Nyctalopia - Causes, Risk Factors, Diagnosis, and Treatment

Introduction

Nyctalopia is also called night blindness. This condition makes it difficult or impossible to see in relatively low light. It is often associated with an inability to adapt quickly from a well-illuminated (bright light) to a poorly illuminated (dark light) environment. It is not a definite disease but rather a symptom of an underlying or previous eye problem, usually a retina problem. It can also be described as an insufficient adaptation to darkness. In the term nyctalopia, there is confusion for so many people with the term hemeralopia. The inability to see in bright light is termed hemeralopia, while nyctalopia is an inability to see in dark light.

What Are the Causes Associated With Nyctalopia?

Night blindness may be from childbirth or can occur because of injury or malnutrition. In addition, patients with genetic (runs in the family) conditions have progressive nyctalopia, and their daytime vision may also be affected.

Nyctalopia which is present since birth is stationary. From birth, the rods either do not work or work very little, but the condition does not get worse.

Several other conditions or factors can be the reason for nyctalopia, including

• Myopia (nearsightedness).

• Glaucoma is a disease in which the optic nerve affects the human eye and brain.

• Glaucoma medications – Some medications can cause the pupils to narrow.

• Cataracts – In this condition, clouding of the lens occurs.

• Retinitis pigmentosa – In this eye disease, the breakdown and loss of retinal cells can cause blindness.

• Keratoconus – In this condition, corneas are curved.

• Vitamin A deficiency.

• Retinal detachment.

• Congenital night blindness in Oguchi disease.

• Sorsby's fundus dystrophy, in which degeneration of the macula of the eye occurs.

• Usher syndrome - A genetic condition that affects both hearing and vision. Retinitis pigmentosa (pigmentation in the retina) is the major vision-related symptom.

What Are the Risk Factors for Nyctalopia?

Certain factors significantly increase the chances of night blindness and include:

1. Poor Nutrition: In malnutrition, patients have fewer vitamins, so a deficiency, mainly vitamin A can cause night blindness.

2. Diabetes: In diabetes, the glucose level in the blood rises, which causes problems in patients such as vision problems. Complications include diabetic retinopathy (affects eyes) and night blindness (inability to see well at night).

3. Pancreatic Ailments: For example, in cystic fibrosis, fat absorption by cells is disturbed, and there is an increased risk of vitamin A deficiency. Vitamin A is fat-soluble, and deficiency can lead to night blindness.

What Is the Pathophysiology of Nyctalopia?

Rods are used for dark vision at night, and cones are used for bright vision during the day. They are both located in the back region of the eye, the retina's outermost region. These rods and cones are made from different segments; the outer one comprises discs containing photoreceptors that help absorb light. Rhodopsin is formed in the eye rods by converting vitamin A in the visual cycle to 11-cis-retinal, which combines with scotopsin. When vitamin A is deficient, adequate amounts of rhodopsin cannot be produced, so the ability to see in low light decreases.

How Is Nyctalopia Diagnosed?

The patient's entire medical history is necessary for an ophthalmologist or eye doctor to determine if any severe eye injuries have happened in the past or not to know the underlying reason. An eye examination is also conducted, which helps in studying various aspects of vision. It includes reading small or printed text, side vision, structures related to the optic nerve, eye pressure, and pupil dilation. Blood samples of the patient are also required to determine the levels of vitamin A and glucose in the blood. To determine what is causing night blindness, an ophthalmologist will perform a thorough eye exam and may order any of several specialized images, tests, or exams.

The following problems can prompt a visit to the doctor to discuss nyctalopia:

• Difficulty moving into the house at night time.

• Issues driving at night time.

• Difficulty recognizing faces in dark places.

• Difficulty in adjustments or adaptation from light to darkness.

Complete patient history is a must; an eye examination will help discover any underlying conditions causing nyctalopia.

What Is the Clinical Presentation of Nyctalopia?

The most promising symptom for patients of nyctalopia is the complex vision at night time.

Other signs or indications of night blindness depend on the exact cause and comprise:

• Patients may have pain in the eyes.

• Some others can have persistent headaches.

• Some may experience nausea and also vomiting.

• Blurred and hazy vision can occur in some.

• Eyes become more sensitive to bright light.

• Delays or difficulty in adjustments from light to darkness.

• Distant vision can be a problem for patients.

What Is the Treatment for Nyctalopia?

Treatment mainly depends on the cause of nyctalopia

• If myopia is the reason for night blindness or nyctalopia, then glasses or contact lenses for myopia will help correct the eye defect.

• Cataract problems can be corrected by surgery to resolve the clouding of the eye lens which will enable clear vision in the eye.

• Glaucoma is treated mainly by eye drops, laser procedures, surgery, or medications, depending on severity. Still, it will not correct all problems of nyctalopia but will reduce eye pressure so vision can be improved.

• Vitamin A supplements should be given in adequate doses if deficiency of vitamin A is the reason.

• Genetic problems, such as retinitis pigmentosa and Usher syndrome, cannot be cured or completely treated. Such individuals are advised not to drive at night and avoid dark places.

How to Prevent Nyctalopia?

1. Lifestyle Modification - Genetic problems cannot be completely treated, but controlling

lifestyle can improve conditions. Try the following to prevent night blindness possibly:

Eat Vitamin A foods. Some suggestions include -

• Carrots.

• Cantaloupes.

• Butternut squash.

• Green vegetables.

• Spinach.

• Dairy products such as eggs or milk.

2. Get a Regular Eye examination With an Ophthalmologist - Visit an eye specialist regularly so problems in the eye are diagnosed early if having problems with the eyes.

3. Use Sunglasses - Protect the eyes from the sun through sunglasses. UV rays increase the risk of damage to the eyes and can cause cataracts, macular degeneration, and glaucoma.

4. Routine Exercise - Regular exercise may reduce the risk of eye conditions. It lowers eye pressure, increases blood circulation, and improves blood glucose levels.

Conclusion

Night blindness or nyctalopia is not an eye problem by itself. Still, it is a symptom rather than a disease of an underlying vision problem like myopia, cataracts, glaucoma, and other defects of the retina. It can arise from vitamin A deficiency or can be because of genetic causes, and it does not cause permanent blindness. It can also be corrected by correctly identifying and treating the underlying cause properly. Regular visits to the eye doctor, diet modification, and exercise can improve the condition.