GB2620628A

GB2620628A - Device for imaging eye

Info

Publication number: GB2620628A
Application number: GB2210393.1A
Authority: GB
Inventors: Bell Stephen
Original assignee: Ocupeye Ltd
Current assignee: Ocupeye Ltd
Priority date: 2022-07-15
Filing date: 2022-07-15
Publication date: 2024-01-17
Also published as: GB202210393D0

Abstract

A device 1 for aiding imaging of an eye and/or eye socket, the device comprising: a body 3 arranged to be inserted into the eye socket, the body 3 having: a curved peripheral edge portion 9; a rear surface 7 forming part of the curved peripheral edge portion 9 and configured to engage the surface of the eye; and a front surface 5 forming part of the curved peripheral edge portion 9 and having a more centrally located flat region 13 defining a target area for scanning, e.g. a window for corneal imaging. One or more through-holes 41 extend through the body 3 remote from the central target area. A forwardly extending annular sidewall 23 may hold the eyelids apart during imaging. Another access device comprises a similar body with eye engaging rear surface and forwardly projecting sidewall for separating the eyelids, but instead of the front surface for imaging, a central aperture (11, Fig. 8) extends through the device to allow surgical access to the eye.

Description

DEVICE FOR IMAGING EYE

The present invention relates to a device for holding an eye of a patient open. The device may be for aiding imaging of an eye and/or eye socket of the patient. The eye may be fully or partially °nucleated or anophthalmic, microphthalmic, or a healthy eye.

WO 2021/038 243 discloses a method of making an ocular prosthesis for a patient. To make the prosthesis, it is necessary to capture images of both the healthy socket and the socket in which the prosthetic will be worn. This ensures so the structure and appearance of a healthy eye is replicated, and the prosthesis is a good fit. Imaging may include scanning by photography, optical coherence tomography (OCT), or other two or three dimensional scanning techniques to capture the appearance and three dimensional structure of the interior and/or exterior of the eye. I5

In order to capture a sufficiently large area to make the prosthetic a good fit and match the appearance of the healthy eye, it is necessary to hold back the eye lids of the patient. Typically, this is done with tape, an eye speculum or other suitable tool. This is uncomfortable for the patient, and difficult for the imaging technician or doctor. Furthermore, the amount the eves are held open varies significantly from patient to patient.

In addition to the above, during analysis of the images, it is necessary to have a clear imaging area, without imaging artefacts, whilst providing a reference point for analysis of the captured image.

According to a first aspect of the invention, there is a device for aiding imaging of an eye and/or eye socket, the device comprising: a body arranged to be inserted into the eye socket, the body having: a curved peripheral edge portion; a rear surface forming part of the curved peripheral edge portion and configured to engage a surface of the eye socket; and a front surface forming part of the curved peripheral edge portion and having a flat region located away from the curved peripheral edge portion of the body, the flat region at least partially defining a target area for scanning, wherein the body includes one or more through-holes extending through the body, the through-holes located away from the target area.

The flat region reduces reflections and other artefacts when an image is taken, and provides a reference point for analysis of the image. The provision of through holes prevents condensation forming, which would also be detrimental to image quality, and the arrangement of the holes away from the flat region ensures the through holes do not impinge on the image taken.

A thickness of the body in the flat region may be less than a thickness of the body in the part of the curved peripheral edge portion surrounding the flat region. This ensures the device has minimal attenuation of any imaging signal.

The body may comprise a recess extending from the rear surface towards the front surface, aligned with the flat region. The recess provides the reduced thickncss. The recess may narrow towards the front surface, measured in a direction parallel to the I5 flat region on the front surface.

The recess may have a flat inner surface extending parallel to the flat region of the front surface. This further reduces reflections and other artefacts when an image is taken When viewed perpendicular to the flat region of the front surface, the flat region of the front surface may overlap the flat inner surface of the recess in all directions The flat inner surface of the recess may define an imaging window within the target area. The imaging window may have an area of at least 16mm by 16mm. A thickness of the body between the front surface and rear surface in the imaging window may be between Imm and 1.25mm The device may comprise a sidewall extending out from the front surface in a direction away from the rear surface, the sidewall may define a volume within it and may be arranged to separate the eye lids of a user. This allows the eyelids of a user to be held open in a readily repeatable manner.

The sidewall may extend around the flat region of the front surface. This ensures the sidewall does not restrict the size of the imaging window.

The sidewall may abut the periphery of the flat region of the front surface.

The sidewall may be formed as a separate element to the body, and may be fixed to the body by adhesive. This allows the front surface to be polished before the device is assembled.

The body may comprise a step formed in the front surface to locate the sidewall.

The step may be formed at the interface between the curved edge portions of the front surface and the flat region.

The sidewall may have an inner surface facing into the volume he inner surface extending perpendicular to the flat region of the front surface. I5

The sidewall may have an outer surface facing out of the volume, the outer surface diverging from the inner surface, as the side wall extends away from the body.

The side all may extend round the full circumference of the flat region of the front 20 surface.

The body may be provided with an anti-fogging coating.

The device may comprise a removable disk arranged to be provided over the flat surface. The sidewall, where present, may locate the disk.

The removable disk may comprise markings or other indica arranged for one or more of the following: colour calibration of a sensor used in imaging the eye; focussing of a sensor used in imaging the eye; location of features of the eve in the frame of reference of the camera; identification of the device by a sensor used in imaging the eye.

The markings or indica may comprise: letters, shapes, patterns, logos or designs in one or more colours. Alternatively, the markings may comprise gridlincs or dashed gridlines.

The device may comprise a suction tool arranged to engage the device for insertion and/or removal of the device from an eye socket. The suction tool may be used for insertion and/or removal of the disk, where provided.

The body may be shaped and sized for use in any one of the following: a fully or partially enucleated or anophthalmic eve socket, wherein the rear surface engages an orbital implant provided in the eye socket; a microphthalmic eye socket, wherein the rear surface engages an eye of the user; a healthy eye socket, wherein the rear surface engages an eye of the user.

According to a second aspect of the invention, there is provided a set having a plurality of devices according to the first aspect, each device being of a different known size and/or configuration. I5

By having a set of device of standard sizes, the scanning technician or doctor may find a best fit for the patient Knowledge of the size used may feed into analysis of the images taken.

The device may comprise a first subset for fitting in a left eye socket and a second subset for fitting in a right eye socket.

According to a third aspect of the invention, there is provided a device for holding an eye open, the device comprising: a body arranged to be inserted into an eye socket, the body having: as rear surface configured to engage a surface of the eye socket; and an opposing front surface; and a sidewall extending out from the front surface, in a direction away from the rear surface, the sidewall defining a volume within it and arranged to separate the eye lids of a user.

This allows the eyelids of a user to be held open in a readily repeatable manner.

The device may comprise an aperture extending through the body, within the sidewall, to allow access to the eye socket of the user or patient. This may allow a doctor, surgeon or technician to access the eye whilst the eyelids arc held apart.

Alternatively, the body may be solid within the sidewall.

According to a fourth aspect of thc invention, there is provided a method of making a device as claimed in the third aspect, the method comprising making the body, polishing the body, and affixing thc sidewall to thc body.

This allows the body to be polished without the sidewall impinging on the body.

The body may be solid and have a flat forward facing surface within the sidewall. The method may include polishing the flat surface before affixing the sidewall.

The body may include a recess extending from the rear surface towards the front surface. The recess may havc a flat inner surfacc extending parallel to the flat region of the front surface. The method may include boring the recess out of the body, and then polishing the recess. Polishing the recess may include rounding the internal corners of the recess.

It will be appreciated that features discussed in relation to one aspect may be applied to any other aspect, unless mutually exclusive.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure I illustrates a device for holding the eyes of a patient open, in sectional side view; Figure 2 illustrates the device of Figure 1 in frontview: Figure 3 illustrates the device of Figure 1 in rear view.

Figures 4A and 48 illustrate examples of disks for use with the device of Figure 1; Figure 5 shows the central region of the device of Figure 1, in cut-through side view, with a disk of Figurc 4A or 4B fitted in place; Figure 6 illustrates a set devices; Figure 7 shows the device of Figure 1 with an anti-fogging coating; Figure 8 illustrates an alternative device for holding the eyes of a patient open, in sectional side view; and Figure 9 illustrates a method for making the device of Figure 1 or Figure 8.

Figures 1 to 3 schematically illustrate a device 1 suitable for holding the eyes of a patient open. Figure 1 shows the device 1 in sectional side view, Figure 2 shows a front view of the device 1, and Figure 3 shows the rear view of the device 1. Figures 2 and 3 include a dashed line through which the section of Figure 1 is taken.

The device is formed by a body 3. The body 3 has a convex front surface 5 (see Figure 2), and an opposing concave rear surface 7 (see Figure 3), in general, in the following description, "forward" will be considered to be along a direction from the rear surface 7 to the front surface 5, and "backward" in the opposite direction. A thickness of the body 3 extends from the front surface 5 to the rear surface 7. The thickness between the front and rear surfaces 17, 19 may vary across the area of the device 1.

In the current example, the device 1 is arranged for use in an anophthalmic eye socket of a user, having an orbital implant (not shown). The shape and size of the body 3 is arranged to sit in the space formed between an orbital implant and the eyelids of the user. In particular, the rear surface 7 of the body 3 is shaped to conform to the surface of the orbital implant, when covered by the conjunctiva of the eye socket.

A peripheral part of the body is formed by a curved edge portion 9. This has curved parabolic surfaces on the front surface 5 and rear surface 7, and is shaped to sit behind the eyelids of the patient.

In a central portion 11 of the front surface 5, the body 3 has a flat region 13. The flat region 13 is substantially circular when viewed front on, and defines a plane. In other words, the front surface may be considered as a continuous parabolic surface with a flattened region 13 formed away from the edge portion 9.

In use, the plane of the flat region 13 of the front surface 5 is generally parallel to an imaging plane used to image an eve socket of the patient wearing the device 1. In the example of a device for use in an anophthalmie socket, the flat region 13 is positioned to overlie the expected location of at least the iris and pupil of an eye in the eye socket. Therefore, the flat region 13 defines a target area for imaging.

At the periphery 15 of the flat region 13, an interface is formed between the flat region 13 and the curved parabolic edge portion 9. A step 17 is formed at this interface, the step 17 having a flat ledge 19 and a side 21. The ledge 19 extends parallel to the flat region 13, but spaced backwards from the flat region 13 towards the rear surface 7, and the side 21 extends perpendicular to the flat region 13, extending between the flat region 13 and the ledge 19.

An annular sidewall 23 is formed, extending forward from the body 3. The sidewall is located by the step 17 and extends forward past the flat region 13. A base 25 of the sidewall rests on the ledge 19 and a portion of an inner surface 27 of the sidewall 23 abuts the side 21 of the step.

The inner surface 27 of the sidewall 23 extends perpendicular to the flat region 13, such that a cylindrical volume 29 is defined inside the sidewall 23.

As the sidewall 23 extends forward from the front surface 5 of the body 3, the sidewall 23 gets thicker (measured in a radial direction from the centre of the sidewall 23). Thus the outer surface 31 of the sidewall 23 is inclined away from the volume 29. Thus the outer surface 31 of the sidewall 23 diverges from the inner surface 27 as the sidewall 23 extends forward.

As will be discussed below in more detail, the sidewall 23 is formed separately to the body 3, and joined to the body by an adhesive 33.

In the peripheral edge portions 9, the rear surface 5 also follows a parabolic curve. In the central portion 11, a recess 35 is formed in the rear surface 7, extending into the body 3 towards the front surface.

When viewed from the rear, the recess 35 is circular in shape. As best shown in Figure 1, the recess 35 is aligned with the flat region 13 of the front surface 5. The recess 35 is smaller than the flat region 13 on the front surface 5, such that when viewed from the front or rear, the recess 35 is formed entirely within the area bounded by the flat region 13.

The width of the recess 35, measured as a diameter parallel to the flat region 13 of the front surface 5, narrows as it extends into the body 3 from the rear surface 7 to the front surface 5, such that the sides 37 of the recess 35 are inclined inwards towards each other as the recess 35 extends forward from the rear surface 7 towards the front surface 5.

The recess 35 is a blind recess in that it has a closed end rather forming a base, rather than extending through the body 3. The base of the recess 35 is formed as a flat surface 39 extending parallel to the flat region 13 of the front surface 5.

In the area of the flat surface 39 of the recess 35_ the body 3 is between 1mm and 1.25mm thick. This ensures fewer artefacts, defects and effects in the image captured, and the flat surfaces 13, 39 also reduce reflections and other image artefacts.

As will be appreciated from Figure I. the thickness of the body 35, measured in a direction perpendicular to the rear surface 7 is at a minimum in the central portion 11, particularly in the recess 35 A number of through holes 41 are formed extending through the body 3 from the front surface 5 to the rear surface 7. The through-holes 41 are formed in the edge portion 9, away from the target imaging area.

In the above example, the body 3 is sized and shaped to fit into an anophthalmic eye socket of a patient. It will be appreciated that this may be by way of example only. In other examples, the body 3 may be sized and shaped to fit into an microphthalmic socket or a healthy eye socket. In the example of the anophthalmic socket, the device 1 engages with the orbital implant/conjunctiva surface in the eye socket. in the microphthalmic socket or healthy eye socket, the device 1 engages with the surface of the eye ball and the target area, bounded by the sidcwall 23, overlies the iris and pupil.

In use, an imaging technician, doctor or the patient themself places the device 1 into the eye socket. By holding the eyes of the patient open, an imaging window 43 (shown by dashed lines in Figures 2 and 3) is defined over which the image can be taken. The image is then captured and the device 1 removed and cleaned and sterilised for reuse.

The imaging window 43 is defined within the target area. The exact shape and size of the imaging window 43 is a result of the imaging technique used. The maximum possible size of the imaging window 43 is limited by the size of the flat inner surface 39 of the recess 35, since the flat inner surface 39 of the recess 35 in the rear surface 7 of the device 1 is smaller than the flat region 13 of the front surface 5. In Figures 3 and 4, the imaging window is shown as circular, and slightly within the boundary of the flat inner surface 39 of the recess 35, but this is by way of example only. The imaging window 43 may be any shape and size, within the boundary of the flat inner surface 39 of the recess 35. In one example, the total imaging window, and thus the size of the image acquired, may be 16=2 The image acquired provides an image of an area of the eye socket covered by the imaging window 43 The image is unobstructed by, for example the eye lids of the I5 patient.

Various types of image may be captured using the device. For example, the image may capture a three dimensional image of the external and/or internal structure of the eye socket. This may be, for example, Optical Coherence Tomography (OCT). In other examples, the image captured may be a two dimensional image of the front surface of the eye socket (either the conjunctiva or the eyeball). Multiple types of image may be taken at the same time.

In some examples, the technician or doctor makes a mark on the front surface 5 to indicate the position of the pupil of the patient. This may be, for example, using a pen or marker. The mark provides a reference point to ensure the image can be aligned in an extern& reference frame, and also provides a focal point. The mark is removed by the cleaning process discussed above.

Where a three dimensional image is captured, the flat region 13 provides a three dimensional reference point for scaling and determining the structure captured in the image, by knowing the size and shape of the device I Optionally, the device 1 may be provided with one or more removable disks 45. Two examples of removable disks are shown in Figures 4A and 4B As shown in Figure 5, which shows a cut-through side view of the central portion 11 of the device 1, the disks 45a, 45b are sized and shaped to fit within the annular sidewall 23, at the flat region 13 of the front surface 23.

The disks 45a, 45b are provided with markings, text or other indica. This may be provided for a variety of uses. For example, gridlines 47 may be provided on the disk 45a to aid alignment of the image to a frame of reference defined by the device 1.

In other examples, areas of different colour 49 may be defined to allow for colour calibration of a device, or text or other markings 51 may be provided to allow identification of the device I being used.

In use, a suction tool 53 is provided having a suction cup 55 at one end and a handle 57. This can be used to insert and remove the disk 45 whilst the device I is fitted in a patient. The removable disk 45 may be inserted, used and removed before image capture. Alternatively, the removable disk may be kept in place during image capture. In yet a further example, the removable disk 45 may only be inserted, used and removed after image capture.

In some examples, the suction tool 53 may also be used for fitting and removal of the device I. As shown in Figure 6, a technician or doctor may be provided with a set 59 of devices la-x as discussed above. Each of the devices la-x may be of the same general configuration, but have slightly different shape and size, to fit into different shape and size eye sockets.

The range of shapes and sizes is chosen based on statistical analysis of a sample of eye sockcts. Thus the technician or doctor may select the best fit for the particular patient, thus improving comfort, and also the fit, which in turn may improve image quality compared to a poorly fitting device I a-x It will be appreciated that in the set 59 of devices shown in Figure 6, the sidewall 23 may the same shape and size for each device 1, and only the body 3 changes alternatively, both the body 3 and sidewall 23 may change.

In Figure 6, the set 59 includes twenty four devices la-x. However, this is by way of example only, and the set 59 may include any number of devices la-x. For example, the set may include 10, 12, 16, 24 or any number of devices la-x.

In some examples, the set 59 may include a first subset 59a for use in left eye sockets, and a second set 59b for use in to right eye sockets. It may be that each device la-1 in the first subset 59a is a mirror image of a device lm-w in the second subset 59b, although this is not always the case When analysing the three dimensional shape (internal or external) of an eye socket, knowledge of the device la-x used for a patient, and the exact size and shape of the device la-x can be of help. For example, knowledge of the size and shape of the device la-x selected may provide a reference or basis for automated analysis, and other processing. For this reason identification of the device la-x used, as discussed above can be helpful. Alternatively, the technician may simply record the device la-x used.

In the above example, through holes 41 are provided in the body 3, away from the central region 11. The through-holes prevent fogging of the device, and especially the imaging target area as the device is worn by the patient.

In addition to or instead of the through holes 41, the device may be provided with an anti-fogging coating 61. As shown in Figure 7, the anti-fogging coating 61 may be provided on the body 3 only, on the front 5 and rear 7 surfaces. Alternatively, the anti-fogging coating 61 may be provided on the whole device 1. In yet a further example, the anti-fogging coating 61 may be provided on the body 3 and/or sidewall 23 only in the central region 11. The antifogging coating 61 may be provided on the front surface 5 and/or rear surface 7.

Any suitable anti-fogging coating 61 that is transparent to the imaging technique being used may be applied. For example, the anti-fogging coating may be polyvinyl alcohol, colloidal silica and porous organosilicate micelles, or Poly(ethylene-maleic anhydride) (PUMA) and Poly(vinyl alcohol) (PVA).

In the examples discussed above, the body 3 of the device 1 is continuous in the central region 11. This is suitable for when the device 1 is used for various imaging techniques. In other examples, where the device is used for other imaging techniques, or to aid a doctor or technician access to the eye socket, for example for surgery, the device I may include an aperture 63 extending through the body 3 in the central region 11. This may be within the sidewall 23, and thus may correspond to the imaging window in the examples discussed above. An example of such a device 1 is shown in Figure 8.

Figure 9 schematically illustrates a method 100 for making a device 1 as discussed above.

In a first step 102, the body 3 is made. The body 3 may be made by any suitable technique. For example, the body 3 may be made by three dimensional printing, moulding, extrusion, casting and the like. The body 3 may be made to substantially the correct shape, or may be made to an approximate shape which is then processed to get the final shape, In one example, for example with three dimensional printing, the body may be made with the flat region 13, recess 35 and through-holes 41 already formed. In other examples, the step 102 of making the body 3 may include optional sub-steps including an optional sub-step 102a of flattening the front surface 5 in the central region 11 after the device 1 is made with a curved front surface 5. A further optional subset 102b may be drilling or boring the recess 35 in the rear surface 7. A process such as tubbing may also be used. A third option& sub-step 102c may be drilling or otherwise forming the through-holes 41.

In examples having an aperture 63 in the central region 11 of the body 3, making the body 3 may also include drilling the aperture 63. Alternatively, the aperture 63 may be already formed in the body 3.

In a second step 104 of the method 100, the body 3 is polished. in particular, the flat region 13 on the front surface 5 may be polished in a first sub-step 104a, and the recess 35 may be polished in a second sub-step 104b. Polishing the recess 35 may include ensuring proper rounding of the corners in the recess 35.

In a third step 106, the sidewall 23 is made. The sidewall 23 can be made using similar methods as the body 3.

The sidewall 23 is then fixed to the body 3 by an adhesive 33 at a fourth step 108.

Any suitable adhesive may be used. The adhesive can be cured as required.

Any suitable transparent biocompatible material may be used for the body 3 and sidewall 23. The body 3 (and any coating) should be transparent to at least the radiation used in any scanning or imaging method used. For example, the device 1 may be made from poly(methyl methacrylate) (PMMA). Alternatively, other acrylic materials could be used. For example, VEROCLEARTM, supplied by Stratasyst could be used, or MED 610.

VERO is an acrylic compound comprising a mixture of components including (but not limited to) an acrylic monomer; isobornyl acrylate; pheno,4,4'-(1-methylethylidene)bis-, polymer with (chloromethyDoxirane,2-propenate; dipheny1-2,4,6-trimethylbenzoyl phosphine oxide; titanium dioxide, acrylate acid ester; propylene glycol monomethyl ether acetate and phosphoric acid.

MED 610 is a mixture of components including (but not limited to) Exo-1,7,7-trimethylbicyclo[2.2.1]hcpt-2-y1 acrylate; tricyclodecane dimethanl diacrylate; bisphenol A epoxy acrylate oligomer; and 2,4,6-trimethylbenoyldiphenylphosphine oxide.

The body 3 and sidewall 23 may be the same or different materials.

The flat region 13 on the front surface 5 is polished before the sidewall 23 is fixed to the body 3. Otherwise, the steps discussed above may be conducted in any suitable order.

In the examples discussed above, the sidewall 23 is continuous around the flat region 13 on the front surface. This may not be the ease. In some examples, the sidewall 23 may be non-continuous around the flat region 13. For example, it may only extend on the top and bottom, so it holds the eyelids up. In other examples, the sidewall 23 may even only act on one eyelid (either the upper or lower).

In the examples discussed above, the sidewall 23 is circular when viewed front on.

This is by way of example only, and the sidewall may have any suitable 23 shape.

In some examples, where the imaging does not requ re a large imaging area, such that the eyelids do not need to be held open, the sidewall 23 may be omitted altogether.

The removable disk 45 is entirely optional. In some embodiments, the function provided by the disk (e.g. the markings, gridline and the like) may be provided on the device 1, for example on the flat surface 13 or the sidewall 23. In other examples, this function may not be required and may be omitted altogether.

In the example discussed above, the sidewall 23 is formed at the edge of the flat region, but this need not be the case. The sidewall, and the step or other feature for locating the sidewall may be located in the flat surface 13, or in the curved portion 9 of the body 3.

The use of the to& 53 for fitting/removing the disk 45 and/or device is entirely optional. Alternatively, any suitable type of tool, either based on a suction cup 55, or on other means, may be used.

Claims

CLAIMSA device for aiding imaging of an eye and/or eye socket, the device comprising: a body arranged to be inserted into the eye socket, the body having: a curved peripheral edge portion; a rear surface forming part of the curved peripheral edge portion and configured to engage a surface of the eye socket; and a front surface forming part of the curved peripheral edge portion and having a flat region located away from the curved peripheral edge portion, the flat region at least partially defining a target area for scanning, wherein the body includes one or more through-holes extending through the body, the through-holes located away from the target area. I5
The device as claimed in claim 1, wherein a thickness of the body in the flat region is less than a thickness of the body in the part of the curved peripheral edge portion surrounding the flat region.
3, The device as claimed in claim I or claim 2, wherein the body comprises a recess extending from the rear surface towards the front surface, aligned with the flat region.
The device as claimed in claim 3, wherein the recess narrows towards the front surface, measured in a direction parallel to the flat region on the front surface.
The device as claimed in claim 3 or claim 4, wherein the recess has a flat inner surface extending parallel to the flat region of the front surface.
6. The device as claimed in claim 5, wherein, when viewed perpendicular to the flat region of the front surface, the flat region of the front surface overlaps the flat inner surface of the recess in all directions.The device of claim 5 or claim 6, wherein the flat inner surface of the recess defines an imaging window within the target area.The device of any claim 6 or claim 7, wherein a thickness of the body between the front surface and rear surface in the imaging window is between lmm and I.25mm The device as claimed in any preceding claim comprising a sidewall extending out from the front surface in a direction away from the rear surface, the sidewall defining a volume within it and arranged to separate the eye lids of a user.10. The device of claim 9, wherein the sidewall extends around the flat region of the front surface.11. The device of claim 10, wherein the sidewall abuts the periphery of the flat region of the front surface.12. The device of any of claims 9 to IL wherein the sidewall is formed as a separate element to the body, and fixed to the body by adhesive.13. The device of claim 12, wherein the body comprises a step formed in the front surface to locate the sidewall.14. The de ice of any of claims 9 to 13, wherein the sidewall has an inner surface facing into the volume, the inner surface extending perpendicular to the flat region of the front surface.15. The device of any of claims 9 to 14, wherein the sidewall has an outer surface facing out of the volume, the outer surface diverging from the inner surface, as the side wall extends away from the body.16. The device of any preceding claim wherein the body is provided with an anti-fogging coating. 17. 18. 19. I5 20. 21. 22. 23.The device of any preceding claim, comprising a removable disk arranged to be provided over the flat surface within the sidewall.The device of claim 17, wherein the removable disk comprises markings or other indica arranged for one or more of the following: - colour calibration of a sensor used in imaging the eve; - focussing of a sensor used in imaging the eye; - location of features of the eye in the frame of reference of the camera -identification of the device by a sensor used in imaging the eye.The device of any preceding claim, further comprising a suction tool arranged to engage the device for insertion and/or removal of the device from an eye socket and/or when dependent on claim 17 or 18, for insertion and removal of the removable disk.The device of any preceding claim wherein the body is shaped and sized for use in any one of the following: -a fully or partially enucleated or anophthalmic eye socket, wherein the rear surface engages an orbital implant provided in the eye socket; - a microphthalmic eye socket, wherein the rear surface engages an eye of the user; - a healthy eye socket, wherein the rear surface engages an eye of the user.A set haying a plurality of devices as claimed in any preceding claim, each device being of a different known size and/or configuration.The set having a plurality of devices as claimed in claim 21, comprising a first subset for fitting in a left eye socket and a second subset for fitting in a right eye socket.A device for holding an eye open, the device comprising: a body arranged to be inserted into an eye socket, the body having: a rear surface configured to engage a surface of the eye socket; and an opposing front surface; and a sidewall extending out from the front surface, in a direction away from the rear surface, the sidewall defining a volume within it and arranged to separate the eye lids of a user.24. A device as claimed in claim 23, comprising an aperture extending through the body, within the sidewall, to allow access to the eye socket of the user.25. A device as claimed in claim 23 or claim 24, having the features of any one of claims 10 to 16 or claim 20.