Foundations of Clinical Research: Applications to Practice, 2nd Edition, Leslie Gross Portney, Mary P. Watkins. Prentice Hall, Upper Saddle River, NJ (2000), 752 pages. $60

Purpose To evaluate the repeatability and reproducibility of a newer swept-source optical biometer and to compare it with a standard partial coherence interferometry (PCI) biometer. Setting Siriraj Hospital, Mahidol University, Bangkok, Thailand. Design Prospective comparative study. Methods One hundred eyes from 100 cataract patients were enrolled in this study. Each patient was measured with 2 optical biometers, a newer swept-source optical biometer (IOLMaster 700) and a standard partial coherence interferometry biometer (IOLMaster 500) by 2 independent operators. The keratometry, axial length (AL), anterior chamber depth, white-to-white corneal diameter, and intraocular lens (IOL) power, calculated by the SRK/T and the Haigis formulas for each device, were recorded. Intraoperator repeatability and interoperator reproducibility of both devices were analyzed using intraclass correlation coefficients (ICCs). Agreement of ocular biometry and IOL power between the 2 devices was evaluated using the Bland-Altman method. Results The repeatability and reproducibility of the swept-source and standard biometers were high for all ocular biometry parameters (ICC, 0.93-1.00). The agreement between the 2 biometers was also high (ICC, 0.92-1.00). The IOL powers obtained from both devices were not distinct. Because of the density of the cataracts, the AL in 5 eyes could be measured only by the swept-source biometer. Conclusions Repeatability and reproducibility of a swept-source optical biometer was excellent and agreement with a standard biometer was very high. Better lens penetration ability and AL measurements were obtained with the swept-source biometer than with the standard biometer. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Clinical comparison of a new swept-source optical coherence tomography–based optical biometer and a time-domain optical coherence tomography–based optical biometer

Ophthalmology is a technologically advancing field with the constant production of new instrumentation. Instruments are usually released on the market with manufacturers claiming performance in various data formats, and this is typically followed by clinical evaluation studies by independent users. Ubiquitous issues in this area include, not least, the variety of methods, both practically and statistically, and the various terminology differences. It is becoming exceedingly difficult for clinicians and researchers to make sense of study results that have used nonstandard methodology in addition to confounding terminology. Terms such as consistency, precision, reliability, accuracy, repeatability, reproducibility, and agreement are just some examples of the many terms that frequently appear in the ophthalmic literature with inconsistent definitions and synonymous usage. The purpose of this editorial is to provide guidance to prospective authors conducting precision (repeatability and reproducibility) studies in terms of basic concepts, terminology, statistical methods, sample size considerations, study design, use of 1 eye or 2 eyes, and worked examples. A number of bodies in the scientific world have devised their own terminology and statistical recommendations, some of which are similar and others markedly different. An example is the International Organization for Standardization (ISO), an independent nongovernmental membership organization and the world's largest developer of voluntary International Standards. ISO has published more than 20 500 International Standards covering almost every industry, including ophthalmology. Examples include standards relating to contact lenses, contact lens care products, intraocular lenses, intraocular implants, spectacle lenses, and ophthalmic instruments. The ISO standardsmight differ markedly even within ophthalmic instruments, an example being differing statistical methods for tonometry and topography. A full list is available on the ISOwebsite (www.iso.org). Such ISO standards are developed by following a formal methodology involving a multi-stakeholder process. They are organic and dynamic, and developments might take years. This editorial is not set to replace any of the ISO standards or suggest that a single approach should be applied to every situation but rather provides a practical commentary on precision that draws

Precision (repeatability and reproducibility) studies and sample-size calculation

Purpose To evaluate the effects of tear osmolarity on the repeatability of keratometry (K) measurements in patients presenting for cataract surgery. Setting Three clinical practices. Design Observational prospective nonrandomized study. Methods Subjects were prospectively recruited based on tear osmolarity (Tearlab Osmolarity System); that is, osmolarity more than 316 mOsm/L in at least 1 eye (hyperosmolar) and osmolarity less than 308 mOsm/L in both eyes (normal). The baseline K value was measured, and a second measurement was taken on the same instrument (IOLMaster) within 3 weeks of the first. Variability in average K, calculated corneal astigmatism using vector analysis, and intraocular lens (IOL) sphere power calculations were compared between groups. Results The hyperosmolar group (50 subjects) had a statistically significantly higher variability in the average K reading (P = .05) than the normal group (25 subjects) and a statistically significantly higher percentage of eyes with a 1.0 diopter (D) or greater difference in the measured corneal astigmatism (P = .02). A statistically significantly higher percentage of eyes in the hyperosmolar group had an IOL power difference of more than 0.5 D (P = .02). No statistically significant differences were present when the subjects were grouped by self-reported dry eye. Conclusions Significantly more variability in average K and anterior corneal astigmatism was observed in the hyperosmolar group, with significant resultant differences in IOL power calculations. Variability was not significantly different when subjects were grouped by self-reported dry eye. Measurement of tear osmolarity at the time of cataract surgery planning can effectively identify patients with a higher likelihood of high unexpected refractive error resulting from inaccurate keratometry. Financial Disclosure Drs. Epitropoulos, Matossian, Berdy, and Malhotra received compensation from Tearlab for participating in the study. No author has a financial or proprietary interest in any material or method mentioned.

Effect of tear osmolarity on repeatability of keratometry for cataract surgery planning.

Comparison of Axial Length, Corneal Curvature, and Anterior Chamber Depth Measurements of 2 Recently Introduced Devices to a Known Biometer

Purpose To compare the repeatability and reproducibility of ocular biometry and intraocular lens (IOL) power obtained with a new optical biometer (AL-Scan) and a standard optical biometer (IOLMaster 500). Setting Siriraj Hospital, Mahidol University, Bangkok, Thailand. Design Prospective comparative study. Methods Two independent operators measured eyes with cataract using both biometers. The keratometry values, axial length, anterior chamber depth, white-to-white (WTW) corneal diameter, and IOL power calculated using the Holladay 1 formula obtained with each device were recorded. Intraoperator repeatability and interoperator reproducibility of both devices were analyzed using the intraclass correlation coefficient (ICC). The agreement in ocular biometry and IOL power between the 2 devices was evaluated by the Bland-Altman method. Results The study recruited 137 eyes of 81 patients. The repeatability and reproducibility of both devices were high for all ocular biometry measurements (ICC, 0.87-1.00). Except for the WTW corneal diameter (ICC, 0.44), the agreement between the biometers was also high (ICC, 0.98-0.99). The IOL powers calculated by the Holladay 1 formula were similar between the 2 biometers. Conclusion The new optical biometer provided excellent repeatability and reproducibility for all ocular biometry. Agreement with the standard optical biometer was good except for the WTW corneal diameter. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

https://www.nidek-intl.com/archives/004/201411/55a8a25884bbb.pdf

Comparison of ocular biometry and intraocular lens power using a new biometer and a standard biometer.

Purpose To compare the corneal astigmatism (magnitude and axis location) derived by total corneal power (TCP), automated keratometry, and simulated keratometry. Setting Siriraj Hospital, Mahidol University, Bangkok, Thailand. Design Prospective comparative study. Methods Eyes with previous ocular surgery or abnormalities were excluded. All patients were examined with the ARK 730A autokeratometer and the Galilei analyzer. The steepest and flattest corneal power along with the steepest axis of the TCP, automated keratometry, and simulated keratometry were recorded. Vector analysis (J0 and J45) was calculated. Analysis of variance with Bonferroni correction was performed for multiple comparisons. Outcome measures were the magnitude and axis location of astigmatism. Results One hundred eyes of 100 cataract patients were randomly selected. There was no statistically significant difference in the mean steepest axis between TCP (93.31 ± 68.75 [SD]), automated keratometry (94.24 ± 64.78), and simulated keratometry (92.42 ± 64.30). However, the mean magnitude of astigmatism measured by TCP (1.23 ± 0.75) was significantly higher than that measured by automated keratometry (0.93 ± 0.68) ( P =.01) but not than that measured by simulated keratometry (1.08 ± 0.68) ( P =.43); there was no statistically significant difference in J0 or J45. Twenty two (40%) of 54 eyes with more than 1.00 diopter of TCP astigmatism had more than 10 degrees of axis difference from automated keratometry. Conclusions The magnitude of TCP astigmatism was higher than that of automated keratometry. The axis location was similar. However, there was more than 10 degrees of axis difference between automated keratometry and TCP in patients with high astigmatism. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Comparison of corneal astigmatism and axis location in cataract patients measured by total corneal power, automated keratometry, and simulated keratometry.

Purpose To compare the central corneal thickness (CCT) measurements in subjects with corneal edema using ultrasound pachymetry, Visante anterior-segment optical coherence tomography (OCT), Cirrus OCT, and Pentacam Scheimpflug camera tomography. Methods This prospective cross-sectional study included 46 eyes of 33 patients with corneal edema and a CCT exceeding 550 μm evaluated by ultrasound pachymetry, Visante OCT, Cirrus OCT, and Pentacam. Two observers measured each eye twice. Intraobserver and interobserver reproducibility were determined and agreement among the devices calculated. Results CCT was measured in 40 eyes of 29 patients. Regardless of the CCT, the measurements obtained using Visante OCT, Cirrus CCT, and ultrasound pachymetry were well correlated. Interobserver and intraobserver reproducibility were high among the three devices. Pentacam overestimated the results compared with the other devices, and ultrasound pachymetry was unmeasurable in six (13%) eyes with very thick and opaque corneas. In eyes with mild corneal edema (CCT 551-650 μm), measurements from the four devices were comparable. Conclusion All devices reliably measured the CCT <650 μm. In eyes with edema exceeding 650 μm, CCT measurements from the Visante OCT, Cirrus OCT, and ultrasound pachymetry devices showed good reproducibility and were well correlated, while the Pentacam overestimated the values compared to the other devices. Pentacam and ultrasound pachymetry should not be used in eyes with extreme corneal edema and opacity.

/pdf/comparison-of-central-corneal-thickness-measurements-in-3w41mb9s8g.pdf

Comparison of central corneal thickness measurements in corneal edema using ultrasound pachymetry, Visante anterior-segment optical coherence tomography, Cirrus optical coherence tomography, and Pentacam Scheimpflug camera tomography.

Pratuangsri Chonpimai

Papers

Clinical comparison of a new swept-source optical coherence tomography–based optical biometer and a time-domain optical coherence tomography–based optical biometer

Comparison of ocular biometry and intraocular lens power using a new biometer and a standard biometer.

Comparison of corneal astigmatism and axis location in cataract patients measured by total corneal power, automated keratometry, and simulated keratometry.

Comparison of central corneal thickness measurements in corneal edema using ultrasound pachymetry, Visante anterior-segment optical coherence tomography, Cirrus optical coherence tomography, and Pentacam Scheimpflug camera tomography.

Tear film change and ocular symptoms after reading printed book and electronic book: a crossover study