Optical Low-coherence Reflectometry Research Articles

Refining Decisions for Identifying Primary Care Patients Who Require A Work-Up for Glaucoma: Intraocular Pressure Changes with Central Corneal Thickness

Purpose: The factors associated with the increased risk of glaucoma include intraocular pressure (IoP), central corneal thickness (CCT), vertical cup-to-disc ratio, visual field index, age, and diabetes mellitus. We have investigated the relation of IoP with CCT in normal, healthy pre-presbyopic persons.
 Methods: A total population of 698 normal patients (1396 eyes), aged 4 to 40 years, were evaluated in two separate clinics, one in Houston, Texas, USA and the second in oakville, ontario, Canada. IoP was measured using a noncontact tonometry (nCT 20 Topcon). In Houston, CCT was determined by using the Pentacam (occulus Pentacam – Belinea) and an optical pachymetry that utilized optical low-coherence reflectometry (oLCR) technology, and in oakville, a Hagg-Streit slit lamp–mounted pachymeter was used.
 Results: of the total number of eyes tested, 1226 eyes had IoP of 21 millimetres of mercury (mm Hg) or lower and 134 eyes had IoP greater than 21 mm Hg. For the normal IoP group (n = 1226 eyes), the overall IoP mean was 15.63 +/– 2.87 mm Hg; the overall CCT mean was 550.21 +/– 39.64 micrometres (µm). In the normal IoP group, for every 10 µm change in CCT, IoP changed a statistically significant amount of 2.49 mm Hg (p <0.05 to <0.001), except for the 10 nm CCT bins above and below the 550 µm mean.
 Conclusions: Although many investigators have described a positive correlation between IoP and CCT, this relationship has not been demonstrated in normal, healthy pre-presbyopic persons. There is a significant change of IoP with CCT (2.49 mm Hg IoP change per 100 µm of CCT). These normative data allow primary eye care clinicians to accurately determine normal and abnormal IoP and refine the index of suspicion for identifying patients who need to be worked up for glaucoma.

Comparative study of anterior segment measurement with rotating dual Scheimpflug analyzer and optical low coherence reflectometry

AbstractPurpose The aim of the study was to compare the anterior segment measurements obtained with optical low coherence reflectometry (Lenstar LS 900, version 1.1, Haag‐Streit, Koeniz, Switzerland) and rotating dual Scheimpflug analyzer (Galilei Dual Scheimpflug Analyzer versión 3, Ziemer Ophthalmic Systems, Port, Switzerland).Methods Prospective, comparative, observational study in which 59 eyes of 30 patients who needed a preoperative study for a refractive procedure or cataract surgery were studied with both the Lenstar 900 and Galilei systems. Central corneal thickness (CCT), anterior chamber depth (ACD), horizontal limbal distance (white‐to‐white distance; WTW), pupil diameter (PD), as well as the keratometric readings at the steepest meridian (Ks), the flattest meridian (Kf), the corneal astigmatism power, and the plus astigmatic cylinder axis were measured. Degree of agreement between Ks, Kf, astigmatism power, cylinder axis, CCT, ACD, WTW and PD were the main outcome measures.Results Ks, Kf, corneal astigmatism power, cylinder axis, and WTW measurements with the Lenstar and the Galilei system showed narrow 95% limits of agreement (LoA), which implies good agreement (p>0.05, Bland‐Altman plot analysis). In contrast, range and 95% LoA were significantly different for CCT, ACD and PD values (p<0.05, Bland‐Altman plot analysis).Conclusion In clinical practice, the Lenstar and the Galilei system can be used interchangeably for WTW measurements and K readings but not for CCT, ACD and PD values.

Comparison of anterior segment measurements with optical low-coherence reflectometry and rotating dual Scheimpflug analysis

To compare the anterior segment measurements obtained with optical low-coherence reflectometry (OLCR) (Lenstar LS 900, version 2.1.1) and rotating dual Scheimpflug analysis (Galilei G1, version 3). Private practice, Policlinic Lleida, Lleida, Spain. Prospective comparative observational study. The following measurements were performed in patients requiring a preoperative study for a refractive procedure or cataract surgery and healthy volunteers from the clinic's staff: central corneal thickness (CCT), anterior chamber depth (ACD), horizontal limbal distance (white-to-white distance [WTW]), pupil diameter, keratometry (K) readings at the steepest meridian (steep K) and the flattest meridian (flat K), corneal astigmatism power, and plus astigmatic cylinder. Measurements were taken using the OLCR device and rotating dual Scheimpflug analyzer. The main outcome measure was the degree of agreement between steep K, flat K, astigmatism power, cylinder axis, CCT, ACD, WTW, and pupil diameter measurements. The study enrolled 100 eyes of 100 subjects. Steep K, flat K, corneal astigmatism power, cylinder axis, and WTW measurements with the OLCR device and Scheimpflug analyzer showed narrow 95% limits of agreement (LoA), which implies good agreement (P>.05, Bland-Altman plot analysis). In contrast, the range and 95% LoA for CCT, ACD, and pupil diameter values were statistically significantly different (P<.05, Bland-Altman plot analysis). In clinical practice, the OLCR device and the rotating dual Scheimpflug analyzer system can be used interchangeably for WTW measurements and K readings but not for CCT, ACD, and pupil diameter values. No author has a financial or proprietary interest in any material or method mentioned.

The Effect of Room Illumination on the Measurement of Anterior Segment Parameters

To evaluate the effect of room illumination on the measurement of anterior segment parameters. In this comparative study, measurements of anterior segment parameters of 25 eyes of 25 healthy patients were performed by optical low-coherence reflectometry (OLCR). Measurements were taken under photopic conditions (150 lux) and under mesopic conditions (3 lux). Paired t test by SPSS 16.0 was used to compare the anterior segment measurements performed in both conditions. A P value lower than 0.05 was accepted as statistically significant. The mean age of the patients was 27.09±1.72 years (range, 20-40 years). Of the anterior segment parameters, axial length and keratometry did not show significant difference between photopic and mesopic conditions (P=0.541 and P=0.812, respectively). The mean anterior chamber depth measurements was 3.04±0.35 mm and 3.06±0.35 mm, whereas the mean lens thickness was 3.75±0.36 mm and 3.77±0.36 mm in the mesopic and photopic conditions, respectively. The mean pupil diameter measurement was 4.86±0.70 mm under photopic conditions and 6.36±0.94 mm under mesopic conditions. The anterior chamber depth, lens thickness, and pupil diameter showed significant difference between photopic and mesopic conditions (P=0.01, P=0.006, and P=0.0001, respectively). Anterior chamber depth, lens thickness, and pupil diameter were affected by the changes in luminance while performing measurements with OLCR. Considering the age of the study group, further studies are needed to test the measurement of accommodation amplitude.

Comparison of central corneal thickness measurements with three new optical devices and a standard ultrasonic pachymeter.

To compare the RTVue spectral optical coherence tomography (SD-OCT), Sirius Scheimpflug-Placido topographer, Lenstar optical low coherence reflectometry (OLCR) and ultrasound pachymetry (USP) devices in terms of their agreement and repeatability of measuring central corneal thickness (CCT). In this prospective study, 50 eyes of 50 patients were included. Three repeated measures were obtained using SD-OCT, Scheimpflug-Placido topographer and USP and five measurements were determined with the OLCR. Bland-Altman plots were used to assess agreement among the instruments, and 95% limits of agreement (LoA) for each comparison were calculated. Intra-examiner repeatability was assessed using intraclass correlation coefficients (ICCs). The mean CCT by SD-OCT, Scheimpflug-Placido topographer, OLCR, and USP were 525.90±34.08 µm, 525.92±34.10 µm, 530.30±35.62 µm, and 543.50±37.11 µm respectively. All 4 modalities of CCT measurements correlated closely with each other, with Pearson correlation coefficients ranging from 0.977 to 0.995. The mean differences (and upper/lower LoA) for CCT measurements were -0.05±6.77 µm (13.3/-13.3) between SD-OCT and Scheimpflug-Placido topographer, 4.38±3.79 µm (11.8/-3.1) between OLCR and SD-OCT, 4.38±6.03 µm (16.2/-7.5) between OLCR and Scheimpflug-Placido topographer, 13.20±6.46 µm (25.9/0.5) between USP and OLCR, 17.59±6.76 µm (30.8/4.3) between USP and SD-OCT, and 17.58±8.13 µm (33.5/1.6) between USP and Scheimpflug-Placido topographer. Intra-examiner repeatability was excellent for all devices with ICCs>0.98. For most practical purposes, CCT measurements with the RTVue, Sirius and Lenstar can be used interchangeably. Although highly correlated, CCT measurement differences between USP and these 3 optical instruments can be significant depending on the clinical situation.

The Effects of Smoking on Anterior Segment Parameters, Retinal Nerve Fiber Layer, and Pupillary Functions

Address for Correspondence/Yazisma Adresi: Bengu Ekinci Koktekir MD, Selcuk University School of Medicine, Department of Ophthalmology, Konya, Turkey Gsm: +90 532 353 27 16 E-mail: benguekinci@hotmail.com Received/Gelis Tarihi: 23.06.2013 Accepted/Kabul Tarihi: 23.07.2013 This study was presented as free paper presentation in the 46th Annual Turkish Ophthalmological Society Meeting, Antalya, Turkey, 2012 Objectives: To evaluate the alterations in the anterior segment parameters, retinal nerve fiber layer, and pupillary functions in smokers. Materials and Methods: In this case-control study, 45 eyes of 45 smokers and 45 eyes of 45 non-smoker control subjects were evaluated. All patients underwent measurement of anterior segment parameters with optical low coherence reflectometry (OLCR), mesopic and photopic pupillary diameter with an aberrometer device, retinal nerve fiber layer thickness with optical coherence tomography, and dry-eye assessment with Schirmer’s test. The results were compared with independent t-test by SPSS 16.0 Inc., and a p-value lower than 0.05 was determined as significant. Results: There was a significant difference between both groups in terms of mesopic pupil diameters that were measured with both OLCR and aberrometer device (p=0.03 and 0.02, respectively). Schirmer scores were also significantly decreased in smokers (p=0.001). The other measured parameters demonstrated no difference between smokers and non-smokers (p>0.05 for all). Conclusion: Smoking may affect pupillary functions, especially the mesopic pupillary diameter, and may cause a deficiency in pupil response under dark circumstances. (Turk J Ophthalmol 2014; 44: 11-4)

Comparison of central corneal thickness measurements using optical low-coherence reflectometry, Fourier domain optical coherence tomography, and Scheimpflug camera

To compare the results of central corneal thickness (CCT) measurements obtained using optical low-coherence reflectometry (OLCR), Fourier domain optical coherence tomography (FD-OCT), and a Scheimpflug camera (SC), combined with Placido corneal topography. A total of 25 healthy subjects were enrolled in the present study, and one eye of each subject was included. A detailed ophthalmic examination was performed in all cases following CCT measurements with OLCR, FD-OCT, and SC. The results were compared using an ANOVA test. Bland-Altman analysis was used to demonstrate agreement between methods. Intra-examiner repeatability was assessed by using intraclass correlation coefficients (ICCs). Statistically significant differences were observed between the results of the CCT measurements obtained using the three different devices (p=0.009). Significant correlations were found between OLCR and FD-OCT (r=0.97; p<0.0001), FD-OCT and SC (r=0.91; p<0.0001), and OLCR and SC (r=0.95; p<0.0001). The 95% limits of agreement (LOA) obtained from Bland-Altman plots were from -7.2 μm to 28.7 μm for OLCR versus FD-OCT, from -19.2 μm to 30.4 μm for OLCR versus SC, and from -42.6 to 32.3 μm for FD-OCT versus SC. Intra-examiner repeatability was excellent for each method, with ICCs >0.98. Although the results of CCT measurements obtained from these three devices were highly correlated with one another and the mean differences between instruments were comparable with the reported diurnal CCT fluctuation, the measurements are not directly interchangeable in clinical practice because of the wide LOA values.

Comparison of two optical biometers in intraocular lens power calculation

Aims:To compare the consistency and accuracy in ocular biometric measurements and intraocular lens (IOL) power calculations using the new optical low-coherence reflectometry and partial coherence interferometry.Subjects and Methods:The clinical data of 122 eyes of 72 cataract patients were analyzed retrospectively. All patients were measured with a new optical low-coherence reflectometry system, using the LENSTAR LS 900 (Haag Streit AG)/ALLEGRO BioGraph biometer (Wavelight., AG), and partial coherence interferometry (IOLMaster V.5.4 [Carl Zeiss., Meditec, AG]) before phacoemulsification and IOL implantation. Repeated measurements, as recommended by the manufacturers, were performed by the same examiner with both devices. Using the parameters of axial length (AL), corneal refractive power (K1 and K2), and anterior chamber depth (ACD), power calculations for AcrySof SA60AT IOL were compared between the two devices using five formulas. The target was emmetropia. Statistical analysis was performed using Statistical Package for the Social Sciences software (SPSS 13.0) with t-test as well as linear regression. A P value < 0.05 was considered to be statistically significant.Results:The mean age of 72 cataract patients was 64.6 years ± 13.4 [standard deviation]. Of the biometry parameters, K1, K2 and [K1 + K2]/2 values were significantly different between the two devices (mean difference, K1: −0.05 ± 0.21 D; K2: −0.12 ± 0.20 D; [K1 + K2]/2: −0.08 ± 0.14 D. P <0.05). There was no statistically significant difference in AL and ACD between the two devices. The correlations of AL, K1, K2, and ACD between the two devices were high. The mean differences in IOL power calculations using the five formulas were not statistically significant between the two devices.Conclusions:New optical low-coherence reflectometry provides measurements that correlate well to those of partial coherence interferometry, thus it is a precise device that can be used for the pre-operative examination of cataract patients.

Correlation of Choroidal Thickness and Volume Measurements with Axial Length and Age Using Swept Source Optical Coherence Tomography and Optical Low-Coherence Reflectometry

Purpose. To report choroidal thickness and volume in healthy eyes using swept source optical coherence tomography (SS-OCT). Methods. A prospective observational study of 122 patients examined with swept source OCT (DRI-OCT, Topcon, Japan). In each eye, we performed 256 horizontal scans, 12 mm in length and centered on the fovea. We calculated choroidal thickness manually with a built-in caliper and automatically using DRI-OCT mapping software. Choroidal volume was also automatically calculated. We measured axial length with optical low-coherence reflectometry (Lenstar LS 900, Haag-Streit, Switzerland). Results. The choroid has focally increased thickness under the fovea. Choroid was thinnest in the outer nasal quadrant. In stepwise regression analysis, age was estimated as the most significant factor correlating with decreased choroidal thickness (F = 23.146, P < 0.001) followed by axial length (F = 4.902, P = 0.03). Refractive error was not statistically significant (F = 1.16, P = 0.28). Conclusions. SS-OCT is the first commercially available system that can automatically create choroidal thickness and volume maps. Choroidal thickness is increased at the fovea and is thinnest nasally. Age and axial length are critical for the estimation of choroidal thickness and volume. Choroidal measurements derived from SS-OCT images have potential value for objectively documenting disease-related choroidal thickness abnormalities and monitoring progressive changes over time.

Comparison of Anterior Segment Measurements Using Scanning-Slit Topography and Optical Low-Coherence Reflectometry (OLCR) Biometry

Purpose: To compare the results of anterior segment biometry including white-to-white (WTW) between scanning-slit topography (ORBscan IIz, Bausch & Lomb), optical low-coherence reflectometry (OLCR) biometry (Lenstar, Haag-Streit), and Castroviejo calipers. Methods: Measurements on 72 eyes of 36 patients that underwent refractive surgery were measured using ORBscan, Lenstar, and calipers and compared. Ocular biometry parameters used in this study included the WTW, central corneal thickness, anterior chamber depth (ACD), keratometry, and pupil size. Results: The WTW measurements using ORBscan and calipers (11.57 ± 0.35 mm and 11.58 ± 0.34 mm, respectively) were statistically similar. However, the measurement using Lenstar (12.05 ± 0.40 mm) was significantly greater than with the other methods (p < 0.001). Central corneal thickness and keratometry measurements using ORBscan were greater than when using Lenstar (p = 0.01 for both). ACD and pupil size measurement using Lenstar were greater than when using ORBscan (p < 0.001 for both). Conclusions: Because WTW and ACD measurements using Lenstar were greater than when using ORBscan and calipers, unexpected high-vaulting may be observed due to the selection of a larger-sized posterior chamber phakic intraocular lens. Therefore, the differences in measurements obtained when using these methods should be considered. J Korean Ophthalmol Soc 2014;55(5):656-661

Comparison of Central Corneal Thickness Measurements with a Rotating Scheimpflug Camera, a Specular Microscope, Optical Low-Coherence Reflectometry, and Ultrasound Pachymetry in Keratoconic Eyes

Objective: To compare central corneal thickness (CCT) measurements with a rotating Scheimpflug camera (RSC), noncontact specular microscopy (SM), optical low-coherence reflectometry (OLCR), and ultrasonic pachymetry (UP) in keratoconus (KC) patients. Method: In this prospective study, four CCT measurements taken with an RSC, SM, OLCR, and UP were compared in 81 eyes of 44 consecutive KC patients. The KC patients were divided into four subgroups according to Amsler-Krumeich’s KC classification. Results: The RSC and UP measurements of the CCT were not statistically significant in all the groups. Comparison of the SM vs. the OLCR measurements yielded statistically significant differences in all the KC patients and in all KC stages. In all the KC patients, RSC and OLCR showed a high correlation coefficient factor (r = 0.87, p = 0.000). Conclusion: CCT measurements with RSC are comparable to those achieved with UP. Compared with the other devices, according to SM measurements, the central cornea is thicker in all keratoconic eyes and in all KC grades, and it is thinner according to OLCR. RSC, UP, SM, and OLCR should not be used interchangeably in keratoconic eyes.

Myopic Shift and Outdoor Activity among Primary School Children: One-Year Follow-Up Study in Beijing

PurposeTo assess whether a change in myopia related oculometric parameters of primary school children in Beijing was associated with indoors and outdoors activity.MethodsThe longitudinal school-based study included school children who were examined in 2011 and who were re-examined in 2012. The children underwent a comprehensive eye examination including ocular biometry by optical low-coherence reflectometry and non-cycloplegic refractometry. Parents and children had a detailed interview including questions on time spent indoors and outdoors.ResultsOut of 681 students examined at baseline, 643 (94.4%) returned for follow-up examination. Within the one-year period, mean time spent daily outdoors increased by 0.4±0.9 hours, mean axial length by 0.26±0.49 mm, the ratio of axial length divided by anterior corneal curvature (AL/CC) by 0.03±0.06, and myopic refractive error by −0.06±0.89 diopters. In multivariate analysis, elongation of axial length was significantly associated with less total time spent outdoors (P = 0.02; standardized coefficient beta −0.12) and more time spent indoors with studying (P = 0.007; beta: 0.14) after adjustment for maternal myopia (P = 0.02; beta: 0.12). An increase in AL/CC was significantly associated with less time spent outdoors (P = 0.01; beta:−0.12) after adjustment for paternal myopia (P = 0.003; beta: 0.15) and if region of habitation was excludedors for leisure (P = 0.006; beta:−0.13), with less total time spent outdoors (P = 0.04; beta:−0.10), or with more time spent i. An increase in myopic refractive error, after adjustment for age, was significantly associated with less time spent outdo ndoors with studying (P = 0.005; beta: 0.13).ConclusionsA change in oculometric parameters indicating an increase in myopia was significantly associated with less time spent outdoors and more time spent indoors in school children in Greater Beijing within a study period of one year. Our study provides additional information on the potentially helpful role of outdoors activity in the prevention of myopia. Public health care measures such as school agendas may potentially take it into account.

Lack of Association Between Primary Angle-Closure Glaucoma Susceptibility Loci and the Ocular Biometric Parameters Anterior Chamber Depth and Axial Length

Three susceptibility loci for primary angle-closure glaucoma (PACG) were recently identified: PLEKHA7 rs11024102, COL11A1 rs3753841, and rs1015213 located in the intergenic region between PCMTD1 and ST18. The purpose of this study was to investigate the associations of these loci with the ocular biometric parameters anterior chamber depth (ACD) and axial length (AL). Genotype and ocular biometric data were available for four population-based studies, including three from Singapore (Singapore Chinese Eye Study, Singapore Malay Eye Study, and Singapore Indian Eye Study) and one from China (Beijing Eye Study), exceeding 7000 participants. ACD and AL were measured using the IOLMaster for the Singapore cohorts and optical low-coherence reflectometry (Lenstar 900 Optical Biometer) for the Beijing cohort. Five readings were obtained for each participant and the average was computed. Analysis excluded any eye that was pseudophakic or aphakic. ACD measurements and genotype data of the three loci were available for 7245, 7243, and 7239 subjects, respectively. We noted nominal evidence of association between single nucleotide polymorphism (SNP) rs1015213 (PCMTD1-ST18) and a shallower ACD when all data were meta-analyzed (β = -0.033, P = 0.021). When multiple testing was considered, the observation was nonsignificant. There was no association between ACD and rs11024102 (PLEKHA7) or rs3753841 (COL11A1). We did not observe significant associations between AL and any of the three SNPs. The lack of association between the PACG susceptibility loci with ACD or AL suggests that predilection to PACG may be mediated by factors other than shallow anterior chamber or short eyeball length.

Polarization sensitive optical low-coherence reflectometry for blood glucose monitoring in human subjects

A device based on polarization sensitive optical low-coherence reflectometry is developed to monitor blood glucose levels in human subjects. The device was initially tested with tissue phantom. The measurements with human subjects for various glucose concentration levels are found to be linearly dependent on the ellipticity obtainable from the home-made phase-sensitive optical low-coherence reflectometry device. The linearity obtained between glucose concentration and ellipticity are explained with theoretical calculations using Mie theory. A comparison of results with standard clinical methods establishes the utility of the present device for non-invasive glucose monitoring.

Effect of Pharmacologic Pupil Dilation on OLCR Optical Biometry Measurements for IOL Predictions

To determine the possible influence of pupil dilation on intraocular lens (IOL) power predictions made using optical biometry with Lenstar LS 900® (Haag-Streit AG, Koeniz, Switzerland). A total of 72 eyes of 72 patients scheduled to undergo cataract surgery were prospectively examined using the optical low-coherence reflectometry (OLCR) optical biometer before and after pupil dilation with tropicamide 1%. The measurements made were axial length, central corneal thickness, anterior chamber depth (ACD), lens thickness, mean keratometry, corneal diameter (CD), and pupil diameter. Holladay II and SRK/T formulas were used to calculate IOL power. Agreement between the 2 measurement modes (with and without dilation) was assessed by calculating intraclass correlation coefficients (ICC) and constructing Bland-Altman plots. The mean age of the patients was 74.71 ± 7.53 years (range 56-90). Among the variables determined, only ACD varied significantly according to pupil dilation (p<0.001). The ICC data revealed excellent intraobserver correlation between measurements made with and without dilation, except for CD. The IOL power predictions were unmodified. The use of pupil dilation does not seem to influence measurements and IOL predictions made using this OLCR optical biometer.

Central Corneal Thickness Measurements With Different Imaging Devices and Ultrasound Pachymetry

The aim of this study was to compare 4 methods of central corneal thickness (CCT) measurements in terms of their agreement, repeatability, and measurement time. CCT was measured in 184 eyes of 92 healthy subjects by the same examiner. The methods used were as follows: noncontact specular microscopy (SM; Topcon SP-3000P; Topcon Corporation, Tokyo, Japan), Pentacam rotating Scheimpflug photography system (Oculus Inc, Wetzlar, Germany), optical low-coherence reflectometry (OLCR; LenStar LS900; Haag-Streit AG, Koeniz, Switzerland), and ultrasound pachymetry (UP; PachPen; Accutome Inc, Malvern, PA). The duration for each examination was measured by an independent observer. The mean age (±SD) of the subjects was 54.3 (± 15.3) years. The mean CCTs (± SD) for SM, Pentacam, OLCR, and UP were 507.8 (± 30.2), 538.4 (± 31.7), 531.8 (± 31.4), and 528.3 (± 32.9) μm, respectively. The Bland-Altman plots showed closest agreement for OLCR-UP, followed by OLCR-Pentacam and Pentacam-UP. SM had the poorest agreement with the other methods. CCTs measured by SM were on average 20 to 30 μm thinner than those of the other methods. The coefficient of repeatability for SM, Pentacam, OLCR, and UP were 3.14%, 4.23%, 1.51%, and 3.46%, respectively. The mean measurement times (± SD) were 13.5 (± 5.7), 45.7 (± 12.3), 18.5 (± 7.1), and 5.6 (± 1.0) seconds, respectively. CCT measurements between OLCR-UP and OLCR-Pentacam are comparable and can be used interchangeably in clinical practice. However, SM underestimates CCT compared with the other methods, whereas Pentacam was found to be the least repeatable and took the longest time.

Biometric measurements in highly myopic eyes

To assess the repeatability and accuracy of optical biometry (Lenstar LS900 optical low-coherence reflectometry [OLCR] and IOLMaster partial coherence interferometry [PCI]) and applanation ultrasound biometry in highly myopic eyes. Division of Preventive Ophthalmology, Zhongshan Ophthalmic Center, Guangzhou, China. Comparative evaluation of diagnostic technology. Biometric measurements were taken in highly myopic subjects with a spherical equivalent (SE) of -6.00 diopters (D) or higher and an axial length (AL) longer than 25.0 mm. Measurements of AL and anterior chamber depth (ACD) obtained by OLCR were compared with those obtained by PCI and applanation A-scan ultrasound. Right eyes were analyzed. Repeatability was evaluated using the coefficient of variation (CoV) and agreement, using Bland-Altman analyses. The mean SE was -11.20 D ± 4.65 (SD). The CoVs for repeated AL measurements using OLCR, PCI, and applanation ultrasound were 0.06%, 0.07%, and 0.20%, respectively. The limits of agreement (LoA) for AL were 0.11 mm between OLCR and PCI, 1.01 mm between OLCR and applanation ultrasound, and 1.03 mm between PCI and ultrasound. The ACD values were 0.29 mm, 0.53 mm, and 0.51 mm, respectively. These repeatability and agreement results were comparable in eyes with extreme myopia (AL ≥ 27.0 mm) or posterior staphyloma. The mean radius of corneal curvature was similar between OLCR and PCI (7.66 ± 0.24 mm versus 7.64 ± 0.25 mm), with an LoA of 0.12 mm. Optical biometry provided more repeatable and precise measurements of biometric parameters, including AL and ACD, than applanation ultrasound biometry in highly myopic eyes. No author has a financial or proprietary interest in any material or method mentioned.

Comparison of Central Corneal Thickness Measurements With Optical Low-Coherence Reflectometry and Ultrasound Pachymetry and Reproducibility of Both Devices

To compare the accuracy of optical low-coherence reflectometry (Lenstar LS 900; Haag Streit, Köniz, Switzerland) and conventional ultrasound pachymetry (UP) (US 4000; Nidek, Japan) for measuring central corneal thickness and to assess the interexaminer reproducibilities of both devices. Department of Ophthalmology, Selcuklu Faculty of Medicine, Selcuk University was the study setting. Central corneal thickness (CCT) was measured in both eyes of 65 emmetropic patients by the same examiner using Lenstar LS 900 noncontact biometry and UP. To assess the interexaminer reproducibility, 2 different examiners consecutively obtained CCT measurements in 16 eyes with Lenstar LS 900 noncontact biometry and UP. Mean CCT measurements with Lenstar LS 900 noncontact biometry and ultrasound biometry were 541.09 ± 33.8 and 545.69 ± 34.0, respectively. Significant correlation was present between these 2 measurements; intraclass correlation coefficient was found to be 95.8% (95% confidence interval: 93.2%-97.4%)(P < 0.001). Interexaminer reproducibility with Lenstar was high, and the intraclass correlation was found to be 99.3% (95% confidence interval: 98.0%-99.7%). We have also investigated the interexaminer reproducibility with UP in these 16 patients, and the results showed a 99.2% (95% confidence interval: 97.7%-99.7%) intraclass correlation. The results of Lenstar LS 900 noncontact biometry correlated with the results of UP. It may be used as an alternative method to UP for measuring CCT. Because of the mild underestimation of CCT by Lenstar, the measurements should be carefully evaluated in patients whose intraocular pressure must strictly be monitored.

Outdoor Activity and Myopia among Primary Students in Rural and Urban Regions of Beijing

To assess associations among outdoor activity, ocular biometric parameters, and myopia among grade 1 and grade 4 primary students in Beijing. School-based, cross-sectional study. A total of 382 grade 1 and 299 grade 4 children participated in the study. The children underwent a comprehensive eye examination, including ocular biometry by optical low-coherence reflectometry and noncycloplegic refractometry. Parents and children participated in a detailed interview, including questions on time spent indoors and outdoors. Factors associated with myopia. The study included 681 children, with 382 (56.1%) students from grade 1 (mean age, 6.3 ± 0.5 years; range, 5-8 years) and 299 students from grade 4 (mean age, 9.4 ± 0.7 years; range, 8-13 years); 370 students (54.3%) lived in the urban region. The mean daily time spent outdoors was 1.6 ± 0.8 hours (range, 0.5-5.1 hours). In multivariate analysis, axial length was significantly associated with older age (P<0.001; standardized β coefficient, 0.28), taller body height (P = 0.001; β, 0.18), maternal myopia (P = 0.03; β, 0.09), and urban region of habitation (P<0.001; β, -0.21), or alternatively to the region of habitation, with less time spent outdoors (P = 0.001; β, -0.16) and more time spent indoors studying (P = 0.02; β, 0.10). The axial length-to-corneal curvature radius ratio was associated with older age, urban region of habitation, maternal and paternal myopia, and paternal level of education. Presence of myopia (defined as refractive error ≤-1 diopters in the right eye) was associated with older age (P<0.001; odds ratio [OR], 1.45; 95% confidence interval [CI], 1.24-1.69), maternal myopia (P<0.001; OR, 2.99; 95% CI, 1.94-5.35), and urban region of habitation (P<0.001; OR, 0.17; 95% CI, 0.11-0.26), or alternatively to the region of habitation, with less time spent outdoors (P<0.001; OR, 0.32; 95% CI, 0.21-0.48) and more time spent indoors studying (P<0.001; OR, 1.38; 95% CI, 1.09-1.75). Less outdoor activity, more indoor studying, older age, maternal myopia, and urban region of habitation were associated with longer ocular axial length and myopia in grade 1 and grade 4 primary school children in Greater Beijing. Remaining outdoors more (e.g., during school) may reduce the high prevalence of myopia in the young generation in Beijing.

Correlation Between Central Corneal Thickness, Anterior Chamber Depth, and Corneal Keratometry as Measured by Oculyzer II and WaveLight OB820 in Preoperative Cataract Surgery Patients

To compare and correlate central corneal thickness (CCT), anterior chamber depth (ACD), and keratometric (flat and steep K) measurements using two anterior segment imaging methods, a Scheimpflug camera system (Oculyzer II [Oculus Optikgeräte GmbH]) and a partial coherence biometry system (WaveLight OB820 [Alcon Laboratories Inc]) in eyes undergoing cataract surgery. Ninety patients (mean age: 66±13 years [range: 32 to 88 years]) underwent preoperative measurement of CCT, ACD, and keratometric measurements by Scheimpflug tomography (Oculyzer II) and optical low coherence reflectometry (WaveLight OB820). Interdevice agreement and correlation between the two techniques were assessed. All measurements were highly correlated and showed no clinically significant difference between methods. Mean CCT was 554.21±39.07 μm and 546.59±37.75 μm for the Oculyzer II and WaveLight OB820, respectively (R²=0.9268). Mean ACD was 2.63±0.44 mm and 2.63±0.43 mm for the Oculyzer II and WaveLight OB820, respectively (R(2)=0.9488). The principal meridian keratometric values were also highly correlated. Mean flat K was 42.88±1.50 diopters (D) and 42.96±1.40 D for the Oculyzer II and WaveLight OB820, respectively (R²=0.8741). Mean steep K was 44.08±1.79 D and 44.26±1.95 D for the Oculyzer II and WaveLight OB820, respectively (R(2)=0.9159). Our data show that the Oculyzer II and WaveLight OB820 provide measurements that are in agreement with published values for CCT and ACD in patients. Excellent agreement for CCT and ACD was found between the two devices, as demonstrated by a high degree of correlation and linearity, in addition to minimal bias. Thus, CCT, ACD, and K measurements by these instruments can both be used in clinical preparation, and their agreement is an ensuring precision factor for cataract and refractive surgeons.