ABSTRACT
The electrostriction contribution to the nonlinear refractive index in optical fiber was theoretically calculated and measured. Nonlinearity was induced directly by insertion of the optical fiber into an intense external electric field. With this technique both the Kerr and the electrostrictive contributions to the intensity dependence of the nonlinear refractive index in a step-index fiber were measured. Good agreement between calculated and measured values was observed. These results should confirm and explain the differences observed in measurement of n(2) at different bit rates.
ABSTRACT
A hand-held noncontact tonometer (Pulsair, Keeler Ltd., UK) was tested in 42 children, from 5 months to 12 years of age. At least 1 intraocular pressure (IOP) reading was obtained in all of the 84 eyes studied, whereas with a Goldman applanation tonometer measurements could be obtained in only 26 eyes (14 subjects). Time required for examination with the Pulsair was quite variable and related to age (p less than 0.0001). Compliance in children was reported as "good" in the majority of cases; it was also age-related (p less than 0.005). Although its reliability could not be definitely evaluated, the results of this study indicate that this instrument may be a valuable choice for screening and follow-up purposes in childhood.
Subject(s)
Intraocular Pressure , Tonometry, Ocular/instrumentation , Child , Child, Preschool , Female , Glaucoma/diagnosis , Humans , Infant , Male , Patient Compliance , Vision Tests/instrumentationABSTRACT
To verify whether central threshold testing with a common automated perimeter could detect glaucomatous damage, we selected 40 eyes with primary open-angle glaucoma and 43 eyes of age-matched normal subjects. The glaucomatous eyes were free from visual field defects within the central 5 degrees. They underwent the Macula Threshold Test of the Humphrey perimeter, using white and blue targets. Differential sensitivities to both white and blue were significantly depressed in the glaucoma group (p less than 0.001). Blue thresholds of glaucomatous subjects and normal subjects were distributed in two quite separate domains, with a mean difference of 4.51 dB. Sensitivities to blue stimuli were related to age in the normal group (r = 0.62; p less than 0.001), while in the glaucoma group they were related to horizontal cup/disc ratios (r = 0.63; p less than 0.001). These results suggest that threshold testing with an automated perimeter and its built-in colour filters can be of help in detecting early central functional disturbances from glaucoma.
Subject(s)
Contrast Sensitivity/physiology , Glaucoma, Open-Angle/physiopathology , Color Perception Tests , Evaluation Studies as Topic , Fovea Centralis/physiopathology , Humans , Middle AgedABSTRACT
The aim of our study was to verify whether threshold testing of the central area with a common automated perimeter could detect early glaucomatous damage. We selected 9 eyes of 9 patients with suspected primary open angle glaucoma and normal visual fields and 18 eyes of 18 age-matched normal subjects. They underwent the Macula Threshold Test of the Humphrey Field Analyzer using white and blue targets. We found no significant difference in retinal sensitivity to white targets between the two groups. Sensitivity to blue targets was significantly lower among glaucoma suspects (18.43 +/- 1.14 dB) than in the control group (22.37 +/- 0.94 dB) p less than 0.001). Blue thresholds related significantly to age only in normals (p = 0.028) while in glaucoma suspects they were strongly related to vertical cup/disc ratios (p less than 0.001). These results suggest that it is possible to detect early central visual disturbances from glaucoma using an automated perimeter and its built-in color filters.
Subject(s)
Fovea Centralis/physiopathology , Glaucoma, Open-Angle/diagnosis , Macula Lutea/physiopathology , Aged , Color Perception , Female , Glaucoma, Open-Angle/physiopathology , Humans , Male , Middle Aged , Photic Stimulation , Sensory Thresholds , Visual Acuity , Visual Field Tests , Visual FieldsABSTRACT
The purpose of this study has been to verify whether threshold testing of the central area with a common automated perimeter could detect glaucomatous damage. We selected 31 eyes of 31 patients with primary open angle glaucoma free from defects within the central 5 degrees of the field and 32 eyes of 32 age-matched normal subjects. They underwent the Macula Threshold Test of the Humphrey Field Analyzer using white and blue targets. Statistical analysis of the results obtained showed that threshold sensitivities to both white and blue targets were significantly depressed in glaucomatous eyes (t = 2.44, p = 0.018 and t = 12.59, p less than 0.001 respectively), but only blue thresholds distributed really differently in glaucomatous and normals. Sensitivities to blue stimuli related to age only in normals (r = 0.58; p = 0.0005), while in glaucomatous they were related to cup/disc ratios (r = 0.70, p less than 0.0001 for horizontal C/D; r = 0.52, p = 0.0027 for vertical C/D). These results suggest that it is possible to detect early central functional disturbances from glaucoma using an automated perimeter and its built-in color filters.
