Transiently raised intraocular pressure reveals pattern electroretinogram losses in ocular hypertension.

PURPOSE: It is known that the pattern electroretinogram (PERG) of normal subjects is reduced temporarily after short-term elevation of intraocular pressure (IOP). The authors evaluated PERG changes in ocular hypertension during and after transient IOP elevation. METHODS: Steady state (8 Hz) PERGs to sinusoidal gratings (1.7 cyc/deg spatial frequency) were recorded in seven untreated patients with ocular hypertension at medium risk (maximum IOP, 22 to 25 mm Hg; cup-disk ratio, 0.6 to 0.7; normal Humphrey 30-2 visual field results; positive family history), as well as in six age-matched normal subjects. Recordings were obtained for the baseline condition during a short-term (6-minute) IOP elevation (to 30 mm Hg) by using a suction cup apparatus and during a 6-minute recovery period after removal of the apparatus. RESULTS: During IOP elevation, PERG amplitudes were reduced significantly from baseline values in normal subjects and patients. However, PERG losses were significantly greater in patients (average loss from baseline after 4 minutes of IOP elevation: 72% +/- 7.6%) compared to controls (average loss after 2 minutes of IOP elevation: 40% +/- 7.5%). In the recovery phase, mean PERG amplitude returned to baseline values in normal subjects but not in patients, whose recovery took longer. In normal subjects, PERG phase did not change either during or after IOP elevation. In patients, however, PERG phase showed a delay from baseline during and after IOP elevation (average delay after 6 minutes of recovery: -41.1 degrees +/- 13 degrees). CONCLUSIONS: Results indicate that increasing IOP with scleral suction produces greater PERG losses in eyes with ocular hypertension than in normal eyes. This suggests that the inner retina of eyes with ocular hypertension may have a heightened sensitivity to vascular or mechanical changes induced by transient IOP elevation.

Macular flicker electroretinograms in Best vitelliform dystrophy.

PURPOSE: The aim of this study was to evaluate the function of the neurosensory retina in Best vitelliform macular dystrophy (BMD) by recording the focal electroretinogram (ERG) fundamental and 2nd harmonic components, which are known to be dominated by receptoral and postreceptoral activity, respectively. METHODS: FERGs were recorded in response to a uniform field (9 x 9 deg) flickered sinusoidally at either 8 Hz or 32 Hz (peak frequencies for the 2nd and fundamental harmonic, respectively). The fundamental component of the response to the 32-Hz stimulus and the 2nd harmonic of the response to the 8-Hz stimulus were measured in their amplitudes and phases. The fundamental-2nd harmonic amplitude ratio was taken as an index of the relative changes in the FERG components. Eleven patients with BMD and vitelliform stage macular lesions were evaluated. Results were compared with those obtained from 13 patients with Type 2 Stargardt macular dystrophy (STD) according to the Noble and Carr Classification, and 29 normal control subjects. Four BMD and four STD patients were also followed electrophysiologically over a 48 month period. RESULTS: Compared to controls, BMD patients showed losses of both FERG fundamental and 2nd harmonic amplitudes, and an increase in the fundamental and increase in the fundamental-2nd harmonic ratio. STD patients also showed losses of both fundamental and 2nd harmonic, but the fundamental-2nd harmonic ratio was normal. In BMD patients, but not in those with STD, the fundamental amplitude tended to decrease over the follow-up period. CONCLUSIONS: The results indicate that BMD involves neurosensory abnormalities early in the disease process. The increased fundamental-2nd harmonic ratio suggests that a postreceptoral dysfunction may be present in addition to that of photoreceptors. This differs from STD, where losses appear to affect primarily the receptoral retina. Receptoral losses in BMD may progress throughout the medium-term follow up.

The first and second harmonics of the macular flicker electroretinogram: differential effects of retinal diseases.

We evaluated the effects of retinal diseases on the macular electroretinogram first and second harmonic components, which are dominated by outer and inner retinal activity, respectively. Macular electroretinograms in response to a uniform field (9 degrees x 9 degrees) flickering sinusoidally at either 32 or 8 Hz (peak frequencies of the first and second harmonics, respectively) were recorded in 14 patients with maculopathies involving photoreceptors (e.g., age-related macular degeneration), in 16 patients with postreceptoral macular diseases (e.g., branch occlusion of central retinal artery), and in 38 normal controls. Amplitude and phase of the first and second harmonic response components were evaluated by Fourier analysis. When compared to controls, patients with photoreceptor diseases had reduction in both first and second harmonic mean amplitudes and second harmonic phase delay; patients with postreceptoral diseases had normal first harmonic components but reduced and delayed second harmonic components. A discriminant analysis, by using first and second harmonic values, correctly classified 13 of 14 patients with photoreceptor diseases and 14 of 16 patients with postreceptoral disorders. These results indicate that combined evaluation of the macular electroretinogram first and second harmonic components is a useful test for identifying the site(s) of retinal dysfunction in patients with macular diseases.

Postreceptoral contribution to macular dysfunction in retinitis pigmentosa.

PURPOSE: To understand the sites of macular dysfunction in retinitis pigmentosa by evaluating focal electroretinogram (FERG) fundamental and second harmonic components, which are dominated by the activity of the outer and inner retina, respectively. METHODS: FERGs were recorded in response to a uniform field (9 degrees x 9 degrees) flickered sinusoidally at either 8 Hz or 32 Hz. The fundamental components of the responses to both the 8-Hz and 32-Hz stimuli and the second harmonic of the response to the 8-Hz stimulus were measured in their amplitudes and phases. Normal subjects (n = 17), as well as patients with typical retinitis pigmentosa (n = 22), cone dystrophy (CD, n = 7) and X-linked congenital retinoschisis (XLR, n = 5) served as subjects. The fundamental (32-Hz)-second harmonic (8 Hz) amplitude ratio was taken as an index of the relative function of outer-inner layers of the macula. RESULTS: Compared to controls, patients with retinitis pigmentosa showed losses of both FERG fundamental and second harmonic and an increase of the fundamental-second harmonic ratio. Patients with CD also showed losses of both fundamental and second harmonic, but the fundamental-second harmonic ratio was normal. Patients with XLR had a selective loss of the second harmonic, resulting in an increased fundamental-second harmonic ratio. On average, the fundamental-second harmonic ratio of patients with retinitis pigmentosa tended to increase with age. CONCLUSIONS: The results suggest that in retinitis pigmentosa, both receptoral and postreceptoral sites contribute to macular dysfunction. This differs from CD and XLR, where losses appear more selective for the outer and the inner retina. Postreceptoral losses in retinitis pigmentosa may become larger with increasing age.

Binocular interactions and steady-state VEPs. A study in normal and defective binocular vision (Part II).

BACKGROUND: Recent evidence indicates that an index of binocular activity may be found in some properties of steady-state visual evoked potentials (VEPs), such as amplitude facilitation and phase shortening. We evaluated binocular interactions with steady-state VEPs in normal subjects as well as in patients with concomitant strabismus and defective binocular vision. METHODS: Steady-state (8-Hz) VEPs to counterphased sinusoidal gratings (1.2 c/deg spatial frequency) of low contrast (3.2%) were recorded in 19 esotropic patients and in 18 age-matched controls. Patients had either anomalous retinal correspondence (ARC, n = 10) or suppression (n = 9) in casual seeing conditions (striated glasses). In all subjects, both binocular and monocular VEPs displayed a major component at twice the stimulation frequency (second harmonic), whose amplitude and phase were measured. A binocular interaction index was obtained by comparing binocular VEPs (BVEPs) with the sum (vectorial) of the two monocular VEPs (SMVEPs). RESULTS: In normal subjects, BVEPs were larger in amplitude than SMVEPs (facilitation), and shortened in latency (phase). On average, both ARC and suppression patients displayed loss in amplitude facilitation and absence of phase shortening. However, 50% of ARC patients showed clear VEP facilitation. In both ARC and suppression patients, the amplitude ratio BVEP/SMVEP was negatively correlated with the amount of the angle of deviation. CONCLUSION: These results suggest that losses in amplitude facilitation and phase shortening of binocular steady-state VEPs reflect abnormal binocular interactions associated with different forms of sensorial adaptation in concomitant strabismus.

Pattern electroretinogram as a function of spatial frequency after retrobulbar optic neuritis.

Steady-state (8-Hz) pattern electroretinograms in response to counterphased sinusoidal gratings of variable spatial frequency (0.6-4.8 c/deg) were recorded in 17 patients who had had retrobulbar optic neuritis in one or both eyes (23 eyes with a clinical history of optic neuritis) and in 21 age-matched normal subjects. Amplitude and phase of the Fourier-analyzed pattern electroretinogram second harmonic were measured. The mean pattern electroretinogram amplitude of patients was significantly reduced compared with that of controls. Amplitude reductions were more marked at intermediate (1-1.4 c/deg) than at lower or higher spatial frequencies. Therefore, the average amplitude versus spatial frequency response function differed significantly in patients compared with controls, displaying a lowpass instead of a band-pass shape. No significant differences in the mean pattern electroretinogram phase were observed between groups at any spatial frequency. These results indicate spatial frequency-dependent abnormalities in the pattern electroretinogram amplitude after optic neuritis, suggesting a specific loss of retinal neurons sensitive to stimuli of intermediate spatial frequencies.

[Use of pefloxacin in boutonneuse fever]. / Sull'impiego della pefloxacina nella febbre bottonosa.

On the basis of previous studies, the authors tested pefloxacin, a new generation quinolone, for the treatment of Mediterranean spotted fever. Treatment with this drug brought about complete recovery with rapid subsidence of clinical symptoms and normalization of instrumental and laboratory parameters. This antibiotic should therefore be listed as one of the agents suitable for combatting rickettsial infections and its use should be encouraged in view of its easy handling, excellent compliance and the possibility for oral administration.