A contact lens electrode with built-in high intensity white light-emitting diodes. A contact lens electrode with built-in white LEDs.

We determined the clinical usefulness of a new contact lens electrode with built-in, white light-emitting diodes (LEDs) for full-field electroretinograms (ERGs). Three, high-brightness white LEDs were incorporated into a contact lens electrode and served as the source for the stimulus and the background. The stimulus intensity, stimulus duration and background illumination were regulated by a small LED control device. Maximum stimulus and background intensities were 3.9 and 3.6 log cd/m2, respectively. We successfully recorded intensity-response series for scotopic and photopic ERGs. We also recorded a duration-series for photopic ERGs, and ERGs that were comparable to the ISCEV standardized ERGs. The compactness and ease of using this system suggest that it will be clinically useful under different conditions.

Focal macular ERGs in eyes after removal of macular ILM during macular hole surgery.

PURPOSE: The removal of the internal limiting membrane (ILM) for traction maculopathy has recently been advocated. However, it is generally believed that the ILM plays an important role in retinal function, because it is the basal lamina of the Müller cells that are involved in the generation of the electroretinogram (ERG) b-wave. To date, there has been no objective assessment of retinal function on removing the ILM. In this study, the changes of each component of the focal macular electroretinograms (FMERGs) were investigated in eyes before and after the ILM was removed in the macular area during surgery for idiopathic macular holes (IMHs). METHODS: FMERGs were elicited by a 15 degrees stimulus centered on the fovea and monitored by an infrared fundus camera. FMERGs were recorded from 49 eyes of 48 patients with IMHs before and 6 weeks after anatomically successful macular hole surgery. Whether an eye had or did not have the ILM removed was randomly determined. The ILM was removed in 30 eyes (ILM-off group) and was not removed in 19 eyes (ILM-on group). Six months after surgery, the same examination was performed in 27 eyes of the ILM-off group and in 15 eyes of the ILM-on group. The amplitudes and implicit times of the a- and b-waves and the mean amplitudes and implicit times of the first three oscillatory potentials (OP1 to OP3) were compared before and after surgery within and between the groups. RESULTS: Visual acuity increased significantly after surgery in both groups. In the ILM-on group, the amplitude of the a- and b-waves and the OPs increased significantly 6 months after surgery (P: = 0.0093, P: = 0.0019, P: = 0.0024, respectively, paired t-test). In the ILM-off group, the a-wave amplitude and mean OP amplitudes were significantly larger 6 months after surgery (P: = 0.0077, P: = 0.0030, respectively, paired t-test). The b-wave amplitude, however, did not change significantly. The percentage increase in the b-wave amplitude 6 months after surgery was significantly higher in the ILM-on group (44.0%) than in the ILM-off group (15.0%; P: = 0.037, t-test). CONCLUSIONS: The removal of the ILM had no adverse effect on visual acuity. However, the selective delay of recovery of the FMERG b-wave 6 months after surgery suggests an alteration of retinal physiology in the macular region.

Amplitude decrease of photopic ERG b-wave at higher stimulus intensities in humans.

PURPOSE: The b-wave of the human photopic electroretinogram (ERG) elicited by a short-flash increases in amplitude with increasing stimulus intensities at lower stimulus levels, but then decreases at higher stimulus intensities. The purpose of the present study was to explore this phenomenon in more detail, using short- and long-flash stimuli. METHODS: The intensity-response functions of the b-wave elicited by short- and long-flashes were compared from threshold to higher stimulus intensities in 5 normal subjects. Short- and long-flash ERGs were elicited under rod-saturating background levels using white light-emitting diodes built into a contact lens electrode. RESULTS: Whereas the amplitude of the short-flash b-wave decreased at higher intensities, the amplitude of the long-flash ERG b-wave did not decrease but plateaued. The long-flash ERG d-wave or OFF-response decreased at higher stimulus levels as did the short-flash elicited b-wave. CONCLUSIONS: Because it is widely accepted that the b-wave and the OFF-response d-wave interact to produce a single positive response, our results suggest that the decrease in the b-wave amplitude at high stimulus intensity is caused by the decrease of the d-wave at the higher stimulus intensities.

Multifocal electroretinogram in occult macular dystrophy.

PURPOSE: Occult macular dystrophy (OMD) is an unusual macular dystrophy presenting with an essentially normal fundus and fluorescein angiography but with progressive central visual loss. The authors studied the function of local retinal areas in the posterior pole of patients with OMD using multifocal electroretinograms (ERGs). METHODS: Multifocal ERGs were recorded using the Visual Evoked Response Imaging System with 61 hexagonal elements within a visual field of 30 degrees radius from 8 OMD patients and 20 age-matched, normal subjects. The amplitudes and implicit times of the patients and normal control subjects were compared at the various retinal eccentricities. RESULTs. The amplitudes of the multifocal ERGs in the OMD patients were markedly reduced in the central 7 degrees of the fovea. The difference of the ERG amplitudes between OMD and normal subjects became smaller toward the peripheral retina. Most OMD patients had slight but significantly delayed implicit times across the whole testing field, and the differences between the OMD and the normal subjects did not change with retinal eccentricity. CONCLUSIONS: Our results for multifocal ERG amplitudes support the idea that OMD patients have localized retinal dysfunction distal to the ganglion cells in the central retina. The delayed implicit times across the whole test field suggest that the retinal dysfunction has a broader boundary than expected by ERG amplitudes and psychophysical perimetric results.

Amplitude increase of the multifocal electroretinogram during light adaptation.

PURPOSE: To determine using the multifocal ERG technique whether there are any regional differences in the increase in the amplitude of cone electroretinograms (ERGs) during light adaptation. METHODS: Multifocal ERGs were recorded with the Visual Evoked Response Imaging System from five normal subjects. Thirty-seven hexagonal stimulus elements and a recording time of 60 seconds were used. After 20 minutes of dark adaptation, multifocal ERGs were repeatedly recorded every 2 minutes over a period of 16 minutes. The amplitudes of the multifocal ERGs at different eccentricities were compared during the 16 minutes of light adaptation. RESULTS: During the 16 minutes of light adaptation, the summed responses of the multifocal ERGs increased in amplitude an average of 36% and 47% for the negative and positive components, respectively. The magnitude of increase was minimal in the central retina at 22% and was significantly larger in the peripheral retina at 58%. The implicit time was slightly increased (<4%) with light adaptation, but there were no regional differences. CONCLUSIONS: The results demonstrated that there are topographic variations in the amplitude increase of cone ERGs during light adaptation. This topographic variation indicates that the mechanism for the increase must be based on known regional differences in the retina.