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 Table of Contents  
INNOVATION
Year : 2019  |  Volume : 31  |  Issue : 1  |  Page : 64-71

How-to guide for smartphone slit-lamp imaging


1 Department of Glaucoma, Westend Eye Hospital; Department of Ophthalmology, Little Flower Hospital and Research Centre, Cochin, Kerala, India
2 Department of Ophthalmology, Jubilee Mission Medical College, Thrissur, Kerala, India

Date of Web Publication15-Apr-2019

Correspondence Address:
John Davis Akkara
Department of Glaucoma, Westend Eye Hospital, Kacheripady, Cochin - 682 018, Kerala
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/kjo.kjo_24_19

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  Abstract 

Ophthalmology is a very visual science; therefore, visualizing the eye and its pathology in good clarity is essential for a diagnosis. Over the past several years, smartphones have evolved to replace several gadgets in our daily life, including cameras. In ophthalmology, they have been very useful to take good quality photographs through slit lamp, gross photographs and also fundus photos using low-cost smartphone fundus cameras. In this article, we elaborate on the techniques, tips, and tricks to obtain excellent smartphone ophthalmic photographs and videos with a mid-level smartphone camera. We teach how to take diffuse and slit photographs, with and without an adapter, in addition, how to take Gonioscopy, specular microscopy, and fundus via 90D. These photos and videos can also be edited on the smartphone itself and used for case discussion, second opinion, teaching, presentations, and publications.

Keywords: Fundus photo, fundus video, imaging apps, slitlamp photo, smartphone


How to cite this article:
Akkara JD, Kuriakose A. How-to guide for smartphone slit-lamp imaging. Kerala J Ophthalmol 2019;31:64-71

How to cite this URL:
Akkara JD, Kuriakose A. How-to guide for smartphone slit-lamp imaging. Kerala J Ophthalmol [serial online] 2019 [cited 2019 Jun 26];31:64-71. Available from: http://www.kjophthal.com/text.asp?2019/31/1/64/256265


  Introduction Top


Over the past several years, smartphones have evolved into pocket computers that replace several of the bulky gadgets we used to use. They have replaced the phone, phone book, camera, camcorder, calculator, alarm clock, torches, watch, music player, radio, eBook reader, voice recorder, GPS, leveler, scanner, compass, gaming device, book, calendar, notepad, newspaper, internet browsing device, light meter, guitar tuner, and so on. In ophthalmology, they can replace eye testing charts for visual acuity, contrast sensitivity, color vision, optokinetic nystagmus drum, Worth 4 dot test, stereopsis testing, amblyopia therapy, several calculators, and more.[1]

Conventional slit-lamp photography and fundus photography devices are large and expensive. The rapid advancement in technology allowing miniaturization of cameras and computers have not led to smaller and cheaper imaging devices from the ophthalmic industry yet. Innovators have used smartphones to create things like a new fundus camera using a portable slit lamp.[2]

Nowadays, every Tom, Dick, and Harry has a smartphone capable of running all ophthalmic apps, with a camera that can take good quality ophthalmic photographs. There are also adapters you can make like the DIYretCam,[3] to use your smartphone for fundus photography. Smartphones have definite potential in ophthalmic imaging [Figure 1], especially in primary care settings.[4] Going further ahead, artificial intelligence algorithms can now run on smartphones to do things like detecting optic nerve head in smartphone captured fundus photographs.[5] The Remidio “Fundus on phone,” a smartphone-based device, can use artificial intelligence for grading of diabetic retinopathy on a smartphone.[6] These algorithms can run on a smartphone itself, unlike earlier, when the images were sent via Internet to a high performance sever computer for processing.
Figure 1: Correct positioning of smartphone with adapter on slitlamp. Note the gap of 1–2 cm between the camera lens and the eyepiece

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In this article, we will give tips and tricks to use your mid-range smartphone to take external, slit lamp, fundus, gonioscopy, specular, and other ophthalmic photographs.

To get started, obtain informed consent from the patient. In several hospitals, the documentation is incorporated into the patient case sheet at the time of registration. The patient identifying information should be removed from the photographs.

Make sure your smartphone camera application is set to the highest resolution and all filters such as “beauty mode” and “portrait mode” are turned off. High dynamic range (HDR) is available in some smartphones, and this should be turned off as it can cause motion blur artifacts. Flash is to be turned off for slit-lamp photographs, turned on for fundus photographs, and depends on the situation for external photographs. Focus and exposure can be set to “touch to focus” mode. Camera settings are to be set to maximum resolution for both photos and videos.

Most modern smartphone camera inbuilt apps are adequate for smartphone ophthalmic photography, but if required, one can use Camera FV-5[7] or open camera[8] or Slit Lamp Pro – Ophthalmic CAM (previously on Play Store, now removed) apps for android or Camera Plus Pro[9] for Apple iOS.

All the photographs in this article are original images by the author and have been taken using a mid-range Android smartphone (OnePlus 3T) on various slit lamps, but should work on any mid-range smartphone.


  Direct External Photography Top


For a patient with an ocular adnexal mass, laceration, ecchymosis, ptosis, strabismus, large ocular injuries, or any other large finding, a direct photograph of the external eye and adnexa is required. If a slit lamp is not readily available, then a direct smartphone photograph would be useful for ocular findings also.

The background illumination, illumination of the participant, and shadows are of utmost importance. The background should preferably be a white, gray or blue, uniform, nonreflecting surface There should be uniform illumination in the background, without any bright lights or bright areas. The participant should be illuminated well, from >1 diffuse light source with no areas of glare or reflections. Another smartphone in Torch/Flashlight mode can be used for this additional lighting if room lighting is not adequate. Turn off the HDR, portrait mode, and other filters. Flash can also be turned on for gross photographs depending on the available lighting and shadows. The participant should hold still while the photograph is taken, and the smartphone should not move either. Autofocus requires good illumination even before the flash is on, and hence, use external illumination (from another smartphone torch perhaps). Autofocus may not always focus on the area of interest, and hence use touch-to-focus to ensure sharp focus. Use long-press to lock focus and exposure and then adjust the exposure gradually until the area of interest is perfectly exposed. Avoid digital zoom and use optical zoom whenever possible [Figure 2].
Figure 2: Direct smartphone photograph of eye showing conjunctival ulcer. Camera focus was made on the eye by keeping smartphone further away, using illumination and touch-to-focus

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Directly taking photographs of ocular structures with the smartphone held close often gives photos which are out of focus. The near point of most smartphone camera's range of focus is 7–10 cm and hence one has to move the smartphone further back and use digital zoom to clear focused photographs. The better option is to use a clip-on macro lens, which acts as an optical zoom.[10]


  Barehanded Smartphone Slitlamp Photography Top


Slit-lamp photography gives much better and detailed photographs than external photographs, and hence use slit lamp whenever possible. Smartphone slit-lamp photography does not require adapters for quick photographs or videos, just steady hands.

First, ensure that the patient is comfortably seated, has given informed consent and is explained the procedure. Start with moderate diffuse illumination and least magnification. Before using the smartphone, look through the eyepiece and bring the desired area of interest into focus. Next, take your smartphone in your left hand with the camera on the left, rest your left-hand fingers on the left eyepiece, and slowly move the smartphone toward the eyepiece until the camera lens is around 1–2 cm from the eyepiece. The view through the slit lamp should be visible as a circle of light, which you need to adjust by moving the camera position in all three axes until you get a sharp bordered circle. Next, hold steady and increase slit-lamp magnification to the desired level. At each step of magnification, the depth of focus reduces, and the image may go out of focus, to use the right hand on the slit-lamp joystick to refocus. Then, use pinch-zoom to zoom to your desired area of interest, touch-to-focus and long-press for focus and exposure lock if necessary. Adjust the exposure and then click the photograph.

Diffuse illumination is easier to photograph than slit illumination and hence practice with diffuse illumination first.


  Slit-Lamp Photography With Adapters Top


Low-cost smartphone slit-lamp adapters are available to buy online in India (https://amzn.to/2T6TLPs),[13] and they make it easier to do smartphone slit lamp and even surgical photography and video recording through the eyepiece of microscopes. I use these when recording slit-lamp videos, especially fundus and Gonioscopy. It is also useful for specular photographs and other photographs which need precision and manipulation.

They consist of two parts – one part holds the smartphone securely from the sides, whereas the other part fixes onto the eyepiece of the slit lamp. There are different models for each part where some work better than others. I prefer the spring action type of smartphone holder with the hexagon model of eyepiece holder.

When fixing the smartphone on the holder, make sure the power and volume buttons are not accidentally pressed by the sides of the adapter. If the power button is difficult to access with the smartphone in the adapter, make sure you have turned on the camera shortcut gesture in your settings. When fixing, the adapter to the eyepiece, leave a gap of 1–2 cm between the eyepiece lens and the camera lens. Some slit-lamp eyepieces have an extra plastic ring around the eyepiece which helps to leave this gap. Once the lenses are grossly centered, activate the camera and do fine adjustment to get a sharp circle of view through the eyepiece [Figure 1].

For dual camera smartphones, figure out which lens is the main lens at what zoom level and center it accordingly. Using an app like Camera FV5 or open camera can help to restrict to a single lens to avoid confusion while centering and taking slitlamp photographs. To switch between the dual cameras in some dual lens smartphones like the OnePlus 5T, put this code in your dialer *#*#1597#*#*. This should open camera in debug mode and allows switching to a single lens mode.

Once fitted and centered, you can take smartphone slit-lamp photos and videos, including 90D/78D/66D fundus, specular endothelial photos, and Gonioscopy.


  Slit-Lamp Photography – Diffuse Illumination Top


Diffuse illumination photographs and videos are the easiest to take. Keep the illumination at an angle, and hence that the reflected glare from the cornea is minimal. The auto-exposure adjustment usually adjusts exposure adequately, if not, use touch-to-focus. Long-press to focus and exposure lock on the area of interest and then increase or reduce the exposure by rotating or sliding around the focus-locked area [Figure 3], [Figure 4], [Figure 5].
Figure 3: Epicapsular stars on anterior lens capsule using smartphone on slit lamp with adapter. Illumination is from left, causing corneal glare and overexposed photo in that area

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Figure 4: Corneal abrasion by small-glass piece. Note that focus is on the cornea, and iris is out of focus. At higher magnification, the depth of focus reduces causing this “portrait effect.” At lower optical magnification (Even with higher digital zoom on smartphone), cornea and iris may have been in focus simultaneously

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Figure 5: Dendritic ulcer stained with fluorescein and viewed under cobalt blue light. The exposure on the smartphone camera has to be reduced to see the stained lesion clearly

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  Slitlamp Photography – Slit Illumination Top


Slit illumination requires extra diffuse illumination to get better pictures. The room illumination adds reflections in the unilluminated cornea in slit photographs. First, focus the area of interest in slightly wider illumination and then slowly reduce to a slit beam. Avoid the area of maximum reflection by changing the angle of the illumination arm (and viewing arm also if necessary). If required, add extra diffuse external illumination onto the cornea using another smartphone in Flashlight/Torch mode. Some slit lamps have a flexible extra diffuse illumination made for this purpose [Figure 6], [Figure 7], [Figure 8], [Figure 9].
Figure 6: Iris bombe seen in slit image. Cornea is edematous. Focus and exposure have been locked on the anterior capsule, so parts of the corneal slit and iris are overexposed

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Figure 7: Descemet's tear (Haab's striae) seen on parallelepiped wide slit. Note that, focus is on cornea, with iris out of focus. The illumination is moved such that corneal reflection and glare is out of the picture

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Figure 8: Pigmented keratic precipitates seen on wide slit. Note that, focus is on cornea with iris out of focus. Furthermore, note that the fine keratic precipitates are better visible against the background of the dilated pupil than against the iris

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Figure 9: Slit image taken for anterior chamber depth evaluation by the Van Herick technique. Notice the reflection of eyelashes, slitlamp, and ophthalmologist on the cornea. This can be avoided by using extra diffuse illumination or Dr. Mukesh Dholakia's Partial Diffuser

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Another technique for the diffuse illumination is to make and use Dr Mukesh Dholakia's partial diffuser, which is a piece of translucent plastic of the size of the slit lamps's reflecting mirror with a slit cut in the center. This is to be placed on the mirror of the illumination arm and it gives the slit as well as a diffuse light at the same time to give excellent slit images without the hassle of extra illumination.


  Retroillumination Top


Change the position of the illumination arm to coaxial; making sure the view through neither eyepiece is obstructed. Keep a slit size small enough to fit in the pupil. When doing retroillumination, note that one eyepiece gets the best view at a time, and hence choose that eyepiece to place the smartphone. This can be used to photograph peripheral iridotomies, iridodialysis, posterior subcapsular cataract, posterior capsule opacification, pigments on endothelium, corneal epithelial edema and so on [Figure 10], [Figure 11], [Figure 12].
Figure 10: Retroillumination showing multifocal intraocular lens in bag. The overexposed reflections from the capsule could have been avoided by making a smaller slit

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Figure 11: Retroillumination showing Elschnig's Pearls in Posterior Capsule Opacification. The focus and exposure has to be adjusted to the posterior capsule to get clear images

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Figure 12: Subluxated intraocular lens in a patient with Posterior Capsule Rent. The folds in the PC have been clearly focused

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  Fundus Photography (90d/78d/66d) Top


First make sure to clean the lenses with a lint-free cloth, as any glare from the lens affects your fundus photo to a great extent. Use the smartphone adapter, as it leaves your hand-free to hold the 90D or other lenses. I prefer to take a video and later extract photographs from it if required. Undilated fundus photography is possible and useful if you need to just take a quick photograph of the disk. However, it is much easier to take the dilated fundus photograph. Use a slit of light to view the fundus through the 90D lens, then touch-to-focus on the view of the fundus to force to the camera to focus on the retina and not the reflections from the lenses. Use long-press to focus-lock, and then adjust the exposure. You can also use manual focus if the smartphone tends to get confused by the glare from the lens. Once in focus, the illumination can even be tilted slightly and widened to get a much larger view of the fundus in internally reflected illumination. Studies have shown that the cup-disc ratio measured from smartphone fundus photographs show good agreement and this would be even better with a slit-lamp-based fundus photo [Figure 13] and [Figure 14].[14]
Figure 13: Fundus photo taken through 90D on slitlamp showing chorioretinal coloboma

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Figure 14: Fundus photo taken through 90D on slitlamp showing a venous loop (blue circle) in a patient with diabetic retinopathy

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  Specular Photographs of Corneal Endothelium Top


Photographing corneal endothelium is difficult but definitely possible with a smartphone. Use the slitlamp adapter. Keep the illumination and viewing arm at equal, approximately 60-degree angles from the center. Make a 1-mm slit so that the corneal layers are seen clearly in a parallelopiped. In this case, you need to focus on the point of maximum reflection from the cornea. Use long-press to obtain a focus lock. Then adjust the exposure way down, till you can see what is under the glare. Once focused on that point, increase the magnification on the slit lamp step by step, making sure to keep the endothelial layer in focus. Take photos of the endothelium at the highest magnification. You will need to crop and adjust the exposure, shadows and highlights of the image to make the endothelial cells clearly visible [Figure 15].
Figure 15: Specular photograph of corneal endothelium. Note the out-of-focus iris and focused endothelium at high magnification and zoom. The glare from epithelium is cropped out

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  Gonioscopy Top


Gonioscopy is also done with the smartphone fixed in the slit-lamp adapter. It is easier to take videos and then find the best frames from it later, but taking photo gives you the best possible image resolution. Follow the same principles as mentioned in slit-lamp fundus photography. Reduce the height of the slit, touch-to-focus and focus-lock to avoid the reflection from the gonioprism. I routinely use the Goldmann 2-mirror, 4-mirror or Volk G-2 for Gonioscopy photographs and videos [Figure 16] and [Figure 17].
Figure 16: Gonioscopy view through inferior mirror of Goldmann 2 mirror gonioprism showing large surgical PI through which ciliary processes are visible (red oval) and corresponding ostium (blue arrow)

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Figure 17: Gonioscopy showing an open angle. Note the Sampaolesi Line (pigmented Schwalbe's line)

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  3D Photography Top


Where feasible, stereo three-dimensional (3D) smartphone photos can be taken. The author has released a free Android app (iDoctor JD) on Google Play Store which has several 3D ophthalmic photographs, some of which were taken using this method.[11] These photographs can be viewed using low-cost Red-Blue Anaglyph glasses [Figure 18] and [Figure 19].[12] Inverse panorama or object panorama is another method of documenting gross findings that gives a lot of valuable 3D information.
Figure 18: Red-Blue three-dimensional anaglyph photo of shallow anterior chamber due to traumatic subluxation of lens. Note the PI done in the superotemporal area. (to be seen with Red-Blue three-dimensional glasses)

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Figure 19: Red-Blue three-dimensional anaglyph photo of corneal metallic rusted foreign body. Note the depth perception in addition to the iris being out-of-focus (to be seen with Red-Blue three-dimensional glasses)

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  Conclusion Top


Smartphones have rapidly driven low-cost innovation in health care.[15] They have made slit-lamp, fundus, gonioscopy, and even specular photography affordable to all ophthalmologists who have access to a slitlamp. Studies have shown fair to good reproducibility or slit-lamp images from conventional slitlamp cameras versus smartphone imaging.[16] Most medium-range smartphones are capable of excellent photographs and these are often good enough for publication and conference presentation. I hope that this guide allows especially the postgraduate students and private practitioners to document important clinical findings, show the findings to the patient, request an expert opinion, present in conferences, and publish in journals. This will definitely advance the field of ophthalmology at a rapid pace and allow us to make a difference.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patients have given their consent for their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Acknowledgments

The authors would like to acknowledge the support of JIPMER and Aravind Eye Hospital - Pondicherry, and Little Flower Hospital - Angamaly.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Akkara J, Kuriakose A. Innovative smartphone apps for ophthalmologists. Kerala J Ophthalmol 2018;30:138-44.  Back to cited text no. 1
  [Full text]  
2.
Arima M, Majima T, Tsukamoto S, Hara T, Wada I, Nakao S, et al. The utility of a new fundus camera using a portable slit lamp combined with a smartphone. Acta Ophthalmol (Copenh) 2019; doi: 10.1111/aos.14049.  Back to cited text no. 2
    
3.
Raju B, Raju NS, Akkara JD, Pathengay A. Do it yourself smartphone fundus camera – DIYretCAM. Indian J Ophthalmol 2016;64:663-7.  Back to cited text no. 3
[PUBMED]  [Full text]  
4.
Bifolck E, Fink A, Pedersen D, Gregory T. Smartphone imaging for the ophthalmic examination in primary care. JAAPA 2018;31:34-8.  Back to cited text no. 4
    
5.
Elloumi Y, Akil M, Kehtarnavaz N. A mobile computer aided system for optic nerve head detection. Comput Methods Programs Biomed 2018;162:139-48.  Back to cited text no. 5
    
6.
Rajalakshmi R, Subashini R, Anjana RM, Mohan V. Automated diabetic retinopathy detection in smartphone-based fundus photography using artificial intelligence. Eye (Lond) 2018;32:1138-44.  Back to cited text no. 6
    
7.
Camera FV-5 Lite – Apps on Google Play. Available from: https://www.play.google.com/store/apps/details?id=com.flavionet.android.camera.lite&hl=en. [Last accessed on 2019 Feb 28].  Back to cited text no. 7
    
8.
Open Camera – Apps on Google Play. Available from: https://www.play.google.com/store/apps/details?id=net.sourceforge.opencamera&hl=en. [Last accessed on 2019 Feb 28].  Back to cited text no. 8
    
9.
Camera Plus Pro. App Store. Available from: https://www.itunes.apple.com/in/app/camera-plus-pro/id345752934?mt=8. [Last accessed on 2019 Feb 28].  Back to cited text no. 9
    
10.
SmartPhone Camera Lens Macro Lens. Available from: https://www.amzn.to/2BWZzQP. [Last accessed on 2019 Feb 28].  Back to cited text no. 10
    
11.
iDoctor JD – Apps on Google Play. Available from: https://www.play.google.com/store/apps/details?id=com.fundazone.medical&hl=en. [Last accessed on 2019 Mar 02].  Back to cited text no. 11
    
12.
Red and Blue 3D Anaglyph Glasses. Available from: https://www.amzn.to/2VqAm8A. [Last accessed on 2019 Mar 02].  Back to cited text no. 12
    
13.
Smartphone Slitlamp Adapter. Available from: https://www.amzn.to/2T6TLPs. [Last accessed on 2019 Feb 28].  Back to cited text no. 13
    
14.
Russo A, Mapham W, Turano R, Costagliola C, Morescalchi F, Scaroni N, et al. Comparison of smartphone ophthalmoscopy with slit-lamp biomicroscopy for grading vertical cup-to-disc ratio. J Glaucoma 2016;25:e777-81.  Back to cited text no. 14
    
15.
Akkara JD. Commentary: Dawn of smartphones in frugal ophthalmic innovation. Indian J Ophthalmol 2018;66:1619.  Back to cited text no. 15
[PUBMED]  [Full text]  
16.
Chen DZ, Tan CW. Smartphone imaging in ophthalmology: A comparison with traditional methods on the reproducibility and usability for anterior segment imaging. Ann Acad Med Singapore 2016;45:6-11.  Back to cited text no. 16
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14], [Figure 15], [Figure 16], [Figure 17], [Figure 18], [Figure 19]



 

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  In this article
Abstract
Introduction
Direct External ...
Barehanded Smart...
Slit-Lamp Photog...
Slit-Lamp Photog...
Slitlamp Photogr...
Retroillumination
Fundus Photograp...
Specular Photogr...
Gonioscopy
3D Photography
Conclusion
References
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