© 2002 by the American Society for Dermatologic Surgery, Inc. • Published by Blackwell Publishing, Inc.ISSN: 1076-0512/02/$15.00/0 • Dermatol Surg 2002;28:1088–1091

CASE REPORT

Vitreous Floaters Following Use of Dermatologic Lasers

Murad Alam, MD,* Nauman A. Chaudhry, MD,

†

and Leonard H. Goldberg, MD, FRCP

‡§

*Department of Dermatology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois,

†

New England Retina Associates, Hamden, Connecticut, and

‡

DermSurgery Associates and

§

Department of Medicine (Dermatology),

University of Texas, M. D. Anderson Cancer Center, Houston, Texas

background.

Laser eye protection has been designed to pro-tect operators and patients from severe eye injuries.

objective.

To describe two cases in which lasers used for cu-taneous therapy may have been associated with the induction ofvitreous floaters, a subacute eye injury, in physicians operatingthese devices, and to review the theoretical feasibility of suchinjuries, prior reports of the same, and strategies for minimizingrisk.

methods.

Report of two cases and review of the literature.

results.

Given the circumstantial evidence, it is possible thatsubacute vitreous injuries may be sustained by the operators of

dermatologic lasers. Ex vivo experiments and previous case re-ports have demonstrated the possibility of laser-induced vitre-ous injury, including changes in vitreous conformation and vit-reous hemorrhage, in the absence of permanent retinal deficits.It may be speculated that vitreous floaters are a milder manifes-tation of such subacute injuries.

conclusion.

To the extent that vitreous floaters can multiplyand presage the onset of severe retinal injury, the risk of theirinduction by dermatologic lasers should be minimized. Simplestrategies and further research can help achieve this goal.

M. ALAM, MD, N. A. CHAUDHRY, MD, AND L. H. GOLDBERG, MD, FRCP HAVE INDICATED NO SIGNIFICANT INTEREST WITH COMMERCIAL SUPPORTERS.

VITREOUS FLOATERS are a common subjectivecomplaint among patients presenting to ophthalmolo-gists.

1–3

These floaters present as translucent to shad-owy opacities, morphologically resembling dots andfibrous streaks, that partially occlude the visual fieldof either one or both eyes. Microscopically floaters aredisruptions in the vitreous gel that fills the inside ofthe globe of the eye and provides for even conductionof light from the cornea and lens to the retina at theback of the eye. Onset of floaters is typically after age50 years,

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when the homogeneous vitreous gel ofyouth begins to separate and condense into a fluid ofsmaller particles. By definition, floaters are caused byglial tissue of epipapillary origin that adheres to theposterior hyaloid membrane (an indicator of posteriorvitreous detachment), as well as by fiberlike intravitre-ous opacities associated with vitreous liquefaction andcollagen fiber aggregation. Most patients with floatersare mildly to moderately bothered by the impediment,to which they adjust over time. Visual acuity is not af-fected in the majority of instances, but floaters do notresolve once they occur, and tend to worsen gradually.Normal aging and trauma

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are the primary causes of

vitreous floaters, and trauma is more likely to lead toassociated complications. In any event, new onsetfloaters of any presumed etiology must be evaluatedby an ophthalmologist, since posterior vitreous de-tachment from the retina and associated vision lossdoes occur in a minority of patients. Retinal detach-ment may occur several weeks after vitreous injury,and timely eye examination upon the advent of float-ers may identify impending retinal injury, and so en-able prophylactic treatment before impairment ofsight.

We present two cases of floaters in young physi-cians. In both, floaters were noted for the first timewithin a few months of beginning work with lasers.

Case Reports

Patient 1

A 32-year-old male laser surgery fellow in a dermato-logic laser practice presented to an ophthalmologistfor evaluation of new-onset floaters of the right eye.

These manifested as dark dots and filamentous, thread-like, translucent opacities that were persistently super-imposed on his visual field. The patient reported thathe had begun his laser training 3 months earlier andpreviously had had extremely little experience usingsuch devices. He noted that 2 days prior to his initiallynoticing the floaters, he had been treating telangiec-

Address correspondence and reprint requests to: Murad Alam, MD,Department of Dermatology, Northwestern University, 675 N. St. ClairSt., Suite 19-150, Chicago, IL 60611, or e-mail: murad@alam.com.

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tatic leg veins with a high-energy pulsed dye laser(PDL). Leaning close to the treatment site, he hadnoted a bright flash in his right (dominant) eye, whichwas aligned with the laser handpiece and about 15 cmdistant. At the time he was wearing blue standard-issue wraparound safety goggles for the 595 nm PDL,but recalled that they were set low on his face and hebelieved the flash reached his eye over the top rim ofthe glasses.

Serial slit-lamp examinations 1 month apart by twoophthalmologists revealed the presence of a moderatenumber of vitreous opacities (floaters) in the right eye,but no posterior vitreous detachment, retinal hemor-rhage, or retinal breaks. The left eye was unaffected.Upon questioning, the patient noted the occasional,but rare, incidence of spontaneous light flashes. Hedenied trauma to the eyes in the recent or distant past.The patient had normal, uncorrected vision, with nohistory of myopia or surgical correction prior to thepresence of floaters, and this visual acuity remainedunchanged at both the examinations.

Over the ensuing 3 months, the patient noted nonew floaters and gradually acclimated to the mild vi-sual obstruction caused by the floaters that persisted.

Patient 2

A 29-year-old female laser surgery fellow in a derma-tologic laser practice noticed the presence of a translu-cent dark spot at the edge of her visual field thatwould occasionally partially obstruct her vision. Thesmall spot was unilateral, in the right eye, and wouldbe barely visible for long periods of time. Then, spo-radically, it would migrate closer to the center of herfield, where it would mildly cloud her visual field.

After discussion with an ophthalmologist, the pa-tient recognized that her symptoms were indicative ofthe presence of a floater. As the floater was solitaryand minimally troublesome, she opted to defer a for-mal slit-lamp examination. The patient was not myo-pic and denied any history of ocular trauma.

While the patient was unable to precisely time theonset of the floater, she was certain that it had oc-curred within the first 3 months of her fellowship. Shehad not had any similar symptoms prior to the start ofher laser work. She did not receive a retinal examina-tion close to onset, but during a routine eye examina-tion approximately 1 year later was found to have noretinal pathology.

Discussion

Anatomically, as the vitreous condenses and contracts,this increased mobility may result in traction on theposterior vitreous adjacent to the retina. Retinal

breaks may occur as part or all of the retina is tornaway. This detachment of the retina results in blind-ness and is a vitreoretinal emergency.

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In the vast ma-jority of cases, the new onset of a floaters alone doesnot herald imminent retinal detachment, but it is awarning sign that should trigger screening.

7,8

Whenslit-lamp examination reveals large numbers of vitre-ous cells (graded 2

�

or worse),

9

or subjective floatersare accompanied by periodic light flashes,

2

or there isgrossly visible vitreous or preretinal blood,

10

the likeli-hood of retinal breaks is increased. Almost 90% ofeyes with floaters and light flashes are found to haveposterior vitreous detachment, and about 10% haveretinal breaks.

2

Two theories have been devised to explain the lightflashes that may accompany floaters. Moor

11

sug-gested that vitreous traction on the retina at the siteapposing the retinal break precipitates symptoms.Verhoeff,

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on the other hand, postulated that duringocular movement a detached vitreous may collideagainst the retina, and the impact can induce the per-ception of light. Detection of vitreous hemorrhage inthe vitreous gel in association with floaters is highlypredictive of retinal breakage, which is found in 70%of eyes thus affected.

13

�

16

Since bleeding is typicallyseen in eyes with numerous floaters, cascades of nu-merous new-onset floaters is an ominous finding thatshould stimulate an active search for vitreous bleedingand retinal breakage. At the opposite extreme, the de-velopment of a single floater in one eye only is muchless likely to presage significant ocular pathology.

17

Posterior vitreous detachment and floaters are morecommon in older patients, women,

18

and myopic pa-tients.

19,20

Moreover, posterior vitreous detachmentusually demonstrates bilateral symmetry.

21,22

If de-tachment occurs in one eye, the other eye should beexamined promptly if similar symptoms develop in it.In younger patients, blunt trauma that compresses theglobe can prematurely induce floaters and complica-tions. Significant impact trauma is believed necessaryto create floaters, but obviously a patient in his or 30sor 40s who is on the cusp of developing spontaneousfloaters associated with age may require a less intensetraumatic insult. Eye surgery, such as cataract surgery,may also predispose to the formation of floaters.

23

As of 1996, there were 83 cases of retinal laser in-jury reported in the literature.

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Historically lasersused in dermatology have been regarded as relativelysafe for the eyes given the relatively limited depth ofpenetration and the availability and strict use of filter-ing protective eye wear. The relative exception hasbeen the Nd:YAG laser, which penetrates more deeplyinto tissue and has been associated with reports of ret-inal damage resulting in visual field defects. However,there is no mention in the dermatology literature and

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very little in the ophthalmology literature of laser in-duction of floaters prior to retinal injury. Of interest isthat laser-induced floaters are not merely a theoreticalconcern, as there is at least one article describing suchinduction. In ex vivo experiments, Q-switched Nd:YAG laser pulses focused on the vitreous body rapidlycreated large numbers of small cavities that were con-sidered evidence of shock wave propagation withinthe vitreous proteins.

25

It was postulated that such in-jury in the eye of a live patient could induce collapseof the vitreous gel, with resulting floaters and possiblevitreous detachment.

While the bulk of laser eye injuries discussed in themedical literature occurred after direct exposure of thepatient’s retina to laser, indirect injuries have also beenreported to cause significant macular retinal damage.In two cases, graduate students sustained retinal andvitreous hemorrhage with visual loss secondary to eyeinjury by reflected pulsed Nd:YAG beams.

24

Militaryrange finders are similarly known to cause eye injuriesin observers who are hundreds of feet away but inad-vertently look in the direction of the laser.

26

Both Nd:YAG lasers and standard ruby lasers have been impli-cated, and in one study the eyes of anesthetized pigs,placed behind binoculars, developed vitreous hemor-rhages when oriented in the direction of a range finderlaser located 850 m (almost 1 km) away.

27

Intravitrealapplication of Er:YAG laser energy during eye surgeryhas also been associated with vitreous and retinalcomplications.

28

Even in the absence of specific injury,nonspecific heating induced by surgical Er:YAG laserscan alter vitreous conformation.

29

Of interest is that lasers have been used to treat float-ers as well. Precise application of Nd:YAG laser hassuccessfully photodisrupted vitreous opacities withoutrecurrence or complications during a 1-year follow-up.

30,31

Patients obtain symptomatic relief after disap-pearance of the floaters, but visual acuity is neither im-proved nor worsened. Vitrectomy, or surgical removalof the vitreous, can also alleviate symptoms in patientsafflicted with large, visually disabling floaters.

32

The etiology of the floaters reported in this article isunclear. To the extent that both patients developedfloaters within 3 months of beginning work as derma-tologic laser fellows, there is a striking temporal coin-cidence suggestive of causality. In both cases the pa-tients were in specialized practices where they wereexposed to and operated numerous laser devices. Pa-tient 1 clearly recalled a bright, blinding flash over hisslightly askew safety glasses during administration ofPDL treatment for leg veins, and the floaters beganwithin 2 days of this event. While this is circumstan-tial evidence, there are reports of PDL-related retinalinjuries in the literature.

33

Patient 2, who developedfewer floaters, could not localize the precise temporal

onset or provide anecdotal evidence of linkage to aspecific laser. In both cases there was no history ofmyopia, which would be associated with early onsetof spontaneous floaters. Neither patient reported anyeye surgeries or blunt trauma to the head or eyes.

It is thought that a variety of factors may contributeto the risk of subacute eye injury by dermatologic la-sers. Despite their best efforts, physicians may occa-sionally forget to wear safety goggles. Trainees re-cently exposed to laser surgery may be particularlyvulnerable to distractions and oversights. Further-more, new lasers with higher peak fluences, longerpulse durations, and longer wavelengths are believedto permit deeper penetration into tissue; an inducedshock wave could conceivably disrupt the vitreous gelsufficiently to release floaters. Other lasers may alsobe problematic, with the intense pulsed light deviceanecdotally inducing blindingly bright flashes and aresidual perception of brightness for hours in opera-tors despite use of filter eyewear. Similarly the prolif-eration of long-pulsed Nd:YAG lasers has increasedthe attendant increased risk of eye damage becauseoperators may inadvertently gaze into the invisible ac-tive beam when they believe the laser is off. Also, non-ablative resurfacing procedures may not be risk freesince they can last many minutes, may be administeredby medical extenders rather than physicians, and ofteninclude treatment around the orbits. As yet there areno reports of ocular injuries in patients undergoingnonablative resurfacing procedures. Significantly, pa-tients may be better protected by their opaque, closedgoggles than operators are by their transparent safetyglasses.

We propose several steps that may reduce the inci-dence of subacute eye injuries, like floaters, whichmay presage future serious ocular problems. First, anappropriate professional organization, such as theAmerican Society for Laser Medicine and Surgery orthe American Society for Dermatologic Surgery, shoulddevelop a brief course on laser safety for operatorsand patients that novices to the laser field should berequired to take. Second, certain high-risk treatmentpractices should be curtailed or performed with greatcare. For instance, use of long-pulsed Nd:YAG laser totreat periorbital blue reticular veins is a technique sofraught with theoretical ocular risks to the patient thatit may appropriately be performed by only the mostexperienced practitioners. Finally, more research andexperience is needed to confirm that current eye safetypractices are truly protective under real-world condi-tions. Laser surgeons should be consulted by eyewearmanufacturers so that the laboratory testing of laserglasses and goggles closely approximates the functionsthey will be required to perform in physicians’ of-fices.

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Testing should be at the higher fluences and

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longer treatment durations that are now the norm inmany practices.

Dermatologic lasers are, on balance, extremely safedevices. There are few reports of serious injuries. La-ser manufacturers continue to improve product safetyand reliability, and most laser surgeons are compliantwith eye safety guidelines. However, the purpose ofthis article is to be a cautionary tale. That few laseroperators have visual field losses does not mean thatnumerous, troublesome subacute ocular injuries arenot being sustained that may increase the future riskof serious retinal problems. In addition, the prolifera-tion of newer, more powerful lasers, and their opera-tion by less qualified personnel, suggest that we can-not relax our vigilance regarding eye safety.

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