 days and tapered till 3 months post‐operation, antibiotic drops (quinolone) 4 times daily and autologous serum hourly for 7 days, and a bandage contact lens till complete epithelization of the surgical wound. Patients were monitored daily to determine the time of a complete epithelization and then on day 15 and 30 to assess any signs of early‐onset haze and visual acuity. Scheimpflug topography and anterior segment OCT were performed on day 15 and 30 as well as IOP tonometry.Results: The results showed a significant decrease in recovery days in patients treated with hydrocortisone compared to the control group (p &lt; 0.0006) which was associated with a higher rate of early‐onset haze. Both groups had satisfactory visual acuity and no significant differences in their IOP were observed.Conclusions: In conclusion, the use of hydrocortisone sodium phosphate drops (Softacort®) has been shown to be efficient in corneal epithelization and haze management and safe in patients after trans‐PRK.

The monitoring of the speed of re‐epithelization after refractive surgery performed with the method of Trans‐PRK, with the use of hydrocortisone sodium phosphate (Softacort)”

AbstractPurpose: To exhibit the advantages of preservative‐free hydrocortisone in the postoperative treatment regimen of transepithelial photorefractive keratectomy (Trans‐PRK) for the promotion of epithelization and minimalization of early haze appearance.Methods: In this prospective, randomized controlled study, 40 patients who had undergone trans‐PRK were divided into two equal groups, the first group received hydrocortisone (Softacort®, Laboratoires Thea) 2 drops 4 times daily for 7 days and the control group received no complementary medication. Both groups were given: artificial tears 2 drops hourly for 7 days, then administered every 2 h for 21 days and tapered till 3 months post‐operation, antibiotic drops (quinolone) 4 times daily and autologous serum hourly for 7 days, and a bandage contact lens till complete epithelization of the surgical wound. Patients were monitored daily to determine the time of a complete epithelization and then on day 15 and 30 to assess any signs of early‐onset haze and visual acuity. Scheimpflug topography and anterior segment OCT were performed on day 15 and 30 as well as IOP tonometry.Results: The results showed a significant decrease in recovery days in patients treated with hydrocortisone compared to the control group (p &lt; 0.0006) which was associated with a higher rate of early‐onset haze presentation. Both groups had satisfactory visual acuity and no significant differences in their IOP were observed.Conclusions: The use of hydrocortisone sodium phosphate drops (Softacort®) has been shown to be efficient in corneal epithelization and haze management and safe in patients after trans‐PRK.

Comparative study for evaluation of the horizontal white-to-white corneal diameter using the optic low-coherent reflectometer and the Scheimpflug topography in normal Egyptian population

Purpose: Comparison of the horizontal white-to-white corneal diameter measured by Lenstar LS 900® (Haag‑Streit AG, Koeniz, Switzerland) and TOMEY TMS-5® (topographic modeling system, version 5) to assess the agreement between them. Setting: El-Agouza police hospital, Egypt. Materials and methods: Comparative prospective cross-sectional clinical study in which measurements of the horizontal WTW corneal diameter were obtained by LENSTAR LS900 and TOMEY TMS-5. Results: The study included 219 eyes of 115 randomly chosen normal Egyptian subjects of both sex (68 males and 47 females). The WTW diameters measured by LENSTAR LS900 and TOMEY TMS-5 ranged from 10.88 to 13.15 mm and 10.69 to 12.94 mm respectively. Lenstar LS 900 gives slightly higher values for WTW diameter than TOMEY TMS-5. Pearson coefficient of correlation (r) revealed a strong statistically significant level of correlation between WTW values measured by both devices (r = 0.87 with p&lt;0.01). Paired samples t-test showed a small mean inter-device difference with high statistical significance (0.29 mm and p&lt;0.01). The Bland-Altman limits of agreement for WTW values measured by them showed a LoA extending from -0.1 to 0.68 mm. Cf the patient.

Distribution of angle lambda and pupil offset as measured by combined Placido Scheimpflug Topography

BackgroundAngle lambda is the angle between the pupillary axis and the line of sight. It is important for accurate centration during anterior segment surgery. The purpose of this study is to identify the distribution of angle lambda and pupil center offset as measured by a combined placido disc Scheimpflug topography system.MethodsA prospective non-randomized study was performed on 2178 eyes in Eye World Hospital, Giza, Egypt. Sirius device (CSO, Costruzione Strumenti Oftalmici, Florence, Italy, version 3.2.1.60) was used to measure average keratometry (K), anterior chamber depth (ACD), central corneal thickness (CCT), horizontal visible iris diameter (HVID), pupil radius (PR), pupil center intercept x-component (PCI-x), and pupil center intercept y-component (PCI-y). Axial length (AL) was measured by immersion A-scan Eyecube Ultrasonography device (Ellex, Adelaide, South Australia, Australia). Angle lambda was calculated by a trigonometrical equation. Pearson correlation was used to analyze the correlation between angle lambda and age and refraction.ResultsAverage angle lambda in all eyes was 3.32° ± 1.99. Mean angle lambda was significantly smallest in myopia and largest in hyperopia. Age correlation to angle lambda was insignificant. Average PCI-x and PCI-y in all eyes was − 0.047 mm and + 0.091 mm, respectively.ConclusionsAngle λ is significantly larger in hyperopia than myopia, and the effect of age is insignificant. Pupil center offset was horizontally greater in hyperopia than in myopia. We therefore encourage the preoperative assessment of angle λ to avoid decentered ablation, especially when treating hyperopia.

Instability of tear film and loss of meibomian glands in patients with acne vulgaris.

In this prospective study, we compared ocular clinical variables in patients with acne vulgaris with those of healthy controls. These variables included tear film break-up time, meibomian gland dropout rate, and anterior chamber parameters. Our sample comprised 73 eyes from 73 patients with acne vulgaris and 67 eyes from 67 healthy controls. All participants underwent a non-invasive first tear film break-up time test and the average tear film break-up time was evaluated. Meibography was used to identify any meibomian gland dropout. The parameters of the cornea and anterior chamber were measured using Scheimpflug topography imaging. Finally, the ocular surface disease index questionnaire was administered to score each participant on their subjective experience of ocular complaints. The noninvasive first tear film break-up time values of the acne vulgaris Group and the control Group were 4.7 ± 2.8 and 6.4 ± 3.5 sec, respectively. There was a significant difference between the groups (p=0.016). The number of eyes with tear break-up at any time during the measurement period was also significantly higher in the acne Group (p=0.018). In the acne vulgaris Group, the mean meibomian gland dropout rates were 33.21 ± 15.5% in the upper lids and 45.4 ± 14.5% in the lower lids. In the control group, these rates were 15.7 ± 6.9% and 21 ± 9.7% respectively. Dropout was significantly higher in the acne group for both the upper and lower lids (p=0.000). We found impaired tear stability in patients with acne vulgaris and a high rate of meibomian gland dropout. These glands play a key role in tear stability and their dropout is likely to result in evaporative dry eye. Measurement of the variables in this study allows objective diagnosis of this condition using a non-invasive, dye-free methodology, with minimum contact.

Corneal Scheimpflug topography values to distinguish between normal eyes, ocular allergy, and keratoconus in children

To identify and compare keratometric, corneal thickness, and elevation parameters and indices among healthy children, ocular allergy, and keratoconus using the OCULUS Pentacam Scheimpflug topography system. This study included healthy children, children with ocular allergy (OA) without keratoconus, and children with keratoconus (KC). The study design consisted of a prospective evaluation and review of medical records from a Brazilian ophthalmology department. The exclusion criteria were inability to undergo the ocular exam, other ocular diseases, contact lens wear, and topographic corneal ectasia. The effect of each corneal parameter was evaluated using univariate and multivariate logistic regression models adjusted for sex and age, and ROC curves were used to assess the ability each variable to discriminate among groups. A total of 182 subjects were included: healthy children (n = 99), children with OA (n = 32), and children with KC (n = 51). Groups differed in terms of sex, with more males in the OA group (73.2%) and the KC group (67.7%) than in the control group (40.9%). All corneal parameters studied differed significantly between the control and KC groups, and between the OA and KC groups; they also differed significantly between the three groups in terms of astigmatism, q-value, CCT, TP, BAD-D, and ARTmax values. We present the first study to describe and compare corneal tomographic parameters in healthy children, OA, and KC. Keratometry indices, ACD, ARTmax, AETP, and PETP were found to be the most useful for differentiating between healthy and KC children.IBR registry number: CAAE 54921916.9.0000.5404.

The role of peripheral ocular length and peripheral corneal radius of curvature in determining refractive error

PurposeThe purpose of this study was to extend the knowledge of peripheral biometric component and its relationship to refractive status in healthy individuals by determining the correlation between peripheral ocular length to peripheral corneal radius ratio and the refractive error. MethodsThis prospective study was conducted on thirty-three healthy adult participants. Refractive error was assessed objectively and subjectively and recorded as the mean spherical equivalent. Central and peripheral ocular lengths at 30° were assessed using partial coherence interferometry under dilation with 1% tropicamide. Central and peripheral corneal radius of curvature was assessed using Scheimpflug topography. Peripheral ocular lengths at 30° were paired with peripheral corneal curvatures at the incident points of the IOLMaster beam (3.8mm away from corneal apex) superiorly, inferiorly, temporally and nasally to calculate the peripheral ocular length-peripheral corneal radius ratio. Descriptive statistics were used to describe the distribution and spread of the data. Pearson’s correlation analysis was used to present the association between biometric and refractive variables. ResultsRefractive error was negatively correlated with the axial length-central corneal radius ratio (r=−0.91; p<0.001) and with 30° peripheral ocular length-peripheral corneal radius ratio in all four meridians (r≤−0.76; p<0.001). The strength of the correlation was considerably lower when only axial length or peripheral ocular lengths were used. ConclusionUsing the ratios of peripheral ocular length-peripheral corneal radius to predict refractive error is more effective than using peripheral corneal radius or peripheral ocular length alone.

Central and mid-peripheral corneal astigmatism in an elderly population: a retrospective analysis of Scheimpflug topography results

Implantation of toric intraocular lenses (IOLs) has become standard in the correction of corneal astigmatism. The IOL selection is based on keratometric measurements of the central cornea. However, mid-peripheral corneal changes may yield suboptimal correction in patients with larger pupils. This study retrospectively analyzed corneal topography data collected using a Scheimpflug device during routine clinical examinations. Of 11,953 patients, 641 met the inclusion criteria. Total corneal astigmatism was compared between five concentric zones (2–6 mm) using vector analysis. The absolute difference between astigmatism at 2 mm and 6 mm was 0.30 D (− 0.36 to 0.64), which decreased to 0.10 D (0 to 0.20) between the 5- and 6-mm zone. With-the-rule astigmatism was the most prevalent (53%), 34% had against-the-rule (ATR), and 13% had oblique. The decrease of the cylinder power with the diameter differed significantly between the three types, with ATR and oblique astigmatism being associated with the steepest change. Patients with high corneal astigmatism tend to demonstrate larger differences between the center and mid-periphery than those with low and moderate astigmatism. In conclusion, we demonstrated that central corneal astigmatism differs from that measured at the mid-periphery and that a larger difference was found in patients with ATR, oblique and high astigmatism.

Topographic, elevation, and keratoconus indices for diagnosis of keratoconus by a combined Placido and Scheimpflug topography system.

To determine the accuracy of various corneal parameters in keratoconus diagnosis using Scheimpflug camera combined with Placido disk corneal topography (Sirius, CSO). One hundred and fifteen keratoconic eyes (group1) and a 111 normal eyes (group2) were assessed prospectively between March 2018 and July 2019 for: corneal keratometric indices (K1, K2, sim K, apex curvature) at different corneal rings of both corneal surfaces, central corneal thickness (CCT), thinnest corneal thickness (TL), corneal asphericity (Q), elevation at thinnest point, root mean square (RMS), and root mean square per area (RMS/A) in spherical, aspheric and aspherotoric reference for both corneal surfaces and keratoconus summary parameters; surface asymmetry index of front and back (SIf, SIb respectively), elevation at keratoconus vertex front and back (KVf, KVb respectively), Baiocchi Calossi Versaci front and back index (BCVf, BCVb) and its vector summation (BCV) and convergence radius and cutoff value for each was calculated. All studied indices were significantly different between the two groups. The highest predictive accuracy "Area under receiver operating characteristic curve (AUROC)" of 0.999 was observed for BCVf, KVb, RMS and RMS/A at 6 mm aspherotoric reference posterior surface. Keratoconus summary indices had high AUROC (0.986, 0.984, 0.948, 0.999, 0.999, 0.998 respectively). Curvature indices had lower AUROC than elevation indices, except for curvature of corneal apex at anterior (0.98) and posterior surface (0.99). Higher AUROC was noted with elevation at thinnest point especially at aspherotoric reference surface. Sirius topography showed high predictive accuracy in detection of keratoconus. Elevation indices and keratoconus summary parameters have the highest diagnostic ability.

Korneal Çapraz Bağlama Tedavisi Sonrası Epitel Kalınlığın Değişimi: Retrospektif Bir Araştırma

Objective: To assess the corneal epithelial remodeling after corneal crosslinking (CXL) and to investigate the relation between topographic parameters and epithelial thickness change. Material and Methods: Sixty-three eyes of 43 keratoconus patients were included in this retrospective study. Keratometry (K) and elevation data were assessed by Scheimpflug topography and corneal and epithelial thickness profile was obtained by anterior segment spectral-domain optical coherence tomography pre-operatively and at the 1st, 6th and 12th months after CXL. Results: Significant decreases were observed in mean K (p=0.014), maximum K (p=0.049), and mean central corneal thickness (p<0.007) after CXL. Superior corneal epithelial thickness was significantly thinner (p<0.001) and the difference between the minimum and maximum epithelial thickness was less at the post-operative first month and didn't change significantly afterwards. Standard deviation of epithelial thickness across the central 5 mm region statistically decreased in the follow-up period (p=0.008). Conclusion: Significant regularization of the epithelial thickness profile was seen in one year after epithelium-off CXL. Demonstrating the normalization of the corneal epithelium and understanding its impact on the post-operative healing process might contribute to the optimization of treatment protocols.

Kuru Göz Hastalarında Noninvaziv Değerlendirme: Gözyaşı Ozmolaritesi, Gözyaşı Menisküs Yüksekliği ve Noninvaziv Gözyaşı Kırılma Zamanının Diğer Testlerle İlişkisi

Objective: To determine the correlation of non-invasive tests with conventional tear function tests in dry eye patients. Material and Methods: One hundred and twenty-two eyes of 61 patients over 18 years old who applied to Çanakkale Onsekiz Mart University School of Medicine, Department of Ophthalmology with dry eye were included in the study. After general ophthalmological examination including best corrected visual acuity, biomicroscopic examination, non-invasive methods like Ocular Surface Disease Index (OSDI) scoring, tear osmolarity, non-invasive tear break-up time (NI-TBUT) measurement with Scheimpflug topography, meibomography, and measurement of the lower lid meniscus height (TMH) with optical coherence tomography were performed. After non-invasive tests, conventional tear function tests like Schirmer test, TBUT, cornea and conjunctiva staining were applied respectively. Results: A positive correlation was found between NI-TBUT and conventional TBUT (p<0.01 Spearman's rho: 0.473). TBUT was found to be positively correlated with Schirmer test and negatively correlated with corneoconjunctival staining (p<0.01 Spearman's rho: 0.393, rho:-0.418). Schirmer test results were correlated positively with TMH and negatively correlated with OSDI scoring and corneoconjunctival staining (p<0.05 Spearman's rho: 0.181; p<0.05 Spearman's rho:-0.214; p<0.01 Spearman's rho:- 0.394). Tear osmolarity test results and meibomography did not correlate with any test. Conclusion: The non-invasive and objective measurement of NI-TBUT may be a better diagnostic modality than TBUT for dry eye patients. Tear osmolarity and meibomography were not significant for diagnosis of early stage dry eye patients.

Assessment of cataract forming effect of diabetes in young adults by lens densitometer.

To investigate the effect of the diabetes on cataract formation by Pentacam Scheimpflug topography system. Thirty diabetic patients and thirty-five healthy control subjects were included in the study. Exclusion criteria were smoking, high refractive error, any systemic disease or drug usage associated with cataract formation and to have diabetic retinopathy. The duration of diabetes and HbA1c level were recorded. A comprehensive ophthalmologic examination was performed in all cases. Pentacam (Oculus, Wetzlar, Germany) three-dimensional lens densitometer module was used to measure density of anterior, nuclear and posterior lens regions. Mean age of group 1 and group 2 was 37.80 ± 5.51years and 36.51 ± 3.77years, respectively. There were not any difference between groups in the means of age and sex (P = .271; P = .700). The mean duration of diabetes in group 1 was 4.23 ± 3.71years (6months-10year). The mean HbA1c level was 8.12 ± 2.07% (5.4-12.7%). Anterior, nuclear and posterior mean lens densitometry measurements were significantly higher in group 1 (diabetic group) than group 2 (control group) [(8.90 ± 0.59%; 8.05 ± 0.72% P = < .001), (7.52 ± 0.31%; 7.00 ± 0.59% P = < .001), (7.25 ± 0.31%; 6.90 ± 0.73% P = .006), respectively]. Diabetes may have cataractous effect in anterior, nuclear and posterior regions of the lens.

Model-based motion compensation for corneal topography by optical coherence tomography

Corneal topography is an essential tool in ophthalmology, in particular for surgical planning and diagnostics. Optical coherence tomography (OCT) enables cross-sectional or volumetric imaging with high resolution. It is, however, not widely used for corneal topography. A major reason for this is that conventional beam-scanning OCT is susceptible to eye motion compared to established modalities, which measure corneal shape in a single shot. To overcome this limitation, we propose a novel pipeline for motion-compensated OCT-based corneal topography. The pipeline includes three main features: (1) continuous, two-dimensional scanning; (2) the three-dimensional continuous motion compensation in postprocessing; and (3) regularised Zernike reconstruction. First, we evaluated our method on an eye phantom that is moved to mimic typical eye motion. The proposed motion compensation was able to determine and correct the movements of the phantom. Second, we performed an in vivo study on 48 eyes, measuring each eye twice with our OCT-based topography, Placido disc topography (Atlas 9000, Carl Zeiss Meditec), and Scheimpflug (Pentacam, Oculus) topography. We then compared the performance of the OCT-based topography to the reference topographies in terms of repeatability and equivalence. The results confirm the necessity and efficiency of the presented motion compensation and validate the proposed methods for scanning and reconstruction.

Accelerated (45 mW/cm2) Transepithelial Corneal Cross-Linking for Progressive Keratoconus Patients: Long-Term Topographical and Clinical Outcomes.

Aims: We characterized long-term clinical outcomes of accelerated (45 mW/cm2) transepithelial corneal cross-linking (ATE-CXL) for the treatment of progressive keratoconus.Methods: Forty-two eyes from 37 patients treated for keratoconus were observed. ATE-CXL was performed using riboflavin and pulsed-light ultraviolet treatment (45 mW/cm2, 7.2 J/cm2). Structural and functional measurements were made after 1 week and 1, 3, 6, 12, 24, 36, and 48 months subsequently. Corneal topographic parameters were observed using Scheimpflug topography (Pentacam software).Results: Surgery was uneventful in all subjects. Mean uncorrected (UDVA) and corrected distance visual acuity (CDVA) (logMAR) were 0.99 ± 0.58 and 0.44 ± 0.27 (P = 0.022), 0.24 ± 0.29 and 0.27 ± 0.35 (P = 0.601), at baseline and last follow-up, respectively. The pre-operative mean maximum keratometry (Kmax) value was 57.29 ± 9.13 diopters (D), and the thinnest corneal thickness (TCT) was 456.21 ± 44.66 μm. Mean Kmax was 56.67 ± 9.36 D, 4 years post-operatively (P = 0.781). TCT changed to 453.17 ± 46.76 μm at 4 years post-operatively (P = 0.780). Multiple linear regression indicated that patients with thinner pre-operative TCT (≤ 450 μm) showed decreasing post-operative average keratometry (Kavg) and increasing post-operative TCT. Patients with posterior central elevation (PCE) >80 μm showed decreasing post-operative Kavg as well as post-operative PCE. No complications were observed during follow-up.Conclusion: Stabilization after ATE-CXL was achieved for the treatment of keratoconus. The clinical efficacy of ATE-CXL in advanced keratoconus patients with thin corneal thickness and greater PCE will require further investigation.

The Reliability between Placido Topography and Scheimpflug Topography in Normal Corneas with Astigmatism less Than 0.50 Dc

Purpose: This Clinical research was targeted to experimentally investigate the reliability between Placido topography and Scheimpflug topography in normal corneas with astigmatism ≤ ±0.50 Dc by comparing the refractive powers at the 4 main meridians (180⁰ - 90⁰) in order to study any differences between the two topographers and their reliability. Comparing the reliability measurements of Placido disk topography (CSO- Modi 02 Corneal Topographer with Phoenix Full &amp; Pupil Module Software) with those of a high-resolution rotating Scheimpflug camera (Pentacam-Oculus,) and assess the agreement between these two topographers in measuring corneal power in normal eyes without astigmatism (≤ 0.50 Dc).&#x0D; Methods and Materials: Measurements were taken from 56 eyes corresponding to a proportion of patients, of which 26 were men with a mean age of ± 30 years and 30 were women with a mean age of ± 27 years. Refractive power maps were taken from the anterior cornea, having results for the steep meridian value (Ks), the flat meridian value (Kf), mean keratometric value (Km), and cornea astigmatism (Ks-Kf). The same examiner took all the data from measuring these 56 eyes. The results for each refractive map from the two topographers was taken with values for meridians (180⁰- 90⁰). Then the there was a statistical analysis comparing the values of (CSO) and (Pentacam) for those 56 eyes measured.&#x0D; Results: The statistical analysis for all meridians based on the results and as far as normal corneas with astigmatism ≤ ±0.50 Dc are concerned, the Placido topography (CSO) and Scheimpflug imaging technique (Pentacam), can be considered as equivalent in terms of diagnostic credibility and accuracy for primary health care, fitting contact lenses, etc. as the correlation coefficient r did not show any important differences for both instruments. For the 90⁰ meridian the correlation coefficient was 0.79, Significance level P=0.0001 and 95% confidence interval ranges from 0.67 to 0.87. For the 180⁰ meridian the correlation coefficient was 0.48, Significance level P&lt;0.0001 and 95% confidence interval ranges from 0.25 to 0.66.&#x0D; Conclusion: In terms of diagnosis of pathology and follow-up, contact lens fitting especially for the anterior cornea surface these two instruments can work quite the same that’s why a small clinical practitioner should have at least a Placido topographer. Corneal topography is an important instrument in order to measure the shape and refractive power of the cornea. Corneal topography gives practitioners an important tool to fit contact lenses asses the power and the cornea shape and helps to evaluate complications of the contact lens in relation with the corneal surface. These instruments continue to develop techniques and software in order to investigate and evaluate corneal surfaces and the integrity of the tear film, so that they can provide better solutions for their contact lens patients.