Yüksek Kortikal Görme Fonksiyon Bozuklukları
Özet
Yüksek kortikal görme fonksiyon bozuklukları, görece normal görme keskinliğine rağmen görsel işleme veya dikkat anomalileriyle karakterize durumlardır. Görsel bilgi retinadan primer görme merkezi V1'e ulaştıktan sonra iki ana yüksek görme yolunu izler: nesne tanıma ile ilgilenen ventral yol (renk ve "ne" analizi) ve uzaysal yönelimle ilgilenen dorsal yol ("nerede" analizi). Farklı beyin bölgelerindeki hasarlar, çeşitli klinik tablolarla kendini gösterir. Oksipital lob hasarında şekil algısı varken okuma yitimini ifade eden agrafisiz aleksi görülürken; oksipito-temporal hasarlarda yarı alan renk körlüğü (serebral hemiakromatopsi), nesneleri tanıyamama (görsel agnozi), yüz körlüğü (prosopagnozi), adlandıramama (optik afazi) ve hareket algısının bozulması (akinetopsi) gibi bozukluklar izlenir. Sağ paryetal lob hasarında ise hastanın bir yarı görme alanındaki objelere ilgisiz kaldığı görsel yarı aldırmazlık meydana gelir. Çift taraflı simetrik paryeto-oksipital hasarlarda simultanognosi, oküler apraksi ve optik ataksiden oluşan Balint sendromu gelişebilir. Bu bozukluklar genellikle posterior veya orta serebral arter tıkanıklıkları, karbon monoksit zehirlenmesi, tümörler ve Alzheimer, Creutzfeldt-Jakob veya Lewy cisimcikli demans gibi nörodejeneratif hastalıklar nedeniyle ortaya çıkar. Semptomların karmaşıklığı ve hekimlerin farkındalık azlığı nedeniyle tanıların gözden kaçabildiği bu durumlarda nöroloji ve oftalmoloji uyumu kritik önem taşır.
Higher cortical visual dysfunctions are conditions characterized by abnormalities in visual processing or attention, despite relatively normal visual acuity. Once visual information from the retina reaches the primary visual center V1, it follows two main higher visual pathways: the ventral pathway, which is involved in object recognition (color and "what" analysis), and the dorsal pathway, which deals with spatial orientation ("where" analysis). Damage in different brain regions manifests with various clinical pictures. While occipital lobe damage leads to alexia without agraphia, which is the loss of reading ability despite preserved shape perception, occipito-temporal damage causes disorders such as hemifield color blindness (cerebral hemiachromatopsia), inability to recognize objects (visual agnosia), face blindness (prosopagnosia), inability to name objects (optic aphasia), and impaired motion perception (akinetopsi). Right parietal lobe damage results in visual hemineglect, where the patient ignores objects in one visual field. Bilateral symmetrical parieto-occipital damage can cause Balint's syndrome, consisting of simultanagnosia, ocular apraxia, and optic ataxia. These disorders usually arise due to posterior or middle cerebral artery occlusions, carbon monoxide poisoning, tumors, and neurodegenerative diseases such as Alzheimer's, Creutzfeldt-Jakob, or Lewy body dementia. Collaboration between neurology and ophthalmology is critical in these conditions, where diagnoses can be overlooked due to the complexity of symptoms and lack of awareness among physicians.
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