Is UV Radiation Linked to Cataracts? A Review of Epidemiological Evidence

[Nereid]

In another thread there's a discussion of the wavelength limits of the human visual system.

A question has arisen re the damage that UV can have on the eye; specifically by wavelength and intensity.

Can anyone help? There's tons of material on the internet, but how to judge what's authoratitive?

 

[Monique]

What exactly do you want to know? Radiation is absorbed by the eye and UV radiation at short wavelengths of 290-320 nm (UV-B) is readily absorbed by DNA and induces thymine dimers: a particular DNA mutation. Also, since it's ionizing radiation, free radicals are produced, which are also damaging.

 

[Nereid]

Thanks Monique.

UV longer than 320nm - what sort of damage does it cause to eyes? E.g. cataracts?

High intensity light - of just about any wavelength? - e.g. staring at the Sun will damage your eyesight (how? what specifically is damaged?). Since UV isn't 'visible' (except just 'blue' of 'violet') except maybe at high intensity (the blue receptors do apparently have some response at short wavelengths, but <1% of that at the peak sensitivity), what sort of damage would you be doing to your eyes if you looked at a very bright UV source, e.g. at 380nm, or 370nm? Would the UV do more damage than (say) the same intensity (and duration) of 'visible' light (e.g. 500nm)?

 

[Monique]

trusty source, nasa: http://earthobservatory.nasa.gov/Library/UVB/

 

[imabug]

Thanks Monique.

UV longer than 320nm - what sort of damage does it cause to eyes? E.g. cataracts?

I believe the primary effect of UV overexposure is an increased risk of developing cataracts. Keep in mind that cataract development is a slow process that occurs over several decades. Staring at a UV source isn't going to give you a cataract right away.

 

[Monique]

For literature: http://www.pubmed.com search for 'cataract uv radiation'.

Here's a recent abstract:

Exp Gerontol. 2004 Jan;39(1):139-46.


Effects of UV-A irradiation on lens morphology and optics.

Azzam N, Levanon D, Dovrat A.

B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 7 Efron St., P.O. Box 9649, Haifa 31096, Israel.

Epidemiological studies have indicated that ultraviolet radiation (UVR) is one of the main factors leading to senile cataract formation. We investigated morphological changes in the eye lens caused by UVR-A. Twenty three pairs of lenses obtained from 23 one-year-old calves were used for this study. For each pair, one lens was exposed to 44 J/m(2) UVR in the 365 nm wavelength region while the contralateral lens was not exposed and served as a control. The lenses were placed in specially designed organ culture containers for pre-incubation. Lenses were exposed to UVR after one day in culture. After irradiation, lens optical quality was monitored throughout additional 15 days of the culture period and lenses were taken for morphological analysis by scanning electron microscopy. Damage to lens optical quality was evident as early as day 8 after the irradiation and increased with time in culture. We found irregularity of fiber morphology in lenses exposed to UV-A irradiation (but not in control lenses), similar to that reported previously for aged lenses. At the end of the culture period (day 16), lens fiber membranes also showed holes in fiber membranes. We conclude that UVR-A caused damage to cell membranes of the lens and alterations in lens optics, which may subsequently lead to senile cataract formation.

PMID: 14724074 [PubMed - indexed for MEDLINE]

 

[Monique]

A review on epidemiological studies on cataracts and uv radiation:

Dev Ophthalmol. 2002;35:21-31.

A review of the epidemiologic evidence linking ultraviolet radiation and cataracts.

McCarty CA, Taylor HR.

Centre for Eye Research Australia, University of Melbourne, Australia.

BACKGROUND/AIMS: Cataract is the most common cause of blindness in the world and there are currently no strategies to prevent it. The aim of this paper is to review the epidemiologic evidence linking ultraviolet (UV) radiation and cataract. METHODS: Published epidemiologic research articles on UV and cataract were reviewed against the epidemiologic criteria for causality: biological plausibility, strength of the association, specificity, experimental evidence, temporal sequence of events, dose-response relationship, and consistency. RESULTS: The majority of the 22 epidemiologic studies reviewed met most of the epidemiologic criteria for causality and support an association between UV-B and the development of cortical cataract and perhaps posterior subcapsular cataract. CONCLUSIONS: The epidemiologic data justify the implementation of public health campaigns to raise public awareness of the risk of cortical cataract due to ocular UV-B exposure. Future researchers should be careful to avoid potential bias by measuring personal ocular UV exposure and by quantifying cataract carefully.

Publication Types:
Review
Review, Tutorial

PMID: 12061276 [PubMed - indexed for MEDLINE]