Renaissance of the slit lamp (1911-2011)
Title: Renaissance of the slit lamp (1911-2011)
Key words: Videography, slit lamp, centenary, imaging, video slit lamp, recentration prism
Author: Marcus-Matthias Gellrich
Ophthalmological practice Germany
Tel 0049-4822-8326 or —30009
Soon after the introduction of the slit lamp by Gullstrand in 1911 1 the systematics for the use of the slit beam was established and — of course — is valid till now. 2 In the 1930-ies the principle of co-pivotal construction was established which means synchronization of the focus of the slit beam and the binocular ophthalmoscope and the slit lamp received its classic shape by Goldmann 3 and Comberg 4. In this time Vogt published his fundamental and comprehensive atlas on slit lamp biomicroscopy illustrated with beautifully drawn figures. 5
In 1953 a significant step in the clinical use of the slit lamp was prepared by the introduction of the fundus lens by el Bayadi. 6 Thereafter no major changes in the application of the slit lamp occurred and even modern video slit lamps concentrate on the classical field of this instrument which is documentation of diseases of the anterior segment and occasionally changes of the central fundus. 7
It is the aim of this article to point out, that one hundred years after the introduction of the slit lamp, this still most important instrument of practical ophthalmological work does not only offer the opportunity to carry out photodocumentation of the fundus, 8, 9, 10 and can also be helpful in follow up of glaucoma. 11. Moreover it can also be used for documentation of the whole face 12, 13, 14 and even strabological disease. 15 Furthermore we want to point out that the slit lamp offers a concept for documentation of nearly all ophthalmological diseases 16 if several basic principles and methods are applied. Their potential in the three main fields of ocular photography (anterior segment, fundus and face) will be evaluated for the slit lamp and compared to other diagnostic methods.
We practice photodocumentation of eye diseases using a video slit lamp (Zeiss, SL 105) with an inbuilt CCD-camera (Panasonic GP-KS 162 HDE, resolution 752 x 582 pixel). Video streams are recorded on a DVD recorder (Panasonic DMR-EX95V) and single pictures are stored on a compact flash-card as a JPG-file using a videoprinter (Panasonic MPD 7).
Retinal photographs were taken through a + 90 dpt hand held fundus lens and face photographs with additional minus lenses as reported previously (see also 4. bottom). 13
We characterize the photographic condition of a specific picture by giving the power of additionally used lenses (e.g. —10, —8, —6, +90 or 0 dpt if no lens was used) and the position of the magnification changer (5x, 8x, 12x, 20x, 32x).
The following six basic principles and methods will be applied to documentation of clinical findings with a video slit lamp.
Measurements with the slit lamp cannot only be carried out with inbuilt graticules, but also on the monitor screen connected to a video slit lamp. This can be easily done if a program like Measure (DatInf, Tubingen) is applied, which does not only allow measurements of distances but also of areas by manual drawings with the cursor on the screen. It is necessary, however, to calibrate the monitor.
2. Picture composites:
Composition of single pictures cannot only be used for comparison right / left or just «telling a short story with pictures» (see Figure 8). If single pictures are arranged in a topographically correct pattern they may form an overview which allows quick orientation in the clinical picture. While we carry out picture composition using the album function of our video printer (Panasonic MPD 7), it is one of the elementary functions of the program Microsoft Power Point.
Microsoft Power Point also allows to align similar pictures on consecutive foils which requires simple geometric operations (shift and rotation). This may be used for detection of change by quickly flickering between consecutive foils. Changes in the ocular tissue (e.g. a photography of the optic nerve) will become evident as virtual movement. 11
The plane of focus is generally set at approximately 10 cm in front of the objective of the slit lamp. This deliberate «shortsightedness» of the instrument can be overcome by simply holding a «correcting minus lens» in front of its objective (see Figure 6). 12, 13, 14 Thus with an e.g. — 8dpt lens the focus will be moved to 50 cm and much bigger objects than the eye can be recorded. This principle can be used either for photographies of face and squint, 15 but also for «scanning» of e.g. MRI print outs and a probe of a child’s handwriting if dyslexia if the major problem (see also Figure 8, bottom).
5. Sequential analysis:
With our video slit lamp pictures are recorded at a rate of 24 frames per second. The quick search and the single step mode allow to select appropriate single pictures among long sequences. This is particularly valuable if findings have to be documented which last only parts of a second or if the patient’s eye is very unsteady during the examination.
For each clinical finding the adequate illumination has to be considered. It will become evident that the fundamental theory of direct and indirect illumination is suitable for documentation of anterior segment disease 7 but not sufficient for recordings of the fundus and face.
In the following the possible use of the above indicated six basic principles and methods will be elucidated for slit lamp photography of the anterior segment, fundus and face (see also Table 1). Examples will be given
1. Pupillary and corneal diameter (e.g. for fitting of contact lenses) can be easily measured with the slit lamp. Also the axis of stabilization of a toric lens can be determined.
The slit lamp, however, may also be used to estimate corneal thickness: If a thin slit beam passes through the corneal center under an angle of 45° it will be deflected. The visible width of the slit beam within the cornea is proportional to the thickness of the cornea (Figure 1). 11 It is necessary to calibrate the monitor for measurements with this procedure.
2. Composition of pictures in a topographical pattern is valuable for a complete overview of the sclera / conjunctiva including the areas hidden under the lids on primary gaze.
In corneal disease there is sometimes the problem that not all parts of the cornea can be photographed sharp. 3x3 arrangements (at high magnification, e.g. 20x) are helpful for limbus overviews and proper visualization of the trepanation scar after keratoplasty
Also complete overviews of the chamber angle may be created easily with this method (Figure 2).
3. An interesting field for the flicker-test is the pupillary reaction. It is often impossible to determine by looking simultaneously on consecutive pictures of a video stream (recording rate 24/sec) whether there is any difference in pupil size. Flickering, however, between two adjacent frames usually makes differences very clear by a visible movement of constriction of dilatation.
Assessment of change in e.g. iritis and nuclear cataracts could also benefit from this procedure, but it requires a standardized setting particularly of the angle of the slit beam towards the cornea which we carry out at 45° for Tyndall’s phenomenon and at 30° for the bigger lens.
4. The principle of scanning with the slit lamp can be applied if e.g. print outs of corneal topography are available.
5. The sequential analysis is very helpful for evaluation of pupillary reaction (direct and looking for relative afferent defect). In particular the condition of the pupil «at dark» can be captured in the following way: Focus of the slit lamp is on the iris at intermediate magnification (e.g. 12x) — the light is turned off (see also 6. down) allowing the pupil to dilate — the light is suddenly turned on inducing light reaction, but this starts with a latency of approx. 0.2 sec. It is easy (using the single step mode) to find the first frame within the video sequence (frequency 24 Hz) at full exposition of light and take this for the pupil «at dark».
For testing of relative afferent defect we swing a light cone of the ophthalmoscope (see 6. down) from the contralateral eye to the eye which is in focus of the slit lamp and take the first frame after full exposition of light and the 16th frame (0.6 sec later) as the basis for documentation of relative afferent defect. Usually this procedure is carried out in the same way for the right and the left eye and evaluation is with the flicker-test as mentioned above (see 3.).
6. Apart from what has been established knowledge on slit lamp illumination for nearly a century now, the need for an additional light source is acknowledged, 7 particularly if the lids have to be photographed at sufficient quality. For the swinging flashlight test, if carried out at a slit lamp as indicated under 5. above, a rather mobile external light, is required and to our experience the light cone of an ophthalmoscope fulfils this need.
1. The size of the optic disc can be determined by marking the outline of the papille on the monitor and applying a geometric analysis program as e.g. Measure (DatInf). It is necessary to know the magnification factor of the fundus lens used (e.g. 0.76 for +90 dpt) 17, but additional calibration of the monitor based on data acquired with a different measurement technique (e.g. HRT) is advisable. Distinction between normal, macro— and micropapilla is thus easy to make.
2. Using a fundus lens the posterior pole of the eye including optic disc and macula can often not be visualized satisfactorily in a single slit lamp photography (disturbing reflexes, poor resolution). Therefore it is advisable to take a picture of the optic disc and the macula separately. Using Power Point these two photographic segments may be adjusted to form one composite with sufficient clarity of the posterior pole (Figure 3).
Composition of single pictures in a topographical pattern also allows to build up panfundus overviews: Using a fundus lens the patient is asked to look into the nine main directions of gaze and the pictures are assembled in a 3x3 pattern as shown in Figure 4a. 8, 9, 10 Parts from a whole fundus which are relevant for an actual disease, of course, can be extracted s can be seen in Figure 4b.
3. The flicker-test is particularly valuable for judgement on many retinal processes by comparing adjusted photographs of the same area taken at different times. Changes in size and shape of a chorioidal nevus, can be visualized as well as macular changes like atrophy of pigment epithelium or the outline of subretinal fluid in central serous retinopathy. Retinal small vessels are very useful hallmarks to detect secondary changes induced by contraction of epiretinal membrane in macular gliosis but also the sudden uprise of perimacular edema induced by subretinal neovascularisation.
These small vessels also show virtual movement on adjacent foils of Power Point if the shape of the cup of the optic nerve changes with time by loss of nerve fibre tissue. This observation can be used for follow up in glaucoma with the slit lamp (Figure 5): Clinical deterioration can be witnessed by the nerve fibres melting away if — as in a thumb cinema — flickering through several slit lamp photographies of the optic disc at high magnification (e.g. 32x) taken over the years. 11
4. Patients with macular or glaucoma problems often carry print outs of HRT, OCT or GDx examinations. Relevant parts may be scanned with the slit lamp. Also Amsler charts and even fundus drawings can be scanned.
5. Sequential analysis of video recordings is clinically important for slit lamp photography of the fundus, because unrest of the patients’s eye during the examination with a hand held lens makes the «optimal shot» a rare event within a sequence. These best pictures can be easily selected using quick search and the single step mode of a DVD recorder.
6. Fundus photography with the slit lamp greatly benefits from the combined use of white and green light. White light is advantageous for pigment changes as in chorioidal nevi or laser scars, whereas green light is preferable for macular changes as drusen and gliosis but also often shows small vessels at better contrast (see Figure 3 and 5).
To obtain face photographies it is necessary that the patient leans back from the chin rest at about 50 cm distance. With a hand held —8 dpt lens in front of the objective of the slit lamp (see Figure 6 and 7) the plane of sharp focus of the slit lamp is set accordingly. 13
1. Measurements of interpupillary distance can be carried out with the slit lamp (e.g. magnification changer at 8x and —8 additional lens in front of the objective) on the video monitor.
2. The nine gaze composite is a clinically valuable application of picture composition. It may be modified, however, to the three horizontal positions to save time and just show e.g. sursoadduction (see. Figure 7 b).
3. The flicker-test may be used to demonstrate to a patient convincingly e.g. the fusional alignment of the abducted eye in intermittent divergent squint. Also very small movements as the occur in microstrabism can be made visible if an assistant familiar with the cover test is available.
4. It is advisable to scan a patient’s old photographies if e.g. the course of Grave’s disease is to be evaluated or if parents bring pictures documenting their child’s squint. Also scanning with the slit lamp of a handwritten scheme of nine gaze angle measurements under dark red glass is a possible (and clinically relevant) form of documentation of disease (see also Figure 8).
5. Certain clinical findings as blepharospasm, blinking tic and many forms of nystagmus are most adequately documented in a short video sequence rather than in »frozen pictures». Using video sequences is also valuable if a «golden moment» has to be captured which only lasts part of a second. This may be generally the case for squint photography in children who are very mobile, but also if very short lasting positions of the eyes have to be documented — as may be in intermittent divergent squint or dissociated vertical divergence.
The same setting may be used for testing of anisocoria. The phase «pupils at dark» can be monitored in the following way: The patient is reclined at about 50 cm from the slit lamp objective. He looks into the light of the slit beam which is aligned by the recentration prism (see Figure 6). Then an assistant covers the slit with an occluder allowing the pupils do dilate. Shortly thereafter the occluder is removed suddenly on command of the examiner inducing bilateral pupilary constriction. As is suggested for single pupil testing (see anterior segment 5.) the first picture with light exposure of the eye may be taken as «pupils at dark».
6. Face photography with the slit lamp requires diffuse intense light. This may be achieved by a bright halogen lamp installed at the ceiling or shining from frontal oblique.
We prefer the following technique using the slit beam not only to enlighten the face but also to induce reproducible corneal reflexes which are important for squint-photography: The binocular microscope is in middle position. The arm taking the slit illuminator is shifted approx. 5-10° to the left (if the video camera is attached to the right ocular) to allow for the free view through the slit lamp. If the patient is reclined about 50 from the objective of the slit lamp the slit beam projects now temporally from his left ear. While the examiner’s right hand holds the —8 dpt lens in front of the objective of the slit lamp the let hand holds a prism of approx. 14 pdpt basis 180° in front of the slit beam to redirect it onto the patient’s face (We therefore call this prism «recentration prism» — see Figure 6). This usually induces some blinding which is to be reduced with the slit diffuser. In primary gaze central corneal reflexes are now visible (Figure 7) and the picture quality my sometimes be enhanced by bringing the slit into a horizontal position. 15
Pictures are often more precise than a description with words or a drawing. They may serve as a basis for explanations to the patient and also help the ophthalmologist to quickly «get into the case». 18, 19 Today large well organized electronic archives are available with huge storage capacities and photographs may be sent around the world within seconds for consultation of colleagues. 20
We present a concept enabling the user of every video slit lamp to put ophthalmological findings into pictures. 16 This concept has evolved over a ten years period of practical work with a video slit lamp.
Additional requirements as we suggest them are readily available: + 90 dpt lens (or e.g. +60, +78) for fundus examination and —10, —9, —8, —7 and —6 dpt minus lenses for face photography. 13, 14 (Minus lenses with lower power do not offer a real advantage to the conditions of normal slit lamp examination). Finally we suggest a recentration prism of approx 14 pdpt which may be taken from the prism trial set as may the minus lenses be taken from the set of trial lenses (see Figure 9).
Video sequences are stored on a freely available DVD recorder. Suitable pictures are stored in JPG format on a Compact Flash card. For further picture work up we use generally available computer programs as Power Point and Measure (DatInf). Import of pictures into the practice program is with the command «copy» by Microsoft.
Thus our concept is not only independent from a specific type of video slit lamp, but also from specific programs for picture work up which are now regularly offered with modern video slit lamps. So far, however, we have not seen a specific solution on the market fulfilling all the needs we consider necessary for carrying out a comprehensive video-ophthalmology with the slit lamp as suggested here. It is not only our hope that this will change, but also that our concept will benefit from the higher resolutions achieved by modern video slit lamps in comparison to the material we show here..
Our concept for imaging of eye diseases is unique in so far that we suggest a solution based on one instrument for nearly all ophthalmological diseases. This is very much in contrast to present developments characterized by an exploding market in ophthalmology for eye imaging. 19, 21, 22 It is essential to know these new developments and to make clear that for every solution we offer there is at least one (sometimes plenty) working with higher resolution and broader information, but also at much higher prices and with the general problem to bring the patient to the special instrument at a time when this is available for clinical work.
We cannot discuss in detail all the methods available in comparison to what we suggest, but will concentrate on a few ones we consider as particularly relevant.
Imaging of anterior segment
With photo slit lamps using flash photography higher accuracy of the single picture may be achieved. 7 Professional photo slit lamps, however, are usually much more difficult to handle. Usually they are an extra device while the concept as we suggest it implies that acquisition of picture material is almost a part of the clinical examination.
Measurement of corneal thickness with the aid of the slit lamp has been available already a long time. 22 It does, however, require additional equipment which has to be connected temporarily to the slit lamp. Nowadays ultrasound or optical pachymeters usually give accuracies up to 1/1000 mm. This is far above the precision of our method which does not need additional devices and uses an oblique thin slit through the central cornea at a fixed angle. We are, however, able to distinguish abnormally thin from normal or abnormally thick corneas (see Figure 1). 11 For clinical purposes this is a sufficient basis to make corrections for ocular pressure 23 or give advice concerning the possibility of refractive excimer treatment.
Pupillary reaction is usually evaluated with a pupillometer relying on infrared techniques. 22 We use the «effect of the red eye» due to the latency of pupillary reaction to determine the pupillary width «without light» using the sequential analysis of video streams.
This method also allows to test for afferent pupillary deficit in which subtle changes can be visualized with the flicker-test.
The classical 30-60 degree fundus photography has influenced our perception of retinal photography for decades. 24 Thus an overview usually shows the optic disc and the macula at good contrast in white light. 20, 21 Due to disturbing light reflexes and decreasing resolution at lower magnifications it is, however, not possible to make comparable photographs with the slit lamp in one picture. It is a good alternative therefore to divide the posterior pole in a macula and a disc area and later bring these images together (see Figure 3). Red free light does not only probably lower the risk of macular damage 25, but also brings out many retinal structures much clearer. 26, 27
Peripheral findings are sometimes beyond the reach of a classic fundus camera, but can be photographed at the slit lamp with good examination technique and a hand held fundus lens (see Figure 4). 8, 9, 10
While Optomap offers visualization of the retina up to 200° and claims to cover 82% of the retina 28 with our 3x3 arrangements of fundus patches (see Figure 4) we can calculate the area covered as follows: We assume the whole inner eye to be a globe and the diameter of the single patch of retina covered by the slit beam as 45° (at 12x magnification). If we apply the rules of spherical geometry we may calculate the part of the surface of that eye globe covered by a 45° angle of view from (1-cos22.5°):2 which is 3.81%. If we create a 3x3 «panretinal» image the maximum percentage covered could reach 34.3%, but this is an upper limit due to the non linear projection in an eye 29 and the fact that there may be overlap between single pictures (see Figure 4). Considering the fact that 72% of the inside of the globe is retina 30 the «panretinal» image as we suggest it covers only up to 47 % of the retinal area.
To our knowledge «panretinal» composites based on slit lamp photographs have not been introduced so far. 31 Even though parts may be missing their topographical information over the whole retina is particularly helpful in assessment of retinal detachment and its treatment. For documentation of diabetic retinopathy and occlusive vessel disease we choose a higher magnification (20x) which shows more detail of retinal tissue. According to the clinical relevance we also put the focus on the mid rather than the far periphery. So far, however, we do not carry out adaptation of all neighbouring pictures in 3x3 arrangements, which would in general be possible with PowerPoint. We still regard it as too time-consuming for practical work while we suggest it for the easier situation of the posterior pole (1+1 arrangement, see Figure 3).
Autofluorescence is an uprising technique especially revealing disease of the retinal pigment epithelium. 32 With the slit lamp it is very often worthwhile to examine a special retinal area not only with white, but also with red free light. Green light was suggested already in the early times for examination of the central retina 26, 33 and is particularly helpful for slit lamp photography of conditions as macular drusen or geographic atrophy.
Changes in certain macular pathologies, especially age related macular degeneration and epiretinal membranes, but also central serous retinopathy can be followed up by applying the flicker-test for comparisons between consecutive examinations. Cases of unexplained decrease of visual acuity, however, especially when subretinal pathology is considered as in occult subretinal membranes and fine cystoid edema, should be sent for OCT examination. Sometimes it depends on clinical experience: Subtle, yet typical changes on biomicroscopy in a boy with visual reduction to 0.3 may arouse suspicion of X-linked retinoschisis, but performing OCT for this occasion can help to eliminate final doubts. 34
Likewise is the flicker-test very valuable in monitoring progression of disc cupping in glaucoma. Seeing the actual process over years condensed to a sequence of seconds, gives a clinical feeling of what is going on with the nerve fibres. The slit lamp, of course, equally shows peripapillary atrophy and splinter hemorrhages. The latter may escape a laser tomographic scanner examination of the optic nerve head which from the theoretical concept is a more precise instrument to detect glaucomatous changes than the slit lamp. 35
This flicker-procedure for follow-up in glaucoma is already known and was found to be valuable for classical photography of the optic nerve head. 36, 37 Having primarily digital data and with the properties of the program Power Point, as we apply it, the procedure, however, seems to be easier than in earlier studies using fundus slides. Also being able to determine the size of the optic disc 17 and give an estimate of the central corneal thickness 11 makes the slit lamp examination a single event acquisition of data relevant for glaucoma, including Goldmann applanation tonometry.
Angiography is still the gold standard for microvascular changes in retinal disease. 21 Microaneurysms and hard exudates are visible at good contrast if red free light is applied at higher slit lamp magnifications (20x). Central ischemia is often preceeded or accompanied by cotton wool spots which are readily identifiable on slit lamp photographs whereas peripheral ischemic zones, however, cannot be visualized adequately on slit lamp photographs.
Face photography has never been so easy as nowadays with the availability of digital cameras. Therefore one might question the need to carry out face photography with the slit lamp which is simply done by putting minus lenses in front of the objective and bringing the patient in the appropriate distance. This method has been introduced by us recently. 12, 12, 14 The use, however, of a standard video or photographic camera — especially with a flash— immediately leads to an artificial situtation of being portraited and may alter the patients’ (particularly children’s) behaviour. 38 This is, however, not the case in face photography with the slit lamp as we suggest it.
We perform strabological photography with the slit lamp by fixed combinations of the magnification changer (e.g. 8x) and the minus lens in front of the objective (e.g. —8 dpt with the patient at 50 cm distance). The use of the slit light for illumination of the patient’s face has already been suggested in earlier times. 4 We carry this idea further to generate — solely based on the slit beam — also corneal reflexes which are right in the center of the pupil at primary gaze. 15 At present we hold a minus lens in the right hand and the recentration prism in the left hand which may sound difficult, but this procedure is certainly easier to learn than indirect ophthalmoscopy or examination with a gonioscopic lens. For convenience, however, we propose that the recentration prism which simply requires the two positions «in» or «out»should be installed — like the diffuser — near the slit beam from where it can be brought easily into the right position.
Who in the end would have expected a highly standardized photographic procedure coming from the slit lamp while there is still no mutual standard for strabology photography in general (distance, light for corneal reflexes) ? 39, 40
Photographing very small and very mobile children with the slit lamp, however, needs special procedures — seeting on extra cushions (see Figure 6) or the child even held upright standing by their parents. 41 Sequential analysis of video streams regularly allows to take a typical picture showing the binocular situation. 10, 15
While there is usually no need for an assistant in photography of the anterior segments and fundus good results in strabological photography depend on good cooperation between the examiner at the slit lamp and an aid carrying out cover tests, holding a patient’s upper lids (see Figure 6) or helping to bring the patient’s head in the right position e.g. for the Bielschowsky inclination test.
Clinical experience shows that a picture of the Bielschowsky test gives more information in mild trochlear palsy than a nine gaze composite. Since trochlear palsy and mild abducens palsy may be monitored more accurately with angle measurements under dark red glass than by photography of squint we altered our concept for documentation of these conditions to scanning of these measurements — handwritten on a sheet of paper — with the slit lamp.
In general does « scanning » with the slit lamp very often require minus lenses due to the size of the object to be scanned which often exceeds that of a the lid rim. Of course, may long written textes and detailed print outs of fundus imagings or even fundus drawings be captured at higher quality with a conventional scanner. We see the advantage of our method in its high versatility not only concerning the size but also the nature of the object which is to be scanned : E.g. if a patient shows a photography he took from a special eye condition with a mobile phone this can be « scanned » easily using the slit lamp. 14
Having more experience with the method we suggest should lead to a deliberate use of simple optical rules of correctional minus glasses: For adequate photography of head tilt of course a larger area has to be shown requiring a larger distance between patient and the slit lamp objective and thus a higher power minus lens (e.g. patient at 1 m, —9 dpt lens and magnification at 5x). For photography of periocular xanthelasmas the lowest normal (= without minus lens) slit lamp magnification may not show the full area, but a setting with a — 6 dpt lens, 8x magnification and the patient at 25 cm distance would be a good choice.
Moreover increasing the distance between a given minus glass and the slit lamp objective (= less minus power) shifts the plane of sharp focus a little nearer towards the objective. This allows for slight adjustments if the patient is not seated exactly in the correct plane of focus. Also the prismatic effect of a high minus lens can be applied to optimize the position of a face towards the center of the monitor.
Being completely aware of the limitations in quality of our methods we nonetheless offer a concept which claims to have a photographic solution for nearly every eye disease only by using a video slit lamp. This means that if a patient suffers from strabism, cataract and macular disease imaging can be carried out by one instrument. 16 This is done without shifting the patient from one diagnostic station to the other, at little expense and does not take a lot of time. Disturbance of the workflow by imaging procedure can even be minimized if relevant parts of the examimation are recorded in a videosequence and appropriate pictures are selected thereafter. 8,12 The more standardized procedures are used the easier it is for anyone — not necessarily being the examiner — to capture relevant pictures.
Wherever professional photographic units are available and there is access to the repertoire of modern retinal diagnostics there is no need to apply our — sometimes basic — methods. In fact, only a minority of the ophthalmologists worldwide are in such a favourable position, and even then there may be occasions when the instruments are there but canot be applied appropriately. A video slit lamp with some additional equipment and clear concepts what has to be done in which situation enables every ophthalmologist to give a basic recording of any clinical finding — 24 hours a day.
What we suggest for the use of a video slit lamp by far exceeds the classical theory of slit illumination techniques. 2, 7, 42 We call the methods applied collectively as videography with the slit lamp 11, 14, 15 — among them digital photography and computer programs for picture work up. 20 Those who introduced and optimized the concept of the slit lamp did everything which was possible at their time. 1, 3, 4 These pioneeers — living today — would undoubtedly not hesitate to improve and broaden the use of our still most important instrument in ophthalmology. So let’s, continue their work, wipe the dust away from the slit lamp and make it ready for the next hundred years !
1. Gullstrand A. Die Nernstspaltlampe in der ophthalmologischen Praxis. IV. Jahresversammlung des schwedischen augenarztlichen Vereins, Stockholm 1911 (translated by Fritz Ask) Klin Monatsbl Augenheilkd 1912;50: 483-484.
2. Heydenreich A. Untersuchungsmethoden. In: Velhagen K, editor. Der Augenarzt (2). Stuttgart: Georg Thieme, 1959: 45-50.
3. Goldmann H. Eine neue Spaltlampe. Klin Monatsbl Augenheilkd. 1933;91:494-502.
4. Comberg W. Uber eine neue Spaltlampe. Klin Monatsbl Augenheilkd. 1933;91: 577-583.
5. Vogt A. Lehrbuch und Atlas der Spaltlampenmikroskopie des lebenden Auges. Part I-III. Berlin: Julius Springer, Stuttgart: Ferdinand Enke, 1930, 1931,1942:1-1091.
6. El Bayadi G. New method of slitlamp micro-ophthalmoscopy. Br J Ophthalmol. 1953;37:625-628.
7. Martonyi CL, Bahn CF, Meyer RF. Slit Lamp: Examination and photography. Sedona: Time One Ink, 2007:1-149.
8. Gellrich M-M. Yes, we can. Deeper (retinal) insights of a slit lamp. 2009;Video presented at
Meeting of the Deutsche Ophthalmologische Gesellschaft in Leipzig 2009
Belretina conference in Minsk 2009
Filatov conference in Odessa 2010
9. Gellrich M-M. Netzhautfotografie mit der Videospaltlampe — alles geht. Z prakt Augenheilkd. 2009;30:372-378.
10. Gellrich M-M. Comprehensive fundus photography with the slit lamp. Ars medica. 2009;19:11-17.
11. Gellrich M-M. Die Spaltlampe — Konstruktionsgeschichte, Untersuchungsmethoden, Videografie. Heidelberg, Kaden, 2011; 1-194.
12. Gellrich M-M. A slit lamp overcomes its shortsightedness. 2007; Video presented at
Meeting of the Deutsche Ophthalmologische Gesellschaft in Berlin 2007
Mieeting of the Societe Francaise d’Ophtalmologie in Paris 2008
Meeting of the Royal College of Ophthalmologists in Birmingham 2009
Available on the video platform of the DOG and the SFO
13. Gellrich M-M. A new view of the slit lamp. Br J Ophthalmol. 2009;93:272-273.
14. Gellrich M-M. Centenary of the slit lamp, 2011; Video presented at the Meeting of the Deutsche Ophthalmologische Gesellschaft in Berlin 2011, Meeting of the XIIth International Annual Congress „Modern Technologies in cataract and refractive surgery — 2011» in Moscow
15. Gellrich M-M. Videografie mit der Spaltlampe, Klin Monatsbl Augenheilkd, in press.
16. Gellrich M-M. Comprehensive imaging in ophthalmology using a video slit lamp. J Ophthal Photog. 2009;31: 110-115.
17. Haustein M, Schmidt E, Sporl E, Pillunat LE, Bohm AG. Flachenbestimmung der Papille mittels indirekter Ophthalmoskopie. Ophthalmologe. 2009;106:141-148.
18. Meyer-Schwickerath GRE. Ophthalmology and photography. Am J Ophthalmol. 1968;66:1011-1019.
19. Wolffsohn J. Eye essentials. Ophthalmic imaging. Edinburgh: Elsevier. Butterworth Heinemann, 2008:1-172.
20. Tyler ME, Saine PJ, Bennett TJ. Practical retinal photography and digital imaging techniques. Philadelphia: Butterworth Heinemann, 2003: 1-222.
21. Saine PJ, Tyler ME. Ophthalmic Photography: Retinal Photography, Angiography, and Electronic Imaging. Boston: Butterworth-Heinemann, 2002: 1-398.
22. Kroll P, Kuchle M, Kuchle HJ. Augenarztliche Untersuchungsmethoden. Stuttgart: Thieme, 2008:1-620.
23. Kutschan A, Schroeder B, Hager A, Dave H, Wegscheider K, Wiegand W. Correction factors for central corneal thickness in Goldmann applanation tonometry. Ophthalmologe. 2010;107:30-35.
24. Allen L. Ocular fundus photography. Am J Ophthalmol. 1964:57: 13-28.
25. Kohnen S. Light-induced damage of the retina through slit-lamp photography. Graefe`s Arch Clin Exp Ophthalmol. 2000;238:956-959.
26. Vogt A. Die Reflexion der Netzhautvorderflache im rotfreien Licht. Praretinale (superfizielle retinale) Faltchenbildung. Klin Monatbl Augenheilkd. 1921;66:838-859.
27. Vignal R, Gastaud P, Izambart C, Daubas P, Freton A. Improved visualization of fundus with green-light ophthalmoscopy. J Fr Ophtalmol. 2007; 30: 271-275.
28. Sherman J, Karamchandani G, Jones W, Nath S, Yannuzzi L. Panoramic Ophthalmoscopy. Optomap images and interpretation. Slack, Thorofare, 2007:1-230.
29. Drasdo N, Fowler C W. Non-linear projection of the retinal image in a wide-angle schematic eye. Br J Ophthal. 1974;58:709-714.
30. Michels RG, Wilkinson CP, Rice TA. Retinal detachment. The C.V. Mosby Company, 1990.
31. Hackel RE, Saine PJ. Creating retinal fundus maps. J Ophthal photog. 2005;27:10-18.
32. Schmitz-Valckenberg S, Fleckenstein M, Gobel AP, Sehmib K, Fitzke FW, Holz FG, Tufail A (2008). Evaluation of autofluorescence imaging with the scanning Laser ophthalmoscope and the fundus camera in age-related geographic atrophy. Am J Ophthalmol. 2008;146(2):183-192.
33. Gullstrand A. Die Macula centralis im rotfreien Lichte. Klin Monatsbl Augenheilkd. 1918;60:289-324.
34. Yu J, Ni Y, Keane PA, Jiang C, Wang W, Xu G. Foveomacular schisis in juvenile X-linked retinoschisis: An optical coherence tomography study. Am J Ophthalmol. 2010;149 (6): 973-978
35. Dreher AW, Tso PC, Weinreb RN (1991) Reproducibility of topographic measurements of the normal and glaucomatous optic nerve head with the laser tomographic scanner. Am J Ophthalmol. 1991;111:221-229.
36. Heijl A, Bengtsson B. Diagnosis of early glaucoma with flicker comparisons of serial disc photographs. Invest Ophthalmol Vis Sci. 1989;30(11):2376-2384.
37. Berger JW, Patel TR, Shin DS, Piltz JR, Stone RA. Computerized stereochronoscopy and alternation flicker to detect optic nerve head contour change Ophthalmology. 2000;107(7):1316-1320.
38. Szirth BC, Kimm GL, Murphree AL. Flash selection in strabismus fotography. J Ophthal Photog 1986;9: 60-63.
39. Kaufmann H. Strabismus. Stuttgart: Thieme, 2003;1-594.
40. Lyle TK. Worth and Chavasse’s squint. London: Bailliere, Tindall, Cox, 1950: 1-319.
41. Szirth BC, Murphee AL, McNamara W. Infant fundus photography. J Ophthal photog. 1985; 8:30-33.
42. Doshi S, Harvey W. Eye essentials. Assessment & investigative techniques. Edinburgh: Elsevier. Butterworth Heinemann, 2005:1-186.
FIGURE 1. Three corneae with known thickness from pachymetry (thick = 650, normal = 540, thin = 435 um). The slit beam is projected under an angle of 45° through the central cornea (magnification changer 32x). Visible width of the slit beam is proportional to corneal thickness, thus allowing estimation of central corneal thickness with a video slit lamp.
FIGURE 2. Composite of single pictures for reconstruction of the chamber angle which shows circular hyperpigmentation. In the center contact glass with magnification changer 5x, all other frames contact glass view with magnification changer 32x.
FIGURE 3. Reconstruction of the posterior pole in a patient with macular drusen. Two fundus segments arranged with Power Point (green light, + 90 dpt lens, magnification changer 20x)
FIGURE 4a. Composite of a ‘panfundus’ image consisting of 9 fundus sections (magnification changer 12x). Each photograph is taken with the slit lamp in different viewing directions (see small insets — fundus section top left in the figure, showing the lower temporal quadrant, a result of the patient looking to the bottom left, etc.). Individual pictures are inverted (as seen through the + 90 dpt lens) and so is the ‘panfundus’ composite. Thus, a general overview of the retina of the left eye with an encircling buckle is obtained.
FIGURE 4b. Composite of fundus sections of a left eye showing simultaneously posterior pole and peripheral foramen in 9 o’clock position (pictures upside down) shortly after laser coagulation.
FIGURE 5 Nearly ten years follow up of right optic disc (inverted) in a patient with normal tension glaucoma (green light, + 90 dpt lens, magnification changer 32x). Increase in peripapillary atrophy and visibility of small vessels at the bottom of the cup is evident by comparing static pictures. The loss of nerve fibre tissue, however, resulting in a shift of all the small vessels towards the edges of the cup is much more obvious by flickering through consecutive Power point foils as in a «thumb cinema».
FIGURE 6. Setting for portrait and strabological photography with the slit lamp: Examination distance is larger than usual (in this case 50 cm). The arm holding the slit illuminator is rotated slightly to the left to allow for undisturbed view through the slit lamp
View through the slit lamp is visible on the monitor in the upper left edge of the picture. Inset shows view of the patient: The examiner holds with the right hand a — 8 dpt lens in front of the slit lamp objective. In the left hand (especially in strabological photography) a horizontal recentration prism (14 pdpt base 180 °) is held, that directs the light of the slit lamp on the patient. This results in sufficiently intense illumination of the face and visible corneal reflexes — see Fig. 7.
FIGURE 7. (Same girl as in Fig 6) Picture is taken with a —8 dpt lens and magnification changer 8x
Fig. 7a. Corneal reflex generated by the slit lamp light used for illumination clearly indicates strabism.
Fig. 7b. 9-gaze arrangement, which can easily be done with Microsoft Power Point showing that there is also sursoadduction on both eyes.
FIGURE 8. Picture composite illustrating a case of hysterical blindness. All the photographies are taken with a video slit lamp (-8 dpt lens and magnification changer 8x). Bottom pictures are an example for «scanning» with the slit lamp. A young lady (top left) claimed not to see anything on the visual acuity charts presented (bottom left — Cardiff test chart at high contrast). So we applied the principle of preferential looking and she perfectly fixated the objects shown, even at very low contrasts (bottom right). The psychological element of that condition is reflected by the large mood change visible on the expression of the face (top right) after being told that there surely is no blindness.
FIGURE 9. Additional requirements for videography with the slit lamp: + 90 and +60 dpt lens (or e.g. +78) and contact glass for fundus examination and —9, —8 and —7 minus lenses for face videography. Also there is a recentration prism of approx 14 pdpt for creating central corneal reflexes.