WO2007099093A1

WO2007099093A1 - Delivery device with electronically controlled display means

Info

Publication number: WO2007099093A1
Application number: PCT/EP2007/051837
Authority: WO
Inventors: Martin VON BÜLOW
Original assignee: Novo Nordisk A/S
Priority date: 2006-02-28
Filing date: 2007-02-27
Publication date: 2007-09-07

Abstract

The present invention relates to a drug delivery device having an electronic display for displaying a plurality of different data items selected from a list of data items wherein the injection device further comprises an actuatable input member for controlling navigation through displayed data items. The display of the delivery device is configured to display data items and in response to operation of the operable input member configured to scroll displayed data items whereby the movement of each scrolling event is performed in steps corresponding to less than half the height of a displayed data item.

Description

DELIVERY DEVICE WITH ELECTRONICALLY CONTROLLED DISPLAY MEANS

The present invention relates generally to systems for managing medical therapy. More specifically, the invention relates to medical systems having electronic display means for pre- senting parameters relating to the administration of drugs or to the diagnosing of one or more physiological parameters.

BACKGROUND OF THE INVENTION

In the disclosure of the present invention reference is mostly made to the treatment of diabetes by injection or infusion of insulin, however, this is only a preferred use of the present invention.

Commercially available insulin injection devices having provisions for dosing specific quanti- ties of drugs are usually provided with dose indicators for metering the amount of drugs to be injected. Dose indicators in the form of mechanical scales are widely used mostly due to technical simplicity as well as intuitive operation for the user of the device.

However, injection devices having electronically controlled displays are gaining more and more interest mainly due to the prospect of providing more extensive information to the user. Also, the inclusion of memory capabilities in medical devices lead to an increase in information. Ultimately, an increase in the amount and diversity of information accessible by the individual patient is generally linked to the overall aim for each patient to be in better compliance with his or her treatment regimen.

While incorporation of an electronic display in a medical delivery device may increase the amount and diversity of information that can be presented to the user of the device, the intuitive feel associated to the operation of such devices may become somewhat compromised. Specifically injection devices having a small form-factor, such as pen-shaped injection de- vices, have a very limited area for inclusion of a display. Due to the compact display size, and owing to the fact that large font sizes of presented display features are preferred by most users, the design and layout of the graphical user interfaces is somewhat problematic. As the amount of information increases, access to various information by navigation through different information sets may become very complicated and non-intuitive. An example of a prior art disclosure of an injection device having an electronic display can be found in DE 38 24 217 which discloses an injection device comprising timer and control means coupled to the injection actuation means, i.e. the exact time for each actuation of the device, and thus normally for an injection, is automatically captured by the timer and control means and stored in a memory. For each actuation (injection) performed the amount of drug infused is memorized together with a time stamp as in a log book, e.g. 5 units of a given insulin were infused at 4:38. The device is adapted for memorizing a number of such log book datasets which then can be recalled by the patient or any attendant medical staff person.

Further disclosures of injection pens having an electronic read-out can be found in WO patent application No. 90/09202, WO patent applicatino No. 02/092153, US Patens Nos. 5728074, 5509905 and 6585698 and US Patent Application No. 2005/0171476.

As far as these documents concern the actual representation of different parameters to be displayed, the actual read-out of information of each parameter amounts to a somewhat static view of selected parameters. For instance, setting a dose to be delivered is referred to by a displaying a data item such as a number, which changes state instantaneously when a different setting is selected. Hence, the intuitive feel known from mechanical scales or dials is lost.

Some injection devices have larger surfaces for the inclusion of larger sized displays offering the view of several data items simultaneously. Those displays are usually configured so that multiple data items are arranged as nested or stacked lines on the display thereby forming a list of data items where several data items can be viewed at the same time. Usually a se- lected data item is graphically inverted or otherwise highlighted compared to non-selected items appearing from the list. For navigating through these data sets, the user is able to navigate between displayed data items by selecting neighbouring data items, so that the highlighting jumps to the newly selected data item, or alternatively by scrolling the complete list on the display, line by line. However, this way of navigating through data sets is not al- ways optimal in particular if the display is configured to show less than 3 lines of data simultaneously. Further, due to the instantaneous transition from one selected data item to a neighbouring data item, the users perception of navigating through a physical list or scale is lost when navigating to a data item which is not presently displayed. DISCLOSURE OF THE INVENTION

Having regard to the problems and deficiencies identified above, it is an object of the present invention to provide a medical delivery device with a display for communicating information to the user of the device, where the display subsystem facilitates easy navigation through different sets of data ranges. The invention provides intuitive handling of data on the device by presenting information in a manner which improve the users perception of navigating through a physical list of entities, thereby improving the users sense of easy orientation through data sets that may be presented on the display.

In the above as well as in the following, reference will be made to drug injection devices, especially for insulin, however, the present invention may be used in any device within the medical field in which similar situations of use give rise to similar problems.

In a first aspect the present invention is based on the concept that data representing a selected value or entity among a series of values/entities is visually presented as belonging to a list of all possible values/entities.

More specifically, in accordance with the first aspect of the invention, a medical delivery device is provided having an electronic display for presenting various kinds of data or information to the user. Some of the data to be displayed on the display are arranged as lists of data items. The device further comprises an actuatable input member for controlling operation of the device with respect to the displayed data. In response to actuation of the input member, the display is configured to scroll the contents of the display so that current displayed data items are scrolled off simultaneously as consecutive data items appears on the display. By scrolling the presented data items in discrete steps which are less than half the height of data items as displayed, the users perception of navigating through a physical list is improved.

In one embodiment, the list of data items comprises a plurality of distinct numerical values selected from a range of selectable numerical values, so that the entities on the list constitutes a scale. The numerical values may correspond to integers or real numbers, e.g. as representing full or fractional units of a doseable medicament. In a particular embodiment, the data thus presented corresponds exclusively to the selctable dose values, optionally includ- ing a short alphanumeric presentation of the units used, e.g. "12 iu". In such a representation, the doseable values as presented on the display is perceived as a physical dial.

In other embodiments, each data item on the list of data items comprises a mixture of nu- merical values (e.g. dose values) and time stamps, and optionally additional date stamps. In such a list, the format of each data item on the list is substantially identical to the format of all other data items on the list, and the complete list again corresponds to a scale or dial representation. In further embodiments, additional icons may be associated with each data item, where the icon represents an action or condition. For example, an icon representing an air shot or the like is appended to particular data items on the list in accordance with detected conditions or conditions selected by the user.

In a preferred embodiment, the scrolling is performed so that the scrolling appears as a smooth movement. In case that the display is of the matrix type, such scrolling can be ac- complished by pixel scrolling. Other types of displays such as 7-segment displays cannot accomplish smooth scrolling. Instead scrolling is performed in steps corresponding approximately to half the height of a 7-segment display. In other embodiments the scrolling of displayed data items is performed in steps corresponding to less than half the height of a displayed line of information, the displayed line height being defined as the font size.

In a further embodiment of the invention, a particular intuitive user interface is accomplished by ensuring that the user operable input member is rotatably mounted with respect to the device housing, and that the scrolling is performed in a direction perpendicular to the axis of rotation of the input member. The scrolling of the displayed data items may be synchronised with the movement of the operable input member so as to

The operable input member may comprise dose setting functionality, so that doses to be dialed by the input member is presented on the electronic display as a dial scale.

In a still further embodiment, the operable input member contains multiple functionality, so that the input member may be used both for dialing a dose of a medicament to be administered by the delivery device and also for expelling of a set dose. Further, the operable input member may comprise functionality so that the user is able to control various other navigating operations with respect to displayed information without interfering with the dose mecha- nism of the injection device. In a preferred embodiment, the operable input member is con- figured as a dose operable member rotatably mounted along an axis, where the operable member is coupled to a dosing mechanism when in a first axial position, and as a navigating member decoupled from the dose mechanism when in a second axial position. Further embodiments may include an rotatably mounted dose operable member which in addition has capabilities as functioning as a joystick.

In a still further embodiment, the delivery device is provided with a rotatable input member having a predetermined number of rest postions corresponding to a number of angular positions of the rotatable input member. One example may comprise a dose dial knob having a number of discrete dose amounts and corresponding discrete angular positions of the dose dial knob with respect to the housing of the injection device. In such a device, the scrolling performed by the display may be carried out as an animated sequence of stepwise scrollings thereby appearing as a smooth scrolling from one data item to another. The initiation of the animated sequence of partial scrollings can be performed by an encoder system coupled to the dose dial knob where the encoder system senses operation of the dose dial knob in one of the two directions of rotation.

According to a still further embodiment of the invention, the display may be configured to show only a single complete line corresponding to a single data item. Typically, this configu- ration will be chosen in slim injection pens since the display of such devices are comparatively small. Here, the font size of the displayed data items can be maximized ensuring that the displayed data is readily observable even in non optimal lighting conditions. Due to the provision of the scrolling of data items in steps corresponding to less than a full line, e.g. less than the height of a displayed data item, a user of the device may still perceive the data as belonging to a list and hence, the users perception of navigating through a physical scale is not minimized.

In a further aspect of the invention, the displayed data items on the display may be aligned along a longitudinal direction of the screen. In order for both right-handed and left-handed users to be able to equally well use the device, the display may be switchable between a first orientation and a second orientation which second orientation may be oriented upside-down with respect to the first orientation.

As used herein, the term "data item" relates to graphical items including a string of text and/or numbers as well as graphical icons. For example, graphical icons can relate to an ac- tivity performed or to be performed by the user. A "data item" is a separate entity which is sized to be fully displayable within the display area and which corrresponds to one or more parameters related to a condition of the delivery device or a condition associated to the use of the delivery device. Further, a data item may include data associated with a user at a par- ticular point in time. Each data item is independent from neighboring data items and is readily perceivable by the user as being an individual condition, parameter or message independent from neighboring data items. At least one parameter included in the data item and the corresponding parameters in neighboring data items generally relates to the same parameter or condition of the delivery device.

The term "list" corresponds to a plurality of distinct data items that appear vertically or horizontal next to each other. When the data items appear vertically, each data item is represented as a line having neighboring lines corresponding to neighbouring data items. The list may be a physical list of entities or data items that may fully or partly be presented simulta- neously on the display of the device. However, the term "list" also encompasses a virtual list arranged in a storage of the device, and which the user perceives as a physical list, when scrolling through data items displayed on the display, even when the display is configured as showing only a single complete data item on the display.

The term "scrolling" refers to one or more displayed data items being translated in a particular direction on the display. When the display is configured as scrolling through a list of data items, the contents of the display or a fraction thereof are shifted within the display to display new data items in the list and remove previously displayed items.

The term "animation" is the simulation of movement created by displaying a series of bitmaps. The animation lets the user perceive the change as a smooth transition. Thus the impression is avoided of an abrupt confrontation with a new lay-out.

As used herein, the term "drug" is meant to encompass any drug-containing flowable medi- cine capable of being passed through a delivery means such as a hollow needle in a controlled manner, such as a liquid, solution, gel or fine suspension. Further, "drug" is meant also to encompass mediums for nasal or pulmonary administration. Representative drugs include pharmaceuticals such as peptides, proteins, and hormones, biologically derived or active agents, hormonal and gene based agents, nutritional formulas and other substances in both solid (dispensed) or liquid form. In the description of the exemplary embodiments ref- erence will be made to the use of insulin. Correspondingly, the terms "subcutaneous" and "transcutaneous" infusion is meant to encompass any method of transcutaneous delivery to a subject.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be further described with references to the drawings, wherein

fig. 1a and fig. 1 b shows schematic representations of a first embodiment of the invention with the medical device in a mode showing recent delivered doses,

fig. 2 shows a block diagram of electrical components included in the first embodiment of the invention,

fig. 3 shows the embodiment of figs. 1 a and 1 b in a different configuration.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Figs. 1-3 show schematic representations of embodiments of the invention. Correspondingly, the configuration of the different structures as well as their relative dimensions and positions are intended to serve illustrative purposes only.

Fig. 1a shows an injection device for use by a patient for medical self treatment, such a device also being known as a "pen" or a "doser" device.

In the exemplary embodiment shown in fig. 1 a, the delivery device 1 is in the form of an in- jection device having an oblong housing 10 i.e. an "injection pen" for performing a subcutaneous injection of a medicament. The injection device housing 10 comprises a reservoir holder 1 1 for holding a reservoir containing a medicament, a distal end of the reservoir holder 11 being provided with means 12 for engaging an injection needle (not shown) for providing fluid communication with the interior of the reservoir. An operable input member in the form of a dosage knob 20 connected to a metering and injection mechanism (not shown) allows the user to set a desired dose of the medicament to be injected, and also allows for expelling medicament from the reservoir in accordance with the set dose.

A display 50 arranged on the injection device allows for displaying various parameters asso- dated with the use of the device to the user of the device. Also, display 50 may be adapted to indicate other data which may be communicated or downloaded to the injection device from a separate device.

In the present context, the display or monitor may be any sort of display or monitor such as a CRT, a matrix display, a liquid crystal display, OLED, 7-segment displays, i.e. any display being electronically controlled by an electronic display controller can be used.

Data to be presented onto the display 50 may include both historic, present and future dose amount data, time and date or physiological data relating to physiological parameters of a user. Various other parameters may be provided for displaying on display 50, such as icons representing actions relating to the use of the device or performed by the user.

Preferably, the injection device is configured to be switched between a plurality of modes. Hence, when the injection device is switched into a particular mode, the display may be adapted to show a particular set of data which is different from data presented in other modes.

In the depicted embodiment of fig. 1a, the display is in a mode configured to show data pertaining to a history of delivered doses administered by the delivery device. The data may in- elude data relating to date and time, dose amounts of recent delivered doses, proposed dose amounts as determined by a processor or blood glucose levels obtained at respective times. In the depicted embodiment, each line includes a time stamp and a dose amount, whereas each line defines a single data item.

As some diabetic patients have impaired vision, the display may be configured for maximizing the font size of displayed data. Due to the physical shape of the depicted injection pen, the display is configured as showing a single line of data items. However, the display may be designed also to include the spacing between the shown data item and the neighbouring data items. In other configurations, the display may be configured to cover also fractions or complete data items of the neighbouring entities on the list. Also, the injection device may be designed so that the user is able to configure the font size presented on the display to suit the particular needs of the user. In this way, the device can be configured to be switchable between a plurality of different font sizes.

In fig. 1a, a virtual list containing a plurality of data items is indicated schematically depicted by reference numeral 55. In the shown embodiment, the list is not presented on the display 50 at one particular time. Rather, the list 55 refers to a list that the user perceives as a list when navigating through the various data items.

The injection device may be provided with various operable input members 20 for controlling the operation of the pen and for navigating and selecting between data items to be presented on display 50.

The operable input members may comprise push buttons, rotary knobs, operable input members performing as a joystick, i.e. input members having a rest position and one or more user activatable biased positions activating navigation or selection of particular data items presented on the display. The mentioned joystick capability may be included in a rotary knob, whereby the operable input member provides a two-fold operating capability.

When the injection device is in a dose dial mode, the display 50 preferably displays the selected dose amount to be injected by the injection device 1. In other modes of operation, the display may be switched to show other data. Dosage knob 20 may be implemented to control the switching between modes of the injection device. For instance, dosage knob 20 may be designed to be pulled away from housing 10 into an extracted position thereby controlling the display without affecting the operation of the dose mechanism of the injection device.

Alternatively, a further operating member may be contemplated for navigating through the displayed data items presented on display 50. Such further operating member may comprise a second knob arranged coaxially with respect to the dosage knob 20. An alternative design may incorporate a ring shaped member arranged on the housing a specific distance from dosage knob 20. Such ring shaped member may be arranged to be mounted on the delivery device so that the ring shaped member may be rotated with respect to the housing for accomplishing navigation of the displayed items and may even be, for selection purposes, adapted to be slideable mounted along the length of the delivery device. A further embodi- merits may comprise a pen cap which, when mounted on the delivery pen, acts as an operable input member.

In the embodiment shown in fig. 1a, the operable input member includes a dosage knob 20 which is rotatable along an axis parallel to the axis of the elongate housing 10. The injection device 1 is provided with electronic circuitry which comprises the electronic components shown in fig. 2.

Dosage knob 20 is coupled to a dosage knob encoder 30 for encoding the rotational position of dosage knob 20 with respect to the housing 10. The dosage knob encoder 30 determines the dosage of medication to be injected based upon the number of rotations of dosage knob 20. The dosage knob encoder may comprise one or more sensors which may be selected from any appropriate sensing means for determining the number of rotations, whether complete or incremental, that adjusting knob 12 undergoes in setting the dosage. Sensor means may employ electromechanical, optical, magnetic, piezoelectric, inductive or other means.

The number of rotations of dosage knob 20 as sensed by the dosage knob encoder 30 is translated into a dosage amount by the display controller 40 which may comprise microprocessor circuitry. The display controller 40 provides the dosage information to display 50. If the injection device is in a mode for administering insulin, the display then presents the dose selected by the user.

Further not shown electronic elements include a storage for storing various parameters to be displayed on display 50. Also, the circuitry includes a power supply for supplying electrical power to the various electrical components included in the injection device. The power supply may comprise a battery, a capacitor which may be supplied with energy either by wired connection or inductively from an external induced electrical field. Also, the power supply may be selected to include power generating means driven by user activatable members integrated in the pen. For instance, the device may be adapted to include power generating means, so that the operation of dosage knob 20 with respect to the housing generates power to be accumulated in the poser supply. Also the technology known from watches having an automatic movement can be incorporated in the medical delivery device.

In response to activation of the dosage knob 20, a presented dose amount on display 50 is scrolled, e.g. shifted up or down on the display. Fig. 1 b shows one situation after operation of dosage knob 20 has been initiated. Here the list is scrolled upwards so that the initially displayed data item gradually is replaced by a new data item introduced on the screen from below.

In accordance with one aspect of the invention, the scrolling is performed in discrete steps corresponding to less than a complete line as defined by the height H (shown in fig. 1 a) between midpoints of two consecutive data items on the list 35.

In accordance with another aspect of the invention, the scrolling is performed in discrete steps corresponding to less than the height of a complete line as defined by the height of a single data item S when presented on the display (also shown in fig. 1a). More preferable, the discrete steps corresponds to less than half the height S.

Preferably, the actual performance of the scrolling is selected in accordance with the particu- lar design of the display, the encoding sub-system and the dosage knob movement.

The scrolling may be performed in smaller or larger steps according to the type of display incorporated in delivery device 1. If a 7-segment display is used, then scrolling is performed in steps corresponding to approximately half the height of the seven segment display.

If a display type is used incorporating a matrix of addressable pixels, scrolling movement may be implemented in more or less fine steps. Preferably the scrolling is performed in discrete steps so that smooth scrolling appears to occur. Finer scrolling modes such as single pixel movements are also possible.

In one particular embodiment of the invention, the scrolling of the displayed items are coupled to the rotation of the dosage knob 20 so that the velocity of the scrolling is adapted to the velocity of movement of peripheral surface of the dosage knob 20, when rotated. If the dosage knob encoder is able to discriminate between a large number of angular positions of dosage knob encoder 30 so that a virtually continuous sensing is performed, the display can be adapted to scroll in corresponding fine increments.

In further embodiments, the dosage knob 20 may be designed to be operable in discrete angular steps corresponding to specific doseable quantities to be administered by the injection device. If the dosage knob encoder has a sensing scheme corresponding to relatively coarse steps, the display scrolling may be adapted to perform an animated sequence of discrete scrolling movements so that the scrolling appears as a smooth transition from the displaying of a first data item to a neighbouring data item. The stepwise movement of the dosage knob 20 may initiate the animated sequence of scrolling. In this way, even though the dosage knob movement is not directly synchronized with the scrolling movement, the user of the device still perceives the displayed data items as a list of entities resembling the view and feel of a mechanical dose scale. If the sequence of rotation of dosage knob 20 is performed rapidly, the scrolling may be programmed to accelerate the animated scrolling sequence, so that the perceived list of data items is able to catch up with the dialed dose as selected by dosage knob 20.

In one embodiment, the list of data items to be displayed by the display, is arranged as an endless loop when scrolling through said list.

The display may be designed to include several display areas, where only some of the display areas are scrolled while remaining display areas are remaining unaffected by said scrolling.

In a further aspect of the invention, the display device may be configured to be switchable between different display orientations. In this way, the display may be configured to be switchable from the configuration shown in fig. 1 a to a configuration shown in fig. 3. If a user holds the injection device in the right hand the display is inverted to that shown in fig. 3 so that the bottom right corner, as viewed by a right handed user, becomes the top left corner as viewed by a left handed user. This feature may be implemented independently with the scrolling feature of the display 50.

Although only a few exemplary embodiments of the present invention have been described in detail above, those skilled in the art will appreciate readily that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the invention. Accordingly, all such modifications are intended to be included within the scope of the present invention as defined in the following claims.

In line with the invention as set forth above, the invention is generally applicable to medical delivery devices regardless of the kind of administration route for delivering a beneficial agent to the user. Also, the invention may be implemented in both injection devices of the non-motorised kind as well as motorised dosers. Further, the invention may be adopted to be used in connection with medical equipment for presenting displayed information on the basis of an analysis of a physiological characteristic, such as within a blood glucose meter.

In the above description of the exemplary embodiments, the different structures providing the desired relations between the different components just as the means providing the described functionality for the different components have been described to a degree to which the concept of the present invention will be apparent to the skilled reader. The detailed construction and specification for the different structures are considered the object of a normal design procedure performed by the skilled person along the lines set out in the present specification.

All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference in their entirety and to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein (to the maximum extent permitted by law).

All headings and sub-headings are used herein for convenience only and should not be construed as limiting the invention in any way.

The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. The citation and incorporation of patent documents herein is done for convenience only and does not reflect any view of the validity, patentability, and/or enforceability of such patent documents.

This invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law.

Claims

1. A medical delivery device comprising:

- an electronically controlled display (50) for displaying data items selected from a list of data items,

- a display controller (40) adapted to control said display (50), and

- an operable input member (20) coupled to the display controller (40), and wherein the controller (40) and the display (50) are configured for displaying a portion of said list of data items and configured for scrolling displayed elements so that displayed data items are scrolled in response to actuation of the operable input member (20), characterized in that the data items on the list each comprises a numerical value selected from a range of numerical values and that the controller (40) and display (30) are adapted to perform display scrolling from one data item to a next consecutive data item in discrete steps which corresponds to less than half the height of a data item as presented on said display.

2. A medical delivery device as defined in claim 1 , characterized in that the operable input member (20) is a rotary knob having an axis of rotation and that said controller (40) and display (50) are configured for scrolling displayed data items in a direction perpendicular to said axis of rotation.

3. A medical delivery device as defined in claims 1 or 2, characterized in that the delivery device comprises a mechanism for metering and injecting doses of one or more drugs to be administered by the delivery device, and that the user operable input member (20) comprises a rotatable dosage knob for setting doses and that said display (50) is configured for displaying data items corresponding to settable dose amounts.

4. A medical delivery device as defined in claim 3, characterized in that said rotary dosage knob can be positioned in two or more axial positions, so that in one of said positions, said dosage knob can be moved independently of said mechanism for metering and injecting doses.

5. A medical delivery device as defined in any of claims 1-4, characterized in that the operable input member (20) comprises is a rotary dosage knob that can be rotated in dis- crete angular positions and that scrolling is performed as a sequence of two or more discrete scrolling steps, thereby presenting the scrolling as an animated sequence when the rotary dialing knob is rotated from a first angular position to a second angular position.

6. A medical delivery device as defined in any of the claims 1-5, characterized in that the operable input member (20) comprises an operating member having a rest position and one ore more distinct biased positions when biased by an external force component, and switching means for signaling the operation into each of said biased positions to said control- ler (40).

7. A medical delivery device as defined in any of the claims 1-6, characterized in that the delivery device includes a housing (10) having an oblong configuration and that the controller (40) and display (50) are configured for simultaneously displaying less than two com- plete data items from said list of data items.

8. A medical delivery device as defined in claim 1-7, characterized in that the display (50) has a matrix of pixels, and that the scrolling of displayed data items are performed in steps corresponding to the display resolution.

9. A medical delivery device as defined in any of claims 1-8, characterized in that the display defines an image plane having an image plane normal axis and that orientation of the data items on the display (50) can be selectively switched from a first orientation to a second orientation by rotating the displayed data items 180 degrees around said normal axis.