Roommates & Soulmates

Ch181: Paige's Someday

Convincing her parents to let her ditch this holiday in favour of visiting her boyfriend's parents had been quite the effort, but in the end it was worth it. Between the baby pictures Jon hadn't wanted his mom to share and hearing stories about his childhood from Luke, Paige had learned quite a bit about her boyfriend in the last few days.

Paige had enjoyed every moment of the festivities - from Jocelyn's famous german apple pancakes to listening to Jon bore everyone's ears off with his endless talk about eye diseases.

"Retinitis Pigmentosa is a really brutal one," Jon was saying as everyone sat together in the living room. "It's hereditary, causing cell death of the rods, the eventual atrophy of several retinal layers, and finally total blindness. Not super common though." He paused as if trying to remember something. "Not like cataracts and glaucoma. If you had to pick though, it's best to have cataracts since that is super noticeable and easily fixed. Glaucoma is more of a silent vision threat. No symptoms until real irreversible damage is done. In fact, it's quite amazing how many retina problems and diseases can occur without symptoms."

"You picked the right profession," Clary interrupted in that annoyed sibling tone. "Doesn't mean I wanna hear about all the eye diseases I don't have."

"Ah, but the more the know the less likely you are to miss your next regularly scheduled eye exam," Jon replied, grinning.

"Like you'd ever let me miss one," Clary huffed.

"True," Jon laughed. "Oh alright fine. How about an optical party trick instead of facts?"

"You mean like an optical illusion or something?" Clary asked.

"Kinda," Jon said. Then he sat up on the couch dislodging Paige's head from his shoulder. "Okay, so see that big red Santa over there?"

Clary turned to look. "Yeah," she said.

"I'm sure you've experienced this before, but if you stare at it for a while without moving your gaze at all, when you eventually look away at a white wall, you'll see the greeny blue colour in the same shape as the red object you were staring at," Jon explained.

"Okay yeah that kinda sounds right," Clary said, uncertainly. Paige couldn't help but grin. Jon had told her this already quite a few times.

"All the while you were staring at that red object your red cones were firing signals to the brain saying 'red', so when you look away all the red cones are overstimulated and unable to transmit for a few seconds," Jon continued his explanation. "Which means only your blue and green can fire, and since white is a mixture of all the colours, missing a colour changes the image."

"Huh," Clary said thoughtfully. "Okay that is kinda interesting. Definitely cooler than genetic eye diseases."

"More relative at the very least," Luke smiled.

"The effect is called an after image," Jon explained.

"Are you going to make her do the blind spot test too?" Paige asked grinning.

"Do I have a choice?" Clary asked, resigned.

"No," Jon continued. "Close your left eye and then fixate on a point straight in front of you." Paige watched Clary do what her brother said. "Now hold up your right thumb, like this, just a few inches away from where you are looking. What you should see is the top of your thumb disappear completely. If it isn't working move your thumb around slightly until it works."

For a while Clary just looked dubious until suddenly she said. "Wow, my thumb's gone."

"That's your blind spot," Jon said. "When both eyes are open it is hidden by the other eye covering the gap, but even with only one eye open your brain can fill in the missing information as long as new information doesn't enter the blind area like a thumb. At that point it can no longer guess what's there like it can with the background and the object disappears."