What does poor vision at dusk mean?
The retina contains two types of light-sensitive cells. Cones work in bright light and are responsible for color and detail, rods for twilight vision and lateral field. When moving from a lighted place to a dark place, the rods need time to adjust: normally the eye adapts in a few minutes. If this process is disrupted, a person does not see anything in the dark for a long time, and when returning to the light he experiences severe discomfort. Some complaints include glare from the headlights of oncoming cars and halos around the headlights.
- Rods are responsible for vision at dusk
- Adaptation to darkness normally takes minutes
- Slow adaptation is the main symptom
- Dazzle from oncoming headlights
- Halos and glare around light sources
Possible reasons
The classic cause, known from school, is vitamin A deficiency; Nowadays, it occurs with a poor, monotonous diet, chronic intestinal diseases with malabsorption, severe liver diseases and after gastric surgery. But in most patients the matter is different: hereditary retinal dystrophies, primarily retinitis pigmentosa, advanced glaucoma, cataracts, high myopia, diabetic retinal damage. Sometimes poor vision in the dark appears after laser vision correction and is due to the size of the pupil in the dark.
- Vitamin A deficiency and malabsorption
- Retinitis pigmentosa and other retinal dystrophies
- Glaucoma with narrowing of the visual field
- Cataract
- High myopia
- Diabetic retinopathy
- Features of the pupil after keratorefractive surgery
Associated symptoms
Additional complaints help to understand the direction of the search. A narrowing of the visual field and difficulty avoiding obstacles indicate damage to the periphery of the retina or glaucoma. Dry eyes, whitish spots on the conjunctiva and rough skin accompany vitamin A deficiency. Gradual blurring of vision and increased glare in the dark are characteristic of cataracts. If parents or siblings have had similar complaints since childhood, hereditary retinal dystrophy is likely. Sudden flashes and floaters require urgent examination.
- Narrowing field of view
- Dry eyes and skin due to vitamin A deficiency
- Glare and fog with cataracts
- Family history of dystrophies
- Increased intraocular pressure
- Chronic bowel and liver diseases
What examinations are needed
The ophthalmologist checks visual acuity, measures intraocular pressure and examines the fundus in detail with a dilated pupil: this is where characteristic changes in retinitis pigmentosa and diabetes are visible. Computer perimetry shows whether the field of view is narrowed and in what location. Electroretinography is used to assess the functioning of rods and cones, and the structure of the retinal layers is studied using optical coherence tomography. If vitamin A deficiency is suspected, nutrition, intestinal and liver condition are assessed, and genetic testing is discussed in case of hereditary diseases.
- Fundus examination with pupil dilation
- Measuring intraocular pressure
- Computer perimetry
- Electroretinography
- OCT retina
- Nutrition and bowel function examination
- Genetic consultation for familial cases
What to do and how to treat it
Treatment depends entirely on the cause, so you shouldn’t start with buying vitamins. If there is a confirmed deficiency of vitamin A, it is replenished under the supervision of a doctor: an excess of this vitamin is toxic, and high doses are contraindicated for pregnant women. It is enough to include liver, eggs, dairy products, carrots, pumpkin, greens and apricots in your diet. For glaucoma, intraocular pressure is reduced, for cataracts surgery is discussed, and for diabetes, sugar control is achieved. For hereditary dystrophies, there is no specific treatment yet, so observation, protection from bright sun and safety measures in the dark come to the fore.
- Determine the cause before taking any medications
- Replenish vitamin A only as prescribed by a doctor
- Foods with vitamin A and carotenoids in the diet
- Treatment of glaucoma, cataracts, diabetes
- Be careful when driving at night
- Good lighting at home and night lights in the hallway
- Regular observation by an ophthalmologist
