Central-field stimulus thresholds in age-related macular degeneration: Associations with visual function and retinal structure

To evaluate the central-field stimulus threshold (CST) values in patients with age-related macular degeneration (AMD) and investigate the relationship between CST values and conventional visual function assessments, as well as retinal anatomical parameters, thereby exploring the role of CST in assessing anti-vascular endothelial growth factor (VEGF) therapy.

Forty patients (eighty eyes) with AMD were included in the analysis. All patients underwent complete ophthalmic examination, including slit-lamp examination, fundus examination, intraocular pressure measurement, Early Treatment Diabetic Retinopathy Study best-corrected visual acuity (BCVA), fundus photography, optical coherence tomography (OCT), OCT angiography, microperimetry (MP), and CST testing. Linear mixed-effects models and generalized linear mixed models were employed to analyze the correlations between CST and BCVA, MP, OCT features, and choroidal neovascularization (CNV) area, as well as changes in CST following anti-VEGF therapy.

Compared to normal eyes, neovascular AMD (nAMD) eyes exhibited higher CST values for white (-47.02 ± 9.02 vs. -51.09 ± 3.61 dB), blue (-52.50 ± 14.46 vs. -60.28 ± 8.60 dB), and red (-30.22 ± 8.21 vs. -36.24 ± 6.41 dB) stimuli. Approximately 39% of nAMD eyes exhibited cone-mediated vision under scotopic conditions. In nAMD eyes, BCVA was negatively correlated with blue and white CST, indicating that better BCVA was associated with higher central retinal light sensitivity. Red and blue CST were positively correlated with center retinal thickness (CRT) and CNV area (All P < 0.05). In the thicker CRT group, the blue-red CST difference decreased from -18.03 ± 10.01 dB to -22.85 ± 2.22 dB after 1 month of anti-VEGF treatment (P = 0.047), 9 of 14 eyes were cone-mediated at baseline, which decreased to 3 eyes after three months of treatment.

CST assessment revealed that both cone and rod were affected in nAMD eyes. CST was correlated with CRT and CNV area. In some nAMD patients, severe rod dysfunction leads to a shift to cone-mediated vision under scotopic conditions, but anti-VEGF therapy may ameliorate this phenomenon. These findings suggest that CST assesses the visual function of AMD patients from a more microscopic, cellular functional standpoint, which may be beneficial for monitoring AMD progression and evaluating the treatment efficacy.