How to build your own slit lamp camera system

I recently built a slit lamp camera using parts I had lying around and thought I'd share the experience.  The entire system can be built from scratch for about $3500-$4000. The system should pay for itself, so all ECPs should consider these systems "low cost".  A list of supported diagnoses and findings is listed at the end of the article.

The first thing you need to do is find out your model of slit lamp.  My slit lamp is from Woodlyn, but apparently Woodlyn follows Zeiss engineering.  A quick call to TTI Medical confirmed this.  After you do this, you will need these components:

1. Beam splitter ($999)
2. DSLR adapter ($1495)
3. Foot pedal for remote shutter ($85) from TTI Medical, no link - call and order
4. Canon Rebel XSi (~$650 - body only needed, or with more work get it down to $550 or less* - see "Tip" below) 
   1. note: this may have changed by the time you read this as the Rebel Ti is now coming out
   2. make sure you do not buy refurbished as you'll need the software that comes in the retail box
5. AC Adapter for Rebel ($65)
6. 22" or larger LCD screen ($150) (preferably with built-in speakers so you can use the computer/screen as a patient education system when you are not in the room - more on that later)
7. Wall Mount for LCD ($5)
8. Old computer and wireless mouse (hopefully free, does not need to be anything special, but USB 2.0 would be nice)
9. Software: $0
   1. the software that comes with the Canon Rebel XSi is more than enough for the job

Total Cost: between $3500-$4000

Why not go and buy a $4000 ready-made system?

1. With this system you get to take off the Rebel and use it for personal use.  It's a semi-pro-quality camera.
2. The Rebel XSi has a much higher quality CCD than any of the all-in-ones.
3. You can upgrade camera if needed down the road.

Building the System

TTI Medical's adapters come with great instructions, so I won't go into detail too much.  You will insert the adapters onto your slit lamp which takes about 10 minutes.  Put the Rebel onto the adapter and secure it.  The top of the camera will face left as you are sitting own if you have the left mount.  Attach the AC adapter, USB cord, and Foot stomp pedal.  You will use the "M" or manual mode.

Install the Canon software - all of it into your computer.  Once you turn on Camera (and it's hooked up via USB) the Windows quick start will popup - tell it to use EOS Utility and click the "every time" checkbox.  Now when you turn the Rebel on, the Canon Utility will pup up automatically. 

After you turn on Rebel, you will click "Set" on the Camera.  This will put the camera into "Live View" mode which means you can see on the LCD what is coming through the slit lamp.  To actually see this though, you will have to click the "Remote Live View Shooting" button which is the 3rd button at the bottom of this small EOS Utility window.  Note: if you click this button before pressing "Set" on camera, you will be able to use Live View, but the foot pedal will not work.  It took me a day to figure out that you have to set the camera in Live View mode by pressing "Set" FIRST, and THEN click the on-screen 'Remote Live View shooting" button in order to use Live View and the foot pedal at same time!

Pearls:

• On the ACCU adapter, there is an iris.  You want it about 3/4 "open" or more.
• Place a small piece of folded up paper under the USB adapter where it meets the camera.  The constant pulling and movement of this cable can cause the internal parts to break.  The paper will raise up the USB cord so that it does not hang and stress the port.
• Set the photo size from "L" to "S" (the fine setting of S, not coarse).  This will still allow the photo to fill up the entire screen when viewed, but the photos will be about 1.2MB in size instead of 3.6MB.  If space is not a problem, you can keep the full 12MP size and not worry.
• Keep wireless mouse on slit lamp table so you can view pics taken.  You can also buy a wireless keyboard that has a mouse pad if you want to annotate.
• Set up your system to either run though your photos or a slide show as a screen saver.  Better yet, use EyeMaginations (or alternative) and use this as a marketing machine.
• Focusing:
  
  • To test the focus, draw something on the sticky side of a Post It and sitck this on the forehead rest of your slit lamp.
  • Focus on this drawing while looking in the oculars of slit lamp.  The oculars must be set at the most plus position and still be clear.  To do this, pull them out and then push each in until they are just in focus.  Pushing in too far will overminus them and cause image to be blurry on camera even though it is clear in your oculars.
  • With Live View turned on, put the drawing in focus inside the oculars.  If the Live View is not in focus, use the "Fine Focus" knob on the adapter to get it in focus.
  • You may have to work on the oculars and fine focus before you get it perfect.
• ISO Level
  • I use the 1600 instead of auto - it seems to work better.
• Lighting: 
  • Keep the iris on about the 3/4 open setting - you can move this around to suit your needs though, but this will give good lighting and decent depth of focus at same time.
  • The camera will automatically adjust brightness for you to a point.  However, if the lighting is up too high, only the actual beam of light and what it is hitting will show up on your photo.  You do not want to drown out the entire photo, so keep lighting at a medium level.  There should be no need to use a super-bright light when using white light.
• Cobalt Lighting:
  • I'm not an expert here, but I seem to get better photos without a ratten filter.  You will need to push lighting all the way up too.  Also, I have found that only wide beams get picked up well.  The more staining you have on the subject, the better the photo will be.  A tiny amount of SPK is tough to pick up, but large abrasions is easier because of all the light from the excited stain.

I have no financial interest in TTI Medical...

Applicable CPT Codes (from http://chppm-www.apgea.army.mil/doem/coding/ExtOcPhotog.aspx):

• 017.31-017.36 Tuberculosis, eye
• 053.20-053.29 Herpes zoster with ophthalmic complications
• 054.40-054.49 Herpes simplex with ophthalmic complications
• 171.0 Malignant neoplasm of connective and other soft tissue of head, face, and neck
• 172.1 Malignant neoplasm eyelid, including canthus
• 172.3 Malignant neoplasm of skin of other and unspecified parts of face
• 173.1 Other malignant neoplasm of skin of eyelid, including canthus
• 190.0-190.9 Malignant neoplasm of eye
• 215.0 Other benign neoplasm of connective and other soft tissue of head, face, and neck
• 216.1 Benign neoplasm of eyelid, including canthus
• 216.3 Benign neoplasm of skin of other and unspecified parts of face
• 224.0-224.9 Benign neoplasm of eye
• 232.1 Carcinoma in situ, eyelid including canthus
• 234.0 Carcinoma in situ of other and unspecified sites, eye
• 333.81 Blepharospasm
• 350.1-350.9 Trigeminal nerve disorders
• 351.0-351.9 Facial nerve disorders
• 358.00-358.01 Myasthenia gravis
• 360.00–360.19 Disorders of the globe
• 360.21 Malignant myopia
• 364.00-364.05 Disorders of iris and ciliary body
• 364.41-364.42 Vascular disorders of iris and ciliary body
• 364.51-364.59 Degenerations of iris and ciliary body
• 364.60-364.64 Cysts of iris, ciliary body, and anterior chamber
• 364.70-364.77 Adhesions and disruptions of iris and ciliary body
• 370.00-370.07 Keratitis
• 370.20-370.24 Superficial keratitis without conjunctivitis
• 370.31-370.35 Keratoconjunctivitis
• 370.50 Interstitial keratitis, unspecified
• 370.52 Diffuse interstitial keratitis
• 370.54 Sclerosing keratitis
• 370.55 Corneal abscess
• 370.60-370.64 Corneal neovascularization
• 371.00-371.05 Corneal scars and opacities
• 372.00-372.9 Disorders of conjunctiva
• 373.01 Ulcerative blepharitis
• 373.02 Squamous blepharitis
• 373.11-373.13 Hordeolum and other deep inflammation of eyelid
• 374.00-374.9 Disorders of eyelid
• 379.00-379.09 Scleritis and episcleritis
• 379.11-379.19 Other disorders of sclera
• 743.00-743.9 Congenital anomalies of the eye
• 802.6 Orbital floor (blow-out) closed fracture
• 802.7 Orbital floor (blow-out) open fracture
• 802.8 Other facial bones closed fracture
• 802.9 Other facial bones open fracture
• 870.0-870.9 Open wound of ocular adnexa
• 871.0-871.9 Open wound of eyeball
• 909.9 Late effects of injuries, poisonings, toxic effects, and other external causes, eye
• 918.0-918.9 Superficial injury of eye and adnexa
• 940.0-940. Burn confined to eye and adnexa
• 941.02 Burn of unspecified degree of eye (with other parts of face, head, and neck)
• 941.12 Erythema due to burn (first degree) of eye (with other parts face, head, and neck)
• 941.22 Blisters, with epidermal loss due to burn (second degree) of eye (with other parts of face, head, and neck)
• 941.32 Full-thickness skin loss due to burn (third degree nos) of eye (with other parts of face, head, and neck)
• 941.42 Deep necrosis of underlying tissues due to burn (deep third degree) of eye (with other parts of face, head, and neck, without mention of loss of body part
• 941.52 Deep necrosis of underlying tissues due to burn (deep third degree) of eye (with other parts of face, head, and neck) with loss of a body part

Invalid reasons for use of this code:

• The service was performed for an ICD-9 code that is not included in the "ICD-9 Codes That Support Medical Necessity".
• The service was provided for the general taking of photographs.
• The photo-documentation was not required to track the progression, lack of progression of an eye condition, or to track the progression of a particular treatment.
• The provider has not generated an interpretation and report specific to the external ocular photographs.

Coding Guidelines:

• It may be necessary to take a series of photographs in order to document the patient’s progress; code 92285 should be only reported once for a series of photographs taken at one session.

Documentation Requirements:

• In addition to the photograph (s), an interpretation and report specific to the photograph(s) must be contained in the patient’s medical record.