A Comprehensive Evaluation of the Precision (Repeatability and Reproducibility) of the Oculus Pentacam HR

This article is made available with the permission of the publisher, Association for Research in Vision and OphthalmologyPurpose.: To evaluate the precision (repeatability and reproducibility) of the Pentacam HR (high-resolution) tomographer (Oculus, Wetzlar, Germany) across a large range of measurement parameters. Methods.: A randomly selected healthy eye of 100 subjects was scanned twice with the Pentacam HR by one observer for each of the three measurement modes: 25-picture (1 second) scan, 50-picture (2 second) scan, and cornea fine scan (50 pictures in 1 second). The repeatability of each scan mode was assessed. One additional 25-picture scan was acquired by a second observer to test reproducibility. Results.: Overall, the Pentacam HR had good precision, with the cornea fine scan returning the most precise results. The 25- and 50-picture scans showed similar precision. The repeatability limits, expressed as the within-subject SD × 1.96√2 of the anterior keratometry (K)1 and K2 readings with the standard 25-picture scan, were 0.25 and 0.36 D, respectively. Pachymetry maps, corneal maps, anterior chamber depth maps, corneal volume, topometric Q values and indices were also found to be precise. Poor precision was found for estimates of axis (astigmatic and progression index), pupil center pachymetry, single points on corneal maps, refractive power maps, and equivalent K readings. Conclusions.: Measurements taken with the Pentacam HR are repeatable and reproducible, especially those obtained with the cornea fine scan. Although the Pentacam HR is clearly a very useful clinical and research tool, the measurement of corneal axes, pupil center pachymetry, front meridional and axial maps, refractive power maps, and equivalent K readings should be interpreted with caution

Subscale Assessment of the NEI-RQL-42 Questionnaire with Rasch Analysis

This article is made available with the permission of the publisher, Association for Research in Vision and OphthalmologyPurpose.: To explore the psychometric properties of the 13 subscales of the NEI-RQL-42 questionnaire using Rasch analysis. Methods.: The NEI-RQL-42 is a refractive error-related quality of life (QoL) questionnaire with a complex design; its 13 subscales contain 42 questions, which include 16 different question/response category formats. It was completed by 100 laser refractive surgery subjects (spectacle and contact lens wearers) pre- and postoperatively. Rasch analysis was used to assess the use of response categories, success in measuring a single trait per subscale (unidimensionality), ability to discriminate persons (precision), and targeting of the questions to person QoL. Results.: Response categories were misused in four subscales (clarity of vision, diurnal fluctuation, symptoms, and appearance), which required repair before further analyses. Six subscales contained items that did not contribute to a single trait measurement (multidimensional). All subscales were found to be inadequate at distinguishing between persons (person separation >2.0), and targeting of the questions to QoL was poor for six subscales. Conclusions.: The NEI-RQL-42 questionnaire is deficient for all psychometric properties tested. Clinicians or researchers wishing to measure QoL related to refractive error correction should consider other questionnaires that have been rigorously developed and meet standard psychometric properties

Demographics, referral patterns and management of patients accessing the Welsh Eye Care Service

BACKGROUND: The Primary Eyecare Acute Referral Service (PEARS) and the Wales Eye Health Examination (WEHE) operate as enhanced optometry services for patients residing in Wales, enabling the examination of a patient presenting with an acute eye problem (PEARS) or the examination of patients at higher risk of eye disease (WEHE). The purpose of the study is to assess the demographics of patients accessing these services, referral patterns and clinical management in one Health Board in Wales (Aneurin Bevan University Health Board). METHODS: Information from 2302 patients accessing the services was prospectively collected. The following information was obtained: type of examination (PEARS or WEHE), patient age, gender, self-referral or general practitioner (GP) referral and clinical management (no further action, monitor by optometrist or ophthalmic medical practitioner [OMP], refer to the Hospital Eye Service [HES], or refer to GP). RESULTS: There were 1791 (77.8 %) PEARS examinations and 511 (22.2 %) WEHE. There were 1379 (59.9 %) females with a mean age of 58.61 (±19.75) and 923 (40.1 %) males with a mean age of 56.11 (±20.42). The majority of patients were self-referrals compared to GP-referrals (1793 [77.9 %] versus 509 [22.1 %] respectively). Sub-analysis indicated similar numbers of self-referrals compared to GP-referrals for the WEHE only (297 [58.1 %] versus 214 [41.9 %] respectively) but greater numbers of self-referrals for the PEARS examinations only (1496 [83.5 %] versus 295 [16.5 %] respectively). For management, 75 % of patients were monitored by their optometrist or OMP, 17 % required referral to the HES and 8 % required referral to their GP. CONCLUSIONS: Higher numbers of females accessed both PEARS and WEHE services and the majority of patients self-referred. These findings have important implications for public health campaigns both for targeting specific groups (e.g. male patients) and increasing awareness among GPs

Subjective Quality of Vision Before and After Cataract Surgery

This article is made available in accordance with the publisher's public repositories policy.Objective To investigate the effect of cataract surgery on subjective quality of vision. Methods The Quality of Vision (QoV) questionnaire (Italian translation) was completed before and 3 months after cataract surgery in 4 groups of patients recruited from September through December 2010: first eye with ocular comorbidity, first eye without ocular comorbidity, second eye with ocular comorbidity, and second eye without ocular comorbidity. The questionnaire measures 3 aspects of quality of vision: frequency, severity, and bothersome nature of symptoms. The Lens Opacities Classification System (LOCS) III was used for cataract grading. Friedman and Kruskal-Wallis H tests were performed to compare QoV scores within and between groups. Spearman rank correlations (rs) were calculated to investigate the correlation between LOCS III and QoV symptoms. Results Two hundred twelve patients (mean [SD] age, 74.2 [8.7] years) were recruited, and 212 eyes were included in the study. Improvements in QoV scores were found in all 4 groups (P .05) differences among the 4 groups in the improvement in QoV scores or in the preoperative or postoperative scores. Blurred vision was correlated with posterior subcapsular cataract (rs = 0.420, P = .04). Conclusions Cataract in one or both eyes causes a similar loss in subjective quality of vision, which is also irrespective of the presence of ocular comorbidity. Posterior subcapsular cataract causes the specific symptom “blurred vision.” Cataract surgery resulted in a large and comparable improvement in subjective quality of vision, regardless of ocular comorbidity and first or second eye surgery

Reengineering the Glaucoma Quality of Life-15 Questionnaire with Rasch Analysis

This article is made available with the permission of the publisher, Association for Research in Vision and OphthalmologyPurpose.: To investigate, using Rasch analysis, whether the 15-item Glaucoma Quality of Life-15 (GQL-15) forms a valid scale and to optimize its psychometric properties. Methods.: One hundred eighteen glaucoma patients (mean age, 65.7 years) completed the German-version of the GQL-15. Rasch analysis was performed to assess category function (how respondents differentiated between the response options), measurement precision (discriminative ability), unidimensionality (whether items measure a single construct), targeting (whether items are of appropriate difficulty for the sample), and differential item functioning (whether comparable subgroups respond differently to an individual item). Where any of these attributes were outside acceptable ranges, steps were taken to improve the instrument. Results.: The five-response categories of the GQL-15 were well differentiated by respondents, as demonstrated by ordered and well-spaced category thresholds. The GQL-15 had an excellent measurement precision but demonstrated poor targeting of item difficulty to person ability and multidimensionality, indicating that it was measuring more than one construct. Removal of six misfitting items created a nine-item unidimensional instrument with good measurement precision and no differential item functioning but poor targeting. A new name, the Glaucoma Activity Limitation (GAL-9) questionnaire, is proposed for the short version, which better reflects the construct under measurement. Conclusions.: The GAL-9 has superior psychometric properties over the GQL-15. Its only limitation is poor targeting of item difficulty to person ability, which is an inevitable attribute of a vision-related activity limitation instrument for glaucoma patients, most of whom have only peripheral visual field defects and little difficulty with daily activities

The development of an instrument to measure quality of vision: the quality of vision (QoV)

PURPOSE. To develop an instrument to measure subjective quality of vision: the Quality of Vision (QoV) questionnaire. METHODS. A 30-item instrument was designed with 10 symptoms rated in each of three scales (frequency, severity, and bothersome). The QoV was completed by 900 subjects in groups of spectacle wearers, contact lens wearers, and those having had laser refractive surgery, intraocular refractive surgery, or eye disease and investigated with Rasch analysis and traditional statistics. Validity and reliability were assessed by Rasch fit statistics, principal components analysis (PCA), person separation, differential item functioning (DIF), item targeting, construct validity (correlation with visual acuity, contrast sensitivity, total root mean square [RMS] higher order aberrations [HOA]), and test-retest reliability (two-way random intraclass correlation coefficients [ICC] and 95% repeatability coefficients [R c ]). RESULTS. Rasch analysis demonstrated good precision, reliability, and internal consistency for all three scales (mean square infit and outfit within 0.81-1.27; PCA Ͼ60% variance explained by the principal component; person separation 2.08, 2.10, and 2.01 respectively; and minimal DIF). Construct validity was indicated by strong correlations with visual acuity, contrast sensitivity and RMS HOA. Test-retest reliability was evidenced by a minimum ICC of 0.867 and a minimum 95% R c of 1.55 units. CONCLUSIONS. The QoV Questionnaire consists of a Raschtested, linear-scaled, 30-item instrument on three scales providing a QoV score in terms of symptom frequency, severity, and bothersome. It is suitable for measuring QoV in patients with all types of refractive correction, eye surgery, and eye disease that cause QoV problems. (Invest Ophthalmol Vis Sci. 2010;51:5537-5545) DOI:10.1167/iovs.10-5341 Q uality of vision (QoV) is a subjective entity based on an individual's unique perception of his or her vision. This perception is multifactorial, consisting not only of visual factors but also of psychological factors. Although optics and vision can be easily measured, none of these measurements explain how the patient subjectively perceives his or her vision; they provide only an indication. 1 Two patients may have identical visual function in terms of objective and subjective testing but very different perception of their QoV. Eye disease, refractive surgery, spectacles, and contact lenses may change QoV. 2-9 Therefore, the patient's perception of QoV may be an important outcome measure, but measuring perception requires a thoroughly developed and validated questionnaire. Many vision-related questionnaires have been developed, but none that specifically measures only QoV. Some instruments include QoV questions, but the questions are mixed in with the measurement of other latent traits such as visual disability. 10 -14 This combining of traits is a problem because all items that are combined to produce a score should measure a single trait; otherwise, the meaning of the measurement is unclear. 15 Second, averaging scores across all items erroneously assumes that the result provides an interval scale. It cannot be assumed that the difficulty of all questions is the same and the difficulty step between each category is constant; hence, the scaling may not be additive or linearly related to the trait under investigation. 16 Such instruments are inadequate for dealing with unanswered items and are not suitable to arithmetic functions. Item response models such as Rasch analysis have demonstrated the limitations in traditional summary (Likert) scoring 21 Rasch analysis consists of a family of psychometric models that provides a valid measurement of the latent trait, in this case, QoV, with recognized superiority over summary scoring methods. METHODS Prestudy and Questionnaire Design Items were identified via an extensive literature review and in focus groups with nonexperts and experts in the fields of refractive correction, questionnaire design, and subject interviews, to ensure content validity. The items were constructed and written at a comprehension level suitable for a 12-year-old

Meta-analysis of optical lowcoherence reflectometry versus partial coherence interferometry biometry

This work is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/A meta-analysis to compare ocular biometry measured by optical low-coherence reflectometry (Lenstar LS900; Haag Streit) and partial coherence interferometry (the IOLMaster optical biometer; Carl Zeiss Meditec). A systematic literature search was conducted for articles published up to August 6th 2015 in the Cochrane Library, PubMed, Medline, Embase, China Knowledge Resource Integrated Database and Wanfang Data. A total of 18 studies involving 1921 eyes were included. There were no statistically significant differences in axial length (mean difference [MD] 0 mm; 95% confidence interval (CI) −0.08 to 0.08 mm; p = 0.92), anterior chamber depth (MD 0.02 mm; 95% CI −0.07 to 0.10 mm; p = 0.67), flat keratometry (MD −0.05 D; 95% CI −0.16 to 0.06 D; p = 0.39), steep keratometry (MD −0.09 D; 95% CI −0.20 to 0.03 D; p = 0.13), and mean keratometry (MD −0.15 D; 95% CI −0.30 to 0.00 D; p = 0.05). The white to white distance showed a statistically significant difference (MD −0.14 mm; 95% CI −0.25 to −0.02 mm; p = 0.02). In conclusion, there was no difference in the comparison of AL, ACD and keratometry readings between the Lenstar and IOLMaster. However the WTW distance indicated a statistically significant difference between the two devices. Apart from the WTW distance, measurements for AL, ACD and keratometry readings may be used interchangeability with both devices

Identifying Content for the Glaucoma-specific Item Bank to Measure Quality-of-life Parameters

"This is a non-final version of an article published in final form in Khadka J, McAlinden C, Craig JE, Fenwick EK, Lamoureux EL, Pesudovs K. Identifying content for the glaucoma-specific item bank to measure quality-of-life parameters. Journal of Glaucoma . 2015 Jan;24(1):12-9. doi: 10.1097/IJG.0b013e318287ac11.". Author manuscript version made available in accordance with publisher copyright policy.PURPOSE: Patient-reported outcomes (PROs) have become essential clinical trial end points. However, a comprehensive, multidimensional, patient-relevant, and precise glaucoma-specific PRO instrument is not available. Therefore, the purpose of this study was to identify content for a new, glaucoma-specific, quality-of-life (QOL) item bank. METHODS: Content identification was undertaken in 5 phases: (1) identification of extant items in glaucoma-specific instruments and the qualitative literature; (2) focus groups and interviews with glaucoma patients; (3) item classification and selection; (4) expert review and revision of items; and (5) cognitive interviews with patients. RESULTS: A total of 737 unique items (extant items from PRO instruments, 247; qualitative articles, 14 items; focus groups and semistructured interviews, 476 items) were identified. These items were classified into 10 QOL domains. Four criteria (item redundancy, item inconsistent with domain definition, item content too narrow to have wider applicability, and item clarity) were used to remove and refine the items. After the cognitive interviews, the final minimally representative item set had a total of 342 unique items belonging to 10 domains: activity limitation (88), mobility (20), visual symptoms (19), ocular surface symptoms (22), general symptoms (15), convenience (39), health concerns (45), emotional well-being (49), social issues (23), and economic issues (22). CONCLUSIONS: The systematic content identification process identified 10 QOL domains, which were important to patients with glaucoma. The majority of the items were identified from the patient-specific focus groups and semistructured interviews suggesting that the existing PRO instruments do not adequately address QOL issues relevant to individuals with glaucoma

Changes in visual function and optical and tear film quality in computer users

Purpose: To assess changes in visual function and optical and tear film quality in computer users.Methods: Forty computer workers and 40 controls were evaluated at the beginning and end of a working day. Symptoms were assessed using the Quality of Vision questionnaire (QoV), 5-item Dry Eye Questionnaire (DEQ--5) and Symptom Assessment in Dry Eye version II (SANDE II). Tear film quality was evaluated using the Medmont E300 dynamic corneal topography tool to measure the tear film surface quality (TFSQ), TFSQ area and auto tear break- -up time (TBUT). Optical quality was assessed by measuring high, low and total ocular aberrations with a Hartmann-Shack wavefront sensor. Visual performance was assessed by measuring photopic and mesopic visual acuity, photopic and mesopic contrast sensitivity and light disturbance.Results: Poorer DEQ-5, QoV and SANDE II scores were obtained in computer workers at the end of the working day compared with controls ( p = 0.19) or ocular aberrations were observed (p >= 0.09). Additionally, both light disturbance ( p = 0.07). In contrast, control subjects exhibited no decrease in any variable during the day.Conclusions: While visual acuity remained unchanged, several aspects of visual function and quality of vision decreased over a day of computer use. These changes were accompanied by greater dry eye symptoms and tear film changes, which are likely to have played a fundamental role. The present study provides insight into new metrics to assess digital eye strain.Conselleria d'Educacio, Investigacio, Cultura i Esport de la Generalitat Valenciana, Grant/Award Number: GV/2018/059; Spanish Ministry of Universities, Grant/Award Number: FPU17/0366