A comprehensive assessment of the precision and agreement of anterior corneal power measurements obtained using 8 different devices

The effect of systemic sclerosis and its subtypes on ocular anterior and posterior segment parameters

PURPOSE

To evaluate anterior and posterior segment parameters in the eyes of patients with systemic sclerosis (SSc) and examine the effect of disease and disease subtypes on these parameters.

METHODS

This cross-sectional study included 54 eyes of 27 SSc patients and 54 eyes of 27 age- and sex-matched healthy controls. In addition to a complete ophthalmologic examination, all patients were examined using a Scheimpflug camera, specular microscopy, and spectral domain optical coherence tomography.

RESULTS

The mean age of the patients was 52.5 ± 11.4 years and 19 patients were female. Anterior chamber volume, central corneal thickness, and central macular thickness (CMT) were significantly lower in the eyes of SSc patients compared to healthy controls (p = 0.01, p = 0.03, and p = 0.006, respectively). When evaluated according to SSc subtype, CMT was lower in diffuse SSc patients (p = 0.001), while mean retinal nerve fiber layer (RNFL) and inferior quadrant RNFL values were lower in limited SSc (p = 0.003 and p = 0.005, respectively).

CONCLUSION

In the eyes of patients with SSc, some ocular parameters may show decreases compared to healthy individuals, presumably secondary to disease-related vasculopathy and fibrosis. CMT and RNFL parameters may be affected differently according to disease subtype.

Comparison of keratometric values and anterior segment parameters measured using Scheimpflug Sirius topography and Lenstar biometry

PURPOSE

This study aimed to evaluate the consistency of preoperative keratometric values, anterior segment, and intraocular lens (IOL) power measurements in patients with cataract and no comorbidities using the Sirius topography device (CSO, Italy) and Lenstar LS 900 (Haag-Streit AG, Köeniz, Switzerland).

METHODS

Patients with grade 2 and 3 cataracts who applied to Ophthalmology Clinic of Dışkapı Yıldırım Beyazıt Education and Research Hospital, University of Health Sciences and planned for cataract surgery were included the study. Forty eyes with cataract from 40 patients were taken in the study. All patients underwent preoperative assessment using a combined Scheimpflug-Placido disc-based tomography device (Sirius) and Lenstar before cataract surgery. Keratometric measurements, such as flat keratometry (K1), steep keratometry (K2), and maximum keratometry (Kmax), and anterior segment parameters, white-to-white (WTW) distance, IOL power, astigmatism (AST), anterior chamber depth (ACD), aqueous depth (AD), and central cornea thickness (CCT), were recorded.

RESULTS

There were significant differences between K1Lenstar and K1Sirius, K2Lenstar and K2Sirius, KmaxLenstar and KmaxSirius, WTWLenstar and WTWSirius, and IOL powerLenstar versus IOL powerSirius. However, there were insignificant differences between ASTLenstar and ASTSirius, ACDLenstar versus ACDSirius, ADLenstar and ADSirius, and CCTLenstar and CCTSirius variables. Furthermore, it was found that Sirius measured significantly higher than Lenstar, especially in terms of IOL power.

CONCLUSION

Significant differences were observed between Lenstar and Sirius in terms of keratometric values, WTW distance, and IOL power. The IOL power value measured with Sirius was found to be higher than the IOL power value measured with Lenstar.

Comparing Repeatability and Agreement between Commonly Used Corneal Imaging Devices in Keratoconus

SIGNIFICANCE

Keratometry and pachymetry are important for diagnosis and monitoring of keratoconus. Many corneal imaging units exist, but comparison to determine repeatability and agreement is paramount for adequate keratoconus management in primary and secondary care.

PURPOSE

This study aimed to evaluate the repeatability and agreement of a Placido disc-based videokeratoscope (Melbourne, Victoria, Australia) used in primary care with spectral-domain optical coherence tomography (Optopol Technology, Zawiercie, Poland) and Scheimpflug corneal tomography (Oculus, Wetzlar, Germany) in secondary care.

METHODS

This was a prospective single-center study where one eye was randomized to have central corneal thickness;thinnest corneal thickness (TCT); and maximum, mean, steep, and flat keratometry (Kmax, Kmean, Ksteep, and Kflat, respectively), measured with all three devices. Three measurements were completed per device to assess intraobserver repeatability.

RESULTS

A total of 110 eyes from 110 patients with keratoconus were analyzed. Repeatability was best with the Pentacam for central corneal thickness, Kmax, Kmean, Ksteep, and Kflat parameters (precision, 9.21, 0.8, 0.38, 0.52, and 0.58). The Medmont had better repeatability than the Revo with Kmax, Kmean, Ksteep, and Kflat (precision, 1.41,1.35,1.43, and 1.59). Revo had the best repeatability with TCT (precision, 3.81). The intraclass correlation coefficient was >0.94 for all parameters in all devices. Agreement was generally poor between devices. However, there was good agreement between Pentacam and Medmont Kflat measurements ( P > .05).

CONCLUSIONS

Repeatability of keratometry parameters with the Pentacam and Medmont was greater than the Revo, suggesting a lower threshold for detecting change in anterior corneal parameters. The Revo had the greatest repeatability for TCT, suggesting a lower threshold for detecting thinning in disease progression and corneal-crosslinking safety. There was poor agreement between devices, and it is not recommended for them to be used interchangably.

Comparison of corneal measurements using two different Scheimpflug analyzers in Sirius and Pentacam devices

The aim was to compare measurements of anterior segment biometry parameters using two Scheimpflug tomographies, Pentacam and Sirius to assess the agreement. Prospective cross-sectional observational study. A total of 60 eyes of 30 healthy subjects were included and evaluated with Pentacam followed by Sirius imaging. Corneal indices were performed with two modalities in both eyes including; apical corneal thickness (ACT), corneal thickness at pupil site(PCT), thinnest corneal thickness (TCT), anterior chamber depth (ACD), chamber angle, chamber volume, cornea volume, mean front keratometry (FKm), the radius of corneal curvature at the anterior and posterior surface in steep and flat meridian, anterior astigmatism values, pupil diameter, and horizontal corneal diameter. The Bland-Altman graph and ICC (intra-class correlation were used to establish an agreement and present the similarity of the findings. Most parameters showed perfect agreement. In both devices, the ICC was more than 0.91 in all measurements except for ACD (ICC = 0.820), cylinder axis (ICC = 0.520), TCT(ICC = 0.881), ACT(ICC = 0.672), PCT (ICC = 0.882), chamber angle (ICC = 0.362), pupil diameter(ICC = 0.137). Pentacam yielded higher values that were significant in five parameters including 3.47 μm for TCT, 4.29 µm for PCT, 10.03 mm3 for chamber volume,2.67 mm3 for cornea volume, and 1.49 mm for pupil diameter but there was only a statistically significant difference in cornea volume and pupil diameter (p-value < 0.001). However, in Pentacam only the chamber angle value was 6.44 mm3 lower than Sirius, with a statistically significant difference (p-value < 0.001). Although these two devices had some statistically different results, it seems that they have a good agreement and correlation in most parameters.

Measuring the agreement of keratometry readings of four devices in eyes with keratoconus

PURPOSE

To determine the keratometry measurement agreement using Sirius corneal topography and Scheimpflug camera, Tomey corneal topography, Topcon autokeratorefractometer, and Tomey OA-2000 optical biometry in eyes with different severity of keratoconus.

METHODS

In this retrospective study 115 eyes in different stages of keratoconus were divided into 2 groups of mild (stage 1), and moderate to severe keratoconus (stages 2, 3), according to the Amsler-Krumeich classification. Keratometry measurements were obtained using Sirius corneal topography and Scheimpflug camera (phoenix V3.7.01.08), Tomey corneal topography (Tms SW22C-200S-200), Topcon autokeratorefractometer (KR8900), and Tomey optical biometry (OA-2000 Opt-Meas V.4E).

RESULTS

In group 1 All devices demonstrated fair agreement in average keratometry values (95% LoA range > 1 D). However, it was poorer for group 2 (95% LOA range > 3 D). In group 1 Bonferroni test revealed statistically significant difference in average K readings among (Topcon autokeratorefractometer 8900 and Tomey OA-2000 biometry, p < 0.01), and between (Tomey topography and Topcon autokeratorefractometer, p < 0.05). Also in group 2 significant difference was observed in the average keratometry of the most instruments (p < 0.01) except for the (Tomey topography and Topcon autokeratorefractometer) and (Tomey topography and Tomey OA-2000 biometry.

CONCLUSIONS

According to our investigation in mild, moderate and severe keratoconus the agreement in K reading between Topcon autokeratorefractometer, OA-2000 optical biometry, Sirius topography and Tomey topography was poor. The agreement declines especially in the steep meridian and it was not acceptable clinically. These devices should not be applied interchangeably.

Comparison of Corneal Power Difference Maps with Achieved Myopic Correction Using Scheimpflug Tomography After LASIK, PRK, and SMILE

Purpose

To compare corneal power difference maps (∆maps) obtained from the Pentacam in patients with 1 year follow-up after LASIK, PRK, and SMILE with further stratification to low, moderate, and high myopia.

Patients and methods

This retrospective study was comprised of patients who had preoperative and 1-year postoperative power maps that were obtained-front sagittal (SagF), refractive power (RP), true net power (TNP), and total corneal refractive power (TCRP)-for evaluation. Measurements were recorded and compared at the 4mm, 5mm and 6mm pupil and apex zones. Comparisons were made between each specific power ∆map and the surgically induced refractive change (SIRC). Further analysis of the ∆maps was performed based on degree of myopia (high, moderate, and low). Correlation and agreement were also assessed with regression and limits of agreement (LoA).

Results

There were 172 eyes in the LASIK group, 187 eyes in the PRK group, and 46 eyes in the SMILE group. In the LASIK group, TNP ∆map at 5mm pupil zone had the least absolute mean difference with SIRC (0.007 ± 0.42D). In the PRK group, TNP ∆map at 5mm apex zone was most accurate compared to SIRC (0.066 ± 0.45D). In the SMILE group, TCRP ∆map at 4mm apex zone had the closest absolute value when compared to SIRC (0.011 ± 0.50D). There was good correlation and agreement for all three surgery groups, LASIK: r = 0.975, LoA -0.83D to +0.83D, PRK: r = 0.96, LoA -0.83D and +0.95D, and SMILE: r = 0.922, LoA -0.97 D to +0.99D.

Conclusion

TNP ∆maps most accurately measured corneal power in the LASIK and PRK groups while TCRP ∆maps were most accurate in the SMILE group. The degree of myopia may change which ∆map is most accurate.

Optic disc and retinal vessel densities assessment by optical coherence tomography angiography in patients with keratoconus

BACKGROUND

This study aimed to evaluate retinal and optic disc vascular changes in patients with keratoconus (KC) using optical coherence tomography angiography (OCTA).

METHODS

Thirty-two eyes of 22 patients with KC and 24 eyes of 24 age- and sex-matched healthy controls were included in this study. Corneal topography and OCTA were performed. Quantitative vessel density of the macular superficial capillary plexus (SCP), macular deep capillary plexus (DCP), and radial peripapillary capillaries (RPC); choriocapillaris flow area; and choroidal thickness were compared between the KC and control groups.

RESULTS

SCP and DCP vessel densities showed a significant reduction in the KC group compared to that in the control group (p < 0.001 and p < 0.001 in the whole image and parafovea, respectively). Choriocapillaris flow area was significantly higher in patients with KC than in the control group (p = 0.003). The foveal avascular zone area did not significantly differ between the two groups (p = 0.949). RPC inside disc vessel density was significantly decreased in the KC group compared to that in the control group (p < 0.001).

CONCLUSION

This study revealed important macular, choroidal, and optic disc vessel densities changes in patients with KC. Macular whole vessel density and parafoveal vessel density of the SCP and DCP decreased, while choriocapillaris flow area increased in patients with KC.

Comparison of Total Corneal Astigmatism between IOLMaster and Pentacam

Purpose. To compare the total corneal astigmatism (TCA) measured by IOLMaster 700 and Pentacam and to investigate the consistency of corneal keratometry (CK) measured by IOLMaster and Pentacam. Methods. Cataract patients were retrospectively enrolled in March and April, 2021. Retrospective analysis was performed on those patients with binocular and monocular CK measured by IOLMaster and Pentacam. Results. A total of 102 patients (204 eyes) were included, 64 of whom were female (62.75%). The flat (K1) and steep (K2) CK of anterior corneal surface (ACS) and flat (TK1) and steep (TK2) of total cornea measured with IOLMaster 700 were $44.16\pm 1.60\text{D}$ , $45.09\pm 1.68\text{D}$ , $44.12\pm 1.62\text{D}$ , and $45.14\pm 1.69\text{D}$ , respectively. Those measured with Pentacam were $44.31\pm 1.57\text{D}$ , $45.22\pm 1.65\text{D}$ , $44.15\pm 1.67\text{D}$ , and $45.19\pm 1.82\text{D}$ , respectively. The astigmatism of ACS and TCA were $-0.94\pm 0.63\text{D}$ and $-1.02\pm 0.69\text{D}$ ( $p<0.01$ ) in the IOLMaster group and $-0.90\pm 0.59\text{D}$ and $-1.05\pm 0.81\text{D}$ in the Pentacam group, respectively ( $p<0.01$ ). TCA measurement results of IOLMaster and Pentacam were consistent ( $\text{Pearson}=0.710$ , $p<0.01$ ), and there was no significant difference ( $p=0.591$ ). Conclusions. Total corneal astigmatism measured by IOLMaster was consistent with that measured by Pentacam. The difference between the astigmatism of anterior corneal surface and total cornea was detected in the measurement of IOLMaster and Pentacam, respectively.

Comparison of Anterior Segment Measurements with a New Multifunctional Unit and Five Other Devices

Purpose

To evaluate the clinical availability of a multifunctional ocular biometric unit, MR-6000, for simultaneous keratometry, tonometry, topography, and pachymetry evaluation, and compare anterior segment measurements with five other devices: autokeratometer (KR-1), Scheimpflug camera (Pentacam HR), swept-source optical coherence tomography (IOLMaster 700), Placido disk scanning-slit topography (Orbscan II), and noncontact tonometry (FT-1000).

Methods

Thirty eyes from thirty patients who visited Severance Hospital for cataract surgery were examined using MR-6000 and the other devices. The mean keratometry, central corneal thickness (CCT), white-to-white (WTW) distance, and intraocular pressure (IOP) values were compared. Repeated measures analysis of variance, Wilcoxon signed-rank test, intraclass correlation coefficient (ICC), and Bland-Altman plot were used to assess the correlation and agreement between devices.

Results

Thirty eyes of thirty patients were evaluated. Statistically significant differences in mean keratometry between MR-6000, KR-1, Pentacam HR, and IOLMaster 700 were not observed (p > 0.05). All five devices, including Orbscan II, had almost perfect agreement in measuring keratometry (ICC > 0.80, p < 0.05). CCT measured by MR-6000 was significantly different from that of Pentacam HR and Orbscan II measurements (p < 0.05) but correlated with that of Pentacam HR and Orbscan II measurements (ICC > 0.60, p < 0.05). The WTW distance measured by MR-6000 was not significantly different from that measured by IOLMaster 700 but was different from that measured by Orbscan II. IOP measured by MR-6000 was not correlated with FT-1000.

Conclusions

Keratometric values obtained through MR-6000 can be used interchangeably with other devices based on good correlation and agreement. However, the CCT, WTW, and IOP values were not interchangeable with a single multifunctional unit for cataract surgery preoperative examination.

Manual and software-based measurements of treatment zone parameters and characteristics in children with slow and fast axial elongation in orthokeratology

PURPOSE

To compare the treatment zone (TZ) measurements obtained using manual and software-based methods in orthokeratology (ortho-k) subjects and explore the TZ characteristics of children with slow and fast axial elongation after ortho-k.

METHODS

Data from 69 subjects (aged 7 to <13 years old), who participated in three 24-month longitudinal orthokeratology studies, showing fast (>0.27 mm, n = 38) and slow (<0.09 mm, n = 31) axial elongation, were retrieved. The TZ after ortho-k was defined as the central flattened area enclosed by points with no refractive power change. TZ parameters, including decentration, size, width of the peripheral steepened zone (PSZ), central and peripheral refractive power changes and peripheral rate of power change, were determined manually and using python-based software. TZ parameters were compared between measurement methods and between groups.

RESULTS

Almost all TZ parameters measured manually and with the aid of software were significantly different (p < 0.05). Differences in decentration, size and the PSZ width were not clinically significant, but differences (0.45 to 0.92 D) in refractive power change in the PSZ were significant, although intraclass coefficients (0.95 to 0.98) indicated excellent agreement between methods. Significantly greater TZ decentration, smaller TZ size and greater inferior rate of power change (relative to the TZ centre) were observed in slow progressors using both methods, suggesting a potential role of TZ in regulating myopia progression in ortho-k.

CONCLUSION

TZ measurements using manual and software-based methods differed significantly and cannot be used interchangeably. The combination of TZ decentration, TZ size and peripheral rate of power change may affect myopia control effect in ortho-k.

Correlation between Placido's Disk and Rotating Scheimpflug Keratometric Findings in Children with Keratoconus before and after Corneal Cross-Linking

PURPOSE

Evaluate correlation between Placido's disk and rotating Scheimpflug keratometric findings in children with progressive keratoconus (KC) before and after corneal cross-linking (CXL) and investigate whether these limits of agreement varied according to disease severity.

SETTING

Department of Ophthalmology of São Paulo Hospital, São Paulo, Brazil.

DESIGN

Prospective nonrandomized open study.

METHODS

Data obtained using rotating Scheimpflug-based tomography and Placido-based topography devices were collected from preoperative and last follow-up postoperative children with KC operated on using standard CXL protocol. Correlation and agreement analyses were performed between the two devices before and after CXL to obtain keratometric findings.

RESULTS

Forty-four eyes from 44 patients 8 to 16 years of age were analyzed at all time points. All parameters were found to be strongly correlated before (r = 0.84-0.99, p < 0.001) and after (r = 0.93-0.99, p < 0.001) CXL. Mean Scheimpflug measurements of flat K, steep K, Kmax, mean K, and corneal astigmatism were higher than Placido measurements in preoperative period. This mean difference decreased in postoperative, but, with exception of Kmax and corneal astigmatism, Scheimpflug measurements remained higher. Mean parameter measurements from both devices decreased after CXL. 95% limits of agreement between instruments were wide for all parameters, and decreased in postoperative and in mild KC.

CONCLUSION

Keratometry measurements obtained using rotating Scheimpflug and Placido disk technology were found to be closely correlated but not interchangeable before and after CXL in pediatric patients. Agreement between devices was better after CXL and in mild KC than in advanced KC.

Agreement of Anterior Segment Parameters Between Schiempflug Topography and Swept-Source Optic Coherence Based Optic Biometry in Keratoconus and Healthy Subjects

PURPOSE

The aim of this study is to compare anterior segment parameters, including corneal thickness (CCT), keratometry and anterior chamber depth (ACD), and white to white corneal diameter (WTW), obtained by Pentacam Schiempflug imaging and intraocular lens (IOL) Master 700 swept-source optic coherence tomography biometry in keratoconus patients and healthy subjects.

METHODS

This prospective cross-sectional instrument agreement analysis includes 88 eyes of 50 keratoconus patients and 87 eyes of 50 healthy subjects. Biometry was performed using IOL Master 700, and topography was performed using Pentacam. The keratometry values (Kf, Ks, Km, and Kmax), ACD, WTW, CCT, axial length (AL), anterior chamber angle (ACA), and lens thickness (LT) were evaluated. Levels of agreement between devices were evaluated by Bland-Altman plots with 95% limits of agreement.

RESULTS

Intraocular lens Master 700 showed higher WTW, ACD, pupil diameter, and CCT values than Pentacam in both the keratoconus and control groups. However, there were no statistically significant differences in flat keratometry (Kf) and steep keratometry (Ks) values between the groups.

CONCLUSION

Pentacam and IOL Master 700 may be used interchangeably in normal eyes and keratoconus eyes for the measurement of keratometry values and axis; however, these two devices should not be considered interchangeable for WTW, ACD, pupil diameter, and CCT measurements in both keratoconus patients and healthy subjects.

Inter-device measurement variability of vital data parameters for keratorefractive and cataract refractive surgery

Introduction:

The measurements of corneal white-to-white (WTW) diameter and pupil size are critical for decision making in refractive surgery. Currently, automatic measurement of keratometry, corneal WTW, and pupil size are implemented in several ocular devices. The purpose of this study was to examine the agreement between two commonly used devices, an autorefractor and an optical biometer, for these parameters.

Methods:

Measurements were performed with both a Lenstar LS-900 and Nidek ARK-1 by an experienced examiner in random order. The devices were placed in close proximity within the same dimly lit room.

Results:

The measurements of 65 right eyes were analyzed. The results of the flat, steep, and mean keratometric reading were not significantly different (p = 0.96, p = 0.90, p = 0.93, respectively). Corneal WTW distances showed only moderate agreement between devices and were found to be significantly different (r = 0.8071; p < 0.01). Pupil diameters showed poor agreement between devices and were significantly different (r = 0.4890; p < 0.01). Agreement between implantable contact lens sizing, based on the measurements obtained by the two devices, was achieved for 19 of the 51 eyes (37.3%).

Conclusion:

We found a significant difference in WTW and pupil size measurements between ARK-1 and Lenstar. Results for both of the devices cannot be considered interchangeable for these data parameters.

Comparison of keratometry data using handheld and table-mounted instruments in healthy adults

PURPOSE

To compare keratometry data between the handheld Retinomax K-plus 3 and the table-mounted IOLMaster 700.

METHODS

Healthy adult volunteers were prospectively recruited to the study. All participants underwent 3 consecutive keratometry measurements using the Retinomax K-plus 3 and a single biometry assessment using the IOLMaster 700. Differences between the Retinomax K-plus 3 and the IOLMaster 700 were assessed using Wilcoxon test for paired samples, Spearman correlation, Bland-Altman and mountain plots.

RESULT

Twenty-eight healthy subjects with a median age of 37 years (interquartile range (IQR) 28-44 years) were included in the study. The median mean keratometry (mean K) reading was higher using the Retinomax K-plus 3 (44.04D; IQR 42.96-45.61D) compared to the IOLMaster 700 (43.78D; IQR 43.22-44.90D, p < 0.01), with a mean difference of 0.18D (95% confidence interval (CI) 0.11-0.23D). Mean K readings were highly correlated between the 2 devices (r = 0.995, p < 0.01). Bland-Altman plots showed 95% limits of agreement between -0.14D and 0.49D. Frequency histogram of mean K reading differences between the Retinomax K-plus 3 and the IOLMaster 700 showed that 56% of cases were between ± 0.2D, 93% of cases were between ± 0.4D and all cases were between ± 0.5D. Mean corneal astigmatism measurement was higher using the Retinomax K-plus 3 (1.01 ± 0.40D) compared to the IOLMaster 700 (0.77 ± 0.36D), with a mean difference of 0.23 ± 0.37D (p < 0.01) between the devices.

CONCLUSIONS

A good agreement exists between the Retinomax K-plus 3 and the IOLMaster 700 regarding keratometry readings. This enables cataract surgeons to safely use the Retinomax K-plus 3 device when indicated.

Agreement Between Two Optical Biometers Based on Large Coherence Length SS-OCT and Scheimpflug Imaging/Partial Coherence Interferometry

PURPOSE

To evaluate the agreement between measurements obtained with a new optical biometer (Argos; Movu Inc) using large coherence length swept-source optical coherence tomography (SS-OCT) and those obtained with an optical biometer with a rotating Scheimpflug camera, combined with partial coherence interferometry (PCI) (Pentacam AXL; Oculus Optikgeräte GmbH) in adults.

METHODS

The following measurements were examined and evaluated: axial length, central corneal thickness (CCT), anterior chamber depth (ACD), mean keratometry, J₀ and J₄₅ vectors, and corneal diameter. Measurements with the two biometers were conducted in triplicate per instrument in a random order by the same examiner. Paired t tests were employed to compare the difference between the two devices. The Bland-Altman method was implemented to assess their agreement.

RESULTS

A total of 145 patients were enrolled in the study. The differences between the Scheimpflug/PCI-based biometer and the SS-OCT biometer were as follows: -0.02 ± 0.05 mm for axial length, 1.15 ± 5.79 µm for CCT, -0.04 ± 0.04 mm for ACD, -0.28 ± 0.16 diopters (D) for mean keratometry, 0.01 ± 0.11 D for J₀, -0.02 ± 0.10 D for J₄₅, and -1.03 ± 0.62 mm for corneal diameter. Bland-Altman plots showed narrow ranges in axial length, CCT, ACD, mean keratometry, and J₀ and J₄₅, which implied excellent agreement between the two biometers. Corneal diameter displayed poor agreement, with a 95% limits of agreement ranging from -2.25 to 0.19 mm.

CONCLUSIONS

Excellent agreement was established between the measurements provided by the new optical biometer based on SS-OCT and the optical biometer using Scheimpflug imaging and PCI, except for corneal diameter. [J Refract Surg. 2020;36(7):459-465.].

A Comparative Study of Corneal Topography in Children with Autism Spectrum Disorder: A Cross-Sectional Study

Purpose: To investigate the corneal characteristics in individuals with autism spectrum disorder (ASD) and age-matched typical development (TD) participants. Methods: This cross-sectional, clinically based study compared children with ASD to age-matched TD participants. Corneal topography was measured with a portable EyeSys Vista system. The distance visual acuity (VA) and the contrast sensitivity (CS) were determined. The refractive error (RE) was assessed using a 2WIN autorefractometer. Results: A total of 31 children with ASD (mean age: 12.78 ± 4.49 years), and 60 participants with TD (mean age: 13.65 ± 3.56 years) were recruited. The two groups were similar in age (t = −2.084, p = 0.075) and VA (t = −0.35, p = 0.32). Most of the children with ASD had a significant amount of refractive errors (REs; range: +5.25 to −5.50 DS), and astigmatism was dominant (range: −0.25 to −4.50 DC). There was no statistically significant difference between both groups in terms of average corneal power (t = 1.12, p = 0.39). The children with ASD and participants with TD also did not differ significantly in terms of corneal shape descriptors (p > 0.05), such as corneal asphericity, inferior superior index, opposite sector index, and differential sector index. The spherical equivalent did not differ significantly between the ASD participants and participants with TD (t = 1.15, p = 0.15). There was a significant difference (p < 0.05) in the astigmatism component between the ASD participants and the participants with TD.

The effect of glaucoma treatment using high-intensity focused ultrasound on total and corneal astigmatism: a prospective multicentre study

PURPOSE

Ultrasound cycloplasty (UCP) acts through the selective coagulation of the ciliary body using high-intensity focused ultrasound (HIFU) technology. The aim of this study was to investigate whether the application of ultrasound beams targeting the ciliary body using an external probe influences astigmatism.

METHODS

Multicentre, prospective, single-arm, open-label study in adult patients with primary open-angle glaucoma and moderately uncontrolled intraocular pressure (IOP) under glaucoma medication. The primary outcome was induced corneal astigmatism, calculated from topography, and assessed statistically through vector analysis. Secondary outcomes included induced total astigmatism and mean changes from baseline in best-corrected visual acuity (logMAR) and IOP. Subgroup analysis was performed to assess the impact of device centring on corneal and total induced astigmatism.

RESULTS

Fifty eyes were enrolled. Mean age was 69.6 ± 11.3 years. At 1, 3 and 6 months postprocedure, HIFU-induced corneal astigmatism was 0.88 D × 93°, 0.87 D × 106° and 1.16 D × 97°, respectively, while induced total astigmatism was 0.62 D × 103°, 0.42 × 106° and 0.39 × 107°. By the last follow-up, the percentage of patients with <0.50, <1.00, <1.50 and <2.00 D of induced corneal versus total astigmatism was 8.3% versus 46%, 29% versus 66%, 62.5% versus 88% and 79% versus 94%. Visual acuity was statistically significantly impaired at 1 month, but no difference remained by 3 and 6 months postprocedure.

CONCLUSION

Ultrasound cycloplasty procedure is associated with increased corneal astigmatism. However, its impact on total refractive astigmatism is less pronounced.

A Comparative Study of Total Corneal Power Using a Ray Tracing Method Obtained from 3 Different Scheimpflug Camera Devices

PURPOSE

We sought to assess the agreement of ray-traced corneal power values by 3 Scheimpflug tomographers tp construct the corresponding arithmetic adjustment factor in comparison with an automated keratometer (IOLMaster) and a conventional Placido-based topographer (Allegro Topolyzer).

DESIGN

Prospective reliability analysis.

METHODS

A total of 74 eyes from 74 healthy subjects who underwent corneal power measurements using Pentacam, Sirius, Galilei, IOLMaster, and Allegro Topolyzer were included. Ray-traced corneal power values, such as total corneal refractive power (TCRP), mean pupil power (MPP), total corneal power (TCP), mean keratometry (Km), and simulated keratometry (SimK) were recorded respectively and analyzed using one-way analysis of variance (ANOVA) and Bland-Altman plots.

RESULTS

Among the 3 ray-traced corneal power values, TCRP and MPP did not differ significantly (P = 0.81), whereas TCP presented a slightly significant larger value (P < 0.001). Compared to Km or SimK, corneal power measurements by the ray tracing method exhibited significantly lower values (P < 0.001). Bland-Altman plots disclosed that the 3 Scheimpflug tomographers showed similar 95% limits of agreement after arithmetic adjustment compared with Km (-0.40 to 0.40 D, -0.39 to 0.39 D, and -0.35 to 0.34 D) or SimK (-0.50 to 0.51 D, -0.43 to 0.42 D, and -0.46 to 0.46 D).

CONCLUSIONS

Ray-traced corneal power values obtained using 3 Scheimpflug tomographers with default diameter settings were similar, indicating that they could be used interchangeably in daily clinical practice. The 3 Scheimpflug tomographers were satisfactory in agreement after arithmetical adjustment compared with conventional automated keratometer or Placido-based topographer.

Repeatability of whole-cornea measurements using a new swept-source optical coherence tomographer

PURPOSE

The aim of this study was to evaluate the repeatability of several corneal parameters provided by a high-resolution swept-source optical coherence tomographer (SS-OCT).

METHODS

One eye from each of 74 patients was measured five times consequently using the ANTERION SS-OCT. The following corneal parameters were analyzed: average, steep and flat keratometry (K), astigmatism for anterior, posterior and total at 3-mm, average K and astigmatism at 6-mm, anterior and posterior eccentricity, higher-order aberrations (HOA) and spherical aberration (Z40), and anterior and posterior best-fit sphere at 8-mm. The intrasubject standard deviation (S_w), coefficient of variation (CoV), coefficient of repeatability (CoR) and intraclass correlation coefficient (ICC) were calculated for each parameter to assess the repeatability.

RESULTS

We have not found statistically significant differences between repeated measurements (p > 0.05). Repeatability was good considering the different metrics used. S_w values were <0.09, varying from 0.035 (posterior average K at 6-mm) to 0.0878 (anterior flat K at 3-mm). CoV values were also low and similar among the different parameters (from 0.08% to 0.21%), except for anterior, posterior and total astigmatism (from 2.25% to 8.46%). Both anterior and posterior eccentricity, and corneal aberrations (HOA and Z40) CoV values were also high. The CoR values were low for all parameters showing those related to the posterior cornea the lowest values (about 0.01). ICC values were >0.98.

CONCLUSIONS

The ANTERION SS-OCT showed good repeatability when reconstructed different parameters for the whole cornea. This device produces measurements with high repeatability that could be useful for clinical research.

Prevalence of Subclinical Keratoconus Among Pediatric Egyptian Population with Astigmatism

Purpose

To report the prevalence of subclinical keratoconus (KC), and KC suspects, in pediatric Egyptian population with astigmatic error ≥2 diopters (D), with the use of CSO Sirius tomographer.

Methods

A cross-sectional study that included all the children aged 6–18 years with an astigmatic error of ≥2 D who attended the pediatric ophthalmology clinic for routine checkups during the period between March 2017 and December 2017 was done. All subjects underwent comprehensive ophthalmic examination, and corneal imaging using CSO Sirius instrument, a pentacam with Scheimpflug technology.

Results

There were 547 subjects enrolled in our study. Mean age was 11.34 ± 3.03 (range 6–18) years. There were 278 subjects (50.8%) between 6 and 12 years, and 269 subjects (49.2%) between 12 and 18 years. Males represented 48.4% and females represented 51.6% of patients. Among all the subjects, there were 26 (4.8%) KC patients, 24 (4.4%) KC suspects, and 497 (90.9%) were normal.

Conclusion

Prevalence of subclinical KC among pediatric age group with astigmatism is relatively high, hence the importance of corneal tomography screening of children with astigmatic error ≥2 D.

Comparison of Multicolored Spot Reflection Topographer and Scheimpflug-Placido System in Corneal Power and Astigmatism Measurements With Normal and Post-refractive Patients

PURPOSE

To evaluate the repeatability of corneal power and astigmatism derived by a novel multicolored spot reflection topographer system (Cassini; i-Optics, Hague, Netherlands) and compare its agreement with a Placido-Scheimpflug system (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy) in normal and post-refractive patients.

METHODS

This prospective study comprised patients who underwent myopic excimer laser refractive surgery (96 eyes) and normal patients (102 eyes). Each patient was measured three times with the Cassini and Sirius. The simulated keratometry (SimK), total corneal power (TCP), and astigmatism were recorded. The repeatability was assessed by one-way analysis of variance. The paired t test was used to compare the differences, whereas the agreement was evaluated by Bland-Altman analysis.

RESULTS

All parameters obtained by the Cassini demonstrated high repeatability, except for total corneal astigmatism (TCA) in the post-refractive group. The intraclass correlation coefficients of all parameters were greater than 0.85, the correlation of variation values was less than 0.55%, and the test-retest repeatability was less than 0.85 diopters (D). The paired t test showed significant differences in steep keratometry, astigmatism, TCP, and TCA in the normal group and in J₀, TCP, and TCA in the post-refractive group. The 95% limits of agreement (LoA) in the normal group demonstrated good agreement, except for TCP. Only J₀ and J₄₅ of astigmatism and TCA remained narrow for 95% LoA in the post-refractive group.

CONCLUSIONS

These results suggested that the Cassini provided high repeatable measurements in corneal power and astigmatism, except the TCA of post-refractive patients. The parameters could be used interchangeably in normal patients, except for TCP, whereas only J₀ of astigmatism and J₀, J₄₅ of TCA showed good agreement in post-refractive patients. [J Refract Surg. 2019;35(6):370-376.].

Interchangeability of corneal curvature and asphericity measurements provided by three different devices

AIM

To evaluate the interchangeability of keratometric and asphericity measurements provided by three measurement systems based on different optical principles.

METHODS

A total of 40 eyes of 40 patients with a mean age of 34.1y were included. In all cases, a corneal curvature analysis was performed with IOL-Master (IOLM), iDesign 2 (ID2), and Sirius systems (SIR). Differences between instruments for flattest (K1) and steepest (K2) keratometric readings, as well as for magnitude and axis of corneal astigmatism were analyzed. Likewise, differences in asphericity (Q) between SIR and ID2 were also evaluated.

RESULTS

Mean differences between devices for K1 were 0.20±0.21 (P<0.001), -0.12±0.36 (P=0.046) and -0.32±0.36 D (P<0.001) for the comparisons IOLM-SIR, IOLM-ID2 and SIR-ID2, respectively. The ranges of agreement for these comparisons between instruments were 0.41, 0.70, and 0.70 D. For K2, mean differences were 0.31±0.33 (P<0.001), -0.08±0.43 (P=0.265) and -0.39±0.38 D (P<0.001), with ranges of agreement of 0.65, 0.84, and 0.74 D. Concerning magnitude of astigmatism, ranges of agreement were in the limit of clinical relevance (0.49 D, P=0.011; 0.55 D, P=0.386; 0.43 D, P=0.05). In contrast, ranges of agreement were clinically relevant for astigmatic axis (26.68°, 33.83° and 18.37°, P≥0.121) and for Q between SIR and ID2 (0.16, P<0.001).

CONCLUSION

The keratometric corneal power, astigmatic axis and asphericity measurements provide by the three systems evaluated cannot be considered as interchangeable, whereas measurements of corneal astigmatism obtained with SIR and ID2 can be considered as interchangeable for clinical purposes.

Comparison of Toric and Spherical Orthokeratology Lenses in Patients with Astigmatism

Purpose

This retrospective study aimed at comparing the efficacy and safety of toric and spherical orthokeratology lenses in the treatment of patients with moderate to high astigmatism.

Methods

Fifty adolescents with myopia and moderate to high astigmatism (≥1.50 D) who underwent consecutive orthokeratology treatment for at least 1 year were included in this study. The toric group comprised 25 subjects (25 eyes, 11 M, 14 F; age, 10.67 ± 1.46 years) who were fitted with toric orthokeratology lenses. The spherical group comprised 25 subjects (25 subjects, 11 M, 14 F; age, 11.45 ± 1.63 years) who were fitted with traditional spherical orthokeratology lenses as a control. Corneal topography, visual acuity, axial length, and slit-lamp examinations were performed to determine the differences between these two groups. The corneal tangential difference mapping was conducted between baseline and every subsequent visit to calculate the magnitude of lens decentration. The corrective effect of ortho-K lens was measured by using the corneal axial difference map.

Results

The mean decentration and its vertical vector were significantly less in the toric group than in the spherical group after 1 month of lens wear. In toric group, the corneal astigmatism decreased from 1.85 ± 0.31 D at baseline to 1.45 ± 0.85 D after the first month of wear. There was a significant linear correlation between the change in corneal astigmatism and lens decentration in the toric group from 1 month to 1 year (Y = 3.268 ∗ X + 0.9182, R ² = 0.5035, p < 0.0001 (X: lens decentration; Y: astigmatic changes)). There were no significant differences in the post-OK uncorrected visual acuity, myopia control, or ocular health between the toric and spherical groups.

Conclusion

The toric orthokeratology lens design can effectively reduce the lens decentration magnitude and CJ180 from 1-month visit to 12-month visit of patients with high or moderate corneal astigmatism. Meanwhile, there was no significant difference in visual acuity, myopia control, and ocular health throughout 12 months. However, the effect of toric lenses on corneal morphology may be susceptible to lens positioning.

Intrasession Repeatability and Intersession Reproducibility Measurements Using VX120 Multidiagnostic Unit

OBJECTIVE

The VX120 multidiagnostic unit is a multidiagnostic instrument that combines several functions: autorefraction, keratometry, corneal topography, aberrometry, pachymetry, and noncontact tonometry. The purpose of this study was to determine the intrasession repeatability and the intersession reproducibility of all parameters measured by the VX120 multidiagnostic unit in a sample of normal healthy eyes.

METHODS

Three repeated measurements in the right eye of the volunteers were taken with VX120. Repeatability of the sphere, cylinder, axis, anterior corneal powers (K flat and K steep, 3-mm pupil), high- and low-order aberration root mean square (HOA-RMS and LOA-RMS, 3-mm pupil), eccentricity, white-to-white (WTW), anterior chamber depth (ACD), and central corneal thickness (CCT) (2-mm central) was analyzed. Within-subject SD (Sw), precision, repeatability, coefficient of variation (CV), and the intraclass correlation coefficient (ICC) were calculated.

RESULTS

The CV was low for K flat and K steep, WTW, ACD, and CCT with a range from 0.34% to 1.16%. The CV was higher for sphere, cylinder, HOA-RMS, and LOA-RMS and eccentricity with a range among 6.92% to 54.24%. The ICC showed high values in all parameters except in HOA-RMS (0.720-0.776) and eccentricity (0.889) in first session with moderate agreement. Comparing the intrasession repeatability of first and second session, statistically significant differences (P<0.01) were found between both sessions just to the CV for all parameters (except cylinder values) measured with VX120. However, nonstatistically significant differences (P>0.13) were found for Sw, precision, and repeatability values.

CONCLUSIONS

The VX120 multidiagnostic unit provides repeatable measurements in anterior corneal power (K flat and K steep), WTW, ACD, and CCT. However sphere, cylinder, HOA-RMS, LOA-RMS, and eccentricity showed worse repeatability. Intersession reproducibility showed good results with little differences between sessions in healthy subjects.

Repeatability of Anterior Curvature Metrics in Healthy and Keratoconic Eyes with a Portable Handheld Topographer

SIGNIFICANCE

This is a prospective observational investigation that studies the repeatability of several outcomes obtained with the Keratron Scout in healthy and keratoconic corneas. In addition, we have been able to determine the "noise" values of the instrument, which can be very useful when evaluating possible progression in keratoconus (KCN).

PURPOSE

The purpose of this study was to evaluate the repeatability of several anterior curvature metrics provided by a portable and handheld Placido disk-based topographer in healthy and keratoconic eyes.

METHODS

One eye from 50 keratoconic patients and 50 eyes from healthy patients were included in this prospective observational study. Two consecutive sessions (with three scans per session) were performed, and the following parameters were analyzed with a Keratron Scout topographer: flat keratometry, steep keratometry, flat corneal axis, corneal astigmatism, and flat and steep asphericities. In addition, in the KCN cohort, indices derived from the Cone Location and Magnitude Index were also recorded. Intrasession (first session, all three measurements) and intersession (one measurement from each session, selected randomly) statistics were calculated. The following variables were calculated: within-subject standard deviation, coefficient of repeatability (R), coefficient of variation, and intraclass correlation coefficient (ICC).

RESULTS

In healthy eyes, the intrasession and intersession ICCs were high (0.947 to 0.999), and for both flat keratometry and steep keratometry, the within-subject standard deviation was 0.08 and R was 0.24 diopters. Repeatability was slightly lower in the KCN group, but the ICC was greater than 0.95, whereas the R for flat keratometry was 0.41 diopters.

CONCLUSIONS

The Keratron Scout provides repeatable measures for the studied metrics in healthy and keratoconic eyes.

Assessment of Pattern and Shape Symmetry of Bilateral Normal Corneas by Scheimpflug Technology

Purpose: The aim of this study was to assess bilateral symmetry in normal fellow eyes by using optical and geometric morphometric parameters. Methods: All participants underwent complete biocular examinations. Scheimpflug tomography data from 66 eyes of 33 patients were registered. The interocular symmetry was based on five patterns: morphogeometric symmetry, axial symmetry at the corneal vertex, angular-spatial symmetry, direct symmetry (equal octants), and enantiomorphism (mirror octants). Results: No statistically significant differences were found between right and left eyes in corneal morphogeometric (p ≥ 0.488) and aberrometric parameters (p ≥ 0.102). Likewise, no statistically significant differences were found in any of the axial symmetry parameters analyzed (p ≥ 0.229), except in the surface rotation angle beta (p = 0.102) and translation coordinates X0 and Y0 (p < 0.001) for the anterior corneal surface, and the rotation angle gamma (p < 0.001) for the posterior surface. Similarly, no statistically significant differences were identified for direct symmetry (p ≥ 0.20) and enantiomorphism (p ≥ 0.75), except for some elevation data in the posterior surface (p < 0.01). Conclusions: The level of symmetry of both corneas of a healthy individual is high, with only some level of disparity between fellow corneas in rotation and translation references. Abnormalities in this pattern of interocular asymmetry may be useful as a diagnostic tool.

Agreement between Keratometric readings by VERION image guided System, Galilei G4 and Pentacam

Objective:

To study Agreement between Keratometric readings by VERION image guided System, Galilei G4 and Pentacam.

Methods:

The quasi experimental study was conducted at Armed Forces Institute of Ophthalmology, Rawalpindi, Pakistan from August 2016 to December 2016. Twenty five patients fulfilling the inclusion criteria participated in the study. All Patients were subjected to Keratometric assessment using Galilei G4 Dual Scheimpflug analyzer (Ziemer, Switzerland), Wavelight Oculyzer II (Pentacam, Germany) and Verion image guided system (Alcon). Steep and flat meridian and diopter of astigmatism by three systems were recorded and endorsed. All readings were taken by the same observer. Statistical Program for Social Sciences (SPSS) version 22.0 was used for statistical analysis. Results analyzed for significance by t-tests and Interclass correlation analysis. In t tests, P values of <0.05 was considered statistically significant while interclass coefficient of >0.7 was considered acceptable.

Results:

Fifty eyes of twenty-five patients (22 male, 28 female) with mean age of 29.50 ± 3.46 years were studied. Flat K, steep K and dioptric power of astigmatism were measured with verion, pentacam and Galilei G4. Interclass correlation analysis showed agreement between individual variables measured by the three devices, while one sample t test showed no significant difference between dioptric power of astigmatism between Verion-Pentacam and Verion- Galilei group. (p 0.178 for former and 0.622 for later group).

Conclusion:

Verion image guided system is comparable to other instruments used currently for keratometry. Verion can be interchangeably used with Pentacam and Galilee G4 in assessing corneal astigmatism.

Comparison of anterior segment measurements using Sirius Topographer® and Nidek Axial Length-Scan® with assessing repeatability in patients with cataracts

Purpose:

The purpose of this study is to evaluate anterior segment measurements obtained using CSO Sirius Topographer^® (CSO, Firenze, Italy) and Nidek Axial Length (AL)-Scan^® (Nidek CO., Gamagori, Japan).

Methods:

A total of 43 eyes of 43 patients were included in this prospective study. The central corneal thickness (CCT), anterior chamber depth (ACD), white-to-white distance (WTW), flat keratometry (K1), steep keratometry (K2), and mean keratometry (K) values were randomly measured three times with each device by the same examiner. The intraclass correlation coefficient of repeatability was analyzed. The compatibility of both devices was evaluated using the 95% limits of the agreement proposed by Bland and Altman.

Results:

Examiner achieved high repeatability for all parameters on each device except the WTW measured by Sirius. All measurements except WTW and K1 taken with the Sirius were higher than that taken with the Nidek AL-Scan^®. The difference in CCT, ACD, and WTW values was statistically significant.

Conclusion:

High repeatability of the measurements was achieved on both devices. Although Km, K1, and K2 measurements of the Sirius and the AL-Scan^® showed good agreement, WTW, CCT, and ACD measurements significantly differed between two devices. Thus, anterior segment measurements except for Km, K1, and K2 cannot be used interchangeably between Sirius and Nidek AL-Scan^® devices.

Axial length growth and the risk of developing myopia in European children

PURPOSE

To generate percentile curves of axial length (AL) for European children, which can be used to estimate the risk of myopia in adulthood.

METHODS

A total of 12 386 participants from the population-based studies Generation R (Dutch children measured at both 6 and 9 years of age; N = 6934), the Avon Longitudinal Study of Parents and Children (ALSPAC) (British children 15 years of age; N = 2495) and the Rotterdam Study III (RS-III) (Dutch adults 57 years of age; N = 2957) contributed to this study. Axial length (AL) and corneal curvature data were available for all participants; objective cycloplegic refractive error was available only for the Dutch participants. We calculated a percentile score for each Dutch child at 6 and 9 years of age.

RESULTS

Mean (SD) AL was 22.36 (0.75) mm at 6 years, 23.10 (0.84) mm at 9 years, 23.41 (0.86) mm at 15 years and 23.67 (1.26) at adulthood. Axial length (AL) differences after the age of 15 occurred only in the upper 50%, with the highest difference within the 95th percentile and above. A total of 354 children showed accelerated axial growth and increased by more than 10 percentiles from age 6 to 9 years; 162 of these children (45.8%) were myopic at 9 years of age, compared to 4.8% (85/1781) for the children whose AL did not increase by more than 10 percentiles.

CONCLUSION

This study provides normative values for AL that can be used to monitor eye growth in European children. These results can help clinicians detect excessive eye growth at an early age, thereby facilitating decision-making with respect to interventions for preventing and/or controlling myopia.

Precision of a new ocular biometer in children and comparison with IOLMaster

To assess the repeatability and reproducibility of AL-Scan in agreement with those by the IOLMaster in healthy children, two skilled operators measured ocular parameters in 58 children. The parameters included keratometry (K) values, anterior chamber depth (ACD), axial length (AL), central corneal thickness (CCT), pupil diameter (PD), and corneal diameter (CD). The cohort comprised of 32 boys and 26 girls. The AL-Scan measurements showed high repeatability, as the test-retest repeatability (TRT) values of AL, CCT, ACD, Kf, Ks, Km, CD, and PD were 0.09 mm, 5.1 μm, 0.04 mm, 0.28 D, 0.24 D, 0.21 D, 0.39 mm, and 0.22 mm, respectively. The within-subject coefficient of variation (CoV) was low (<0.35%) and the intraclass correlation coefficients (ICC) of all parameters were >0.85. The interobserver reproducibility was excellent with low values of TRT and ICC > 0.95. The CoV of AL, CCT, ACD, and K was <0.22%. The 95% limits of agreement between the AL-Scan and the IOLMaster were narrow for all parameters except for CD. The repeatability and reproducibility of the new biometer, Al-Scan, was excellent for all parameters and can be routinely used in children to measure the biometric values.

Comparability and repeatability of different methods of corneal astigmatism assessment

Purpose

To assess the comparability and repeatability of keratometric and astigmatism values measured by four techniques: Orbscan IIz^® (Bausch and Lomb), Lenstar LS 900^® (Haag-Streit), Cassini^® (i-Optics), and Total Cassini (anterior + posterior surface), in healthy volunteers.

Patients and methods

Fifteen healthy volunteers (30 eyes) were assessed by the four techniques. In each eye, three consecutive measures were performed by the same operator. Keratometric and astigmatism values were recorded. The intraclass correlation coefficient (ICC) was used to assess comparability and repeatability. Agreement between measurement techniques was evaluated with Bland-Altman plots.

Results

Comparability was high between all measurement techniques for minimum keratometry (K1), maximum keratometry (K2), astigmatism magnitude, and astigmatism axis, with ICC >0.900, except for astigmatism magnitude measured by Cassini compared to Lenstar (ICC =0.798) and Orbscan compared to Lenstar (ICC =0.810). However, there were some differences in the median values of K1 and K2 between measurement techniques, and the Bland-Altman plots showed a wide data spread for all variables, except for astigmatism magnitude measured by Cassini and Total Cassini. For J0 and J45, comparability was only high for J0 between Cassini and Orbscan. Repeatability was also high for all measurement techniques except for K2 (ICC =0.814) and J45 (ICC =0.621) measured by Cassini.

Conclusion

All measurement techniques showed high comparability regarding K1, K2, and astigmatism axis. Although posterior corneal surface is known to influence these measurements, comparability was high between Cassini and Total Cassini regarding astigmatism magnitude and axis. However, the wide data spread suggests that none of these devices should be used interchangeably.

Repeatability of Ophtha Top topography and comparison with IOL-Master and LenstarLS900 in cataract patients

AIM

To determine the repeatability of Ophtha Top topography and assess the consistency with intraocular lens (IOL)-Master and LenstarLS900 (Lenstar) in measuring corneal parameters among cataract patients.

METHODS

Totally 125 eyes were enrolled. Corneas were successively measured with Ophtha Top, IOL-Master and Lenstar at least three times. The flattest meridian power (Kf), the steepest meridian power (Ks), mean power (Km), J0 and J45 were recorded. Intra-class correlation coefficients (ICCs), the coefficient of variance (COV), within subject standard deviation (Sw), and test-retest repeatability (2.77Sw) were adopted to determine the repeatability. The 95% limit of agreement (95%LOA) and Bland-Altman plots were used to assess comparability.

RESULTS

Repeatability of Ophtha Top topography for measuring corneal parameters showed the ICCs were all above 0.93, 2.77Sw was lower than 0.31, and the COV of the Kf and Ks was lower than 0.25. The keratometric readings with Ophtha Top topography were flatter than with the IOL-Master and Lenstar devices, while the Pearson correlation coefficients were over 0.97. The J0 and J45 with Ophtha Top topography were smaller compared with Lenstar and IOL-Master, while was comparable between Lenstar and IOL-Master.

CONCLUSION

Ophtha Top topography shows excellent repeatability for measuring corneal parameters. However, differences between the Ophtha TOP topography and Lenstar, IOL-Master both in cornea curvature and the astigmatism should be noted clinically.

Assessment of the macula and choroid in pediatric keratoconus patients

Purpose

To present choroidal and macular thickness measurements in pediatric patients with keratoconus and to evaluate a possible correlation between anterior and posterior segment parameters.

Methods

50 eyes of 50 patients and 50 eyes of 50 age-matched controls were included in this cross-sectional comparative study. The participants underwent ophthalmologic examination including; refraction, visual acuity, biomicroscopy, corneal topography and optical coherence tomography. The choroidal thickness (CT) was measured at subfoveal area and at 500 microns intervals to the nasal and temporal to the fovea up to 1500 microns.

Results

The mean age of the patients and controls were 12.4 ± 1.9 and 12.0 ± 2.1 years. The mean thinnest corneal pachimetry was 456 ± 57 μm, the mean central macular thickness (CMT) was 258 ± 24 μm and the mean subfoveal choroidal thickness was 342 ± 30 μm for the patients. There was no significant difference between the patients and controls in regards of CMT and CT at any measured points (p > 0.05 for all). There was no correlation between anterior segment parameters and CMT. There was no correlation between anterior segment parameters and subfoveal choroidal thickness.

Conclusions

We may conclude that keratoconus does not affect the CMT and CT of pediatric keratoconus patients, and we may propose that we do not need a correction for this group of patients when we need to evaluate the CMT and CT.

Detailed Distribution of Corneal Epithelial Thickness and Correlated Characteristics Measured with SD-OCT in Myopic Eyes

Purpose

To investigate the detailed distribution of corneal epithelial thickness in single sectors and its correlated characteristics in myopic eyes.

Methods

SD-OCT was used to measure the corneal epithelial thickness distribution profile. Differences of corneal epithelial thickness between different parameters and some correlations of characteristics were calculated.

Results

The thickest and thinnest part of epithelium were found at the nasal-inferior sector (P < 0.05) and at the superior side (P < 0.05). respectively. Subjects in the low and moderate myopia groups have thicker epithelial thickness than those in the high myopia group (P < 0.05). Epithelial thickness was 1.39 μm thicker in male subjects than in female subjects (P < 0.001). There was a slight negative correlation between corneal epithelial thickness and age (r = −0.13, P = 0.042). Weak positive correlations were found between corneal epithelial thickness and corneal thickness (r = 0.148, P = 0.031). No correlations were found between corneal epithelial thickness, astigmatism axis, corneal front curvature, and IOP.

Conclusions

The epithelial thickness is not evenly distributed across the cornea. The thickest location of the corneal epithelium is at the nasal-inferior sector. People with high myopia tend to have thinner corneal epithelium than low–moderate myopic patients. The corneal epithelial thickness is likely to be affected by some parameters, such as age, gender, and corneal thickness.

Repeatability of Wavefront Aberration Measurements With a Placido-Based Topographer in Normal and Keratoconic Eyes

PURPOSE

To determine and compare the repeatability of anterior corneal higher order aberrations (HOAs) using a Placido-based topographer (Allegro Topolyzer; WaveLight Technologie AG, Alcon Laboratories, Erlangen, Germany) in a sample of normal and keratoconic eyes.

METHODS

Three repeated measurements of each cornea of normal and keratoconic eyes were taken with the Allegro Topolyzer. Repeatability of the HOAs (3rd- and 4th-order individual values and normalized polar Zernike coefficients, coma-like, root mean square (RMS) up to 8th-order values, HOA RMS, and total RMS for 6-mm pupil diameter) and central corneal power (3-mm pupil) were analyzed. Within-subject standard deviation (Sw), precision, repeatability, coefficient of variation (CV), and the intraclass correlation coefficient (ICC) were calculated.

RESULTS

Zernike coefficients were significantly different between the normal (36 eyes of 36 patients) and keratoconus (36 eyes of 36 patients) groups (P ≤ .03) except in Z(+1) 3, Z(+3) 3, Z(-4) 4, and Z(+4) 4. In the normal group, Sw was 0.031 µm or less, CV ranged from 6.49% (spherical aberration) to 37.18% (secondary astigmatism), and ICC values ranged from 0.227 to 0.982. In the keratoconus group, Sw was 0.059 µm or less, CV ranged from 2.06% (total RMS) to 25.82% (tetrafoil), and ICC values ranged from 0.839 to 0.996. In analyzing the keratoconus stages (Amsler-Krumeich classification), the repeatability of the Zernike coefficients tended to improve with increasing keratoconus stage.

CONCLUSIONS

The repeatability of corneal wavefront aberration provided by the Allegro Topolyzer was better in keratoconic eyes (good and moderate repeatability) than in normal eyes (moderate and poor repeatability). These results are important to eye care practitioners and refractive surgeons during refractive surgery planning or keratoconus detection, classification, and management. [J Refract Surg. 2016;32(5):338-344.].

Myopic Laser Corneal Refractive Surgery Reduces Interdevice Agreement in the Measurement of Anterior Corneal Curvature

OBJECTIVES

To investigate interdevice differences and agreement in the measurement of anterior corneal curvature obtained by different technologies after laser corneal refractive surgery.

METHODS

The prospective study comprised 109 eyes of 109 consecutive patients who had undergone laser-assisted in situ keratomileusis (LASIK). Preoperative and postoperative corneal parameters were measured by Scheimpflug imaging (Pentacam), Placido-slit-scanning (Orbscan) and auto-keratometry (IOLMaster). Preoperative and postoperative anterior corneal curvatures (K readings) were compared between devices. Interdevice agreement was evaluated by Bland-Altman analysis.

RESULTS

Preoperatively, the difference of K reading for Pentacam-IOLMaster (0.04±0.20 D) was not statistically significant (P=0.059). The differences between Pentacam-Orbscan and Orbscan-IOLMaster were 0.20±0.34 D (P<0.001) and -0.17±0.29 D (P<0.001), respectively. After surgery, no difference was found for Pentacam-Orbscan (-0.05±0.38, P=0.136). The differences between Pentacam-IOLMaster and Orbscan-IOLMaster were 0.13±0.29 D (P<0.001) and 0.19±0.34 D (P<0.001). Preoperative interdevice agreement (95% limit of agreement [LOA]) between Pentacam and Orbscan, Pentacam and IOLMaster, and Orbscan and IOLMaster were 1.31 D, 0.79 D and 1.14 D, respectively. The 95% LOAs decreased to 1.47 D, 1.14 D, and 1.34 D after refractive surgery.

CONCLUSION

Corneal refractive surgery changed the preoperative and postoperative interdevice differences in corneal curvature measurements and reduced interdevice agreement, indicating that the devices are not interchangeable.

Repeatability and Agreement of Central Corneal Thickness and Keratometry Measurements between Four Different Devices

Background. To estimate repeatability and comparability of central corneal thickness (CCT) and keratometry measurements obtained by four different devices in healthy eyes. Methods. Fifty-five healthy eyes from 55 volunteers were enrolled in this study. CCT (IOLMaster 700, Pentacam HR, and Cirrus HD-OCT) and keratometry readings (IOLMaster 700, Pentacam HR, and iDesign) were measured. For statistical analysis, the corneal spherocylinder was converted into power vectors (J0, J45). Repeatability was assessed by intraclass correlation coefficient (ICC). Agreement of measurements between the devices was evaluated by the Bland-Altman method. Results. The analysis of repeatability of CCT data of IOLMaster 700, Pentacam HR, and Cirrus HD-OCT showed high ICCs (range 0.995 to 0.999). The comparison of CCT measurements revealed statistically significant differences between Pentacam HR versus IOLMaster 700 (p < 0.0001) and Pentacam HR versus Cirrus HD-OCT (p < 0.0001), respectively. There was no difference in CCT measurements between IOLMaster 700 and Cirrus HD-OCT (p = 0.519). The repeatability of keratometry readings (J0 and J45) of IOLMaster 700, Pentacam HR, and iDesign was also high with ICCs ranging from 0.974 to 0.999. The Pentacam HR revealed significantly higher J0 in comparison to IOLMaster 700 (p = 0.009) and iDesign (p = 0.041); however, no significant difference was between IOLMaster 700 and iDesign (p = 0.426). Comparison of J45 showed no significant difference between IOLMaster 700, Pentacam HR, and iDesign. These results were in accordance with Bland-Altman plots. Conclusion. In clinical practice, the devices analyzed should not be used interchangeably due to low agreement regarding CCT as well as keratometry readings.

Corneal Topographic and Aberrometric Measurements Obtained with a Multidiagnostic Device in Healthy Eyes: Intrasession Repeatability

Purpose. To evaluate the intrasession repeatability of corneal curvature, eccentricity, and aberrometric measurements obtained with a multidiagnostic device in healthy eyes. Methods. This study enrolled 107 eyes of 107 patients ranging in age from 23 to 65 years. All of them underwent a complete anterior segment examination with the VX120 system (Visionix-Luneau Technologies, Chartres, France). Three consecutive measurements were obtained. The within-subject standard deviation (S_w), intrasubject precision (1.96 × S_w), and intraclass correlation coefficient (ICC) were calculated. Results. All S_w for corneal power measurements were below 0.26 D, with ICC above 0.982. The S_w for corneal astigmatism at different areas (3, 5, and 7 mm) was below 0.21 D, with ICC above 0.913. Concerning the axis of astigmatism, its S_w was below 11.27°, with ICC above 0.975. The S_w and ICC for corneal eccentricity were 0.067 and 0.957, respectively. The S_w and ICC for high-order aberration root mean square (RMS) were 0.048 µm and 0.901, respectively. For 3rd- and 4th-order aberrometric parameters, all S_w were below 0.037 µm and all ICC were higher than 0.84, except for quadrafoil RMS (ICC: 0.689). Conclusions. The multidiagnostic device evaluated is able to provide consistent measurements of corneal power, eccentricity, and third- and fourth-order aberrations in healthy eyes.

Comparison of Anterior Segment Measurements Obtained by Aladdin Optical Biometer and Sirius Corneal Topography

Objectives:

To assess the agreement of anterior segment parameter measurements derived from Aladdin optical biometer using optical low coherence interferometer and Sirius corneal topography using combined Scheimpflug-Placido disk.

Materials and Methods:

Data obtained using the Aladdin and Sirius systems from 110 eyes of 59 subjects who had no health problems other than refractive errors were retrospectively evaluated. Anterior chamber depth (ACD), flat (K1) and steep (K2) keratometry readings, and white-to-white distance (WTW) measurements taken with both devices were noted.

Results:

The mean age of the patients was 47.31±18.57 years (range, 25 to 79 years). Mean ACD was 3.35±0.4 mm using Aladdin and 3.42±0.44 mm using Sirius. Mean difference in ACD was 0.075 mm greater with Sirius than Aladdin (p<0.001). K1 measurement obtained by Aladdin was an average of 0.409 D higher (p<0.001). No statistically significant differences were detected between the two devices in respect to K2 and WTW measurements (p=0.18, p=0.85 respectively). Pearson correlation analysis showed high correlation between the two devices for all measurements (r=0.985, 0.895, 0.961 and 0.766 for ACD, K1, K2 and WTW respectively; p<0.001).

Conclusion:

Anterior segment parameters obtained by Aladdin optical biometer and Sirius anterior segment analysis system correlated well with each other and measurement differences between the devices were clinically negligible except for K1 values.

Simulated Keratometry Repeatability in Subjects with and without Down Syndrome

PURPOSE

To assess the repeatability of simulated keratometry measures obtained with Zeiss Atlas topography for subjects with and without Down syndrome (DS).

METHODS

Corneal topography was attempted on 140 subjects with DS and 138 controls (aged 7-59 years). Subjects who had at least three measures in each eye were included in analysis (DS: n = 140 eyes (70 subjects) and controls: n = 264 eyes (132 subjects)). For each measurement, the steep corneal power (K), corneal astigmatism, flat K orientation, power vector representation of astigmatism (J0, J45), and astigmatic dioptric difference were determined for each measurement (collectively termed keratometry values here). For flat K orientation comparisons, only eyes with >0.50 DC of astigmatism were included (DS: n = 131 eyes (68 subjects) and control: n = 217 eyes (119 subjects)). Repeatability was assessed using (1) group mean variability (average standard deviation (SD) across subjects), (2) coefficient of repeatability (COR), (3) coefficient of variation (COV), and (4) intraclass correlation coefficient (ICC).

RESULTS

The keratometry values showed good repeatability as evidenced by low group mean variability for DS versus control eyes (≤0.26D vs. ≤0.09D for all dioptric values; 4.51° vs. 3.16° for flat K orientation); however, the group mean variability was significantly higher in DS eyes than control eyes for all parameters (p ≤ 0.03). On average, group mean variability was 2.5 times greater in the DS eyes compared to control eyes across the keratometry values. Other metrics of repeatability also indicated good repeatability for both populations for each keratometry value, although repeatability was always better in the control eyes.

CONCLUSIONS

DS eyes showed more variability (on average: 2.5×) compared to controls for all keratometry values. Although differences were statistically significant, on average 91% of DS eyes had variability ≤0.50D for steep K and astigmatism, and 75% of DS eyes had variability ≤5 degrees for flat K orientation.