Indocyanine green angiography (ICG-A) and fluorescein angiography (FA) of the anterior segment are not commonly used in clinical practice, although several studies have underlined their importance for elucidating a wide range of eye pathologies like vascular occlusions, diabetic microangiopathy, glaucoma, tumors and injury.12345
The Heidelberg retina angiograph (HRA) has been commercially available for approximately ten years. Currently an updated version has been released in the market, the HRA II. The original one has been renamed "HRA classic". The new apparatus, the HRA II, possesses the option to examine the anterior segment and the vitreous cavity of the eye. This possibility does not exist in the original HRA classic yet. Therefore it would be useful to design an adaptable lens equipment for the HRA, to upgrade it for an extended use in the anterior segment and vitreous cavity.
The HRA produces real upright images. The parallel rays emerging from the HRA are focused in an emmetropic eye on the retina. To visualize the anterior segment of the eye, the parallel rays should be brought into focus at a distance of about 2 cm in front of the optic top of the HRA. Consequently, a plus lens of about 50 diopters is needed. The goal of this study was to develop an easy-to-use and low-cost optical device to expand the application of the HRA classic for the vitreous cavity and the anterior segment of the eye.
Materials and Methods
Two types of lenses were integrated in the new accessory device for the HRA classic. A 60-diopters lens (VOLK 60D) was used for imaging the anterior segment and a 30-diopters lens (VOLK 30D) for angiography of the vitreous cavity [Fig. 1]. The second piece of the cylindrical plastic frame was used to fixate the lens. The opening of the accessory devices was designed to fit on the cylindrical optic top of the HRA classic, so that it was placed exactly in the optical axis of the HRA classic.
Once placed at the optic top of the HRA classic the angiography of the anterior segment could be performed with the technique familiar from angiography of the retina and choroid. The device could easily be attached or removed without changing the patient's position, allowing angiography of the fundus, the vitreous cavity and the anterior segment without delay. The size of the scanned area could be varied between 10, 20 and 30 degrees. As the images were scanned by a resolution of 512 x 512 pixels, the 10-degree mode allowed the highest resolution. The confocal mode of the HRA provided tomographic scans of the area in focus, whereas the tissues of the anterior or posterior level to that plane were not added to the image. The HRA offers an available range of +11 to -11 diopters to focus on the favored area. Angiography of the anterior segment using the 60-diopters lens and of a choroidal melanoma with tumor extension in the vitreous cavity using a 30-diopters lens was performed and is presented as follows.
Angiography of the iris
First case: A 42-year-old man suffered from an insulin-dependent diabetes mellitus. Ophthalmic examination revealed proliferative diabetic retinopathy and a decent rubeosis iridis. FA of the iris, using the new accessory optical device, demonstrated patches of avascular iris [Fig. 2]. Leakage at the pupillary margin became evident in the late phase FA.
Second case: A 66-year-old man presented with general arteriosclerotic disease. A central retinal vein occlusion in the left eye five months before required fundus angiography. At this time the anterior and posterior segment examination revealed no signs of ischemia. Angiography of the iris presented physiologic findings without any proliferation or leakage in the late phase angiogram in the left eye. Although ophthalmic examination did not show any pathologic findings in the right eye, angiography of the iris surprisingly revealed small new vessels mainly at the pupil margin and leakage in the late phase [Fig. 3], requiring further pupillary evaluation and follow-up.6
Angiography of a choroidal melanoma with extension in the vitreous cavity:
A 58-year-old man complained of a decrease of visual acuity in his left eye for several months. Fundus examination revealed a huge brownish tumor mass. The tumor height was 10.6 mm with the typical signs of a choroidal melanoma evaluated by A-scan-ultrasonography. On ICG-A images the tumor caused a black area due to its localization anterior to the focused plane [Fig. 4a]. As the HRA consists of a confocal scanning system, a tomographic image was performed, scanning only details from the focal plane. Using the accessory device with the 30-diopters lens, visualization of the tumor was possible. Thus, tomographic scans through the tumor were obtained, allowing the visualization of leakage of fluorescein at the tumor's surface in the late phase of FA [Fig. 4b]. In contrast, ICG-A allowed a tomographic scan through the tumor and visualization of the tumor's own vessels, as the emission of ICG is in the near infrared range, allowing transmission despite the tumor's intense pigmentation [Fig. 4c].
This newly designed optical accessory for the HRA classic allowed the angiographic evaluation of the anterior segment as well as the vitreous cavity. Although the new laser scanning ophthalmoscope from Heidelberg Engineering, the HRA II, already includes this facility, the "HRA classic" is still widely used and will not be replaced at once. The advantages of this new accessory optical device are easy with fast attachment to and removal from the HRA classic, allowing both, anterior and posterior segment angiography in the same session. Furthermore, costs are reduced by the integration of a magnification lens commonly used with indirect ophthalmoscopes and therefore widespread and easily available. As the adapter is always positioned exactly in the optical path and at a constant distance to the optics of the HRA, the images are reproducible in size. Therefore adequate follow-up, especially important in tumors is granted. The high magnification and the resolution of 512 x 512 pixels enables the visualization of iris neovascularization even when slit-lamp examination does not allow adequate diagnosis.
We thank Mr. Djurica Bajic for the technical support and manufacture of the optical device.
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