It was believed that the light-absorbing nature of these lens implants might offer advantages over clear lens implants, including providing sharper vision, better contrast sensitivity and reduced risk of macular degeneration.

But recent research has shown that blue-blocking IOLs fail to provide measureable visual or eye-protective benefits for people under going cataract surgery, according to two reports in this month’s issue of Survey of Ophthalmology. In fact, blue-blocking IOLs may perform worse than clear IOLs in some measures of visual performance.

In the first report, researchers at the University of Kansas School of Medicine say blue-blocking IOLs fail to decrease glare or improve contrast sensitivity, and the reduced light transmittance of the blue-blocking lens implants appears to reduce visual performance in dim and dark environments.

The researchers also say that most scientific evidence shows that environmental light exposure and cataract surgery are not significant risk factors for the progression of age-related macular degeneration (AMD), and that blue-blocking IOLs are unlikely to prevent or reduce one’s risk of AMD.

In the second report, researchers at Ophthalmic Consultants of Boston and Harvard Medical School reviewed the results of 56 peer-reviewed studies of blue-blocking IOLs. Eleven of these studies directly compared the visual outcomes of blue-blocking IOLs and conventional (non-blue-blocking) lens implants.

Of the 11 studies that directly compared the two types of IOLs, 10 of the studies (91 percent) concluded that blue-blocking IOLs offered no significant benefits over conventional IOLs in measures of visual performance that included visual acuity, contrast sensitivity, color perception and visual sensitivity in bright, medium and low-light conditions.

The researchers said one study suggested blue-blocking IOLs might produce worse vision than clear IOLs in low-light conditions and could possibly affect circadian rhythms and thereby cause sleep disturbances in susceptible individuals.

Also, regarding the possible protective effect of shielding the retina from blue light, the researchers said the benefits of blocking the transmittance of blue light to the retina and the relationship between light transmittance and the progression of AMD “remain unclear.”

Ed. note:  Blue-blocking IOLs are one of many types of premium refractive IOLs used in cataract surgery and refractive lens exchange. Ask your refractive surgeon to discuss your IOL options during your pre-surgical consultation.

SOURCES:
1. Blue-blocking IOLs decrease photoreception without providing significant photoprotection. Survey of Ophthalmology. May 2010.
2. Blue-blocking IOLs: A complete review of the literature. Survey of Ophthalmology. May 2010.

AMD and cataract surgery: Study design and methods

Patients with cataracts and early macular degeneration who were deemed to be at high risk of having their AMD progress to a more serious and more vision-threatening form of the disease were randomly assigned to two groups:

• The study group (27 patients) underwent immediate phacoemulsification-style cataract surgery.
• The control group (29 patients) had cataract surgery deferred for six months.

At both the beginning of the study and six months after the study group had their cataract surgery (before the control group did), all subjects were assessed using the following criteria:

• visual acuity
• quality of life (measured via questionnaire)
• fundus fluorescein angiography (FFA)

FFA is a diagnostic test that uses an injected dye to determine if there is any leakage of retinal blood vessels or abnormal new blood vessel growth in the choroid — the layer of the eye that underlies the cornea and nourishes it.

Such blood vessel growth is called choroidal neovascularization, or CNV, and this represents the beginning of a more advanced stage of macular degeneration called “wet” AMD. New blood vessels formed by CNV can leak into the retina and cause severe vision loss.

Eyes with unsuspected pre-existing CNV that was detected by fluorescein angiography were disqualified from the study.

AMD and cataract surgery: Study results

Findings of the study at the 6-month mark included:

• Of the 27 eyes that underwent cataract surgery, one eye (3.7 percent) developed CNV, compared with none in the control group of 29 eyes that did not have surgery.
• The mean visual acuity improvement among study eyes that underwent cataract surgery was a 2.8-line improvement on a standardized eye chart.
• AMD patients who underwent cataract surgery reported more than a two-fold average improvement in quality of life scores, as measured by a standardized questionnaire.

The development of CNV in one eye among the study group compared with no eyes in the control group did not meet the criterion of statistical significance.

Conclusions

The researchers concluded there is no increased short-term risk of progression of AMD to CNV in high-risk individuals following uncomplicated phacoemulsification cataract surgery.

Also, provided there is no CNV, there are distinct quality of life benefits of cataract surgery in people with early AMD, the researchers said.

It should be noted that the follow-up period of this study was six months. Studies with longer follow-up periods are needed to determine long-term risks of cataract surgery among patients with early AMD.

SOURCE:  Cataract surgery in high-risk age-related macular degeneration: a randomized controlled trial. Clinical & Experimental Ophthalmology. August 2009.