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with either a double-sided macro flash or a builtin ring flash. These macro flashes are typically meant for short range (less than one meter) photography for optimum illumination. When photographing oculoplasty patients for full body photography, a studio flash set-up is still the recommended approach.

Fundus Camera

Mydriatic Fundus Camera

Conventional non-corneal contact mydriatic fundus camera (Fig. 11.2) can range between 20 and 60 degrees view of the ocular fundus. The ophthalmic photographer can choose the angle of view that will best reflect the needs of the photodocumentation, for example, in imaging the optic nerve for glaucoma one would use a view of 20 degrees, while in the case of a large melanotic choroidal tumor one would select a

Fig. 11.2: Fundus camera

wider 60 degree field of view. Mostly, these retinal cameras capture full color images of the retina as well as having capabilities of capturing monochromatic and angiographic images (fluorescein and ICG). Determining the exposure level of electronic flash is completely different from the regular 35-mm camera used in external photography. Usually, these values are predetermined (factory setting) by the angle of view selected on the retinal camera as well as the film sensitivity used. Other determining factors for flash intensity can be the use of a plus diopter setting and angiographic or monochromatic selections (such as cobalt-blue and red-free). Typically, retinal cameras have two or more camera backs; a 35-mm camera for color or monochromatic black and white film, a polaroid camera and in some cases certain retinal camera manufacturers offer optional video camera (analog or digital) to show the images on the monitor and store them in imaging software program on the computer system.

Non-mydriatic Fundus Camera

As the name suggests, the non-mydriatic fundus camera does not require the use of mydriatic agents to dilate the patient’s pupil. The nonmydriatic fundus camera usually requires a natural dilation of 4 mm; this can be a limiting factor on patients over the age of 60 years old that typically do not naturally dilate well. These fundus cameras are usually very easy to operate as they have no viewfinder but instead they use a large 4-inch monochromatic TV monitor (or in some more modern non-mydriatic cameras, an LCD screen) where the patient’s fundus can be seen by way of an infrared video alignment camera. Since the viewing lamp utilizes infrared wavelength, the patient is not aware of the examination process. The flash illumination, when using a low LUX video charged couple device (CCD) camera, is usually very low as these

Fig. 11.3: Non-mydriatic fundus camera

cameras have a very high sensitivity. The lower the LUX level of the color CCD camera, the faster the pupillary recovery time and thus, the faster the photographic procedure. There are many manufacturers of non-mydriatic fundus cameras some have the ability to capture angiographic images. When one uses mydriatic cameras in the mode of non-mydriatic, these cameras are usually confined for mid-phase only as a waiting period of at least one minute must be allowed to permit full pupillary recovery time. Nonmydriatic cameras can download their captured images to a computerized filing system. Often, non-mydriatic cameras (Fig. 11.3) are used to photograph diseases of the posterior segment of the eye.

The camera is very small and light weighted, it can be easily taken outside of the clinic. Fundus images have been stored on a personal computer directly from the camera using USB cable and an exclusive software.

Indocyanine Green Angiography

Indocyanine green angiography (ICGA) can be performed with near-infrared illumination using

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Fig. 11.4: ICG angiogram

a retinal camera. ICGA examines the dynamic flow circulation of the choroidal vessels and adjunct structures (Fig. 11.4). Typically, a retinal camera that has been designed with special filters uses a black and white near-infrared CCD video camera (analog or digital) and records static megapixel images stored in a computer bank or dynamic images on videotapes as in the case of the scanning laser ophthalmoscope (SLO).

Digital Hand-held Fundus Camera

Digital hand-held fundus camera is recently introduced. This camera is designed for digital images, therefore, it becomes light and easy to operate compared to the previous model. The fundus images are displayed on a small LCD monitor and can be checked. These images can be stored on a memory card.

There is an adapter for indirect images. The adapter is very useful while taking the fundus photographs of the premature babies (Fig. 11.5).

Photo Slit-lamp (Kowa Attachment)

The hand-held Kowa Genesis camera has a special attachment (Fig. 11.6) that allows for anterior segment photodocumentation using a

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Fig. 11.5: Digital hand-held fundus camera

Fig. 11.6: Kowa genesis with slit-lamp attachment

slit-adapter. It allows the user to take images on either 35-mm film, video or fully digital backs. Once the adapter is connected, it is possible to capture conventional anterior segment images including of gonioscopy (Fig. 11.7). For

Fig. 11.7: Gonio photography

gonioscopy, topical anesthetic agent and a transparent gel such as Gogniosol should be used. A lens that has anti-reflection coating should be preferred.

Use of gonioscopic lenses need special techniques, however, combined with the use of a video camera it makes it easier to preview the captured field as opposed to capturing on conventional 35-mm film and waiting for the film to be processed to evaluate the photographic technique. However, using video-captured image does not equal the quality of 35-mm film (resolution, hue, color, contrast) but most surgeons agree that the trade-off of immediacy in seeing the images is well worth than the quality of the 35-mm film. For publication a conventional 35-mm film can also be used in conjunction with the video images.

Portable Slit-lamp with Video Camera

Portable slit-lamp is very useful when taking pictures of bed-ridden patients and/or small children. This slit-lamp can adapt a very small video camera and can take patients’ anterior segment photographs or video images.

Photography in Operating Theatre

There are two main ways of capturing images in the operating theatre, the first consists of positioning the camera next to the operator using a bedside approach, while the other technique

is to attach a camera directly to the operating microscope and have the operator take all images using one of the optical pathways of the microscope (right or left). Using this technique means that the photography port will be taken through a 70/30° type of prism and that the operator will have to look through only the optical pathway that is occupied by the camera. Using this technique will ensure the operator that what he/she sees is actually captured. Additionally, using this technique will give a good preview of the non-stereo image that is captured by the recording device since only one optical pathway is equipped with a recording device (usually the right optical pathway is best). It is critical that the microscope should be set for focusing the recording device and not the operator’s actual diopteric correction. If this is not done, captured images may not be sharp. The operator will also notice that the field viewed and the field photographed is not exactly the same area (usually the photographed field is smaller) but with practice and years of experience, very good results may be achieved. It is critical as in any other type of photography that the primary lens (lens close to the patient’s cornea) should be free of artifacts such as: dust, fingerprints, water stains, fluorescein stains. Attentive care should be given to the lens cleaning techniques to avoid possible damage to the costly lens. If this is not done, the quality and color of the captured images will be very low with color shift and low contrast images as well as poor optical resolution.

Specular Microscopy

Photography of the corneal endothelial cells can be easily performed using a slit-lamp photomicroscope and resulting images can be analyzed using a computer program. Typically, these images can show the borders of the cells that reflect the light towards the high magnification microscope lens when used in conjunction with

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specular illumination methods. This illumination can be achieved by using the illumination tower set at 45 degrees (incident light) from the apex of the cornea while observing the return light (reflected light) through the objective when the observation tower is set at 45 degrees from the opposite side of the illumination tower. Recent trends in specular microscopy are the use of noncontact specular microscope that causes little trauma to the patient and risk of cross contamination is less because no corneal applanation is required with the system.

In Figure 11.8 one can easily compare the size and/or the arrangement of the endothelial cells. With innovative imaging technology the use of non-contact specular microscopy can be easily observed on large monitor obviating the use of printsorphotographyonsilverhighlightfilmbase.

Fig. 11.8: Specular photography: endothelial cells

In the past, the role of the ophthalmic photographer was limited to the capturing of the endothelial cells of the cornea. Today, however, the role of the ophthalmic photographer has evolved to include the analysis of the corneal cells using a computer program (Fig. 11.9).

Imaging System

In 1990, the field of ophthalmic photography was introduced to electronic imaging technology. At first, only two companies in the United States

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Fig. 11.9: Noncon robo

were in the forefront of this newly introduced technology—KOWA VK-2 system (Fig. 11.10), Topcon ImageNet and Ophthalmic Imaging Systems (OIS). Soon thereafter, a flurry of imaging systems appeared mostly in PC base and mostly disappearing in a year or two. In the past ten years, this new technology has grown to be an

Fig. 11.10: Digital imaging system: KOWA VK-2 system

accepted daily routine tool of major universities and HMO type practices. The electronic imaging has mostly replaced all film based angiography (especially true for ICG) avoiding the long darkroom delays. Although this technology is not comparable to film based technology, yet as far as resolution and gray scale, it does offer certain advantages, such as, instant results viewable on large CRT screens, image processing or enhancement, transfer of images through the internet for teaching, screening or second opinion (teleophthalmology).

Advantages

Imaging system has following advantages:

1.Captured images are displayed on a monitor immediately,

2.Displayed images are large, so the patients who are dilated or have low vision can appreciate them,

3.Images may be reviewed by the treating ophthalmologist as they are being captured,

4.Prints can be produced immediately on thin paper so it is easy to put on a patient’s chart, and

5.Images may be stored in the computer data base system for easy review and follow-up.

Disadvantages

Imaging system has following disadvantages:

1.The computer systems are quite expensive and technology changes rapidly making systems obsolete in one year,

2.Computer, large CRT screen and printer require additional space,

3.Operation of the computer and system software requires training and maintenance, and

4.Quality of image is not yet comparable with 35-mm film.

Imaging systems in ophthalmology typically means that the conventional ophthalmic camera recording device such as the 35-mm or polaroid type back is replaced with a charged couple device (CCD) that may be either analog (video signal) or digital (higher resolution than video signal). These CCDs usually can add significantly to the cost of the fundus or slit-lamp camera especially if they are digital in nature. Digital CCD can be either a single chipped red, green and blue chipped or could be 3 chipped, one for each of the RGB wave lengths. The latter is far more expensive than the single chip but the color separation with the three-chip-CCD is superior. The area of sensitization of the CCD chip (usually varying from inch-to-inch) being much smaller than of the 35-mm surface (24 mm × 36 mm) or of the polaroid sheet, the light (flash intensity) required to expose the light sensitive CCD is significantly less than that of traditional film base emulsion to expose the same area of the eye. Much like the film base emulsion, CCD comes in a variety of sensitivity calculated in LUX values. The lower the value in front of the LUX, the more sensitive (and usually more expensive) the CCD is. However, it can also be said that the more sensitive the CCD is, the more electronic “noise” (comparable to large grain when referring to film) can be produced (comparable to higher sensitivity film such as 1,600 or

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3,200 ISO). More recently, ophthalmic manufacturers: have introduced non-mydriatic retinal cameras with purely digital recording devices. Non-mydriatic cameras are usually equipped with two CCD, one is a black and white infrared low resolution used for alignment of the patient’s retina (image is viewable on a small CRT screen located on the base of the non-mydriatic retinal camera), while the second is used to actually capture the color image of the retina through the naturally dilated pupil in a dimly lit room. One of the main advantages of the low light CCD chip used in the non-mydriatic camera is that retinal images can be captured sequentially without having to wait 4 to 5 minutes as with instant type photography (polaroid). The captured retinal images typically do not affect seriously the natural dilation of the pupil. Pupillary recovery is usually very fast as opposed to when using instant type film. Additionally, some non-mydriatic retinal cameras can capture ICG angiography since in some cases the infrared cameras used higher resolution.

Photograph of Both Eyes

To take the photographs of ocular movements especially in case of strabismus, amblyopia, and ocular muscle disorder, eye gaze position in 9 directions should be captured (Fig. 11.11). To

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achieve this type of photography, simply place the patient’s head in a straight forward position referred to as primary gaze. Having selected a long lens such as 135-mm macro or 150-mm macro combined with a ring flash, and patient is asked to fixate at a gaze of 30 degrees in each o’clock position such as 12 o’clock, 1:30, 3, 4:30, 6, 7:30, 9 and 10:30 and take photographs in each of these positions. Make certain that the patient maintains his or her head in the primary straight forward position and avoid side-to-side head shifts or frontal and backward tilts. When taking photographs in downward gazes (4:30, 6, 7:30 o'clock), an assistant should help in lifting the eyelids in order to expose those gaze positions. For an overall even illumination, the use of a ring flash should be used, as the ring flash will create a ring pattern on the patient’s corneas, will be equidistant and could be considered as a Heirshberg ring. The long macro lens (135- 150-mm macro) will avoid facial distortion and give accurate facial renderings.

Photography of Face and Skin

For full-face photography of patients (Fig. 11.12), the practice of using a long 135 to 150-mm macro lens still applies in order to maintain correct facial proportions and avoid the distortion created by wider-angle non-macro lenses. It is important that the patient wipes the facial sweat or heavy make-up used by some women as well as any ocular ointment used onto the eyes prior to taking photographs. This practice will avoid getting any unwanted or irregular flash reflexes. Typically, it is a good idea to use an electronic set of flashes mounted as in a photo studio. This type of illumination helps to accentuate areas of interest by creating shadows. If no flash is available, it is possible to use natural outdoor sunlight illumination but caution should be used not to over-expose the area of interest and use a standard blue or gray background. To document

Fig. 11.12: Face and skin photograph

proptosis, the best position is to capture the image from above the patient’s head using two macrotype electronic flashes set at 90 degrees from the patient. This technique will create the appropriate shadows that will help define areas of interest to the oculoplastic surgeon.

Photography of Pupil

In some cases of neuro-ophthalmology, it is important to document the pupillary changes of patients and to differences between the right and the left pupil (as both may dilate differently from each other under similar Lux conditions). The best way to record these differences is to use a black and white camera that is mounted on a tripod (for added steadiness) and have the patient place his chin in a chin-rest (also for added steadiness). The room is then darkened and about 5 minutes is needed to allow for each pupil to either dilate or constrict depending on the particular condition of the patient (at times a flash light, white light, may be used to provoke

a specific pupillary reaction that is recorded on video). Analog iris recorders are available that use infrared CCD cameras in combination with an infrared illumination system that is not perceivable to the patient and where the patient’s pupil does not react. Images are then recorded as either a series of still images or as a string of segments (continuous video images) that are then transferred to a computer for numeric processing. Typically when performing these studies, no mydriatic agents are used unless otherwise indicated by the examiner.

External Photography

When taking photographs of the cornea and the lens, the choice instrument is a photo slit-lamp since it has the correct optical magnification and the appropriate flash to accomplish the task at hand. However, when a photo slit-lamp is not available, a 35-mm SLR camera with macro lens and electronic flash or even a fundus camera (using a plus diopter) may be used. External close-up photography of one eye for the purpose of documentation of ocular trauma or tumors can be taken with a macro type lens (usually a long lens) and a side macro flash (usually mounted on either side of the front of the macro lens) to avoid disturbing flash reflexes often found when using a ring flash type systems. Careful evaluation of where the flash reflex will fall is critical in obtaining useful photo-documentation. Many macro type electronic flashes have what is called a modeling light that is mounted directly next to the flash tube. These modeling lights will illuminate the field of interest and give a good idea of where the flash reflexes will show-up when the photograph is captured. Since the cornea and sclera are highly reflective surfaces, special attention needs to be given to the illumination technique. It is possible to limit these reflections by using polarizing filters on the flash

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and lens, however, the reflexes will only partially disappear and the iris detail is made very dark.

Conventional 35-mm SLR Camera

When using a 35-mm macro lens for ophthalmic photo-documentation, it is critical to select a lens that will keep the true perspective of the area of interest. Nikon Corporation introduced a special macro lens with intergraded ring type macro flash tube. This special macro lens called Nikor Medikor lens, it comes in two focal lengths. This lens works somewhat differently in that the photographer selects the required magnification on the lens and then simply focuses by physically moving towards or away from the patient. Other possible choices for macro lenses

Use of Fundus Camera in External

Photography

The hand-held fundus camera (Kowa Genesis) may be especially useful in close-up external photography as the system uses a powerful distortion-free macro lens along with a co-axial illumination in the fundus camera that produces a small reflex on the cornea or sclera. This camera is particularly well suited in the pediatric population (Fig. 11.13).

Some table-top retinal cameras are also well suited for external (single eye) photo-documen- tation of the eye; these retinal cameras are usually fitted with a frontal concave lens. To capture the images, simply position the patient in the chinrest as you would for conventional retinal photography and select a plus diopter setting

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Fig. 11.13: Photograph of external eye with handheld fundus camera

(as well as in some cases selecting a higher magnification lens) by focusing the retinal camera until the images becomes clear. Film type and flash exposure is the same as for regular fundus photography (Fig. 11.14). For taking fluorescein stain photography of the cornea or sclera, the retinal camera may be the most useful instrument since it already has both the exciter and barrier filter in place (Fig. 11.15). When performing iris angiography, again the retinal camera is best suited for this purpose not only due to the filters but also because these cameras are equipped

Fig. 11.14: Photograph of external eye with table-top fundus camera

Fig. 11.15: Fluorescein stain photography

Fig. 11.16: Anterior segment fluorescein angiogram

with an internal timer that is critical for fluorescein studies requiring dynamic flow analysis (Fig. 11.16). Black and white films ISO 400 or instant type (polaroid or Fuji) film can be used and processed in a similar way as for retinal angiography.

Optical System of Fundus Camera

Fundus camera’s optical system can be compared to the Galilean type telescope and is characteristic by incorporating an internal co-axial type illumination and electronic flash. The light

emitted through the objective of the camera lens is a ring-shaped image. The distance from this ring to the surface of objective lens is referred to as the working distance and is of great importance in taking good artifact-free fundus photographs. The actual position of this ringshaped light can be best observed by looking from the side of the fundus camera. To keep this relative position constant is one of the most important and basic points in fundus photography to insure good color saturation and artifact-free photography (Fig. 11.17).

Fig. 11.17: Working distance

Fundus Photography

Preparatory Operations

Prior to starting the photographic session, the patient’s eye must be dilated with a mydriatic

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agent to achieve best possible pupillary dilation (optimally a pupillary dilation of over 8 mm is desirable). The objective lens should be clean and free from dust and smear. Any dust particles must be carefully removed with a manual blower while smear should be removed with lens cleaning paper. Check that the film is correctly loaded and flash intensity control is properly set according to the film sensitivity as well as the retinal pigmentation. Also adjust the eyepiece diopter scale to match the operator’s diopteric correction (Fig. 11.18). Adjust the height of the motorized camera table as well as the operator’s and patient’s stool so both may be as comfortable as possible in front of the fundus camera (Fig. 11.19).

Fig. 11.18: Diopteric correction

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Fig. 11.19: Comfortable position

Operational Procedures

The patient rests his/her chin on the chin rest and presses his/her forehead lightly against the forehead bar. Adjust the patient’s lateral canthus with the head rest of the fundus camera and align the patient’s eye with the illumination beam and optical pathway of the fundus camera. If necessary, adjust the optical table for optimal patient comfort.

Looking through the viewfinder of the fundus camera, focus the camera until you obtain a sharp image of the posterior segment of the eye. Slightly adjust the joystick (left-right-forward and backward) to set the camera to a position in which the subject’s eye is evenly illuminated. It should be free from flares and reflections. One should try to achieve maximum color saturation. Ask the patient to gaze at the fixation target until you have the desired area of the fundus in your viewfinder. It is important for operator to ask the patient to keep both eyes open throughout the entire photographic session. Also make certain that the eyelids as well as eyelashes should not obstruct the light passage. The light

Fig. 11.20: Beam pathway

beam should be projected entirely into the pupil to avoid artifacts to be recorded on the film (Fig. 11.20).

If pictures are taken before the above conditions are fully satisfied, reflections and/ or artifacts will be produced and it will result in a lower picture quality and poor contrast. Once all these conditions have been fully satisfied, capture the image with a minimum delay, otherwise the patient may be tired and lose fixation and concentration. When the patient is asked to keep his eye open for over 30 seconds, the tear film starts breaking and cornea gets dry causing a low contrast photograph. It is important to always keep in mind that the patient’s comfort and well-being is critical in order to achieve good photo-documentation. Speak slowly and clearly explain the photographic procedure to the patient in order to lessen his or her anxiety.

Fluorescein Angiography

Ophthalmic photography is unique because the medical photographers also perform dynamic flow studies of the iris, retina or choroid using dyes such as sodium fluorescein or indocyanine green. These studies provide a vital piece of information needed by the treating ophthalmologist in order to understand the vision problems of a patient. Fluorescein angiography (FA) is often more complex than conventional color retinal photography. This, however, is not the case, the main differences between color retinal photography and angiography are a set of filters (usually a set of exciter and barrier filter) and remembering the correct sequence of the flow study (area to be photographed in the early, mid or late phase that are usually recorded with a timer).

Principle of Sodium Fluorescein

Angiography

Sodium fluorescein is mainly used to perform dynamic flow studies of the integrity of retinal vessels (in some cases, sodium fluorescein may also be used in the study of the vascular integrity of the anterior segment). Once the pupils are sufficiently dilated, a solution with a concentration of 10% (2.5 cc of volume) or 25% (1 cc of volume) of sodium fluorescein is injected in the patient’s vein. Injection volume should be carefully controlled in children or patients weighing less than 100 pounds. When using a concentration of 10% of sodium fluorescein, a recommended dose of 0.066 cc per kg should be used. It not only avoids adverse reactions but gives a good fluorescence standard in the dynamic flow study. The dye travels throughout the body’s circulatory system (first throughout the veins) including the retinal vessels. When observing the retina with a cobalt blue light (referred to as the exciter light set at about

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Fig. 11.21: Fluorescein absorption and emission

490 nm), sodium fluorescein reflects a green fluorescence towards the film plane of the retinal camera. Before arriving to the film plane, that green fluorescence passes through a yellow barrier filter (referred as the barrier filter) that removes all unwanted blue light that may interfere with the true appearance of the fluorescence found at about 520 nm. These exciter filters (cobalt blue set at 490 nm) and the barrier filter (sharp cut-off filter set at 520 nm) must be matched perfectly in order to render true fluorescence images of the retinal vessels (Fig. 11.21).

Film Type and Development

The amount of fluorescence perceived by the film when properly excited by cobalt blue illumination is somewhat low; therefore, a highly sensitive black and white film such as ISO 400 film should be used. When processing this black and white film (in total darkness), use a medium to high contrast fresh developer in conjunction with an extended processing time in a solution set at 20°C/68°F. Push process is a technique that is used in angiography to see more detail on the film produced by the fluorescence; this technique consists of processing the exposed sensitive film for an extended period of time (50 to 100% longer) or to process the film in a warmer solution say 2 to 4 degrees centigrade higher.

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Photographic Procedures

Fluorescein angiographic study consists of several phases based on time sequence. Depending on the particular ocular disease, dynamic flow studies vary between 3 and 15 minutes. Fluorescein angiography has following phases:

1.Preinjection or control photograph: It is a photograph in which both the exciter and barrier filters are in place and a photograph is taken without the presence of sodium fluorescein. This is usually done to determine the presence of pseudo-fluorescence or autofluorescence such as in the case of drusens.

Fig. 11.22: Arterial/venous phase of FA

2.Arterial and venous phase: This is the early phase of the angiogram study usually within 14 to 30 seconds after injection of sodium fluorescein (Fig. 11.22).

3.Mid-phase: When all retinal vessels have been filled (stained) with sodium fluorescein (from 30 seconds to 120 seconds).

4.Late phase: This is the last phase and varies in duration depending on the disease of the patient. In diabetic retinopathy, this phase may vary from 3 to 5 minutes, whereas in some ocular tumors, it may last as long as 15 to 20 minutes (Fig. 11.23).

Fig. 11.23: Late phase of FA

The fluorescein angiography helps in understanding various retinal diseases and abnormalities. One needs to study carefully the retinal drawing of the patient’s chart and look for notes or direction from the retina specialist to understand the areas of interest and the main phase of the study (early, mid or late). It is critical to follow precisely the retina specialist’s notes to understand the diseased eye to be first studied (right or left eye). How soon the retina specialist needs to evaluate the results of the angiogram? Does the retina specialist need to treat the patient with laser immediately after the angiographic study? This is referred to as a STAT angiogram. A good practice is to carefully study the diseased retinal areas when performing color photography, usually done prior to an angiography. Once you understand the ocular disease, you can start the angiographic procedure with a good plan. Number of images in each phase, early, mid and late phases as well as area of interest, are dependant on a particular study. It is, however, important to get different results from what were initially anticipated. In fact, at times, angiographic pattern may be completely different from what was anticipated, a retinal vessel that was thought to be leaking may be intact and

Fig. 11.24: Nerve fiber layer with blue filter

a normal one may be found leaking. Anticipating the unexpected findings comes with years of angiographic experience and a good set of standardized angiographic protocol.

Monochromatic Fundus Photography

Various monochromatic wavelengths penetrate at different layers of the eye revealing specific structures as well as foreign bodies in those layers. With the appropriate monochromatic wavelength filter (cobalt blue filter), it is possible to isolate the first layer of the retina where you can find the nerve fiber layers (Fig. 11.24). This

Fig. 11.25: Red-free photography

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Fig. 11.26: Choroidal pigment with red filter

may be very useful while documenting a patient with glaucoma to demonstrate nerve fiber dropout. A green filter (referred to as red-free) will cut out all red-light making those areas black (red is seen as black) creating a nice high contrast image of the posterior pole. Red filters will allow the longer wavelengths of the visible spectrum to penetrate deep into the ocular structures to reveal the choroidal vascular pattern (choroidal vessels appear as white while retinal vessels will appear as black Fig. 11.25) and a choroidal nevus or melanoma (Fig. 11.26). These photographs, in particular those taken with red-free light, are very suitable for printing use.

Anterior Segment Photography with Photo Slit-lamp

The anterior segment is usually photographed with a photo slit-lamp biomicroscope (Fig. 11.27). It is similar to the clinical slit-lamp biomicroscope that is used in our daily work; with the exception that it incorporates a camera (static or motion such as video) and an electronic flash light. Needless to say, photographers need a good understanding of the clinical instrument before they can become skillful in capturing clinically useful images of the anterior segment (Fig. 11.28).

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Fig. 11.27: Photo slit-lamp

Different from fundus photography, photo slitlamp biomicroscopy is perhaps the most challenging type of photography in the field of ophthalmology. It requires a good understanding of the ocular structures; disease process as well as illumination techniques to illustrate the area of interest to the clinician. The illumination is of key importance.

Since pathology varies greatly and may appear differently for each case, simple changes of slit-width, height angle of the illumination tower or even the use of diffuser, the same pathology may show itself quite differently in the final picture. It becomes essential to select most suitable lighting technique for each situation. This challenge is perhaps what gives the photographer greatestpleasurein takingpictures of best area of interest.

In observing through the slit-lamp the reflections from the cornea and lens are not so offensive. However, same reflections may become disturbing and even harmful in hiding areas of interest when taking photographs. Adjust the illumination tower angle to avoid unwanted reflections. When using auxiliary light (often

Fig. 11.28: Slit-lamp photograph of lens with various nuclei

referred to as fill light), it is necessary to pay attention to avoid the reflection that light may produce on the cornea. Carefully place the area of interest in the field to be photographed while making certain that you are using the best possible form of illumination. Use appropriate magnification to ensure that not only the area of interest is captured but you leave enough room to have a point of reference for follow-up photographic sessions (for example, in photographing an iris melanoma; use of medium magnification would allow for a portion of the iris to be seen for identification that the mass is located at 12, 3, 6 or 9 o’clock and provides an idea about the size of the mass.

Bibliography

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2.Kwan A. A simple slit-lamp digital photographic system. Eye News 2000;6:18-21.

3.Prasad S. Digital video in a surgical setting.

J Cataract Refract Surg 2004;30:2302-03.