Construction and validation of a Tamil logMAR chart

Purpose:  To design, construct and validate a new Tamil logMAR visual acuity chart based on current recommendations.
Methods:  Ten Tamil letters of equal legibility were identified experimentally and were used in the chart. Two charts, one internally illuminated and one externally illuminated, were constructed for testing at 4 m distance. The repeatability of the two charts was tested. For validation, the two charts were compared with a standard English logMAR chart (ETDRS).
Results:  When compared to the ETDRS chart, a difference of 0.06 ± 0.07 and 0.07 ± 0.07 logMAR was found for the internally and externally illuminated charts respectively. Limits of agreement between the internally illuminated Tamil logMAR chart and ETDRS chart were found to be (−0.08, 0.19), and (−0.07, 0.20) for the externally illuminated chart. The test – retest results showed a difference of 0.02 ± 0.04 and 0.02 ± 0.06 logMAR for the internally and externally illuminated charts respectively. Limits of agreement for repeated measurements for the internally illuminated Tamil logMAR chart were found to be (−0.06, 0.10), and (−0.10, 0.14) for the externally illuminated chart.
Conclusions:  The newly constructed Tamil logMAR charts have good repeatability. The difference in visual acuity scores between the newly constructed Tamil logMAR chart and the standard English logMAR chart was within acceptable limits. This new chart can be used for measuring visual acuity in the literate Tamil population.     

角膜生物力学性能测量方法的研究进展

角膜为黏弹性生物组织,其生物力学性能测量方法主要可分为离体测量法和活体测量法。其中离体测量法又分为角膜轴向拉伸法、角膜膨胀法、离体全眼球测量法等;活体测量法以眼反应分析仪测量法为主。几种方法各有优缺点,均不能全面反映角膜的生物力学性能。在基础试验离体测量法中,角膜膨胀法具有较好的可操作性和重复性;活体测量方法中眼反应分析仪测量法如能建立与经典生物力学参数之间的关系,在临床检查和诊断中将具有更大的潜力和推广性。就目前角膜生物力学性能测量方法的研究现状做一综述。     

Repeatability of corneal parameters with Pentacam after laser in situ keratomileusis

AIM: To investigate the coefficient of repeatability (CR) for corneal parameters evaluated with Pentacam after laser in situ keratomileusis (LASIK) in myopic eyes. DESIGN AND SETTING: Prospective, non-interventional, non-comparative study in an institutional setup. MATERIALS AND METHODS: Forty eyes of 40 consecutive subjects who had undergone LASIK for myopia were assessed with the Scheimpflug system (Pentacam 70700: Oculus, Wetzlar Germany). The mean of five consecutive measurements of all the corneal parameters was recorded and CR was calculated as standard deviation of the difference from the mean of these repeat measurements divided by the mean response. The statistical significance of the CR was calculated for these parameters at 5% significance level. RESULTS: The best CR was observed for the periphery of the anterior corneal curvature (0.18%) and the least for the horizontal meridian of the posterior corneal curvature (1.29%). Despite being significantly different ( P < 0.001), both the measurements were highly repeatable in post-LASIK eyes. The central, apical and minimal corneal thickness had a CR of 1%, 0.78% and 0.77% respectively. These were equally repeatable ( P> 0.323). The CR of the mean radius of curvature of the anterior cornea (0.29%) was significantly better ( P < 0.001) than the posterior corneal curvature (0.57%). CONCLUSION: The CR for the post-LASIK cornea with Pentacam was the best for the anterior corneal curvature. Significantly, Pentacam has a high degree of repeatability for the posterior corneal curvature, which has a potential for early detection of keratectasia in these eyes. Post-LASIK pachymetry with Pentacam also showed excellent repeatability.     

Test–retest repeatability of [18F]Flortaucipir PET in Alzheimer’s disease and cognitively normal individuals

The aim of this study was to investigate the test–retest (TRT) repeatability of various parametric quantification methods for [¹⁸F]Flortaucipir positron emission tomography (PET). We included eight subjects with dementia or mild cognitive impairment due to Alzheimer’s disease and six cognitively normal subjects. All underwent two 130-min dynamic [¹⁸F]Flortaucipir PET scans within 3 ± 1 weeks. Data were analyzed using reference region models receptor parametric mapping (RPM), simplified reference tissue method 2 (SRTM2) and reference logan (RLogan), as well as standardized uptake value ratios (SUVr, time intervals 40–60, 80–100 and 110–130 min post-injection) with cerebellar gray matter as reference region. We obtained distribution volume ratio or SUVr, first for all brain regions and then in three tau-specific regions-of-interest (ROIs). TRT repeatability (%) was defined as |retest–test|/(average (test + retest)) × 100. For all methods and across ROIs, TRT repeatability ranged from (median (IQR)) 0.84% (0.68–2.15) to 6.84% (2.99–11.50). TRT repeatability was good for all reference methods used, although semi-quantitative models (i.e. SUVr) performed marginally worse than quantitative models, for instance TRT repeatability of RPM: 1.98% (0.78–3.58) vs. SUVr_80–100: 3.05% (1.28–5.52), p < 0.001. Furthermore, for SUVr_80–100 and SUVr_110–130, with higher average SUVr, more variation was observed. In conclusion, while TRT repeatability was good for all models used, quantitative methods performed slightly better than semi-quantitative methods.     

Repeatability of corneal thickness measurements made by a scanning slit topography system

Two sets of corneal thickness (CT) measurements at five corneal locations were made with Orbscan on 33 normal young adults. No significant intravisit and intervisit differences at any of the corneal locations were found (Repeated measures ANOVA, F < 0.49, p > 0.49). The 95% limits of agreement (95% LA) for between-measurement differences for the central cornea was about +/-19 microm (or 3%), indicating good repeatability; for the inferior, temporal and nasal corneal locations, the 95% LA were close to +/-30 microm (approximately 4-5%); and for the superior corneal location, they were about +/-35 microm (or 5.5%). The estimated number of repeated measurements that should be taken for accurate CT measurements (at any of the five corneal locations and excluding outliers of >3 S.D.) of 2% (standard error) is < or =2, and of 3% is 1. This study shows that only central CT measurements with the Orbscan are repeatable. The role of the Orbscan pachometry is therefore limited and is recommended for central CT measurements only.     

Pain drawings predict outcome of surgical treatment for degenerative disc disease in the cervical spine

Introduction: Pain drawings have been frequently used in the preoperative evaluation of spine patients. For lumbar conditions comprehensive research has established both the reliability and predictive value, but for the cervical spine most of this knowledge is lacking. The aims of this study were to validate pain drawings for the cervical spine, and to investigate the predictive value for treatment outcome of four different evaluation methods.

Methods: We carried out a post hoc analysis of a randomized controlled trial, comparing cervical disc replacement to fusion for radiculopathy related to degenerative disc disease. A pain drawing together with Neck Disability Index (NDI) was completed preoperatively, after 2 and 5 years. The inter- and intraobserver reliability of four evaluation methods was tested using κ statistics, and its predictive value investigated by correlation to change in NDI.

Results: Included were 151 patients, mean age of 47 years, female/male: 78/73. The interobserver reliability was fair for the modified Ransford and Udén methods, good for the Gatchel method, and very good for the modified Ohnmeiss method. Markings in the shoulder and upper arm region on the pain drawing were positive predictors of outcome after 2 years of follow-up, and markings in the upper arm region remained a positive predictor of outcome even after 5 years of follow-up.

Conclusions: Pain drawings were a reliable tool to interpret patients’ pain prior to cervical spine surgery and were also to some extent predictive for treatment outcome.