Light-induced iatrogenic phototoxicity due to exposure to an operating microscope was first described by McDonald and Irvine in 1983 after extracapsular cataract extraction. Since then, it is a well-recognized entity noticed following prolonged exposure to light during anterior as well as posterior segment surgeries. Posterior segment surgeries have an additional risk following exposure to endoillumination. In this ophthalmic image, the authors have illustrated the development of phototoxic maculopathy following exposure to light from operating microscopes and endoilluminators after a trans-scleral sutured posterior chamber intraocular lens implantation procedure lasting for 2.5 h.
Phototoxic injury can occur due to photochemical, thermal, or mechanical damage which is dependent on spectral irradiance and duration of exposure of light. However, the most commonly implicated mechanism is photochemical due to exposure to visible light for >10 sec which is insufficient to cause thermal damage. This leads to the formation of intracellular reactive oxygen species causing the damage.
In the acute stage, the lesions may be undetectable or may present as retinal edema within 24–48 hours. Gradually, they may evolve into a hypopigmented lesion with pigment mottling. The lesions caused by operating microscope are typically perifoveal rather than foveal as microscopes are not completely co-axial and it may be round or oval depending upon the light source. On fundus fluorescein angiography, early discrete areas of hyperfluorescence with late staining may be detectable. On spectral domain optical coherence tomography, focal retinal edema with disruption of the photoreceptor integrity and thickening of the underlying retinal pigment epithelium has been described.
Van den Beisen et al. reported that most of the times, the safety limits are exceeded within a minute of exposure to standard endoilluminators during vitrectomy. The permissible exposure time can be exceeded up to 13 min using an additional 475 nm long pass filter, light levels below 10 mW, and maintaining a distance of at least 10 mm between the light probe and the retina. But practically, most of the vitrectomy surgeries are bound to exceed this time limit. Unlike an operating microscope light, the relative light exposure is more for an endoilluminator as it is in close proximity to the retina. It is also dependent on the duration of exposure, irradiation spectrum, and angle of illumination. This makes it tough to set a standard. Yonekawa et al. identified an additional risk factor with the use of indocyanine green dye during internal limiting membrane peeling proposing that the maculopathy may be potentiated by the photosensitizing property of the dye apart from the proximity of the probe tip. Another risk factor suggested by Jaffe et al. was the increase in the inspired oxygen. They noticed a marked increase in the phototoxic damage in rhesus monkeys with an increase in oxygenation.
This iatrogenic retinal phototoxicity can be prevented with the conscious effort of the surgeon to reduce the amount of light exposure to the minimum. The intensity of the light source should be kept just adequate for visualization of structures. The endoillumination probe should be kept as far as possible from the retinal surface and the tissue manipulation with the probe can be avoided. A diffuse illumination can be used wherever possible. The endoillumination probe can be withdrawn from the port when changing instruments in the other hand. Use of special light filters can reduce the amount of retinal damage. The cornea can be covered by a shield when the intraocular part of the surgery is over. Intermittent use of oxygen can also help prevent the development of these lesions. Jaffe et al. recommend complete elimination of the oxygen by nasal prongs in patients <40 years of age under local anesthesia and decreasing the oxygen until after surgery is completed in general anesthesia cases.
1. McDonald HR, Irvine AR. Light-induced retinopathy from the operating microscope in extracapsular cataract extraction and intraocular lens implantation Ophthalmology. 1983;90:945–51
2. Dogra M, Singh SR, Dogra MR. Operating microscope and endoilluminator-induced retinal phototoxic maculopathy after trans-scleral sutured posterior chamber intraocular lens Indian J Ophthalmol. 2019;67:692
3. Jain N, McCuen BW, Mruthyunjaya P. Unanticipated vision loss after pars plana vitrectomy Surv Ophthalmol. 2012;57:91–104
4. Michels M, Sternberg P Jr. Operating microscope-induced retinal phototoxicity: Pathophysiology, clinical manifestations and prevention Surv Ophthalmol. 1990;34:237–52
5. Oh SH, Kim KS, Lee WK. Outer retinal changes in endoilluminator-induced phototoxic maculopathy evident on spectral-domain optical coherence tomography Clin Exp Optom. 2015;98:381–4
6. van den Beisen PR, Berenschot T, Verdaasdonk RM, van-Weelden H, van Norren D. Endoillumination during vitrectomy and phototoxicity thresholds Br J Ophthalmol. 2000;84:1372–5
7. Yonekawa Y, Abbey AM, Shah AR, Thomas BJ, Capone A Jr. Endoilluminator phototoxic maculopathy associated with combined ICG-assisted epiretinal membrane and internal limiting membrane peeling Clin Ophthalmol. 2014;8:2501–6
8. Jaffe GJ, Irvine AR, Wood IS, Severinghaus JW, Pino GR, Haugen C. Retinal phototoxicity from the operating microscope: The role of inspired oxygen Ophthalmology. 1988;95:1130–41