Search

To assess short-term changes in macular function after transpupillary thermotherapy (TTT) in patients with occult subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD), using focal electroretinography (FERG).Twenty-five patients with occult subfoveal CNV due to AMD were treated with TTT delivered using an infrared (810 nm) diode laser (spot size 3.0 mm, laser power 400–600 mW, duration 60 seconds). All patients were clinically evaluated before, 1 and 6 weeks after treatment. Snellen visual acuity (VA) was measured at each visit. Fluorescein angiography (FA) was performed at baseline and 6 weeks after TTT. Focal ERGs were recorded in all patients immediately before and 1 week after TTT in response to an 18-degree diameter, 41 Hz flickering spot (630 nm) centred on the fovea, presented on a steady background in Maxwellian view. A subgroup of 12 patients was also re-tested by FERG at 6-weeks post-TTT.No significant changes in mean FERG amplitude and phase were observed across the different recording sessions before and after TTT. One week after TTT, four patients had significant (>2 SD from baseline variability) increases in FERG amplitude and/or phase advances, one had a decrease in amplitude and four had phase delays, compared to baseline. The remaining 15 patients had stable FERGs. Six weeks after TTT, four patients had significant increases in FERG amplitude and/or phase advances, four had decreases in amplitude and/or phase delays, and four had stable FERGs, compared to baseline. Improvement in FERG parameters after TTT was always associated with an improvement in VA and a decrease in exudation. Patients with post-TTT FERG deterioration had stable or deteriorated clinical pictures. At either 1 or 6 weeks post-TTT, the FERG amplitude increase was inversely correlated (p < 0.05) with the baseline FERG amplitude and VA.Three major conclusions can be drawn: in a short-term follow-up, TTT was not found to be associated with significant changes in macular function; FERG improvement was associated with VA improvement, and the increase in FERG amplitude was greatest in patients with the worst baseline acuity.

Purpose: To evaluate regional cone system function after uncomplicated retinal detachment (RD) surgery, by recording focal electroretinograms (FERGs) from the central and paracentral regions of the posterior pole. Methods: FERGs in response to either a central (eccentricity: 0–2.25 deg) or a paracentral annular (2.25–9 deg) uniform field, presented on a light adapting background and sinusoidally flickered at 41 Hz (95% modulation depth, 93 cd/m2 mean luminance) were recorded from 16 eyes (16 patients) 2 weeks to 420 months following uncomplicated RD surgery (encircling procedure with or without scleral buckling). Pre-operatively, 10 out of 16 eyes had a macular RD. Mean time elapsed from onset of symptoms to surgery was 20 days (range: 5–90 days). Post-operatively, visual acuity ranged 0.1 to 1.0. Eight age-matched normal subjects served as controls. Amplitude and phase of the FERG fundamental harmonic were measured. Results: Compared to control eyes, affected eyes’ central and paracentral FERGs were on average reduced in amplitude (by 40% and 28%, respectively, p<0.01) and delayed in phase (by 70 and 100 degrees, respectively, p<0.01). Eyes with a macular RD did not differ in FERG amplitude or phase from eyes that had a peripheral RD. In individual affected eyes, central, but not paracentral FERG amplitudes were negatively correlated (p=0.05) with time elapsed from onset of symptoms to surgery. Conclusions: Central and paracentral cone system dysfunction may be detected even at lengthy time intervals from retinal reattachment, independent of the presence of a pre-operative macular RD. The extent of central loss appears to be inversely related to RD duration, in agreement with previous reflectometric findings on foveal cone photopigment density [Liem et al., 1994; Ophthalmology 10: 1945-51].

Objectives: The flicker electroretinogram (FERG) consists mainly of a linear (fundamental, 1F) and a non linear (second harmonic, 2F) component. Previous results indicate that 2F originates more proximally in the retina than 1F, and that retinitis pigmentosa (RP) may affect 2F to a greater extent than 1F. The aim of this study was to evaluate FERG 1F and 2F abnormalities in RP as a function of the stimulus temporal frequency (TF).

In normal subjects, the steady‐state electroretinograrn in response to contrast reversing gratings (PERG), is spatially band‐pass tuned in amplitude, with a maximum at intermediate spatial frequencies and an attenuation at lower and higher ones. The amplitude attenuation at low spatial frequencies is believed to reflect centre‐surround antagonistic interactions in the receptive fields of inner retinal neurons. The aim of this study was to evaluate the PERG spatial tuning in multiple sclerosis (MS) patients without a previous optic neuritis history. Steady‐state PERGs in response to counterphase‐modulated (8 Hz) sinusoidal gratings of variable spatial frequency (0.6, 1.0, 1.4, 2.2 and 4.8 c/deg), were recorded from 18 patients with definite or probable MS and no history of optic neuritis (ON‐). Nine of them had no signs of subclinical optic nerve demyelination (asymptomatic) in either eye, while nine had symptoms or signs of optic pathways involvement (symptomatic) in one or both eyes. Results were compared with those obtained from 10 MS patients with a previous history of optic neuritis (ON+) in one or both eyes, as well as from 21 age‐matched controls. The amplitudes and phases of the responses' 2nd harmonics were measured. Compared with the controls, asymptomatic ON‐patients showed selective losses in mean PERG amplitudes at medium and high (1.0–4.8 c/deg) spatial frequencies. Symptomatic ON‐patients and ON+patients had reductions in mean PERG amplitudes, with respect to controls, involving the whole spatial frequency range, but with greater losses at medium‐high (1.0–4.8 c/deg) than at lower spatial frequencies. In all patients' groups, the average PERG spatial tuning function differed significantly from that of the controls, assuming a low‐pass instead of the normal band‐pass shape. The PERG phase was delayed in ON+but not in ON‐patients, as compared to controls. However, the phase delay was independent of spatial frequency. In both ON‐and ON+patients, losses in PERG amplitude and spatial tuning tended to be associated with corresponding abnormalities in perimetric sensitivity, visual acuity, colour vision and transient visual evoked potential (WP) latency. The results indicate that abnormalities of the spatial tuning of steady‐state PERG can be found in MS patients without either optic neuritis or signs of subclinical optic nerve demyelination. These changes may reflect a retinal dysfunction, developing early in the course of MS, due to a loss of specific subpopulations of inner neurons, changes in lateral interactions of their receptive fields, or both.