A method to detect progression of glaucoma using the multifocal visual evoked potential technique

Purpose To describe a method for monitoring progression of glaucoma using the multifocal visual evoked potential (mfVEP) technique. Methods Eighty-seven patients diagnosed with open-angle glaucoma were divided into two groups. Group I, comprised 43 patients who had a repeat mfVEP test within 50 days (mean 0.9 ± 0.5 months), and group II, 44 patients who had a repeat test after at least 6 months (mean 20.7 ± 9.7 months). Monocular mfVEPs were obtained using a 60-sector pattern reversal dartboard display. Monocular and interocular analyses were performed. Data from the two visits were compared. The total number of abnormal test points with P < 5% within the visual field (total scores) and number of abnormal test points within a cluster (cluster size) were calculated. Data for group I provided a measure of test–retest variability independent of disease progression. Data for group II provided a possible measure of progression. Results The difference in the total scores for group II between visit 1 and visit 2 for the interocular and monocular comparison was significant (P < 0.05) as was the difference in cluster size for the interocular comparison (P < 0.05). Group I did not show a significant change in either total score or cluster size. Conclusion The change in the total score and cluster size over time provides a possible method for assessing progression of glaucoma with the mfVEP technique. Presented in part at the Annual Meeting of the Association for Research in Vision and Ophthalmology, Fort Lauderdale, FL, May 2006.     

Repeat reliability of the multifocal visual evoked potential in normal and glaucomatous eyes

PURPOSE: To investigate the repeat reliability of the multifocal visual evoked potential (mfVEP). PATIENTS AND METHODS: Fifteen subjects with no known abnormalities of the visual system and 10 patients with glaucoma participated in the study. Monocular mfVEPs were recorded on two separate days, using a 60-sector, pattern-reversal dart board array. Within a single session, two 7-minute. recordings were obtained for each eye. The amplitude of each mfVEP response was obtained using a root mean square measure (RMS). An mfVEP ratio [10*log (RMS day 1 / RMS day 2)] provided a measure of the reproducibility of an individual response. The same calculations were performed for Run 1 compared with Run 2 within a day and Run 1 (Run 2) compared with Run 1 (Run 2) across days. RESULTS: For all 1800 mfVEP responses (60 sectors x 15 subjects x 2 eyes), the correlation between the amplitude on day 2 and the amplitude on day 1 was good (r = 0.85). The mean standard deviation (SD) of the 60 mfVEP ratios for the individual subjects was 1.63 dB for the 14-minute records (the combination of the two 7-minute recordings). On average for the 7-minute records, the mean SD across days was 1.77 dB while the mean SD within a day was 1.53 dB. The correlation within a day (r = 0.87) also was slightly larger than across days (r = 0.80). The mean SD decreased as the RMS amplitude increased. The patients' mean SD was 1.75 dB with r equal to 0.82. CONCLUSIONS: The repeat reliability of the mfVEP was good (approximately 1.6dB); in fact, it was better than that typically obtained with static automated perimetry (approximately 2.7dB). Repeat testing on separate days added surprisingly little to the variability seen with repeat testing within the same session.     

Multifocal VEP and ganglion cell damage: applications and limitations for the study of glaucoma

With the multifocal technique, visual evoked potentials (VEPs) can be recorded simultaneously from many regions of the visual field in a matter of minutes. Recently, the multifocal visual evoked potential technique (mfVEP) has generated considerable interest, especially among those seeking objective measures of glaucomatous damage. It is well accepted that significant ganglion cell damage can occur before functional deficits are detected with static automated achromatic perimetry, the "gold standard" for detecting and monitoring glaucomatous damage. In this article, we ask the following questions: What are the potential applications of the mfVEP technique? What are its limitations? To what extent will it replace or augment static automated achromatic perimetry? To answer these questions requires an understanding of the mfVEP technique, as well as techniques needed to relate its results to those of automated perimetry. describes how the mfVEP is elicited, recorded, derived and displayed. If both eyes of an individual are normal, then mfVEPs recorded for monocular stimulation of each eye are essentially identical. However, the amplitude and waveform of the mfVEP responses vary across individuals, as well as across the visual field within an individual. These variations in the normal mfVEPs are described in Section 3. In, these variations are related to cortical anatomy, and to the cortical sources contributing to the mfVEP. The mfVEP is predominantly generated in V1. Although there are undoubtedly extrastriate contributions, these contributions are probably smaller for the mfVEP than for the conventional VEP. The mfVEP is not a small version of the conventional VEP. To detect ganglion cell damage with the mfVEP requires methods for analyzing the responses and for displaying the results. In, a method for detecting ganglion cell damage is described. This method compares the monocular responses from the two eyes of an individual and produces a map of the defects. This map is in the form of a probability plot similar to the one used to display visual field defects measured with automated perimetry. Procedures are described for directly comparing these mfVEP probability plots to the probability plots for Humphrey visual fields (HVFs). The interocular mfVEP test described in will not be sensitive to bilateral damage. describes a test based upon monocular mfVEPs. The statistical basis of the monocular mfVEP test is relatively complex (see ). In any case, under many conditions the interocular test will be more sensitive and this is discussed in. summarizes a number of clinical applications of the mfVEP and concludes that the mfVEP has a place in the clinical management of glaucoma. To understand the limitations of the mfVEP, a signal-to-noise ratio (SNR) approach is described in. Using the techniques described in, the relationship between the amplitude of the mfVEP and the sensitivity loss of the HVF is discussed in. The evidence supports a simple model in which the amplitude of the signal portion, but not the noise portion, of the mfVEP response is proportional to HVF loss where HVF loss is expressed in linear, not dB, units. It is hypothesized that both the signal in the mfVEP, and the sensitivity of the HVF, are linearly related to ganglion cell loss. A theoretical approach, developed in, allows a direct comparison of the efficacy of the mfVEP and HVF in detecting glaucomatous damage. In short, when the mfVEP has a large SNR it will often be superior to the HVF in detecting damage. On the other hand, when the mfVEP has a small SNR, the HVF will probably be superior. summarizes the relative advantages of the HVF and the mfVEP. In summary, the mfVEP does have a place in the clinical management of glaucoma, although it is not likely to replace static automated achromatic perimetry in the near future. However, this is an evolving technology and the future will undoubtedly see major improvements in the mfVEP technique.     

Multifocal visual evoked potential responses in glaucoma patients with unilateral hemifield defects

PURPOSE: To determine whether the multifocal visual evoked potential (mfVEP) technique can detect damage to the visual system in the unaffected hemifields of patients with glaucoma and unilateral hemifield defects. DESIGN: Experimental study. METHODS: Monocular mfVEPs and achromatic automated perimetry (AAP) were obtained in both eyes of 16 patients with open-angle glaucoma and unilateral hemifield defects. The mfVEPs were obtained using a pattern-reversal dartboard array with 60 sectors; the entire display was 44.5 degrees in diameter. For each pair of mfVEP responses an interocular ratio of root-mean-square amplitude was calculated. These values were compared with the mean values obtained from 30 control subjects. Probability plots for MfVEP were derived. A cluster analysis was used to determine whether an mfVEP hemifield was normal or abnormal. RESULTS: Three of 60 (5.0%) mfVEP hemifields from control subjects had significant mfVEP deficits based upon a cluster of abnormal points. Significant mfVEP deficits were detected in the affected AAP hemifield in 15 of 16 (93.8%) glaucoma patients and in 6 of 16 patients in hemifields with apparently normal AAP. The percentage of hemifields with abnormal mfVEPs, but normal AAP, was significantly higher for the glaucoma patients than for the controls (37.5% vs 5.0%, P <.001, chi square).In glaucomatous eyes with achromatic visual fields defects limited to one hemifield, the mfVEP technique can detect evidence of glaucomatous damage in the unaffected hemifield.     

Pathbreaking Congressional Budget Office study shows dramatic increases in income disparities in the 1980s and 1990s: an analysis of the CBO data.

Researchers at the Center on Budget and Policy Priorities analyze the data presented in a Congressional Budget Office study that includes the best data any agency or institution has compiled on income and tax trends in recent decades. The CBO report shows that the average after-tax income of the richest 1 percent of Americans grew by $414,000 between 1979 and 1997 (after adjusting for inflation) while average after-tax income fell $100 for the poorest 20 percent of Americans and grew a modest $3,400 for those in the middle of the income spectrum. In percentage terms, after-tax income grew an average of 157 percent over this period for the top 1 percent, rose a modest 10 percent for the middle 20 percent, and was effectively unchanged for those in the bottom fifth. Income gaps between rich and poor and between the rich and the middle class widened in the 1980s and 1990s and reached their widest point on record in 1997. Even before enactment of the 2001 federal tax cuts, the percentage of income Americans pay in federal taxes has declined since 1979 for every income group. By one key measure, the percentage of income paid in federal taxes fell the most for those with the highest incomes.     

Are indications for prostatectomy in octogenarians the same as for younger men?

Prostatectomy for benign hypertrophy of the prostate is usually performed to alleviate lower urinary tract symptoms (LUTS). We assessed indications for and risks of prostatectomy in men 80 years of age and compared them to those for younger men in order to determine whether indications for prostatectomy in octogenarians are different than these for younger men. Medical records of 171 men comprised of 84 patients >80 years of age (mean 84.4) and 87 patients <65 years of age (mean 60.6) who underwent prostatectomy for benign prostate hypertrophy were reviewed. Data regarding indications for surgery, American Society of Anesthesiologists system grade, anesthesia and surgery performed, duration of hospitalization and intrahospital postoperative complications were obtained. The respective indications for surgery in the very elderly and younger patients were: urinary retention with indwelling catheter in 46 (55%) and 34 (39%) (p < 0.04), LUTS in 32 (38%) and 52 (59%) (p < 0.005), and gross hematuria in 6 (7%) and 1 (1.2%). Transurethral prostatectomy was performed in 47 elderly patients (56%) and in 30 young patients (34.5%). The other patients in each group underwent open (suprapubic prostatectomy) surgery. The overall complication rate was significantly higher in the elderly group (39% vs 22%, p < 0.05), with major complications occurring only in this group. Indications for surgery were different for octogenarians than for younger men. Morbidity and mortality rates were significantly higher among the elderly men. Age appears to be an independent risk factor for complications associated with prostatectomy. This revised version was published online in August 2006 with corrections to the Cover Date.