Y. Grall

Functional assessment of macular hole surgery by scanning laser ophthalmoscopy.

OBJECTIVE This study aimed to evaluate more precisely the benefit of macular hole surgery. DESIGN The design was a prospective study of 40 eyes in 40 patients examined before and after surgery of full-thickness macular holes with a scanning laser ophthalmoscope (SLO). PARTICIPANTS Forty patients with full-thickness macular holes participated. Three of the holes were stage 2, 23 were stage 3, and 14 were stage 4. INTERVENTION The SLO examination consisted of macular imaging and assessment of macular function using tests produced by an acousto-optical modulator. MAIN OUTCOME MEASURES Preferred retinal locus (PRL) was determined, visual acuity was measured, and scotoma was detected by microscotometry and by the line test (modified Watzke-Allen test). RESULTS Anatomic success was achieved in 32 of 40 cases as assessed biomicroscopically. On SLO examination before surgery, macular holes were seen as a central bright round disc outlined by a thin dark edge surrounded by a dark ring and a less dark area with ill-defined limits. In all cases, the PRL was located on the upper edge of the hole, a scotoma was always detected inside the hole, and the line was seen as broken in 26 of 32 cases. After surgery, the hole closed completely in 25 of 32 eyes; it disappeared from 14 of these 25 eyes and was replaced by a dark or clear disc in 11. In the other seven successful cases, its size shrank and its edge flattened but remained faintly visible. The hole remained unchanged in eight cases. Eccentric PRL became central in 28 of 32 cases. The scotoma disappeared in 23 of 32 cases. The line was seen as continuous in 24 of 32 cases. Complete anatomic and functional successes were achieved in 19 of the 32 cases of macular hole closure. CONCLUSION The SLO examination allows accurate assessment of the anatomic and functional results of macular hole surgery. Various degrees of functional success were recorded, depending on the test used.

Eye fixations near corners : evidence for a centre of gravity calculation based on contrast, rather than luminance or curvature

Subjects scanned line drawings of polygons in order to count the number of corners. The positions their eyes fixated were studied as a function of the size of the angle and whether the apex of the angle was present or absent. The results showed that the eyes tended to land at a position near the centre of gravity of the corner configurations. The observed landing positions were coherent with the hypothesis that the centre of gravity was calculated within an attentional spotlight centered on the apex of the corners, and that the calculation was based not on the total luminance distribution, nor on the distribution of energy in a neurophysiologically motivated curvature detector, but simply on the basis of a contrast detector.

Scanning laser ophthalmoscope imaging of fluorescein-labelled blood cells

Abstract• Purpose: To demonstrate the feasibility of a technique for the visualization by scanning laser ophthalmoscope (SLO) of fluores cein-labelled autologous leukocytes and platelets in retinal vessels. • Method: Individual blood samples from rats and rabbits were centrifuged to isolate platelets and leukocytes, then passively labelled with fluorescein and reinjected into the same animal. An SLO was used to visualize and record cell displacement in the retinal circulation. Labelled platelets were analysed by flow cytometry. • Results: By SLO, platelets appeared as a heterogeneous particle flow, and individual leukocytes appearing as brighter spots could easily be traced. Flow cytometry showed that after labelling platelets were well individualized and their size was slightly increased. • Conclusion: Circulating blood cells can be visualized in retinal vessels by a simple method consisting of passive labelling of autologous platelets and leukocytes by fluorescein. No platelet toxicity was detected. This method could be applied to the study of blood cell movement in human retinal vascular diseases.

Contribution of scanning laser ophthalmoscopy to the functional investigation of subjects with macular holes

A study was designed to validate a functional investigation performed with the scanning laser ophthalmoscope before surgery for macular holes in 12 eyes: The assessment included fundus examination, a functional examination resulting in evaluation of the preferred retinal lows, visual acuity and recording of visual evoked potentials. The preferred retinal locus was evaluated by presenting a small square area, and visual acuity was determined by means of calibrated figures. The visual evoked potentials were evoked by three alternating checkerboards (check size, 30′, 2 Hz) centered over the hole and seen at an angle of 6.5 × 6.5°, 2.5 × 2.5° and 6.5 × 6.5° with central exclusion of 2.5 × 2.5°. The appearance of the fundus visualized by scanning laser ophthalmoscopy consisted of a clear central disk corresponding to the hole, surrounded by a very dark ring, associated with a second, less dark ring with unclear margins. Fixation was unstable in one case with a visual acuity of 20/70. In 11 cases, fixation was localized to the superior retina with a visual acuity superior to 20/70. The visual evoked potentials evoked by 6.5 × 6.5° were discernible in all 12 eyes; visual evoked potential by annular stimuli were discernible in 11 cases. The 2.5 × 2.5° stimulus evoked no response in eight cases, proving the area of the hole was nonfunctional. A response was recorded in the four other cases, where the dimension of the holes was less than 2°. The results of this scanning laser ophthalmoscopic assessment demonstrated a precise evaluation of the residual macular function in the cases of full-thickness macular holes.

Electrophysiological exploration of visual function in mitochondrial diseases

In a group of 10 children (ranging from 5 months to 15 years old) affected by diseases with mitochondrial dysfunction, 4 suffered from mitochondrial myopathy, 4 from mitochondrial encephalopathy and 2 from Friedreichs ataxia. The clinically detectable visual impairment consisted of 3 grey ocular fundi (the other 7 were normal) associated, in 2 subjects, with a mild nystagmus. Electrophysiological assessment, consisting of ERGs and flash VEPs, was systematically performed. The normal ERGs in all subjects confirmed the normal functioning of retinal electrogenesis. In contrast, the VEPs of 6 out of 10 subjects were modified: in 2 of the 4 subjects with mitochondrial myopathy, the VEPs had a hyperamplitude; in the 2 subjects with Friedreichs ataxia, the implicit time of the principal VEP peaks was increased, together with a hyperamplitude in 1 case; lastly, in 2 of the 4 subjects with mitochondrial encephalopathy, the VEPs were altered. These modifications reflected visual pathway conduction disorders with no clinical expression. Various underlying pathophysiological mechanisms possibly responsible for these modifications are discussed.

Colored focal visual evoked potentials by cathode ray tube versus scanning laser ophthalmosope

We compared the focal visual evoked potentials obtained in 52 young subjects with normal vision, evoked by means of three alternating black/color checkerboards generated by a trichromic cathode ray tube (dominant wavelength, 514 nm; colorimetric purity, 0.45) and by means of a scanning laser ophthalmoscope (argon laser beam, 514 nm; colorimetric purity, ≈ 1). These three checkerboards, with an area of 3.5° × 3.5° (stimulating the fovea), then with an area of 3.5° × 3.5° with a central exclusion of 1.5° × 1.5° (stimulating the perifoveola) and finally with an area of 1.5° × 1.5° (stimulating the foveola) were presented within a field (8° × 8°) of homogeneous luminance of 170 cd/m2 and 1500 cd/m2, respectively. Their check sizes were 30′, with a reversal temporal frequency of 0.75 Hz. The transient focal visual evoked potentials recorded with these three stimuli generated by the two types of stimulators were clearly detected for at least 85% of subjects. Their characteristics (waveform, amplitude and culmination times of the different waves) were comparable, regardless of the stimulator used (cathode ray tube or scanning laser ophthalmoscope). These results suggest that, under these various conditions of luminance and colorimetric purity, the neurophysiologic circuits tested function in identical ways. The focal visual evoked potential signs, now clearly defined by means of stimuli generated by cathode ray tubes, therefore apparently can be applied to the focal visual evoked potential evoked by stimuli generated by the scanning laser ophthalmoscope.

Visual Evoked Potentials and Colour Pattern Stimulations

After a historical account and a brief description of the techniques of signal analysis used in the Service Central de Biophysique et Medecine Nucleaire (Hospital Lariboisiere), the authors present the experiments they have undertaken, concerning coloured stimulations. These experiments were carried out in three steps: (a) coloured stimulations on cathode-ray screen, with constant luminance, concerning 8 healthy volunteers; (b) coloured stimulations on patterned screen (pattern reversal), concerning 31 healthy volunteers; (c) development and first stimulations with increased reliability, and offering new possibilities of coloured stimulation. The results evidence two different groups of electrophysiological responses, distinctly related to the presence or absence of a morphoscopic structure in the stimulation. Besides, a significant increase in latencies is observed with blue stimulation.

Correlation functions in the analysis of visual evoked potentials

Our “vision” laboratory has been working for several years on stimulation methods and data processing. We present here the results of an analysis of correlation functions between VEPs obtained by flashes and patterned stimulations. This study provides additional information about possible interpretations.

3321 Quantification of metamorphopsia using a scanning laser ophthalmoscope (SLO)

PURPOSE; To assess metamorphopsia in patients with epimacular membrane, using a SLO. METHOD& A SLO wa.s used to project I7 spots on the retina. A first spot considered as a reference appears at a constant place above a central flickering spot. The task consists in moving 15 other spots, appearing one after the other, in order to draw two regular squares as shown in the figure below. ~QQE: C-m of Bkcd-W Barrier (BRB) inward and outward fluxes of flu”#sceia inmlmalindivid”alsatlddiahdicpatialtswithml zically visible rciim&y using high-resdution vitmus

3324 SLO angiography using autologous fluorescent labeled platelets and leukocytes in rabbits

PURPOSE; To assess metamorphopsia in patients with epimacular membrane, using a SLO. METHOD& A SLO wa.s used to project I7 spots on the retina. A first spot considered as a reference appears at a constant place above a central flickering spot. The task consists in moving 15 other spots, appearing one after the other, in order to draw two regular squares as shown in the figure below. ~QQE: C-m of Bkcd-W Barrier (BRB) inward and outward fluxes of flu”#sceia inmlmalindivid”alsatlddiahdicpatialtswithml zically visible rciim&y using high-resdution vitmus