Precision with opamp in transimpedance amplifier configuration with LED as photodiode
You start with "how accurate do I need?" then move on to "How do I get it?"  Never start the second until you know the first.

The example you cite shows a 0.3% error.  You can work for a decade without needing that sort of precision.

For this particular case, to get better than that, you would need to start with a very precise \$1.000M\Omega\$ resistor.  Then, you need an opamp with small bias voltages and currents.