GB2398631A

GB2398631A - Computerised assessment of the ocular motility fileds

Info

Publication number: GB2398631A
Application number: GB0229556A
Authority: GB
Inventors: Ahmed A Assaf
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-12-19
Filing date: 2002-12-19
Publication date: 2004-08-25
Also published as: GB0229556D0

Abstract

A computerised method for testing Ocular Motility fields relates to the assessment of strabismus patients. It can be used to assess both binocular and monocular fields of eye movements. A patient places his chin on an adjustable chin-rest and the appropriate adjustment in position is made. The chin-rest is mounted on a motorised table, along with a computer display. A target is moved along meridians on the display at regular intervals around 360 degrees. The apparatus may be used to test the field of Binocular Single Vision, for which both eyes are kept open. The position of the target is recorded at the point where the target is seen in double. This is repeated at different meridians. For testing the field of Monocular eye movements one eye is covered. Appropriate adjustment to the chin-rest is made. The patient follows a moving target generated along various meridians as above. In both tests, the results are saved along with patient and test data.

Description

J

239863 1 Computerised assessment of the Ocular Motility Fields

TECHNICAL FIELD

This invention relates to motor assessment of strabismus (squint) patients.

FIELDS OF OCULAR MOTILITY

Fields of ocular motility are two types:

1. Field of binocular single vision (BSV)

One of the main symptoms of squint in older children adults is diplopia. The field of BSV is used to assess the parts of the visual field in which the patient sees objects singly versus the parts in which he/she sees the objects double. This test is done with both eyes open.

2. Uniocular field of fixation

This test is used to chart the extent at which each eye (while its fellow eye is covered) can move away from the primary position along in various parts of the visual field.

Both the above tests are useful in monitoring the progress of the patient with certain types of squint with time or following surgical procedures.

PREFERABLE TECHENICAL FEATURES

This invention consists of both hardware and software components: 1) Large computer display (screen or other forms of display), with computer.

2) Adjustable chin-rest and headrest, both laterally and in the up and down position.

It is useful also to have chin-rest be adjusted along the anteroposterior axis, i.e. adjust its distance from the screen (figure 1) 3) Both the screen and chin-rested are mounted on a motorised table the height of which can be adjusted.

4) An input device, such as mouse, trackballetc.

5) A digital camera at the centre of the display to monitor fixation.

6) Software.

The chin rest has 3 positions: a. In the middle for the use of the field of BSV: the middle point between the two eyes faces the centre of display (screen).

b. To the left to test the right eye: the right eye directly faces the centre of display.

c. To the right to test the left eye: the left eye directly faces the centre of display.

The chin-rest is also movable up and down to allow adjustment of the eye position vertically to correspond to the level of the centre of the screen.

If the chin-rest is adjustable in the antero-posterior axis, the distance between the display and the chin-rest (or the eye position) is adjusted to correspond to the required extent of peripheral field testing in degrees as allowed by the size of the display (screen).

Screen Grid: The display (screen) may have a grid representing the degrees away from the centre in concentric fashion; say every 5 to 10 degrees. Radial line can also be drawn to represent the degrees from O to 360 say every 10 or 15 degrees. The zero reference point can be taken at any place along the face of the clock. In this case, I will choose to start from the 12 o'clock going in clockwise direction till 360 degrees when reaching 12 o'clock position again, but this could be in any other arrangement (figure 2).

Alternative device features: 1. The display can be of any forms of computer display such as, but not limited to, projection via LCD projectors or displayed in virtual reality glassesetc.

2. The digital camera at the centre of the screen to monitor fixation is optional.

Alternatively, the monitoring of fixation mechanism could take any other form of transmitting the position of the eye to the examiner.

3. The eye position is monitored via an eye position tracking system.

4. The chin rest is at a fixed distance from the display, i.e. no movement along the antero-posterior axis.

5. The screen is moved laterally and forwards while the chin-rest is fixed.

6. The above device can be used to conduct the visual field test.

Testing distance: This is the distance between the patient eyes (while he/she is positioned at the chin- rest and forehead against the head rest) and the centre of the display. The testing distance will depend on the size of the display. Ideally the size of the display should allow testing in parts of the visual fields of minimum 20 and up to 70 away from the

centre of the visual field.

TESTING METHODS

Before examination the inter-pupillary distance (IPD) for the patient is measured in millimetres.

I) Testing the f eld of ASH: When testing the field of BSV both eyes were kept open. The chin rest is in the central position and the distant between the display and the patient eyes is adjusted to allow the required the degrees of peripheral visual field testing.

The patient is seated in front the chin-rest. The motorised table is adjusted to the required patient height. The patient places his chin on the chin-rest and centre of the screen faces the centre between the 2 eyes. The chin-rest is adjusted vertically so as the position of the eyes is level with the centre of the screen.

A target is displayed at the centre of the screen. When the test is ready to be conducted the object is moved by the computer (or the operator using a keyboard) along the start meridian away from the centre. The speed of the movements of the target can be varied by the operator to suite the ability of the patient. The patient is asked to follow the target with both eyes open. At the time he starts to see the moving target double she/he can clicks the mouse. This position is recorded by the computer as the position at which diplopia (if any) is first seen along that meridian.

Alternatively, the patient announces the point at which he sees the moving target double and the operator enters the point through the keyboard or mouse. The moving targets could be of any appropriate shape or colour. (The target could be moved peripherally towards the centre recording the point at which double vision is seen singly).

The same process is repeated along all the other meridians around the 360 degrees, say at 10-15 degrees intervals. Testing of any meridian could be repeated if in doubt.

Also it should be possible to step backwards and repeat testing of any meridian/s in question. I Once the whole 360 degrees field is covered, the points at which double vision is first seen at various meridians are connected to the neighbouring ones on either side. This results in delineation of the field of vision at which objects are seen singly.

II) Testing uniocular f eld offL,cation: In this instance each eye is tested to degree of movement of each eye while its fellow eye is covered.

Initial chin-rest adjustment is carried as above. If the right eye is to be tested, the left eye covered. The chin-rest is then moved to the left by an amount equal to half of the IPD, or the eye position can be monitored through the digital camera until the position ' of the eye is central. r As above a moving target is displayed started from the centre in a particular meridian.

The patient is asked to follow the target until it disappears of view. The end point is when the patient stops looking at object directly or stops following the object as it moves outwards. The computer via the patient or operator records this position as above. The same process is repeated along all the other meridians around the 360 degrees, say at 1015 degrees intervals. Testing of any meridian could be repeated if in doubt. Also it should be possible to step backwards and repeat testing of any meridian/s in question. Once the whole 360 degrees field is covered the test ends. At the end of the test, the result is displayed by connecting the points at which the target disappears to the adjacent points.

The same process is repeated for the second eye. The chin-rest in this case is moved so the eye to be tested is directly facing the centre of the screen and the fellow eye is covered.

The test result in both above tests can be saved along with the patient and test details.

Other tests can be added at a later date. The test results can be analysed electronically to assess and compare change with time or postoperatively.

Claims

1. Ocular Motility Fields Tester consists of both hardware and software components: the hardware consists of a computer system with an appropriate display and an input device such as trackball or similar; adjustable chin-rest and head-rest; and a motorised table with adjustable height; the software, on the other hand, is used for the testing process and manipulation of the test results.

2. Ocular Motility Fields Tester as claimed in Claim 1 wherein an appropriate target, used for testing, is moved radially along meridians at specific interval around the 360 degrees.

3. Ocular Motility Fields Tester as claimed in Claim 2 wherein patient fixation can be monitored during the testing process.

3. Ocular Motility Fields Tester as claimed in Claim 2 wherein the field of binocular single vision is tested.

4. Ocular Motility Fields Tester as claimed in Claim 3 wherein the monocular field eye movements can be tested.

5. Ocular Motility Fields Tester as claimed in Claim 4 wherein patient fixation can be monitored during the testing process.

ts to the claims have been filed f Cl,AIMS 1. Ocular Motility Fields Tester comprising of both hardware and software components: the hardware consists of a computer system with an appropriate display and an input pointing' device; adjustable chin-rest and head-rest; and a motorised table with adjustable height (figurel); the software is used for the assessment of field of binocular single vision by testing eye movements radially along meridians at specific intervals around the 360 degrees (figure 2) and manipulation of the test results.

2. Ocular Motility Fields Tester as claimed in Claim 1 wherein the monocular field eye movements can be tested.