When Joey and Chandler are driving over the bridge, the interior shots show the Queensboro Bridge, yet when Joey kicks out Chandler, the exterior shot is off the Brooklyn Bridge. Still yet, when Chandler comes back he tells everyone that Joey kicked him off on the George Washington Bridge.
Rachel tries to avoid going to the eye doctor by knocking over a box of cereal. The box ends up a few feet from the counter with the cereal spreading out. In the following shot showing the floor the box is almost touching the counter and the spilled cereal is in a more concentrated pile.
Rachel is terrified of anything touching her or anyone else's eyes, and hates when people makes jokes having to do with eyes. In a previous season, Monica has to go see the eye doctor because she got ice in her eye. Monica asks, "How cute is the new eye doctor?" And Rachel responds, "So cute I'm thinking about jamming this pen in my eye."
The same insert (outside the front door of the coffeehouse) with the mailman and tall blonde guy are used twice in a row. Once before Joey and Chandler leave and before Chandler comes in from being kicked out of the cab.
When Phoebe mentions the cab of her grandmother for the road trip to Last Vegas, the apple she's holding has a bite taken out of it. In the next scene, the apple does not have a bite taken out.
The instrument where Rachel sets her head on at the optometrist's office is called a slit lamp. The doctor tells Rachel she will feel a tiny puff of air in her eye. The slit lamp can only check the eye in a magnified lens, similar to the handheld ophthalmoscope that the doctor uses later on. An autorefractor (not featured in the episode), where the patient also sets their head on in a similar position, can do the air puff feature.
In the Coffee shop, after Joey over-excitedly pokes himself in his eye before the opening credits Chandler ask him "are you alright there Matt?" He uses the Actor's name not the character's name.
When the gang catches Rachel so Monica can drop the medicine into her eye, you can clearly see she drops it onto her lid, not into the actual eye.
When Joey and Chandler are driving the cab to Las Vegas, all interior shots show them on the Queensboro Bridge, but the exterior shot after Chandler is kicked out shows them on the Brooklyn Bridge, both of which are East River crossings that would be taking them east from Manhattan to Brooklyn, and not West towards Las Vegas.
When Chandler arrives back at the coffee house, he says Joey kicked him out on the George Washington Bridge, which would have taken them the right direction, west across the Hudson River. In actuality, the Holland Tunnel is the closest Hudson River crossing to Greenwich Village.
When Joey arrives in the desert of Las Vegas, we see a few saguaro cacti; however, these are only native in the Sonoran Desert, not the Mojave Desert, which is where Las Vegas is located.
Rachel demonstrates an extreme phobia of having anything coming even close to her eye. It begs the question of how she applies eyeshadow and mascara, let alone how she calmly let Ross apply it for her in Season 3 when she had a broken rib.
When Rachel and Monica are leaving the apartment for eye doctor appointment, Rachel is walking to the left side while the stairs are on the right side.