Night blindness, also called nyctalopia (nik-tl-oh-pee-uh), is the inability to see well at night or in poor light. It was first described over 2000 years ago. Nyctalopia is not a disease, but rather a symptom of many different conditions, some treatable, some not. Historically, it was known as “moonblink” and believed to be a temporary condition caused by sleeping in the moonlight of the tropics.
Nyctalopia is due to a disorder or disease of cells in the retina called rods. Rods are responsible for our ability to see in dim illumination. By contrast, cones of the retina are responsible for our ability to see detail and color vision in lighted conditions. Rods contain a pigment called rhodopsin that allows us to see at night. The body synthesizes rhodopsin from vitamin A which is why we are told to eat carrots. The eyes continually produce rhodopsin, but in the daytime it is continually bleached out by light. This is why when you walk from the hallway of a movie theater into the movie, sometimes you have to stop to allow your eyes to adjust to the dark. You can think of this as changing from using cones to rods or, the time it takes to regenerate enough rhodopsin to see in the dark. Maximum dark adaptation can take up to 48 hours. Another common example is when you go to sleep at night the room seems very dark however, when you wake up in the middle of the night it seems less dark or even brighter!
Nyctalopia can vary on a scale from very mild to so debilitating that driving at night or going outside in the dark is not possible. Disorders or diseases that cause nyctalopia include: nearsightedness, glaucoma, diabetes, retinitis pigmentosa, vitamin A deficiency, cataracts, various medications, some refractive surgeries and laser treatment for diabetic retinopathy.
Contrast sensitivity describes the ability of the visual system to distinguish bright and dim components of an image. Nearsightedness, cataracts, various medications and some refractive surgery cases cause nyctalopia through the reduction of contrast sensitivity.
Glaucoma, diabetes, and retinitis pigmentosa result in damaged or diseased rods in the retina resulting in nyctalopia. Laser treatment of the retina for diabetic retinopathy results in damage to the peripheral retina where most rods are concentrated and therefore significantly reduces night vision.
Nyctalopia can be treated by improving contrast sensitivity through quality optical products including digitally surfaced and non-glare lenses. Various tinted lenses may also help. Maintaining control of diabetic retinopathy, glaucoma and having cataracts removed when necessary, can prevent or delay potential night blindness. Diet is also very important not only to control blood sugar, but to avoid vitamin deficiencies particularly vitamin A.
Finally, get an eye health evaluation to rule out all of the above listed causes of nyctalopia. Preventative eye care can be very helpful in avoiding this condition. Please contact our offices in Stillwater at 405-372-1715 for your eye health evaluation. We also invite you to visit our website at www.cockrelleyecare.com and like us on Facebook at Cockrell Eye Care Center!