[Slit lamp photography with the Haag-Streit slit lamp 900].
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Adult↗
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[Slit-lamp photography with the Haag-Streit 900 slit lamp].
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Fundus Oculi↗
On focusing the slit-lamp: Part II. "The fading-slit test"--verifying the ocular setting.
The focusing-rod test is considered the gold standard for determining the correct setting of the slit-lamp ocular rings. This method is, however, somewhat time-consuming, considering the time it often takes to locate a rod every time one switches between slit-lamps or slit-lamp-mounted lasers. In this article we present an alternative test, which we call the fading-slit test, that requires only a second to perform, does not involve additional equipment (such as a rod), and can be applied at any time during the slit-lamp examination. However, while the focusing-rod test determines what setting should be used, the fading slit test can verify only whether the current setting is indeed the correct one and, therefore, it is not a complete substitute for the focusing-rod test. The fading-slit test is performed as follows: while focusing on any approximately flat surface (even the center of the patient's dome-shaped cornea would do) and using oblique illumination, gradually reduce the slit width until it disappears. Pay attention to whether the slit continuously thins, reaching a hairline width prior to its disappearance or, alternatively, whether, just before disappearance, the slit remains somewhat wide, gradually fading away, instead of thinning away. In the former case the ocular setting is correct; in the latter case it is incorrect.
Calibration↗
An accessory fill-in flash for the Nikon photo-slit lamp.
High-quality slit lamp photographs require a balance between slit beam exposure and exposure of surrounding ocular structures. Proper exposure of surrounding ocular structure is difficult to obtain with the Nikon photo-slit lamp. The purpose of this research was to design an accessory fill-in flash for this slit lamp, which would provide proper exposure of over all ocular structures. In addition, this paper describes the procedures used to obtain proper exposure values and provides an exposure table for this accessory flash unit.
Eye↗
Slit lamp laser Doppler interferometer.
A slit lamp laser interferometer is described for clinical in vivo eye length measurements. The basic components are a laser Doppler interferometer, a slit lamp attachment, and a commercial slit lamp. First measurements of the axial length of the eye yielded a standard deviation of 0.04 mm and less.
Eye↗
Slit lamp classification system.
A slit lamp classification system is presented which follows the same divisions as the FDA Slit Lamp Classification System but expands the number of categories. It also differs in that there is an orderly progression of the various findings and a numbering system which allows for easy statistical analysis. In this way, the incidence of findings may be grouped according to degree of severity, and may be easily compared across different categories.
Conjunctival Diseases↗
Photometric oculometry. I. An analysis of the optical principles in slit-lamp fluorophotometry.
The optical principles of slit-lamp fluorophotometry are analysed by aid of a mathematical model of the optical system. The analysis forms the theoretical basis for a slit-lamp technique called photometric oculometry, which makes possible an estimation of intraocular axial distances and axial length. The technique is based on a calculation--by aid of a mathematical model of the eye--of the ratio between intraocular movement of the slit-lamp focal plane and corresponding movement of the slit-lamp. Intraocular axial distances can be calculated by aid of this ratio and a direct measurement of the slit-lamp movement when the focal plane is moved in the optical axis from retina to cornea. These items are prerequisites for a quantitative determination of the blood-retinal barrier permeability to fluorescein during vitreous fluorophotometry.
Eye↗
Mosaicking and enhancement of slit lamp biomicroscopic fundus images.
AIMS: To process video slit lamp biomicroscopic fundus image sequences in order to generate wide field, high quality fundus image montages which might be suitable for photodocumentation. METHODS: Slit lamp biomicroscopic fundus examination was performed on human volunteers with a contact or non-contact lens. A stock, charge coupled device camera permitted image capture and storage of the image sequence at 30 frames per second. Acquisition time was approximately 30 seconds. Individual slit lamp biomicroscope fundus image frames were aligned and blended with custom developed software. RESULTS: The developed algorithms allowed for highly accurate alignment and blending of partially overlapping slit lamp biomicroscopic fundus images to generate a seamless, high quality, wide field montage. CONCLUSIONS: Video image acquisition and processing algorithms allow for mosaicking and enhancement of slit lamp biomicroscopic fundus images. The improved quality and wide field of view may confer suitability for inexpensive, real time photodocumentation of disc and macular abnormalities.
Algorithms↗
Automated, real time extraction of fundus images from slit lamp fundus biomicroscope video image sequences.
AIMS: Slit lamp fundus biomicroscopy allows for high magnification, stereoscopic diagnosis, and treatment of macular diseases. Variable contrast, narrow field of view, and specular reflections arising from the cornea, sclera, and examining lens reduce image quality; these images are of limited clinical utility for diagnosis, treatment planning, and photodocumentation when compared with fundus camera images. Algorithms are being developed to segment fundus imagery from slit lamp biomicroscopic video image sequences in order to improve clinical utility. METHODS: Video fundus image sequences of human volunteers were acquired with a video equipped, Nikon NS-1V slit lamp biomicroscope. Custom developed software identified specular reflections based on brightness and colour content, and extracted the illuminated fundus image based on colour image analysis and size constraints. RESULTS: In five subjects with variable image quality, the approach allowed for automatic, robust, accurate extraction of that portion of the video image corresponding to the illuminated portion of the fundus. Non-real time analysis allowed for fundus image segmentation for each frame of the image sequence. In real time, segmentation occurs at 2 Hz, and improvements are being implemented for video rate performance. CONCLUSIONS: Computer vision algorithms allow for real time extraction of fundus imagery from marginal quality, slit lamp fundus biomicroscope image sequences.
Algorithms↗
LOCS III examination at the slit lamp, do settings matter?
PURPOSE: To explore whether slit lamp settings may influence measurements made with the LOCS III grading system. The following were tested using a total of 221 subjects: 1. Test-retest variability (with and without the neutral density filter). 2. Readings with and then without the neutral density filter. 3. Readings with maximum and minimum illumination (filter and rheostat). 4. Examinations with different slit beam width. 5. Light output from 10 slit lamps (Haag-Streit 900BM) was measured using a lightmeter. RESULTS: The 95% limits of agreement (test-retest examination) for nuclear opacity (NO), nuclear colour (NC), cortical opacity (C), and posterior subcapsular lens opacity (P) were 0.66, 0.60, 0.62 and 0.39, respectively, using standard settings. Corresponding results with the neutral density filter were similar. Examinations performed with and without the neutral density filter showed that the 95% limits of agreement increased by a factor of at least 1.7 compared with test retest data (NO and NC) and 2.2 for (C and P) (p < 0.001 (f test)). Maximum vs. minimum brightness settings increased variability by a factor of at least 2.1 (NO and NC) and 3 (C and P) (p < 0.001 (f test)). Changing beam width measurements produced a significant systematic measurement bias of 0.3 for NO and 0.4 for NC (P < 0.01 (t test)), a wider beam giving a higher score. Individual slit lamps may vary by a factor of four in their light output levels for apparently identical settings. The range of illumination produced by a slit lamp is 46-fold. CONCLUSIONS: For nuclear opacity and nuclear colour measurements, changing settings between examinations increases variability without evidence of systematic bias. However, using a thicker slit beam induced a systematic bias. For cortical and posterior subcapsular lens opacity, varying the illumination had more marked effects on reproducibility without a systematic bias.
Cataract↗
[Experience with a new slit lamp concept (author's transl)].
Since the development of the first slit lamp by A. Gullstrand in 1911 this instrument is an indispensible part of our diagnostic repertoire. Nevertheless it was not until almost 40 years later that the slit lamp could be able to be used for the examination of the fundus as a result of the development of the Goldmann 3-mirror contact glass. Because of the increasing importance of antiretinal detachment prophylaxis the slit lamp examination also of the rear end of the eye its becoming more and more important because of its good stereoscopy, the excellent illumination and the high magnification. A newly developed slit-lamp apparatus fulfils these special requisites which have firstly been demanded recently. This apparatus is easy and comfortable to use, which makes easier above all the contact glass examination. Technical factors, possibilities of application and experience with this slit-lamp are discussed.
Ophthalmoscopes↗
Adjusting the slit-lamp oculars: an unnecessary burden or a must?
Adjusting the slit-lamp eyepiece rings is perceived by some to be insignificant for achieving adequate focus. Others assume that these rings should be set only to compensate for one's refractive error. Observations are presented concerning the eyepiece scale setting during routine examinations, slit-lamp mounted YAG and Argon laser procedures and during opthalmic surgery. Diagrams illustrate the optical basis of these observations. Factors influencing optimal eyepiece ring setting, besides ametropia, include slit-lamp misalignment (variations in calibration) as well as unconscious accommodation. An inaccurate setting cannot be fully compensated by adjusting the slit-lamp joy-stick. When an incorrect setting is used, while using oblique illumination, it becomes impossible to focus on details placed at the center of the viewfinder. In addition, irrespective of joy-stick position, it is impossible to view an oblique slit transecting the cornea in perfect focus. An accurate setting, as a whole, results in sharper images throughout the slit-lamp examination. Differences between individual instruments make it necessary to reset the eyepieces for each eye and for each individual instrument. Methods are described for evaluating the need for readjustment, as well as a simple technique for calibration in the absence of a focusing rod.
Calibration↗
[Slit-lamp perimetry: a new diagnostic technique].
AIM OF THE STUDY: To test a novel diagnostic technique, slit-lamp perimetry. PATIENTS AND METHODS: Slit-lamp perimetry is performed during a normal slit-lamp examination by projecting a small, round light mark onto the fundus. The light mark is moved and consecutively the patient is asked, if the light moved towards or away from the scotoma. Using the patients feedback the light mark can be placed exactly onto the retinal region corresponding to the scotoma. This method was tested on a patient with a microinfarction of a small retinal arteriole and on two patients with small preretinal parapapillary vitreous floaters. RESULTS: Slit-lamp perimetry correctly localized preretinal vitreous floaters and a fresh cotton wool spot missed on an dilated fundus examination. CONCLUSION: Slit-lamp perimetry is a novel rapid diagnostic technique to localize retinal and preretinal pathologies reponsibles for scotomas.
Adult↗
Conversion of lens slit lamp photographs into physical light-scattering units.
PURPOSE: To derive from lens slit lamp photographs by means of densitometry the physically defined quantity for light scattering (the Rayleigh ratio) and to expand the use of the Lens Opacity Classification System (LOCS III) to include clear lenses and also to calibrate the LOCS III Nuclear Opacity (NO) score in physical terms. METHODS: Series of slit lamp photographs were taken from 38 eyes from 29 subjects (age range 18 to 84 years old) including cataracts, for 0.1- and 0.2-mm slit width, using 200 ASA and 1600 ASA film speed (Kodak professional; Eastman Kodak, Rochester, NY) and different flash settings with a Topcon SL-6E (12 slit/speed/flash combinations; Paramus, NJ). Additionally 19 eyes were photographed with a Zeiss 40 SL/P (8 slit/speed/flash combinations; Carl Zeiss, Thornwood, NY). A calibrated suspension of latex spheres also was photographed at the same 20 conditions. Densitometry was performed on the nuclear area of all photographs including the LOCS III standards, using a photometrically corrected photocell. Slit width and flash intensity settings were photometrically calibrated. All eyes and the suspension were digitally "photographed" with the EAS-1000 (Nidek, Gamagori, Japan) Scheimpflug system. RESULTS: For each eye and the suspension, the series of 20 or 12 densities, corresponding to a range of about 1 log unit in the amount of light used, proved to follow closely a course common to all eyes (the two film characteristics), apart from a shift in the amount of light (because of the differences in light back scattering). CONCLUSIONS: From normal slit lamp photographs, the physical quantity for light (back) scattering can be derived using transformation graphs derived in this study. The LOCS III NO score also can be used for clear lenses and translated into physical units. In this way, slit lamp photography can be used better for more precise studies, provided some minimal calibration of the photograph slit lamp.
Adolescent↗
Video equipment recommendations for slit lamp videography.
Current developments in video technology have made videotaping through a slit lamp a useful capability available at a more reasonable cost. The technical basis of equipment needed to select or design an apparatus for slit lamp videography is reviewed. As an overview, the optimum slit lamp video apparatus would have the following criteria; the slit lamp should have zoom optics and rheostat illumination, the beam splitter should be a mirror or 70/30 type, the camera should have maximal light sensitivity (101ux) with reasonable resolution (greater than 300 lines). The recorder should be SP-Umatic or Super VHS for documentation, or consumer VHS for patient education, and the monitor should be a professional 13- or 15-inch monitor.
Humans↗
Videotape recording system for use with the slit lamp biomicroscope.
Previous attempts at capturing slit lamp biomicroscopy observations on videotape have had a limited success due to high expense, poor resolution, and/or insufficient light. A slit lamp biomicroscope-videotape recording system which incorporates current technology is described. Although the system is used primarily for contact lens research, other applications for the eye care practitioner are described.
Fundus Oculi↗
Depth measurement with the slit-lamp microscope.
The sagittal distance of ocular structures can be obtained with a slit-lamp microscope providing the movement of the slit-lamp can be measured. A simple device consisting of a pointer attached by a spring clip to the axle of a Haag-Streit 900 slit-lamp is described. The pointer rides over a scale which slides with the slit-lamp. Comparisons of anterior chamber depth and lens thickness showed a high correlation between this optical method and ultrasound measurements.
Anterior Chamber↗
[Comparison of optic nerve head measurements obtained with the slit lamp and with CSLO].
PURPOSE: To evaluate the accuracy of disk size and cup/disk ratio (C/D) estimation by measuring the vertical diameter and cup/disk ratio at the slit lamp. METHODS: Two hundred and thirty eight eyes of 185 people, 82 glaucomas and 156 normal subjects were included. All underwent slit lamp examination, tonometry, optic nerve photographs, scanning laser tomography (HRT) and standard perimetry (Humphrey). Correlation between slit lamp measurements (vertical diameter and C/D ratio) and HRT parameters was evaluated. RESULTS: There is a significant correlation between the disk diameter measured at the slit lamp and the disk area measured with HRT (Pearson Test, r: 0.52, p<0.001). Additionally, there is significant correlation between the semi-quantitative estimation of C/D ratio at the slit lamp and the C/D area ratio from the HRT (r: 0.83, p<0.001). CONCLUSION: Measuring the vertical diameter and the C/D ratio at the slit lamp is a useful method for estimating the real disk area and C/D ratio. It is highly recommended that disk size be estimated when attempting to interpret clinical findings in the optic nerve head.
Anthropometry↗