Comparison of central corneal thickness with four noncontact devices: An agreement analysis of swept-source technology

Reliability of Tear Meniscus Height Measurements in Contact Lens Wearers and Its Relationship With Discomfort Symptoms

OBJECTIVES

To evaluate the reliability and agreement of tear meniscus height (TMH) measurements performed with a corneal analyzer and optical coherence tomography (OCT) technology in contact lens (CL) wearers and its correlation with contact lens discomfort symptoms.

METHODS

Asymptomatic and symptomatic CL wearers classified through the Contact Lens Dry Eye Questionnaire-8 were evaluated with the Corneal Analyzer (Topcon CA-800) and OCT technology (Topcon 3D OCT-2000). The repeatability and intraclass correlation coefficient (ICC) were calculated. The agreement between devices was calculated using the Bland-Altman method. The relationship between TMH measurements and the Contact Lens Dry Eye Questionnaire-8 and Contact Lens Discomfort Index scores was assessed through the Spearman correlation coefficient.

RESULTS

Seventy-nine asymptomatic and 42 symptomatic CL wearers aged 34.24±12.50 years were enrolled. The repeatability values obtained for the CA-800 were 0.07 mm in all cases, and the ICC was 0.93 for the whole sample. The CA-800 provided significantly ( P <0.01) higher TMH values than the OCT for the whole sample (0.22±0.08 vs. 0.17±0.06 mm). A weak indirect correlation (ρ=-0.22) between the OCT TMH measurement and Contact Lens Discomfort Index scores was found ( P ≤0.04).

CONCLUSION

The CA-800 provides reliable TMH measurements during CL wear; however, they might not be interchangeable with OCT ones. Tear meniscus height measurements might be useful as a complementary sign to detect CL discomfort, but it cannot be used alone as a diagnostic tool.

Clinical applications of anterior segment swept-source optical coherence tomography: A systematic review

Optical coherence tomography (OCT) is a non-invasive method that provides the opportunity to examine tissues by taking cross-sectional images. OCT is increasingly being used to evaluate anterior segment (AS) pathologies. Swept-source (SS) OCT allows greater penetration and achieves better visualization of the internal configuration of AS tissues due to the longer wavelength employed and high scan speeds. We reviewed the utilization of AS SS-OCT in various conditions including glaucoma, ocular surface pathologies, iris tumors, refractive surgery, cataract surgery, and scleral diseases. A systematic literature search was carried out on PubMed, Scopus, and Web of Science databases between January 1, 2008, and September 1, 2022 using the following keywords: AS SS-OCT; dry eye and SS-OCT; ocular surface and SS-OCT; cornea and SS-OCT; dystrophy and SS-OCT; glaucoma and SS-OCT; ocular surface tumors and SS-OCT; conjunctival tumors and SS-OCT; refractive surgery and SS-OCT; cataract and SS-OCT; biometry and SS-OCT; sclera and SS-OCT; iris and SS-OCT; ciliary body and SS-OCT; artificial intelligence and SS-OCT. A total of 221 studies were included in this review. Review of the existing literature shows that SS-OCT offers several advantages in the diagnosis of AS diseases. Exclusive features of SS-OCT including rapid scanning, deeper tissue penetration, and better image quality help improve our understanding of various AS pathologies.

A Proposed Method for Estimating Refractive Error in Primary School Children

Background This study aimed to evaluate consecutive measurements of biometric parameters, age, and refraction in a cohort of Turkish primary school-age children and to assess the correlation between biometric changes and refraction. Methodology The study population was seven and 12-year-old children (n = 197). The retrieved data consisted of three consecutive measurements with a one-year interval for each subject. Data from one eye (right) were used. Age, gender, body mass index, spherical equivalent (SE), axial length (AL), anterior chamber depth (ACD), central corneal thickness (CCT), keratometry (K), and lens thickness (LT) were analyzed. The onset and final data were retrieved from the database in 2013 and 2016, respectively. Statistically, logistic and Cox regression models of all parameters were analyzed, and the significance level was set at 5%. Results The median of the onset and final SE values were -0.00 D (0.00-0.00) and 0.50 D (0.19-1.00), respectively. The onset AL (hazard ratio (HR) = 5.82, 95% confidence interval (CI) = 3.45-9.76, β = 1.76, p < 0.001), K_mean (HR = 2.28, 95% CI = 1.67-3.11, β = 0.82, p < 0.001), and age (HR = 0.77, 95% CI = 0.59-0.99, β = -0.26, p = 0.046) were correlated with myopia progression. To calculate the estimated SE, the onset data were included in the logistic regression model. The onset SE (β = 0.916, p < 0.001), AL (β = -0.451, p < 0.001), ACD (β = 0.430, p = 0.005), and K (β = -0.172, p < 0.001) were correlated with the mean final SE. An equation was generated using the regression model analysis. Conclusions The onset parameters of SE, AL, ACD, and K were confirmed to correlate with the final SE values in the proposed model. To confirm the use of the refractive calculator, a cross-validation analysis is needed to estimate three-year subsequent refractive error among seven and 12-year-old children.

Agreement of anterior segment measurements between four diagnostic imaging devices in myopic patients

PURPOSE

To compare the inter-device agreement of anterior chamber depth (ACD), central corneal thickness (CCT), flat keratometry (K1), steep keratometry (K2), corneal astigmatism (ΔK), and white-to-white (WTW) measurements.

METHODS

This is a retrospective study with 73 myopic patients (142 eyes). We extracted and compared anterior segment measurements (ACD, CCT, K1, K2, ΔK, and WTW) of four devices (OPD-Scan III, Pentacam HR, Lenstar LS 900, and Galilei G4), and performed pairwise agreement comparisons between them.

RESULTS

Agreement analyses revealed that the most agreement occurred: in Pentacam HR and Galilei G4 for ACD measurements, in Pentacam HR and Lenstar LS 900 for CCT measurements, in OPD-Scan III and Galilei G4 for WTW measurements, in OPD-Scan III and Pentacam HR for K1 and K2 measurements, and OPD-Scan III and Galilei G4 for ΔK measurements.

CONCLUSION

OPD-Scan III is interchangeable with both Galilei G4 and Lenstar LS 900 for WTW measurements. OPD-Scan III and the Pentacam-HR are interchangeable in K1, K2, and ΔK measurements. OPD-Scan III and Lenstar LS 900, and OPD-Scan III and Galilei G4 are interchangeable in K1 and ΔK measurements, respectively.

A comparison of central corneal thickness measured using noncontact methods and ultrasonic pachymetry

Aim

The aim of this study is to compare central corneal thickness (CCT) measurements in healthy eyes using ultrasonic pachymetry (UP) with values obtained using anterior segment spectral domain optical coherence tomography (SD-OCT), the Scheimpflug camera system, and noncontact specular microscopy.

Material and Methods

One hundred and twenty-five eyes of 117 healthy individuals (56 women, 61 men) were included. All patients underwent consecutive CCT measurement with UP, the Scheimpflug camera, anterior segment SD-OCT, and specular microscopy. The four devices could be read. Measurements from the four devices were classified in pairs and compared using the paired t-test. Relations between the devices were analyzed using the Pearson test. An alpha error level of P < 0.05 was regarded as statistically significant.

Results

The mean age of the healthy individuals included in the study was 34.75 ± 14.55 years (20-76). Mean CCT values were 541.21 ± 29.24 μm with UP, 539.26 ± 29.27 μm with the Scheimpflug camera system, 532.21 ± 29.53 μm with SD-OCT, and 534.45 ± 29.20 μm with specular microscopy. The differences in measurements at the paired t-test were statistically significant (P < 0.001 for all). However, measurements using the four devices exhibited significant mutual correlation (P < 0.001 for all).

Conclusions

CCT can be measured using different devices. Noncontact methods have now begun replacing UP, regarded as the gold standard. Although CCT values obtained from different devices were correlated, the difference between these measurements was statistically significant. Therefore, the same device should be used for measurement in the diagnosis and follow-up of diseases such as corneal ectasia and glaucoma where corneal thickness is important.

Comparison of central corneal thickness using non-contact tono-pachymeter (Tonopachy) with ultrasound pachymetry in normal children and in children with refractive error

Purpose

To compare the central corneal thickness (CCT) measured by non-contact tono-pachymeter [Tonopachy (TP)] with the gold standard ultrasound pachymetry (UP) in normal children and in children with refractive error.

Methods

This cross-sectional study involved 95 normal children (190 eyes) and 123 children with refractive error (246 eyes), a total of 218 children (436 eyes) aged 7-15 years. After refraction and complete ophthalmic evaluation, axial length was measured with IOLMaster 700, CCT was measured with TP followed by UP. The correlation between the CCT measurements obtained with the two methods was analysed by Intraclass correlation coefficient (ICC) and the limits of agreement were assessed with Bland-Altman analysis plot.

Results

Mean CCT measured with TP was 537.46 ± 36.41 μm and by UP was 537.17 ± 39.80 μm in normal children (P = 0.79) and in refractive error group, the mean CCT was 533.50 ± 34.91 μm by TP and 531.60 ± 36.30 μm by UP (P = 0.04). The 95% limits of agreement between TP and UP ranged from -19.2 to + 21.6 μm (mean = 1.20) for total children, -20.8 to + 21.4 μm (mean = 0.29) for normal group and -18.0 to + 21.8 μm (mean = 1.90) for refractive error group. ICC for CCT measurement between TP and UP was 0.980 for total children and refractive error group and 0.981 for normal group.

Conclusion

The CCT measurement obtained by TP showed an excellent agreement with UP. Hence non-contact TP can be used to assess CCT in children above seven years of age.

Agreement between 2 swept-source OCT biometers and a Scheimpflug partial coherence interferometer

PURPOSE

To evaluate the agreement between different parameters obtained with 2 swept-source optical coherence tomography (SS-OCT)-based biometers and 1 Scheimpflug camera with partial coherence interferometry (PCI).

SETTING

Single center, Oftalvist, Alicante, Spain.

DESIGN

Prospective case series.

METHODS

Biometry was performed in 49 eyes using 3 optical biometers: ANTERION SS-OCT, IOLMaster 700 SS-OCT, and Pentacam AXL PCI. Keratometry (K), J0 and J45 vectors, anterior chamber depth (ACD), central corneal thickness (CCT), white-to-white (WTW), lens thickness (LT), and axial length (AL) were measured with each device. Bland-Altman analysis was applied.

RESULTS

This study comprises 49 eyes of 49 patients. There were no statistically significant differences for K1, K2, J0 and J45 between the 3 devices (P > .9). In contrast, there was a statistically significant difference in the ACD, CCT, WTW, LT, and AL between the biometers (P < .001). Specifically, there was a statistically significant difference between ACD, CCT, and WTW values for all-pairwise comparisons. IOLMaster showed the shortest ACD value and ANTERION showed the largest ACD. IOLMaster showed the highest CCT and Pentacam showed the lowest CCT. IOLMaster showed the largest WTW and Pentacam showed the shortest WTW. The LT measured with IOLMaster was thicker than that measured with ANTERION. There was a statistically significant difference in the AL between IOLMaster and Pentacam, with a shorter AL measured with IOLMaster (P < .001), but no differences were found between ANTERION and IOLMaster (P = .599) and between ANTERION and Pentacam (P = .054).

CONCLUSIONS

Mean differences and the limits of agreement obtained in all-pairwise comparisons of the different parameters should be judged clinically to consider the interchangeability of these devices.

Comparison of 2 swept-source optical coherence tomography-based biometry devices

PURPOSE

To compare 2 swept-source optical coherence tomography (SS-OCT) biometers, IOLMaster 700 (biometer A), and ANTERION (biometer B).

SETTING

Department of Ophthalmology, Vienna Institute for Research in Ocular Surgery, Karl Landsteiner Institute, Hanusch Hospital, Vienna, Austria.

DESIGN

Retrospective study.

METHOD

Biometric measurements of cataract patients performed between June and July 2019 were reviewed. Patients scheduled for cataract surgery were measured with both SS-OCT devices on the same day. The following biometry parameters were compared: keratometry, central corneal thickness, anterior chamber depth (ACD), lens thickness (LT), and axial length (AL).

RESULT

In total, 389 eyes of 209 subjects were measured with both devices. The mean absolute difference between the keratometry data of the 2 devices was 0.04 ± 0.05 mm (7.80 ± 0.26 mm for biometer A and 7.82 ± 0.26 mm for biometer B; P < .0001) for the steep keratometry readings and 0.04 ± 0.04 mm (7.63 ± 0.26 mm and 7.65 ± 0.25 mm; P < .0001) for the flat keratometry readings. For ACD and LT, the mean absolute difference was 0.07 ± 0.04 mm and 0.07 ± 0.04 mm. The mean absolute difference for AL was 0.02 ± 0.03 mm (23.55 ± 1.18 mm for biometer A and 23.54 ± 1.18 mm for biometer B; P < .0001).

CONCLUSIONS

Good agreement was found between the 2 devices, with a minor offset for ACD and LT measurements. Although differences were found to be small, the devices should not be used interchangeably.

Repeatability of biometry measured by three devices and its impact on predicted intraocular lens power

PURPOSE

To compare the repeatability of ocular biometry measured with the LENSTAR LS 900, IOLMaster 700, and Anterion and its impact on predicted intraocular lens (IOL) power.

SETTING

Tertiary eye-care facility in South India.

DESIGN

Prospective, observational, cross-sectional study.

METHODS

Eyes diagnosed with cataract had 3 consecutive scans on each biometers. The repeatability was assessed using the within-subject standard deviation (Sw), test-retest repeatability, and coefficient of variation (CoV). The agreement was evaluated with the intraclass correlation (ICC). The IOL power was calculated with the Barrett Universal II formula.

RESULTS

The study comprised 127 eyes of 76 patients. The repeatability of all parameters for a given device were excellent (ICC >0.9, low CoV and Sw). The agreement of the parameters between the biometers was very good (range from 0.93 to 0.99). The predicted IOL power differed statistically between the devices (P < .05), but the difference was clinically insignificant between the 3 biometers (ICC >0.99 for repeat calculation of IOL power).

CONCLUSIONS

All the biometers included in the study had good to excellent repeatability of biometry parameters. The agreement of the predicted IOL power was excellent between the 3 optical biometers.

To compare central corneal thickness measurements obtained by Pentacam with those obtained by IOLMaster 700, Cirrus anterior segment optical coherence tomography and Tomey specular microscopy in normal healthy eyes

Purpose:

To compare central corneal thickness measurements obtained by Pentacam with those obtained by IOL Master 700, Cirrus Anterior segment optical coherence tomography and Tomey Specular microscopy in normal healthy eyes.

Methods:

Two hundred and six eyes of healthy subjects were included in the study. Each subject was assessed by four different methods of measuring central corneal thickness using Pentacam, IOL Master 700, Cirrus AS-OCT and Tomey Specular microscopy by a single examiner.

Results:

The mean CCT [± standard deviation (SD)] for Pentacam, IOL Master 700, Cirrus AS-OCT and Tomey Specular microscopy were Pentacam (Oculus), AS-OCT (Cirrus), IOL Master 700 and Specular microscopy (Tomey) were 523.75 (±27.75), 525.29 (±28.81),517.13 (±28.43) and 512.82 (±27.60) μm, respectively. All the means were significantly different from one another (P < 0.000). The differences between pairs of mean central corneal thickness (CCT) for Pentacam and IOL Master, Pentacam and anterior segment- optical coherence tomography (AS-OCT), and Pentacam and Specular microscopy are statistically significant. Bland–Altman plots showed that pentacam and IOL Master 700 have the closest agreement, followed by AS-OCT. Specular microscopy was found to have the poorest agreement with Pentacam.

Conclusion:

We found that CCT measurements of Pentacam did not correlate with measurements of IOL Master, or AS-OCT or Specular microscopy. In clinical practice, the devices analyzed should not be used interchangeably due to low agreement regarding CCT values.

Comparison of central corneal thickness measurements with three different optical devices

Purpose:

The purpose of this study was to compare and evaluate the agreement of central corneal thickness (CCT) values obtained with three different devices working according to optical principle in healthy eyes.

Methods:

60 eyes of 60 individuals (30 men and 30 women) were enrolled in this study. CCT measurements performed with Scheimpflug–Placido topographer (Sirius), spectral-domain optical coherence tomography (RTVue) with an anterior segment module, and optical biometer (AL-Scan) were compared. Bland–Altman analysis was used to demonstrate agreement between methods.

Results:

The mean age was 30.07 ± 7.313 years (range, 18–47 years). The mean CCT values obtained by RTVue, Sirius, and AL-Scan were 518.25 ± 36.38 µm, 526.08 ± 36.33 µm, and 513.50 ± 39.09 µm, respectively. The mean differences in CCT were 7.83 ± 14.15 µm between Sirius and RTVue, 12.58 ± 11.87 µm between Sirius and AL-Scan, and 4.75 ± 4.50 µm between RTVue and AL-Scan. The mean CCT was statistically different among the three groups (p < 0.05). All three modalities of CCT measurements correlated closely with each other, with Pearson’s correlation coefficients ranging from 0.924 to 0.961. The 95% limits of agreement were −19.90 to 35.56 µm between Sirius and RTVue, −10.69 to 35.85 µm between Sirius and AL-Scan, and −4.07 to 13.58 µm between RTVue and AL-Scan.

Conclusion:

Different results could be obtained through different noncontact devices in CCT measurements. Although the measurement values obtained by these devices show a high level of correlation, it would be a more correct approach to not use them directly interchangeably in clinical practice. Evaluation and follow-up of CCT should be performed using the same device.

Clinical role of swept source optical coherence tomography in anterior segment diseases: a review

PURPOSE

To note the comprehensive role of swept source anterior segment optical coherence tomography (SS-ASOCT) in anterior segment diseases.

METHODS

A systematic literature search was carried out on various medical databases using the keywords, swept source anterior segment optical coherence tomography; SS-ASOCT; Cornea and SS-ASOCT; SS-ASOCT and glaucoma; SS-ASOCT and cataract; SS-ASOCT and biometer; SS-ASOCT and tear film and ocular surface.Original works and novel reports describing the potential role of SS-ASOCT in various anterior segment conditions were included.

RESULTS

After a thorough assessment of literature, it was clear that the SS-ASOCT did provide newer insights into many anterior eye conditions. The rapid scan acquisition, deeper tissue penetration, and higher magnification did enhance many of our understandings, which were previously not possible. In addition, lenticular assessment under complex clinical scenarios with automated values on objective scale has made it a worthy tool with immense future possibilities.

CONCLUSIONS

SS-ASOCT unveiled various anterior segment findings which were of clinical importance.

Effect of photorefractive keratectomy on agreement of anterior segment variables obtained by a swept-source biometer vs a Scheimpflug-based tomographer

PURPOSE

To evaluate agreement of anterior segment variables between Pentacam-AXL and IOLMaster 700 before vs after photorefractive keratectomy (PRK).

SETTING

Salouti Eye Clinic, Shiraz, Iran.

DESIGN

Prospective cohort with interdevice agreement analysis.

METHODS

This study included healthy PRK candidates who were assessed with both devices preoperatively and 6 months after PRK. Only data from the right eye of each patient was analyzed. Pentacam-AXL average keratometry (AvgK) and zonal keratometry in the central 2.5 mm zone (zonal-K2.5) were each compared with mean keratometry (Km) from the IOLMaster 700. Other main outcome measures included vector analysis of corneal astigmatism (J0 and J45), central corneal thickness (CCT), anterior chamber depth (ACD), and white-to-white (WTW) distance. Axial length (AL) measurements by the same devices on a new cohort of 40 patients who had undergone PRK were also assessed. A paired t test was used to assess the interdevice measurement differences, and Bland-Altman analysis was used to calculate the 95% limits of agreement (LoA).

RESULTS

This study included 97 patients. Preoperative vs post-PRK 95% LoAs between Pentacam-AXL and IOLMaster 700 were as follows: AvgK/Km (-0.42, 0.08 diopter [D]) vs (-0.49, 0.18 D); zonal-K2.5/Km (-0.40, 0.32 D) vs (-0.57, 0.74 D); J0 (-0.33, 0.18 D) vs (-0.28, 0.35 D); J45 (-0.28, 0.23 D) vs (-0.24, 0.27 D); pupil pachymetry/CCT (-18, 12 μm) vs (-2.6, 19.6 μm); apical pachymetry/CCT (-17.4, 12.8 μm) vs (-1.7, 20.9 μm); ACD (-0.03, 0.13 mm) vs (-0.03, 0.13 mm); WTW (-0.68, 0.23 mm) vs (-0.63, 0.14 mm); and AL (-0.07, 0.01 mm) vs (-0.07, 0.03 mm), respectively.

CONCLUSIONS

PRK showed a negative impact on interdevice agreement for CCT and corneal power measurements, whereas it did not have a significant effect on the agreement of devices for ACD, WTW, AL, and the J45 astigmatism vectoral component. For IOL power measurement in post-PRK eyes, the 2 devices could be regarded as interchangeable for measuring AL and ACD but not for keratometry readings.

Variability of Central Corneal Thickness Measurements-Comparing Zeiss IOL Master and Tomey Corneal Specular Microscope

PURPOSE

The aim of this study was to compare the intraobserver repeatability and agreement of central corneal thickness (CCT) measurements by 2 commonly available instruments, Zeiss IOL Master 700 (SS-OCT-based optical biometry device) and Tomey corneal specular microscope EM-3000 (Noncontact specular microscopy).

DESIGN

Retrospective study.

METHODS

This is a retrospective analysis of data from routine clinical practice in which preoperative CCT measurements of 105 patients scheduled for cataract surgery were analyzed. Two consecutive CCT measurements were measured using Zeiss IOL Master 700 and Tomey corneal specular microscope EM-3000 by the same examiner. The repeatability of CCT measurements was analyzed by mean intraobserver difference, coefficient of repeatability (CR), and intraclass correlation. The agreement between the 2 methods was analyzed by mean difference and limits of agreement (LoA) using the Bland-Altman method.

RESULTS

The mean absolute intraobserver difference between the 2 measurements by Zeiss and Tomey were 3.41 ± 3.98 μm and 8.62 ± 9.52 μm (P < 0.0001), respectively. For Zeiss, the CR was 10.3 μm with 95% LoA of -10.5 to 10.1 μm. For Tomey, the CR was 25.2 μm with 95% LoA of -25.2 to 25.2 μm. The mean CCT measurements ± standard deviation by Zeiss and Tomey were 544.0 ± 38.1 μm and 532.6 ± 40.0 μm, respectively (P = 0.003). The 95% LoA in CCT between the 2 methods was -15.8 to 38.7 μm.

CONCLUSIONS

Zeiss IOL Master 700 has superior intraobserver repeatability and consistency than Tomey EM-3000. Zeiss produced higher CCT measurements than Tomey; hence, in clinical practice, interchangeability between these 2 methods is limited.