Detection of retinal laser injury using confocal scanning laser imaging.

The use of laser energy in medical practice requires specific safety measures. Accidental ocular exposure of laser can have vision-threatening consequences. We report a case of accidental laser exposure in a dentist who was working with a diode laser. The patient presented within 24 hours of exposure and the clinical fundus examination and spectral-domain optical coherence tomography (SDOCT) were unremarkable at this time. Blue light autofluorescence (BAF) and multicolor images obtained using the Spectralis SDOCT system revealed the laser impact site. The multicolor image showed a larger extent of retinal involvement highlighting its role in imaging.

Laser is used for treatment in various medical disciplines including ophthalmology, dermatology, and dentistry. The use of laser is an established mode of treatment for cancerous and precancerous oral lesions. Diode laser (810 nm) has been used to treat oral leukoplakia and oral lichen planus.[1] CO2 laser has been used in conditions like aphthous ulcers and tissue excesses.[2] Working with a laser requires safety precautions to avoid accidental exposure. The eye in general and retina, in particular, is 100000 times more prone to laser damage than skin when working in the range of 400–1400 nm.[3] Detection of retinal laser damage requires detailed clinical examination and imaging as they can be subtle and mimic other retinal diseases.[45] Multicolor imaging (MC) of the retina is a novel imaging modality that is increasingly being used to identify various retinal conditions.[6] We herein report multimodal imaging features of laser-induced accidental retinal injury in a dentist.

Case Report

A 58-year-old dentist presented with a blurring of vision in both eyes following exposure to diode laser a day ago. The best-corrected visual acuity (BCVA) was 6/6 N6 in the right and 6/60 N36 in the left eye. He had a history of central serous chorioretinopathy (CSC) in the left eye few years ago.

Old records revealed the BCVA was same as the current visit in both eyes. Figs. 1 and 2 depict the findings during the last visit one year ago. The right eye [Fig. 1a] had no subretinal fluid (SRF). The left eye had SRF, noted on MC image [Fig. 1b] using Spectralis spectral-domain optical coherence tomography (SDOCT). SDOCT of the right eye [Fig. 1c] was normal whereas the left eye [Fig. 1d] showed fibrin at fovea and SRF. Blue light autofluorescence (BAF) image of the right eye [Fig. 1e] was unremarkable during his last visit. The left eye showed hyperfluorescence over SRF [Fig. 1f]. Individual blue reflectance (BR) [Fig. 2a], green reflectance (GR) [Fig. 2c], and infrared reflectance (IR) image [Fig. 2e] of right eye were normal. Compared to BR [Fig. 2b] and GR images [Fig. 2d], the extent of the SRF was best seen on the IR image [Fig. 2f] in the left eye.

Figure 1

(a) Previous visit multicolor (MC) image of the right eye shows normal macula. (b) MC image of left eye shows subretinal fluid (SRF) shown by solid arrowheads whereas central retinal pigment epithelium (RPE) atrophy is seen as orange – red hue (blank arrow). (c) SDOCT line scan shows thick choroid and normal foveal architecture in right eye. (d) SDOCT line scan of left eye shows thick choroid and fibrin at fovea seen homogenous hyperreflective deoposits and SRF on sides. (e) Blue light autofluorescence (BAF) of right eye was normal. (f) BAF image of left eye showed SRF as hyperautofluorescence

Figure 2

(a) Previous visit blue reflectance (BR) image of right eye shows normal pattern. (b) BR image of left eye shows margin of SRF (arrowhead). (c) Green reflectance (GR) image of right eye showed normal reflectance. (d) GR image of left eye showed the margin of SRF (arrowheads) more distinctly than BR image. (e) Infrared reflectance (IR) image of right eye showed normal reflectance. (f) IR image of left eye showed the margins of SRF (arrowheads) and central RPE atrophy (blank arrow)

Clinical examination with an indirect ophthalmoscope and slit-lamp biomicroscopy at the current visit after exposure to laser was unremarkable in the right eye whereas the left eye showed retinal pigment epithelium (RPE) atrophy and trace subretinal fluid. The color fundus photograph of the right eye [Fig. 3a] was unremarkable whereas the left eye [Fig. 3b] showed RPE alterations. MC image [Fig. 3c] of the right eye showed a circumscribed area of orange-yellow hue involving both arcades, papillomacular bundle, and fovea. There was an optic disc sized circular zone of altered hue near the superior arcade. MC image of the left eye [Fig. 3d] showed a margin of RPE atrophy as a darker hue. SDOCT image of the right eye [Fig. 3e] showed no change in the retinal layers whereas the left eye showed trace SRF and loss of outer retinal layers [Fig. 3f]. BAF image of the right eye [Fig. 3g] showed a circumscribed area of hyperautofluorescence corresponding to the circular zone of altered hue on the MC image. BAF image of the left eye [Fig. 3h] continued to show hyperautofluorescence due to trace SRF. Circumscribed areas of hyperreflectance were noted on BR [Fig. 4a], GR [Fig. 4c], and IR [Fig. 4e] images in the right eye, which corresponded to the orange-yellow hue seen on MC image. The circular zone of altered hue was best seen on IR [Fig. 4e] image. Boundaries of SRF were best seen on GR [Fig. 4b, d and f] image in the left eye. A diagnosis of laser-induced retinal injury in the right eye was made.

Figure 3

(a) Color fundus photograph of right eye shows normal fundus. (b) Color fundus photograph of left eye showed RPE alterations. (c) After laser exposure the MC image of right eye showed circumscribed area of orange – yellow hue over macula over area between optic disc and fovea. Within this area there was a circular zone of altered hue near (arrows) near superior arcade which was the site of laser beam impact. (d) MC image of left eye shows margins of SRF with multiple orange red areas within SRF suggestive of RPE atrophy. (e) SDOCT line scan through the macula does not show any change in the reflectivity of individual layers. (f) SDOCT image of left eye shows trace SRF with loss of external limiting membrane and ellipsoid zone along with thinning of outer nuclear layer. (g) BAF image of right eye showed a circular zone of hyperautoflourescence which corresponded with circular zone of altered hue seen on MC [Figure 3c] image. Rest of the macula showed normal fluorescence. (h) Hyperautofluorescence was noted over SRF in left eye on BAF image

Figure 4

(a) After exposure of laser the BR image of right eye showed circumscribed area of hyperreflectance coinciding with the same on MC image. The laser impact site noted on MC image is barely seen on BR image (arrow). (b) BR image of left eye showed margins of SRF (arrowheads). (c) GR image showed the circumscribed area of retinal involvement as hyperreflectance better than GR. The laser impact site (arrow) is also seen better than BR image. (d) GR image of left eye showed the margin of SRF (arrowheads) more distinctly than BR image. (e) IR image of right eye showed circumscribed area of hyperreflectance which is smaller than that seen on GR whereas laser impact site (arrows) is best seen on IR. (f) IR image of left eye continued to show margins of SRF (arrowheads) and central RPE atrophy (blank arrow)

Discussion

Retinal injury due to laser can occur both as exposure during work or accidental exposure to laser pointers.[78910] The present case highlights the adverse effect of such an exposure as an occupational hazard in a dentist, which is hitherto unreported in literature.

Although the patient maintained BCVA in the right eye and clinically did not have any discernible retinal change, the MC image showed the altered retinal reflectivity after exposure. The optic disc sized circular zone of altered hue noted on the MC image [Fig. 3a] corresponded with the circumscribed area of hyperautofluorescence noted on BAF [Fig. 3e], which suggests that this area might be the point of impact of a laser beam. The hyperautofluorescence on BAF may have been caused by increased photoreceptor degradation and increased production of lipofuscin within the area. What MC image further added to the knowledge was the exact and larger extent of retinal involvement due to laser, which extended beyond the area of hyperautofluorescence and involved the entire retina between fovea and optic disc. It is intriguing to note that SDOCT scan of this area did not show any change in the retinal anatomy at the present time. The SDOCT changes would probably develop with time.

Individual reflectance images of the right eye showed the same area of hyyperreflectance coinciding with the orange-red hue noted on the MC image. The hyperreflectance was most pronounced on the GR image [Fig. 4c] suggesting affection of the inner and middle retinal layers more than outer retinal layers. MC, BAF, and reflectance image of the left eye remained unchanged after laser exposure, which may be because the patient was using the right eye alone while working.

Conclusion

The present case highlights the risk associated with accidental exposure to the dental laser to the retina. It also highlights the role of MC imaging to detect the retinal damage, which was not clinically discernible.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/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.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.