Blue-blocking, or yellow, IOLs have been a topic of debate. The controversy lies in designing an IOL that provides the right balance between retinal photoprotection and visual performance. The focus of this review is on blue-blocking IOLs and their effect on color and contrast sensitivity, age-related macular degeneration (AMD), and UV light exposure. Some researchers support the use of yellow IOLs as a tool to provide better safety for the aging eye, although others argue that blue-blocking IOLs will limit functional vision. Additional researchers examined the relationship between UV light exposure and AMD. The following articles were reviewed:
1. Ernest PH. Light-transmission-spectrum comparison of foldable intraocular lenses. J Cataract Refract Surg. 2004;30:1755-1758.
2. Mainster MA, Sparrow JR. How much blue light should an IOL transmit? Br J Ophthalmol. 2003;87:1523-1529.
3. Rodriguez-Galietero A, Montes-Mico R, Monuz G, Albarran-Diego C. Comparison of contrast sensitivity and color discrimination after clear and yellow intraocular lens implantation. J Cataract Refract Surg. 2005;31:1736-1740.
4. Owsley C, Jackson GR, White M, et al. Delays in rod-mediated dark adaptation in early age-related maculopathy. Ophthalmology. 2001;108:1196-1202.
5. Delcourt C, Carriere I, Ponton-Sanchez A, et al. Light exposure and the risk of age-related macular degeneration. Arch Ophthalmol. 2001;119:1463-1468.
6. Tomany SC, Cruickshanks KJ, Klein R, et al. Sunlight and the 10-year incidence of age-related maculopathy. Arch Ophthalmol. 2004;122:750-757.
7. Klein R, Peto T, Bird A, Vannewkirk MR. The epidemiology of age-related macular degeneration. Am J Ophthalmol. 2004;137:486-495.
THE ADVENT OF BLUE-BLOCKING IOLs
Throughout life, the crystalline lens protects the retina from hazardous UV light. Cataract extraction removes this protective barrier and may accelerate retinal phototoxicity. To control the amount of radiation transmitted to the retina after cataract surgery, IOLs were created with the capability of blocking UV radiation. All IOLs today block short-wavelength UV radiation up to 400nm. Blue-absorbing chromophores were added to IOL technology in the 1990s to expand protection and decrease the amount of UV-blue energy (400- to 500-nm range) reaching the retina (Figure 1). It was thought that adding a blue-blocking chromophore increased protection from photic retinopathy because it simulated the properties of the natural crystalline lens.1
EFFECT ON NIGHT VISION
Although implanting a blue-blocking IOL can increase the amount of retinal protection, there is some argument about whether this filter alters a patient's visual performance. According to Mainster et al,2 blocking blue light, although beneficial during daylight hours, can limit visual performance in scotopic conditions, especially in aging individuals (Figure 2). Compared with a conventional lens that only blocks UV light, IOLs with blue-blocking capabilities reduce scotopic sensitivity by 25%.2
Rodriguez-Galietero et al3 compared visual performance measures such as contrast sensitivity and color vision in 40 subjects between the ages of 65 and 70 years. The subjects received a yellow IOL in one eye and a colorless, UV-filtering IOL in their fellow eye. Monocular contrast sensitivity and color vision were assessed for each subject at 3 months postoperatively. The study's results demonstrated similar contrast sensitivity function at all frequencies between the eyes. Additionally, compared with the colorless IOL, the yellow IOL did not negatively influence patients' color discrimination.
Night vision can be compromised for older adults with preexisting retinal conditions such as AMD. A study by Owsley et al4 investigated disturbances in dark adaptation in patients with early AMD. Twenty older adults (between 66 and 88 years old) with early signs of AMD and 16 adults with normal retinas were measured. Using a Humphrey Field Analyzer (Carl Zeiss Meditec Inc., Dublin, CA), investigators measured the rate of rod-mediated sensitivity recovery after exposure to 98% bleach. All patients had a pretesting visual acuity of 20/25. Researchers also assessed each patient's visual acuity and scotopic, contrast , and photopic sensitivities. The results of the study showed that, despite good visual acuity, patients with early AMD exhibited deficits in dark adaptation compared with the participants who had normal retinas.
AMD AND UV LIGHT EXPOSURE
Besides the potential impact of a yellow lens on scotopic sensitivity and color vision, some researchers have investigated the relationship between UV light exposure and the progression of early AMD. Recent evidence from large, population-based studies regarding the relationship between AMD and UV light exposure has been inconclusive.
The Pathologies Oculaires Liées à l'Age (POLA) study5 examined the relationship between cataracts, AMD, and risk factors for the disease. More specifically, this population-based study investigated a lifetime of light exposure among 2,584 residents in a harbor town in southern France. Patients were classified based on color fundus photographs of their maculas. Of the participants examined, those exposed to high amounts of solar radiation both professionally and leisurely were found to have pigmentary abnormalities less frequently. Subjects who claimed to have used sunglasses when outdoors had a reduced risk for soft drusen. The POLA study concluded that the examination did not support “a deleterious effect of sunlight exposure in AMD.”
The Beaver Dam Eye Study6 evaluated the association of sunlight with the 10-year incidence of AMD. Conducted in Beaver Dam, Wisconsin, data were collected on patients who were between the ages of 43 and 86 years. Residential history, time spent outdoors, and the use of hats and sunglasses were considered. Unlike the POLA study, this research showed an association between cumulative sun exposure and increased retinal pigmentation. However, investigators found that the use of hats and sunglasses did not prevent the progression of AMD at 10 years. The Beaver Eye Dam Study did not find a significant relationship between UV light exposure and the 10-year incidence and progression of AMD.
The Age-Related Eye Disease Study,7 a clinical trial sponsored by the National Eye Institute, reviewed the epidemiology responsible for causing AMD. According to this study, the consistent risk factors for AMD have been age and a family history of the condition. Furthermore, the review identified smoking, hypertension, and cataract surgery as associated causes of AMD. According to data from the Age-Related Eye Disease Study, threats for AMD do not include an exposure to UV-B light.
Current IOLs that only block UV light are excellent at protecting the retina from potentially harmful light. Older patients with preexisting retinal disease would benefit from maximized scotopic vision. Adding chromophores to provide further photoprotection from blue light may be important, but that benefit must be balanced against any cost to patients' functional vision.
Dr. Chu acknowledged no financial interest in any product or company mentioned herein. He may be reached at (952) 835-1235; firstname.lastname@example.org.
Dr. Matsumoto acknowledged no financial interest in any any product or company mentioned herein. She may be reached at (952) 835-1235; email@example.com.
Helen Boerman, OD, is Assistant Clinical Operation Manager at Wang Vision Institute in Nashville, Tennessee, and is Staff Physician, Adjunct Faculty at Indiana University School of Optometry in Bloomington. She acknowledged no financial interest in any product or company mentioned herein. Dr. Boerman may be reached at (615) 321-8881; firstname.lastname@example.org.
Wei Jiang, MD, is a resident in ophthalmology at the Jules Stein Eye Institute in Los Angeles. She acknowledged no financial interest in any product or company mentioned herein. Dr. Jiang may be reached at (310) 825-5000; email@example.com.
Baseer Khan, MD, FRCS(C), is a fellow of glaucoma and anterior segment at the University of Toronto. He acknowledged no financial interest in any product or company mentioned herein. Dr. Khan may be reached at (415) 258-8211; firstname.lastname@example.org.
Patty Lin, MD, MBA, is a resident in ophthalmology at the Jules Stein Eye Institute in Los Angeles. She acknowledged no financial interest in any product or company mentioned herein. Dr. Lin may be reached at (310) 825-5000; email@example.com.
Gregory J. McCormick, MD, is a cornea and refractive fellow at the University of Rochester Eye Institute in New York. He acknowledged no financial interest in any product or company mentioned herein. Dr. McCormick may be reached at (585) 2562569; firstname.lastname@example.org.
Jason Noble, BSc, MD, is a resident in ophthalmology at the Department of Ophthalmology at the University of Toronto. He acknowledged no financial interest in any product or company mentioned herein. Dr. Noble may be reached at email@example.com.
Lav Panchal, MD, is a fellow at the Wang Vision Institute in Nashville, Tennessee. He acknowledged no financial interest in any product or company mentioned herein.
Dr. Panchal may be reached at (917) 751-8651;
Jay S. Pepose, MD, PhD, is Professor of Clinical Ophthalmology & Visual Sciences, Washington University School of Medicine, St. Louis. He acknowledged no financial interest in any product or company mentioned herein.
Dr. Pepose may be reached at (636) 728-0111;
Paul Sanghera, MD, is senior resident in ophthalmology in the Department of Ophthalmology and Vision Sciences at the University of Toronto. He acknowledged no financial interest in any product or company mentioned herein.
Dr. Sanghera may be reached at (416) 666-7115; firstname.lastname@example.org.
Renée Solomon, MD, is an ophthalmology fellow at Ophthalmic Consultants of Long Island in New York. She acknowledged no financial interest in any product or company mentioned herein. Dr. Solomon may be reached at email@example.com.
Tracy Swartz, OD, MS, acknowledged no financial interest in any product or company mentioned herein. She may be reached at (615) 321-8881;
Ming Wang, MD, PhD, acknowledged no financial interest in any product or company mentioned herein. He may be reached at (615) 321-8881;