Abstract
Purpose: :
To investigate temporal parameters of contrast sensitivity to chromatic stimuli in patients with different clinical refraction to reveal initial retinal pathologic changes and start early treatment.
Methods: :
We selected 72 subjects of different age for participation in the study: group I - 26 children (6-12 y/o), group II - 26 teenagers (13-19 y/o), group III - 20 adults (20-31 y/o). Clinical refraction varied as follows: 54 eyes had mild myopia (-6.25D), and 26 eyes had mild hyperopia (<+3.00D). For estimation of critical flicker frequency (CFF), light stimulator connected to IBM computer and controlled by specifically designed "Blick" software was used. Testing was monocular and performed on both eyes with full correction of the refractive error. During the test, impulses of green (G), blue (B) and red (R) lights were sequentially presented to a subject. Statistical analysis was performed using parametric (t-test) and nonparametric methods: median, 25/75 percentiles, and Spearman rank correlation coefficient.
Results: :
The greater was the refractive error the more apparent changes in CFF test (in Hz) we observed in all age groups for all chromatic stimuli parameters. Mild myopia patients showed the same results as hyperopia patients and were very close to normal: children - G(43) R(43) B(42.25), teenagers - G(42) R(41) B(40.5), adults - G(43) R(43) B(40.5). In contrast, CFF test was significantly different in high myopia among all groups: children - G(38) R(37) B(36), teenagers - G(37,5) R(37) B(36,75), adults - G(38) R(37) B(37), p less 0.05. 25 and 75 percentiles were analyzed for every CFF color group with every refraction error. The most significant change of CFF test results we observed in adult patients with high myopia: G 38 [35.5-39], a R 37 [35-38.5] and a B 37 [34.5-38], p less 0.05.
Conclusions: :
Our results show that CFF changes in subjects with refractive errors (especially myopia) indicate the presence of initial photoreceptor abnormalities. This helps to diagnose retinal pathology in subjects with refractive errors, especially at early stage progressive myopia at and to improve treatment outcomes.
Keywords: contrast sensitivity • temporal vision • refractive error development