OPTIC NERVE DISORDERS AND OPTIC TRACT DISORDERS
Definition
The loss of visual function can be linked to both ocular pathologies and pathologies that can involve those portions of the brain (Optic Nerve, Optic Chiasm, Optic Tract, Lateral Geniculate Nucleus, Optical Radiation, Occipital Cerebral Cortex) responsible for the transmission and decoding of visual information.
Symptomatology
In addition to ocular pathologies, the optic nerve pathologies, caused by Diabetes, Glaucoma, demyelinating diseases (Multiple Sclerosis), ischemic phenomena, toxic or iatrogenic processes, infectious processes, autoimmune pathologies, hypothyroidism and hyperthyroidism, neurodegenerative pathologies, neoplastic processes, traumas, are of particular interest. Moreover, many optic nerve disorders are related to genetic mutations, such as Leber Neuropathy or Dominant or Recessive Hereditary Optic Neuropathy. Pathologies of the optic nerve occur with a progressive or acute loss of visual acuity, with deficit of the visual field, with modifications of chromatic perception or contrasts. Other diseases of the Central Nervous System such as Migraine (with or without visual aura), TIA, Stroke, Cerebral Infarctions, neoplastic diseases, head trauma, can induce deficits in visual perception or specific losses of part of the visual field. In addition, various pathologies that recognize an inflammatory, vascular, neoplastic or toxic, metabolic etiology, can induce other dysfunctions of the visual system not necessarily associated with changes in visual perception.
Diagnostics
An accurate anamnestic connection is essential, an assessment of visual acuity even after cycloplegia, examinations of ocular motility, perimeter examinations or metric fields, electrofunctional examinations (ERG, PERG, F-ERG, mfERG, PEV), retinal and optic nerve morphological evaluations through OCT examinations, a targeted neuroradiological diagnostic. For a correct diagnosis of functional damage it is essential to associate PEV and various types of ERG. In particular, to obtain specific information on post-retinal nerve conduction, the simultaneous recording of PEV and PERG is particularly useful, where the difference between the P100 latency time of PEV (expression of occipital response) and the P50 latency time of PERG (expression of maximum ganglion cell activity) is referred to as "Retinocortical time".
Therapy
The early diagnosis of pathologies of the optic nerve and visual pathways allows to diagnose systemic pathologies unknown by the patient that mainly affect the cardiovascular, rheumatological, endocrinological and neurological system, which must be treated with specialized therapy.
