GB2323281A - Apparatus for testing the extra-ocular eye muscles - Google Patents

Abstract

The apparatus, which tests the eye muscles by a combination of motility and near and far fixation, comprises a larger card bearing eight numbers arranged radially as shown and a smaller card also bearing eight numbers and having an aperture through which the larger card is viewed. The subject stands 1 m. from the larger card and about 20 cm. from the smaller card and recites the numbers in a clockwise direction alternating between the near and far cards, the time taken to do this providing a comparative measure of muscle physiology. Also disclosed is apparatus comprising an array of illuminatable diodes, a microprocessor and infra-red, eye movement-detecting "spectacles", the arrangement being such that as each diode swiches on, the subject looks towards it to switch it off as quickly as possible.

Description

DYNAMIC FIXATION -A TEST FOR MEASURING THE SPEED OF EYE MOVEMENT DESCRIPTION Dynamic Fixation measures the performance of the extra ocular muscles by eye movement (a combination of motility and near and far fixation) Using two cards (see Fig 1), the subject is timed for 24 near, far near, vergence cycles. The test aims to reduce thinking time to the point where the speed to the extra-ocular muscles becomes the most significant contributory part of the time taken for the test.

BACKGROUND In the original research three groups were tested, 28 Club and Intemational track and field athletes, 13 International archers and 18 Non-Athletes (otherwise healthy people who do sport for recreation). Significant differences in the mean times for these groups were found.

It is proposed that the performance of the extra-ocular muscles is innate and unaffected by the extemal rigours of athletic training or the lassitude of the couch potato. Since all skeletal muscles have the same basic physiology and locomotion is dependant on the development of muscle strength, the eye muscles could also be a predictor of athletic potential.

The significance of athletic potential goes beyond the sports arena and would be a useful clinical tool. It could give an indication of muscular metabolism and show where this is at odds with life style. In view of the connection between health and exercise, it would allow practitioners to prescribe an appropriate form of exercise.

In future the test may be developed to compare the performance of international athletes in different sports, it could also be used to develop eye speed, if this appears to be important in some events.

The test could measure the rate of extra-ocular fatigue and the different effects of aerobic and anaerobic exercise. The test may be useful to train relaxation and switching off thought, which sometimes inhibits athletic performance. The numbers could be read anti-clockwise and the duration and repetitions increased, according to any new conditions which the experimenter chooses to investigate.

QUESTIONNAIRE The questionnaire (See Fig 2) is designed to give a broad profile of each subject, although apart from name address and date the only specific details needed for the test are age, sport and involvement. Additional details which would be useful include, light level, location, time of day and current activity level. (before or after training, resting) SETTING UP APPARATUS Distance Chart (see Fig 3) This needs to be positioned with its centre at the eye level of the subject. The best that can be said is that it was positioned at the average height. The effect of being too low or too high could be to favour either the depressors or the elevators in the extra ocular muscles, which could affect results. However if a sport is played habitually above or below eye level then the height could be adjusted accordingly after normal readings are taken.

Eye Position A distance of one meter normal to the distance chart is measured out on the floor and marked with white tape. The subject stands with their toes on the line so the distance of their eyes to the centre of the target approximates to one metre. This allows for body lean so that the centre of rotation of the globe is roughly in line with the one metre marker. (see Fig 4) METHOD INTRODUCING THE TEST The test is introduced by saying, "This test is a measure of the performance of the eye muscles. It does this by making them move in and out and in different directions. What I would like you to do is hold this card (near card see Fig 5) and look through the hole so that you can see all the numbers of the chart with both eyes1 without moving your head or the card." At which point the card can generally be passed to the subject who is asked to stand in position, with their toes on the metre line. (see Fig 6) Some subjects with strong dominance or amblyopia tend to line the hole up with their dominant eye, this tendency should be checked by looking at the positioning of the card and corrected if necessary.

Near Card Distance Control In the correct position the hole size acts as a control, keeping the near card from drifting too far away from the eyes, where all the letters will cease to be seen by both eyes. This should be about 20cm from the eyes.

Instructions Once they have discovered how to position the card the numbers are pointed out, " What I will be asking you to do is read out the numbers aloud, starting with the number 1 on the near card and then going to the 4 and back to the 7 and so on in a clock-wise direction." Demonstration The explanation is helped by demonstration, but the test should be handed over to the subject as soon as they are ready to have a go. The best way to learn the test is to do it and allow questions to clear up misunderstandings.

Language If the subjects first language is not English, they can be given the choice of saying the numbers in their mother tongue.

Practise The subject is then given a chance to practise, getting used to saying the numbers and proceeding in the right direction, going from near to distance and back, not the other way round. Onoe the idea had been understood the subject is asked to continue reading round the clock for 3 circuits starting and finishing with the top number 1.

Stop Watch The next step is to take a time, but not record it " In a moment I will be taking a time just to get you used to the stop watch, but will not record the result." This achieves two things: To de-stress the taking of a time (for track athletes in particular this has particular significance) To make sure the test is thoroughly leamed, so that it can be performed without excessive concentration on the method.

Cortical Processing The aim is that the test shouldn't be leamed so well that the numbers are memorised, but well enough to reduce cortical processing to a minimum. The size and distance of the targets, the predictable arrangement and positions of the numbers have already been designed to reduce this effect.

RECORDING The subject is now told that a time will be taken on the next run with the final instruction: " Try to read the numbers as quickly as you can but make sure you look at them before you say them. Try to relax and put your mind out of gear. I will start the watch when you say the first number 1 and stop it when you say it for the 4 th time. (after the 3rd circuit of the chart, this gives 24 near-distance-near cycles ) I will be taking a time for 3 sets of 3 circuits." At the beginning of each set say, " Are you ready ? OK, in your own time, start with the top number 1." The times are recorded on the data sheet shown in the appendix It is helpful to observe eye, head and body movement during the test. in particular the eyes may appear to fixate precisely as instructed, or have a smoother circuit using peripheral vision. Eye movement should be recorded Peripheral or Precise. ( see Fig 7) Data After each set the time should be recorded immediately (see Fig 7) and the second set started as soon as this is done, the interval between the readings is standardised in this way. In what could be a partially anaerobic exercise for the extra-ocular muscles, recovery time is important and should be consistent.

CHARACTERISTICS OF DYNAMIC FIXATION Recreation The recreational subjects, who have no specific sporting ability, have relatively slow times (Third reading 17.48) and a high average standard deviation between the readings (1.59) Non Dynamic Sports (Control) o Low standard deviation between the three readings, (1.09) Low speed (third reading 17.41) (Muscle type 1, control or Non dynamic) Dynamic Sports (Explosion) High standard deviation between the initial three readings (1.23) High speed (third reading 14.88) (Muscle type 2, explosion or dynamic) Eye Movement The eye movement can be either Type 1 movement, precise.

or type 2 movement, peripheral.

Standard Deviafion From The Mean A high figure for the standard deviation from the mean, may indicate an -homogeneous group as far as muscle type is concerned. This can apply to elite groups as well as recreational.

Deviation Ratio This is a measure of the suitability of a sport to the muscle types who participate in it. For healthy participation it should approach or possibly be less than the ratio for the club athletes which is 1.45 SIGNIFICANCE OF THE READINGS The most significant reading is the third, but the way in which the readings improve suggests that all the readings contribute to the interpretation of the results. The use of the stopwatch is also an integral part of the procedure, not just to record results but as a presence, which implies different things to different people. It conveys an atmosphere of urgency and concentration, which is likely to affect results. Even though the third reading is the most significant it cannot be isolated and has to be taken at the conclusion of the correct method, in the allotted space of time.

For casual timings on the apparatus the means of the groups probably give an adequate guide: (see Table) Table 1 Comparison of Means

GROUP MEAN International 15.87 Club 16.33 Recreation 18.68 Archers 18.20 FUTURE DEVELOPMENT

SACCADIC FIXATOR Self illuminating diodes, activated o o by eye movement o o O o o o 0 0 0 0 0 Micro Processor P 14r1II , 1' --- Infra red, eye movement detector.

Subject METHOD As each diode switches on the subject looks toward it to switch it off. Eye movement and the saccadic fixator connected electronically by the infra red eye movement detector, wom like a pair of glasses. The control is achieved by the same principle as the mouse control on a personal computer and relates direction of gaze to a precise location on the Fixator.

The lights are illuminated and turned off as quick as the eyes can look in the appropriate direction. This is the principle of the Dynamic fixator with out the need for speech or number recognition. Various light pattems will be used to establish the most reliable combination.

This method allows all the existing programmes of the Saccadic fixator to be controlled by eye movement exclusively.

Claims (10)

1. Dynamic Fixation is a test for measuring the performance of the extraocular muscles of the eye by a series of motility movements and near, far fixations.

2. A test as claimed in Claim 1 which is a two card test, consisting of a large wall mounted card at one metre (distance) and a smaller hand held (near) card at 20 cm

3. A test as claimed in Claim wherein the distance card in Claim 2, is viewed through a hole in the near card in Claim 2.

4. A test as claimed in Claim 1 wherin the hole in the near target in Claim 2, is the control for the distance at which the near card is held from the eyes of the subject

5. A test as claimed in Claim 1, wherein the hole in the near card as claimed in Claim 3, is a control for the height at which it is held.

6. A test as claimed in Claim 1 wherein the Fixation Targets on the cards, as claimed in Claim 2, are numerical and randomly numbered from one to ten.

7. A test as claimed in Claim 1 wherein the targets are fixed in concentric circles on the two cards as claimed in Claim 2, at the eight points of an octagon.

8. The targets as claimed in Claim 6, are large low contrast and non accommodative.

9. A test as claimed in Claim 1 wherein the surfaces of the two cards as claimed in Claim 2, are non reflective.

10. A test as claimed in Claim 1 wherein the height of centre of the wall mounted card as claimed in claim 2 is adjustable to the eye level of the subject.