optometer


Also found in: Dictionary, Wikipedia.
Related to optometer: pupilloscope

optometer

 [op-tom´ĕ-ter]
a device for measuring ocular refraction.

op·tom·e·ter

(op-tom'ĕ-tĕr),
An instrument for determining the refraction of the eye.
[opto- + G. metron, measure]

optometer

/op·tom·e·ter/ (op-tom´ĕ-ter) a device for measuring the power and range of vision.

op·tom·e·ter

(op-tom'ĕ-tĕr)
An instrument for determining the refraction of the eye.
[opto- + G. metron, measure]

optometer

An automatic machine for determining the REFRACTION of the eye. Also known as a refractometer.

optometer 

Instrument for measuring the refractive state of the eye. There are two main types of optometers: subjective and objective. Subjective optometers rely upon the subject's judgment of sharpness or blurredness of a test object while objective ones contain an optical system which determines the vergence of light reflected from the subject's retina. Electronic optometers in which all data appear digitally within a brief period of time after the operator has activated a signal can be of either type. Objective types (also called autorefractors or autorefractometers) have become very popular and several of these autorefractors are now providing both objective and subjective systems within the same instrument. Syn. refractometer. See objective accommodation; Humphrey Vision Analyser; autorefraction; infrared optometer; photorefraction; refractive error.
Badal's optometer A simple, subjective optometer consisting of a single positive lens and a movable target. The vergence of light from the target, after refraction through the lens, depends upon the position of the target. The patient is instructed to move the target towards the lens from a position where it appears blurred until it becomes clear. That point (converted in dioptric value) represents the refraction of the patient's eye. This is a crude and inaccurate instrument, in which the measurement is marred by accommodation, variation in retinal image size with target distance, large depth of focus, non-linearity of the scale, etc. Badal's improvement was to place the lens so that its focal point coincides with either the nodal point of the eye or the anterior focal point of the eye or the entrance pupil of the eye, thus overcoming the problems of the non-linear scale and the changing retinal image size (Fig. O3).
optometer of Fincham, coincidence An objective optometer which forms the image of an illuminated fine line target on the retina by passing through a small, peripheral portion of the pupil. The examiner views through a telescope with an optical doubling system, which splits the visual field into two. If the incident beam of light is not in focus on the retina, the reflected beam will not be along the optical axis and the two half-lines will be seen out of alignment. Adjusting the dioptric value of the target in order to obtain alignment gives a measure of the ametropia.
infrared optometer An optometer that uses infrared light rather than visible light. This is done so that the target used in the optometer is invisible to the patient. Otherwise when it is altered it tends to become a stimulus to accommodation. However, the instrument must be corrected for the chromatic aberration of the eye. Most modern optometers use infrared light. They are based on one of three principles: (1) retinoscopy, (2) Scheiner's experiment, (3) ophthalmoscopy (indirect).
objective optometer; subjective optometer See optometer.
Young's optometer A simple optometer consisting of a single positive lens and using the Scheiner's disc principle. The target is either a single point of light or a thread, which is moved back and forth until it is seen singly by the observer. When the target is out of focus, it is seen double and slightly blurred. See Scheiner's experiment.
Fig. O3 Optical principle of the Badal optometer ( F , F ′, first and second principal focus of the lens; F e , anterior focal point of the eye; T, target)enlarge picture
Fig. O3 Optical principle of the Badal optometer (F, F′, first and second principal focus of the lens; Fe, anterior focal point of the eye; T, target)

optometer

a device for measuring the power and range of vision.
References in periodicals archive ?
In experiments with absolute intensity measurements, it was necessary to detach the recording electrodes and move the preparation so the optometer detector could be placed in the same position as the preparation.
In experiments in which the optometer provided a recorded trace simultaneously with electrical recordings, the optometer detector was placed as close to the preparation, and to the primary light path, as possible with the electrodes and their micromanipulators in place.
b) Irradiance was measured using a Daavlin X96, P9710 optometer (accuracy, [+ or -] 5%).
Measurements of cylindrical irradiance were made using a GigaHertz-Optik model P9710 optometer and a model ROD-360-UV 18-2 cylindrical UV sensor (Puchheim, Germany).
Thus, all measurements were taken using the GigaHertz-Optik model P9710 optometer and model ROD-360-UV18-2 cylindrical UV sensor (Puchheim, Germany).
For example, Rosenfield (1989) reported that laser optometer dark focus values averaged [approximately equal to] 2 D, but dark focus values of the same individuals when measured with an infrared optometer had a mean of 1.
The laser optometer task requires active attention because observers must watch for intermittent test patterns, which appear at unpredictable intervals; when the stimulus appears, the observers must report apparent motion within the pattern, which is often a somewhat difficult task.
Unfortunately, the dark focus position for 4 of the 10 participants was outside of the measurable range of the laser optometer, and thus no analysis of the dark focus data is included in this paper.
1] with a UDT Optometer (Model S370) and a radiometric probe placed 3 mm from the tip of the light guide.
Accommodation and convergence were measured with a dynamic infrared optometer (Cornsweet and Crane, 1970) and a dual-Purkinje image infrared eyetracker (Crane and Steele, 1985), respectively.
Irradiance was controlled with a neutral-density wheel driven by a stepper motor under computer control, and calibrated with a UDT optometer (United Detector Technology Model S370) and radiometric probe with point calibrations provided by UDT.
Use of hand-held air-puff tonometers to measure intraocular pressure (IOP); Use of hand-held optometers (Nikon, Retinomax) for objective refraction.