- Explain the pathophysiology of these conditions. What are possible interventions/outcomes for these conditions?
Cataracts: Opacification of the crystalline lens of the eye results in cataract formation. Most cataracts are age-related. As the cataract is forming, it tends to imbibe fluid that swells the lens, which can obstruct the flow of aqueous humor to increase intraocular pressure-glaucoma. As opacification progresses, there is increasing loss of vision, starting from the center of visual fields and progressing outward.
The cataract can be removed. After removal, contact lenses (for those who can manage them-something difficult for an older person) or glasses with very thick lenses can compensate for loss of crystalline lens function. A more expensive option is prosthetic lens implant, which requires no bother.
Glaucoma: Increased intra-ocular pressure is known as glaucoma. It can be due to increased production of aqueous humor (not common), or due to obstruction to flow and resorbtion. In some older persons, there is increased resistance to ouflow of aqueous into Schlemm's canal, so-called primary "open angle" glaucoma, which is painless and insidious. This type of glaucoma is more frequent with diabetes mellitus and with myopia. In some older persons with hyperopia, the iris is displaced forward to narrow the angle at the anterior chamber, obstructing flow, so-called primary "closed angle" glaucoma, which presents with acute pain. In either case the increased pressure presses on the optic nerve, causing excavation to produce progressive visual loss.
Macular degeneration: Age-related macular degeneration (ARMD) is the most common cause of decreased vision in older persons. The macula is the area of greatest visual acuity and represent the center of the visual field. With aging, the macula degenerates, called age-related macular degeneration. The initial result is decreased visual acuity, and possible blindness with progression. Sometimes there is hemorrhage into the macula (hemorrhagic macular degeneration).
Atrophic maculopathy, one of the forms of ARMD, is associated with only mild to moderate visual loss but is not treatable. On the other hand, exudative maculopathy is characterized by the formation of neovascular membranes and causes acute visual disturbances; however, it is potentially treatable by means of laser photocoagulation.
Diabetic retinopathy: There is a more benign "background" retinopathy with small hemorrhages, microaneurysms, and exudate. There is a more severe "proliferative" retinopathy with neovascularization (new blood vessel growth) that bleed easily and cause scarring to obscure vision. As the scar tissue contracts, the retina can be pulled away from the retinal pigment epithlelium to produce retinal detachment. There are methods for re-attachment of the retina (spot welding) but it must be done quickly to restore vision.
Hypertensive retinopathy: Hypertension can lead to arteriolosclerosis with retinal arteriolar narrowing along with flame-shaped hemorrhages, exudates, cotton-wool spots, and microaneurysms.
Arteriosclerotic retinopathy: The adventitia of the thickened arteriole compresses ("nicks") adjacent crossing veins. The very thickened arterioles have a "silver wire" appearance on fundusocopic examination.
