VISUAL PATHOLOGY Lesions located at different sites along the visual pathways will result in different types of vision loss. This section will test your grasp of the fundamentals of the visual system as it provides you with examples of some of the more common visual defects. Some of these lesions you may not have been exposed to. Don't be disturbed, this is for your learning experience. 1. A complete section of the optic nerve will result in total blindness of that eye loss of temporal visual field of that eye loss of temporal visual fields of both eyes paralysis of that eye Correct No. Total blindness of that eye will result. The optic nerve is made up of the axons of all the ganglion cells of the retina of one eye, which travel together until the nasal fibers cross in the optic chiasm. Section of an optic nerve results in loss of all vision of that eye. 2. A patient has an enlarging pituitary tumor that is pushing on the center of the optic chiasm. This will result in loss of all vision in both eyes nasal visual field in both eyes temporal visual field in both eyes upper visual field in both eyes Very good. No. The answer is C. The center of the optic chiasm is made up of crossing fibers from the nasal retinae. Their destruction would cause blindness in the temporal visual fields of both eyes. This is known as bitemporal hemianopsia (blindness in half the visual field; Here the temporal half of each visual field). Remember to always check to see if the question is using visual fields or retinal fields. 3. A brain tumor compresses the right optic tract. This will disturb vision in the right eye the left eye the nasal field in right eye and the temporal field in the left eye the temporal field in the right eye and the nasal field in the left eye Brilliant No. The answer is C. The optic tract connects the optic chiasm with the lateral geniculate body, and contains fibers from the temporal retina on that side along with those from the nasal retina on the opposite side. The correct answer is C (Don't forget that visual fields are opposite to their retinal sections). This is known as homonymous hemianopsia (blindness in the same half visual field of each eye), and can be caused by a lesion anywhere behind the optic chiasm. 4. A blow to the head damages the left cuneus. This person has loss of vision in which visual fields left lower temporal and right lower nasal fields left upper temporal and right lower nasal fields left lower nasal and right lower temporal fields left upper temporal and right upper nasal fields Again you have made a good diagnosis! No. The answer is C. The cuneus is the superior portion of the calarine cortex, and receives fibers from the upper temporal retina of that side and from the upper nasal retina on the opposite side. The left cuneus,therefore,controls vision in the lower nasal visual of the left eye and the lower temporal field of the right eye. 5. During physical examination you discover that the patient has right homonymous hemianopsia. A light shined in her right eye produces both direct and consensual light reflexes, but when the light is shined in her left eye, both reflexes are absent. Where might her lesion be? left optic nerve optic chiasm left optic tract right optic radiations Very good. No. The answer is C. 6. The pupils of a 52 year old male are small, unequal and do not react to light but constrict when he focuses on a near object. What disease does he have brain tumor near the chiasm myasthenia gravis hypothyroidism tuberculosis syphilis Good guess or you know your medical trivia. Good try this was a tough one. The answer is E. This man has tertiary syphilis, and his pupils are known as Argyll Robertson pupils. The accommodation reflex is preserved but the light reflexes are absent; the exact location of the lesion is unknown. 7. Horner's syndrome results from interruption of sympathetic fibers supplying the head. Symptoms of the involved side include ptosis (drooping eyelid), lack of sweating on the involved side of the face, and which of the following eye changes? mydriasis miosis homonymous hemianopsia bitemporal hemianopsia only contralateral pupillary dilation Great! Remember that sympathetics control pupillary dilation. So their loss gives miosis. No. The answer is B. Sympathetics control pupillary dilation, so their loss gives miosis. 8. A patient complains of blurred vision. You note that his pupils are unequal, and one pupil reacts to light and dark much more slowly than the other. What is the clinical name for this condition? Argyll Robertson pupil Grave's pupil Adie's pupil lazy pupil Nelson's pupil Good job ( or a good guess). This is called Adie's pupil and the cause is unknown. No. This one was tough. This condition is called Adie's pupil and the cause is unknown