Cone- and rod-mediated multifocal electroretinogram in early age-related maculopathy

Abstract

Purpose To investigate the cone-and rodmediated multifocal electroretinograms (mfERG) in early age-related maculopathy (early ARM). Methods and subjects We investigated the cone-and rod-mediated mfERG in 17 eyes of 17 subjects with early ARM and 16 eyes of 16 age-matched control subjects with normal fundi. All subjects had a visual acuity of 6/12 or better. We divided the ARM subjects into two groups based on drusen size and retinal pigment epithelium abnormalitiesFa less advanced (ARM1) and a more advanced (ARM2) group. The mfERG data were compared to templates derived from the control group. We analysed the mfERG results for the central and peripheral fields (CP method) and the superior and inferior fields (SI method). Results While the mean cone results showed no statistically significant difference between the groups, the rods showed significantly delayed responses in the ARM1 group for the CP and the SI methods, but not in the ARM2 group, although there was a trend of longer latencies compared to the control group. Conclusion Our results show a functional impairment of the rods in early ARM subjects. As there is histopathological evidence showing earlier rod than cone impairment in early ARM, following the rod function with the mfERG might be helpful in diagnosis or for monitoring the progression of early ARM.

Functional loss in early age-related maculopathy: the ischaemia postreceptoral hypothesis

“…The authors suggested that delayed implicit times rather than amplitudes reflected chronic retinal ischaemia. 85 A postreceptoral involvement of rod pathways as found in studies with the mfERG in early ARM [38][39][40] is supported by Hood et al 86 who compared the rodmediated mfERG with the full-field rod ERG. They suggested that the rod-mediated mfERG responses are like the full-field rod ERG with mainly bipolar cell responses and a very small photoreceptor contribution.…”

“…32,33 The functional results of these tests cannot be given in detail but all show an impairment of cone-or rod-mediated function (or both) in early ARM. In addition, there is preferential vulnerability of the S-cone 34,35 and rod pathway [36][37][38][39][40][41][42] in early ARM over the L-and M-cone pathway. Curcio 43 has demonstrated that parafoveal rods were the first to die in early ARM and the last surviving photoreceptor in late ARM was a cone.…”

Complement factor H deficiency in aged mice causes retinal abnormalities and visual dysfunction

“…By contrast, the negligible difference between normal and cfh Ϫ/Ϫ mice under photopic conditions suggests that there is minimal impairment of cone function despite occasional histological changes in the short-wavelength cone population (see below). This is in keeping with the loss of rods and rod function in AMD (19)(20)(21)(22) and in particular impaired scotopic function in the macula (23).…”

The Clinical Applications of Multifocal Electroretinography: A Systematic Review

“…By using a special protocol for recording rod-mediated mfERG instead of the conventional cone-mediated mfERG, Feigl et al also showed that rod-mediated mfERG may be more sensitive in detecting retinal dysfunction in early AMD compared with light-adapted conemediated mfERG. 55,56 These results suggest the rod system might be affected earlier than the lightadapted cone system in early AMD. Feigl et al further demonstrated that the use of a global-flash mfERG stimulus by inserting a global bright flash between two dark frames may also detect deficits in early AMD before the conventional mfERG stimulus.…”

“…4,156 As described previously, apart from using mfERG for recording responses from the cone system, rod-mediated mfERG can also be recorded through dark-adaptation and insertion of dark frames between the multifocal flashes in order to study the topographical function of the rod system. 37,38,55,56,92,93,102 Besides using the conventional m-sequence technique in the recording of mfERG, the use of an LCD stimulator has enabled another recording technique called the cyclic-summation method. 168 This method was found to have better signal-to-noise ratio and can provide faster recording time compared to the conventional m-sequence.…”