pinhole test

pinhole test

1 a test performed on a person who has diminished visual acuity to distinguish a refractive error from organic disease. A refractive error may be corrected with glasses, whereas organic disease may signal the development of preventable blindness. Several pinholes, 0.5 to 2 mm in diameter, are punched in a card. The patient selects one and looks through it with one eye at a time, without wearing corrective lenses. If visual acuity is improved, the defect is refractive; if not, it is organic. The pinhole effect results from blocking peripheral light waves, which are most distorted by refractive error.
2 a test to determine the size of the focal spot of an x-ray tube.
3 a test to trace the path of x-ray tube movement.
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A low-voltage pinhole test is performed by moving a moistened, electrified sponge over a non-conductive coating applied to a relatively conductive substrate such as metal or concrete.
Pinhole test, the horizontal flow of water under hydraulic height of 50 mm diameter hole in the soil caused by a millimeter, starts [8].
Pinhole test results, all samples are in dark type are classified divergence.
During this patient's hospitalizations, her acuity assessments were always conducted while she was wearing her glasses, but neither a pinhole test nor formal refraction by an eye care specialist had been conducted.
The pinhole test involves directing a patient to look at a visual acuity chart, one eye at a time, through a pinhole.
Among the matters they consider are testing the amount of material in soil finer than number 200 (75 [micro]m) sieve, identifying and classifying dispersive clay soils by the pinhole test, preparing rock slabs for durability testing, analyzing the size of particles in natural and man-made riprap materials, determining the short-term compression behavior of turf reinforcement mats, measuring nominal thickness of permanent rolled erosion control products, installing articulating concrete block revetment systems, and determining the performance of a temporary ditch check in protecting earthen channels from stormwater-induced erosion.