GB2382252A

GB2382252A - Portable visual stimulators

Info

Publication number: GB2382252A
Application number: GB0124634A
Authority: GB
Inventors: Alki Liasis
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-13
Filing date: 2001-10-13
Publication date: 2003-05-21
Also published as: GB0124634D0

Abstract

Two visual stimulators, intended for stimulating a response enabling measurement of visual evoked potentials (VEPs) in a patient (13,14) are arranged in a manner that allows them to be independently adjustable. The arrangement allows a user to adjust the orientation of each stimulator independently such that it is suitably aligned with the visual axis of each eye, thereby ensuring that effective binocular stimulation is achieved, irrespective of ocular misalignment. Each stimulator is capable of producing high spatial resolution images via miniature cathode ray tube arrangement (10, fig 4). The stimulators are designed in a compact manner so as to be portable, thereby enabling the system to be easily transported to a patient who may not be able to visit a testing laboratory.

Description

Hand held micro visual stimulators.

This invention relates to visual stimulators that include the type used for electrodiagnostic recordings during acquisition of Visual Evoked Potentials'VEP' (responses that can be recorded from the scalp in response to a time locked stimulus).

During routine clinical testing a large screen positioned a specific distance from the patient is used to deliver the stimuli (usually consisting of a reversing checkerboard). In most cases this methodology is fine during binocular testing when both eyes fixate on the screen, and during monocular testing when one eye fixates on the screen during stimulation.

Conventional visual stimulation (as described above) may be inadequate during VEP recordings in patients who are unable to attend the electrophysiology laboratory and those with abnormal eye alignment and/or movements. It is essential to record reliable VEPs in these patients as they are an integral part of the assessment of visual loss. Their reliability is essential as the results influence diagnosis, therapy and prognosis.

The first objective of this invention is to produce a portable visual stimulator that can be used to present high spatial resolution stimuli during the recording of monocular and binocular visual evoked potentials in patients away from the laboratory.

The second objective is to enable the recording of monocular and binocular VEP recordings in IZ > patients with abnormal eye alignment and movements.

The essential features of this invention are: 1) a stimulation system that is small and as a result can be hand held or attached to some form of head mount and therefore can be used away form the laboratory (i. e. portable).

2) the independent movement of the individual micro stimulators enables the visual stimulators to be aligned to the axis of the patients eyes even if they are not aligned.

3) the ability to present complex patterns via the micro stimulators CRO tubes ensures the visual stimulation is comparable video or computer generated images used during routine clinical testing..

Figure 1. Top View of micro stimulator Figure 2. Front view of micro stimulator Figure 3. Side view of stimulator.

Figure 4. Internal workings of stimulator shown from top.

Figure 5. An example of the invention being used. c Referring to the drawings (Fig 1-3). Two micro stimulators are connected together by a'scissors' mechanism'1 & 2'that allows the independent movement of each micro stimulator away and towards each other. Each of the micro stimulators is attached to the connecting mechanism via a stalk'4'that allows vertical movement of the stimulators and is held in that position by a fixing screw'8'. In addition the stalks are connected to the stimulators via a spherical bearing'9'that allows the micro stimulator to be rotated in any orientation.

The outer casing'5'enables the stimulators to be held by hand or clamped to another device for example cap support.

The rubber eye caps'7'ensure there is a light proof seal between the stimulator and the eye.

The image presented to the subject by the CRO tube'10'is kept in focus by adjustment of the viewfinder'6'that when twisted results in movement of the viewing lens'12'backwards or forwards. The micro stimulators receive video, VGA and power via the connector block'3' located at the end of the stimulators.

An example of where this invention is applicable is during the recording of VEPs in patients with unaligned eyes'strabismus'. During conventional stimulation techniques the patient is asked to fixate on the stimulating screen in front of them. In patients with strabismus only one eye can look at the screen at any time. Figure 5 shows how the stimulators are positioned in normal subjects'13'and in a patient with unaligned eyes'14'. The movement of the micro stimulators

allows the visual displays to be aligned with each of the eyes regardless of the position of the eye.

The drawings. Figure 1. Top view of both micro stimulators connected together.

Figure 2. Side view of one micro stimulator. Figure 3. One of the connecting arms.

Figure 4. Top cross section view of one micro stimulator.

0 Figure 5. An example of the micro stimulators used in a control subject and a patients with strabismus.

Claims

CLAIMS.

1. A portable hand held visual stimulator employing CRO tubes that can deliver high spatial resolution images.

2. A visual stimulator as in Claim 1 where the stimulators arise from two micro stimulators enabling stimulation of each eye individually.

3. A visual stimulator as in Claim I & Claim 2 where the two micro stimulators are connected together in such away that enables the two micro stimulators to be moved into any position independently

4. A visual stimulator as herein described and illustrated in the accompanying drawings.

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