Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/16—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
  • A61B5/161—Flicker fusion testing

Definitions

• the present invention relates to a papillometer comprising a flashing light source, an optical device for transmitting the light emitted by this source to an eye to be examined, an electronic control device for varying the flashing frequency of this source and means for analyze the flicker of said eye.
• papillometers are already known, which are devices making it possible to measure the response of the eye to the blinking of a light source.
• Flickering can be defined as the perception by the eye of the flashing of a light source.
• the eye By blinking a low frequency light source with 100% modulation, the eye distinctly perceives the light that turns on and off alternately.
• the source flashing frequency increases to a value of the order of 4-0 Hz, the eye no longer clearly perceives the flashing and the physiological impression of the patient is that the light has a stronger intensity than 'it really is.
• the papill ⁇ lotion disappears to make way for the impression that light is emitted continuously.
• CFF Cosmetic Flic ering Frequency
• the frequency f and the modulation m can vary independently.
• the variation range of the modulation is from 0 to 100%, since it is impossible to create negative light.
• This stimulation makes it possible to draw curves giving the melting threshold as a function of the frequency and of the modulation for each eye examined.
• the general appearance of these curves is shown in fig. 2 for which the logarithm of the frequency in Hertz has been plotted on the abscissa, and the logarithm of the inverse of the modulation in% on the ordinate.
• the papillometer can become a non-invasive diagnostic instrument whose interest is general and not limited to ophthalmological use.
• the present invention proposes to overcome the drawbacks men ⁇ mentioned above by providing an efficient and reliable papillometer while remaining compact and light.
• control device is arranged to generate a digital sinusoidal signal in delta modulation.
• the flashing light source is a photo-emitting diode.
• the source of electrical energy, the light-emitting diode, the optical system for focusing the light emitted by the source on the retina of an eye to be examined, and the control device are mounted in the same housing. .
• the electronic control device comprises a memory in which at least one range of frequencies and at least one range of modulations are recorded.
• said memory can comprise several registers each corresponding to a range of frequencies, the stored information defining control signals of the light source.
• fig. 1 represents the curve illustrating the stimulation to which the eye to be examined is subjected
• fig. 2 shows the response curve of the eye subjected to the stimulation according to FIG. 1, i.e. the DE LANGE curve
• fig. 3 represents a sectional view illustrating the papillometer according to the invention
• fig. 4- represents a block diagram of the electronic components of the papillometer according to FIG. 3, and
• fig. 5 illustrates the principle of the delta modulation providing the signal for supplying the light source.
• fig. 1 represents the sinusoidal stimulation curve to which the eye to be examined is subjected. This curve responds to the equation:
• L Lo (l + mcos 2 ⁇ ft) in which the time t is plotted on the abscissa and the value of the stimulation L is plotted on the ordinate, m being the modulation. For a modulation equal to zero L is equal to Lo.
• Fig. 2 represents in logarithmic coordinates the general shape of a DE LANGE curve when the logarithm of the frequency in Hertz is mentioned on the abscissa and when the logarithm of the inverse of the frequency in% is mentioned on the ordinate.
• the papillometer 10 as shown comprises a box 11 of generally rectangular shape, the rear part of which is equipped with an eye 12 intended to be placed in front of the patient's eye.
• This eyecup is mounted on a tubular element 13 secured to the housing 11 which contains a light source 14 constituted for example by a photoluminescent diode preferably emitting yellow light, as well as an optical focusing system 15.
• a light source 14 constituted for example by a photoluminescent diode preferably emitting yellow light, as well as an optical focusing system 15.
• the housing 11 also contains batteries or an accumulator battery 16 as well as an electronic device 17 which will be described in more detail below and which in particular has the function of controlling the supply of the light source.
• this box 11 On its front face, this box 11 includes a switch 18 for engagement and disengagement and two function keys (not shown in this view), as well as a display screen 19 f for example of the liquid crystal type.
• Fig. illustrates the electronic device of the papillometer which comprises function keys 20 and 21 arranged to make it possible to increase or reduce respectively the modulation and the frequency.
• a microprocessor 22 for example of the 6303 type, which controls the light-emitting diode 14 and which has a second output to a device 23 for controlling the display viewed by the screen 19.
• electronic device comprises a memory 24 which is advantageously an electrically programmable read-only memory (EPROM).
• EPROM electrically programmable read-only memory
• the light source used is preferably a photoluminescent diode emitting yellow light.
• This diode is directly controlled by a digital sinusoidal signal in delta modulation. This makes it possible to avoid distortions due to the non-linearity of the photo-emitting diodes and to produce weak modulations.
• the spectrum of the modulated signal contains the fundamental and it is the eye which filters the signal. The modulated signal should therefore not contain harmonics between 0 and 100 Hz.
• Delta modulation is a digital differential modulation characterized by zero order extrapolarization and one-bit quantization so that the only two characteristic parameters are the sampling frequency and the quantization step.
• delta modulation makes it possible in particular to simplify the circuit because it does not require a reactive circuit.
• modulations of the order of one per thousand only the delta modulation gives sufficient stability.
• a direct delta modu ⁇ lation on the eye which acts as an integrator, the non-linearities and the instabilities influence the average intensity, but not the modulation rate.
• the analog signal U (t) which, in the present case, is a sinusoid, is compared to the output signal D (t) of the accumulator 16, at a sampling frequency f ..
• the output of the accumulator must be able to follow the automatic signal.
• the sign slope ⁇ / t. must be equal to the maximum derivative of U (t).
• the signal is sinusoidal therefore:
• the signal is directly demodulated by the eye which acts as a low pass filter.
• the choice of sampling is carried out as follows: the sinusoid tables are calculated on a microcomputer. Through therefore, choose a number of samples per period, not a sampling frequency. The choice of sampling depends on the following criteria:
• the number of samples per period is high when generating a sinusoid at low frequency (between 2 and 10Hz we obtain approximately 12000 samples per period) and lower for high frequencies.
• the sine is not generated by an analog-delta modulation conversion, but is calculated by a microprocessor on the basis of the following general principle:
• a program on a microcomputer creates a digitized sine table in delta modulation. This table is then transferred to an EPROM type memory. This is placed in the papillometer where a microprocessor reads the sinuses in memory and transmits them to the photoluminescent diode. A sine digitized in memory is required for each modulation level.
• the modulation variation is not continuous but the available memory, which is for example 64 K multiplay, allows the storage of more than twenty modulation levels, which is more than sufficient. In practice, only the half sine is memorized and the microprocessor reconstructs the missing half period.
• the memory advantageously comprises several registers in which the frequency ranges are stored.

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• Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Pathology (AREA)
• Heart & Thoracic Surgery (AREA)
• Hospice & Palliative Care (AREA)
• Psychiatry (AREA)
• Psychology (AREA)
• Social Psychology (AREA)
• Physics & Mathematics (AREA)
• Developmental Disabilities (AREA)
• Biophysics (AREA)
• Child & Adolescent Psychology (AREA)
• Biomedical Technology (AREA)
• Educational Technology (AREA)
• Medical Informatics (AREA)
• Molecular Biology (AREA)
• Surgery (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Optical Communication System (AREA)
• Eye Examination Apparatus (AREA)
• Measurement Of The Respiration, Hearing Ability, Form, And Blood Characteristics Of Living Organisms (AREA)

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• 1990
  • 1990-03-27 FR FR9004152A patent/FR2660182A1/fr not_active Withdrawn
• 1991
  • 1991-03-27 US US07/777,540 patent/US5237349A/en not_active Expired - Fee Related
  • 1991-03-27 EP EP91906371A patent/EP0473760A1/de not_active Withdrawn
  • 1991-03-27 CA CA002055592A patent/CA2055592A1/fr not_active Abandoned
  • 1991-03-27 JP JP3505646A patent/JPH04507056A/ja active Pending
  • 1991-03-27 WO PCT/CH1991/000080 patent/WO1991014399A1/fr not_active Ceased

Non-Patent Citations (1)

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