The external environment that we see every day is possible due to the ocular motor system involved in controlling the eye musculature. The motor system also holds the action of a few muscles and other neural circuits around the eye. The best example of ocular reflex is the eye blink reflex that protects the cornea from drying or from contact with a foreign particle in the environment.
On the other hand, the pupillary light reflex is primarily involved in determining pupil size with the help of increased light that can cause pupil constriction and reduce the light that enters the retina. Abnormal pupillary reflex is noticed in multiple cases of optic nerve injury, ocular nerve damage, pupillary response in traumatic brain injury, and excessive use of depressant drugs. The article will broadly discuss various topics related to optic atrophy.
Pupillary light reflex:
The pupillary light reflex helps in adjusting the pupil size during changes in light levels. Moreover, it also helps measure pupil size when conducting eye evaluation. Pupillary light reflex plays an integral role in adjusting the amount of light entering the retina, protecting the photoreceptors from bright sunlight.
Iris comprises two sets of muscles that control pupil size. The sphincter muscle fibers make a ring-like structure at the margin of the pupil so that the sphincter contracts and the pupil constricts. On the other hand, dilator muscle fibers are responsible for radiating the pupil diameter measurement. Dilator muscle fiber helps in dilating the pupils by increasing their size. Irrespective of their functions, both the muscles are involved in controlling the amount of light entering the retina and the eye’s depth of field.
- Consensual reflex: When light typically enters one eye, and pupil constriction appears in both eyes.
- Direct response: Size of the pupil changes in the vision directed with light (e.g., if the light is produced in the right eye, proper pupil constriction occurs)
- Consensual response: Size of the pupil changes in the eye opposite to the eye directed with light ( If the light is headed in the left eye, proper pupil constriction occurs).
Optic Nerve Atrophy:
Optic atrophy is a severe eye condition that affects the optic nerves responsible for transmitting impulses from the eye to the brain. The optic nerve is a set of bundles that carry images from your retina to the brain. Once these nerves are damaged, the retina fails to transmit the visual information to the brain, causing vision loss or blurred vision.
Signs and Symptoms:
The optic atrophy sign is prominent and can be noted as optic nerve pallor. As the optic nerve fiber is very thin, the surrounding disc margin appears very sharp, and the disc becomes pale, indicating the absence of small blood vessels. Various symptoms of optic atrophy are listed below.
- Abnormal color vision
- Blurred or milky vision
- Abnormal side vision
- Less brightness in one eye compared to the other eye.
The symptoms mentioned above do not necessarily suggest that you suffer from optical nerve damage; however, it is recommended to fix a consultation with a retina surgeon if you observe any symptoms.
Causes of Optic Nerve Atrophy:
Optic nerve atrophy can be due to different diseases and disorders leading to optic nerve damage. Cases of optic nerve damage increase when the nerve is improperly developed due to various reasons. Glaucoma and inflammation of the optic nerve are yet another reason that can disrupt the functioning of the optic nerve leading to vision loss. Many retina specialists indicate vitamin deficiencies, tumors, and poisons that can cause optic atrophy.
- Optic nerve stroke, also known as anterior ischemic optic neuropathy
- Optic nerve tumor
- Inflammation or optic neuritis due to multiple sclerosis
Clinical diagnosis involving pupillary evaluation:
If your ophthalmologist suspects an optic atrophy condition, they may suggest a pupillary evaluation that can help in determining the visual acuity, color vision, side vision, and pupil reaction. An ophthalmoscope is used to examine these parameters; further MRI of the orbits and brain may also be conducted upon necessity.
It is not difficult to diagnose optic atrophy condition, but it is difficult to determine the prime cause of the damage. Usually, an ophthalmologist often gets confused about the visual impairment caused due to optic neuropathy and retina disease. That is why they prescribe the technicians to measure pupil size as a standard preoperative procedure to fast-forward the diagnosis.
Doctors, ophthalmologists, and other medical specialists suggest the below-mentioned workups for individuals presenting optic atrophy conditions. Before conducting a further diagnosis, a general pupil diameter measurement is done, which is an essential part of the preoperative evaluation.
- Diagnosis of afferent pupil
- MRI or brain and orbit with contrast
- Visual fields 30-2, color vision
- CT with contrast (To evaluate bone growth and sinusitis)
- Cardiovascular health evaluation and blood pressure check
Often optic atrophy is confused with optic nerve hypoplasia, myelinated nerve fibers, myopia, or titled disc. Therefore a differential diagnosis is conducted to determine the cause of optic atrophy.
- Vascular: Diabetes, arteritic, and non-arteritic ischemic optic neuropathy
- Inflammatory: Sarcoid and systemic lupus
- Toxic and nutritional: Various medications such as methanol, vitamin deficiency, amiodarone, and ethambutol lead to nutritional toxicity.
- Neoplastic condition: Lymphoma, leukemia, and tumor
- Genetics: Leber’s hereditary optic nerve atrophy and Autosomal dominant optic atrophy
- Traumatic optic neuropathy
- Radiation optic neuropathy
Treatment for optic nerve atrophy:
Although there is diagnosis and treatment for optic nerve atrophy, a cure or reversal of damage is not yet possible according to the current medical science and technologies.
Pupillary size measurement and other diagnoses such as Optical Coherence Tomography (OCT) and Visual Field Testing can confirm if a person is suffering from optic nerve atrophy or not. Unfortunately, there are no medications to reverse the optic nerve damage.
However, doctors and eye specialists can help manage further optic nerve damage by controlling the fluid pressure around the brain and spinal cord. In the majority of the cases, optical nerve damage is unilateral; hence protecting the good eye is essential. The use of magnifiers and tinted lenses can be beneficial in protecting the eye from any damage.
The optic nerve atrophy condition is non-reversible. It is advisable to get an ophthalmologist’s suggestion if you experience blurred or abnormal side vision. Early diagnosis can help save the image by reserving healthy axons and ganglions. Once the optic nerve is entirely damaged, it can lead to significant vision loss.