Avoid watching TV in the dark; you'll be able to enjoy your favourite holiday movie for longer. When the room is dark, your pupils enlarge, making it easier for light to enter your eyes and cause glare, which can hurt your eyes and cause eye strain.

To control how much light enters the eye, the human pupil, a variable aperture, is present.

The iris is a group of muscles that regulates the pupil's size. Bright light causes the iris to constrict, which shrinks the pupil.

The iris entirely relaxes in darkness or low light to allow the largest amount of light to pass through the enlarged pupil and into the eye. When watching TV in low light or darkness, the TV is the only source of light reaching the eye.

The iris is forced to constantly relax and contract, putting pressure on it, as different images and pictures are presented on TV in a constant range of brightness levels.

Since the TV is not a significant source of light and the impact of its brightness fluctuation is minimal, this effect is not noticed when watching TV in light.
 

While it is advised not to watch television in the dark due to the continual relaxation and contraction of the iris, this does not hold true when viewing a film in a dark cinema.

The main justification is that cinema images are not made up of pixels like those on television or computers. The format of a movie is analogue.

See how stressful it is to read a lengthy text on a computer compared to reading the same item from a print out is an easy approach to test for the stress caused to the eye.
 

When we read a book, the letters are all-black, and the white space in between them. On a computer, a letter's centre is the darkest, while its colour fades and disappears towards the periphery. As a result, the focusing mechanism experiences a lot of strain.

Once more, watching a movie reduces eye strain since the screen entirely fills the viewer's field of vision.

With a TV or computer, this is not the case. The screen is smaller and does not completely fill the eyes' field of vision.

Additionally, the thing on the TV is continually flashing, and we can make out zones with various light levels. As a result, it is highly recommended that watching TV or working on a computer be done in a well lit room.