Retinal Imaging On the Cheap

If your practice&#;s technology budget is tapped out but you find yourself in need of a portable retinal imager to use for hospital rounds, nursing home visits or pediatric patients, you&#;re in luck: There are a couple of new adapters and apps that allow you to document retinal findings for under $500. Here&#;s a look at how these devices work, as well as their benefits and limitations.

D-Eye

If you are looking for more details, kindly visit weiqing.

The D-Eye Portable Retinal Imaging System (D-Eye, Padova, Italy) is a lens assembly that magnetically attaches to a late-model Apple iPhone or Samsung Galaxy.

Andrea Russo, MD, a practicing ophthalmologist and PhD candidate at Italy&#;s University of Brescia, invented the D-Eye. &#;About 20 years ago, they joined digital cameras with PCs in order to record the view of the retina in our offices,&#; Dr. Russo says. &#;Now, we have the smartphone, which is a computer in your pocket. When I finished my residency program, I decided to use a few lenses to create the D-Eye project. Essentially, the D-Eye is a direct ophthalmoscope for viewing the retina using just a smartphone held close to the patient&#;s eye.&#;

A collage of retinal images captured with the new D-Eye system. (

Image courtesy Andrea Russo, MD.

) The D-Eye uses a -10-D lens to compensate for any myopia a patient may have. The other components are a beam splitter and a mirror. &#;The mirror is used to reflect the light coming from the LED inside the smartphone and the beam splitter is for conveying the light into the patient&#;s eye,&#; Dr. Russo explains. &#;We also use a couple of polarizing filters that are important for reducing the glare from the cornea, or the Purkinje reflection. For a hyperopic patient, we use the camera&#;s internal autofocus system to compensate for the hyperopia.&#; Since a smartphone&#;s LED can be irritating to patients when held close to the eye, the D-Eye also has a diaphragm that dims the light, making it more tolerable. Dr. Russo says even babies are not bothered by the illumination.

In practice, Dr. Russo says the field of view is limited. &#;It&#;s around 5 to 8 degrees with an undilated pupil, and 20 to 25 degrees with dilation,&#; he says. &#;This is because direct ophthalmoscopy is similar to looking through a keyhole, and the wider the keyhole, the wider the field of view. It really depends on the pupil&#;s dimensions.

&#;You can record still images or videos with it,&#; Dr. Russo continues, &#;but I suggest recording video, since you have a limited field of view. In video mode, you can pan around the retina, from the fovea to the optic disk, then out to the equator, to catch all the details. Otherwise, if you only use still images, you could lose a few parts of the retina. You can&#;t go farther than the equator, but you can reach it as you can with an ordinary direct ophthalmoscope.&#;

Dr. Russo says that, though the device is useful, it&#;s not a substitute for a traditional retinal camera and direct ophthalmoscopy. &#;The traditional system is the next level,&#; he says. &#;The D-Eye system is in the middle between direct ophthalmoscopy and high-end, expensive cameras. This isn&#;t intended to be a substitute for traditional equipment, but instead to help with exams in specific cases, such as bedridden patients, patients in rural areas and babies. In terms of conditions, it&#;s good for glaucoma screening because the optic nerve is easy to view. For diabetic retinopathy, you can assess the retina out to the periphery and notice signs of diabetic retinopathy. We actually published a paper this year that described the agreement between the D-Eye system and the ordinary slit-lamp exam in diabetic retinopathy that found that the agreement was pretty good.&#;1

Future plans for the device are aimed at overcoming the current version&#;s limitations. &#;We&#;re developing a D-Eye 2.0 with a much wider field of view,&#; Dr. Russo explains. &#;Since, as I said earlier, direct ophthalmoscopy is like looking through a keyhole, the closer you get to the keyhole, the wider the field of view, so the solution is to make the D-Eye slimmer. This one is about 1 cm, and the 2.0 will be 0.5 cm.&#;

The D-Eye costs $390. Also, when a new version comes out, Dr. Russo says all the user will need to purchase is the housing that attaches to the , not an entirely new D-Eye lens system. For information, visit

OphthalmicDocs Fundus

The OphthalmicDocs Fundus is born out of the open-source movement in software, which allows users to take a product, in this case an adapter for a smartphone, and modify it in ways they see fit. As such, the OphthalmicDocs adapter isn&#;t something you buy; instead it&#;s a file you can download and send to a 3D printer, creating it yourself for the cost of the printing and materials. You add a condensing lens and then attach the device to your smartphone.

The idea for the device came from Hong Sheng Chiong, MD, an ophthalmology registrar (similar to a resident in the United States) at Gisborne Hospital in New Zealand. At first, his idea was limited to drawings on paper, but when he co-founded OphthalmicDocs he teamed up with product designers and engineers, and the device began taking shape.

The OphthalmicDocs Fundus is inexpensive because you make it on a 3D printer. (

Image courtesy Hong Sheng Chiong, MD.

) The OphthalmicDocs Fundus adapter is basically a bracket that fits on a smartphone. The bracket has an arm that extends outward from the and ends in a housing that holds the condensing lens in front of the &#;s camera. &#;For now the adapter is designed to hold a 28-D or a 20-D lens,&#; explains Dr. Chiong. &#;The 28-D lens is for pediatric cases or infants, and the 20-D lens is mainly for adults. With dilation, the field of view is up to 40 degrees. If the user has a modern smartphone, such as a Samsung Galaxy or an iPhone, its autofocus is used to compensate for a patient&#;s refractive error, up to 5 D of myopia or hyperopia. As for getting good images, we usually recommend using a smartphone that has at least a 5-megapixel camera. We&#;ve tried it on older generation phones with 3.2 or 3.8 megapixels, and found that though you would get a picture of the retina, it wouldn&#;t be of good enough quality to tell if the image is drusen or exudate, or if it&#;s a bleed or pigment.&#; The working distance is between 5 and 7 cm away from the patient&#;s eye.

&#;We&#;ve been mainly using it locally in our hospital for patients who present to the emergency department, those too sick to be sent down to the eye clinic, and for neonatal examinations,&#; says Dr. Chiong. &#;Because we&#;re on the east coast of New Zealand, it&#;s an outreach area, and we have small villages of 500 to 1,000 people who live two hours away from the nearest health-care center. In that type of situation, it&#;s useful for screenings for patients who require a retinal exam. It&#;s also handy in an outreach environment because a conventional fundus camera would be too heavy and bulky to move around, and could be damaged by the rough road conditions.&#;

Dr. Chiong says that, though the adapter is useful in certain situations, it has some limitations, as well. &#;The strength of the system is that it&#;s portable,&#; he says. &#;But, like any portable, handheld device, if you try to take a video and there&#;s movement, it will degrade the image quality. The best way to get a good image is to have the patient sit down, and then stabilize the patient&#;s head with one hand while holding the smartphone with the other.

&#;The pupil size is a huge factor in getting images with the current version of the device,&#; Dr. Chiong continues. &#;Cases that are challenging for the retinal adapter are patients that don&#;t have a pupil that&#;s easily dilatable. It&#;s challenging in floppy-iris syndrome, for example. Also, like any other fundus camera, it doesn&#;t give you a 3D perception of a lesion, just 2D, so you can&#;t be sure if it&#;s elevated or not.&#;

Future plans center on making the system non-mydriatic. &#;We&#;re working on a non-mydriatic adapter with a wider field of view,&#; says Dr. Chiong. &#;You could actually have up to a 50-degree field of view by incorporating a small, powerful lens after the objective lens and using an infrared light source to get focus to prevent pupillary constrictions.&#;

The 3D printer file can be downloaded at ophthalmicdocs-fundus.org, along with instructions on assembly. If you don&#;t have access to a 3D printer, you can find one near you by visiting

PEEK Retina

A smartphone solution for retinal imaging that&#;s being used for research outside of the United States is the Portable Eye Examination Kit Retina.

PEEK Retina consists of an adaptor that slides over the top portion of a smartphone, interfacing with the &#;s camera, and a software application for focusing the retinal image and organizing the videos and images that the camera captures.
The PEEK system has been used for retinal screening in low-income communities in Kenya, for diabetic retinopathy detection in Botswana and for screening patients for possible malarial retinopathy in Mali. PEEK&#;s designers are also working on incorporating eye tests into the system to allow physicians in the field to perform quick eye exams to get a baseline for a patient&#;s acuity. In the future, PEEK will also have color testing to screen for color-blindness and contrast sensitivity testing.

In terms of availability, it looks like PEEK will arrive in Europe first. &#;We are currently in the manufacturing stage, and aim to have the PEEK Retina adapter available in early ,&#; explains PEEK&#;s Sarah O&#;Regan. &#;We should be able to ship it within the European Union&#;and to non-governmental organizations within the EU who will be responsible for export. We hope to be able to ship to as many countries as possible, and are working with a regulatory consultant on this. We&#;re currently unable to ship PEEK Retina to addresses in the United States until FDA approval has been granted, but we are working on this.&#; For more information or to possibly get involved with PEEK research, visit peekvision.org.  

REVIEW
&#;

Dr. Russo sold the patent for the D-Eye and is an adviser to the company. Dr. Chiong is co-founder of the charitable trust OphthalmicDocs, which doesn&#;t charge for the adapter or app.



1. Russo A, Morescalchi F, Costagliola C, Delcassi L, Semeraro F. Comparison of smartphone ophthalmoscopy with slit-lamp biomicroscopy for grading diabetic retinopathy. Am J Ophthalmol ;159:2:360-4.

technology budget is tapped out but you find yourself in need of a portable retinal imager to use for hospital rounds, nursing home visits or pediatric patients, you&#;re in luck: There are a couple of new adapters and apps that allow you to document retinal findings for under $500. Here&#;s a look at how these devices work, as well as their benefits and limitations.The D-Eye Portable Retinal Imaging System (D-Eye, Padova, Italy) is a lens assembly that magnetically attaches to a late-model Apple iPhone or Samsung Galaxy.Andrea Russo, MD, a practicing ophthalmologist and PhD candidate at Italy&#;s University of Brescia, invented the D-Eye. &#;About 20 years ago, they joined digital cameras with PCs in order to record the view of the retina in our offices,&#; Dr. Russo says. &#;Now, we have the smartphone, which is a computer in your pocket. When I finished my residency program, I decided to use a few lenses to create the D-Eye project. Essentially, the D-Eye is a direct ophthalmoscope for viewing the retina using just a smartphone held close to the patient&#;s eye.&#;The D-Eye uses a -10-D lens to compensate for any myopia a patient may have. The other components are a beam splitter and a mirror. &#;The mirror is used to reflect the light coming from the LED inside the smartphone and the beam splitter is for conveying the light into the patient&#;s eye,&#; Dr. Russo explains. &#;We also use a couple of polarizing filters that are important for reducing the glare from the cornea, or the Purkinje reflection. For a hyperopic patient, we use the camera&#;s internal autofocus system to compensate for the hyperopia.&#; Since a smartphone&#;s LED can be irritating to patients when held close to the eye, the D-Eye also has a diaphragm that dims the light, making it more tolerable. Dr. Russo says even babies are not bothered by the illumination.In practice, Dr. Russo says the field of view is limited. &#;It&#;s around 5 to 8 degrees with an undilated pupil, and 20 to 25 degrees with dilation,&#; he says. &#;This is because direct ophthalmoscopy is similar to looking through a keyhole, and the wider the keyhole, the wider the field of view. It really depends on the pupil&#;s dimensions.&#;You can record still images or videos with it,&#; Dr. Russo continues, &#;but I suggest recording video, since you have a limited field of view. In video mode, you can pan around the retina, from the fovea to the optic disk, then out to the equator, to catch all the details. Otherwise, if you only use still images, you could lose a few parts of the retina. You can&#;t go farther than the equator, but you can reach it as you can with an ordinary direct ophthalmoscope.&#;Dr. Russo says that, though the device is useful, it&#;s not a substitute for a traditional retinal camera and direct ophthalmoscopy. &#;The traditional system is the next level,&#; he says. &#;The D-Eye system is in the middle between direct ophthalmoscopy and high-end, expensive cameras. This isn&#;t intended to be a substitute for traditional equipment, but instead to help with exams in specific cases, such as bedridden patients, patients in rural areas and babies. In terms of conditions, it&#;s good for glaucoma screening because the optic nerve is easy to view. For diabetic retinopathy, you can assess the retina out to the periphery and notice signs of diabetic retinopathy. We actually published a paper this year that described the agreement between the D-Eye system and the ordinary slit-lamp exam in diabetic retinopathy that found that the agreement was pretty good.&#;1Future plans for the device are aimed at overcoming the current version&#;s limitations. &#;We&#;re developing a D-Eye 2.0 with a much wider field of view,&#; Dr. Russo explains. &#;Since, as I said earlier, direct ophthalmoscopy is like looking through a keyhole, the closer you get to the keyhole, the wider the field of view, so the solution is to make the D-Eye slimmer. This one is about 1 cm, and the 2.0 will be 0.5 cm.&#;The D-Eye costs $390. Also, when a new version comes out, Dr. Russo says all the user will need to purchase is the housing that attaches to the , not an entirely new D-Eye lens system. For information, visit d-eyecare.com The OphthalmicDocs Fundus is born out of the open-source movement in software, which allows users to take a product, in this case an adapter for a smartphone, and modify it in ways they see fit. As such, the OphthalmicDocs adapter isn&#;t something you buy; instead it&#;s a file you can download and send to a 3D printer, creating it yourself for the cost of the printing and materials. You add a condensing lens and then attach the device to your smartphone.The idea for the device came from Hong Sheng Chiong, MD, an ophthalmology registrar (similar to a resident in the United States) at Gisborne Hospital in New Zealand. At first, his idea was limited to drawings on paper, but when he co-founded OphthalmicDocs he teamed up with product designers and engineers, and the device began taking shape.The OphthalmicDocs Fundus adapter is basically a bracket that fits on a smartphone. The bracket has an arm that extends outward from the and ends in a housing that holds the condensing lens in front of the &#;s camera. &#;For now the adapter is designed to hold a 28-D or a 20-D lens,&#; explains Dr. Chiong. &#;The 28-D lens is for pediatric cases or infants, and the 20-D lens is mainly for adults. With dilation, the field of view is up to 40 degrees. If the user has a modern smartphone, such as a Samsung Galaxy or an iPhone, its autofocus is used to compensate for a patient&#;s refractive error, up to 5 D of myopia or hyperopia. As for getting good images, we usually recommend using a smartphone that has at least a 5-megapixel camera. We&#;ve tried it on older generation phones with 3.2 or 3.8 megapixels, and found that though you would get a picture of the retina, it wouldn&#;t be of good enough quality to tell if the image is drusen or exudate, or if it&#;s a bleed or pigment.&#; The working distance is between 5 and 7 cm away from the patient&#;s eye.&#;We&#;ve been mainly using it locally in our hospital for patients who present to the emergency department, those too sick to be sent down to the eye clinic, and for neonatal examinations,&#; says Dr. Chiong. &#;Because we&#;re on the east coast of New Zealand, it&#;s an outreach area, and we have small villages of 500 to 1,000 people who live two hours away from the nearest health-care center. In that type of situation, it&#;s useful for screenings for patients who require a retinal exam. It&#;s also handy in an outreach environment because a conventional fundus camera would be too heavy and bulky to move around, and could be damaged by the rough road conditions.&#;Dr. Chiong says that, though the adapter is useful in certain situations, it has some limitations, as well. &#;The strength of the system is that it&#;s portable,&#; he says. &#;But, like any portable, handheld device, if you try to take a video and there&#;s movement, it will degrade the image quality. The best way to get a good image is to have the patient sit down, and then stabilize the patient&#;s head with one hand while holding the smartphone with the other.&#;The pupil size is a huge factor in getting images with the current version of the device,&#; Dr. Chiong continues. &#;Cases that are challenging for the retinal adapter are patients that don&#;t have a pupil that&#;s easily dilatable. It&#;s challenging in floppy-iris syndrome, for example. Also, like any other fundus camera, it doesn&#;t give you a 3D perception of a lesion, just 2D, so you can&#;t be sure if it&#;s elevated or not.&#;Future plans center on making the system non-mydriatic. &#;We&#;re working on a non-mydriatic adapter with a wider field of view,&#; says Dr. Chiong. &#;You could actually have up to a 50-degree field of view by incorporating a small, powerful lens after the objective lens and using an infrared light source to get focus to prevent pupillary constrictions.&#;The 3D printer file can be downloaded at ophthalmicdocs-fundus.org, along with instructions on assembly. If you don&#;t have access to a 3D printer, you can find one near you by visiting 3Dhubs.com A smartphone solution for retinal imaging that&#;s being used for research outside of the United States is the Portable Eye Examination Kit Retina.PEEK Retina consists of an adaptor that slides over the top portion of a smartphone, interfacing with the &#;s camera, and a software application for focusing the retinal image and organizing the videos and images that the camera captures.The PEEK system has been used for retinal screening in low-income communities in Kenya, for diabetic retinopathy detection in Botswana and for screening patients for possible malarial retinopathy in Mali. PEEK&#;s designers are also working on incorporating eye tests into the system to allow physicians in the field to perform quick eye exams to get a baseline for a patient&#;s acuity. In the future, PEEK will also have color testing to screen for color-blindness and contrast sensitivity testing.In terms of availability, it looks like PEEK will arrive in Europe first. &#;We are currently in the manufacturing stage, and aim to have the PEEK Retina adapter available in early ,&#; explains PEEK&#;s Sarah O&#;Regan. &#;We should be able to ship it within the European Union&#;and to non-governmental organizations within the EU who will be responsible for export. We hope to be able to ship to as many countries as possible, and are working with a regulatory consultant on this. We&#;re currently unable to ship PEEK Retina to addresses in the United States until FDA approval has been granted, but we are working on this.&#; For more information or to possibly get involved with PEEK research, visit peekvision.org.Dr. Russo sold the patent for the D-Eye and is an adviser to the company. Dr. Chiong is co-founder of the charitable trust OphthalmicDocs, which doesn&#;t charge for the adapter or app.

Abstract

  Accidental retinal laser injuries are easily diagnosed when there areknown laser sources, typical macular injuries, and visual deficits consistentwith retinal findings. Decisions are more difficult when retinal findingsare subtle or absent, despite reported visual problems and somatic complaints.Inaccurate diagnosis of an ocular laser injury can precipitate a costly, lengthysequence of medical and legal problems. Analysis of laser-tissue interactionsand the characteristics of unambiguous retinal laser injuries provide 6 keyquestions to facilitate difficult diagnoses. Case reports demonstrate theusefulness of answering these questions before making diagnostic decisions.Retinal laser lesions that cause serious visual problems are readily apparentophthalmoscopically and angiographically. Accidental, intentional, or clinicalretinal laser lesions do not cause chronic eye, face, or head pains. Diagnosisof a retinal laser injury should be evidence based, not a matter of conjectureor speculation.

It is well understood that accidental momentary exposure to an ordinaryflashlight beam is annoying but safe. Accidental momentary exposure to a low-powerlaser pointer beam is also annoying but safe, yet it can evoke fear or outragein some people.1-5 Untowardresponses to real or imagined laser exposures can have complex social andpsychiatric explanations or more practical fiscal motivations. Ophthalmologistsmay be called on to determine whether a retinal laser injury is responsiblefor symptoms that reportedly follow an actual or perceived laser exposureincident. The proper analysis of those situations requires a clear understandingof the organic and psychophysical consequences of actual laser injuries, particularlywhen real but unrelated ophthalmic and systemic problems are present to confoundthe analysis.

Laser effects

Exposure to UV radiation (200-400 nm), visible light (400-700 nm), andinfrared radiation (700-10 000 nm) can damage the eye.6-9 Transmissionand absorption of optical radiation by ocular media depend on the wavelengthof the incident UV radiation, visible light, or infrared radiation.10 Wavelength, pulse duration, spot size, and irradiance(power density, or laser power divided by area) determine the magnitude andlateral extent of temperature rises in exposed tissue produced by incidentlaser beams.11,12 Cornea and lensrefraction produce retinal irradiances for laser beams that are up to 105 times greater than their corneal irradiances.13 Laserradiation can damage the eye by photomechanical, photothermal, or photochemicalmechanisms.8,9,14-16 Itis useful to differentiate between these mechanisms, but more than one effectmay be involved in any particular injury.

Photomechanical injuries are caused by extremely high laser irradiancesin very brief laser exposures ranging from hundreds of femtoseconds (10&#; 15 seconds) to microseconds (10&#; 6 seconds).Tissue is fragmented, perforated, or distorted immediately by a photomechanicalinjury.Clinical examples include photodisruption in Nd:YAGlaser capsulotomy, photoablation in excimer laser keratorefractive surgery,and photovaporization in holmium:YAG laser thermokeratoplasty for hyperopia.Powerful Q-switched industrial or military lasers can cause severeretinal injuries when their radiation is absorbed in the retinal pigment epithelium(RPE) and underlying choroid.17-23 Intypical, accidental retinal injuries, rapid tissue expansion causes hemorrhageand prominent, permanent retinal scars.

Thermal laser injuries are produced by high laser irradiances in briefexposures ranging from microseconds to several seconds. Tissue protein coagulationoften causes immediate or delayed blanching of the laser impact site and adjacenttissue. Clinical examples include argon laser panretinal photocoagulationand trabeculoplasty. Barely visible retinal photocoagulation lesions are associatedwith retinal temperature increases of 10°C.12,24-28 Typicalclinical photocoagulation lesions are associated with much higher retinaltemperature increases (40°C-60°C).12,24,27,28 Accidentalcornea, iris, and crystalline lens injuries have been reported in clinicalphotocoagulation.29-34 Accidentalretinal laser lesions that produce substantial vision loss are apparent ophthalmoscopicallyor angiographically.17-23

Photochemical injuries occur when prolonged optical radiation exposurecauses phototoxic chemical reactions in affected tissues8,16,35-37 orwhen a previously administered exogenous photosensitizer is activated by anappropriate light source.38 Clinical examplesinclude solar and operating microscope maculopathy and verteporfin photodynamictherapy for age-related macular degeneration. Viewing intense light is veryuncomfortable. Natural protective responses, such as squinting, pupillaryconstriction, and looking away from uncomfortably brilliant light sources,protect people from phototoxic retinal injuries, except in highly unusual,prolonged viewing circumstances, such as unprotected solar eclipse observationor welding arc viewing with a defective protective filter.6,9,39

Accidents

It is estimated that fewer than 15 retinal injuriesworldwide each year are caused by industrial and military lasers.17,22,40-44 Inmost actual laser eye injuries, the laser source is known, typical chorioretinaldamage occurs, there is an unambiguous temporal relationship between a laserincident and the onset of visual abnormalities that are well correlated withretinal findingsand retinal abnormalities remodel after the incidentin a manner commensurate with their severity.

Laser eye injuries can be prevented by appropriate laser safety eyewearuse. Unfortunately, laser safety glasses or goggles partially restrict vision,interfering with visually demanding laboratory, industrial, or military tasks.In addition, laser safety goggles can be uncomfortable and can fog in hotand humid environments. Most industrial accidents occur when a misfired laserbeam enters an unshielded bystander's eye. Military injuries typically occurwhen a laser rangefinder or target designator beam is inadvertently or inappropriatelyviewed by an unprotected user or onlooker (Figure 1 and Figure 2).46,47 An ordinary laser pointer is safe,unless a user chooses to stare at its uncomfortable brilliant light for morethan 10 seconds at close range, despite eye hazard labels warning users toavoid eye exposure.1-5 Anteriorsegment eye injuries from lasers are rare because UV and infrared lasers thatproduce radiation with considerable corneal or crystalline lens absorptionare typically used in well-controlled medical or industrial devices or environments.Most ocular laser accidents are caused by powerful Q-switched lasers thatproduce serious retinal injuries.19,20,22,42

Symptoms and findings

The severity of initial vision loss after a retinal laser injury dependson the distance of the laser impact site from the center of the fovea, theextent of chorioretinal disruption, and the amount of chorioretinal bleeding.Victims of visually significant retinal laser injuries typically experiencesudden, severe decreased vision in one or, less commonly, both eyes. Theyusually notice a bright flash of light even with invisible laser beams, followedby an immediate decrease in the vision of affected eyes. They occasionallyhear a loud popping sound during a Q-switched chorioretinal laser injury.Vision may improve over several days to months. Visual prognosis is excellentif retinal findings are minor or do not involve the fovea. If the resultsof Amsler grid testing are abnormal, findings stabilize within a few months.These findings are consistent, stable, and well correlated with retinal findingsin cooperative patients.

Momentary pain may occur at the time of ocular laser injury, but onlyrarely. This pain does not persist, just as it does not persist after clinicalretinal photocoagulation. Noninjurious laser exposures and most laser injuriesare painless, but rubbing an eye after a laser exposure can cause a painfultransient corneal abrasion that individuals may attribute to laser exposure.Self-inflicted corneal abrasions are responsible for reported painful visionlosses in children after laser pointer exposures.5

The most common initial clinical finding after an industrialor military Q-switched laser injury is prominent vitreous and/or chorioretinalhemorrhage from blood vessels ruptured by tissue distortion (Figure 2).17,20-22,40 Thenumber and size of blood vessels damaged at the laser impact site determinethe extent of initial hemorrhage.23 The locationof the vessels and the structural integrity of adjacent tissue determine howeffectively blood is tamponaded locally.23 Largeretinal areas can be rendered dysfunctional if blood spreads laterally intosubhyaloid, subretinal, or sub-RPE spaces. Persistence of hemorrhage intosubretinal spaces can cause photoreceptor deterioration.48 Retinalholes and scarring can occur at the impact site (Figure 1 and Figure 2).17,20-22,40

Fundus photography, fluorescein angiography, and opticalcoherence tomography are invaluable for determining whether retinal injuryis present after a laser incident and, if so, whether visual complaintsare consistent with documented retinal abnormalities. Acute photomechanicalinjuries typically produce a hypofluorescent spot at the laser impact sitecaused by vitreous or associated chorioretinal hemorrhage. As the hemorrhageresolves, a hyperfluorescent window defect may develop at the site owing toRPE damage (Figure 2), with hyperfluorescentstaining of any fibrosis that develops after the injury. An RPE discontinuityor elevation is commonly seen on optical coherence tomograms immediately afterand subsequent to photomechanical injuries (Figure 2). Acute photocoagulation lesions typically have a hypofluorescentcenter with a surrounding ring of faint hyperfluorescence. If a photocoagulationlesion is sufficiently small, there may be only a tiny hyperfluorescent spotat the injury site. Fluorescein leakage in the form of staining or poolingof dye at photocoagulation sites in late angiogram frames is common immediatelyafter an injury. Acute photochemical lesions may have no angiographic abnormalities(as in mild solar maculopathy) or early hyperfluorescence with late leakage(as in operating microscope injuries).9 Visuallysignificant phototoxic lesions eventually produce angiographically apparentRPE abnormalities.

Retinal photography and fluorescein angiography should be performedas soon as possible after a suspected laser injury because there may be subvisiblelesions if laser exposure variables are below thresholds for ophthalmoscopicallyapparent lesions. These tests are also important for dating chorioretinalfindings and for determining whether concurrent systemic disease rather thanlaser injury could be their cause. Indocyanine green angiography may alsobe useful, particularly if it is performed using scanning laser ophthalmoscopy.

If there is no vitreous and/or chorioretinal hemorrhage to obscure thesite, an acute laser injury is likely to produce a lesion with some fluoresceinpooling or staining, whereas an ordinary window defect on an angiogram performedwithin a week of a laser incident is more likely to be due to previous trauma,inflammation, or other natural processes. The possibility of preexisting orconcurrent eye or systemic problems makes it important to obtain a completemedical history and review of systems in cases of possible retinal laser injury,in addition to carefully reviewing copies of past medical records and retinalimaging if available.

Incidental angiographic findings should not be overinterpreted.For example, tiny RPE window defects occur routinely in angiograms with normalfindings. In a small series of 50 consecutive fluorescein angiograms reviewedby one of us (M.A.M.), two thirds of the contralateral normal eyes of individualswith unilateral retinal problems had 1 or more tiny RPE window defects. TheRPE is its own record of a lifetime of infection, trauma, inflammation, andother natural events. A few scattered RPE imperfections are neither surprisingnor conclusively diagnostic of laser injury.

Diagnosis

The diagnosis of a laser injury can have considerable legal, financial,and medical consequences. It should be based on objective medical evidencerather than on unscientific speculation. Medicolegal problems arise when aninjury is alleged but objective findings are absent, within normal limits,or explainable by unrelated medical problems. The ease of diagnosing an actuallaser injury is directly proportional to its severity. The answers to 6 facilitatingquestions are useful for diagnosing less severe or absent injuries after areal or imagined laser accident (Table 1). If the answer to question 1 is "no," then no visually significantlaser injury has occurred. If the answers to all 6 questions are "yes," thena laser injury has almost certainly occurred.

Proper evaluation of a laser injury demands an exhaustive review ofsystems and medical history to rule out ocular or systemic causes for theophthalmic and somatic complaints ascribed to a purported laser exposure.In suggestible or otherwise susceptible individuals, pain can represent anindividual's somatization of a perceived although not organic ocular injury.Differentiating the psychiatric, financial, or other origins of nonorganicdisorders is a challenging problem,49-60 butperceived ocular injuries with no demonstrable tissue damage are not reallaser injuries.

Case reports

Case 1

History

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An 11-year-old girl stared at a red laser pointer beam held close toher right eye for more than 10 seconds to satisfy the curiosity of classmateson a school bus who wanted to know if her pupil would constrict.61 Sheexperienced no pain but developed decreased vision and a central scotoma immediatelyin her right eye. Three weeks later, a retinal evaluation revealed centralfoveal pigment mottling with corresponding faint hyperfluorescence on fluoresceinangiography. These findings became less prominent during the next 3 monthsas her scotoma resolved, and her uncorrected visual acuity returned to 20/25OD, the same as in her unaffected left eye. She had no other ocular abnormalitiesin her right eye. In addition, this patient had no recent history of infection,inflammation, or mechanical trauma and no contributory past systemic or ocularhistory.

Analysis

This 11-year-old girl probably experienced a 5-mW, 10-second, 50-µmretinal spot diameter exposure that produced a 6° to 10° retinal temperaturerise with a retinal irradiance of 160 W/cm2 of diode 635-nm redlight.5,62 In comparison, clinicalphotocoagulation for diabetic retinopathy can be performed with a 200-mW,0.2-second, 200-µm retinal spot diameter exposure that produces a 40°to 60° retinal temperature rise with a retinal irradiance of 325 W/cm2 of argon laser 514-nm green radiation.62 Subvisiblelesion transpupillary thermotherapy for occult choroidal neovascularizationin age-related macular degeneration can be performed with an 800-mW, 60-second,3-mm retinal spot diameter exposure that produces a 10° retinal temperaturerise with a retinal irradiance of 7.5 W/cm2 of diode laser 810-nminfrared radiation.62

Laser pointers sold in the United States are required to have an outputpower less than 5 mW.1,2,5,63 Accidentalmomentary laser pointer exposure is safe because it is terminated in lessthan 0.25 second by normal aversion responses to uncomfortably brilliant light.1,2,5,64,65 Prolongedviewing of a laser pointer beam for more than 10 seconds is potentially harmful,1 which is the reason that these devices have warninglabels. Retinal irradiance produced by a laser pointer held close to the eyeis high because much of its power enters the eye and is concentrated intoa small retinal spot. Conversely, heat conduction cools small retinal spotsmore effectively than large ones, so retinal temperature rises for small-spot,10-second laser pointer and large-spot, 60-second transpupillary thermotherapyexposures are comparable.11,24,62 Thus,the most likely mechanism for the documented retinal damage caused by thislaser pointer exposure is threshold transpupillary thermotherapy&#;typephotocoagulation. In this case, the answers to all 6 diagnostic questionsgiven in Table 1 are "yes,"and this episode is a case of laser injury.

Case 2

History

A prankster with a laser pointer momentarily exposed a middle-aged workerto the beam of an ordinary laser pointer from a distance of 9 m. The worker'svisual acuity after the incident was 20/20 OU. In the 4 years after the episode,the worker developed headaches, progressive photophobia, and severe sharpand longer-lasting dull eye pains. His photophobia was disabling even whenwearing sunglasses at ordinary indoor illumination levels. Visual field testsinitially documented unilateral hemianopsia, although findings from magneticresonance imaging were normal. Fluorescein angiography and eye examinationsby numerous ophthalmologists immediately after and subsequent to the episodedid not identify organic disease other than dry eye syndrome. The worker wasthen seen by a neuro-ophthalmologist, who diagnosed him as having photo-oculodyniasyndrome66 and attributed the origin of hispain, photophobia, and headaches to previous laser pointer exposure. The prankster'sfoolishness, the neuro-ophthalmologist's speculation that momentary laserpointer exposure can cause photo-oculodynia syndrome, and the worker's excellentemployment record and reported absence of health or occupational problemsbefore the incident probably influenced the defendant to settle this worker'sdamage claims out of court.

Analysis

Laser pointers are poor optical devices that contain a simple, inexpensivelens that collimates its diode laser's divergent, astigmatic beam. Assumingthat a laser pointer beam has a full 5-mW output and a standard beam divergenceof 1.5 milliradian, only 7% of the laser beam would enter a 4-mm-diameterpupil at a distance of 9 m. This exposure would produce a physiologic retinaltemperature rise of only 0.4°C, which could not cause retinal injury.Furthermore, at a distance of 9 m from an artificial pupil, a laser pointercan be aimed through a 7-mm aperture at best only 25% of the time (B.E.S.,D. J. Lund, BS, H. Zwick, PhD, D. A. Stamper, MS, P. R. Edsall, BS, J. W.Molchany, BS, unpublished data, ). Normal head movements and hand movementsreduce any retinal exposure even more, so a laser pointer injury from a distanceof 9 m is impossible without pupillary dilation and mechanically restrainingand aligning both the laser pointer aperture and the observer's pupil formore than 10 seconds.

We could find only a single article66 inthe medical literature on photo-oculodynia syndrome, which is described as"a category of chronic eye pain triggered by even minor ocular trauma, whenthere is no evidence of ongoing tissue damage or inflammation." The term wasproposed as an alternative to the standard term "photophobia."66 Only6 individuals with this condition were described in the article,66 3of whom reported less discomfort after cervical sympathetic ganglion block.There is no scientific basis for the neuro-ophthalmologist's speculation thata complex ocular pain syndrome could be induced by brief, nondamaging lightexposure. If that were the case, there would be millions of people with photo-oculodyniasyndrome due to flash photography and laser eye surgery. In this case, theanswers to diagnostic questions 1 and 6 in the Table 1 are "no," and this episode is not a case of laser injury.

Case 3

History

A young male soldier viewing the exit aperture of a laser rangefinderthat he was holding accidentally exposed his right eye to several powerfulQ-switched, -nm laser pulses.20 He reportedno pain but noticed an immediate decrease in vision in his right eye. Ophthalmicexamination 24 hours later revealed vitreous hemorrhage overlying 2 retinalholes in his right fovea. Fluorescein angiography 5 days after the incidentdocumented 3 prominent chorioretinal lesions with surrounding hyperfluorescence.Central macular scarring progressed in his right eye, and his visual acuity18 months after the laser exposure was 20/400 OD.

Analysis

Military Q-switched laser rangefinders and target designators are hazardousdevices with radiation outputs that far exceed maximum permissible exposurelevels.20,44,63 Injuriesto users and bystanders continue to occur infrequently despite careful precautionsand safety training. In this case, the answers to all 6 diagnostic questionsin the Table 1 are "yes," andthis episode is a case of laser injury.

Case 4

History

A 40-year-old male soldier observed 3 red light pulses emitted in 3seconds by a tank approximately 3 km from his helicopter. He reported oculardiscomfort for approximately an hour after the mission. These symptoms wererelieved by acetaminophen use and did not recur. His visual acuity was 20/20OU after the incident and when tested several times during the next 5 years.The soldier experienced metamorphopsia 7 years after the episode. He soughtmedical care 2 years later, concerned that he might be going blind from alaser exposure. When examined at that time, his uncorrected visual acuitywas 20/20 OD and 20/50 OS, improvable to 20/20 OS, where his responses wereslower. Findings from anterior segment examination were normal, but therewere numerous yellow flecks in each macula, approximately 50 to 100 µmin longest lateral extent. A foveal fleck was present in both eyes. Earlyfluorescein angiogram frames documented that the flecks had central hypofluorescencewith a surrounding zone of hyperfluorescence. The hyperfluorescence fadedin later images.

Analysis

The soldier did not undergo a thorough retinal examination or retinalimaging studies until 9 years after the tank observation incident. At thattime, ophthalmoscopy and fluorescein angiography documented pattern RPE dystrophy.67-69 We know of no scientificevidence to suggest that this problem is caused or accelerated by light exposure.The tank that the soldier observed was probably equipped with a Q-switchedruby laser (694.3-nm, red) rangefinder. Q-switched retinal laser injuriestypically cause immediate vision loss and a prominent, permanent chorioretinalscar. The soldier did not have vision loss after the incident or a chorioretinalscar consistent with laser injury. Furthermore, the type of ruby laser rangefinderknown to be on the kind of tank he observed produces a retinal exposure farbelow international safety standards at a 3-km viewing distance.63,70 Inthis case, the answers to questions 1 and 6 in the Table 1 are "no," and this episode is not a case of laser injury.

Case 5

History

A middle-aged photographer had pain from a corneal abrasion after takingphotographs of a ship. He surmised that there had been a laser device on theship and that a laser injury had caused his discomfort. His visual acuitywas 20/20 OU after the episode. A retina specialist found 3 tiny (10- to 20-µm)RPE window defects in one eye on a fluorescein angiogram and ascribed themto laser injury. Findings from optical coherence tomography were normal. Amslergrid test results were highly variable, and the locations of grid abnormalitiesand RPE defects were inconsistent.

During the next 5 years, the photographer developed chronic headaches,photophobia, blurred vision, and nighttime driving and reading difficulties.He reported episodes of monocular diplopia. He also reported a constellationof terrible, intermittently disabling, periodic, and chronic eye and facepains. The initial retina specialist ascribed all these symptoms to laserinjury. He also diagnosed a laser exposure in one of the photographer's companionspresent at the incident who reported similar symptoms but had completely normalfindings on retinal examination and fluorescein angiograms.

A review of the photographer's voluminous medical history several yearsafter the episode revealed dry eye syndrome, map-dot-fingerprint corneal dystrophy,temporomandibular joint syndrome, iritis, conjunctivitis, migratory arthritis,plantar fasciitis, chronic low back pain, epididymitis, and recurrent diarrhea.Most of the systemic problems predated the purported laser incident. New RPEdefects developed after the incident. The photographer had not been diagnosedpreviously as having reactive arthritis (Reiter syndrome),71 whichcan produce small RPE defects.72,73 Noevidence of laser injury was found in the years after the incident by 17 otherophthalmologists, including 5 neuro-ophthalmologists and 8 retina specialists.A trial was held 5 years after the incident in which the retina specialistwho made the initial diagnosis steadfastly maintained that all the photographer'ssymptoms were due to retinal laser injury. A jury ruled against the photographer'sclaim for damages against the ship owner.

Analysis

No laser was ever identified in this case despite a search of the ship.A costly, time-consuming chain of events was precipitated by the initial retinaspecialist's (1) failure to attach significance to an association betweenthe photographer's symptoms and his complex past medical history, (2) quickdiagnosis of a laser injury, (3) subsequent attribution of the photographer'sgrowing list of pains and visual complaints to a laser injury, and (4) diagnosisof laser exposure in the photographer's associate based on symptoms in theabsence of retinal or angiographic abnormalities. As noted previously herein,the few tiny RPE defects on which the initial diagnosis was based are common.Even if these defects were due to threshold laser effects, they could nothave caused the photographer's reported problems or millions of patients wouldbe afflicted with similar problems after routine retinal laser surgery. Inthis case, the answer to question 1 in the Table 1 is "yes." Regarding question 2, there were angiographicfindings but no optical coherence tomography abnormalities. The answers toquestions 3, 4, and 5 are "no." Question 6 cannot be answered because therewas no known laser source. The patient had real complaints, but they werecaused by preexisting autoimmune problems rather than by laser injury.

Comment

Accidental laser injuries are rare. Complaints of laser injuries aremore numerous. The ease of laser injury diagnosis is proportional to the severityof the injury. In ambiguous cases, subtle retinal findings should have excellentvisual prognoses and clinical outcomes. Absence of a retinal lesion does notprove absence of laser exposure. Nonetheless, retinal laser lesions that causeserious visual problems are readily apparent ophthalmoscopically and angiographically.They remodel in the months that follow an injury. Actual retinal laser injuriesdo not cause chronic eye, face, or head pains. Thus, pains in the months thatfollow a real or imagined retinal laser injury are nonorganic or the resultof regional or systemic problems unrelated to the laser incident. Fundus photography,fluorescein angiography, and optical coherence tomography should be performedas quickly as possible after a laser incident to document findings for analysisand comparison with subsequent tests.

The legal system has an uneasy relationship with "science" and "truth."Facts are welcomed by the attorneys of plaintiffs and defendants only whenthey support their clients' biases and best interests. Medical "experts" arehired to advocate opinions that are often unrelated to evidenced-based medicalpractice. Juries struggle to separate reality from fiction. Attorneys maycraft convincing cases for "victims" who claim severe pain and vision losseven when they have no physical evidence of injury. Patients with severe nonorganicproblems of psychiatric origin or organic problems originating from problemsunrelated to an injury may be dissuaded from solving these problems by hopesof financial gain.

A clinician's intransigence and misunderstanding of laser injury characteristicscan be powerful allies of tort attorneys. When retinal laser injuries arealleged but uncertain because objective findings are minimal or absent, laserinjury diagnosis should be deferred pending completion of a rigorous reviewand analysis of relevant laser devices and the purported victim's medicalhistory, clinical course, ophthalmic examination findings, and retinal imagingstudy results. Such a review and analysis may take weeks or months to completeauthoritatively. Hasty diagnoses should be avoided because they can createserious and lengthy medical, legal, and social issues. The 6 key diagnosticquestions given in the Table 1 providea framework for evaluating potential laser injuries. The diagnosis of a laserinjury should be evidence based, not a matter for speculation or conjecture.Retinal laser injuries do not cause chronic pain, and visually significantretinal laser injuries are apparent ophthalmoscopically and angiographically.

Correspondence: Martin A. Mainster, PhD, MD, Department of Ophthalmology,University of Kansas Medical School, Rainbow Blvd, Mail Stop , KansasCity, KS - ().

Submitted for publication August 4, ; final revision received February12, ; accepted March 25, .

This study was supported in part by the Kansas Lions Sight FoundationInc (Manhattan).

References

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