Featured Research

from universities, journals, and other organizations

Visual Decline As We Age: Genetics Or Environment?

Date:
February 11, 2009
Source:
American Academy of Ophthalmology
Summary:
Which has a larger impact on the "normal" decline of visual function as we age, genetic or environmental factors? This question is explored in the February issue of Ophthalmology, the journal of the American Academy of Ophthalmology.

Which has a larger impact on the "normal" decline of visual function as we age, genetic or environmental factors? This question is explored in the February issue of Ophthalmology, the journal of the American Academy of Ophthalmology.

Vision worsens for most of us as we age, even in the absence of eye diseases such as glaucoma or AMD. Elders who have good visual acuity (20/25 vision or better) may have trouble driving at night or adjusting when they move between indoor and outdoor light. Some declines are optic, such as presbyopia, reduced flexibility of the eye's lens, which causes poorer near vision for many people after age 40. Other declines are neuronal, related to the eye's ability to send images to the brain. Since crucial functions like reading and memory depend on vision, it is important to understand how "normal" aging occurs and discover what can be done to delay or prevent reduced function. In the first investigation of heredity's impact on neuronal visual decline, Ruth E. Hogg, PhD, of the University of Melbourne, Australia, and her colleagues used a classic twin study to explore genetic and environmental factors.

Study participants were a cohort of the AMD twin study by the University of Melbourne Centre for Eye Research, comprised of eighty-four twins (42 pairs, 21 identical and 21fraternal) between the ages of 57 and 75 who met study criteria for visual acuity and absence of eye disease. In each person the eye with the best visual acuity (or the right eye if acuity was equal in both eyes) was tested for adaptation to light level changes, for color detection, and for detection of gray tone gradations between image and background, termed contrast sensitivity. Taken together, these tests assess key visual functions needed in daily life. When test results showed that a visual ability declined at about the same age in identical twins, the trait was assumed to be under genetic control, and when the decline occurred at different ages, environmental factors were considered dominant. Results for identical twins and fraternal (non-identical) were compared, and when concordance between scores was higher for identical than for fraternal pairs, genetics was assumed to be the controlling factor.

Genetic factors appear to be strong determinants of sharp visual acuity and color discrimination, functions performed by cone cells pathways in the eye's retina, the tissue at the back of the eye that converts light into electronic images for relay to the brain. Genetic factors were not strongly correlated with night vision and the ability to adapt to light level changes, which are performed by retinal rod cells, implying that environmental influences are important to those functions. Autopsies and other studies have found that substantially more rod than cone cells are lost as eyes age. The flow of nutrients across the retinal membrane appears to be more important for rod cell than for cone cell function, and it is here that environmental factors—such as smoking, deficient nutrition, excessive sunlight exposure, and inflammation---may influence visual decline. Rod cell deterioration is accepted as a component of both general visual decline and age-related diseases like AMD, the most common cause of visual disability in elders.

"Our results support clinical and research efforts now underway to slow or stop age-related vision decline by modifying lifestyle factors and/or using specific medications," says Dr. Hogg.


Story Source:

The above story is based on materials provided by American Academy of Ophthalmology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ruth E. Hogg, Peter N. Dimitrov, Mohamed Dirani, Mary Varsamidis, Matthew D. Chamberlain, Paul N. Baird, Robyn H. Guymer, Algis J. Vingrys. Gene-Environment Interactions and Aging Visual Function: A Classical Twin Study. Ophthalmology, 2009; 116 (2): 263 DOI: 10.1016/j.ophtha.2008.09.002

Cite This Page:

American Academy of Ophthalmology. "Visual Decline As We Age: Genetics Or Environment?." ScienceDaily. ScienceDaily, 11 February 2009. <www.sciencedaily.com/releases/2009/02/090202183038.htm>.
American Academy of Ophthalmology. (2009, February 11). Visual Decline As We Age: Genetics Or Environment?. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2009/02/090202183038.htm
American Academy of Ophthalmology. "Visual Decline As We Age: Genetics Or Environment?." ScienceDaily. www.sciencedaily.com/releases/2009/02/090202183038.htm (accessed August 1, 2014).

Share This




More Health & Medicine News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

House Republicans Vote to Sue Obama Over Healthcare Law

House Republicans Vote to Sue Obama Over Healthcare Law

Reuters - US Online Video (July 31, 2014) The Republican-led House of Representatives votes to sue President Obama, accusing him of overstepping his executive authority in making changes to the Affordable Care Act. Mana Rabiee reports. Video provided by Reuters
Powered by NewsLook.com
Despite Health Questions, E-Cigs Are Beneficial: Study

Despite Health Questions, E-Cigs Are Beneficial: Study

Newsy (July 31, 2014) Citing 81 previous studies, new research out of London suggests the benefits of smoking e-cigarettes instead of regular ones outweighs the risks. Video provided by Newsy
Powered by NewsLook.com
Dangerous Bacteria Kills One in Florida

Dangerous Bacteria Kills One in Florida

AP (July 31, 2014) Sarasota County, Florida health officials have issued a warning against eating raw oysters and exposing open wounds to coastal and inland waters after a dangerous bacteria killed one person and made another sick. (July 31) Video provided by AP
Powered by NewsLook.com
Health Insurers' Profits Slide

Health Insurers' Profits Slide

Reuters - Business Video Online (July 30, 2014) Obamacare-related costs were said to be behind the profit plunge at Wellpoint and Humana, but Wellpoint sees the new exchanges boosting its earnings for the full year. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins