Table 3.

Challenges of neuroprotection drug discovery

Challenges	Examples
Uncertain mechanisms of pathogenesis	Deprivation of neurotrophic factors, excitotoxicity, apoptosis, oxidative stress, microglia overactivation, etc
High cost of neuroprotective agents	Supplementation of neurotrophic factors, inhibition of excitotoxicity, etc
Lack of safe and sustained delivery system	Supplementation of neurotrophic factors, inhibition of apoptosis, etc
Lack of validated animal models	Experimental glaucoma with acute/chronic ocular hypertension, intravitreal injection of glutamate for excitotoxicity, etc
Uncertain therapeutic targets	Supplementation of neurotrophic factors, inhibition of excitotoxicity or apoptosis, etc
Limitations in assessment of visual field progression	Test variation, rate of mean derivation loss, determination of endpoint, etc