British Journal of Ophthalmology, 1981, 65, 702-706

Video funduscopy and fluoroscopyW. M. HAINING

From the Department of Ophthalmology, University of Dundee, Ninewells Hospital andTeaching School, Dundee DD2 1UB

SUMMARY A system of television ophthalmoscopy has been developed using commercially avail-able colour television cameras and a specially designed high-sensitivity monochrome televisioncamera. Funduscopy and fluoroscopy can be performed at low light levels and recorded on standardvideo tape for clinical evaluation and also as a teaching aid. A computerised television stereoophthalmoscope image processor is being developed for real-time volumetric recording the volumeof the optic disc cup in glaucoma.

The application of a television system to produce anelectronic image of the human fundus oculi wasdescribed by Ridley' some 30 years ago, working inconjunction with the Marconi Wireless TelegraphCompany. At that time, however, there was no satis-factory fundus camera which was free from opticalartefacts. Ridley therefore designed a flying spotmonochrome television (TV) ophthalmoscope, andPotts and Brown2 went on to develop a colour tele-vision ophthalmoscope in 1959. The main disadvan-tage of their systems was an unacceptably high level offundus illumination. This entire field of research wassurveyed by Dallow.3

Improvements in TV technology over the past fewyears have produced a new generation of camerassuch as the Circon low-light-level single-tube colourcamera, reference MV9295, and the inexpensiveHitachi Denshi Model GP5. The Badger 25 SIT is anultra low-light-level monochrome TV camera. Thesecameras, coupled with a newly designed high-efficiency ophthalmoscope from Carl Zeiss, Jena,constitute the first commercially available TVfunduscopy and fundus fluoroscopy systems.Fundus fluoroscopy dates back to 1961, when

Novotny and Alvis4 described the application offluorescence emission photography as a practicalmethod of displaying the fine detail of the humanretinal and choroidal circulation. High-speedrecording of the passage of fluorescein dye entry wasobtained by a cine fluorographic technique.5Although this was used in the investigation of retinaland choroidal circulatory disorders, the time delay indark-room processing of cine film, and the subsequentneed for projection screening, proved unacceptable.

Correspondence to Dr W. M. Haining.

The reason for designing a high-resolution TVfunduscopy system was dictated by the need to makefluorographic results immediately available to thereferring clinician, particularly when these wereurgently required. In 1973 Van Heuven and Schaffer,6using the Littman fundus camera, designed a low-light-level TV system using an image intensifier. Sub-sequent technological developments in TV tubedesign for ultra low-light-level requirements inmilitary surveillance have resulted in the manufactureof an integral silicone intensified target tube of lightweight and small dimension.The Stereo-ophthalmoscope 110 from VEB Carl

Zeiss, Jena, GDR, was chosen as having the bestoptical system for TV ophthalmoscopy. The fundusoculi can be observed through 3 viewing angles, 400,29°, and 14.50, corresponding to 15 x, 20 x, and40 x magnifications. The binocular indirect stereo-ophthalmoscope gives excellent 3-dimensional visual-isation of the fundus oculi with detailed inspection ofthe vitreoretinal boundary layers. Stereo fluoroscopywith the blue filter enables stereoscopic observationof fluorescence angioscopy and spatial localisation ofextravascular fluorescence.The Stereo-ophthalmoscope 110 can be fitted with

I or 2 supplementary observer eyepieces for instruc-tion, discussion, and teaching, but the introduction ofa television viewing system greatly improves thesefacilities.

Television ophthalmoscopy and fluoroscopy systems

The stereo-ophthalmoscope can be readily convertedinto a television ophthalmoscope by replacing thebinocular tube and beam splitter with a specially

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Video funduscopy and fluoroscopy

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Fig. I Camera set up showing Badger SITcamera mountedon television ophthalmoscope with Sony U-Matic video cassetterecorder, set at stop-frame, in the background.

designed adapter for the attachment of colour andmonochrome television cameras (Fig. 1). The con-version can be effected simply and quickly, with dove-tail mountings and preadjusted magnetic holders.The TV adapter has a variable aperture stop which

can be closed completely and also houses the fluoro-scopic barrier interference filter. There is a choice ofeither 50 mm or 100 mm focal length objective lens(Table 1).The efficient light gathering power of the optical

system in the Stereo-ophthalmoscope 110 and specialTV adapter, in conjunction with highly sensitivemonochrome and colour television cameras, resultsin very good quality television imaging.

Colour television ophthalmoscopy. The quality ofimage equates well with the appearance of the fundusoculi obtained by conventional ophthalmoscopy. Thegreater contrast and therefore resolution obtainedfrom the monochrome television camera is used toadvantage in television fluoroscopy.

In practice the entire fundus oculi can be covered

by manipulating the television ophthalmoscope inrelation to the television monitored image, givinggood control of fine focusing and reflex free fields ofview. The compact lightweight television cameras arecounterbalanced by the tilting and rotating stereo

Table I Technical details of the television ophthalmoscope

50mm lens 100mm lens

Viewing angle 420, 42°. 220 40, 30. 15°Magnification 7 2 x, 10 x, 20 x* 14.5 x, 20 x, 40 xtResolutiont (lines/screen)in horizontal direction Better than 250 Better than 250Minimal structures resolvablein mm (calculated from theabove) 0 22 ,016,0-08 0)11,008.0n04Illumination 6V 20W halogen lamp, variable intensityThe recommended lens is the 100mm lensIncreased sensitivity with some reduction in resolution is obtainable with the50mm lens

*Maximum angle without vignetting.tProvided 16 x magnification by the television system (1 inch (2 5 cm) cameratube window-20 inch (50 cm) monitor screen).tTheoretical limit, calculated from the image diameter on the camera tube andmanufacturer's specification.

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ophthalmoscope mounting, allowing the operator topan around both central and peripheral fundus fields.Alternatively, the patient is instructed to move theeye in the required directions as in conventionalophthalmoscopy.Because the television cameras are easily detach-

able they can be used as a multipurpose televisioncamera module on different instruments such assurgical operating microscopes and biomicroscopes,thus spreading the functional cost of a single televisioncamera over several fields of application. Televisionophthalmoscopic and fluoroscopic data can be storedby means of a standard video cassette recorder eitherfor direct visual analysis on replay or for feeding intoan image analysing system for quantitative studies.

Video fluoroscence angioscopy. The outstandingadvantage of television fluoroscopy is the dynamicvisualisation of choroidal and retinal vessel flow inhealth and disease. Although the maximum resol-ution is limited to about 40 ,um when working withthe 100 mm lens, i.e., only about a quarter of theresolution obtained from black-and-white high-speedfilm which is conventionally used in fluorography, thishas been found adequate in practice for most clinicalinvestigations of ocular circulatory disorders.

Basically the same instrument is used as describedpreviously, but instead of the colour televisioncamera an intensified target black-and-white camera,Badger SIT from RT Laboratories, UK, is used. Thiscamera gives a clear television image at incident lightlevels of 10-2 lux, and it has a resolution which iscomparable with the Circon colour television camera.

This image intensified tube has an exceptionallyhigh-quality response and was specifically designed atRT Laboratories to have maximum sensitivity at520-530 nm to record fluorescence for a blood

fluorescein mixture. The excitation and barrier filtersused are as previously described.7

This system provides a method of observing the dyetransit through the ocular circulations in both theanterior and posterior segments at the time of dyeinjection. Simultaneous video recording with astandard video cassette recorder gives a compactclinical record of archival quality. The stored data canbe quickly retrieved through a computerised dataretrieval autosearch control unit for routine clinicalevaluation and serial comparison. The dynamicsequence can be halted at any chosen stage for still-frame analysis (Figs. 2, 3, and 4; Table 2).

FUTURE APPLICATIONS

A further development has been the design of atelevision stereo ophthalmoscope to be used in con-junction with a computerised image analyser and datastorage bank. The video display system will performreal-time stereo data analysis and through ananalogue to digital converter will give a digital displayor paper print-out of optic disc cup volume. Thecomputer stored data would be used to detect volu-

Table 2 Manufacturers and suppliers ofequipment used

Television camerasLow-light-level, single-tube, Circon Corporation, 749 Ward Drive,colour television camera, with Santa Barbara, Ca 931 11. USAC-mount. reference MV 9295 (UK representative) Video South Ltd.

5 Kingsmead Square, Bath, AvonHitachi Denshi Model GP5 Hitachi Denshi (UK) Ltd, Lodge House,colour television camera Lodge Road, Hendon, LondonNW44DQBadger 25 SIT low light Alrad Instruments Ltd, 19a The Precinct.monochrome television camera Egham, Surrey TW20 9HNVideo tape recorderColour video cassette recorder.Sony U-Matic with still frame facilitiesand autosearch control unit Sony Company of Japan Ltd

Fig. 2 Stillfrom video recordingofnormalfluorescence angiogram.

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Video funduscopy and fluoroscopy

Fig. 3 Stillframe of irisangiogram showing dye entry andleakagefrom abnormal iris vesselsassociated with central retinal veinocclusion.

metric change in low-tension glaucoma, and as anadditional parameter to monitor long-term control inchronic simple glaucoma.

Discussion

Colour television funduscopy provides a method ofindividual and group viewing of the fundus, for thepurposes of consultation, teaching, or comparisonwith previous video recordings.

Television fluoroscopy has the unique advantage ofdynamic visual display of fluorescent dye entry, initialtransit, and recirculation within the ocular circulation,and the evolution of any abnormal extravascularfluorescence. The system is simple to operate for theophthalmologist without skilled technical assistance,

and it is particularly useful in smaller departments orthe consulting room without photographic dark-roomfacilities.Video cassette recording of data offers to the

clinician the availability of instant replay for detailedanalysis of any particular sequence. There is also thefacility of remote viewing in the consulting room,either at the time of fluoroscopy or by retrieval fromvideo records.

Considerable saving is made in running costs, in-cluding technicians' time carrying out dark-room pro-cessing, and in the cost of film materials as comparedwith video recording of an equivalent number ofpatients. Perhaps the most important consideration isthe high level of patient acceptability of a silent,low-light-level recording procedure which can be

Fig. 4 Stillframe ofappearanceofoptic nerve head during earlyvenousfillingphase ofdye transit ina case of central vasculitis, showingdye leakage and mural staining ofveins.

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performed with the minimum of stress and themaximum of convenience to both patient and doctor.

Electronic imaging can be further developedthrough computer technology to quantitative analysisof optic disc cup volume and measurement of retinalhaemodynamics.

References

1 Ridley H. Television in ophthalmology. Proceedings of the 16thInternational Congress of Ophthabnology. London: 1950: 2:1397-404.

2 Potts AM, Brown MC. A colour television ophthalmoscope.Trans Am Acad Ophthalmol Otolaryngol 1958; 62: 136-7.

3 Dallow RL. Television Ophthalmoscopy. Springfield: Thomas,1970.

4 Novotny HR, Alvis DL. A method of photographing fluorescencein circulating blood in the human retina. Circulation 1961; 24:82-6.

5 Haining WM, Wright MP, Perkins RE. Cinefluorography. RecentAdvances in the Technical Aspects of Fluorescein Angiography.Boston, Mass: Little, Brown. 1974; 14: 15-29.

6 Van Heuven WAJ, Schaffer C. Advances in televised fluoresceinangiography. International Symposium of Fluorescein Angi-ography, Tokyo. In: Fluorescein Angiography. Tokyo: IgakuShoin, 1973: 10-14.

7 Haining WM, Lancaster RC. Advanced technique for fluoresceinangiography. Arch Ophthalnol 1968; 79: 10-15.

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