Biomedical subjects

Anca-Doina Dimofte

Publications and source records attributed to Anca-Doina Dimofte.

3 recordsLinked to original sources

PubMed2004

[Changes in contrast sensitivity in glaucoma patients].

OBJECTIVE: To evaluate changes of temporal contrast sensitivity (TCS) in patients with glaucoma. MATERIAL AND METHOD: We measured TCS (for 10, 20 and 30 Hz frequencies) in 57 eyes with glaucoma using a prototype that produces a red colour flicker stimulus (lambda = 626 nm) projected in the central 320 of the visual field. In all patients measurements were undertaken for the visual acuity and intraocular pressure. Also the optic disc was evaluated (including C/D ratio), as well as the visual field using the 24/2 program of the Humphrey automated perimeter. RESULTS: For all tested frequencies we computed sensitivity and specificity of the test S < 0 as diagnostic tool for glaucoma. The sets of determination with 30 Hz flicker stimulus have a validity score of 83.8%. We also evaluated the correlation curves between the S score, C/D ratio and mean deviation from automated perimetry. CONCLUSIONS: Patients with glaucoma present a significant drop of the S score for all three tested frequencies. The S score positively correlates with mean deviation (MD) and negatively with C/D ratio reflecting thus diffuse alterations of the magnocellular system. The decrease of the S score in the 30 Hz set of data is major and S < 0 as a diagnostic test has very good sensitivity and specificity. S score might be used in screening for glaucoma as well as monitoring progression of the disease (rapid test, low cost, good validity).

Analysis of Variance↗

PubMed2003

[Measurement of temporal contrast sensitivity].

OBJECTIVE: The main objective is to present a new prototype designed to test temporal contrast sensitivity, using a flicker stimulus. MATERIAL AND METHOD: We used a radiant surface manufactured with light emitting diode having a dominant wave-length of 626 nm, producing a light spot projected in the central visual field (320). The system uses a flicker stimulus with parameters (light intensity and frequency) that can be varied using a computer. The test group (24 healthy subjects) gave us the possibility to evaluate the test response, to optimise the testing protocol and draw the specific de Lange curve. RESULTS: The test has a very good reproducibility with less then 1% variations between measurements. Distribution of temporal contrast sensitivity follows the de Lange classic curve, the frequencies tested in this experiment being situated on the platou of the curve. We preferred to express the results as minimal light intensity. Within 10 Hz to 30 Hz the results demonstrate little dispersion, with a standard deviation of 0.8% and 2.1% for maximal light intensity of 100% and 50% respectively. CONCLUSIONS: We consider that the prototype can be used for testings of the temporal contrast sensitivity for the central visual field (central 320). The device is simple to use and can well accommodate for outpatient evaluations. We hope that our prototype will be used to monitor minimal changes in the response of the visual system to flicker stimuli.

Adult↗

PubMed2003

[Temporal contrast sensitivity in general population].

OBJECTIVE: To define the normal range of values for temporal contrast sensitivity (TCS) in the general population. MATERIAL AND METHOD: The study group consisted of 140 healthy subjects (280 eyes). Measurements were performed using a prototype designed to produce a red color flicker test (660 nm) with variable frequency and modulation, projected în the central visual field. We conducted test with 10, 20 and 30 Hz with highest illumination level. Subjects have been grouped according to age decades as well as sex. Each group was separately evaluated for distribution type, mean and confidence interval. Statistical differences were assessed using ANOVA with one variable. RESULTS: No significant differences could be found between male and female subjects and the response pattern is very similar în all age groups. Temporal contrast sensitivity presents a normal distribution, with a limited dispersion of data around mean value for the respective decade. TCS slightly decreases with age but correlation parameters do not gain statistical significance. Normal range was defined for age decades using the S score, which quantifies the distance from the mean and as such compensates for the differences generated by the non-linear relationship between age and TCS. The test S < 0 defines pathological circumstances with a specificity of 96.5% at 10 Hz, 99.3% at 20 de Hz and 95.4% at 30 de Hz respectively. CONCLUSIONS: We managed to establish normal TCS range of values for the general population using a test with a very good specificity. These normal values, obtained within a statistically significant group, represent the first step în using TCS în ophthalmologic research. Abnormal TCS changes can now be compared with normal values for each age group.

Adolescent↗