Diseases of the eye affect the majority of the general population at some point throughout their lifetime, significantly affecting quality of life, especially if access to treatment is not available. They are so prevalent they account for the most common surgical procedure worldwide (cataract surgery), drive an industry for one of the most common medical devices (glasses), and inspire some of the highest resolution 3D imaging techniques available (OCT).

A nice glossary of Ophthalmological terms compiled by OpticianCertification.org can be found here, but without further ado here are five diseases of the eye that account for the majority of issues related to blindness or poor vision:

Cataracts:

A cataract is a clouding in one or both the eyes’ lenses typically due to age, trauma, genetics, smoking, and/or other factors. Lenses with cataracts are easily recognizable by their cloudy appearance, though the patient may not initially notice the gradual increase in cloudiness.

• Prevalence: 50% of population aged 65 and over
• Major Symptoms: Cloudiness of vision, blindness
• Physiological Causes: Deposited clumps of proteins or pigments in the lens
• Diagnosis: Visual examination of the eye
• Treatment: Cataract surgery to replace the lens with an intraocular lens (IOL) (this is the most common surgery in the world)

Refractive Error (including near- and far-sightedness):

Refractive error is essentially poor vision, typically brought on by genetics and/or age. Near-sightedness results in far-away objects appearing as blurry, far-sightedness and presbyopia result in close-by objects appearing as blurry, and astigmatism results in general blurriness.

• Prevalence: 14-28% of population, more in some areas
• Major Symptoms: Blurry vision
• Physiological Causes: Geometry issues with the eyeball, cornea or lens
• Diagnosis: Visual acuity test or Shack-Hartmann wavefront test
• Treatment: Glasses, laser eye surgery

Glaucoma:

Glaucoma is a group of diseases which affect the optic nerve, and are typically classified as open-angle (more common) or closed-angle (less common). Open-angle glaucoma develops very slowly and painlessly over time, where closed-angle glaucoma can be more acute and painful. Both are thought to be caused by drainage issues with the trabecular meshwork and the efficacy of Schlemm’s Canal, brought on by increased intraocular pressure, age, genetics, and/or hypertension, though there is no universally accepted reason behind the nerve damage.

• Prevalence:  2% of population aged 40 and over
• Major Symptoms: Blindness or partial blindness (typically gradually)
• Physiological Cause: Damage to the optic nerve
• Diagnosis: Tonometry (measuring intraocular pressure), dilated eye examination (to examine shape and colour of optic nerve), others
• Treatment: Symptoms reduced via medication, laser trabeculoplasty or surgery (including opening Schlemm’s canal or improving flow in the trabecular meshwork)

Age-Related Macular Degeneration:

The retinal macula is the high-resolution, cone-cell packed area in the center of the retina. Its degeneration is often brought on by age, smoking and/or genetics, and affects the ability of a patient to see objects straight ahead.

• Prevalence:  4% of population younger than 60, 12% aged 80 and over
• Major Symptoms: Partial Blindness (typically gradually)
• Physiological Cause: Degeneration of the macular via accumulation of harmful substances, the mechanism of which is varied and/or unclear
• Diagnosis: Examination of the eye, including some combination of optical coherence tomography (OCT), dark adaptation, contrast sensitivity, Amsler grid, Snellen chart, fundus photography, angiography, and others
• Treatment: No universal treatment exists that can restore lost vision, prevention is possible through a healthy lifestyle

Diabetic Retinopathy:

Retinopathy is damage to the retina of the eyes. Diabetic retinopathy is damage brought on by both type I and type II diabetes, and can manifest as macular edema (swelling) in 10% of cases.

• Prevalence: Makes up 5% of blindness worldwide, affects up to 80% of population having diabetes for over 20 years, leading cause of blindness among working age adults
• Major Symptoms: Partial blindness (typically gradually)
• Physiological Causes: Bulging and bursting of retinal blood vessels, neuron damage
• Diagnosis: Examination of vasculature through fundus photography, OCT, or FFA; examination of the eye; or standard visual acuity test
• Treatment: Laser photocoagulation, medication, or surgery to replace the vitreous with saline

Diagnostics and treatment of these diseases are often performed with precision opto-mechanical medical devices that continue to increase in reliability and accuracy and decrease in price every year. Most opto-mechanical medical devices are very complex, but even glasses and sunglasses are Class I Medical Devices under the FDA. Whichever way you look at it, eye diseases are more likely than not to affect our lives; but thanks to a number of reliable medical devices and proven procedures, most are treatable quickly and safely.