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NR 1-3/2009
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Digital imaging of
the fundus with long-wave illumination
Cyfrowy obraz dna oka w
oświetleniu o długiej fali
Professor Pasyechnikova Nataliya, MD, PhD
Naumenko Volodymir, MD, PhD
Korol Andrii, MD, PhD
Zadorozhnyy Oleg, MD
State Institution „The Filatov Institute of Eye Diseases and
Tissue Therapy of AMS of Ukraine”
Director: Professor Pasyechnikova Nataliya, MD, PhD |
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| Summary: |
Purpose: To increase the
quality, diagnostic value and use of non-invasive fundus
examination with transscleral or transpalpebral
long-wave (red and near infrared) illumination.
Material and methods: For fundus visualization we used
red light diode sources at 660 nm and near infrared
light diode sources at 810, 940 nm. Light radiation from
diode sources penetrates into the globe through eyelid
skin and sclera. Fundus examination was performed
without dye injection and local anesthesia. The
technique was called «long-wave fundusgraphy» (LFG).
Results: Comparing with fluorescein angiography
additional topographical information was received
concerning CNV associated with hemorrhage or subretinal
fluid, which masked the true borders of the neovascular
component. If CNV is completely invisible under a layer
of blood or pigment, on fluorescein angiography only a
hypofluorescent area is registered. In such cases
fluorescein angiography is insufficient for correct
diagnosis. Examination of such patients with 940 nm
excluded maximum masking property of blood or pigment
deposits and permitted visualization of CNV.
Conclusions: Non-invasive, consecutive long-wave imaging
may be useful for CNV detecting and may obtain
additional information about fundus structures in
patients with dye intolerance, retinal hyperpigmentation,
haemorrhage or fluid masking subretinal structures,
miosis or in the presence of opaque media. |
| Słowa kluczowe: |
long-wave fundusgraphy,
retina, choroid. |
| Key words: |
długofalowa fundusgrafia,
siatkówka, naczyniówka. |
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Currently fluorescein and
indocyanine-green angiography (ICG) are standard procedures in
the diagnosis of retinal and choroidal diseases that involve
intravenous injection of contrast substance. However imaging of
the fundus without dye injection is playing an increasingly
important role, especially when there is intolerance or risk
related to injection of dye.
Photographing of the fundus with various light spectra,
including infrared, was first reported by I. Kugelberg (1).
However, standard infrared devices and systems of infrared
signal reception are unsuitable for fundus visualization. This
area of ophthalmology, as a potential source of additional
information of eye fundus structures, is presently
insufficiently developed and investigated.
Purpose
To increase the quality, diagnostic value and use of
non-invasive fundus examination with transscleral or
transpalpebral long-wave (red and near infrared) illumination.
Material and methods
This work was carried out together with the Ukrainian Institute
of Physics of Metals. The device for fundus imaging consists of
generation, focusing and registration of infrared radiation, a
power unit and a computer for processing of the received photo
or video signal and its demonstration on a monitor. For fundus
visualization we used red light diode sources at 660 nm and near
infrared light diode sources at 810, 940 nm. Light radiation
from diode sources penetrates into the globe through eyelid skin
and sclera. Fundus examination was performed without dye
injection and local anesthesia. The technique was called «long-wave
fundusgraphy» (LFG).
This study was conducted on 210 eyes of 200 patients and 57 eyes
of 30 normal subjects. 96 eyes had dry AMD, 114 eyes had
exudative AMD with active choroidal neovascularization (CNV).
The age range of all persons was 25 to 75 years. Patients were
included in the study with different levels of ocular media
opacities. LFG was carried out in eyes with small pupils and
with dilated pupils in the same patients. All images were
acquired by the same operator. We used standard ophthalmologic
examination for all patients including ophthalmoscopy, optical
coherent tomography (OCT) and fluorescein angiography (FAG).
Results
With 660 nm red illumination images of the retina and retinal
vessels were obtained (Fig. 1A).
In near infrared illumination (810, 940 nm) structures of the
choroid were more precisely visualized (Fig. 1B). The optic disc
was always dark. Retinal vessels were seen against a light
bright background. Choroidal vessels were dark and well
delineated under the retinal pigment epithelium or thin layer of
blood. LFG allows to image structures of the retina and the
choroid in red and near infrared spectral areas and also have
many advantages over angiography. Examination is possible
irrespective of pupil size.
Examination of patients with dry AMD revealed subretinal
deposits (soft drusen). In infrared light they appeared as local
sites of fading or elevation (for video mode) and were much more
numerous compared with ophthalmoscopy and color photography.
Part of subretinal deposits corresponded to clinically visible
drusen, other were seen only in red light (660 nm). Some
subretinal deposits could be detected only in infrared light. We
have shown that the borders of clinically visible drusen are
more precisely estimated in the red mode of LFG (Fig. 2).
However, borders of small subretinal deposits revealed by means
of LFG, were not always well visualized because of their small
sizes.
Additional information about CNV of various etiologies was
obtained (Fig. 3, 4). Red light has smaller significance
compared with infrared light in CNV imaging.
We describe one case with spontaneous contraction of CNV tissue
under the neuroretina. It concerned 65-year-old man with AMD and
the active predominantly classic CNV (Fig. 5).
A three dimensional video image of fundus structures and CNV may
be obtained because of the phenomenon of shadowing and motion
parallax. We were able to detect CNV in patients with
intolerance or risk factors to the injection of fluorescein,
when fluorescein angiography was contraindicated.
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Discussion
Red and near infrared fundus illumination were used because of
greater penetrating ability of long-wave illumination through
eyelid skin, sclera and retinal pigment epithelium (2).
Pathohistological findings in excised CNV showed cells of the
retinal pigment epithelium, fibrin and fibrous collagen
surrounding CNV (3,4,5). Products of blood degradation and
melanin are possible sources of high reflectance of near
infrared light (6). At 940 nm all CNVs consisted of two
components. The first component was represented as a bright (hyper
reflective) contour of the membrane, because of accumulation of
highly reflective materials. The central part of CNV was dark in
near infrared light (hypo reflective), because near infrared
light absorbed by water, hemoglobin and its derivatives (Fig.
3).
Contraction of CNV and subsequent perfusion disturbances were
not decreased near infrared reflectance of CNV (Fig. 5).
Comparing with fluorescein angiography additional topographical
information was received concerning CNV associated with
hemorrhage or subretinal fluid, which masked the true borders of
the neovascular component (7). If CNV is completely invisible
under a layer of blood or pigment, on fluorescein angiography
only a hypofluorescent area is registered. In such cases
fluorescein angiography is insufficient for correct diagnosis.
Examination of such patients with 940 nm excluded maximum
masking property of blood or pigment deposits and permitted
visualization of CNV.
Conclusion
Non-invasive consecutive long-wave imaging may be useful for CNV
detecting and may obtain additional information about fundus
structures in patients with dye intolerance, retinal
hyperpigmentation, haemorrhage or fluid masking subretinal
structures, miosis or in the presence of opaque media.
References:
1. Kugelberg I: Der Augenhintergrund in Infraroten Licht. Acta
Ophthalmol 1934, 12, 3, 179-190.
2. Elsner AE, Burns SA, Weiter JJ, Delori FC: Infrared imaging
of sub-retinal structures in the human ocular fundus. Vision Res
1996, 36, 1, 191-205.
3. Bynoe LA, Chang TS, Funata M et al.: Histopathologic
examination of vascular patterns in subfoveal neovascular
membrane. Ophthalmology 1994, 101, 1112-1117.
4. Grossniklaus HE, Hutchinson AK et al.: Clinicopathologic
features of surgically exised choroidal neovascular membranes.
Ophthalmology 1994, 101, 1099-1111.
5. Submacular Surgery Trials Report No. 7. Histopathologic and
ultrastructural features of surgically excised subfoveal
choroidal neovascular lesions. Arch Ophthalmol 2005, 123,
914-921.
6. Weinberger AW, Lappas A et al.: Fundus near infrared
fluorescence correlates with fundus near infrared reflectance.
Invest Ophthalmol Vis Sci 2006, 47, 3098-3108.
7. Delori FC, Pflibsen KP: Spectral reflectance of the human
ocular fundus. Appl Optics 1989, 28, 1061-1077.
The study was originally received 13.12.2008 (1094)/
Praca wpłynęła do redakcji 13.12.2008 r. (1094)
Accepted for publication 21.01.2009/
Zakwalifikowano do druku 21.01.2009 r.Adres do
korespondencji (Reprint requests to):
65061, Korol Andrii
State Institution „The Filatov`s Institute of Eye Diseases and
Tissue Therapy of AMS of Ukraine”
49/51 Frantsuzkii blvd., Odessa, Ukraine
e-mail: arkorol@inbox.ru
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Fig. 1. A – fundus black-white photograph of a
55-year-old woman. Dry AMD manifests as soft drusen. B,C –
fundus black-white photograph of the same patient with 660 nm
illumination. Borders of large clinically revealed drusen are
better estimated in red mode.
Ryc. 1. A – biało-czarna fotografia dna oka u 55-letniej
kobiety. Suche AMD w postaci miękkich druz. BC – biało-czarna
fotografia tej samej pacjentki w oświetleniu 660 nm. Granice
dużych druz stwierdzonych klinicznie są lepiej uwidocznione
w podczerwieni.
Fig. 2. A – digital photograph with 660 nm a
27-year-old man with a normal fundus. The optic disc looks
bright compared with the background. Retinal vessels are well
delineated. B – near infrared photograph (wavelength is 940 nm)
shows a dark optic disc and choroidal vessels against a bright
background.
Ryc. 2. A – cyfrowa fotografia przy użyciu 660nm u 27-letniego
mężczyzny z normalnym dnem oka. Tarcza n. II jest jaśniejsza od
tła. Naczynia siatkówki mają wyraźne obrysy. B – fotografia w
bliskiej podczerwieni (długość fali 940 nm), pokazuje ciemną
tarczę n. II i naczynia naczyniówki na jasnym tle.
Fig. 3. A – fluorescein angiogram of a
55-year-old woman. Hyperfluorescent area correspond to
predominantly classic choroidal neovascularization. B – near
infrared photo graph (λ= 940 nm) demonstrates CNV.
Ryc. 3. A – angiografia fluoresceinowa u 55-letniej kobiety.
Pola hiperfluorescencji korespondują z klasyczną, dominującą
neowaskularyzacją naczyniówki (CNV). B – fotografia w bliskiej
podczerwieni (λ= 940 nm) pokazuje CNV.
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Fig. 4. A – fluorescein angiogram of a
65-year-old woman. Hyperfluorescent area corresponds to occult
CNV. B – near infrared photograph (λ=940 nm) demonstrates CNV.
Ryc. 4. A – Angiografia fluoresceinowa u 65-letniej kobiety.
Pola hiperfluorescencji korespondują z ukrytą CVN. B –
fotografia w bliskiej podczerwieni (λ=940 nm) pokazuje CNV.
Fig. 5. A – fluorescein angiogram. B – fundus
color photograph of 65-year-old man with AMD and the active
predominantly classic CNV. C – fluorescein angiogram. D – fundus
color photograph and E – near infrared photograph of the same
patient with spontaneous CNV contraction 3 months later. Arrow
points to hyperfluorescent area corresponded to the retinal
pigment epithelium defect after CNV contraction. E – near
infrared photograph demonstrates contracted hyperreflective CNV
tissue.
Ryc. 5. A – angiografia fluoresceinowa. B – kolorowa fotografia
dna oka u 65-letniego mężczyzny z AMD i czynną klasyczną CNV.
C – angiografia fluoresceinowa. D – kolorowa fotografia dna oka
i E – fotografia w bliskiej podczerwieni u tego samego pacjenta
z samorzutną, ściągającą CVN – 3 miesiące później. Strzałki
wskazują pola hiperfluorescencji odpowiadające uszkodzeniu
nabłonka barwikowego siatkówki po ściągającej CNV.
E – fotografia w bliskiej podczerwieni pokazuje ściągniętą
hiperrefleksyjną tkankę CVN.
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