When causes of vision loss are looked at from a global perspective, diabetic retinopathy--that is, damage to the retina due to diabetes--is one of the most significant causes. Cornell Medical College physicians Claire Fraser and Donald D'Amico, writing in the medical database UpToDate, suggest that diabetic retinopathy is one of the main reasons for vision impairment in people ages 25 to 74 years old. Although symptoms often do not appear until late in the progression of the disease, treatment may reduce symptoms and slow the disease, so knowledge of symptoms of diabetic retinopathy is important.
Vision Loss Due To Macular Edema
One aspect of diabetic retinopathy is the damage to tiny blood vessels in the retina called capillaries. When these become damaged and leak, the macula area of the retina can become swollen with fluid; this is called macular edema. The result of macular edema is a decrease in visual acuity; the patient feels that her vision is not as clear as it normally is. Both near vision and distant vision eventually become affected as a larger area of the macula becomes swollen and damaged.
Retinal Detachment Due to New Vessel Formation
A second component of diabetic retinopathy is one called neovascularization. This refers to the formation of new blood vessels that branch off of existing blood vessels of the retina. In a subtype of diabetic retinopathy called proliferative diabetic retinopathy, these new vessels cause the retina of the eye to distort and ultimately detach, resulting in loss of vision in the eye and requiring surgery to repair the detachment.
Acute Glaucoma Due to New Vessel Formation
If the neovascularization process of diabetic retinopathy also occurs within an eye structure called the anterior chamber, the fluid within the eye, called aqueous humor, has no way to flow normally. Instead, it is blocked off by the new blood vessels, causing pressure within the eye to go up to dangerous levels. This is called acute, closed-angle glaucoma. Dr. John Salmon, writing in the ophthalmology textbook "Vaughan & Asbury's General Ophthalmology," suggests that a patient with glaucoma will often experience intense pain, nausea and vomiting, and the appearance of "halos," along with a sudden decrease in his vision. This is an ophthalmological emergency--a patient with acute glaucoma needs to be seen by an ophthalmologist and treated immediately to bring the eye pressure back to normal levels.
"Floaters" Due to Bleeding Within the Eye
The vessels that form during the neovascularization process are much more fragile and prone to breakage than the original vessels were. One consequence of this fragility is the tendency for vessels to break and bleed into the jelly-like substance of the eye called the vitreous. This is called a vitreous hemorrhage and may result in patients experiencing a sensation of "floaters" in their vision. These are described in "Vaughan & Asbury's General Ophthalmology" as spider webs, rings, or flying saucer-like objects that patients perceive as being somewhere in their field of vision, either directly in front of them or when they look to the side.
References
- "Vaughan & Asbury's General Ophthalmology;" 2008
- "Emergency Medicine: A Comprehensive Study Guide"; Judith E. Tintinalli, MD, MS et. al.; 2004
- "UpToDate"; Denise S. Basow; 2010
