P. Capris

Learning effect, short-term fluctuation, and long-term fluctuation in frequency doubling technique

PURPOSEnTo evaluate short-term and long-term fluctuations and learning effects in healthy subjects tested with the frequency doubling technique, which is based on a low spatial frequency and a high temporal frequency stimulus.nnnMETHODSnTwenty-three healthy adult subjects were consecutively recruited from volunteers, and 20 subjects finished the study. All the visual fields were assessed by the frequency doubling technique, program C-20, full threshold. The frequency doubling technique presents stimuli on a black-and-white video monitor with specialized control circuitry interfaced to a microprocessor. During program C-20, full threshold, 17 points are tested, one round point centrally and 16 square ones in the periphery up to 20 degrees of eccentricity. Each stimulus consists of a 0.25-cycle/degree sinusoidal grating undergoing a 25-Hz counterphase flicker. One eye of each patient was chosen at random. Each subject was tested once in the first session, three times in the second session, and once in the third and fourth sessions. Both short-term and long-term fluctuation were studied either as the average fluctuation value of all the points tested or as a point-to-point fluctuation. To study the learning effect, the results of the first session were compared with those of the second, the third, and the fourth sessions.nnnRESULTSnThe average mean sensitivity of the three examinations of the second session was 30.4 +/- 1.24 dB, and the average short-term fluctuation of all the subjects was 2.16 +/- 0.5 dB. The short-term fluctuation of each point tested ranged from 1.4 to 3.4 dB. The average mean sensitivity for all the sessions was 32.4 +/- 1.14 dB, with an average long-term fluctuation of 3.23 +/- 0.5 dB, and the long-term fluctuation of each tested point ranged from 2.5 to 4.4 dB. A mild learning effect was found between the first section and the others.nnnCONCLUSIONnShort-term and long-term fluctuations were similar to those known to occur with the conventional threshold perimetry when they were compared with the literature data. A learning effect was also observed and should be taken into account for the clinical use of this test.

Correlation between high-pass resolution perimetry and standard threshold perimetry in subjects with glaucoma and ocular hypertension.

Purpose: To evaluate the correlation between High–Pass Resolution Perimetry (HRP) and standard threshold perimetry in patients with glaucoma or ocular hypertension. Methods: 31 glaucomatous patients and 37 ocular hypertension subjects with previous perimetric examination experience were consecutively recruited and only one eye for each patient was selected at random. Glaucomatous patients were classified as having primary open angle glaucoma when they had an abnormal visual field and/or an abnormal optic nerve head (ONH)/retinal nerve fiber layer (RNFL) typical of glaucoma, open angle at gonioscopy and no clinically apparent secondary cause for their glaucoma. Ocular hypertension subjects were defined as having intraocular pressure>21 mm Hg on no treatment, normal visual field, normal ONH and RNFL, elevated intraocular pressure without any treatment. All the subjects were examined with Humphrey Field Analyzer (HFA) 640, `program central 30-2 (Humphrey Systems, San Leandro, CA, USA) and with High–Pass Resolution Perimeter (HRP), Ophthimus version 2.4, `ring program (Nikon-HighTech Vision, Goteborg, Sweden). Visual field indices were obtained with both systems: for HFA mean deviation (MD), corrected pattern standard deviation (CPSD) and short term fluctuation (SF), while for HRP global deviation (GD), local deviation (LD), form index (FI) and neural capacity (NC). The data were analyzed by descriptive analysis, Students t test with Bonferronis correction or Mann-Whitney non-parametric test and Pearson or Spearmans correlation coefficient.Results: A significant correlation was found between MD and GD (r = -0.81), CPSD and LD (r = 0.87), PSD and LD (r = 0.72). NC was significantly correlated with MD (r = 0.76), GD (r = -0.94). FI was significantly correlated with PSD (r = -0.58), CPSD (r = -0.72), LD (r = -0.56).When the same data were analyzed for the glaucomatous group only, similar results were found; in the ocular hypertensive group no significant correlation was found except between NC and MD (r = 0.52).Conclusion: HRP indices vary comparably with HFA indices. Parameters as NC and FI were significantly correlated with standard visual field indices of both HFA and HRP. Although the clinical applications for FI are not clear yet, NC could detect both early glaucomatous damage and age related changes.

Optimized macular recovery test for the early diagnosis and risk prediction of retinopathy in diabetics

SummaryThe authors present a clinical study on the macular recovery test, in a new optimized version, in normal subjects and in diabetic patients. The discriminating thresholds between normals and retinopathic diabetics and between non-retinopathic and retinopathic diabetics were statistically analyzed.