Abstract
Purpose :
Blue light, produced with a cobalt filter, is used in conjunction with fluorescein for the assessment of corneal surface defects (e.g. abrasions, ulcers, erosions, lesions), tear film breakup / tear film visualization, and contact lens fitment. At present these filters are glass based and have been expensively adapted for smart phone use for portability. Here we sought to create a cheap and compact 3D printed cobalt filter report that can be adapted for any light source or smart phone for less than 10 cents (USD).
Methods :
Five commercially available 2.75 mm filaments were selected for their potential in producing usable blue light in both ambient light and darkened exam room conditions. Ten mm diameter filter disks were printed at 0.5 mm thickness intervals up to 5 mm. Discs were fitted over the LED flash assembly on a iPhone 8 and assessed for fluorescein response. Print conditions were per the default Cura Lulzbot Edition (v 2.6.69) settings for each respective material on a Lulzbot TAZ6. Print orientation, infill, and segment layer height were then manually adjusted for maximum fluorescein response at the thinnest disk material thickness.
Results :
Two polyethylene terephthalate (PET) type filaments had the best fluorescein response but had different minimum thicknesses required to elicit fluorescein responses. A PETG analogue had the best fluorescein response at a thickness of 2.5 mm at 100% infill in a crosshatch layer pattern at a layer height of 0.14 mm. This print required using 0.2 meters of filament at an estimated cost of 10 cents of material. The PETG analogue showed equal-to or better performance compared to a slit lamp based cobalt filter.
Conclusions :
Here we report on the successful creation of an inexpensive and thin cobalt filter that can be 3D printed on any type of fused filament deposition printer for any ophthalmic application requiring cobalt blue light for examination or imaging. To the best of our knowledge this the first time a 3D printed object has been used to create a light filter for medical applications. The success of the filter even in ambient light conditions expands the capabilities of fluorescein visualization in non-ideal settings, such as outdoor clinics.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.