Retinal burns occurring at cataract extraction

Light as a drug: prospective randomized evaluation and comparison of the effect of decreased illumination on visual recovery after cataract surgery

PURPOSE

To compare the effect of decreased illumination on the rate of postoperative visual recovery, and the incidence of cystoid macular edema (CME) with surgical visualization achieved with a traditional analog operating microscope compared with a 3D digital visualization system.

SETTING

Ambulatory surgery center, New York.

DESIGN

Prospective, randomized, consecutive, single-surgeon series.

METHODS

Patients undergoing routine cataract surgery were randomized into either (1) visualization through the binoculars of a standard operating microscope ("traditional group") or (2) visualization through a 3D digital visualization system affixed to the same operating microscope ("digital group"). Note was made in each case of light intensity used, light exposure time, cumulative dissipated energy (CDE), femtosecond laser use, preoperative medical and ocular conditions, intraoperative and/or postoperative complications, and preoperative and postoperative visual acuities and optical coherence tomography confirmed CME.

RESULTS

The study comprised 118 eyes in the traditional group and 96 eyes in the digital group. There were no differences in preoperative visual acuity, light exposure time, CDE, or femtosecond laser use between groups, but the light intensity used in the digital group was significantly less (19.5% ± 0.5%) than in the traditional group (48.6% ± 0.6%; P < .001). Furthermore, the digital group achieved a better decimal postoperative day 1 visual acuity (0.60 ± 0.03) with less rates of CME (2.1%) when compared with that of the traditional group (0.51 ± 0.02, P = .03; and 9.2%, P = .03), respectively.

CONCLUSIONS

Visual recovery and CME rates were significantly better in patients who underwent cataract surgery assisted by the 3D digital visualization platform without an increase in complications or surgical time.

Tolerance to Light of Patients Suffering From Infectious Keratitis

PURPOSE

With very photophobic patients, the advantages of red or near infrared light to develop new ophthalmology imaging devices seem obvious: no or little glare, possibility of long signal integration, no phototoxicity, and lesser autofluorescence of ocular tissues. Nevertheless, in this range, the shortest possible wavelength facilitates signal detection. The aim of this study was, thus, to determine the maximal irradiance tolerated with 6 wavelengths: 2 red, 2 far red, and 1 near infrared lights to determine the shortest wavelength well tolerated by patients, in comparison with the standard cobalt blue light of ophthalmology slitlamp.

METHODS

An interventional, monocentric, single-group assignment study was conducted on 30 eyes of 30 patients with infectious keratitis. Thanks to a customized machine, the photophobic eye was exposed to the 6 lights with increasing intensity. The patients switched off the light when the discomfort was too elevated. The maximal cumulative irradiance possible at 482, 650, 675, 700, 750, and 800 nm were 171, 689, 759, 862, 920, and 889 mW/cm, respectively.

RESULTS

The maximal cumulative irradiance tolerated by patients increased significantly with wavelength (P < 0.001), but the difference was not significant between each increment: red at 675 nm gave a significantly higher cumulative irradiance than blue at 482 nm; red at 700 nm did not provide significant gain compared with 675 nm; and far red at 750 nm still provided additional gain compared with 700 nm, but no significant gain was observed between 750 and 800 nm. The shortest wavelengths were stopped more quickly, and more than 50% of patients reached the maximum irradiance delivered by the source at 750 and 800 nm.

CONCLUSIONS

We demonstrate that a light source at 750 and 800 nm can be used for ophthalmic imaging with good tolerance in photophobic patients.

CLINICAL TRIAL REGISTRATION

NCT03586505.

Efficacy of 3D digital visualization in minimizing coaxial illumination and phototoxic potential in cataract surgery: pilot study

PURPOSE

To compare the coaxial light intensity required during cataract surgery and rate of postoperative visual recovery, with surgical visualization achieved with a traditional analog operating microscope compared with a 3D digital visualization system.

SETTING

Weill Cornell Medical Center, New York Presbyterian Hospital, New York, New York.

DESIGN

Retrospective, consecutive, single-surgeon series.

METHODS

Patients undergoing femtosecond laser-assisted cataract surgery were retrospectively grouped into either: (1) visualization using the binoculars of a standard operating microscope (traditional group) or (2) visualization using a 3D digital visualization system affixed to the same operating microscope (digital group). Note was made in each case of light intensity used, light exposure time, intraoperative and/or postoperative complications, and postoperative visual acuities.

RESULTS

The study comprised 24 eyes in the traditional group and 27 eyes in the digital group. There were no intraoperative or postoperative complications in either group and no difference in mean light exposure time, but the mean light intensity used in the digital group was significantly less (18.5% ± 1.5%) than that in the traditional group (43.3% ± 3.7%; P < .001). Furthermore, the digital group achieved a postoperative day 1 visual acuity that was within 2 lines of the postoperative month 1 visual acuity a greater percentage of time than that in the traditional group (81.5% of eyes vs 54.2% of eyes; P = .04).

CONCLUSIONS

Light intensity was significantly decreased in patients who underwent cataract surgery assisted by the 3D digital visualization platform without an increase in complications or surgical time and possibly with a faster postoperative visual recovery.

Microscope-Induced Thermal Burns During Lymphaticovenular Anastomosis

Bright illumination sources using xenon lamps have improved microsurgical visualization under an operating microscope; however, surgeons must recognize the potential for accidental thermal damage to soft tissues.In this article, we present 2 reports of microscopic thermal burn in lymphaticovenular anastomosis (LVA).A 23-year-old woman and a 57-year-old woman with bilateral lymphedema of the legs had LVAs on both legs under local anesthesia. The burn wound in a 23-year-old woman was full thickness, and the one in a 57-year-old woman was deep dermal burn. Both of them healed without skin grafting.Working distance and high illumination intensity are important risk factor. The use of epinephrine as part the local anesthetic mixture that decreases blood flow is also a major risk factor for thermal burns. Lymphaticovenular anastomosis particularly requires high magnification, which leads to increasing the intensity and decreasing the working distance. The surgical conditions around LVA are inherently prone to microscope-induced thermal burns.

The illumination characteristics of operative microscopes

PURPOSE

Modern operative microscopes use light sources which possess the power to severely damage underlying tissue. Currently, manufacturers provide a safety warning of this possibility. However, they are unable to suggest specific settings due to a stated "lack of scientific publications on this topic". We aim to radiometrically evaluate multiple otologic microscopes at variables which effect irradiance in order to determine reference emissions levels and provide guidelines for improved intraoperative safety.

MATERIALS AND METHODS

The optical radiance of four otologic microscopes was evaluated at variable field illumination sizes (spot size), intensity settings and working distances. The spectral emission of each microscope was separately measured. The energy absorbed in skin with representative properties was then calculated as a function of time for each microscope by accounting for the emission spectrum of the microscope and the absorption spectrum of skin.

RESULTS

Microscopes showed a wide range of optical radiance based on model, spots size, intensity setting and working distances. Spectral emission of all four microscopes was centered in the visible spectrum with minimal ultraviolet or infrared contribution. A large amount of energy is absorbed by skin during usage of operative microscopes. The highest calculated absorption at 200 min of use was 736.26 J/cm(2).

CONCLUSIONS

Operative microscopes have the ability to cause patient morbidity secondary to the energy they impart. In an effort to decrease potential injury we recommend that physicians be aware of their microscopes properties and how to control variables which effect irradiance of the skin.

Rapamycin attenuates visible light-induced injury in retinal photoreceptor cells via inhibiting endoplasmic reticulum stress

An extended exposure of the retina to visible light may lead to photochemical damage in retinal photoreceptor cells. The exact mechanism of retinal light damage remains unknown, and an effective therapy is still unavailable. Here, we demonstrated that rapamycin, an inhibitor of the mammalian target of rapamycin (mTOR), markedly protected 661W photoreceptor cells from visible light exposure-induced damage at the nanomolar level. We also observed by transmission electron microscopy that light exposure led to severe endoplasmic reticulum (ER) stress in 661W cells as well as abnormal endomembranes and ER membranes. In addition, obvious upregulated ER stress markers were monitored by western blot at the protein level and by quantitative reverse transcription-polymerase chain reaction (RT-PCR) at the mRNA level. Interestingly, rapamycin pretreatment significantly suppressed light-induced ER stress and all three major branches of the unfolded protein response (UPR), including the RNA-dependent protein kinase-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1), and activating transcription factor 6 (ATF6) pathways both at the protein and mRNA levels. Additionally, the inhibition of ER stress by rapamycin was further confirmed with a dithiothreitol (DTT; a classical ER stress inducer)-damaged 661W cell model. Meanwhile, our results also revealed that rapamycin was able to remarkably inhibit the activation of mTOR and its downstream factors eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1), p-4EBP1, p70, p-p70, and phosphorylated ribosomal protein S6 kinase (p-S6K) in the light-injured 661W cells. Thus, these data indicate that visible light induces ER stress in 661W cells; whereas the mTOR inhibitor, rapamycin, effectively protects 661W cells from light injury through suppressing the ER stress pathway.

The susceptibility of the retina to photochemical damage from visible light

The photoreceptor/RPE complex must maintain a delicate balance between maximizing the absorption of photons for vision and retinal image quality while simultaneously minimizing the risk of photodamage when exposed to bright light. We review the recent discovery of two new effects of light exposure on the photoreceptor/RPE complex in the context of current thinking about the causes of retinal phototoxicity. These effects are autofluorescence photobleaching in which exposure to bright light reduces lipofuscin autofluorescence and, at higher light levels, RPE disruption in which the pattern of autofluorescence is permanently altered following light exposure. Both effects occur following exposure to visible light at irradiances that were previously thought to be safe. Photopigment, retinoids involved in the visual cycle, and bisretinoids in lipofuscin have been implicated as possible photosensitizers for photochemical damage. The mechanism of RPE disruption may follow either of these paths. On the other hand, autofluorescence photobleaching is likely an indicator of photooxidation of lipofuscin. The permanent changes inherent in RPE disruption might require modification of the light safety standards. AF photobleaching recovers after several hours although the mechanisms by which this occurs are not yet clear. Understanding the mechanisms of phototoxicity is all the more important given the potential for increased susceptibility in the presence of ocular diseases that affect either the visual cycle and/or lipofuscin accumulation. In addition, knowledge of photochemical mechanisms can improve our understanding of some disease processes that may be influenced by light exposure, such as some forms of Leber's congenital amaurosis, and aid in the development of new therapies. Such treatment prior to intentional light exposures, as in ophthalmic examinations or surgeries, could provide an effective preventative strategy.

Retinal light toxicity

The ability of light to enact damage on the neurosensory retina and underlying structures has been well understood for hundreds of years. While the eye has adapted several mechanisms to protect itself from such damage, certain exposures to light can still result in temporal or permanent damage. Both clinical observations and laboratory studies have enabled us to understand the various ways by which the eye can protect itself from such damage. Light or electromagnetic radiation can result in damage through photothermal, photomechanical, and photochemical mechanisms. The following review seeks to describe these various processes of injury and many of the variables, which can mitigate these modes of injury.

Effect of the angle of the operating microscope light beam on visual recovery after phacoemulsification: Randomized trial

PURPOSE

To evaluate differences in visual recovery after phacoemulsification with direct or tilted surgical microscope illumination using a macular photostress test.

SETTING

Western Eye Hospital, Imperial College Health Care National Health Service Trust, London, United Kingdom.

METHODS

This randomized double-masked controlled trial enrolled patients presenting to a daycare unit for single-eye cataract surgery. Inclusion criteria were no ocular pathology other than cataract, corneal keratometric astigmatism less than 1.50 diopters, intended target of emmetropia in the operated eye, and cataract grade 1 to 3 (Lens Opacification Classification System II). Exclusion criteria were an abnormal preoperative photostress test. Patients were randomized to have phacoemulsification with the operating microscope angled 15 degrees nasal to the fovea (study group) or with the operating microscope directly overhead around the optic disc region (control group). The same surgeon performed all phacoemulsification procedures using a standardized technique and topical anesthesia. Outcome measures were uncorrected (UDVA) and corrected (CDVA) distance visual acuity 10 minutes and 60 minutes postoperatively.

RESULTS

In the 30 patients evaluated, the mean UDVA 10 minutes postoperatively was 0.40 logMAR +/- 0.26 (SD) in the study group and 0.72 +/- 0.36 logMAR in the control group (P<.01). The mean CDVA was 0.18 +/- 0.26 logMAR and 0.44 +/- 0.30 logMAR, respectively (P = .016). There was no significant between-group difference in acuity at 60 minutes.

CONCLUSION

Tilting the microscope beam away from the fovea resulted in faster visual recovery and less macular photic stress.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Neurosensory retinal detachment of the macula in retinal phototoxicity documented by optical coherence tomography

PURPOSE

To report a neurosensory detachment documented by optical coherence tomography in operating light microscope-induced retinal phototoxicity.

METHODS

A 53-year-old man had a pars plana lensectomy, core vitrectomy, and posterior chamber sutured intraocular lens implantation in his right eye. The surgery lasted >3 hours.

RESULTS

On postoperative Day 13, best-corrected visual acuity was 20/100. There was retinal pigment epithelial atrophy in the superior macula with subtle pigmentary clumping on its borders. Fluorescein angiography revealed staining in the area of retinal pigment epithelium atrophy with blockage of underlying choroidal fluorescence by the border hyperpigmentation in a pattern typical of phototoxicity. Optical coherence tomography documented a large, central neurosensory detachment. The central macular thickness was 731 μm. Best-corrected visual acuity in the right eye on postoperative Day 31 had improved to 20/60, and the optical coherence tomography had minimal subretinal fluid with a central macular thickness of 226 μm. On postoperative Day 78, there was no subretinal fluid, best-corrected visual acuity was 20/50, and the central macular thickness was 191 μm. Four months postoperatively, best-corrected visual acuity was 20/30.

CONCLUSION

Microscope light-induced retinal phototoxicity may be associated with a neurosensory detachment.

Recovery from macular phototoxicity after corneal triple procedure

PURPOSE

Visual recovery from macular phototoxicity in 2 cases after prolonged exposure to operating microscope light from uncomplicated corneal triple-procedure surgery. Recovery is discussed in the context of repair and regeneration.

METHODS

Retrospective case reports.

RESULTS

Immediately postoperatively, both patients reported positive scotomata and were found to have macular retinal pigment epithelial depigmentation. In 1 case, the fovea was involved. By 6 to 12 months, the scotomata had disappeared despite large areas of retinal pigment epithelial hyperpigmentation remaining.

CONCLUSION

Recovery from macular phototoxicity occurs, although the mechanism remains unclear. Positive scotomata in these cases resolved over several months. The time scale of recovery was consistent with the time required for cellular replacement and possible differentiation from neural progenitor cells.

PHOTIC RETINOPATHY AFTER CATARACT SURGERY IN DIABETIC PATIENTS

PURPOSE

To report and emphasize photic retinopathy (PR) after cataract surgery in diabetic patients.

METHODS

The charts of 2,573 patients who underwent cataract surgery at Baskent University Hospital (Ankara, Turkey) between January 2001 and December 2003 were retrospectively analyzed for PR and diabetes mellitus (DM). All surgeries were performed using the same coaxial illuminated microscope. The diagnosis of PR was confirmed by fluorescein angiography, showing typical mottled fluorescein transmission in a well circumscribed area in each case. Statistical analyses were performed with chi2 and Mann-Whitney U tests.

RESULTS

Diagnoses of PR and DM were established in 16 cases (0.62%) and 382 cases (14.85%), respectively. DM was present in 7 (43.75%) of the PR cases. PR occurred more frequently in DM patients than in non-DM patients (7/382 vs. 9/2,191, respectively; P = 0.001; chi2= 10.64). All 16 patients with PR had received retrobulbar anesthesia (RA). RA was used in 61.21% of all surgeries and in 78.01% of the surgeries for DM patients. Occurrence of PR during RA was higher for DM patients than for non-DM patients (7/298 vs. 9/1,277, respectively; P = 0.011; chi2= 6.50). Mean operation times +/- SD for PR cases were 29.9 +/- 9.9 minutes and 38.2 +/- 5.3 minutes in DM and non-DM cases, respectively (P = 0.091). None of the photic lesions were sight threatening.

CONCLUSIONS

Diabetic patients may be more vulnerable to photic injury. Surgeons should take precautions to prevent PR when performing cataract surgery on diabetic patients.

Lightless cataract surgery using a near-infrared operating microscope

PURPOSE

To describe the near-infrared (NIR) operating microscopy (NIOM) system using the NIR wavelength as the illumination source and to evaluate the feasibility of this system for lightless cataract surgery.

SETTING

HenAm Kim Eye Center, Haenam-Gun, South Korea.

METHODS

In this noncomparative interventional case series, cataract surgery was performed in 4 patients with bilateral cataract using the NIOM system in 1 eye and conventional microscopy in the fellow eye. The primary components of the system include an optical filter, a stereoscopic camera, head-mounted displays, and a recording system. This system uses invisible NIR (wavelength 850 to 1300 nm) illumination to facilitate cataract surgery without light. The differences between the NIOM system and conventional microscopy during cataract surgery were evaluated.

RESULTS

The NIOM system provided excellent 3-dimensional viewing in real time. The image resolution was sufficient while performing all steps of cataract surgery. Immediately postoperatively and at 10 and 30 minutes and 1 hour, the visual acuity was better in the 4 eyes in which the NIOM system was used than in the 4 eyes in which conventional microscopy was used. However, using the NIOM system required good surgical skill.

CONCLUSIONS

Lightless cataract surgery using the NIOM system seems useful for obtaining good visual acuity immediately postoperatively. The system may also reduce the incidence of light-induced retinal toxicity and the need for mydriatic administration and be a good educational tool.

Study of the effect of involuntary user movement on the potential light hazards from some ophthalmic instruments

A study was undertaken to determine whether involuntary user movement provides a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the eye from slit lamps and indirect ophthalmoscopes. This was accomplished by assessment of the extent to which light from these devices can be maintained in focus on a 1-mm-diameter fiber-optic cable for 45 s. The results suggest that, although involuntary user movements can be significant, they do not provide a basis for relaxing the measurement conditions for evaluating the potential optical radiation hazards to the cornea and lens from slit lamps and indirect ophthalmoscopes.

Microscope-induced retinal phototoxicity in cataract surgery of short duration

OBJECTIVE

Microscope-induced retinal phototoxicity has been described after prolonged cataract surgery, usually in operations lasting longer than 100 minutes. The purpose of this study was to compare the features of microscope-induced retinal phototoxicity occurring in patients who underwent cataract surgery of short duration and long duration.

DESIGN

A retrospective nonrandomized comparative trial.

PARTICIPANTS

Thirty-four patients, whose medical records documented the development of phototoxic lesions in the retina as a result of cataract surgery, were divided into two groups: group A with 14 patients whose operating time was 30 minutes or less, and group B with 20 patients whose operating time was greater than 30 minutes.

INTERVENTION

All patients underwent either phacoemulsification or extracapsular cataract extraction (ECCE) with implantation of an intraocular lens.

RESULTS

The mean operating time was 23.1 minutes (range, 11-30 minutes) in group A, and 60.8 minutes (range, 34-123 minutes) in group B. Phacoemulsification was done more often in group A (P = 0.001) and ECCE in group B (P = 0.0003). A final refraction of +/- 1 D was achieved by 12 eyes (86%) in group A and by 12 eyes (60%) in group B (P = 0.11). The correlation between final refraction and duration of the operation was significant; the closer the final refraction approached to emmetropia, the shorter the duration of surgery (r = 0.53; P = 0.001). Diabetic retinopathy was more common in group A (P = 0.03).

CONCLUSIONS

Phototoxic lesions of the retina may occur during cataract surgery even when the duration of the operation is short. The most relevant associated factors found in this study were correction approximating emmetropia and diabetic retinopathy.

Study of filtered light on potential retinal photic hazards with operation microscopes used for ocular surgery

There have been numerous reports of retinal photic injury from operation microscopes used during cataract surgery. The risk of injury has been associated with the intensity of the light directed into the eye, short-wavelength emission, user technique, exposure time, and direct axial lighting. We evaluated use of light transmission filters to modify a tungsten-halogen light source spectrum to reduce the risk of retinal photic injury. A two-light source filter combination was found with a color profile acceptable for intraocular surgery that reduces the risk of retinal photic injury by a factor of approximately 2.5.

Updating on intraoperative light-induced retinal injury

We are presenting the state of knowledge concerning intraoperative light-induced retinal injury, considered to be a combination of photic retinopathy and retinal photocoagulation. It may arise from retinal light exposure to the operating microscope or to the fiberoptic endoilluminator. Ultraviolet and short-wavelength visible light are more dangerous than longer wavelength light. Many risk factors may facilitate the onset of this iatrogenic disease following surgery. Many aspects of the retinal damage are still poorly understood. Many mid light-induced retinal injuries probably remain undiagnosed in routine postoperative examination. Current appropriate light filters are not the definitive solution. Appropriate precautions should be taken during both anterior segment and vitreoretinal surgery.

Subclinical operating microscope retinopathy: the use of static perimetry in its detection

Focal retinal pathology and dysfunction as a sequel to manifest damage due to operating microscope illumination is well recognised. We wished to determine whether retinal dysfunction could be identified in the absence of clinically visible lesions. We therefore have conducted a prospective controlled study on 36 patients undergoing cataract surgery and 27 control subjects. A Wild M690 zoom operating microscope was used for each procedure. No filters were used. The Humphrey visual field equipment was employed to determine threshold retinal sensitivity at predetermined loci above and below fixation in both groups. No clinically visible retinal lesions were seen in any patient. However, post-operative investigation revealed a statistically significant depression in retinal sensitivity at points most exposed to operating microscope illumination (p < 0.05). This was most noticeable following longer total operating times and in patients with the longest time intervals between lens extraction and completion of the procedure. It is concluded that operating microscope position and centration, and the position of the eye, should be adjusted to place the image of the illuminating element away from the foveola. Also retinal illumination should be kept to a minimum, particularly after an intraocular lens has been implanted.

Photic maculopathy after extracapsular cataract surgery. A prospective study

Photic retinal injuries have been described after surgical exposure to the intense illumination systems of operating microscopes. The overall incidence of such injuries has been postulated at less than 10%. The authors prospectively studied 43 consecutive patients to determine the incidence of photic macular injuries during cataract surgery. Patients underwent complete ophthalmic examinations, fundus photography, and oral fluorography before and after surgery. Photic macular injuries developed in 12 of 43 eyes (28%) as a result of intraocular surgery. This incidence is much higher than previous estimates. The association with possible risk factors, cystoid macular edema, and the effect of these injuries on final visual acuity are discussed.

Pathologic findings of photic retinopathy in the human eye

The macular retina of a patient whose eye was scheduled for enucleation because of progressive growth of a malignant melanoma that had invaded the iris and filtration angle was exposed to unfiltered light from the operating-room microscope for 60 minutes. Photic maculopathy was documented with fundus photography and fluorescein angiography 67 hours after light exposure. Seventy-two hours after light exposure, the eye was enucleated, fixed in Trumpe's solution, and studied with light microscopy and electron microscopy. Findings included localized necrosis of the retinal pigment epithelium; loss of the apical villi, plasma membranes, and cytoplasmic organelles; extrusion of pigment granules; and extensive disruption of the outer lamellae of the photoreceptors. The inner segments of the photoreceptors were edematous and contained swollen mitochondria. Near the margins of the photic retinopathy, thinned retinal pigment epithelial cells appeared to have migrated under injured retinal pigment epithelial cells, suggesting early attempts at repair. Additional findings included Müller-cell swelling.

Photic retinal injury from endoillumination during vitrectomy

We treated a patient who developed a paramacular area of light-induced retinal damage after endoscopic epimacular membrane removal. Postoperative color photographs showed complete absence of the membrane, but fluorescein angiography demonstrated a previously absent superior paramacular lesion consistent with a photic injury. Operative microscope illumination had been eliminated by corneal shielding, which implicated endoillumination as the source of injury. We recommend the following procedures to avoid this complication: careful planning of vitreous surgery for epimacular membrane removal; using filters; minimizing the length of surgery; keeping the light output low; maintaining maximal light pipe distance from the retina; eccentric orientation of the light pipe; and use of intermittent and variable site illumination techniques.

Operating microscope-induced retinal phototoxicity: pathophysiology, clinical manifestations and prevention

Retinal light damage is a poorly understood phenomenon, due to its multifactorial etiology and relatively infrequent recognition. It has been increasingly identified following ocular surgery involving the intense light of the operating microscope. The authors describe the clinical entity, review salient features of its pathophysiology and provide guidelines for prevention of retinal phototoxicity.

The site of operating microscope light-induced injury on the human retina

We determined the site of the focal illumination from the Zeiss OPMI-6 operating microscope on the retina of the phakic and aphakic human cadaver eye by directly observing the illuminating element image on the posterior scleral surface of the globe. With the eye straight ahead and the operating microscope level, the focal oval area of retinal illumination was located superior to the foveola in both the phakic and aphakic eye. Tilting the operating microscope 10 degrees toward the surgeon displaced the entire illuminating element image 0.50 mm below the foveola in the phakic eye and 0.25 mm below the foveola in the aphakic eye. Rotating the eye inferiorly 10 degrees displaced the entire illuminating element image 1.0 mm below the foveola in the phakic eye and 1.25 mm below the foveola in the aphakic eye. Centering the field of view superiorly (viewing the superior limbus) paradoxically displaced the illuminating element image inferiorly, resulting in central foveal illumination. Foveal light exposure was avoided in most eye positions by tilting the microscope at least 10 degrees toward the surgeon.

Microscope light-induced maculopathy in combined penetrating keratoplasty, extracapsular cataract extraction, and intraocular lens implantation

A characteristic retinal phototoxicity reaction was noted in four patients who underwent penetrating keratoplasty, extracapsular cataract extraction (ECCE), and intraocular lens (IOL) implantation. This complication has been well documented in association with other ocular procedures, but only one previous similar case has been reported. The authors bring this potential complication to the attention of corneal surgeons, discuss the risk factors, and offer suggestions on prevention.

Three cases with light-induced retinopathy

Three patients presented a characteristic retinopathy presumably induced by light arising from operating microscope during extracapsular cataract extraction combined with intraocular lens insertion. The operating microscope was equipped with video-recorder. Light sources were tungsten bulb. All cases were asymptomatic and an inspection at the post-operative control examination led to the detection of this type of retinopathy.

Light-induced maculopathy and cystoid macular edema

We present two patients with paramacular burns induced by the operative light microscope. In one case there was associated cystoid macular edema. Of the 34 total reported cases of paramacular burns, there have been only two cases of cystoid macular edema. Thus, although the total number of reported cases of light-induced maculopathy is small, this disorder does not appear to predispose to cystoid macular edema. Loss of visual acuity is mainly caused by the proximity of the burn to the fovea.

Solar radiation and age-related macular degeneration

Age-related macular degeneration (AMD) involves a progressive impairment of the outer layers in the center of the retina. Experimental studies have demonstrated that bright light preferentially damages precisely the region that degenerates in AMD. The evidence that solar radiation is responsible for some of the deteriorative changes that lead to AMD is examined in this review. In the primate eye, the high-energy portion of the solar spectrum is most hazardous to retinal molecules, with damaging effects increasing as photon energy rises. This action spectrum is explicable by the quantum laws which describe the interaction of radiation with matter. High-energy visible and ultraviolet photons can produce molecular damage by a photochemical mechanism. The lesion is exacerbated by oxygen, which initiates free-radical chain reactions (photodynamic effects). Melanin exerts a protective effect against damage from sunlight. In the human retina, documented lesions from solar radiation range from the acute effects of sun-gazing to injuries resulting from prolonged periods of exposure in brightly illuminated environments. The damage occurs in the same region that degenerates in AMD. A cataractous lens and ocular melanin both protect the retina against AMD, as predicted by the radiation hypothesis. Identification of an environmental factor that evidently plays a role in the etiology of AMD provides the basis for a program of preventive medicine.

A model for predicting the site of paraxial retinal lesions secondary to "coaxial" operating microscope illumination systems

We measured a 15 +/- 2-mm displacement of the illuminating element of the coaxial operating microscope from the true optical center of the microscope. We further calculated the displacement of the image of the illuminating element of the operating microscope on the retina of the simplified schematic eye and found that the "coaxial" operating microscope would focus the light between 1.3 and 1.8 mm superior to the fovea of the eye, depending on the theoretical refractive status of the simplified eye. Actual measurements on a simulated retina (35-mm camera) confirmed the calculated displacements. The deviation varied with eye tilt and microscope position. We also found that the maneuvers commonly used by anterior segment surgeons of tilting the microscope and rotating the eye downward tended to displace the image of the illuminating element closer to the fovea, increasing the chance for symptomatic retinal damage. A combination of such maneuvers may reduce the potential for clinically significant retinal phototoxicity by displacing the light further inferior to the fovea.

Effects of yellow filter glasses on colour discrimination of normal observers and on the illumination level

Ten healthy young persons wearing yellow filter glasses were examined with the Farnsworth-Munsell 100-hue test using a Macbeth daylight illuminator. Results obtained with (Schott) filters GG 400, GG 420, GG 435 and GG 455 were within normal limits. Using filters GG 475, GG 495 and OG 515 the mean total error score was 123.9, 203.8 and 226.9, respectively, and the test diagram showed a tritan error axis. Illumination of the Macbeth daylight illuminator measured without filters was 1800 lux. Using yellow filters the illumination varied from 1650 to 1500 lux.

Infrared. An unseen and unnecessary hazard in ophthalmic devices

The concept of instrument-induced light damage to the retina is well established. Many have argued that ultraviolet (UV) energy is overwhelmingly responsible and that longer wavelength infrared (IR) energy causes thermal change and plays a minimal role. We suggest that infrared may play a primary role in instrument-induced damage. We measured the radiometric and photometric outputs from commonly used ophthalmic devices in normal use and in IR-blocked conditions. We found IR output to represent a significant portion of the total irradiation produced by these instruments. Infrared was easily and inexpensively minimized without compromising usable visible light in these instruments using an efficient IR filter. The instruments' incandescent lamps, glass envelopes, and optics are poor UV emitters or transmitters. Manufacturers' data do not indicate UV emission. Evidence for UV blocking and IR transmission by the intraocular media is presented.

Radiation of the fiberoptic illuminator of an operating microscope

Relative radiation spectrum of a fiberoptic illuminator of an operating microscope (Zeiss Opmi 6) was measured with a spectrophotometer within the range of 350 to 1100 nm. Total irradiance at the corneal level was measured with a radiometer within the range of 250 to 4000 nm. Illumination was measured with a standard illuminometer. Two selective filters were used to optimally reduce the total radiation. A Schott filter GG 420 was used to cut off ultraviolet radiation and a Schott thermal filter KG 1 to reduce intrared radiation. Measured without filters the energy of radiation of wavelengths shorter than 400 nm was only 0.05% of the total energy of radiation, 78.5% was within the range of 400 to 780 nm, and 21.4% was produced by radiation of wavelengths longer than 780 nm. Corresponding values measured with selective filters were 0.003, 95.4 and 4.6. Irradiance at the corneal level was 7.7 mW/cm2 without filters and 3.8 mW/cm2 with selective filters, and the corresponding illumination levels were 21,300 and 16,500 lux. Using selective filters the total irradiance was effectively reduced causing only a minor reduction of the illumination level and a small just noticeable alteration of the colour of the operating field.

Photic retinopathy from the operating room microscope

Photic retinopathy was produced in two patients after a 60-minute exposure to light from an operating room microscope (Zeiss OpMi 6). The first patient had a blind eye with clear (phakic) media and a normal-appearing retina. A 60-minute exposure produced an oval gray lesion in the posterior pole at the level of the pigment epithelium. With an ultraviolet-400 filter added for a second exposure, a second lesion was produced. The second patient received a 60-minute exposure (without an ultraviolet filter) 72 hours before enucleation for a malignant melanoma. This produced photic retinopathy that resulted in a slight decrease in central visual acuity and a dense paracentral scotoma. This conclusively establishes a cause-and-effect relationship between exposure to the light from an operating room microscope and a retinal lesion in the human eye.