Statistical strategies to assess reliability in ophthalmology

Evaluation of a visual acuity eHealth tool in patients with cataract

PURPOSE

To validate the Easee web-based tool for the assessment of visual acuity in patients who underwent cataract surgery.

SETTING

University Eye Clinic Maastricht, Maastricht, the Netherlands.

DESIGN

Prospective method comparison study.

METHODS

Subjects aged between 18 and 69 years who underwent cataract surgery on 1 or both eyes at the Maastricht University Medical Center+ were eligible to participate in this study. The uncorrected (UDVA) and corrected distance visual acuity (CDVA) assessments were performed using the web-based tool (index test) and conventional ETDRS and Snellen charts (reference tests). The outcomes of the different tests were expressed in logMAR, and a difference of <0.15 logMAR was considered clinically acceptable.

RESULTS

46 subjects with 75 operated eyes were included in this study. The difference of the UDVA between the web-based tool and ETDRS or Snellen was -0.05 ± 0.10 logMAR ( P < .001 [0.15; -0.26]) and -0.04 ± 0.15 logMAR ( P = .018 [0.24; -0.33]), respectively. For the CDVA, these differences were -0.04 ± 0.08 logMAR ( P < .001 [0.13; -0.21]) and -0.07 ± 0.10 logMAR ( P < .001 [0.13; -0.27]), respectively. The Pearson correlation coefficients between the web-based tool and ETDRS were maximally 0.94 and compared with Snellen 0.92. In total, 73% to 88% of the visual acuity measurement differences were within 0.15 logMAR.

CONCLUSIONS

The web-based tool was validated for the assessment of visual acuity in patients who underwent cataract surgery and showed clinically acceptable outcomes in up to 88% of patients. Most of the participants had a positive attitude toward the web-based tool, which requires basic digital skills.

Optical Coherence Tomography Angiography Analysis Toolbox: A Repeatable and Reproducible Software Tool for Quantitative Optical Coherence Tomography Angiography Analysis

BACKGROUND AND OBJECTIVE

The purpose of this article is to demonstrate the optical coherence tomography angiography (OCTA) Analysis Toolkit (OAT), a custom-designed software package, as a repeatable and reproducible tool for computing OCTA metrics across different devices.

MATERIALS AND METHODS

Fourteen participants were imaged using three devices. Foveal avascular zone, vessel index, vessel length index, and vessel diameter index were calculated using the OAT. Repeatability and reproducibility were assessed using the coefficient of variation and interclass correlation coefficient (ICC).

RESULTS

Analysis of identical images demonstrated perfect levels of repeatability for all metrics (coefficient of variation 0%), which was a consequence of the software being deterministic (ie, producing the same outputs for the same inputs). Foveal avascular zone ICC values were in the excellent-to-good range (ICC > 0.6) for all devices. All values for vessel index (VI), vessel length index, and vessel diameter index fell in the good-to-fair (ICC > 0.4) or excellent-to-good range, except for vessel index analysis in the Cirrus device (ICC = 0.34).

CONCLUSIONS

The OAT appears to be a reliable tool that may enable comparison between OCTA data sets acquired on different imaging instruments, thereby facilitating a more consistent approach to OCTA analysis. [Ophthalmic Surg Lasers Imaging Retina 2023;54:114-122.].

FIBER-ML, an Open-Source Supervised Machine Learning Tool for Quantification of Fibrosis in Tissue Sections

Pathologic fibrosis is a major hallmark of tissue insult in many chronic diseases. Although the amount of fibrosis is recognized as a direct indicator of the extent of disease, there is no consentaneous method for its quantification in tissue sections. This study tested FIBER-ML, a semi-automated, open-source freeware that uses a machine-learning approach to quantify fibrosis automatically after a short user-controlled learning phase. Fibrosis was quantified in sirius red-stained tissue sections from two fibrogenic animal models: acute stress-induced cardiomyopathy in rats (Takotsubo syndrome-like) and HIV-induced nephropathy in mice (chronic kidney disease). The quantitative results of FIBER-ML software version 1.0 were compared with those of ImageJ in Takotsubo syndrome, and with those of inForm in chronic kidney disease. Intra- and inter-operator and inter-software correlation and agreement were assessed. All correlations were excellent (>0.95) in both data sets. The values of discriminatory power between the pathologic and healthy groups were <10^-3 for data on Takotsubo syndrome and <10^-4 for data on chronic kidney disease. Intra-operator agreement, assessed by intra-class coefficient correlation, was good (>0.8), while inter-operator and inter-software agreement ranged from moderate to good (>0.7). FIBER-ML performed in a fast and user-friendly manner, with reproducible and consistent quantification of fibrosis in tissue sections. It offers an open-source alternative to currently used software, including quality control and file management.

Defining growth in small pulmonary nodules using volumetry: results from a "coffee-break" CT study and implications for current nodule management guidelines

Objectives

An increase in lung nodule volume on serial CT may represent true growth or measurement variation. In nodule guidelines, a 25% increase in nodule volume is frequently used to determine that growth has occurred; this is based on previous same-day, test–retest (coffee-break) studies examining metastatic nodules. Whether results from prior studies apply to small non-metastatic nodules is unknown. This study aimed to establish the interscan variability in the volumetric measurements of small-sized non-metastatic nodules.

Methods

Institutional review board approval was obtained for this study. Between March 2019 and January 2021, 45 adults (25 males; mean age 65 years, range 37–84 years) with previously identified pulmonary nodules (30–150 mm³) requiring surveillance, without a known primary tumour, underwent two same-day CT scans. Non-calcified solid nodules were measured using commercial volumetry software, and interscan variability of volume measurements was assessed using a Bland–Altman method and limits of agreement.

Results

One hundred nodules (range 28–170 mm³; mean 81.1 mm³) were analysed. The lower and upper limits of agreement for the absolute volume difference between the two scans were − 14.2 mm³ and 12.0 mm³ respectively (mean difference 1.09 mm³, range − 33–12 mm³). The lower and upper limits of agreement for relative volume difference were − 16.4% and 14.6% respectively (mean difference 0.90%, range − 24.1–32.8%).

Conclusions

The interscan volume variability in this cohort of small non-metastatic nodules was smaller than that in previous studies involving lung metastases of varying sizes. An increase of 15% in nodule volume on sequential CT may represent true growth, and closer surveillance of these nodules may be warranted.

Key Points

• In current pulmonary nodule management guidelines, a threshold of 25% increase in volume is required to determine that true growth of a pulmonary nodule has occurred.

• This test–retest (coffee break) study has demonstrated that a smaller threshold of 15% increase in volume may represent true growth in small non-metastatic nodules.

• Closer surveillance of some small nodules growing 15–25% over a short interval may be appropriate.

Double-Organ Bias in Controlled Trials on Eyelid Ptosis

PURPOSE

Proper statistical analysis is an essential element in the evaluation of clinical trial outcomes. We had the informal observation that double-organ bias was a neglected issue during the statistical analyses of clinical trials on eyelid ptosis. The aim of this study was to formally document the prevalence of this bias in these studies.

METHODS

Clinical trials on eyelid ptosis, published in the last 20 years, were searched in PubMed with the terms; "((blepharoptosis) OR upper eyelid ptosis) OR eyelid ptosis" and with the filters "Randomized Controlled Trial (RCT), Clinical Trial, Humans." Two independent observers evaluated the articles for eligibility, field of the journal, field of the authors, presence of randomization, type of the study (surgical, medical), and statistical approach to double organ bias.

RESULTS

The PubMed search yielded 101 articles and 23 of them met the above-mentioned criteria. In 3 articles, primary outcome measure was not related with the eyes. Among the remaining 20 articles, 14 (70%) had double-organ bias in the statistics. The bias was slightly less common in randomized trials (60% vs. 80%), but the difference was not statistically significant. Its prevalence was similar between ophthalmology journals and the rest (p = 0.64). Interestingly, the bias tended to be more in Q1 journals (87.5%) compared to Q2 and Q3 journals (58.3%) and median impact factor was higher in biased articles (1.82 vs. 1.29), but the differences weren't statistically significant (p = 0.32, p = 0.24). There was no difference between the last 2 decades (66.6% vs. 75%, p = 0.64).

CONCLUSIONS

The prevalence of the double-organ bias was very high in published clinical trials on eyelid ptosis (70%) and even among RCTs (60%). The prevalence of the bias didn't prevent publication in higher impact factor journals and didn't change between journals from different disciplines or over time.

Repeatability and Reproducibility of Macular Hole Size Measurements Using Optical Coherence Tomography

The purpose of this study was to assess the repeatability and reproducibility of measuring the minimum linear diameter (MLD) of macular holes (MHs) using horizontal linear and radial scan modes in optical coherence tomography (OCT). Patients with concurrent sets of radial and horizontal linear OCT volume scans were included. The MLD was measured twice in both scan modes by six raters of three different experience levels (groups). Outcome measures were the reliability and repeatability of MLD measurements. Fifty patients were included. Mean MLD was 317.21(±170.63) µm in horizontal linear and 364.52 (±161.71) µm in radial mode, a difference of 47.31 (±26.48) µm (p < 0.001). In the radial scan mode, MLD was identified within 15° of the horizontal meridian in 27% and within 15° of the vertical meridian in 26.7%, with the remainder (46.3%) in oblique meridians. The intra-group coefficients of repeatability (CR) for horizontal linear mode were 23 µm, 33 µm and 45 µm, and for radial mode 25 µm, 44 µm and 57 µm for groups 1, 2 and 3, respectively. The inter-group CR, taking group 1 as reference standard for groups 2 and 3, were 74 µm and 71 µm for the linear mode, and 62 µm and 78 µm for radial mode. The radial mode provides good repeatability and reliability for measurement of MLD. In a majority of cases the MLD does not lie in the horizontal meridian and would be underestimated using a horizontal OCT mode.

Analysis of Choroidal Vascularity Index in Keratoconus Patients Using Swept-Source Optical Coherence Tomography-Based Binarization Techniques

PURPOSE

To analyse the vascular density of the choroid in a keratoconus (KC) population using swept-source optical coherence tomography (SS-OCT).

METHODS

Prospective, noninterventional study that analysed 97 eyes from 52 KC patients and 145 eyes from 89 healthy controls. The sample was divided in four different age groups. Inclusion criteria were topographic diagnosis of KC using Pentacam, axial length shorter than 26 mm, good quality of the images, and no other systemic or ocular diseases. A 12 mm horizontal single-line SS-OCT b-scan was performed to create a choroidal thickness (CT) profile. Validated automated segmentation and binarization were used in order to analyse choroidal, stromal, and vascular areas.

RESULTS

The percentage of choroidal vascularity (vascular area/total area) was 56.6% in KC patients vs. 49.4% in controls. Aged-adjusted choroidal, stromal, and vascular areas and corrected choroidal percentage of vascularity are statistically increased in KC patients when compared with healthy controls (p < 0.001). All these parameters show a decreasing trend with age. Both stromal and vascular areas were thicker in KC patients (p < 0.001).

CONCLUSIONS

Choroidal, stromal, and vascular areas and corrected choroidal percentage of vascularity are statistically increased in KC patients when compared with healthy controls. All these parameters tend to decrease with age.

How Big is the Hole? Measuring Intra- and Inter-Individual Agreement in Macular Hole Size Measurements

PURPOSE

The size of a macular hole helps determine treatment planning and postoperative prognosis. The aim of this study was to examine intra- and inter-individual agreement in the measurement of full thickness macular hole (FTMH) size using optical coherence tomography (OCT) images.

METHODS

Thirty OCT scans of FTMHs were reviewed by three vitreoretinal consultants and three vitreoretinal fellows. The FTMH size was recorded by each clinician independently and they repeated the measurements 3 weeks later. The repeatability of measurements was analysed using techniques of agreement measurement.

RESULTS

The Coefficients of Repeatability (CR) for the intra-individual agreement were 46 µm, 73 µm and 60 µm for the consultant group and 44 µm, 60 µm and 57 µm for the fellow group. The Coefficients of Variation (CoV) of intra-individual repeatability were 3.8%, 5.9%, and 5.1% for the consultants and 3.5%, 5.2%, and 4.9% for the fellows. The CR for inter-individual agreement varied from 62 µm to 122 µm. There was no significant difference in repeatability of measurements between the consultant and the fellow groups (chi-squared, p = .95).

CONCLUSIONS

Manual OCT FTMH diameter measurements show poor intra- and inter-individual repeatability. Future work should aim to develop an automated method for measuring macular holes.

Changes in symmetry of anterior chamber following routine cataract surgery in non-glaucomatous eyes

Background

To assess minimum and maximum changes in anterior chamber dimensions following routine cataract surgery in non-glaucomatous eyes.

Methods

Forty-two eyes (42 participants) underwent routine cataract surgery with same surgeon and were assessed preoperatively, 1, 3, 6 and 12 months postoperatively. Primary outcome measure: Angle-to-angle diameter (AAD) (at 0-180^o, 45-225^o, 90-270^o, 135-315^o), Anterior-chamber-angle (ACA) (at 0^o, 45^o, 90^o, 135^o, 180^o, 225^o, 270^o and 315^o) and central anterior chamber depth (ACD) at all visits. Secondary outcome measures: relationship to axial length (AL).

Results

The mean AAD and ACA increased post-operatively in all meridians at all visits postoperatively. At 12 months, there was a maximum change in AAD in horizontal meridian (506.55 ± 468.71 μm) and least in vertical meridian (256.31 ± 1082.3 μm). The mean percentage increase in ACA postoperatively was least at 90^o (5% increase compared to 29–35% elsewhere). Central ACD deepened at all postoperative visits and this did not change over 12 months. There was no correlation between AAD, ACA and ACD with AL at any visit.

Conclusion

The AAD, ACA and ACD increases following cataract surgery in non-glaucomatous eyes, but at 12 months increase in AAD is least in vertical compared to horizontal meridian. Also, ACA was narrower (only 5% increase) superiorly compared to elsewhere (29–35% increase in ACA). This may have implications with regards to surgeries performed in the anterior chamber and corneal endothelial cell loss.

Fast Measure of Visual Acuity and Contrast Sensitivity Defocus Curves with an iPad Application

Objective:

To evaluate the repeatability of the fast measurement of the visual acuity (VADC) and contrast sensitivity (CSDC) defocus curves with a new test as well as the agreement of measurements at far distance obtained with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and the ClinicCSF test for measuring Contrast Sensitivity Function (CSF).

Method:

Records from fifty-nine subjects implanted with Multifocal Intraocular Lenses (MIOLs) were retrieved from our database. VADC and CSDC were measured from +1.00 D to -4.00 D in 0.50 D steps. The agreement with the ETDRS and the CSF at far distance was assessed in comparison to the 0 D location of the VADC and the CSDC, respectively. The repeatability was evaluated in 34 subjects who consecutively repeated two measures.

Results:

Median Visual Acuity (VA) was -0.1 logMAR with the VADC at 0 D of defocus and 0 logMAR with the ETDRS (p>0.05). A total of 45.8% of eyes showed no differences between both tests and the difference was less than one line of VA in 96.6% of the eyes. The intrasubject repeatability was under one line of VA along all the defocus curve except for positive defocus levels. The CSDC showed the best agreement with the CSF for 18 cycles per degree. The CSDC was less repeatable than VADC. Mean time spent on completing the VADC and CSDC was 7.81 and 7.98 minutes, respectively.

Conclusion:

The VADC showed good agreement with the ETDRS and good repeatability despite the short testing time. In contrast, poorer repeatability was found for CSDC. Our method would facilitate the inclusion of VADC in clinical practice as it is a fast test, being also the first one including the measure of CSDC.

Reproducibility of corneal, macular and retinal nerve fiber layer thickness measurements using the iVue-100 optical coherence tomography

Purpose

To determine the intra-session and inter-session reproducibility of corneal, macular and retinal nerve fiber layer thickness (RNFL) measurements with the iVue-100 optical coherence tomography in normal eyes.

Methods

These parameters were measured in the right eyes of 50 healthy participants with normal vision. Six scans each for corneal thickness, macular and optic nerve head were taken on one day (intra-session), followed by similar repeated measures on five separate days (inter-session). Reproducibility was computed using intra-class correlation coefficient (ICC), coefficient of variation (COV), and test-retest variability (TRV).

Results

For intra-session reproducibility, the ICC, COV and TRV values for mean corneal thickness were 0.924, 2.82%, and 3.06 µm respectively. For the mean macular thickness, they were 0.978, 4.64% and 4.51 µm respectively, while for mean RNFL thickness they were 0.946, 3.19%, and 5.66 µm respectively. Inter-session values for mean corneal thickness were 0.926, 2.65% and 3.48 µm, and 0.916, 2.24% and 2.03 µm for mean macular thickness. For mean RNFL thickness, they were 0.962, 2.21%, and 4.72 µm respectively.

Conclusion

There was good reproducibility of all measured parameters. However, mean RNFL thickness measurements were the most reproducible, suggesting that this may be the best parameter to use to determine measured changes over time.

Double-Organ Bias in Published Randomized Controlled Trials of Glaucoma

PURPOSE

Most of the statistical tests used in significance testing are based on the assumption that each data entry is independent from other entries, however, we observe that in many articles researchers include data from 2 eyes as independent variables while performing these statistical tests. The aim of this study was to formally survey the prevalence of the above-mentioned "double-organ bias" in randomized controlled trials (RCT) of glaucoma.

MATERIALS AND METHODS

We did a PubMed search with the terms "glaucoma" and limitations "Humans" and "Randomized Controlled Trials" in 15 highest-impact-factor ophthalmology journals between November 2002 and November 2012. We only included RCTs published as an original article, where the aim was treating glaucoma. Two independent observers (M.K. and A.S.E.) read through each article and classified the articles according to treatment modality (medical, laser, or surgical) and presence of double-organ bias.

RESULTS

The PubMed search yielded 270 articles. A total of 130 articles qualified for the survey. Eighty-five of the RCTs were medical studies, 11 were laser studies, and 34 studies evaluated the outcome of a surgical procedure. In 17 of the 130 articles (13.1%), double-organ bias was found. Prevalence of the double-organ bias was not significantly different between medical (12.9%), laser (14.7%), and surgical (9.1%) studies.

CONCLUSION

Double-organ bias was observed around 13.1% of the published RCTs, leading to inaccurate statistical testing.

Lateral thinking - Interocular symmetry and asymmetry in neurovascular patterning, in health and disease

No biological system or structure is likely to be perfectly symmetrical, or have identical right and left forms. This review explores the evidence for eye and visual pathway asymmetry, in health and in disease, and attempts to provide guidance for those studying the structure and function of the visual system, where recognition of symmetry or asymmetry may be essential. The principal question with regards to asymmetry is not 'are the eyes the same?', for some degree of asymmetry is pervasive, but 'when are they importantly different?'. Knowing if right and left eyes are 'importantly different' could have significant consequences for deciding whether right or left eyes are included in an analysis or for examining the association between a phenotype and ocular parameter. The presence of significant asymmetry would also have important implications for the design of normative databases of retinal and optic nerve metrics. In this review, we highlight not only the universal presence of asymmetry, but provide evidence that some elements of the visual system are inherently more asymmetric than others, pointing to the need for improved normative data to explain sources of asymmetry and their impact on determining associations with genetic, environmental or health-related factors and ultimately in clinical practice.

Development and testing of an automated computer tablet-based method for self-testing of high and low contrast near visual acuity in ophthalmic patients

PURPOSE

Many eye diseases require on-going assessment for optimal management, creating an ever-increasing burden on patients and hospitals that could potentially be reduced through home vision monitoring. However, there is limited evidence for the utility of current applications and devices for this. To address this, we present a new automated, computer tablet-based method for self-testing near visual acuity (VA) for both high and low contrast targets. We report on its reliability and agreement with gold standard measures.

METHODS

The Mobile Assessment of Vision by intERactIve Computer (MAVERIC) system consists of a calibrated computer tablet housed in a bespoke viewing chamber. Purpose-built software automatically elicits touch-screen responses from subjects to measure their near VA for either low or high contrast acuity. Near high contrast acuity was measured using both the MAVERIC system and a near Landolt C chart in one eye for 81 patients and low contrast acuity using the MAVERIC system and a 25 % contrast near EDTRS chart in one eye of a separate 95 patients. The MAVERIC near acuity was also retested after 20 min to evaluate repeatability.

RESULTS

Repeatability of both high and low contrast MAVERIC acuity measures, and their agreement with the chart tests, was assessed using the Bland-Altman comparison method. One hundred and seventy-three patients (96 %) completed the self- testing MAVERIC system without formal assistance. The resulting MAVERIC vision demonstrated good repeatability and good agreement with the gold-standard near chart measures.

CONCLUSIONS

This study demonstrates the potential utility of the MAVERIC system for patients with ophthalmic disease to self-test their high and low contrast VA. The technique has a high degree of reliability and agreement with gold standard chart based measurements.

Comparison of blood pressure measurements of anesthetized dogs obtained noninvasively with a cylindrical blood pressure cuff and an anatomically modified conical blood pressure cuff

OBJECTIVE

To compare blood pressure measured noninvasively with an oscillometric device that involved use of a novel conical cuff and a traditional cylindrical blood pressure cuff.

ANIMALS

17 adult hound-type dogs.

PROCEDURES

Dogs were anesthetized, and a 20-gauge, 1.5-inch catheter was inserted in the median sacral artery. The catheter was attached to a pressure transducer via fluid-filled noncompliant tubing, and direct blood pressure was recorded with a multifunction monitor. A specially fabricated conical cuff was placed on the antebrachium. Four sets of direct and indirect blood pressure measurements were simultaneously collected every 2 minutes. Four sets of measurements were then obtained by use of a cylindrical cuff.

RESULTS

The cylindrical cuff met American College of Veterinary Internal Medicine consensus guidelines for validation of indirect blood pressure measurements for mean arterial blood pressure (MAP), systolic arterial blood pressure (SAP), and diastolic arterial blood pressure (DAP). The conical cuff met the consensus guidelines for difference of paired measurements, SD, and percentages of measurements within 10 and 20 mm Hg of the value for the reference method, but it failed a correlation analysis. In addition, although bias for the conical cuff was less than that for the cylindrical cuff for SAP, MAP, and DAP measurements, the limits of agreement for the conical cuff were wider than those for the cylindrical cuff for SAP and MAP measurements.

CONCLUSIONS AND CLINICAL RELEVANCE

On the basis of results of this study, use of a conical cuff for oscillometric blood pressure measurement cannot be recommended.

Repeatability and accuracy of applanation resonance tonometry in healthy subjects and patients with glaucoma

PURPOSE

To evaluate the repeatability and accuracy of the applanation resonance tonometer (ART) used in the automatic servo-controlled version, and to evaluate the influence of central corneal thickness (CCT) on the ART intraocular pressure (IOP) measurements.

METHODS

This prospective, randomized, single-centre study included one eye of 153 subjects (35 healthy volunteers and 118 patients with glaucoma). All participants underwent ultrasonic CCT measurement, followed by IOP evaluation with Goldmann applanation tonometer (GAT) and ART in random order. A single operator measured the IOP with each tonometer three times. Intra-examiner variability was evaluated using the coefficient of variation (CoV), intraclass correlation coefficient (ICC) and test-retest differences. Intermethod agreement was assessed using the Bland-Altman method. Linear regression analysis was used to evaluate the relationship between IOP measurements and CCT.

RESULTS

The mean IOP was 17.7 ± 4.4 mmHg with GAT and 20.6 ± 5.3 mmHg with ART (p < 0.001). CoV and ICC were, respectively, 5 ± 3% and 0.99 for GAT, and 8 ± 4% and 0.96 for ART (intermethods differences, p = 0.001). The ART test-retest differences significantly increased with increasing mean IOP (p = 0.003). The mean IOP difference (ART minus GAT) was 3.0 ± 4.0 mmHg, which increased with increasing mean IOP (p < 0.001). Both GAT IOP and ART IOP readings were significantly directly related to the CCT values (p = 0.03 and p = 0.004, respectively; intermethods difference, p = 0.32).

CONCLUSIONS

The ART intra-examiner repeatability was excellent, although significantly lower than that of GAT, and decreased at higher IOP levels. ART significantly overestimated GAT IOP measurements, especially at higher IOP range. Both GAT and ART appeared similarly influenced by CCT value.

Assessment of tear film stability in dry eye with a newly developed keratograph

PURPOSE

To investigate the applicability of a newly developed corneal topographer in assessing tear film stability.

METHODS

This is a prospective, case-control study. Forty-four Chinese dry eye patients and 41 normal subjects were recruited. Noninvasive tear film break-up time (NI-BUT) was measured using a new method based on a corneal topographer equipped with modified scan software. The reliability of the measurements was determined. Then, the correlations between the NI-BUT and the traditional fluorescein tear film break-up time, Schirmer I test values, and inferior tear meniscus height measurements were determined. The receiver operating characteristic curve technique was used to evaluate the NI-BUT examination in the diagnosis of dry eye.

RESULTS

In total, a significant difference between the NI-BUT and the fluorescein tear film break-up time was found (3.2 ± 2.3 seconds vs. 5.2 ± 3.4 seconds; P < 0.001). The coefficient of variation and intraclass correlation coefficient values of NI-BUT were 12.8% and 0.93, respectively, for NI-BUT for intraobserver repeatability and 15.4% and 0.88, respectively for interobserver repeatability. The NI-BUT showed a good correlation with other dry eye examinations (all P < 0.05). In addition, the NI-BUT was significantly shorter in dry eye patients (2.0 ± 0.2 seconds) than in normal subjects (4.3 ± 0.3 seconds; P < 0.001). When the cutoff value was set at <2.65 seconds, the sensitivity and specificity of the test were 84.1% and 75.6%, respectively.

CONCLUSIONS

Measurements of NI-BUT obtained with the newly developed corneal topographer may provide a simple, noninvasive screening test for dry eyes with acceptable sensitivity, specificity, and repeatability.

Repeatability and reproducibility of Goldmann applanation, dynamic contour, and ocular response analyzer tonometry

PURPOSE

To evaluate the repeatability and interoperator reproducibility of the Pascal dynamic contour tonometry (DCT), ocular response analyzer (ORA), and Goldmann applanation tonometer (GAT) in a single population of normal individuals.

METHODS

The study included 52 eyes from 26 normal individuals. One operator measured the intraocular pressure (IOP) with each tonometer 3 times while 2 additional operators each measured the IOP with each tonometer once. Repeatability and reproducibility were assessed by the coefficient of variation (CV) and intraclass correlation coefficient (ICC). Agreement among tonometers was also assessed using Bland-Altman plots.

RESULTS

The mean age of included participants was 31.5±8.8 years and 15 (58%) were female individuals. In general, both intraoperator repeatability and interoperator reproducibility were significantly higher for DCT compared with the other tonometers. Intraoperator DCT (CV=3.7, ICC=0.89), GAT (CV=9.7, ICC=0.79), IOPg (CV=7.0, ICC=0.79), and IOPcc (CV=9.8, ICC=0.57). Interoperator DCT (CV=6.1, ICC=0.73), GAT (CV=9.0, ICC=0.82), and IOPg (CV=10.8, ICC=0.63), IOPcc (CV=11.7, ICC=0.49).

CONCLUSION

Overall, DCT was significantly more repeatable and reproducible than GAT, IOPg and IOPcc. The better reproducibility of the DCT may result in more precise measurements for monitoring IOP changes over time compared to GAT and ORA.

Biomechanical studies on transverse olecranon and patellar fractures: a systematic review with the development of a new scoring method

INTRODUCTION

Several methods of transverse patellar and olecranon fixation have been described. This article compares biomechanical studies of various fixation methods using a newly developed scoring method.

SOURCE OF DATA

The databases PubMed, Web of Science, Science Direct, Google Scholar and Google were searched for relevant studies.

AREAS OF AGREEMENT

Fixation hardware failure remains a problem. Various materials and fixation techniques have been tested to provide an improved fixation of transverse olecranon and patellar fractures.

AREAS OF CONTROVERSY

The difference in biomechanical testing setup between the studies makes it hard to compare different fixation techniques.

GROWING POINTS

The newly developed grading method was proved to be unbiased and reliable; however, extra specifications need to be added at some criteria when adopting the scoring method.

AREAS TIMELY FOR DEVELOPING RESEARCH

Non-metallic constructs may provide an improvement to the currently used metallic tension band wiring technique; however, clinical research is required.

Validation of printed and computerised crowded Kay picture logMAR tests against gold standard ETDRS acuity test chart measurements in adult and amblyopic paediatric subjects

AIMS

The impression exists that picture acuity scores may overestimate function when subjects are switched to letter charts. This has not been systematically investigated. The aims of this study were to validate both printed crowded Kay picture (pCKP) and computerised CKP (cCKP) logMAR test acuity measurements against gold standard ETDRS letter chart scores.

METHODS

A total of 30 adult subjects with various ophthalmic disease and 40 amblyopic children underwent test and re-test visual acuity measurements using the ETDRS chart, the pCKP logMAR test, and the cCKP acuity scores taken, using the COMPlog visual acuity measurement system. Bland and Altman methods were employed.

RESULTS

Computerised and printed Kay picture acuity scores agreed well. Both Kay picture test measurements were systematically biased when compared with ETDRS chart measurements. No significant proportional bias was found. The test retest variability (TRV) of all three tests was found to be similar between ± 0.14 and 0.16 logMAR in both groups.

CONCLUSIONS

All three tests were similarly replicable and computerised Kay pictures appear to be a valid alternative to hard copy Kay pictures. Kay picture acuity measurements were systematically biased when compared with the gold standard ETDRS. Measurement error means that differences of up to 0.16 logMAR may be observed in clinically stable patients when re-measured using the same technique. A combination of TRV and systematic bias can however lead to differences of up to 0.40 logMAR in stable amblyopic patients when switched from CKPs to ETDRS chart acuity measurements.

Reproducibility and agreement in evaluating retinal nerve fibre layer thickness between Stratus and Spectralis OCT

PURPOSE

To evaluate intra-device reproducibility of retinal nerve fibre layer (RNFL) measurements obtained using Stratus and Spectralis optical coherence tomography, and to analyze inter-device correlation and agreement for these measurements.

DESIGN

Prospective observational study.

METHODS

A total of 30 normal individuals participated in the study. One eye of each participant was scanned three times during one session by the same operator using Spectralis and Stratus. Intra-class correlation coefficients (ICCs), correlation coefficients (R), and Bland-Altman plots (BAPs) were used to assess reproducibility, correlation, and agreement between the two devices, respectively.

RESULTS

A significant difference in mean RNFL thickness was seen between Stratus and Spectralis (106.2 ± 6.9 μm vs 100.0 ± 7.3 μm, P = 0.0001). ICCs of RNFL thickness measurements ranged from 0.69 (clock hour 2; 95% confidence interval (95% CI): 0.54, 0.85) to 0.91 (inferior quadrant; 95% CI: 0.86, 0.96) for Stratus and were higher for Spectralis, ranging from 0.87 (temporal-superior sector; 95% CI: 0.79, 0.94) to 0.96 (global and nasal-inferior sector; 95% CI: 0.94, 0.99). Rs of RNFL thickness measurements between the two instruments ranged from 0.61 (temporal quadrant) to 0.87 (superior quadrant). BAPs demonstrated a systematic difference in RNFL values between the two devices, with Spectralis producing thinner RNFL values than Stratus.

CONCLUSIONS

Spectralis demonstrated higher ICCs and thinner RNFL measurements than Stratus. Although the inter-device correlation was good, differences in RNFL measurements obtained by the two devices indicate that these measurements would not be interchangeable in clinical evaluations.

Differential expression and distribution of placental glutathione peroxidases 1, 3 and 4 in normal and preeclamptic pregnancy

Preeclampsia is a pregnancy-specific condition affecting 2-7% of women and a leading cause of perinatal and maternal morbidity and mortality; it may also predispose the mother and fetus to increased risks of adult cardiovascular disease. The selenoprotein glutathione peroxidases (GPxs) have critical roles in regulating antioxidant status.

OBJECTIVES, STUDY DESIGN AND MAIN OUTCOME MEASURES

Immunohistochemical measurements of GPx1, GPx3 and GPx4 protein expression were performed on samples taken from three standardised sampling sites between the cord insertion and the periphery of the placenta from 12 normotensive, and 12 preeclamptic women to establish if their expression differed between sampling sites. Total GPx activities were also examined from the three sampling sites of these placentae.

RESULTS

There were highly significant reductions in overall immunohistochemical staining of all 3 GPxs in the preeclampsia compared to normotensive placentae (GPx1: P=0.016; GPx3: P=0.003; GPx4: P<0.001). Furthermore, graded differences in expression between the standardised placental sampling sites were also found for GPx3 (higher in the inner region, P=0.05) and GPx4 (higher in the periphery, P=0.02) but not GPx1. Placental GPx enzyme activity was also significantly reduced in tissue from preeclamptic women as compared to normotensive women (P=0.007; the difference was more pronounced nearest the cord insertion).

CONCLUSIONS

We have shown highly significant reductions in expression of all three major classes of GPx in placentae from women with preeclampsia, and distribution gradients in activity, which may relate to the differential oxygenation of regions of the placenta.

Digital image analysis of plus disease in retinopathy of prematurity

An accurate assessment of retinopathy of prematurity (ROP) is essential in ensuring correct and timely treatment of this potentially blinding condition. Current modes of assessment are based upon clinical grading by expert examination of retinal changes. However, this may be subjective, unreliable and difficult and there has been significant interest in alternative means of measurement. These have been made possible through technological advancements in image capture and analysis as well as progress in clinical research, highlighting the specific importance of plus disease in ROP. Progress in these two fields has highlighted the potential for digital image analysis of plus disease to be used as an objective, reliable and valid measurement of ROP. The potential for clinical and scientific advancement through this method is argued and demonstrated in this article. Along with the potential benefits, there are significant challenges such as in image capture, segmentation, measurement of vessel width and tortuosity; these are also addressed. After discussing and explaining the challenges involved, the research articles addressing digital image analysis of ROP are critically reviewed. Benefits and limitations of the currently published techniques for digital ROP assessment are discussed with particular reference to the validity and reliability of outcome measures. Finally, the general limitations of current methods of analysis are discussed and more diverse potential areas of development are discussed.

The Development, Assessment, and Selection of Questionnaires

Patient-reported outcome measurement has become accepted as an important component of comprehensive outcomes research. Researchers wishing to use a patient-reported measure must either develop their own questionnaire (called an instrument in the research literature) or choose from the myriad of instruments previously reported. This article summarizes how previously developed instruments are best assessed using a systematic process and we propose a system of quality assessment so that clinicians and researchers can determine whether there exists an appropriately developed and validated instrument that matches their particular needs. These quality assessment criteria may also be useful to guide new instrument development and refinement. We welcome debate over the appropriateness of these criteria as this will lead to the evolution of better quality assessment criteria and in turn better assessment of patient-reported outcomes.

Axial length measurement in eyes with diabetic macular edema: a-scan ultrasound versus IOLMaster

OBJECTIVE

To compare axial length (AL) measurements obtained with ultrasound (US) and IOLMaster (software version 3.01.0294; Carl Zeiss Meditec, Jena, Germany) in eyes with diabetic clinically significant macular edema (CSME) and to examine the correlation between measurement difference and foveal thickness.

DESIGN

Prospective nonrandomized clinical study.

PARTICIPANTS

Twenty-three healthy eyes of 23 participants and 21 eyes with CSME of 21 diabetic outpatients.

METHODS

The authors prospectively measured AL using US and IOLMaster in eyes of both groups. Foveal thickness was measured with optical coherence tomography. The difference between both methods was assessed using the t test, and its correlation to foveal thickness was evaluated by Pearson coefficient.

MAIN OUTCOME MEASURE

Difference in AL measurements between IOLMaster and US.

RESULTS

Mean+/-standard deviation foveal thickness in healthy and CSME eyes was 201+/-26 microm (range, 156-240) and 475+/-106 microm (range, 331-758), respectively. Mean AL by US and IOLMaster in healthy eyes was 23.17+/-1.07 mm (range, 21.17-25.18) and 23.25+/-1.10 mm (range, 21.17-25.26), respectively (P = 0.51); in CSME eyes, it was 23.02+/-0.97 mm (range, 21.53-24.81) and 23.27+/-0.924 mm (range, 21.9-25.13), respectively (P<0.001). Correlation between AL difference and foveal thickness was poor in both healthy (r = 0.18, P = 0.40) and CSME (r = 0.02, P = 0.93) eyes.

CONCLUSIONS

Axial length measurements using applanation A-scan US and IOLMaster in eyes with CSME differ statistically and clinically significantly. This is likely a result of the fundamentally different methodology of the 2 methods in measuring eyes with a pathologically thickened retina. A conversion formula based on foveal thickness can not be provided at present.