The human eye is capable of detecting even the smallest unit of light by identifying the presence of photon, the smallest unit of light in the dark.

The finding was announced in the journal of Nature Communications. This study is vital in concluding the study in search for the limit of what the human eye can see.

"If you imagine this, it is remarkable: a photon, the smallest physical entity with quantum properties of which light consists, is interacting with a biological system consisting of billions of cells, all in a warm and wet environment," Alipasha Vaziri, lead researcher said in a statement published by the International Business Times. "The most amazing thing is that it's not like seeing light. It's almost a feeling, at the threshold of imagination," Vaziri added.

Three subjects underwent an intense experimentation to measure the limits of their vision. The experiment required the subject to sit in the dark room for 40 minutes and look into an optical system. They were asked to push a button where sounds can be heard. Some light accompanied the sounds at some point by a single photon. The light set-up in the experiment is called spontaneous parametric down-conversion, or SPDC.

They were asked to confidently rate if their answer to seeing the photon in a scale of 1 to 3. Although volunteers made wrong guesses, they were able to make correct answers. The explanation is that 90 percent of photons that enter the front of the eye never reaches the back. But their level of confidence with their answers is higher when they are right.

The data was gathered through 30,000 repeated trials.Scientists say that the rate of testing supports their claim. Based on the experiment, the volunteers managed to detect photons in 51.6 percent of the time.

"The response that the photon generates survives all the way to the level of our awareness despite the ubiquitous background noise. Any man-made detector would need to be cooled and isolated from noise to behave the same way," Vaziri said in a statement published by Phys.Org.

The researchers say now that they know the human eye can detect photons, they would like to find out how the biological system achieve this sensitivity despite the presence of noise. To answer that, more experiments have to be conducted.