Have you ever wondered how it is that you’re able to see in near-darkness, and how your eyes can adapt to being in a dark room? Sure, it might take up to half an hour for your eyes to fully adjust when you come inside after having been exposed to bright sunlight outdoors. But if you
have healthy eyes, they adapt reliably. It’s truly amazing.
How Healthy Eyes Adapt to the Darkness
Your marvellous irises do more than just show off your eye colour and look pretty. They actually contain muscles that work to manipulate your pupils. Together, the irises and pupils act like gatekeepers as light falls on your eyes. The pupils’ job is to let in just the right amount of light – not too little, and not too much. Aided by the irises, the pupils widen in a dim environment to let more light in. They grow smaller in bright light when less light is needed to enable your vision.
After the light enters the eye, it proceeds through the lens to the retina. In conjunction with the retina, a couple of different types of photoreceptors make light or dark adaptation possible. In bright light, photoreceptors known as “cones” sense and adapt to changes in daylight or similar levels of illumination. In dimmer light, photoreceptors called “rods” take over the performance of this task.
Cones and rods work together to help you see, as long as some level of light is available for your eyes to work with. You cannot see in total darkness, but your rods are so light sensitive that they make it possible to see even in extremely dim light.
Rods exhibit far more light sensitivity than cones do. However, cones are far faster at adapting and regenerating than rods are. Rods contain a substance known as “rhodopsin” that can be regenerated in low-light conditions. In bright light, the rhodopsin is not so easily regenerated. In that case, the highly adaptable cones take over to perform the necessary light adaptation function.
Aging Eyes Might Adapt to Darkness More Slowly
The above description is what happens when the eyes are healthy, but all of this can fall apart when eye health deteriorates. As you age, it is possible that the muscles in your iris might weaken, as muscles are prone to doing. As the eyes become less responsive to light, it can result in your eyes not properly adapting to swift changes between light and darkness.
As you age, you’re also likely to maintain most of your cones, but lose significant numbers of your rods – perhaps up to one-third of them. One common result of these changes: It often takes much longer for an older person’s eyes to adapt to the darkness than it takes for a young
At the age of forty, you may notice that your vision is changing for the worse. After your sixty- fifth birthday has come and gone, your eyes will take noticeably longer to adjust to dramatic changes between light and darkness. You will also need significantly greater amounts of illumination to enable you to see well.
Precautions You Can Take to Help Preserve Eyesight After 40:
If you’re over the age of 40, we recommend taking some extra precautions to help preserve your eyesight:
- Keep your glasses and the windshield of your car sparkling clean.
- Wear a wide-brimmed hat and high-quality sunglasses when you spend time outdoors in bright sunlight.
- Ensure that you eat a nutritious diet. In particular, eat foods that are high in zinc, such as garbanzo beans and cashews. Zinc deficiency and vitamin A deficiency are both correlated with poor darkness adaptation. Researchers have determined that zinc supplementation is helpful in correcting this problem. Women need 8 mg of zinc per day; men need 14 mg per day.
- It’s also crucial to eat foods such as fresh, raw carrots that are high in vitamin A. Under ordinary circumstances, women need at least 700 µg of vitamin A per day, and men need at least 900 µg per day.
- Consider enrolling in an extras cover health insurance plan that includes optical cover.
- Get your eyes checked at least once per year. If you’re younger than 65, Medicare will cover a regular eye examination from an optometrist once every three years. Otherwise, if you’re not able to cover the costs out of pocket or through private health cover, you can ask if your GP might be able to perform your eye exams. Once you’re over the age of 65, Medicare will cover your annual eye examinations.
- If any obvious changes in your vision occur, speak with your GP about it immediately. Preventative care is essential for ensuring that vision problems do not worsen unnecessarily.
- Always give your eyes sufficient time to adjust between light and dark environments, especially before climbing stairs or performing any other activity that poses a risk of falling and injury.
We hope this information is helpful to you in understanding how your eyes should properly adapt to the darkness. If you notice that your eyes are not adapting as they should, please do speak with your GP as soon as possible — or get in touch with us to book a consultation.