Partial Coherence Interferometer Research Articles

Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese.

To compare anterior segment biometry parameters in progress and non-progress primary angle closure glaucoma (PACG) among Malay and Chinese patients. A cross-sectional study was conducted between November 2015 and December 2016 involving 75 patients with PACG (43 Malays and 32 Chinese) who were recruited from a single glaucoma center in Malaysia. Ocular examination included anterior segment biometry measurements on the selected eye. Axial length (AL) and anterior chamber depth (ACD) measurement was done using a noncontact partial coherence interferometer (IOL Master, Carl Zeiss, Germany). Anterior chamber angle (ACA) was measured by Anterior Segment-OCT (Spectralis Heidelberg, Germany). Humphrey visual field (HVF) 24-2 analysis of the same eye was conducted and compared with the HVF when diagnosis was made. Progression of PACG patients was assessed according to the Hodapp, Parrish and Anderson's (HPA) classification, they were then divided into progress and non-progress groups. Comparison of anterior segment biometry parameters between Malay and Chinese PACG patients with and without progression was analyzed using independent T test. Multivariate ANOVA analysis was used to compare the anterior segment parameters between progress and non-progress PACG patients, with adjustment for age, gender, lens status, family history and presence of diabetes mellitus. Chinese PACG patients have significant shorter AL (22.18 mm ± 0.76) and narrower ACA (11.96° ± 6.00) compared to Malay PACG patients. Among the progress group, Chinese PACG patients have significant shorter AL, shallower ACD and narrower ACA compared to Malays. However, after controlling for confounding factors, there was significant difference in ACA between Malay and Chinese PACG. There was also no significant difference of ocular biometry measurement between Chinese and Malay patients in progress and non-progress group. There was racial influence in ocular biometry measurement in PACG patients. Chinese have significant narrower ACA compared to Malays. Serial AS-OCT monitoring is important in management of PACG. Neoh FP, Azhany Y, Siti-Azrin AH, et al. Anterior Segment Biometry in Primary Angle Closure Glaucoma Patients with Visual Field Progression: Comparison between Malays and Chinese. J Curr Glaucoma Pract 2023;17(1):3-8.

Agreement between Two Swept-Source Optical Coherence Tomography Biometers and a Partial Coherence Interferometer.

PurposeTo evaluate the level of agreement between ANTERION (Heidelberg Engineering, Heidelberg, Germany), OA-2000 (Tomey, Nagoya, Japan), and IOLMaster 500 (Carl Zeiss AG, Jena, Germany).MethodsFifty-one eyes of 51 patients were included in the study. Flat keratometry (K) and steep K, vector component of astigmatism (Jackson cross-cylinder at 0° and 90° [J0] and Jackson cross-cylinder at 45° and 135° [J45]), anterior chamber depth, and axial length were compared using the three devices. Repeated measures analysis of variance was conducted to compare the mean values of the biometrics. Pearson correlation test was conducted to analyze the correlations of the measured values, and a Bland-Altman plot was used to assess the agreement between the three devices. The predicted intraocular lens power of each device was compared to the others using the SRK/T, Haigis, Barrett Universal II, and Kane formulas.ResultsAll K values measured using ANTERION were flatter than those of other instruments. However, good agreement was observed for flat K (ANTERION - OA-2000; 95% limits of agreement [LoA], 0.86 diopters [D]) and steep K (ANTERION - OA-2000; 95% LoA, 0.93 D) and OA-2000 - IOLMaster 500 (95% LoA, 0.93 D). J0 and J45 vector components of astigmatism were not statistically different; however, the agreements were poor between the devices (95% LoA ≥1.97 D). Anterior chamber depth values of ANTERION and OA-2000 were interchangeable (95% LoA, 0.15 mm). The axial length showed a high agreement (95% LoA ≤0.17 mm) among the three devices. The predicted intraocular lens powers of the three devices were not interchangeable regardless of formulas (95% LoA ≥1.04 D).ConclusionsSignificant differences in ocular biometrics were observed between ANTERION and the other two devices. This study demonstrated that only axial length showed good agreement among devices.

Comparison of acquisition rate and agreement of axial length with two swept-source optical coherence tomographers and a partial coherence interferometer.

To assess the acquisition rate and agreement of axial length (AL) measurements with the OA-2000, Anterion, and IOLMaster 500 in cataractous patients. In total, 298 eyes of 191 cataractous patients were enrolled and scanned with the three devices in random order. The success rate of AL measurements per device was calculated and a chi-square test was utilized to identify the differences in acquisition rate between the three devices. Logistic regression analysis was applied to evaluate the association of different cataract types and severity with the AL measurement acquisition rate. Bland-Altman plots were mapped to appraise the agreement of AL values. AL measurements were successfully achieved in 288 eyes (96.64%) with the OA-2000, in 282 eyes (94.30%) with the Anteiron, and in 246 eyes (82.55%) with the IOLMaster 500. Significant differences in the acquisition rate were found between either of the SS-OCT devices and IOLMaster 500 by chi-square analysis (P < 0.001). No significant difference was noted between OA-2000 and Anterion. Increasing severity of posterior subcapsular cataract was associated with a higher failure rate with the IOLMaster 500. Bland-Altman analysis identified good agreement between the three biometers with narrow 95% limits of agreement. The OA-2000 and Anterion showed similarly higher acquisition rate of AL measurements than IOLMaster 500 in cataractous patients. Good agreement for AL values was found between the three biometers in cataractous patients.

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

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). Single center, Oftalvist, Alicante, Spain. Prospective case series. 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. 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). 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.

Anterior chamber depth measurement before and after photorefractive keratectomy. Comparison between IOLMaster and Pentacam.

an accurate measurement of anterior chamber depth (ACD) both in eyes that underwent corneal refractive surgery (CRS) and in eyes that did not, can be crucial, as in case of intraocular lens (IOL) calculation in eyes that need to undergo cataract extraction, or during the evaluation of glaucomatous patients. The aim of this nonrandomized retrospective case series was to measure anterior chamber depth (ACD) before and after photorefractive keratectomy (PRK), comparing a rotating Scheimplfug camera (RSC) and a partial coherence interferometer (PCI). 125 right eyes of 125 patients were examined. ACD was measured with RSC and a PCI preoperatively and 1, 3 and 6 months postoperatively. The results were analyzed using Friedman and ANOVA test for repeated measures, Wilcoxon test, Pearson and Bland-Altmann correlation. Both instruments showed an ACD decrease after CRS. The mean preoperative difference in ACD between the two instruments was 0.11 ± 0.11 (range: -0.07 mm to 0.73 mm) (p < 0.05) (r = 0.92). The mean difference in ACD reduction between the two instruments was: 0.08 ± 0.11 (range: -0.35 to 0.39 mm) (p < 0.05, r = 0.93) at 1 month; 0.13 ± 0.11 (range: -0.09 mm to 0.48 mm) (p < 0.05, r = 0.93) at 3 months; 0.14 ± 0.15 (range: -0.16 to 0.82 mm) (p < 0.05) (r = 0.87), at 6 months. The ACD decrease shown with both instruments suggests the presence of anterior segment remodeling after PRK. RSC measurements were larger than PCI ones, both before and after PRK.

Comparison of Clinical Outcomes between Swept-source Optical Coherence Tomography Biometer and Partial Coherence Interferometer

Comparison of Clinical Outcomes between Swept-source Optical Coherence Tomography Biometer and Partial Coherence Interferometer

Comparison of SRK/T and Haigis formulae in the prediction of refractive outcome after phacoemulsification

Purpose To compare the accuracy of SRK/T and Haigis formulae used for intraocular lens (IOL) power calculation by a partial coherence interferometer in patients undergoing phacoemulsification surgery. Patients and methods A prospective interventional clinical study included 70 eyes of 60 patients, who underwent uncomplicated phacoemulsification with IOL implantation from October 2015 to December 2017. Preoperative axial length (AL), corneal curvature (keratometry), and preoperative anterior chamber depth (preoperative ACD) were measured using Nidek AL-scan optical biometer and the IOL power was determined using both SRK/T and Haigis formulae. The difference between the predicted value and the postoperative spherical equivalent was calculated for both the formulae by the end of the follow-up (3 months postoperatively). Results The mean errors of the two formulae were SRK/T: −0.225±0.61 D and Haigis: 0.171±0.68 D; the mean absolute errors of the two formulae were 0.534±0.36 and 0.533±0.44 D, respectively. There was no statistically significant difference between the mean error of the two formulas used in the overall performance, but was significant in eyes with an AL of more than 25 mm. The proportion of patients having a prediction error within ±0.50 D of SRK/T formula (54.29%) was comparable to those of Haigis (55.71%) and the prediction errors within ±1.0 D were 87.14 and 85.71%, respectively. There is a weak correlation between the mean AL, keratometry and the Haigis–SRK/T prediction differences (r 2=0.273). Conclusion The calculation of IOL power using SRK/T and Haigis formulae resulted in an accurate postoperative refraction. In long AL subcategory, the mean absolute error of Haigis was less compared with the SRK/T formula.

Accuracy of the SRK/T Formula Using Partial Coherence Interferometer, Al-Scan after Phacoemulsification

Purpose: To evaluate the accuracy of SRK/T formula used for IOL power calculation by partial coherence interferometer in patients undergoing phacoemulsification surgery. Patients and methods: A prospective interventional clinical study included 40 eyes of 34 patients who underwent uncomplicated phacoemulsification with IOL implantation from March 2015 to March 2017. Biometries were measured using ultrasound or AL-scan and intraocular lens power was calculated using the SRK-T formula. Patients were divided into 2 groups based on device used for IOL power calculation: AL-scan or ultrasound ; Axial length: >=25 mm or < 25mm; or lens opacity: Cataractous or clear lens. The mean error (ME) was calculated from the difference between the formula predicted refractive error and the actual post operative refractive error by the end of the followup (3 months postoperative). Results: Mean axial length measured preoperatively was 27.47 ± 316mm (21.55-34.05) mm. 60 percent of the patients were within 0.5 D of the predicted refractive error and 90 percent were within 1.0 D. There was no statistically significant difference in the overall performance of the SRK/T formula between the mean error when dividing the patients into 2 groups according to: device used for IOL power calculation (P= 0.274); Axial length (P= 0.46); or lens opacity (P= 0.18) in precision of predicting postoperative refraction. Conclusions : SRK/T formula helps in improvement of the accuracy of IOL power calculation and decreasing the postoperative refractive error. By using SRK/T formula, there was no statistically significant difference between the AL-scan or applanation ultrasound used in biometry.

Differences in retinal shape between East Asian and Caucasian eyes.

To investigate whether retinal shape is different between East Asians and Caucasians. There were 36 East Asian and 40 Caucasian young adults, with refractions between +0.75D and -5.50D. Peripheral eye lengths were obtained after pupil dilation using the Lenstar partial coherence interferometer. Measurements were obtained along the horizontal and vertical meridians of the visual field out to ±35° and ±30°, respectively, in 5° steps. Retinal co-ordinates were estimated using a validated method from the peripheral eye length measurements and ray-tracing through a modified Le Grand full theoretical eye. Rays were directed normally towards the anterior cornea. Retinal shapes were described in terms of vertex radius of curvature (Rv ), asphericity (Q) and equivalent radius of curvature (REq ) along both horizontal and vertical meridians. Rv was smaller in East Asian than in Caucasians (mean difference ± 95% CI -0.7 ± 0.5 mm), along the horizontal meridian than the vertical meridian (-1.2 ± 0.6 mm), and in myopia than in emmetropia (-1.0 ± 0.6 mm). Rv along the horizontal meridian, but not along the vertical meridian, became smaller as myopia increased. Q did not vary significantly with meridian, refraction group or race. The same pattern of results occurred for REq as for Rv . The percentage differences of heights under the estimated retinal surfaces showed steeper retinas in East Asians than in Caucasians; the differences between East Asian and Caucasian emmetropes were 2.5% and <1% along horizontal and vertical meridians, respectively, and corresponding differences for myopes were 4.6% and 1.8%. East Asians had steeper retinas than Caucasians. The horizontal meridian had steeper retinas than the vertical meridian. Myopes had steeper retinas than emmetropes. Racial differences in retinal shape in both emmetropes and myopes, combined with the high prevalence of myopia in East Asia, suggest that retinal shape may play a role in myopia development.

Comparison of biometry and intraocular lens power calculation performed by a new optical biometry device and a reference biometer

To compare biometry measurements and intraocular lens (IOL) power calculations obtained by a new optical A-scan interferometer biometer (Galilei G6) (new biometer) and a partial coherence interferometer biometer (IOLMaster 500) (reference biometer). Private practice, Recife, Brazil. Retrospective comparative study. Cataract patients who had biometric measurements with the new biometer and the reference biometer were included in the study. Comparisons were performed for axial length (AL), keratometry (K), anterior chamber depth (ACD), and IOL power calculation to reach emmetropia with an Acrysof SN60WF IOL using the Haigis formula. The Pearson correlation coefficient and the 95% limits of agreement (LoA) were calculated. The paired Student t test and the Wilcoxon test were used to assess differences between devices. Eighty-eight eyes (88 patients) were studied. Both biometers provided statistically similar mean IOL power to reach emmetropia, AL, keratometry, and ACD measurements (P>.05). The differences in these variables did not vary as their mean values increased, and there was a strong positive correlation between the values obtained by both devices for each variable. The 95% LoA values for AL, mean keratometry, ACD, and IOL power were 0.27mm, 1.08 diopters (D), 0.66mm, and 1.56 D, respectively. The 2 devices were comparable with regard to mean IOL power, mean AL, K, and ACD measurements. However, the wide range of differences between the devices suggests they should not be used interchangeably.

Comparison of Ocular Biometry Measurements Using A-Scan Ultrasound and Two Types of Partial Coherence Interferometers

Purpose: To compare the measurement results of 3 ocular biometry devices, A-scan ultrasound and two types of partial coherence interferometers in normal and cataractous eyes. Methods: This study included 42 normal eyes and 40 cataractous eye. Axial length and anterior chamber were measured using three ocular biometry measurements, ultrasonography (HiScan, Optikon 2000, Rome, Italy), IOL Master (Carl Zeiss, Jena, Germany), and AL-scan (Nidek, Gamagori, Japan), and mean corneal curvature and corneal diameter were measured using two partial coherence interferometers. The results were compared in each group. Results: Significant differences in measurements existed among the 3 ocular biometry devices (A-scan ultrasound, IOL Master and AL-scan) in normal eyes (p < 0.001) and cataractous eyes (p = 0.034). However, the measurements were not significantly different between the 2 partial coherence interferometers (IOL Master and AL-scan) in both groups. We confirmed lower agreement among the 3 ocular biometry devices in cataractous eyes compared with normal eyes in terms of a larger range of 95% agreement and error in cataractous eyes. Conclusions: Significant differences in measurements were observed when using the 3 ocular biometry devices in both normal and cataractous eyes. Because of low agreements between ocular biometry devices in cataractous eyes, complementing the measurements between ocular biometry devices is necessary when measuring cataractous eyes. J Korean Ophthalmol Soc 2016;57(5):757-762

Repeatability and Reproducibility of a New Partial Coherence Interferometer; AL-Scan Optic Biometer

The purpose of this study was to evaluate the intra-observer repeatability and inter-observer reproducibility of the ocular parameter measurements in cataract eyes using the new partial coherence interferometer, AL-Scan. Eighty-six eyes with cataracts were included in this prospective study. Axial length, average keratometry, anterior chamber depth, central corneal thickness, white-to-white distance and intraocular lens power calculation with the SRK-T formula were determined by two observers. The measurements were repeated by the same observers using the same AL-Scan unit on the same eye approximately 2 weeks later, just before surgery. Inter-observer reproducibility was excellent, with very high interclass correlation coefficients (˃0.984) for all measured parameters. Standard deviations (Sw) and coefficients of variation (CV) of the repeated measurements were low, which demonstrated high intra-observer repeatability, except for the central corneal thickness and white-to-white distance measurements (Sw≤0.224 ∞CV≤ 1.072). The precision of the measurements obtained by the AL-Scan biometer is highly reliable and observer-independent.

Comparison of the Postoperative Refractive Errors Measured by Ultrasound and Partial Coherence Interferometers after Phacovitrectomy

Purpose: To compare the accuracy of refractive outcome measured by Ultrascan (Alcon, Fort Worth, TX, USA) and partial coherence interferometers after phacovitrectomy. Methods: We performed a retrospective study in 74 eyes of 74 patients who underwent phacovitrectomy. SRK-T formula was used to predict intraocular lens (IOL) power. The difference between the predicted and postoperative refractive outcomes for the 2 methodologies (Ultrascan and IOL Master [Zeiss, Carl Zeiss, Jena, Germany]) were compared. The predicted refractive outcome was defined as the estimated refractive error when the selected IOL was inserted. Results: The axial length measured using IOL Master was statistically longer than when measured using Ultrascan (23.85 ± 0.15 mm, 23.56 ± 0.15 mm, p < 0.001). Based on keratometry, statistically significant difference between the 2 groups was not observed. The postoperative refractive error was more accurate when using the IOL Master than Ultrascan (0.08 ± 0.74, 0.47 ± 0.69, p < 0.001). However, in cases of vitreous hemorrhage, the postoperative refractive error was 0.42 ± 0.49 with the IOL Master and 0.07 ± 0.54 with the Ultrascan. Conclusions: Generally, IOL Master is a more accurate method for calculating the IOL power prior to phacovitrectomy. However, in cases of vitreous hemorrhage, Ultrascan appears superior to IOL Master when calculating the IOL power. J Korean Ophthalmol Soc 2015;56(7):1059-1064

The Roles of Cornea and Axial Length in Corneal Hysteresis among Emmetropes and High Myopes: A Pilot Study

Purpose: To observe the roles of cornea and axial length (AL) in corneal hysteresis (CH) among emmetropes and high myopes.Materials and Methods: The CH, corneal resistance factor (CRF) and corneal-compensated intraocular pressure (IOPcc) of 40 young emmetropes (spherical equivalent +/−0.50 D) and 40 age-matched high myopes (−6D or more) were measured by the Ocular Response Analyzer. AL was measured using a partial coherence interferometer. The mean keratometry reading (meanK) and corneal volume (CV) in 4 zones were measured using the Pentacam. Full stromal thickness (FST) and epithelial and Bowman's thicknesses (Epi + BT) were evaluated using confocal microscopy. Valid confocal microscopic results from the more emmetropic eyes of 30 emmetropes and the more myopic eyes of 27 high myopes were studied.Results: High myopes exhibited significantly longer AL (27.34 ± 0.90 mm versus 23.71 ± 0.79 mm), lower CH (10.17 ± 1.38 mmHg versus 11.11 ± 1.25 mmHg), and higher IOPcc (16.50 ± 3.05 mmHg versus 13.91 ± 2.49 mmHg) compared with emmetropes. The 2 groups showed similar CRF, CVs, meanK, FST and Epi + BT. By combining the results of both groups, CH and CRF were significantly correlated with FST (r2 = 0.368 and r2 = 0.408, respectively), CVs (r2 = 0.251–0.391 and r2 = 0.201–0.346, respectively), but not with Epi + BT or meanK. Furthermore, AL and IOPcc were significantly correlated with CH (r2 = 0.112 and r2 = 0.161, respectively) but not with CRF. The multivariate analysis indicated that FST (standardized coefficients, β = 0.591) and CV (β = 0.575) had stronger association than IOPcc and AL for CH.Conclusions: High myopes exhibited lower CH than emmetropes. Although CH had stronger correlation with FST than AL, it might contain the biomechanical properties of components other than the cornea.

Intraocular lens prediction accuracy after corneal refractive surgery using K values from 3 devices

To compare results of intraocular lens (IOL) power calculation methods using different keratometry (K) values after myopic refractive surgery. Seoul St. Mary's Hospital, Seoul, South Korea. Evaluation of diagnostic test or technology. The IOL power of patients who had cataract surgery after refractive surgery was calculated using the SRK/T formula with true net power (TNP) and the equivalent K using the Pentacam Scheimpflug system. The simulated K, 2.0 mm zone of total mean power (TMP 2.0 mm) maps, and 4.0 mm zone of total optical power (TOP 4.0 mm) maps were calculated using the Orbscan II scanning-slit topographer and keratometer of the IOLMaster partial coherence interferometer (PCI). The IOL power was also calculated with the Haigis-L method with the corneal radius using the PCI system. The PCI axial length was used with all methods. The prediction error and absolute prediction error measured with the Haigis-L, TNP, TMP 2.0 mm, and TOP 4.0 mm were significantly lower than the equivalent K, simulated K, and PCI K (P<.05). The percentages of correct refraction predictions within ± 0.50 diopter (D), ± 1.00 D, and ± 2.00 D in the Haigis-L method were the highest (64.5%, 80.6%, and 100%, respectively) of all methods. The Haigis-L using corneal radius with the PCI measurement was the most predictable method for IOL calculation after corneal refractive laser surgery in patients without a clinical history. The TMP 2.0 mm in the scanning-slit topographer and the TNP in the Scheimpflug system may also be relatively predictable keratometric values for IOL calculation.

Agreement between a partial coherence interferometer and 2 manual keratometers

To establish repeatability and validity of a partial coherence interferometry (PCI) device in patients with astigmatism. Industry and university. Observational studies. A prospective study determined the agreement between the IOLMaster 500 PCI device and the Marco 1-position manual keratometer for measurement of mean corneal power, astigmatic power, and axis. Interinstrument and interoperator reproducibility was also assessed. A retrospective study determined the agreement between the PCI device and the Javal 2-position manual keratometer. Repeatability was also assessed. The 95% limits of agreement (LoA) were determined for all comparisons. Comparing the PCI device and the 1-position manual keratometer, the axis was within 5degrees in 72.1% of eyes; the cylinder power differed by 0.18 diopter (D) (95% LoA, ±0.45 D) and the mean power by 0.33 D (95% LoA, ±0.25 D). Comparing the PCI device and the 2-position manual keratometer, the axis was within 5 degrees in 77.1% of eyes. The mean difference in cylinder power between the 2 instruments was close to zero (95% LoA, ±0.37 D); however, the mean power differed by 0.34 D (95% LoA, ±0.25 D). The repeatability of the PCI device was better than that of both manual keratometers. Agreement between the PCI device and the 2-position manual keratometer for measures of corneal astigmatism and axis was excellent. The 1-position manual keratometer gave slightly lower estimates of corneal astigmatism, although the agreement for axis was excellent. Thus, the PCI device is an appropriate choice for the calculation of toric intraocular lenses. Dr. Bullimore is a consultant to Carl Zeiss Meditec AG and Alcon Surgical, Inc. Drs. Buehren and Bissmann are employees of Carl Zeiss Meditec AG.

Effect of Day Length on Eye Growth, Myopia Progression, and Change of Corneal Power in Myopic Children

Because of the northern location of Denmark, the length of the day over the year varies from 7 to 17.5 hours. Experimental and clinical results suggest that the development of myopia may be related to ambient light exposure. The purpose of current study was to investigate whether axial eye growth, myopia progression, or corneal power change in Danish myopic children varies with the length of the day. Cross-sectional study. Two hundred thirty-five children 8 to 14 years of age found to have myopia during screening for a clinical trial (ClinicalTrial.gov identifier, NCT00263471; accessed December 6, 2005). All children found to have any value of spherical equivalent that was myopic (<0 diopters [D]) at the first of 2 visits were included. Cycloplegic refraction was measured using an autorefractor, axial eye length, and corneal power using an automatic combined noncontact partial coherence interferometer and keratometer. The accumulated number of daylight hours during the measurement period was calculated for each participant using an astronomical table. Change over 6 months in axial length, refraction, and corneal power. Accumulated hours of daylight ranged from 1660 to 2804 hours. Significant correlations were found between hours of daylight and eye elongation (P = 0.00), myopia progression (P = 0.01), and corneal power change (P = 0.00). In children with an average of 2782 ± 19 hours of daylight, axial eye growth was 0.12 ± 0.09 mm, myopia progression was 0.26 ± 0.27 D, and corneal power change was 0.05 ± 0.10 D per 6 months, whereas in children with an average of 1681 ± 24 hours of daylight, axial eye growth was 0.19 ± 0.10 mm, myopia progression was 0.32 ± 0.27 D, and corneal power change was -0.04 ± 0.08 D per 6 months. Eye elongation and myopia progression seem to decrease in periods with longer days and to increase in periods with shorter days. Children should be encouraged to spend more time outside during daytime to prevent myopia. The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Comparison of the Refractive Results Measured by Ultrasound and Partial Coherence Interferometers

Comparison of the Refractive Results Measured by Ultrasound and Partial Coherence Interferometers

Seasonal variation in myopia progression and axial elongation: an evaluation of Japanese children participating in a myopia control trial

To investigate the seasonal variations in myopia progression and axial elongation in Japanese children. Ninety-two children who were enrolled in a myopia-control trial and wearing single vision or progressive addition lenses were included in the analyses (mean ± SD age 11.4 ± 1.7 years, mean spherical equivalent refractive error -4.40 ± 1.38 D). Refractive error and axial length were measured every 6 months for 1.5 years by non-cycloplegic autorefraction and partial coherence interferometer, respectively. Myopia progression and axial elongation for each 6-month interval were calculated by subtracting the measure at the end of the interval from that at the beginning. Seasons were classified as summer, winter or others, based on mid-day of the 6-month period between visits. Myopia progression was not significantly influenced by the season. After adjusting study groups (type of spectacles), years and age at the baseline, the mean (±SE) myopia progression was 0.35 ± 0.04 D for summer, 0.28 ± 0.06 D for winter and 0.38 ± 0.04 D for the others. In contrast, axial elongation was significantly influenced by the season, and the mean axial elongation was 0.137 ± 0.010 mm for summer, 0.170 ± 0.013 mm for winter and 0.163 ± 0.008 mm for the others. The seasonal variation in axial elongation, however, was smaller than that previously reported overseas. In Japanese children myopia progression did not slow in summer. Although axial elongation slightly decreased in summer, myopia progression seems to be fairly stable throughout the year.

Comparison of Ocular Biometry Measured by Ultrasound and Two Kinds of Partial Coherence Interferometers

Comparison of Ocular Biometry Measured by Ultrasound and Two Kinds of Partial Coherence Interferometers