Does eyesight primarily deteriorate 'naturally' due to genetics (genomic/epigenomic factors), or due to external factors such as normal wear and tear, or disease?

By normal wear and tear I include things like repetitive straining of the eyes by reading small text in a dim room night after night.

As a background to my question: By dissecting the causes of visual deterioration into genetic factors versus external factors I hope to relate those causes to the age of onset, and rate of decay of visual acuity.

  • $\begingroup$ What exactly is the difference between "natural deterioration" and "degradation through wear and tear"? To me, these are the same and the question is quite unclear, as @anongoodnurse also suggests. $\endgroup$ – AliceD Nov 8 '14 at 3:28
  • $\begingroup$ Also, the title and question body don't match. Please clarify the question. $\endgroup$ – AliceD Nov 8 '14 at 4:15
  • $\begingroup$ @ChrisStronks - I apologize for my ambiguity. By "natural degradation" I mean an aging process predetermined in length and intensity by some biological factor in the human gene/genome similar to the 'lottery' of vision that is 'given out' at birth. The distinction I am attempting to make between this and aging broadly is the specificity of age of onset and rate of decay. $\endgroup$ – slimputent Nov 10 '14 at 17:10
  • $\begingroup$ By "wear and tear" and "over-stimulation" I am implying environmental/behavioral factors such as repetitive straining of the eyes by reading small text in a dim room night after night. The reason I didn't ask specifically about reading is because I'd like to know the broader answer about why does vision degradation occur when it does. Does that help? $\endgroup$ – slimputent Nov 10 '14 at 17:13
  • $\begingroup$ please adapt your question and specify what you want to know. From the comment on @anongoodnurse it seems you specifically want to know something about accommodation, while from the above comment it seems you want a very broad answer. Please specify. $\endgroup$ – AliceD Nov 10 '14 at 23:16

Vision deteriorates for both reasons, but I'm not quite sure how to separate the effects of aging from wear and tear.

Cataracts are the leading cause of blindness in the world. Ways in which environment (which falls under the category of wear and tear in my book) affects cataract formation:

  • UV light: people living at high altitudes (e.g. Tibet) have more cataracts 2° to increased UV light than those at lower altitudes (sunglasses with UV protection delays the process)
  • lead exposure increases cataract formation.
  • infections in infancy and childhood (rubella, toxoplasmosis, other)

Macular degeneration is another cause of vision loss. Environmental factors include:

  • smoking: speeds up age related macular degeneration.
  • diet: diets low in antioxidants, and obesity increase degeneration.

Retinal damage caused by diabetic retinopathy:

  • Juvenile onset diabetes has long been thought to be associated with viral infections from coxsackievirus B, cytomegalovirus, adenovirus, rubella, and mumps.
  • Type II diabetes is influences by obesity, lack of exercise, certain medications, (nicotinic acid, some diuretics, anti-epileptics, psychiatric drugs, and drugs to treat HIV (can impair beta cells or disrupt insulin action); Pentamidine (used to treat a type of pneumonia) can cause pancreatitis and diabetes; glucocorticoids/steroid hormones may impair insulin action.

Corneal opacities:

  • infections: (Chlamydia trachomatis) bacteria that are spread by close contact with an infected person or by flies, especially common in Africa.
  • recurrent injury (soot and pathogens from indoor smoke, a dusty, windy environment).
  • vitamin A deficiency

Nearsightedness: - near-point work: reading, working with a computer all day, etc.

Glaucoma: - diabetes, obesity, near-point work, other.

Nonenvironmental causes would be genetics and illnesses associated with aging.

  • genetic predispositions associated with diabetes, nearsightedness and farsightedness
  • decreased lens plasticity with age
  • strokes secondary to hypertension, etc.
  • amblyopia (“lazy eye”), strabismus (when eyes are aligned in different directions), astigmatisms
  • hereditary causes of glaucoma and age-related macular degeneration
  • retinitis pigmentosa, (degenerative disease of the retina)
  • innumerable genetic disorders (Marfan's, Tay-Sachs, Albinism, Cone-rod dystrophy, various autoimune disorders, etc.
  • retinoblastoma
  • predisposition to glaucoma

Focusing on Vision Through an Environmental Lens
Glossary of Eye Conditions
Causes of Diabetes
Inherited Eye Disease

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  • $\begingroup$ @anongoodnurse - You answered perfectly, especially given that I am new to Stack Exchange and very poorly worded the question. Your answer was incredibly informative about the types of diseases that affect vision and their factors. My initial inquiry (perhaps naively and certainly not communicated correctly) was what causes the deterioration of vision in individuals who's visual health is not affected by any disease, but have only behavioral factors and biological predispositions as possible culprits. I'm a little lost at this point about how to pursue an answer to that question, however. $\endgroup$ – slimputent Nov 12 '14 at 18:24

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