Subjects With Unilateral Neovascular AMD Have Bilateral Delays in Rod-Mediated Phototransduction Activation Kinetics and in Dark Adaptation Recovery

Abstract

Patients with unilateral wet AMD display rod dysfunction in both their wet and dry AMD eyes. A subset of these patients display, in addition, bilateral cone dysfunction and delayed rod phototransduction activation, which may either reflect extensive morphologic change in advanced stages of AMD and/or represent a distinct phenotypic manifestation within the heterogeneous context of AMD as a disease.

ISCEV extended protocol for derivation and analysis of the strong flash rod-isolated ERG a-wave

“…Rod-isolated ERG components may be obtained by subtracting cone-mediated responses as detailed below. Information about the dynamics of rod phototransduction can be derived from analysis of the initial portion of the rod-isolated ERG a-wave [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. This extended protocol describes the recording of ERGs to the same strong flash under both dark-adapted and light-adapted (LA) or photopic rod-saturating conditions.…”

“…However, white flashes are consistent with ISCEV standard ERG stimuli and have also been widely used to derive the rod-isolated ERG a-wave (e.g. [10,[12][13][14]).…”

“…(d) Scotopic stimulus flash strengths. Studies isolating and fitting models to the rodmediated ERG a-wave have used a series of strong flashes [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. However, shortened protocols based on one or two flashes have been proposed for clinical use [7,10].…”

“…A large number of studies have used mathematical models to fit the leading edge of the rod-isolated a-wave to extract parameters relating to rod phototransduction [2][3][4][5][6][7][8][9][10][11][12][13][14]. However, as there are some important limitations [15] to such analysis (discussed in ''Appendix 2''), this protocol does not endorse the use of a particular mathematical model at this time.…”

“…The inter-stimulus interval is a minimum of 3 s. This allows cone recovery between flashes and is comfortable for most patients, and an interval of 3 s allows efficient averaging if needed. (h) Averaging may be used to improve the signal/ noise ratio, and typically 3-10 responses have been averaged in previous studies [5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”