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R Effert

Publications and source records attributed to R Effert.

30 records · Page 2Linked to original sources
PubMed1991

[A new photographic method for measuring squint angles in infants and small children].

A new photographic method for measuring squint angles in children and infants is presented. A photographic picture is taken from the subject, using a camera with the three flashes bulle. One flashbulle is placed vertically over the lens, two other flashbulles are placed symmetrically in an angle of 10 degrees beside the middle flash. Six reflections can be seen on the photographic picture in each pupil. (1. and 4. Purkinje Sanson Images of each light source.) The horizontal distance of two reflections is determined by the distance of the flashguns. If the reflection lines in both eyes are symmetrical, there is no squint. If there is a shift, it can be measured on the slide and by using a simple formula the squint angle can be calculated. The accuracy of the method is between 2 and 3 degrees.

Child, Preschool↗
PubMed1991

[Testing vision in children].

Measurement of visual acuity in children is more difficult than in adults. Children tend to riet when the threshold is reached and become inattentive. However the exact determination of visual acuity in children is important in some situations (Screening, Amblyopia). In this paper we examined whether an automated procedure is more exact than measurement by an examiner. Three series of experiments were done. In n = 173 we measured visual acuity first by an examiner using an optotype projector and second by an automated procedure (computer, keyboard, television screen). Both, the examiner and the computer used the same test-procedure and threshold criterion (DIN-Norm). The correlation coefficient was 0.84. In n = 53 children (age 4 to 7) visual acuity was measured by an examiner without a special strategy. Afterwards visual acuity was measured by the automated procedure. The correlation coefficient was 0.1. In n = 63 children (age 5-7) visual acuity was measured by an examiner using a strategy and a threshold criterion. Afterwards the automated procedure was used. The correlation coefficient was 0.69. The results show, that without a strategy and defined threshold criterion it is not possible to compare the measurements of visual acuity in different times. An automated procedure presented in this paper guaranties constant test conditions in an optimal way.

Adult↗
PubMed1990

[Quantification of capsular sack forces after intraocular lens implantation].

In order to quantify the force acting in the capsular bag following implantation of an intraocular lens (IOL), 58 J- and C-loop lenses obtained from four different manufactures were implanted into the capsular bag in porcine eyes. The cornea and iris were removed before implantation. Photographs of the capsular bag before and after implantation, with a measuring rod for comparison, were taken under a microscope. In this way, the compression of the haptics could be measured (mean 1.7 mm, standard deviation 0.6 mm). Afterwards one haptic of each lens was fixed in a special mount placed on a high precision scale and the opposite haptic was compressed by 2 mm using a special micrometer-screw. After 5 min compression time, differences of 300% between the different manufacturers and lens types were measured. To find out whether the differences measured have an influence on the deformation of the capsular bag, a graph was plotted with force measured and values for elongation of the capsular bag along the axes. In this way a correlation of the elongation and the force could be shown. The results show that besides shaping the haptics of IOLs, the force necessary to compress the haptics also has an influence on the final form of the capsular bag.

Animals↗
PubMed1989

[An alternative measuring procedure to the simultaneous prism cover test].

The simultaneous prism cover test is frequently used for measuring a manifest squint angle. In this paper an alternative method for measuring a manifest squint angle is described. While a subject fixes on a fixation object in near or far position, one eye illuminated from below with a collimated visible light beam. The light source is mounted on a holder which can be rotated around a vertical axis. The examiner observes the light reflexes of the anterior surface of the cornea and the posterior surface of the lens in the patients pupil and turns the holder until the images lie on a vertical line. In this case the direction of the incident light beam, which is determined by the position of the holder, and the direction of the optical axis of the eye coincide. For example, by measuring before and after covering, the difference in the measured light directions is the manifest squint angle, as determined by the simultaneous prism cover test.

Convergence, Ocular↗
PubMed1989

[Automated measurement of distance vision based on the DIN strategy].

A method for automated measurement of far vision is described which meets the test requirements laid down in the new DIN standards. The subject sits 5 m from a high-resolution monitor on which either Landolt rings or Snellen's types are generated by a computer. By moving a joystick the subject indicates to the computer whether he can see the critical detail (e.g., the direction of opening of the Landolt ring). Depending on the subject's input and the course of the test so far, the computer generates the next test symbol until the threshold criterion is reached. The sequence of presentation of the symbols and the threshold criterion are also in accordance with the DIN standard. Initial measurements of far vision using this automated system produced similar results to those obtained by conventional methods.

Distance Perception↗
PubMed1989

[Graphic assessment of retinal findings by computer].

Despite the increasing amount of patient data in the area of words and numbers that is being stored by computer, the graphic storage of ophthalmological findings has found only limited success. However, a sketch is much more instructive than a description in words. This paper shows that by using a suitable computer with a graphic oriented disc-operating system and a purchasable graphic and data base program, it is easily possible to generate sketches of retinal detachment on a computer screen. In the graphic program, all of the necessary symbols are already available when the program is started. The user just makes a copy of the symbols he needs to "draw" the actual fundus findings. We use the system of Meyer-Schwickerath. Afterwards, the drawing on the monitor is transferred into the data base program and stored.

Computer Graphics↗
PubMed1988

[Clinical use of the Canon R10 autorefractometer for determining refraction in children with strabismus].

Using a Canon R 10 Autofractor, refraction was measured in 131 children with squint. Measurements before and after cycloplegia were compared to a reference measurement (taken with the Rodenstock PR 50 hand-held refractometer after cycloplegia). In 80% of the cases the power and axis of the cylinder equalled the reference measurements. Due to accommodation, 40% of the values for spherical equivalents before cycloplegia were false. After cycloplegia 80% of the spherical equivalents were also in agreement with the reference measurement. The short examination time and the interesting fixation target facilitate multiple measurements in children. As a result, refraction can be measured more reliably with the R 10 Autorefractor than with the hand-held refractometer in children from age 2 1/2 or 3. Retinoscopy is only indispensable in cases where it is difficult or impossible to use an autorefractor, i.e., on children aged under 2 1/2 and those with extreme head tilt.

Accommodation, Ocular↗
PubMed1988

[A computer program for registering all daily accumulated data at a school for vision disorders].

Despite increasing medical use of the computer, many clinics have experienced only limited success (or none at all) in computerized registration of patient data. One important reason for this lies in the complicated user interfaces of most programs. The clinician has no time to familiarize himself with the complicated command sequences involved, while necessary acceptance of the new technology by administrative staff is often lacking. This paper shows that computerized registration and interpretation of patient data are well within the bounds of possibility, given the use of newly-developed user-friendly operating systems and suitable personal computers. A concrete example of computerized registration of data in a remedial center is given: a case with squint symptoms for which 176 parameters can be entered.

Documentation↗
PubMed1986

A new method for determining squint angle in primary and all secondary positions using the first and fourth Purkinje images.

A new objective method is presented for measuring the squint angle in all gaze positions. While the subject fixates an object at a distance d, his eyes are illuminated one at a time from above or from the side with a collimated infrared beam. A high-sensitivity infrared camera observes the first and fourth Purkinje images from below. Camera and light source are mounted on the same holder, which can be turned around horizontal and vertical axes. The examiner turns the holder while observing the Purkinje images on a TV monitor until both images lie either on a vertical line (to measure a horizontal deviation) or on a horizontal line (to measure a vertical deviation). In either of these cases the direction of the incident light, which is determined by the position of the holder, and the direction of the optical axis of the eye coincide. Advantages of the method include: the angle between the optical axis and the fixation line can be easily determined; the subject does not have to fixate with both eyes; and the accuracy is +/- 1 degree.

Evaluation Studies as Topic↗
PubMed1986

A new method to perform the cover test.

A new method is presented to perform the cover/uncover test and the alternate cover test. With the subject's head in a chin rest, he fixates an object at either near or far distance, and one eye is illuminated from above with a collimated infrared beam. A high-sensitivity infrared TV camera observes the first and fourth Purkinje images from below. The examiner covers the nonilluminated eye and, viewing a TV monitor, compares the relative positions of the two images before and after covering. By changing the incident angle of the beam, the amount of deviation can be measured. To perform the alternate cover test, the illuminated eye is covered with an infrared transmitting filter.

Evaluation Studies as Topic↗