"Do you, doctor, take the mfERG.for better or for worse?"

Multimodal Imaging of Central Retinal Disease Progression in a 2-Year Mean Follow-up of Retinitis Pigmentosa

PURPOSE

To determine the rate of progression and optimal follow-up time in patients with advanced-stage retinitis pigmentosa (RP) comparing the use of fundus autofluorescence imaging and spectral-domain optical coherence tomography.

DESIGN

Retrospective analysis of progression rate.

METHODS

Longitudinal imaging follow-up in 71 patients with retinitis pigmentosa was studied using the main outcome measurements of hyperautofluoresent ring horizontal diameter and vertical diameter along with ellipsoid zone line width from spectral-domain optical coherence tomography. Test-retest reliability and the rate of progression were calculated. The interaction between the progression rates was tested for sex, age, mode of inheritance, and baseline measurement size. Symmetry of left and right eye progression rate was also tested.

RESULTS

Significant progression was observed in >75% of patients during the 2-year mean follow-up. The mean annual progression rates of ellipsoid zone line and hyperautofluorescent ring horizontal diameter and vertical diameter were 0.45 degree (4.9%), 0.51 degree (4.1%), and 0.42 degree (4.0%), respectively. The ellipsoid zone line width and hyperautofluorescent ring horizontal diameter and vertical diameter had low test-retest variabilities of 8.9%, 9.5%, and 9.6%, respectively. This study is the first to demonstrate asymmetrical structural progression rate between right and left eye, which was found in 19% of patients. The rate of progression was significantly slower as the disease approached the fovea, supporting the theory that RP progresses in an exponential fashion. No significant interaction between progression rate and patient age, sex, or mode of inheritance was observed.

CONCLUSIONS

Fundus autofluorescence and optical coherence tomography detect progression in patients with RP reliably and with strong correlation. These parameters may be useful alongside functional assessments as the outcome measurements for future therapeutic trials. Follow-up at 1-year intervals should be adequate to efficiently detect progression.

Efficacy of oral valproic acid in patients with retinitis pigmentosa

PURPOSE

To evaluate the efficacy of valproic acid (VPA) on visual function in patients with retinitis pigmentosa (RP).

METHODS

Thirty patients (60 eyes) with typical RP were recruited for the study. Of these, 15 patients received oral VPA (500 mg once daily) for a period of 1 year (group 1) and the remaining 15 received no treatment (group 2) and served as controls. The effect of VPA on visual function was determined in terms of visual acuity, amplitude and implicit time in multifocal electroretinography (mfERG), and visual evoked response (VER) performed at presentation and at the third month, sixth month, and 1 year in both groups. Side effects of oral VPA were also monitored.

RESULTS

At 1-year follow-up, 14 of 15 patients in group 1 had improvement in median best corrected visual acuity (BCVA) from 1.8 [Range (R) 1-3] at baseline to 1.3 (R, 0.6-1.3) (P<0.001). In contrast, there was a slight decrease in median BCVA from 1.8 (0.8- 3) logarithm of the minimum angle of resolution (logMAR) at baseline to 1.83 (P=0.3) in the control arm. There was also a statistically significant increase in improvement in amplitude and latency/implicit time in mfERG and VER in this group (P<0.001). However, no such improvement was observed in the control arm.

CONCLUSIONS

Thus, VPA seems to have a positive effect on the visual functions in RP patients. Long-term studies evaluating the dose modifications, genetic analysis, and change in visual fields will add to our current knowledge.

Cone-mediated multifocal electroretinogram in early age-related maculopathy and its relationships with subjective macular function tests

PURPOSE

To investigate the multifocal electroretinogram (mfERG) and subjective function in early age-related maculopathy (ARM).

METHODS

Seventeen subjects with early ARM with visual acuity (VA) of 6/12 or better and 20 age-matched control subjects were examined. We assessed mfERGs, high and low contrast distance VA, near VA, low luminance VA, contrast sensitivity, saturated and desaturated Panel D-15 and visual fields (mean sensitivity). The mfERG responses were analysed by comparing central-overall (method 1) and superior-inferior (method 2) ratios.

RESULTS

The mfERG did not discriminate between the groups whereas colour vision (tritan deficiency), contrast sensitivity, and high contrast and low contrast VA showed significantly reduced responses for the early ARM group compared with the control group (p < or = 0.01). The mfERG first-order kernel responses correlated significantly with the desaturated D-15 in both methods (r = -0.5, p < or = 0.05). Fundus grading was not correlated with the mfERG measures.

CONCLUSIONS

Although the mfERG correlated significantly with the desaturated D-15 in early ARM, suggesting it operates at a sensitive level, it failed to discriminate between the control and ARM groups. In our sample, the subjective function measures were more sensitive than the mfERG measures.

Senescence of human multifocal electroretinogram components: a localized approach

BACKGROUND

Previous studies have shown significant age-related changes in the first-order kernel of multifocal ERG (mfERG) responses. All of these reports were based upon ring averages across the retinal field. This study was carried out to determine age-related changes in the localized response and localized variability in the mfERG parameters: N1P1 amplitude, scalar product and implicit time of P1.

METHODS

MfERG recordings from 70 normal phakic subjects (ages 9-80 years) were analyzed with VERIS 4.8. Scalar product values (for each hexagon based on ring average templates) were obtained and analyzed for age-related changes. Statistical measures such as coefficient of variation (CV) and parameters of a linear regression model were applied. Point-by-point comparisons were made across hemifields.

RESULTS

Each localized response showed a significant aging effect either in scalar product or in N1P1 amplitude. The average decline of the response was approximately 5% per decade, varying from 3.3% (peripherally) to 7.5% (perifoveally). The decline was significantly higher for the superior than for the inferior retina for amplitude parameters, corresponding to larger increases in P1 implicit time. The relative rate of change with age was similar for the nasal and the temporal retina. The average CV for all subjects at all locations was 29.4% (+/-4.1%).

CONCLUSIONS

The localized approach revealed patterns of age-related change that were not apparent in the ring averages. Information about changes in discrete retinal areas with age should make the mfERG more useful in quantitatively monitoring progression of retinal disease.