Pentacam Oculus Research Articles

Pentacam vs SP3000P specular microscopy in measuring corneal thickness.

To compare corneal thickness (CT) measurements obtained with SP3000P specular microscope and Pentacam in eyes screened to undergo refractive surgery (RS). In this prospective study, a non-randomized consecutive series of 73 healthy eyes (age range: 14-78 years; mean=38.4±14.9) underwent CT measurement with both Oculus Pentacam and Topcon SP3000P specular microscope to assess their suitability to undergo corneal RS. CT measurements with SP3000P ranged from 451 to 609 μs (mean 523.1±34.4 μs). The measurements obtained with Pentacam ranged at the corneal apex from 477 to 672 μs (mean 558.9±38.9 μs), at the pupil center from 477 to 672 μs (mean 557.9±38.9 μs) and at the thinnest point from 474 to 669 μs (mean 551.1±39.4 μs). CT measurements showed a good correlation but a statistically significant difference at the pupil center (mean -34.9±14.6 μs, R(2)=0.860, p<0.001), at the apex (mean -35.9±14.9 μs, R(2)=0.856, p<0.001) and at the thinnest point (mean -32±14.8 μs, R(2)=0.862, p<0.001). The calculated regression formulas were: y=0.816x+66.94 for the apex, y=0.819x+66.07 for the pupil center and y=0.810x+73.13 for the thinnest point; where y is the CT measured with the SP3000P and x is the measurement obtained with the Oculus Pentacam. Our results suggest that SP3000P measures thinner corneas compared to the Pentacam and that the correcting factor we identified should be applied to make comparisons between these two devices.

FRO 2014: Automated detection, classification and notification of pathological corneas using the Oculus Pentacam

AbstractTo develop an automated classification system for normal and abnormal corneal topography based on data obtained from the Pentacam, which can be used for the following purposes: 1. To investigate the variability of corneal topography. 2. To automatically detect pathological corneas such as keratoconus, high astigmatism, post‐refractive surgery and early onset of edema or corneal dystrophies (e.g. Fuchs dystrophy) before it is visible with the slit‐lamp. 3. To create an add‐on program to the Pentacam software that gives a warning message with a probability of belonging to a disease group when a new patient is measured.

Normative Values for Corneal Densitometry Analysis by Scheimpflug Optical Assessment

To describe the normative data for corneal Scheimpflug densitometry based on a cohort of normal participants. A total of 445 healthy participants were recruited for assessment (794 eyes). Left and right eyes were considered separately. All participants were assessed using the corneal densitometry analysis add-on to the standard software of the Oculus Pentacam. Densitometry measurements were obtained and expressed in standardized grayscale units (GSU). All participants were Caucasian; 42% were male and 58% were female. The mean age was 48.0 ± 15.3 years (range, 20.2-84.2 years). Mean corneal densitometry over the 12-mm-diameter area was 19.74 ± 3.89 GSU. When divided by radial zone, densitometry values were lowest in the central zone (16.76 ± 1.87 GSU) and highest in the periphery (27.36 ± 7.47 GSU). There was no difference between central zone and the surrounding 2- to 6-mm annulus (P > 0.05), though the 6- to 10-mm and the 10- to 12-mm zones displayed higher densitometry values (P < 0.001). When divided by depth, the anterior layer displayed the highest densitometry reading of 25.81 ± 5.14 GSU, which was significantly higher than that of both the central (P < 0.001) and the posterior layers (P < 0.001). Changes in corneal densitometry were correlated with age, though not within the central 6-mm-diameter ring. No sex difference was seen within the cohort. This add-on to the standard imaging software allows rapid and objective assessment of the corneal densitometry. We provide normative data that may be used as a reference facilitating research and complementing clinical examination.

The Effects of Epithelium-off Corneal Collagen Cross-linking on Peripheral Corneal Keratometry, Pachymetry as well as Scheimpflug Imaging Calculated Corneal Indices in Keratoconus

ABSTRACT Purpose To utilize Scheimpflug imaging to describe corneal changes in keratoconic patients undergoing collagen cross- linking. Study type Case series. Study design Retrospective chart review at two sites: Calgary, Alberta and Brandon, Manitoba, Canada. All patients were diagnosed with keratoconus and had undergone corneal collagen crosslinking. All patients had pre- and post-procedure imaging done with Oculus Pentacam. Results Sixty-one eyes of 48 patients with 6 months follow- up and 36 eyes of 27 patients with one year follow-up were included. Average age was 27 ± 12 years (15-48 years). Fifty- one males and 10 females were studied. At 1 year follow-up, all Pentacam indices were found to improve: ISV −4.44 ± 18.6 (p = 0.16), IVA −0.07 ± 0.27 (p = 0.12), KI −0.009 ± 0.082 (p = 0.49), CKI −0.012 ± 0.027 (p = 0.01), IHA −3.87 ± 23.3 (p = 0.33) and IDH −0.062 ± 0.308 (p = 0.24). Keratometry measurements were flatter at the pupil centre by 0.87 ± 2.53 D (p = 0.05). Kmax and Kmin were flatter by 0.58 ± 1.37 D (p = 0.02) and 0.33 ± 1.70 D (p = 0.25) respectively. Pupil center pachymetry was thinner by 12.9 ± 21.1 µm (p = 0.0006) at 6 months, as were the corneal apex and thinnest local by 12.9 ± 22.3 µm (p = 0.001) and 21.8 ± 54.6 µm (p = 0.05) respectively. However, all central pachymetry readings were not statistically different from baseline at the one year measurements. Peripheral corneal measurements at 6 mm diameter were no different from baseline at 6 months, however, were significantly thicker at the 1 year follow-up. Conclusion The data, in this study, points to a more uniform cornea post corneal collagen crosslinking. The inferior cornea becomes flatter and superior cornea steeper with less variation when comparing the corneal curvatures. The peripheral cornea becomes thicker at 1 year post-procedure. Collagen cross- linking stabilizes the cornea. How to cite this article Penner V, Muzychuk A, Al-Ghoul A, Rocha G. The Effects of Epithelium-off Corneal Collagen Crosslinking on Peripheral Corneal Keratometry, Pachymetry as well as Scheimpflug Imaging Calculated Corneal Indices in Keratoconus. Int J Kerat Ect Cor Dis 2014;3(3):113-117.

Intraocular lens power calculations using a Scheimpflug camera to measure corneal power

We measured corneal power using an Oculus Pentacam® to assess its accuracy for calculating intraocular lens (IOL) power after myopic refractive surgery. A series of corneal power measurements were performed on 22 patients (43 eyes) who had undergone myopic refractive surgery. In 37 of the 43 eyes, phacoemulsification and IOL implantation subsequently were performed. Conventional keratometry and three corneal measurements (mean true net power, central true net power, and 4.5 mm equivalent K reading) obtained using a Pentacam were analyzed and compared to values derived from the clinical history method. Prediction errors of three Pentacam corneal power measurements inserted in third generation IOL formulas also were compared. Analysis of the variance showed that only two Pentacam corneal measurements, mean true net power and central true net power, were not significantly different from those of the clinical history method. Mean true net power was correlated more closely with the clinical history method corneal power than other corneal power values. The one-sample t-test showed that of three Pentacam corneal measurements combined with third-generation formulas, only the mean true net power inserted in the SRK/T implant power calculation formula was not significantly different from zero. The percentages of eyes within ± 0.50 D and ± 1.00 D of the refractive prediction error of this method were 67.6% and 86.5%, respectively. Mean true net power inserted in the SRK/T formula can be used to calculate directly IOL power after myopic refractive surgery.

Clinical outcomes after intrastromal corneal ring segments reoperation in keratoconus patients.

To evaluate the clinical outcomes after Ferrara intrastromal corneal ring segments (ICRS) reoperation in patients with keratoconus. A total of 37 keratoconus eyes implanted with intrastromal corneal ring segments, which had an ICRS exchange, addition, reposition or removal were evaluated. Uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), keratometry (K), asphericity (Q) and pachymetry at the thinnest point (PTP) of the cornea were evaluated using a corneal tomography (Oculus Pentacam, USA). The mean follow-up time after the reoperation was 30.5±9.7 months. The mean UCVA improved from 20/300 to 20/80 (P=0.005); the mean BCVA improved from 20/160 to 20/50 (P=0.0002), the mean keratometry reduced from 49.33±4.19D to 46.16±3.90D (P=0.0001), the mean pachymetry at the thinnest point increased from 450±42.9μm to 469±40.8μm (P=0.0001). The asphericity increased from -0.84±0.74 to -0.35±0.81 (P=0.15) and the spherical equivalent reduced from -4.64±4.87D to -3.04±3.45D (P=0.137). The changes in the asphericity and spherical equivalent were not statistically significant. Ferrara ICRS implantation showed to be a reversible and readjustable surgical procedure for keratoconus treatment. Good outcomes can be obtained even after removal, addition, reposition or exchange of ICRS.

Correlation between Cataract Grading by Scheimpflug Imaging and Phaco Time in Phacoemulsification using Peristaltic and Venturi Pumps

To study the correlation among cataract grading system by Scheimpflug imaging (Oculus Pentacam® Nucleus Grading System [PNS]), effective phaco time (EPT), and surgical time (ST) using peristaltic and venturi pumps on the Whitestar Signature Phaco System (Abbott Medical Optics, Inc., Santa Ana, California, USA). Patients scheduled to have bimanual microincision phacoemulsification by the same surgeon (T.F.) had Pentacam® Scheimpflug assessment using PNS and were randomly distributed into 2 groups. In group 1, surgery was performed using peristaltic pump, and in group 2, using venturi pump. Parameters assessed in both groups included EPT and ST. Sixty eyes that had uneventful clear cornea phacoemulsification with implantation of foldable intraocular lens (IOL) were evaluated, 30 in each group. The EPT was statistically superior with higher nuclear density grades for both groups 1 and 2 (group 1 Spearman R = 0.739, p<0.001; group 2 Spearman R = 0.924, p<0.001). The ST statistically increased with nucleus density for both groups 1 and 2 (group 1 Spearman R = 0.620, p<0.001; group 2 Spearman R = 0.643, p<0.001). Group 2 presented statistically significant reduction on median ST compared with group 1 for nucleus grading 2, 3, 4, and 5. The PNS is an objective and reproducible method of grading nuclear cataract density and had a correlation with EPT. Peristaltic and venturi pumps in Signature Phaco System were similar in EPT but venturi pump reduced the median ST in nucleus with higher PNS, without repercussion on complications or anterior chamber stability.

Analysis of posterior capsule in after-cataract by oculus pentacam

Objective To investigate the accuracy of oculus pentacam in measuring posterior capsular thickness of after-cataract patients.Methods The study included experimental investigation and clinical observation.Thirty three rabbit eyes were made into after-cataract animal model successfully.The posterior capsular thicknesses were measured at 10 days,6 months and 12 months by oculus pentacam.The eyeballs were removed and posterior capsular thicknesses were detected by immunohistochemistry under light microscope at 10 days,6 months and 12 months.The results of the same time points were compared.In the clinical observation,52 eyes with after-cataract were enrolled and posterior capsular thicknesses were detected by oculus pentacam at 1 week,1 month,3 months and 12 months after cataract surgery.Results In animal experiment,the data of linear cross-sectional graph detected by oculus pentacam were compared with the results of light microscope examination and there was no significant difference between them.The linear crosssectional thicknesses of posterior capsule were not significantly different from the thicknesses tested under light microscope.The difference of individual credibility test was not statistically significant.In clinical observational study,posterior capsular thickness did not increase until 1 year after surgery.Conclusion Posterior capsular thickness of after-cataract detected by oculus pentacam is accurate,reliable,non-invasive and easy to operate,which provides objective data for the choice of clinical treatment. Key words: Cataract, after; Examination ; Oculus pentacam

Identification and localization of multiple intrastromal foreign bodies with anterior segment optical coherence tomography and ocular Pentacam

To report the clinical aspects and the imaging of a patient with intrastromal glass foreign bodies after a road traffic accident using both anterior segment optical coherence tomography (OCT) and ocular Pentacam. A detailed case report was made of the use of anterior segment OCT (AS-OCT) and ocular Pentacam to evaluate intrastromal foreign bodies. AS-OCT and Pentacam were valuable non-invasive tools in identification, localization and monitoring patients with intrastromal foreign bodies. This report demonstrates that AS-OCT and ocular Pentacam are effective and necessary procedures for both the diagnosis and follow-up of intracorneal foreign bodies.

Global and local contributions to surface curva- ture of healthy corneas

This paper demonstrates for several healthy eyes the application of a simple model to understanding local and global contributions to short-term variation in anterior and posterior corneal curvature. Multiple axial anterior and posterior corneal radii and central corneal thicknesses for the right eyes of 10 young subjects were determined over time using a rotating Scheimpflug camera (Oculus Pentacam). The axial radii were transformed to corneal powers, and also to curvatures that were referred to a mid-corneal surface such that local and global contributions to short-term variation could be analyzed quantitatively.When variation of the anterior and posterior corneal surfaces of several healthy eyes are studied in terms of curvatures (rather than powers) it is the posterior surfaces that are more variable withthe global or macroscopic rather than local effects dominating. (Harris and Gillan found the same for an eye with mild keratoconus.) This finding is opposite to that when variation is considered in terms of dioptric power where the anterior corneal surface usually appears more variable. Possible reasons for this finding includes firstly that the posterior corneal surface has to be measured through the air-tear interface and anterior corneal surface,and thus some uncertainty in measurements of the posterior surface may relate to this limitation. Secondly, no attempt was made here to mathematically align the multiple surfaces as determined per eye and thus we cannot be certain that precisely the same central corneal region was measured each time.Investigators need to carefully consider whether they are more interested in the optical or physical nature of variation in surfaces such as the cornea since studies of the optical effects require theanalysis to be performed in terms of dioptric powers and symmetric dioptric power space whereas studies of physical variation in the topography of the cornea and the possible reasons for such variability require the application of surface curvaturesin surface curvature space. This paper describes the application and significance of both methods to facilitate understanding of short-term variation of the human cornea. It does not, however, attempt to make any definite claims as to what factors (seeabove) may be major contributors to such variability, and this complicated but interesting research issue requires further clarification. (S Afr Optom 2012 71(4) 146-158)

Wie beeinflusst die zentrale Hornhautdicke den intraokularen Druck bei der Applanations- und Konturtonometrie?

Golmann applanation tonometry represents a well-established procedure for measuring intraocular pressure (IOP). This implies the necessity of an accurate measurement of IOP with the reference tonometer. One example is the contour tonometer Pascal with a measuring probe, adapted to the cornea geometry, for measuring the IOP and the ocular pulse amplitude. There is controversy of how strongly corneal thickness affects the measurement of IOP. We thus analysed, for a number of eyes, the correlation of IOP, as measured by two types of applanation tonometers and one contour tonometer and the central corneal thickness. In all 158 patient eyes were investigated in a clinical comparison of applanation tonometers AT 870 and Ocuton-A. The study was performed by a trained ophthalmologist and the comparison was in accordance with international standard ISO 8612. In addition, the corneal thickness in the vertex was repeatedly determined using an Oculus Pentacam. The potential effect of central corneal thickness on the IOP as measured by the mentioned tonometers was statistically evaluated by rank correlation analysis. We found that the measured IOP values for the three investigated tonometers were not normally distributed. The central corneal thickness values, in contrast, measured on 158 eyes by means of an ultrasound pachymeter and additionally on 235 eyes by the Pentacam, obeyed a Gaussian distribution. For the correlation analysis of both parameters the Spearman linear rank correlation coefficient (r) was considered. We found a very weak (|r| < 0.2) correlation between central corneal thickness and IOP for all 3 tonometers. The softness of the correlation is also illustrated by a large standard deviation of the regression line. A comparison of the different devices for corneal-thickness measurements shows less variance and a smaller variation coefficient when the ultrasoundpachymeter AL-1000 is used. The measured values for IOP are only very weakly correlated to the central corneal thickness. For the 3 tonometer types studied there is no need to correct the indicated pressure values according to the central corneal thickness of the investigated eye. Clinical comparisons according to the ISO 8612 standard between a tonometer under test and a reference Goldmann applanation tonometer are always a time-consuming procedure. Additional measures to determine the central corneal thickness of every investigated eyes are dispensable.

Evaluation of free-form IOL topographies by clinically available topographers

PurposeNo commercially available device for measuring individual IOL surface topographies exists on the market. The purpose of this paper is to show the applicability of clinically available corneal topographers for measuring individual IOLs consisting of a spherical surface on one side and a freeform surface on the other side. MethodsThree measurement principles (Placido rings: Tomey TMS-2N, Scheimpflug: Oculus Pentacam, optical coherence tomography: Tomey CASIA) are applied in determining the IOLs’ surface and compared against the design data used for producing the surfaces. Spherical and freeform IOLs are measured and analysed in both radius of curvature (ROC) and higher-order residual parameters by analysing the residuals. ResultsRepeatability and reproducibility measurements show a sub-μm precision for the TMS-2N system, while the Pentacam's values are located around 10μm and the CASIA system's values gather around 20μm. The TMS-2N system works best at detecting a sample's ROC and residual properties within the range of 8mm to 13.5mm mean ROC. In this range, the deviations from the theoretical ROC are about 45μm. The Pentacam doesn’t have this limitation, but faces problems with exporting measurements of freeform surfaces. In some circumstances the program crashes and prevents the export. If being able to export the Pentacam measurements show an average deviation of 100μm from the theoretical ROC value. The CASIA system shows high amounts of noise which makes it not applicable in this field, having deviations of several 100μm from the theoretical ROC value. Residual comparison for the higher-order samples shows sub-μm precision for the TMS-2N, about 1μm precision for the Pentacam and several μm for the CASIA system. The values for the customized samples are slightly increased, several μm for the TMS-2N, up to 30μm for the Pentacam system and around 75μm for the CASIA system. ConclusionThe TMS-2N system is an appropriate device for measuring individual IOL surface topographies for ROCs between 8mm to 13.5mm. The Pentacam and CASIA induced relatively high level of variation and noise. Future application of the TMS-2N in this field will reveal its long-term statistics.

Oculus Pentacam and Keratograph Integration in Advanced Refractive Procedures

Oculus Pentacam and Keratograph Integration in Advanced Refractive Procedures

Corneal topographic changes following trans-conjunctival 20 gauge sutureless vitrectomy (TC20V)

PurposeTo assess the occurrence and magnitude of corneal topographic changes in phakic eyes undergoing Transconjuctival Cannulated 20 gauge Vitrectomy (TC20V) without scleral buckling or silicone oil tamponade.SettingProspective randomized controlled study done at Egyptian Eye Academy.MethodsForty eyes of 40 patients underwent TC20V for a variety of vitreo-retinal conditions over a 1 year follow-up period. Corneal keratometric readings were obtained using Oculus Pentacam before surgery, 1 week after, and 1 month after surgery; neither scleral buckling nor silicone oil tamponade were used in order to not affect the final corneal changes. Cases with postoperative hypotony were excluded.ResultsThe mean preoperative K1 (vertical keratometry) was 44.87 ± 3.55, the mean preoperative K2 (horizontal keratometry) was 44.57 ± 3.68; the mean postoperative K1 after 1 week was 45.1 ± 6.82 while the mean postoperative K2 after 1 week was 45.7 ± 3.97. Using paired t-test analysis, the P-value of the K1 change was 0.01 and P-value of the K2 change was 0.02. Both indicate minimally significant differences. One month postoperative the mean K1 was 45.2 ± 2.53 and the mean K2 was 45.1 ± 1.56 and P-values of both K1 and K2 changes after 1 month were >0.05, which indicates insignificant changes.ConclusionThe results showed that minimal corneal topographic changes were encountered with the use of TC20V owing to the tunnel configuration of the wound, and these changes also decrease within the first month.

Evaluation of Ocular Biomechanical Indices to Distinguish Normal from Keratoconus Eyes

ABSTRACT Purpose To compare and assess the ability of pressure-derived parameters and corneal deformation waveform signal-derived parameters of the ocular response analyzer (ORA) measurement to distinguish between keratoconus and normal eyes, and to develop a combined parameter to optimize the diagnosis of keratoconus. Materials and methods One hundred and seventy-seven eyes (177 patients) with keratoconus (group KC) and 205 normal eyes (205 patients; group N) were included. One eye from each subject was randomly selected for analysis. Patients underwent a complete clinical eye examination, corneal topography (Humphrey ATLAS), tomography (Pentacam Oculus) and biomechanical evaluations (ORA Reichert). Differences in the distributions between the groups were assessed using the Mann- Whitney test. The receiver operating characteristic (ROC) curve was used to identify cutoff points that maximized sensitivity and specificity in discriminating keratoconus from normal corneas. Logistic regression was used to identify a combined linear model (Fisher 1.0). Results Significant differences in all studied parameters were detected (p &lt; 0.05), except for W2. For the corneal resistance factor (CRF): Area under the ROC curve (AUROC) 89.1%, sensitivity 81.36%, specificity 84.88%. For the p1area: AUROC 91.5%, sensitivity 87.1%, specificity 81.95%. Of the individual parameters, the highest predictive accuracy was for the Fisher 1.0, which represents the combination of all parameters (AUROC 95.5%, sensitivity 88.14%, specificity 93.17%). Conclusion Waveform-derived ORA parameters displayed greater accuracy than pressure-derived parameters for identifying keratoconus. Corneal hysteresis (CH) and CRF, a diagnostic linear model that combines different parameters, provided the greatest accuracy for differentiating keratoconus from normal corneas. How to cite this article Luz A, Fontes B, Ramos IC, Lopes B, Correia F, Schor P, Ambrósio R. Evaluation of Ocular Biomechanical Indices to Distinguish Normal from Keratoconus Eyes. Int J Kerat Ect Cor Dis 2012;1(3):145-150.

Optical transferences and their application to ray tracing through the human cornea*

The purpose of this paper is two fold, firstly to describe aspects of the quantitative analysis of the linear optical character of the corneas of ten young and healthy subjects using the exp-mean-log-transference and secondly to illustrate how mean transference and ray vector fields or diagrams can be used to explain and understand the optical properties of corneas as thick optical systems.An Oculus Pentacam was used to obtain 43 successive measurements of the radii of curvature of the anterior and posterior corneal surfaces and the central corneal thicknesses of the right eyes of ten subjects. From these measurements 4×4 ray transferences were calculated. Mean transferences were obtained via multi-dimensional Hamiltonian space and these mean transferences were used to produce stereo-pairs of ray vector fields. The mean transferences are also important in understanding the behaviour of light through each of the corneas concerned. This paper provides the first order optical characters of corneas from the positions and inclinations of rays entering and leaving such systems. As anticipated, light rays through the cornea are deflected inwards when the refractive index of the cornea is greater than the index of the surrounding medium. The exp-mean-log transference for a specific cornea exists and is the optical transference of the averaged cornea of the sample of measurements for that cornea. Within the limitations of linear or paraxial optics, the corneas of the different eyes in this sample and their averages were found to be close to that of thin optical systems; but they were not truly thin and instead should be considered as being thick optical systems. (S Afr Optom 2011 70(4) 156-167)

A Comprehensive Evaluation of the Precision (Repeatability and Reproducibility) of the Oculus Pentacam HR

To evaluate the precision (repeatability and reproducibility) of the Pentacam HR (high-resolution) tomographer (Oculus, Wetzlar, Germany) across a large range of measurement parameters. A randomly selected healthy eye of 100 subjects was scanned twice with the Pentacam HR by one observer for each of the three measurement modes: 25-picture (1 second) scan, 50-picture (2 second) scan, and cornea fine scan (50 pictures in 1 second). The repeatability of each scan mode was assessed. One additional 25-picture scan was acquired by a second observer to test reproducibility. Overall, the Pentacam HR had good precision, with the cornea fine scan returning the most precise results: The 25- and 50-picture scans showed similar precision. The repeatability limits, expressed as the within-subject SD × 1.96√2 of the anterior keratometry (K)1 and K2 readings with the standard 25-picture scan, were 0.25 and 0.36 D, respectively. Pachymetry maps, corneal maps, anterior chamber depth maps, corneal volume, topometric Q values and indices were also found to be precise. Poor precision was found for estimates of axis (astigmatic and progression index), pupil center pachymetry, single points on corneal maps, refractive power maps, and equivalent K readings. Measurements taken with the Pentacam HR are repeatable and reproducible, especially those obtained with the cornea fine scan. Although the Pentacam HR is clearly a very useful clinical and research tool, the measurement of corneal axes, pupil center pachymetry, front meridional and axial maps, refractive power maps, and equivalent K readings should be interpreted with caution.

Correlation of central and peripheral corneal thickness in healthy corneas

To study the thickness profile of the normal cornea in order to establish any correlation between central and peripheral points. Sixty-seven eyes of 40 patients were subjected to central corneal thickness measurement (CCT) with an ultrasound pachymeter (UP) and corneal thickness mapping with the Oculus Pentacam. The corneal apex thickness (CAT), pupil centre thickness (recorded as CCT and corresponded to CCT of UP) and thickness at the thinnest location (CTL) were obtained and compared with each other. Corneal thickness data at 3 mm and 7 mm temporally, nasally, superiorly and inferiorly from the corneal apex were obtained. The mean corneal thickness values along the 2, 4, 6, 8 and 10 mm diameter concentric circles, with the CTL as the centre, were also obtained. The above data at different points were statistically correlated. There was no significant difference between CCT readings measured by UP and Pentacam (P=0.721). There was high positive correlation between the CAT values and the thickness at 3 mm (R≥0.845, P<0.001) and at 7 mm points (R≥0.654, P<0.001). A gradual increase in thickness was noted from the centre to the periphery with a high positive correlation between the CTL values and the mean thickness at the circles of 2, 4, 6, 8 and 10 mm (R≥0.635, P<0.001). The results suggest that central corneal thickness can serve as a good guide for predicting peripheral thickness. For surgical procedures specifically undertaken at mid-peripheral and peripheral zones, the actual measurements at the site of surgery may confer some advantage.

Comparison of Oculus Pentacam and Stratus Optical Coherence Tomography for Measurement of Central Corneal Thickness

Measurement of central corneal thickness (CCT) plays an essential role in the diagnosis and treatment of many ocular diseases. In this study, we aimed to compare the CCT measurements obtained using the Scheimpflug system (Pentacam; Oculus, Inc) with a retinal optical coherence tomography device (Stratus OCT; Carl Zeiss Meditec, Inc) to examine healthy corneas. CCT measurements of 80 eyes belonging to 40 male patients (mean age: 24.48 ± 6.01 years) were evaluated with the Pentacam and the Stratus OCT. The relationship between the CCT values obtained with these 2 devices was examined with a Pearson correlation analysis, a paired t test, and a Bland-Altman analysis. The average CCT value obtained with Pentacam was 546.11 ± 34.15 μm and that obtained with Stratus OCT was 567.76 ± 35.02 μm. Although the average difference between the devices was 21.65 ± 8.59 μm (P < 0.0001), the measurements obtained with both devices were significantly correlated (r = 0.969, P < 0.0001). In Bland-Altman analysis, there was a high consistency between measurements obtained with either Pentacam or Stratus OCT devices. Corneal thickness measurements differ depending on the device used. Corneal thicknesses that have been calculated with Pentacam were lower than the values obtained with Stratus OCT. Both devices used for CCT measurement are easily applied, noninvasive, and effective. However, the devices are not interchangeable. Stratus OCT is not optimal for CCT measurement because of the important limitations of using manual measurements, but it can be used if other measurement devices designed for the purpose are not available.

Comparative analysis of the nuclear lens opalescence by the Lens Opacities Classification System III with nuclear density values provided by Oculus Pentacam: a cross-section study using Pentacam Nucleus Staging software

To compare the clinical classification of cataract using the Lens Opacities Classification System (LOCS) III with the mean values of lens density provided by the Pentacam Scheimpflug System in nuclear cataracts. One hundred and one eyes from 101 patients with age-related nuclear cataract were submitted to clinical examination for lens grading score using LOCS III. According to LOCS III, nuclear opalescence was divided in six groups. Patients were evaluated by the Pentacam Scheimpflug System for the mean lens density using the Pentacam lens densitometry program (PLDP), the Pentacam Nucleus Staging (PNS) mean value and the PNS cataract grading score. A positive correlation between the mean values of lens density and LOCS III classification, considering groups 1 to 5, could be noticed with PLDP and PNS mean value. The mean values between the groups were similar using the PLDP and the PNS mean value. However, when the PNS cataract grading score was evaluated, there was low correspondence with LOCS III classification. Pentacam Scheimpflug device offers an objective measure of the lens nuclear density on nuclear cataracts. PLDP and the PNS mean value were both useful to evaluate age-related nuclear cataract up to LOCS III group 5.