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PubMed1999

[Microperimetry and reading saccades in retinopathia solaris. Follow-up with the scanning laser ophthalmoscope].

UNLABELLED: Patients with solar retinopathy often complain of minute central scotomas and are handicapped when reading. The purpose of this study was to verify scotomas that are too small to be detected by standard perimeters and to analyze patients' reading patterns. METHODS: Nineteen patients (12 female, 7 male, aged 5-46 years) with acute solar retinopathy after watching a solar eclipse on 12 October 1996 underwent scanning laser ophthalmoscope (SLO) microperimetry within 10 days after exposure using stimulus size Goldmann I (0.11 degree) with the 20 degrees field. Size and depth of scotomas were measured. Eye movements during reading were recorded on videotape. Follow-up was at 1 and 6 months. RESULTS: Thirty-one eyes (7 patients unilateral, 12 bilateral) showed scotomas. Four eyes showed anatomic changes in the retinal pigment epithelium but no functional loss. VA was 0.16 to 0.5 in 5 eyes, 26 had VA of 0.8-1.2. Scotomas could be detected in all eyes with subjective impairment. Scotoma size varied from 0.3 to 1.7 degrees (1 patient 6 degrees). Forty-four percent were deep scotomas (0 dB). All defects improved at 1 and at 6 months; 25% were no longer detectable. Reading speed was reduced in 75% of eyes (42% at 6 months): 200-560 signs/min, median: 510, normal > or = 660 (at 6 months: 350-920 signs/min, median 670). This was especially due to increased number of regressions (in 81% of eyes, 21% at 6 months). The frequency and width of saccades were no different from normal subjects. CONCLUSION: Minute scotomas (diameter = 0.3 degree) can be detected with the SLO. All patients showed objective improvement of their field defect up to 6 months, even when this was not noted by the patient or thought to be due to habituation. Small scotomas can dramatically reduce reading performance.

Adolescent↗
PubMed2002

Reproducibility of multifocal ERG using the scanning laser ophthalmoscope.

BACKGROUND: Prior to application of multifocal electroretinography (mfERG) using the scanning laser ophthalmoscope (SLO) in a clinical routine setting it is important to determine the reproducibility of this technique in normals during the use of monochromatic red HeNe laser light. METHODS: Thirty-five eyes of 35 volunteers (visual acuity > or =0.8) were examined using the SLO for mfERG with two test patterns in a 20-deg diameter field. Multifocal ERG was performed using the RETIscan system with a binary m-sequence technique. Evaluation was performed for the first-order kernel concentric ring segments. Three measurements were performed for each type of sequence (six sequences for seven hexagons, eight for 19 hexagons) with removal of electrodes between the recordings. Stimulus intensity for all subjects was set to 235 cd/m2 (background illumination 20 cd/m2). We used gold-foil electrodes to obtain good signal quality while not disturbing corneal transmission and refraction. RESULTS: The coefficient of variation for the P1 amplitudes for the center and surrounding ring(s) was 10.4% and 9.3% for seven hexagons and 15.2%, 9.3% and 7.6%, for 19 hexagons, respectively. The corresponding intraclass correlation coefficients varied between 0.59 and 0.77. The CV for the P1 peak times varied between 1.3% and 1.5% for ring analysis in seven and 19 hexagons. CONCLUSION: Our data shows that the setup of mfERG with the SLO provides a retest variability comparable with conventional CRT examinations. One advantage is the simultaneous visualization of the fundus with observation of fixation during examination, thereby allowing more confidence in pathological results.

Electroretinography↗
PubMedDate not supplied

Tracing method in the assessment of retinal capillary blood flow velocity by fluorescein angiography with scanning laser ophthalmoscope.

PURPOSE: To evaluate the feasibility of a new method (the tracing method) for measuring perifoveal capillary blood flow velocity (BFV). METHODS: The BFV in the perifoveal capillaries was measured in 12 eyes of healthy subjects and 12 eyes of patients with clinically significant macular edema (CSME) by fluorescein angiography using a scanning laser ophthalmoscope by either the tracing method or the conventional method. A randomized crossover design was employed to assign the subjects to each method. RESULTS: The number of capillaries recognized by the tracing method in healthy subjects and in patients with CSME was significantly higher than that recognized with the conventional method (P = 0.0134 and P = 0.0108, respectively). The number of fluorescent dots detected by the tracing method in healthy subjects and in patients with CSME was also significantly higher than that detected with the conventional method (P = 0.0002 and P = 0.0137, respectively). Accurate detection of the movement of fluorescent dots and analysis of BFV were possible with the tracing method. The BFV varied within each perifoveal capillary, and the mean BFV also varied according to capillary location in the macula. CONCLUSION: The new tracing method is useful for analyzing the retinal capillary BFV in healthy subjects and in patients with CSME.

Aged↗
PubMed1996

Displacement correction and surface reconstruction of the retina using scanning laser ophthalmoscopic images.

A method for a three-dimensional surface reconstruction of the retina in the area of the papilla is presented. The surface reconstruction is based on a sequence of discrete gray-level images of the retina recorded by a scanning laser ophthalmoscope (SLO). The underlying assumption of the surface reconstruction algorithm developed here is that the depth information is also encoded in the brightness values of the single pixels in addition to the ordinary spatial 2D information. The brightness of an image position depends on the degree of reflection of a confocal laser beam. Only those surface structures located directly in the focus plane of the confocal laser beam produce a high response to the laser light. The displacements between the single images of a sequence are considered to be approximately linear and are corrected by applying the cepstrum technique. The depth is estimated from the volumetric representation of the image sequence by searching for the maximal value of the brightness within a computed depth profile, at every image position. In the resulting images, disturbances occurring during the recording cause incorrect local estimations of the depth. These local disturbances are corrected by applying specially developed surface improvement processes. The work is concluded with a comparison of several different approaches to reduce the noise and disturbances in SLO image data.

Algorithms↗
PubMed1990

The pigeon's eye viewed through an ophthalmoscopic microscope: orientation of retinal landmarks and significance of eye movements.

The retina of live, anaesthetized pigeons was inspected with an ophthalmoscopic microscope mounted on a goniometer. Retinal landmarks (optic axis, pecten, fovea, border between the yellow and red field) and the ora terminalis were projected into the visual field of the eye and related to existing data. The resting position of the eye is determined by an orientation of the pecten 45 degrees to the horizontal plane and the optic axis pointing to the horizon with an azimuth angle of 70 degrees relative to the bill. The binocular overlap is maximal (approximately 30 degrees) some 15 degrees above the eye-bill axis. In the resting position of the eye the red field is directed to the lower frontal visual field with only marginal binocular overlap. Binocular overlap of the area dorsalis with the red field, however, during frontal fixation is brought about by eye movements in the range we have demonstrated. The fixation point is 10 degrees below the eye-bill axis.

Animals↗
PubMed2005

Polarimetric high-resolution confocal scanning laser ophthalmoscope.

A polarimetric high-resolution confocal scanning laser ophthalmoscope has been developed. The system incorporates a fixed linear polarizer in the illumination path and a rotatory quarter-wave plate and another fixed linear polarizer in the registration path. Retinal areas that are smaller than those provided by commercial instruments can be imaged. Series of four fundus images for independent polarization states in the second pass were recorded for different eyes and retinal locations and the spatially resolved Stokes vectors calculated. From those images, the contrast across retinal blood vessels was maximized and the corresponding image was reconstructed. In terms of polarization, the analysis of small retinal areas might prove to be useful in the improvement of retinal imaging and the enhancement of structural details in the early diagnosis of ocular pathologies.

Eye Diseases↗
PubMed1995

Indirect ophthalmoscope perimetry in patients with retinal detachment or retinoschisis.

PURPOSE/METHODS: We evaluated visual field testing, using indirect ophthalmoscopy, in patients with retinal detachment or retinoschisis. While performing ophthalmoscopy, we projected a shadow onto the schisis or detachment by holding a scleral depressor on the observer's side of the condensing lens. A response was recorded as positive if the patient saw the shadow. RESULTS/CONCLUSION: In all 20 detachment eyes, compared to zero of 12 schisis eyes, the response was positive. Indirect ophthalmoscope perimetry can help distinguish retinoschisis from retinal detachment.

Humans↗
PubMed1994

Capillary blood flow velocity measurements in cystoid macular edema with the scanning laser ophthalmoscope.

Using a scanning laser ophthalmoscope, we calculated the velocity of retinal blood flow in a juxta-foveolar capillary during the course of cystoid macular edema after partial central retinal vein occlusion in a 53-year-old woman. The mean velocity of the fluorescent dots in the macular capillary of the right eye with cystoid macular edema was 1.59 +/- 0.08 mm/sec at the initial examination. Despite the systemic administration of indomethacin (75 mg/day for three weeks), best-corrected visual acuity decreased from 20/30 to 20/70, and the velocity became 0.82 +/- 0.13 mm/sec. Prednisolone (30 mg/day orally for one week) improved the cystoid macular edema, and the velocity was 0.96 +/- 0.06 mm/sec 12 days after initiation of the drug. The velocity gradually improved; one year later it was 1.65 +/- 0.17 mm/sec and visual acuity was 20/22. Velocity in the left eye, which did not have cystoid macular edema, was 2.16 +/- 0.16 mm/sec. Thus, scanning laser ophthalmoscopy proved useful for measuring the velocity of retinal blood flow.

Blood Flow Velocity↗
PubMed2001

Scanning Laser Ophthalmoscopic Microperimetry on Idiopathic Epiretinal Membrane and Vitreomacular Traction Syndrome.

Purpose: To evaluate visual function before and after vitrectomy for idiopathic epiretinal membrane and vitreomacular traction syndrome.Methods: Microperimetry with scanning laser ophthalmoscope (SLO) was performed in 4 eyes with idiopathic epiretinal membrane (IERM) and 2 eyes with vitreomacular traction syndrome (VMTS), before and at least 3 months after vitrectomy.Results: Five eyes had preoperative scotoma, which disappeared postoperatively. In 1 eye, absolute and relative scotomas developed postoperatively over the areas where the retinal surface was vigorously scratched to peel off an overlying membrane, and in another eye new scatomas appeared over a newly formed epiretinal membrane 8 months after vitrectomy.Conclusions: To our knowledge, the present report is the first to describe preoperative absolute scotoma in IERM, VMTS and also iatrogenic absolute scotoma due to retinal scratching. SLO microperimetry is useful for evaluation of visual function before and after vitrectomy for epiretinal membrane and vitreomacular traction syndrome.

Journal Article↗
PubMedDate not supplied

Indocyanine green angiograms of choroidal nevi. comparison between confocal and nonconfocal scanning laser ophthalmoscope and fundus video camera.

PURPOSE: A fundus video camera and a nonconfocal scanning laser ophthalmoscope (SLO) detect direct light and indirect light, whereas a confocal SLO detects mostly direct light. Differences in confocal and nonconfocal SLO images and fundus video camera images are most likely due to their different optical systems. These differences were examined in indocyanine green (ICG) angiograms of a choroidal nevus. METHODS: A confocal SLO, a nonconfocal SLO, and a high resolution digital fundus video camera were used to obtain ICG angiograms of pigmented choroidal nevi in 4 patients for 30 minutes following dye injection. RESULTS: All the angiograms showed a hypofluorescent region in the nevus until 10-14 minutes after dye injection, except in 1 patient in whom no hypofluorescent region was seen in an early confocal-SLO angiogram. From 20 minutes to 30 minutes postinjection, the hypofluorescent regions were still visible in all fundus video camera angiograms and nonconfocal SLO angiograms but not in confocal SLO angiograms. CONCLUSIONS: Early angiograms taken with the three angiography systems showed a similar appearance of the choroidal nevus. However, late ICG angiograms with a confocal SLO showed different images from those taken with a nonconfocal SLO or a fundus video camera. It is suggested that the angiography system and the aperture size of an SLO should be selected according to the aspect of the pigmented choroidal nevus that is of interest in late-phase ICG angiography.

Adult↗
PubMed1991

Retinal capillary blood flow measurement with a scanning laser ophthalmoscope. Preliminary results.

The scanning laser technique in combination with digital image analysis allows direct objective measurement of flow velocities in perimacular capillaries. In addition, the complete macular network of capillaries can be observed. By means of digital frame-to-frame picture analysis of digital recordings, blood flow velocities and morphologic data have been measured. The mean flow velocity in perimacular capillaries observed with the scanning laser ophthalmoscope in healthy subjects (n = 21) amounted to 3.28 +/- 0.45 mm/second. In patients (n = 13) with diabetes mellitus (no or background retinopathy), the mean flow velocity was significantly reduced (2.89 +/- 0.57 mm/seconds) compared with healthy subjects. Morphologic data of the perifoveal capillary bed showed a significant reduction of capillaries in patients with diabetes mellitus when compared with healthy subjects.

Adult↗
PubMed2004

[Analysis of optic nerve head by confocal scanning laser ophthalmoscope in ocular hypertension].

PURPOSE: To analyze optic nerve head topography using confocal the scanning laser ophthalmoscope (CSLO) in ocular hypertension in comparison to normal eyes. PATIENTS AND METHODS: We examined 25 patients with ocular hypertension and 27 normal controls. All of them had a complete ophthalmic examination. Optic nerve head analysis was performed by using a CSLO-type Heidelberg retina tomograph (HRT). The following stereometric parameters were evaluated: disc area, area and volume of cup, cup/disc ratio, area and volume of neuroretinal rim, mean and maximal cup depth, cup shape measure, height variation contour, mean retinal nerve fiber layer thickness, and retinal nerve fiber layer (RNFL) cross-section area. RESULTS: In ocular hypertension eyes, rim volume, height variation contour and RNFL thickness showed a statistically significant reduction compared to normal eyes. CONCLUSION: HRT appears to be an important tool in detecting early damage of retinal nerve fiber layer in ocular hypertension.

Adult↗
PubMedDate not supplied

Inverse image alignment method for image mosaicing and video stabilization in fundus indocyanine green angiography under confocal scanning laser ophthalmoscope.

An efficient image registration algorithm, the Inverse Compositional image alignment method based on minimization of Sum of Squared Differences of images, is applied in fundus blood vessel angiography under confocal scanning laser ophthalmoscope, to build image mosaics which have larger field of view without loss of resolution to assist diagnosis. Furthermore, based on similar technique, the angiography video stabilization algorithm is implemented for fundus documenting. The actual underlying models of motion between images and corresponding convergence criteria are also discussed. The experiment results in fundus images demonstrate the effectiveness of the registration scheme.

Algorithms↗
PubMed2000

Multiple sclerosis with normal neuro-ophthalmological work-up: results of focal stimulations induced by a scanning laser ophthalmoscope.

OBJECTIVE: Visual evoked potentials (VEPs) are a very useful tool in diagnosis of multiple sclerosis (MS). Nevertheless, in some cases of the disease, VEPs are normal. The aim of this study was to evaluate the diagnostic value of focal checkerboard reversal stimulation based on opto-acoustic modulation generated by a scanning laser ophthalmoscope (SLO) in patients whose standard neuro-ophthalmological work-up was normal. METHODS: We prospectively studied 185 MS patients. In this cohort we found 30 patients with definite MS and normal neuroophthalmological work-up and we studied the diagnostic yield of focal visual stimulation in these patients. We performed focal SLO-elicited VEPs with two different spatial distributions: a central 8 x 8 degrees square field and a central 8 x 8 degrees exclusion square. The results were analysed in terms of age of the patient, course of the disease, and disability evaluated on the Expanded Disability Status Scale (EDSS). RESULTS: Mean latencies of focal VEPs were increased in MS patients compared to controls. In MS, focal stimulation allowed dysfunction of the visual system to be detected in 50% of patients who have been classified as normal according to conventional VEPs. VEP abnormalities were found to be correlated with the EDSS score (P<0.001) and the course of the disease (P<0.05). CONCLUSION: We have demonstrated the value of focal VEPs in MS diagnosis using SLO-based techniques. Further prospective work in patients with possible and probable MS should enable an evaluation of the sensitivity and specificity of this method in the early diagnosis of MS.

Adult↗
PubMed1998

The correlation of the visual field with scanning laser ophthalmoscope measurements in glaucoma.

PURPOSE: To assess the relationship between Humphrey visual field data and optic disc topographical data collected by the Heidelberg Retina Tomograph (HRT) scanning laser ophthalmoscope in chronic glaucoma patients. METHODS: The mean deviation (MD) and corrected pattern standard deviation (CPSD) from Humphrey visual fields of 106 eyes of 106 patients with glaucoma were analysed for correlation with the multiple topographical measures calculated by the HRT. RESULTS: Significant correlations were found between MD of the visual field and several optic disc measurements. These included neuroretinal rim volume, mean nerve fibre layer thickness and cross-sectional area, and the cup shape measure. CPSD correlated significantly only with mean nerve fibre layer cross-sectional area. This pattern was common to the whole circumference of the disc with the exception of the directly temporal segment. CONCLUSION: Optic disc topography performed by HRT reflects the optic disc pathology in correlation with perimetry.

Aged↗
PubMed2003

Multifocal ERG recording with simultaneous fundus monitoring using a confocal scanning laser ophthalmoscope.

PURPOSE: To assess the general feasibility of recording multifocal electroretinograms (mfERGs) with simultaneous fundus monitoring in a clinical setting. METHODS: An mfERG system (RETIscan) and a confocal scanning laser ophthalmoscope (Heidelberg Retina Angiograph) were connected to record mfERGs elicited by a pseudorandom binary m-sequence stimulus generated by a 514 nm laser source. Recordings were compared to a conventional mfERG system using monitor stimulation. A total of five subjects (two normal subjects and three patients) were examined. RESULTS: In normal volunteers records obtained by the fundus-monitored mfERG showed highest response densities in the central fundus area and a decrease of response amplitudes towards the periphery paralleling cone receptor density. However, compared to the monitor stimulation, the drop-off of amplitudes as a function of eccentricity was not as clearly defined. The responses obtained from patients with retinal diseases were diminished in the areas of retinal dysfunction. CONCLUSIONS: These preliminary findings indicate that the technique of laser stimulation in principle allows for topographic retinal recording. This method might be useful, for example if the retinal position of the stimulus array is not centred onto the fovea but deviates due to fixation problems. However, further improvement of the technique appears necessary before considering routine clinical application.

Adult↗
PubMed2005

Oral fluorescein angiography with the scanning laser ophthalmoscope in diabetic retinopathy: a case controlled comparison with intravenous fluorescein angiography.

AIM: To compare the performance of oral fundus fluorescein angiography with a confocal scanning laser ophthalmoscope (SLO) with intravenous fundus fluorescein angiography (IVFFA) with a fundus camera in the assessment of sight-threatening diabetic retinopathy. PATIENTS AND METHODS: A total of 25 patients undergoing IVFFA to investigate their diabetic retinopathy were recruited. Participants returned 1 week later and an oral angiogram with the SLO was performed. Six facets of the oral and intravenous angiograms were scored and compared: visualization of the foveal avascular zone (FAZ); branch retinal identification; macular leakage; identification of microaneurysms in areas of macular leakage; peripheral nonperfusion, and leakage from neovascular complexes. RESULTS: Compared to IVFFA, the FAZ was unreliably visualized with oral angiography (Kappa 0.1, 95% CI 0-0.3). In contrast, macular leakage (Kappa 0.78, 95%, CI 0.72-0.83), identification of microaneurysms in areas of macular leakage (Kappa 0.78, 95%, CI 0.72-0.83), and neovascular complexes (Kappa 1.0) were reliably seen. Analysis of the visualization of peripheral nonperfusion was complicated by the finding that profuse dye leakage from neovascular complexes obscured the view of the peripheral retina. If the five angiograms in which this occurred were excluded, oral angiography identified 23 of the 24 eyes in which significant nonperfusion was found on IVFFA. CONCLUSION: Oral angiography with the SLO can provide high-quality angiograms that allow judgments to be made about the presence of treatable diabetic maculopathy, proliferative diabetic retinopathy, and peripheral nonperfusion. In the presence of coexisting macular oedema, it proved to be an unreliable technique with which to investigate foveal ischaemia.

Administration, Oral↗
PubMed1999

A simple eye model to objectively assess ophthalmoscopic skills of medical students.

OBJECTIVES: Ophthalmoscopy is an important clinical skill that is essential for medical students to master. Competency in the performance of this skill needs to be assessed objectively. DESIGN: The development of a simple, cheap eye model for objective assessment of ophthalmoscopic skills of medical students is described. SETTING: University of Liverpool. SUBJECTS: Undergraduate medical students. RESULTS: The model was used in 803 assessments and showed a high level of student performance, based on both checklist marking of the general approach to the examination and objective marking of the ability of students to manipulate the light beam, focus the lens and systematically examine the model's fundus. CONCLUSIONS: The method described provides a simple, cost-effective, objective assessment of the performance of ophthalmoscopy.

Audiovisual Aids↗