You could even use LEDs to measure the pulses. See here for an example: LED Camera | Blinkenlight. Of course you would need to match the LED to the meter's led. You have to make sure that the LED will have a longer wavelength then the meter's LED.
A phototransistor might be a better choice though. I would expect that an infrared sensitive transistor should be sufficient. An LDR is definitely to slow for your application.