Abstract
Purpose: :
To evaluate the effect of refractive correction on the reliability and accuracy of visual fields made by frequency doubling technology (FDT) Matrix.
Methods: :
48 eyes of healthy people were submitted to FDT Matrix 30/2 threshold program. All the subjects had already experienced in perimetry. The mean age was 36.5 ± 9.2 yrs and the refractive defect was included between -3.50 to + 2.00 diopters (mean value -1.31 ± 2,41 D) with a corrected visual acuity of 20/20. All the subjects had normal eye examination, intraocular pressure (IOP) < 20 mmHg and they were in good general health. They had negative familiar history for glaucoma and/or neurological diseases. All the subjects were submitted to 30/2 FDT Matrix visual field two times with an interval of one week; first session without refractive correction, second session using the best refractive correction. Mean Defect (MD), Pattern Standard Deviation (PSD), False Positive (FP) False Negative (FN) answers, Fixation loss (FL) and time of examination of the two different sessions of visual field exams were considered and submitted at statistical analysis (t Test).
Results: :
MD was statistically significant reduced when the refractive correction is used (- 2,03 dB ± 3,64 vs -1,41 ± 3,51 p < 0,006273) while PSD did not statistically changed ( 3.06 ± 0.89 vs 3.11 ± 0,80 p< 0.53). The reliability parameters and time of examination had no significant variation with or without refractive correction.
Conclusions: :
It is known FDT responses is mediated by magnocellular (M) ganglion cells. These cells are poorly influenced by blur vision when stimulated. However the statistically significant reduction of MD obtained with corrective lens showed that a better general accuracy and sensitivity of FDT responses is obtained with refractive correction. PSD constancy with or without correction confirmed that a localized defect is the first sign of visual field defect and that the absence of difference of PSD between the two sessions is related to the absence of pathological conditions in the eyes studied. It can be concluded that since FDT Matrix is less influenced by other non conventional perimetric techniques by refractive errors the use of corrective lens is any case advisable to improve the accuracy and reliability of the results obtained .
Keywords: visual fields • refraction • optic nerve