Author Question: Phil is a 54-year-old with type 2 diabetes. After he was initially diagnosed with the condition, his ... (Read 77 times)

Bob-Dole · **on:** Jun 25, 2018

Phil is a 54-year-old with type 2 diabetes. After he was initially diagnosed with the condition, his physician referred him to an ophthalmologist for a comprehensive eye examination. Phil had been struggling with the lifestyle changes he was required to m

He was able to return to a healthy weight with physical exercise and dietary changes, but he worked long hours and ate poorly when on business trips. Phil missed his second annual checkup with his ophthalmologist because of such a trip. When he finally made it in, she examined him and stated there was now evidence of small retinal hemorrhages and cotton-wool exudates. She emphasized his need to reduce his hypertension and hyperlipidemia and wrote up a report for his physician.

How do visual disturbances arise from background and proliferative retinopathy?

How might blindness occur with a prolonged detached retina? Explain using your knowledge of pathophysiology.

What are the similarities and differences between traction retinal detachment and rhegmatogenous detachment?

Question 2

Allan is 48 years old and works as a business executive. One day after returning from a lunch meeting, Allan felt as though his office was spinning around him.

His left ear had a feeling of fullness, and he heard ringing in it. He was so dizzy that he reclined in his office chair and closed his eyes, not wanting to move his head for fear the spinning would start again. The following evening, a similar event happened at home. His wife was concerned about the vertigo he was experiencing and how irritated he was by the tinnitus. When the same event happened 1 month later, Allan said his hearing was affected when the attack was at its worst. His wife insisted it was time he took some time off work to see his family physician.

What inner ear disorder produces the triad of vertigo, tinnitus, and hearing loss? What is the pathophysiology of this condition?

What are the sensory functions of the semicircular canals and the utricle and saccule?

Allan's symptoms included a feeling of fullness in his ear accompanied by hearing loss. How does endolymph contribute to the function of hearing? What is the role of the endolymphatic potential?

verrinzo · **Reply #1 on:** Jun 25, 2018

Answer to Question 1

Background retinopathy affects the capillary endothelium and results in a breakdown of the blood-retinal barrier. As plasma leaks from the compromised capillaries, macular edema and subsequent loss of vision result. In proliferative retinopathy, neovascularization is responsible for visual change. These new vessels tend to bleed into the vitreous cavity and decrease visual acuity. Because of their mode of attachment, these new vessels also have the tendency to adhere the vitreous to the surface of the retina. As the vitreous moves, it exerts mechanical forces on the retina, leading to retinal detachment and progressive loss of vision.

The neural retina receives nutrients from the choroid. When the neural retina is detached from the pigment layer, the transport of nutrients is severed. With prolonged detachment, the receptors of the neural retina become ischemic, die, and cause loss of vision in that portion of the retina.

Traction retinal detachment is a result of mechanical forces that pry the retina away from the choroid. The traction forces are frequently from the lay down of fibrotic tissue that have developed secondary to injury, infection, or inflammation. In rhegmatogenous detachment, a retinal tear is present. The detachment occurs when the liquid vitreous enters the tear and separates the neural retina from the pigment layer.

Answer to Question 2

Allan is experiencing the symptoms of Mnire disease. The disease is thought to result from the impaired filtration and excretion of the endolymphatic sac. The condition may be exacerbated by an abnormal increase in endolymph production. This excessive production may occur on its own, or as a compensatory mechanism for an abnormal decrease in perilymph.

The sensory cells of the utricle and saccule respond to static head position in relation to gravitational pull. They also provide sensory input for changes in linear motion and changes in head position.
The semicircular canals are positioned to detect rotational movements of the head. They sense head tilting with acceleration and detect turning movements in concert with locomotion.

Endolymph is a potassium-rich fluid contained in the scala media of the cochlea. It receives sound waves as they pass through the perilymph of the scala vestibuli and translate across the vestibular membrane. When the endolymph is set in motion, the basilar membrane vibrates and the receptor cells in spiral organ of Corti are stimulated so that the perception of sound occurs.
The endolymphatic potential exists because of an electrolyte gradient in the cochlear apparatus, maintained by Na+/K+ active transport pumps. The resting membrane potential between endolymph and perilymph acts to sensitize the hair cells of the spiral organ of Corti, allowing them to perceive the quietest of sounds.