Visual evoked potentials in relation to visual acuity in macular disease.

PURPOSE: To investigate how central retinal function contributes to pattern visual evoked cortical potentials (PVECPs), we recorded transient and steady-state PVECPs in patients with macular disease and compared the results with those of patients with optic neuritis. The results were also evaluated for correlation with visual acuity and kinetic perimetric measurements. METHODS: PVECPs to 3 rev/s stimulation (transient) and 12 rev/s stimulation (steady-state) for check sizes 15' and 30' were obtained from all patients and age-matched healthy controls. The peak latency and amplitude of the P100 component of the transient VECP and the amplitudes of the steady-state VECP were measured and evaluated. RESULTS: Patients with macular disease produced significant delay of P100 latency and amplitude attenuation of the steady-state VECP, as compared with healthy subjects. P100 latency delay was less in patients with macular disease than in those with optic neuritis, while the attenuation rate of the steady-state VECP amplitude was similar between groups. Visual acuity was correlated with P100 latency and steady-state VECP amplitude reduction. CONCLUSIONS: Although the delay of latency was less in patients with macular disease than in those with optic neuritis, the electrophysiologic alterations that occur in macular disease demonstrate a potential for diagnostic value at the level of the retina.

Sclerostomy with an Erbium YAG Laser. The Relationship with Pulse Energy.

Purpose: To investigate the optimal pulse energy to do sclerostomy with an erbium YAG laser.Materials and Methods: The experiments were performed in enucleated porcine eyes. We changed pulse energy and examined the effects on surrounding tissue.Results: With the increase of pulse energy, the effects of the laser extended to the area surrounding the laser probe. At the threshold energy for doing full-thickness sclerostomy, the total energy was significantly higher than with higher pulse energy. And with pulse energy higher than 2 mJ, the total energy did not show any significant change. Histopathologically, the damaged area around sclerostomy became larger with the increase of pulse energy.Conclusion: The optimal energy to do full-thickness sclerostomy with this system seemed to be 2 mJ.

[Assessment of visual function before and after macular surgery by pattern visual evoked cortical potentials].

PURPOSE: To investigate pre- and postoperative visual function in patients with macular hole and those with epiretinal macular membrane (ERM) by means of visual evoked cortical potential (VECP). MATERIAL AND METHODS: VECP was recorded from 15 eyes with macular hole and 9 eyes with ERM prior to and 3 months after surgical treatment. Check sizes of 30' for transient stimulation, and 7.5', 15', 30', 60' and 120' for steady-state stimulation were applied. RESULTS: In transient VECPs, the P 100 component was prolonged and attenuated in both diseases before surgery, and it remained unchanged after surgery. In the eyes with macular hole, the amplitudes of steady-state VECPs showed significant reduction in 15' and 30' check sizes before surgery, and recovered only in 15' check size after surgery. The preoperative spatial frequency curve of ERM was lowered in the whole frequency range measured. CONCLUSIONS: VECP reflected the area of macular hole and ERM. VECP changes after surgery were considered to depend on the degree of surgical invasion.

[Sclerostomy with an erbium YAG laser--the relationship with pulse energy].

PURPOSE: To investigate the optimal pulse energy to do sclerostomy with an erbium YAG laser. MATERIALS AND METHODS: The experiments were performed in enucleated porcine eyes. We changed pulse energy and examined the effects on surrounding tissue. RESULTS: With the increase of pulse energy, the effects of the laser extended to the area surrounding the laser probe. At the threshold energy for doing full-thickness sclerostomy, the total energy was significantly higher than with higher pulse energy. And with pulse energy higher than 2 mJ, the total energy did not show any significant change. Histopathologically, the damaged area around sclerostomy became larger with the increase of pulse energy. CONCLUSION: The optimal energy to do full-thickness sclerostomy with this system seemed to be 2 mJ.

[Protective effect of nitric oxide on ischemic retina].

Nitric oxide (NO) is a free radical and was regarded as noxious to life. But recent studies show that NO is an important substance for transcellular signal transduction. It also seems to act as a neurotransmitter in the nervous system. In ischemic nerve tissue a release of glutamate is one of the critical factors that increase neuronal death, and some experiments suggest that NO may be involved in this process. Here we provide evidence that NO provides neuroprotection in ischemic retinas in vivo. Albino rabbits' eyes were subjected to 60 minutes of ischemia by raising intraocular pressure. Before ischemia the eyes were treated intravitreously with the NO-precursor L-arginine, the NO synthase-inhibitor nitro-L-arginine methyl ester hydrochloride (L-NAME), the NO-donor sodium nitroprusside (SNP), or solvent only. The amplitude of the b-wave was measured and the recovery ratio of the b-wave was analyzed hourly after reperfusion. The recovery ratio of b-wave in the eyes with L-arginine and with SNP increased more rapidly than in the controls, while the recovery ratio in the eyes with L-NAME increased in a way similar to that of the controls. These results suggest that NO plays a neuroprotective role in ischemic retina. It may be involved with S-nitrosylation of some proteins, including one of the glutamate receptors, the N-methyl-D-aspertate (NMDA) receptor.

[Sensory and electrical responses in stimulation of the macula with short-wave (407-527 nm) linear polarized light (Haidinger polarization brushes)]. / Sensorische und elektrische Antworten bei Reizung der Makula im kurzwelligen (407-527 nm) linear polarisierten Licht (Haidinger-Polarisationsbüschel).

We investigated Haidinger's (1844) entoptic polarization brushes of the macula psychophysically and electrophysiologically during rotation of plane-polarized blue (< 520 nm) light projected to a polarization screen. Psychophysically the sensitivity of the brushes was highest between 470 and 490 nm, with a steep decrease at longer wavelengths. Increase of adaptive illumination (I) above 0.1 cd/m2 increased the increment threshold (delta I) of the brushes between 407 and 515 nm about equally (delta I/I = 0.9). Comparison of the action spectrum of different photoreceptors with the spectral sensitivity of Haidinger's brushes suggested synergistic contributions of blue, green and red photoreceptors. A decrease in visual acuity to 0.01 by plus lenses did not affect the light threshold of the brushes significantly, while blurring by Bangerter foils increased the threshold markedly (about eightfold at visual acuity of 0.01). Thus, the determination of threshold of Haidinger's brushes provides the means of investigating certain macular functions behind, and widely independent of, opacities of the ocular media. While no retinal potentials (ERG) were seen during rotation of the polarizer, we obtained cortical potentials (VEP) closely related to the appearance of Haidinger's brushes in response to rotation onset of blue polarized light. The potential derived from Oz+Ol+Or consisted of a phasic negative response after a peak latency of 295 +/- 34 ms (N 295). Similar responses were also obtained to medium and long wavelengths (extrinsic windmill rotation during foveal fixation at stimulus conditions closely related to Haidinger's brushes: 3 degrees field, 2 cy/rev, 2 cd/m2, contrast 0.15). Thus VEP recording permits the comparison of entoptic and extrinsic excitation of the macula.

L-arginine and nicotinamide adenine dinucleotide phosphate alter dark voltage and accelerate light response recovery in isolated retinal rods of the frog (Rana temporaria).

Effects of intracellularly applied L-arginine and nicotinamide adenine dinucleotide phosphate (NADPH) on the dark voltage and light responses of retinal rods were studied by means of the whole-cell patch-clamp technique. In this mode an exchange of substances by diffusion between cytosol and pipette medium occurs (Pflügers Arch., 411 (1988) 204-211). In retinal rods a loss of nucleotides is reflected by a hyperpolarization of the dark voltage and by a prolongation of the light responses (Vis. Neurosci., 2 (1989) 101-108). Intracellular application of L-arginine prevented the prolongation of the light responses and NADPH accelerated the light response recovery and in addition depolarized the photoreceptor cells. The effects were similar to those observed before upon application of the nitric oxide (NO)-releasing substance sodium nitroprusside (Vis. Neurosci., 9 (1992) 205-209). It is therefore assumed that the observed effects are linked to the NO-synthase and to an activation of a guanylate cyclase by NO. It is concluded that the level of NADPH in photoreceptor cells may affect the metabolic flux of guanosine 3',5'-cyclic monophosphate (cGMP).

A case of Kearns-Shy syndrome with later onset.

We report a case of Kearns-Shy syndrome in a 44-year-old woman. She complained of bilateral ptosis, exotropia and gait disturbance. Diffuse chorioretinal degeneration and numerous punctate whitish spots were observed in both fundi. Eye movements were severely disturbed. An electroretinogram was almost nonrecordable, while visually evoked cortical potentials to pattern stimulation were normal. The dark adaptation curve showed an elevation of rod threshold. Besides such ophthalmological findings, muscle weakness, extinguished tendon reflex and healing difficulty were observed. Blood lactate, pyruvic acid and serum creatinine kinase were at high levels. A muscle biopsy showed ragged-red fibers and partial deficiency of cytochrome c oxidase. The patient is being treated with coenzyme Q, and we are now following up the therapeutic effects of this treatment.

Diabetes as risk factor of cataract: differentiation by retroillumination photography and image analysis.

We performed an epidemiological study to identify risk factors of cataract based on 2,243 subjects who underwent a general health checkup. Each subject underwent a 75-gram oral glucose tolerance test and blood chemistry analysis. The prevalence rate of cataract was higher in diabetic subjects in their 50s than in nondiabetics in the same age range (p less than 0.01). The incidence of vesicular and radial lens opacity was higher in diabetics than in nondiabetics (p less than 0.05).

[Difference of the shortening characteristics between left ventricular endocardium and epicardium as measured by radiopaque markers in experimental dogs].

This study was performed to clarify the difference of shortening characteristics between left ventricular epicardium and endocardium. Four to five pairs of radiopaque markers (lead beads, phi 0.3- 0.8 mm) were implanted just beneath the epicardium and endocardium, respectively in eight open-chest dogs. After the pericardium and thorax were closed, biplane cine-roentgenograms were obtained. The spatial distance (segment length) between any two of the markers was calculated using a digitizer-computer-plotter system. Left ventricular wall thickness (Th) was measured as a distance between epicardial and endocardial markers. The maximum left ventricular thickness (Thmax) was 9.4 +/- 3.4 mm (mean +/- SD), the minimum (THmin) 8.4 +/- 3.1 mm, and a percent increase of wall thickness [(Thmax-Thmin)/Thmin] was 12.7 +/- 6.5%. The value of epicardial segment length divided by endocardial segment length as normalized by each length at R wave of ECG was 1.088 +/- 0.071 at the end of systole and 0.979 +/- 0.016 at end diastole, indicating that endocardial segment shortened and distended more than epicardial segment during systole and diastole, respectively. Epicardial segment began to shorten 3 +/- 26 msec earlier and distend 4 +/- 50 msec earlier than endocardial one. This study revealed a small but consistent difference in the amount of shortening and its initiation and termination between the epicardium and endocardium.

[Effect of nitroglycerin on epicardial and endocardial shortening characteristics in dogs].

In 8 dogs, several paired lead beads as radiopaque markers were implanted in the subepicardial and subendocardial regions, and biplane cineradiograms were obtained after closure of the chest. The spatial distance (segment length) between the two markers in the outer and inner sides of the myocardium was calculated using a digitizer-computer-plotter system, and the effect of nitroglycerin on regional left ventricular geometry was assessed. Segment length at the R wave of the electrocardiogram (LECG R) was reduced from 39.7 +/- 11.8 (mean +/- SD) to 38.8 +/- 12.1 mm at the subepicardium and from 31.9 +/- 9.5 to 29.5 +/- 10.4 mm at the subendocardium 3 minutes after intravenous injection of 0.5 mg of nitroglycerin. Segment length at endsystole (LES) was also reduced from 38.9 +/- 11.7 to 38.2 +/- 11.8 mm at the subepicardium and from 29.6 +/- 9.2 to 27.9 +/- 9.9 mm at the subendocardium by nitroglycerin. Systolic shortening [(LECG R--LES)/LECG R] x 100) showed a slight reduction after nitroglycerin. Left ventricular wall thickness measured as a distance between subepicardial and correspondent subendocardial markers showed a slight but significant increase by nitroglycerin: Maximal thickness was increased from 10.9 +/- 3.2 to 11.4 +/- 3.3 mm, and thickness at the R wave of the electrocardiogram was also increased from 10.9 +/- 3.1 to 10.5 +/- 3.2 mm. Thickening of the wall was markedly increased at the anterior mid portion of the left ventricle but not at the base, suggesting nitroglycerin has larger effect on the former position than the latter.