Retinal image location of hand, fingers, and objects during manual tasks.

PURPOSE: A new method was developed using the scanning laser ophthalmoscope (SLO) to investigate the effects of central visual loss on eye-hand coordination in manual tasks. Using the SLO, the retinal positions of the hand, fingers, and objects are imaged and recorded while a subject performs a manual task. METHOD: A video camera images the subject's hand and objects to be manipulated in the SLO laser-beam raster, producing a video image of a subject's hand, fingers, and objects on the subject's retina while the objects are manipulated. A subject with bilateral central scotomas and an age-matched control subject with normal vision traced an ellipse with the index finger, tapped four disks in sequence, and carried out a pattern duplication task with pegs. Retinal positions of the fovea or preferred retinal locus (PRL), fingers, and objects were measured from digitized SLO images. RESULTS: In all tasks, the fovea or PRL was directed to an object or position before the fingers arrived. This lead time was much greater for the scotoma subject than the control subject ( approximately 1400 vs. approximately 400 ms, respectively). The scotoma subject was much less accurate in placing the PRL and fingers on objects and required substantially more time for task completion than the control subject. CONCLUSIONS: The coordination of foveal fixation and finger placement found with the SLO method was similar to that found by others using eyetracking techniques with visually normal subjects. The presence of a central scotoma and use of a PRL caused marked deterioration in the quality of this coordination. Unlike eyetracking methods, the SLO technique does not require calibration because the positions of the fingers and objects are directly observable on the retina. This method could be useful in studying eye-hand coordination of individuals with scotomas that affect foveal vision.     

Reading with a macular scotoma. I. Retinal location of scotoma and fixation area

To investigate how patients with macular scotomas use residual functional retinal areas to inspect visual detail, a scanning laser ophthalmoscope (SLO) was used to map the retinal locations of scotomas and areas used to fixate. Three patients with dense macular scotomas of at least 20 months duration and with no explicit low vision training were tested. SLO stimuli were produced by computer modulation of the scanned laser beam, and could be placed on known retinal loci by direct observation of the retina on a television monitor. Videotaped SLO images were analyzed to produce retinal maps that are corrected for shifts of stimulus position due to fixational eye movement, thus showing the true retinal locations of scotomas and fixation loci. Major findings were as follows: 1) each patient used a single, idiosyncratic retinal area, immediately adjacent to the scotoma to fixate, and did not attempt to use the nonfunctional foveola, 2) fixation stability with the eccentric fixation locus was as good as, or better than, that of ocularly normal subjects trying to fixate at comparable eccentricities, 3) fixation stability was not systematically related to clinical visual acuity, and 4) there is good agreement as to the shape and overall size of SLO and standard clinical tangent screen scotoma maps for these three patients.     

Horizontal and vertical micropsia following macula-off rhegmatogenous retinal-detachment surgical repair

Background Dysmetropsia or distorted image size perception (smaller: micropsia; larger: macropsia) is known to occur after successful surgical re-attachment for macula-off rhegmatogenous retinal detachment. However, the vertical and horizontal components of size distortion have not been previously quantified separately. The purpose of this article is to describe horizontal and vertical dysmetropsia occurring in patients following pars plana vitrectomy and gas treatment (octafluoropropane, C₃F₈ or sulfur hexafluoride, SF₆) for macula-off rhegmatogenous retinal detachment. Material and methods Four patients (mean±SD, 59±8 years; three women and one man) who had had pars plana vitrectomy and gas treatment for macula-off rhegmatogenous retinal detachment 6–7 months earlier underwent ocular examination, best corrected visual acuity test, threshold horizontal and vertical dysmetropsia measurement using a computerised version of the New Aniseikonia Test, slit-lamp examination and optical coherence tomography of the macula. Results All patients had binocular visual complaints including difficulty judging distances or reading, rivalry or asthenopia. The logMAR visual acuity (mean±SD) in the operated eye was 0.52±0.199 and 0.02±0.171 in the unaffected eye. All patients perceived the image as smaller (micropsia) with the affected eye, with differences ranging from −9 to 0%. Four patients showed 3% or more size difference between horizontal and vertical meridians. Conclusions Dysmetropsia does occur in symptomatic patients following successful surgical repair of macula-off rhegmatogenous retinal detachment by pars plana vitrectomy and gas treatment. The effect on image size is heterogenous across the retinal area affected. Presented at the annual meeting of the Association for Resarch into vision and ophthalmology (ARVO), Fort Lauderdale, Florida, 2005. The authors have no propietary interests.     

Retinal location of the preferred retinal locus relative to the fovea in scanning laser ophthalmoscope images.

PURPOSE: It is difficult to determine the position of a preferred retinal locus (PRL) relative to the fovea in scanning laser ophthalmoscope (SLO) images as a result of disease-related retinal morphologic changes that obscure the fovea. To overcome this problem, we developed a method for determining retinal foveal position based on normal fixation position relative to the optic disk. The normal foveal position measurements can then be used to estimate the distance between a PRL and the fovea. METHODS: Using the SLO, foveal position was determined for 50 normal subjects by measuring the retinal locus of fixation relative to the optic disk in undistorted SLO images. The resulting normal foveal fixation area is described by a bivariate normal ellipse that can be plotted on any undistorted SLO image. Measurement reliability was assessed by repeated measurements. The PRL relative to the normal foveal fixation area was determined for 24 subjects with macular degeneration and bilateral central scotomas. RESULTS: The normal foveal fixation area based on all 50 subjects is described by a p = 0.9 bivariate ellipse whose centroid is located 12.6 degrees temporal to the temporal optic disk edge and 1.4 degrees inferior to a horizontal line bisecting the disk. PRL area is shown to increase with distance from the foveal fixation ellipse centroid. The shape of the PRL, characterized by the ratio of PRL ellipse major to minor axis, was found to depend on whether the PRL was vertically or horizontally aligned with the foveal fixation centroid. CONCLUSIONS: PRL position relative to the fovea can be reliably estimated by plotting the normal foveal fixation bivariate ellipse on undistorted SLO images of retinas in which the fovea is obscured as a result of the disease process.     

Recording pattern reversal visual evoked response with the scanning laser ophthalmoscope

We recorded visual evoked responses (VERs) to alternating, checkerboard pattern stimuli using the scanning laser ophthalmoscope (SLO). Retinal position and focus of checkerboard stimuli were monitored on the SLO video monitor throughout testing. Checkerboard size, check size, and retinal positions were varied. Consistent with other, well-established pattern reversal techniques, the SLO method produced: 1) reliable VERs with amplitudes of 2 to 10 microvolts, 2) maximum amplitudes at an intermediate check size for a fixed overall pattern size, and 3) variations in VER amplitude depending on stimulus retinal position relative to the fovea. Hence, the SLO-VER technique would be useful for clinical VER measurements when precise retinal stimulus position and focus are desired.     

Imaging retinal densitometry with a confocal scanning laser ophthalmoscope

We describe a novel use of the Scanning Laser Ophthalmoscope (SLO), viz. as an imaging retinal densitometer. In our SLO a helium-neon or an argon laser beam is moved in a raster pattern over the retina; the reflected light is descanned (confocal SLO) and collected by a photomultiplier. Images of the fundus subtending 22 by 18 deg are displayed on a TV monitor. Single frames taken with 514 nm light were stored in a computer in arrays of 256 by 256 pixels and density differences between dark adapted and bleached images were calculated. With a full bleach density differences of about 0.35 were found in the center of the fovea; at retinal eccentricities of 15-20 deg we found 0.15. After selective bleaching with 633 nm light substantial density differences were only seen in the foveal area. We conclude that the confocal SLO is a very suitable instrument for imaging fundus reflectometry.     

Confocal fundus imaging with a scanning laser ophthalmoscope in eyes with cataract.

AIMS/BACKGROUND--The study aimed to determine the influence of increased intraocular light scatter on the contrast in scanning laser ophthalmoscope (SLO) images and to examine to what extent SLO images can visualise the fundus through media opacities due to cataract. METHODS--Intraocular light scatter was estimated from measurements of letter contrast sensitivity before and after cataract surgery in five eyes. SLO images were obtained before and after surgery using confocal apertures of 1, 2, 4, and 10 mm, at laser wavelengths of 633 and 780 nm. Visibility of the fundus was determined by measurements of retinal contrast. SLO images were compared with standard fundus photographs. RESULTS--SLO images obtained before surgery revealed details of the retina that were unresolvable in the fundus photographs because of light scattering. By using one of the three smallest apertures, image contrast was further improved. However, no simple relations between aperture size, estimated light scatter, and image contrast could be found. CONCLUSION--SLO imaging was found to be superior to fundus photography for viewing the retina in eyes with cataract. Owing to the inhomogeneous nature of cataracts, the optimal choice of confocal aperture and laser wavelength is not simple and must be individualised.     

Microperimetry--comparison between the micro perimeter 1 and scanning laser ophthalmoscope--fundus perimetry

PURPOSE: To compare microperimetry using the scanning laser ophthalmoscope (SLO, Rodenstock, Germany) and the recently introduced Micro Perimeter 1 (Nidek Technologies, Italy). DESIGN: Prospective comparative observational study. METHODS: Fundus perimetry with static threshold perimetry was performed using the SLO and the MP1 in 68 eyes of 40 consecutive patients with different retinal diseases for example, central serous chorioretinopathy, macular dystrophy, and age-related macular degeneration. With both instruments, an automated 4-2-1 staircase strategy with Goldmann III stimuli and a comparable number of stimuli were applied. The depth and size of the detected scotomata as well as the location and stability of fixation were compared between both instruments. RESULTS: There was good concordance of results, with 75% (51 of 68 eyes) showing an equal defect. Whereas the MP1 showed larger defects (depth and size) in 23.5% (16/68) of eyes studied than the SLO, the defects appeared larger with the SLO in 1 eye. Concerning fixation analysis, similar results were found for fixation stability with stable fixation in 47.1% (MP1: 32/68) and 48.5% (SLO: 33/68) and likewise for the location of fixation with foveal fixation in 54.4% (37/68) with the MP1 and the SLO. Whereas the average number of stimuli was similar for both instruments (MP1 56.8 +/-16.1, SLO 62.9 +/- 17.0), examination time was prolonged with the MP1 (MP1: 11m 35s +/- 3m 47s, SLO: 10m 29s +/- 3m 23s). Throughout all examinations, fundus visualization with the SLO was superior to the MP1. CONCLUSIONS: For automated threshold microperimetry the MP1 provides results comparable to our SLO perimetry. Both instruments enable detection of sensitivity loss of the central visual field and an analysis of fixation behavior during microperimetry. Nevertheless, the MP1, with its automated real-time image alignment, facilitates examination. Additionally, the enlarged field allows testing in an area of 44 x 36 degrees instead of the 33 x 21 degree-area of the SLO. However, in comparison to our SLO-software, the current software of the MP1 requires improvements before exact measurements of defined retinal diseases are possible.     

In vivo imaging and counting of rat retinal ganglion cells using a scanning laser ophthalmoscope

PURPOSE: To determine whether a scanning laser ophthalmoscope (SLO) is useful for in vivo imaging and counting of rat retinal ganglion cells (RGCs). METHODS: RGCs of Brown Norway rats were retrogradely labeled bilaterally with the fluorescent dye 4-(4-(dihexadecylamino)styryl)-N-methylpyridinium iodine (DiA). The unilateral optic nerve was crushed intraorbitally with a clip. RGCs were imaged in vivo with an SLO with an argon blue laser (488 nm) and optical filter sets for fluorescein angiography, before and 1, 2, and 4 weeks after the crush. Fluorescent cells were also counted in retinal flatmounts at baseline and 1, 2, and 4 weeks after the crush. An image overlay analysis was performed to check cell positions in the SLO images over time. Lectin histochemical analysis was performed to determine the relationship of microglia to the newly emerged DiA fluorescence detected by image overlay analysis after the optic nerve crush. RESULTS: Fluorescent RGCs were visible in vivo with an SLO. RGC survival decreased gradually after the crush. In the retina after the optic nerve crush, newly emerged DiA fluorescence detected by image overlay analysis corresponded to fluorescent cells morphologically different from RGCs in the retinal flatmount and was colocalized mostly with lectin-stained microglial processes. RGC counts by SLO were comparable to those in retinal flatmounts. CONCLUSIONS: The SLO is useful for in vivo imaging of rat RGCs and therefore may be a valuable tool for monitoring RGC changes over time in various rat models of RGC damage.     

New examination methods for macular disorders--application of diagnosis and treatment

To establish a diagnosis or evaluate the efficacy of treatment for macular disorders, we need methods to evaluate the anatomical and functional changes of these disorders. In this article, we describe several studies that we have conducted for 2 years. In section 1, we report our new methods for making a diagnosis and evaluating visual function in macular disorders. In section 2, we describe our trials of these examination methods in treatment. Here is the summary of our results. In section 1, to examine the structures of the macular area, we used a retinal thickness analyzer (RTA), a confocal scanning laser ophthalmoscope (Heidelberg Retina Tomograph, HRT), and optical coherence tomography (OCT) to measure retinal thickness and assess retinal microstructures. We compared retinal imaging analysis of various macular diseases obtained with these three instruments. With the RTA, we obtained good three-dimensional macular images displayed on a retinal thickness map, but the retinal thickness map did not demonstrate the thickened retina with dense retinal hemorrhages, and high backscattering from hard exudates might obscure the vitreoretinal interface. The HRT three-dimensional topographic image clearly showed the undulation of the retinal surface. However, it took a relatively long time to obtain the HRT image, and we sometimes could not obtain good topographic images because of fixation movement. Examination with the OCT allows confirmation of the retinal cross-sectional structures, such as retinoschisis or cystoid spaces and the vitreomacular interface, such as vitreous traction, that cannot be detected using other conventional methods with high resolution, but high reflectivity from dense hemorrhages obscured the deeper layers of the retinal structures. Measurement of retinal thickness obtained with both the RTA and OCT is highly reproducible, and there was significant correlation between the retinal thicknesses measured with the two instruments. We believe that these three instruments might contribute significantly to early, accurate diagnosis and better monitoring of the therapeutic effects of vitrectomy for macular diseases. In the future, if these fundus imaging analysis instruments can achieve higher resolution and can analyze three-dimensional retinal images, they will provide better information to clinically evaluate macular diseases. We demonstrated vitreous examination and examination from the retinal surface to the deeper retinal layer at the macular area using a scanning laser ophthalmoscope (SLO). The SLO examination with an argon laser and a large confocal aperture was useful for conducting kinetic examination of the vitreous opacity above the macula. With a diode laser and a ring aperture (dark-field mode), it was possible to examine the retina from the deeper retinal layer to the choroids. On the other hand, the SLO also allows us to conduct a functional examination of fixation. We demonstrated that the referred retinal locus of fixation may change during the follow-up period in patients whose central fixation is impaired due to macular disease, and we showed that the fixation behavior was related to the visual acuity. Therefore, the SLO is an ideal instrument for determining the visual field and the visual acuity before and after treatment in patients with macular disease, because of its precise localization of the examination point by directly observing the fundus and by monitoring fixation behavior. Our new program installed in the SLO allows us to complete the quantitative retinal sensitivity evaluation within 2 minutes, which is difficult to do using a conventional SLO program. Furthermore, we demonstrated for the first time that minute functional changes in the retina can be detected by the SLO under low background illuminance. Such changes cannot be detected under conventional conditions. In addition, the extrafoveal visual acuity of normal subjects and patients with macular disease was studied using this new SLO program. The iso-acuity lines could be illustrated by summarizing these results in normal subjects. The SLO acuity of the horizontal meridian is significantly better than that of the vertical meridian, and even in the nasal area adjacent to the optic disc, an acuity of better than 0.1 could be achieved. To evaluate macular function, we also investigated the blood flow of the choroid (CF), the retina (RF), and the choriocapillaris at the fovea (CCF). We investigated the CF in patients with age-related macular degeneration (AMD) using pulsatile ocular blood flow (POBF) measurements. In patients with exudative AMD, the POBF was significantly lower than in patients with nonexudative AMD or in control subjects. Decreased CF may play a role in the development of choroidal neovascularization in AMD. RF was measured using laser Doppler velocimetry (LDV). (ABSTRACT TRUNCATED)     

Correlations between densitometry of red-free photographs and reflectometry with the scanning laser ophthalmoscope in normal subjects and glaucoma patients

Objective: To compare image measurements of the retina produced by scanning laser ophthalmoscopy with those from red-free photographs (RFP) of the nerve fibre layer.Subjects: The left eyes of 23 subjects (10 normal, 7 glaucoma suspect and 6 glaucomatous) were included in this study.Method: All the eyes were photographed using standard red-free photography, and images of the retina were digitised directly from the SLO.Results: The correlation coefficient for all except three subjects was > 0.45, and the probability (p) that R=0 was < 0.05 in all but 5 eyes.Conclusions: The data indicate that variations in retinal surface reflectivity as measured by the SLO are similar to those recorded on negative film during RFP. This further suggests that the SLO can be useful for making objective measurements of the RNFL, without the intermediate and variable steps of photography.Abbreviations RFP red-free photographs - RNFL retinal nerve fibre layer - SLO scanning laser ophthalmoscope     

SLO-mfERG-Kampimetrie und SLO-Mikroperimetrie bei Morbus Stargardt

PURPOSE. We used a scanning laser ophthalmoscope (SLO) evoked multifocal electroretinography (mf-ERG) to evaluate retinal function in patients with Stargardt's disease. SLO microperimetry could demonstrate the size of central retinal scotoma very well in these patients. The aim of the examination was to correlate the results of SLO mf-ERG and SLO microperimetry. METHODS. In four patients with Stargardt's disease SLO mf-ERG and SLO microperimetry were performed. The area of measurement in the SLO mfERG had a 24 degrees diameter (12 degrees visual angle) at the posterior pole of the eye. Stimulation was done using a helium-neon laser (632.8 nm). Simultaneous control of fixation was made using a infrared laser (730 nm). SLO microperimetry was performed with stimuli having the size of Goldmann III stimuli and the intensities 0 dB, 12 dB and 20 dB. In this study the reduction of SLO mfERG amplitudes was correlated to graded stimulus intensities in the SLO microperimetry. RESULTS. The area of reduced retinal function in the SLO mf-ERG measurement could be well correlated to the size of the scotoma in the SLO microperimetry, using the stimulus Goldmann III with the intensity 20 dB. CONCLUSION. SLO mfERG and SLO microperimetry are sensitive methods for quantifying functional deficits and are therefore useful for performing a detailed examination of the retina.     

Trans-Tenon's retrobulbar triamcinolone infusion for myopic choroidal neovascularization

PURPOSE: To report the effects of trans-Tenon's retrobulbar injection of triamcinolone acetonide for subfoveal and juxtafoveal choroidal neovascularization (CNV) caused by pathological myopia. METHODS: Eleven consecutive patients (11 eyes) with myopic CNV were treated with trans-Tenon's retrobulbar injection of triamcinolone acetonide. Each patient received a single injection. Evaluation included best corrected visual acuity (BCVA) measurements, fluorescein fundus angiography, retinal oedema examined by optical coherence tomography (OCT), and retinal sensitivity using scanning laser ophthalmoscopy (SLO) at the initial examination and at 6 and 12 months after treatment. RESULTS: At 6 months after treatment, BCVA had improved by at least two ETDRS lines in eight eyes, and remained unchanged in three eyes. No eye showed worsening of VA by two or more ETDRS lines. At 12 months, BCVA had improved by at least two ETDRS lines in 10 eyes and remained unchanged in only one eye. The size of the CNV decreased in all patients after treatment. Fluorescein fundus angiography revealed an absence of dye leakage in the late angiographic phase. Optical coherence tomography revealed decreased retinal oedema in all patients and SLO microperimetry revealed an increase in retinal sensitivity in seven eyes, at both 6 and 12 months after treatment. Chorioretinal atrophy developed around the CNV in 10 eyes at 6 months and in all eyes at 12 months after treatment. CONCLUSIONS: Trans-Tenon's retrobulbar injection of triamcinolone acetonide for CNV resulting from pathological myopia appears to be relatively safe and to have a good visual outcome, although a longterm follow-up study in a larger series of patients is necessary.     

Measurement of eye rotations in three dimensions and the retinal stimulus projection using scanning laser ophthalmoscopy

A transformation algorithm is introduced to specify eye rotations in three dimensions from two-dimensional translations of ocular fundus landmarks dynamically monitored by means of the novel Scanning Laser Ophthalmoscope (SLO). The rotation parameters are expressed as Y-X-Z Euler angles and in terms of the rotation axis and one rotation angle. Additionally, the angular distance of the retinal stimulus projection can be evaluated relative to the fovea. By simultaneously operating as eye movement measurement device, fundus camera, and visual target projector, the SLO opens a variety of new applications for the combined analysis of eye movements and the underlying 'retinal events' in vision and oculomotor research.     

Ultrahigh-Resolution Combined Coronal Optical Coherence Tomography Confocal Scanning Ophthalmoscope (OCT/SLO): A pilot study

OBJECTIVE: To evaluate clinical images from a prototype ultrahigh resolution (UHR) combined coronal optical coherence tomography/confocal scanning ophthalmoscope (OCT/SLO) and to compare them to standard-resolution OCT/SLO images on the same patients. DESIGN: Cross-sectional pilot-study. PARTICIPANTS: Sixty-six eyes of 42 patients with various macular pathologies, such as age-related macular degeneration, macular edema, macular hole, central serous retinopathy, epiretinal membrane and posterior vitreous traction syndrome. METHODS: Each subject was first scanned with a standard-resolution OCT/SLO that has an axial resolution of ∼10 micron. Immediately following, patients were scanned with the prototype UHR OCT/SLO device. The UHR system employs a compact super luminescent diode (SLD) with a 150 nm bandwidth centered at 890 nm, which allows imaging of the retina with an axial resolution of 3 microns. Both coronal and longitudinal OCT scans were acquired with each system, and compared side-by-side. Scan quality was assessed for the observer's ability to visualize the vitreo-retinal interface and retinal layers – in particular of the outer retina/RPE/choroidal interface, increased discrimination of pathological changes, and better signal intensity. MAIN OUTCOME MEASURES: Ultrahigh and standard-resolution coronal and longitudinal OCT/SLO images of macular pathologies. RESULTS: In the side-by-side comparison with the commercial standard-resolution OCT/SLO images, the scans in the Ultrahigh resolution OCT/SLO images were superior in 85% of cases. Relatively poor quality images were attributed to lower signal-to-noise ratio, limited focusing, or media opacities. Several images that had a better signal intensity in the standard-resolution OCT/SLO system were found to show more retinal detail in the UHR system. In general, intraretinal layers in the UHR OCT/SLO images were better delineated in both coronal and longitudinal scans. Enhanced details were also seen in the outer retina/RPE/choroidal complex. The UHR OCT/SLO system produced better definition of morphological changes in several macular pathologies. CONCLUSIONS: Broadband SLD-based UHR OCT/SLO offers a compact, efficient, and economic enhancement to the currently available clinical OCT imaging systems. UHR OCT/SLO imaging enhanced the quality of the OCT C-scans, facilitated appreciation of vitreo-retinal pathologies, and improved sensitivity to small changes in the retina, and the outer retina/RPE/choroidal interface.     

Novel approach towards colour imaging using a scanning laser ophthalmoscope

AIMS—Conventional fundus imaging using a fundus camera produces colour fundus pictures. The scanning laser ophthalmoscope (SLO) has the advantages of lower levels of light exposure, improved contrast, and direct digital imaging but until now has produced monochromatic images as a laser of single wavelength is used. True representation of the fundus is possible by combining images taken using blue, green, and red lasers.
METHODS—A custom built SLO was used to capture blue, green, and red fundus images from suitable volunteers and patients with fundus disease. Images were corrected for eye movement and combined to form a colour image. Colour fundus photographs were taken using a fundus camera for comparison with the SLO image.
RESULTS—The background fundus and retinal vasculature had similar appearances with the two imaging modalities. Internal limiting membrane reflections were prominent with the SLO. Identification of new vessels in the diabetic fundus was easier with the SLO than the colour fundus photographs.
CONCLUSION—A colour SLO offers all the advantages of the present monochromatic imaging system with the added advantage of true colour representation of the fundus.

Keywords: scanning laser ophthalmoscope; fundus imaging; digital colour fundus images     

Oral fluorescein angiography with the confocal scanning laser ophthalmoscope.

OBJECTIVE: To evaluate the efficacy of oral fluorescein angiography with a confocal scanning laser ophthalmoscope (SLO) system. DESIGN: Comparative case series. PARTICIPANTS: The authors used a confocal SLO (Heidelberg Retina Angiograph [HRA]) to perform oral fluorescein angiography in 47 patients, 13 of whom were without any retinal disease and 34 with a variety of retinal diseases including macular holes and pucker, inflammatory diseases, retinal vascular diseases, and age-related macular degeneration. The images were also compared to images taken with a fundus camera after intravenous fluorescein injections in patients on whom both studies were done. INTERVENTION: Color fundus photographs were taken of each eye (30 degrees fundus camera) before drinking 4 ml of 25% sodium fluorescein mixed with 60 ml of orange juice. After oral fluorescein ingestion, images of each eye were taken with a fundus camera (TriX film) and the HRA (using 512- x 512-pixel resolution). The images were repeated at 0-, 2.5-, 5-, 7.5-, 10-, 12.5-, 15-, 20-, 25-, and 30-minute intervals. Twenty of the 47 patients underwent intravenous fluorescein angiography performed with the fundus camera. MAIN OUTCOME MEASURE: Images were analyzed by a masked reader, and foveal avascular zone visualization, branch retinal vessel identification, and image quality were scored. Statistical analysis was performed with a t test for paired data with a two-tailed test of significance (alpha = 0.05). RESULTS: Foveal avascular zone was 100% as seen in 16 eyes (47%) in the HRA machine versus 1 eye (2%) in the conventional fundus camera (P < 0.0001). The third-order branch retinal vessels were identified in 59% of eyes in the HRA versus 26% in the fundus camera group (P < 0.0001), and the image quality was considered comparable to an intravenous angiogram in 47% with the HRA versus 9% with the conventional fundus camera (P < 0.0001). CONCLUSIONS: Oral fluorescein angiography using the HRA produces sufficiently detailed images to diagnose, treat, and follow many types of retinal pathology.     

Theoretical analysis of peripheral imaging after excimer laser corneal refractive surgery for myopia

PURPOSE: To explore theoretically the retinal point images in the peripheral fields of eyes that have had excimer laser refractive surgery.University research laboratory. METHODS: Model eyes were based on Navarro's finite schematic eye, the eyes being made myopic by an increase in axial length. To simulate photorefractive keratectomy (PRK), the anterior shape and thickness of the cornea were modified. Variables included pupil size, ablation zone size, preexisting refractive error, and the addition of a blending zone. Image-quality criteria for each retinal point image were its size and the angular separation of the centroids of those parts of the image produced by rays passing through ablated and unablated corneal zones. RESULTS: In the peripheral visual field, the boundary between the ablated and unablated cornea caused a separation of the retinal image of a single point into 2 parts. The separation increased with the preexisting refractive error. Image quality was correspondingly reduced by ablation. As pupil size increased, the field angle at which the retinal image doubling first occurred decreased. Increasing the diameter of the ablation zone or using a blending zone increased the angle at which the doubling first occurred, and the blending zone improved image quality considerably. Chromatic effects appeared to be relatively unimportant. CONCLUSIONS: This analysis provides further evidence of the disadvantages of small central ablation zones in excimer laser refractive surgery and of the advantages of well-designed blending zones in improving postsurgical peripheral image quality. Image quality in the peripheral field of the pseudoemmetropic post-PRK eye is generally worse than in a naturally emmetropic eye, even though the axial image quality may be similar.     

Measuring retinal vascular diameter using the scanning laser ophthalmoscope and computer. Initial results]

The diameter of the large retinal vessels is an important factor in retinal microcirculation. A system configuration was developed that uses SLO images to measure the diameter of retinal branch vessels off-line. The place for measurement is defined in the image by the investigator, and the diameter is measured automatically. The mean standard deviation of the diameter of arterial vessels was 2.37% and for veins 3.43% by repeat measurement in sequential pictures by optimal scanner settings. The reproduction of vessel diameters was unsatisfactorily for repeat examinations. The course of these results may be changes in the fundus image connected with changes in the position of the scanner-bulbus (e.g., new examination, poor fixation). The scanner-bulbus position is not yet precisely defined and not reproducible enough.     

Fixation points and retinal sensitivity observed in reading text by patients with bilateral macular atrophy

PURPOSE: To study by use of a scanning laser ophthalmoscope(SLO). How patients with bilateral macular atrophy use their retinas in reading Japanese sentences of varying sizes. METHODS: Thirty-eight eyes of 19 patients with bilateral macular atrophy were examined. Sentences of a fixed length (MNREAD-J sentences) were projected onto the patients' retinas with the SLO, and the size of the letters was varied. Patients were asked to read aloud the sentences slowly, and both their voices and retinal images were recorded simultaneously on videotape so that we could locate the retinal area they were using for reading. We compared these fixation points in reading with simple fixation points obtained by SLO microperimetry. RESULTS: In 21 eyes, the patients used the same area of the retina in all measurements. In 15 eyes, the fixation points for reading differed from the fixation area measured by microperimetry. In 8 of the 15 eyes, the fixation area for reading changed as the letter size was altered. In 2 eyes, oral reading was impossible, and no fixation point was established. CONCLUSIONS: The combination of SLO with reading evaluation clarified the fixation area for oral reading. Multiple fixation points were thought to be present quite commonly in eyes with macular degeneration. The fixation point was thought to be determined by the macular condition and the size of the letters being read.