Inter-device reproducibility of the scanning laser polarimeter with variable cornea compensation

Blumenthal, Eytan Z.; Frenkel, Shahar

doi:10.1038/sj.eye.6701472

Cited by 20 publications

(15 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…SLP was shown to be a highly reproducible imaging technique of the RNFL. [9][10][11] After experience with the GDx-VCC accumulated, it became apparent that an additional SLP anomaly, which is likely unrelated to corneal compensation, appears in a small proportion of scanned individuals. 12 This SLP anomaly, or artefact, became known as an atypical birefringence pattern (ABP), and consequently has been addressed by the manufacturer via a typical scan score (TSS) score (on a scale of 0-100), such that normal patterns score high, while ABP scans score low.…”

Section: Introductionmentioning

confidence: 99%

Clinical characteristics of eyes demonstrating atypical patterns in scanning laser polarimetry

Orlev

Horani

Rapson

et al. 2007

Eye

Self Cite

View full text Add to dashboard Cite

Purpose To characterize which clinical features are associated with the occurrence of atypical birefringence patterns (ABP) occasionally seen with scanning laser polarimetry (SLP). Methods Sixty-one subjects, including glaucoma patients, glaucoma suspects, and normal subjects, underwent a full clinical examination, standard visual field (VF) test, and a GDx-VCC SLP examination. One eye was selected from each patient. The magnitude of ABP was determined in two independent ways: using a support vector machine analysis (typical scan score (TSS)) and by a masked experienced observer. We assessed whether the magnitude of ABP was correlated with age, gender, the refractive state of the eye, corneal polarization axis and magnitude, GDx global parameters (TSNIT and NFI), and the VF status, as evident from glaucoma hemifield test (GHT), mean deviation (MD), and the pattern standard deviation (PSD). Results Of the 61 study eyes, 27 (44%) showed an ABP, based on a TSS cutoff (o82.5). A very high correlation was found between the TSS score and the masked experienced observer score (r 2 ¼ 0.80; Po0.001). The following clinical parameters were found, on bivariate analysis, to be significantly correlated with the presence of an ABP: age (r 2 ¼ 0.086; P ¼ 0.02); corneal polarization magnitude (r 2 ¼ 0.069; P ¼ 0.04); TSNIT (r 2 ¼ 0.16; Po0.001). Conclusion The presence and magnitude of ABP did not seem to be closely correlated with most clinical parameters. A low, but statistically significant, correlation was found for age and corneal polarization magnitude (r 2 ¼ 0.086 and 0.069, respectively). A lowmedium correlation was found for TSNIT (r 2 ¼ 0.16); however, we speculate that this might represent a confounding effect, rather than an underlying association. We conclude that none of the clinical parameters investigated in this study appears to be strongly correlated with the presence of an ABP on SLP scans performed using the commercially available GDx-VCC.

show abstract

Section: Introductionmentioning

confidence: 99%

Clinical characteristics of eyes demonstrating atypical patterns in scanning laser polarimetry

Orlev

Horani

Rapson

et al. 2007

Eye

Self Cite

View full text Add to dashboard Cite

show abstract

“…This parameter is a support vector machine algorithm, automatically provided by the device software, and calculated combining information from many different parameters. In previous reports NFI displayed moderate to low reproducibility levels [27, 29]. We may postulate that even slight intersession differences for those parameters may influence NFI value through a summation effect.…”

Section: Discussionmentioning

confidence: 99%

“…Overall results were fair to good. The most recent version of SLP, coupled with a variable corneal compensator, has been evaluated in terms of interdevice reproducibility and reliability of measures [27], interoperator reproducibility and any operator learning effect in 15 normal and 15 glaucomatous patients [28] and intraobserver reproducibility in healthy eyes and eyes with ocular hypertension [29]. To our knowledge, evaluation of intersession reproducibility is lacking.…”

Section: Discussionmentioning

confidence: 99%

“…Reproducibility of measurements with older versions of GDx have previously been assessed in detail [17,18,19,20,21,22,23,24,25,26]. More recently a few papers evaluated GDx-VCC interdevice [27], intraoperator [28] or intraobserver reproducibility [29]. The aim of this study is to evaluate intersession reproducibility of RNFL thickness measurements caught by GDx-VCC in a sample of healthy subjects and glaucomatous patients.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Intersession Reproducibility of Retinal Nerve Fiber Layer Thickness Measurements by GDx-VCC in Healthy and Glaucomatous Eyes

et al. 2006

View full text Add to dashboard Cite

Background: To assess intersession reproducibility of retinal nerve fiber layer (RNFL) thickness measurements on scanning laser polarimetry with variable corneal compensation (GDx-VCC) in a sample of healthy subjects and glaucoma patients. Methods: One eye each from 29 healthy and 29 glaucomatous subjects was selected and underwent RNFL scanning by the same operator at baseline and 1 week later. Glaucoma diagnosis relied on the presence of a reproducible defect on automated perimetry. GDx-VCC parameters considered were those available on page 1 of the printout [TSNIT average and standard deviation (SD), superior and inferior average (SA, IA), Nerve Fiber Indicator]. Reproducibility was assessed by calculating coefficient of variation and intraclass correlation coefficient separately for the two groups and for each parameter. The percentage of eyes with an intersession difference in thickness parameters of more than 5% was also calculated. Results: Coefficient of variation was <6% for TSNIT average, SA and IA in both groups. Corresponding values for TSNIT SD in healthy subjects and in glaucoma patients were 13.7 and 11.4%, respectively, whereas for Nerve Fiber Indicator they were 82.9 and 13.3%. Intraclass correlation coefficient ranged from 0.794 to 0.907 in healthy subjects and from 0.924 to 0.972 in glaucoma patients. In healthy subjects, TSNIT average, SA and IA intersession difference was 5% or less in 55–69% of eyes, whereas the value for TSNIT SD was 34.5%. Corresponding values in glaucomatous eyes ranged from 69 to 79.3% for TSNIT average, SA and IA and was 37.9% for TSNIT SD. Conclusions: Intersession reproducibility of RNFL thickness measurements on GDx-VCC is high, both in healthy and in glaucomatous eyes. In a few cases, however, intersession variation may be larger than 10%. Caution is necessary while interpreting these changes during follow-up, in order to separate physiological variability from real RNFL thickness variations.

show abstract

“…17 Some have reported that pupillary size does not affect the statistical evaluation of the parameters associated with polarimetric assessment of the peripapillary RNFL thickness. 18 This observation suggests that under the conditions of their experiment, the reproducibility of the GDx peripapillary RNFL measurements may be insufficient to identify the effect of pupil size on the retardation measurement. Others indicate that nerve fibre layer measurements with the GDx (without corneal compensation) are influenced by drugs affecting pupillary diameter.…”

Section: Eyementioning

confidence: 98%

Accuracy of GDx variable corneal compensation polarization measurements in normal human eyes: effect of accommodation, cycloplegia, focus, pupil size, and eye selection on reproducibility

Levy¹,

Schachar²

2005

Eye

View full text Add to dashboard Cite

Accuracy of GDx variable corneal compensation polarization measurements in normal human eyes: effect of accommodation, cycloplegia, focus, pupil size, and eye selection on reproducibility NS Levy and IH Schachar AbstractPurpose To evaluate the reproducibility of variable corneal compensation (VCC) and the effect of accommodation, cycloplegia, eye selection, focus, and pupil size on this measurement of polarization. Methods Using a GDx scanning laser polarimeter, multiple measurements of the VCC were obtained from each eye of 33 healthy, young adults under differing conditions. Pupil size and refraction were independently measured with a pupillometer and an autorefractometer. The effects of eye, instrument focus, pupil diameter, cycloplegia, and accommodation were statistically assessed.Results The reproducibility of a single retardation measurement and its axis, as determined by the standard deviations (SD) of repeated measurements, is 71.58 nm and 2.101, respectively. There is a difference in retardation between right and left eyes, of 5.2679 nm, P ¼ 0.002. Increasing pupil size increases retardation. Cycloplegia or defocusing decreases retardation, and pharmacologically induced accommodation has no effect on retardation. Conclusions The retardation and its axis are highly reproducible measurements when the pupil is of physiologic size and the GDx is properly focused. There is a consistent difference in VCC retardation between the paired right and left eyes. This difference may reflect equipment-induced measurement artefact and/or an anatomic asymmetry between the paired eyes of the subjects studied. Clinicians should be cautious when comparing interocular VCC measurements between paired right and left eyes and using data pooled from both eyes for age-adjusted, normalized standards.

show abstract

Inter-device reproducibility of the scanning laser polarimeter with variable cornea compensation

Cited by 20 publications

References 16 publications

Clinical characteristics of eyes demonstrating atypical patterns in scanning laser polarimetry

Clinical characteristics of eyes demonstrating atypical patterns in scanning laser polarimetry

Intersession Reproducibility of Retinal Nerve Fiber Layer Thickness Measurements by GDx-VCC in Healthy and Glaucomatous Eyes

Accuracy of GDx variable corneal compensation polarization measurements in normal human eyes: effect of accommodation, cycloplegia, focus, pupil size, and eye selection on reproducibility

Contact Info

Product

Resources

About