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Incidence of Cataract Surgery After Percutaneous Cardiac Intervention
JAMA Internal Medicine
2016;176(5):710-711
More than 1 million percutaneous cardiac intervention (PCI) procedures are performed each year in the United States. Although this procedure is done under x-ray guidance, the risk of radiation cataract among post-PCI patients has received little attention, and there are no current guidelines for patient eye protection. Using claims data from Taiwan’s National Health Insurance research database, Wei et al. conducted a retrospective matched-cohort study to evaluate the risk of cataract among patients after PCI.
The researchers identified 13,807 patients in Taiwan who had PCI between January 2001 and December 2012, and matched them 1:2 with 27,614 people in the database who had not undergone PCI. Matching was done according to birth year, sex, and diabetes status.
The researchers found that patients who had undergone PCI had an overall 25% increase in the incidence of cataract surgery, with evidence of a dose-response relationship depending upon the number of PCI procedures. They listed several reasons why the association had not previously been addressed: 1) the radiation dose of PCI was traditionally too low to cause immediately noticeable damage, and no reliable diagnostic method is available to detect radiation cataract; 2) common risk factors for coronary artery disease, such as diabetes, hypertension, smoking, and steroid use, also increase the incidence of cataract; and 3) data on the safe radiation threshold for the lens are uncertain, and it is difficult to set regulations to limit lens exposure for PCI.
The authors noted that in the past decade, procedures for complex cardiac conditions have become lengthier, and multiple procedures have become more common, resulting in higher cumulative radiation doses and increased risks for radiation damage. They recommend that PCI patients should wear eye protection during the intervention.
Glaucoma Prevalence in the United States: The 2005-2008 NHANES
Investigative Ophthalmology & Visual Science
2016;57(6):2577-2585
Gupta et al. estimated the prevalence of glaucoma in the U.S. population based on optic nerve head photography of participants in the National Health and Nutrition Examination Survey (NHANES) 2005-2008. They found an overall prevalence of 2.1% in this population, and more than half of the cases were previously undiagnosed.
The participants were 2,883 men and 2,863 women over age 40 who had gradable photographs of the macula and optic disc of both eyes. The images were first screened by a reading center, and participants with a cup-to-disc ratio ≥0.6 were further graded by 3 glaucoma specialists to determine the presence or absence of glaucoma.
Based on NHANES data, the researchers estimated that the overall prevalence of glaucoma in the U.S. civilian, noninstitutionalized population 40 years of age and older was 2.1%. Glaucoma affects 2.9 million individuals, including 1.4 million women; 1.5 million men; 2.3 million people 60 years of age and older; and 0.9 million blacks, Mexican-Americans, and people of other minority races. The prevalence of glaucoma was found to be highest in non-Hispanic blacks, followed by non-Hispanic whites, Mexican-Americans, and others.
Among the 172 participants with glaucoma detected on fundus photography, only 78 reported a previous diagnosis of glaucoma. Those who were unaware of their glaucoma status were more likely to be younger, to have a small disc, and to have an abnormal frequency-doubling visual field result, and were less likely to have notching or disc hemorrhages, compared with those who reported a glaucoma diagnosis.
The researchers concluded that data from NHANES 2005-2008 suggest that approximately 1.6 million people in the United States have undiagnosed glaucoma. Because timely treatment is critical, developing effective and practical screening algorithms for glaucoma is a clinical research priority and a requirement for disease control.
Visual Acuity After Gene Therapy for Choroideremia
New England Journal of Medicine
2016;374(20):1996-1998
In the Correspondence section, Edwards et al. reported on the 3.5-year follow-up of retinal gene therapy for choroideremia that they conducted in the United Kingdom. This condition, caused by loss-of-function mutations in the gene CHM, is characterized by atrophy of the choriocapillaris and retinal pigment epithelium (RPE), leading to vision loss.
In their initial investigation, the researchers had delivered nonmutated CHM in an adeno-associated virus vector (AAV.REP1) by subfoveal injection in the vicinity of the RPE and photoreceptor cells in 1 eye (study eye) each of 6 patients. In all patients, the worse-seeing eye received the treatment. Early improvement in visual acuity (VA) was reported in 2 of the 6 patients who received gene therapy (patients 1 and 4). These 2 patients had advanced disease, with the worst baseline VA in the study; the other 4 study patients had good baseline VA, which remained stable.
By 3.5 years, VA in the treated eye of Patient 1 had increased by 21 ETDRS letters (>4 lines) from baseline, while Patient 4 improved by 18 letters (>3 lines). In contrast, over the same time period, VA in the control eye decreased by 18 letters and 6 letters, respectively, in the 2 patients.
In the other 4 patients, who had good baseline acuity, VA remained stable in their treated eyes through the 3.5-year follow-up. However, in 3 of these 4 patients, the control eyes showed a decline in VA in that period.
The researchers contrasted their findings to those reported in 2 gene therapy studies for Leber congenital amaurosis (LCA). In the LCA studies, patients had initial gains in visual function, which subsequently declined. The researchers commented that the course is different between LCA and choroideremia or retinitis pigmentosa: The former disease usually causes profound loss of VA early on, while the latter conditions are characterized by progressive loss of visual field, with VA remaining close to normal until very late stages. Thus, they concluded that in some patients with choroideremia, the effect of preserving VA by means of retinal gene therapy may take several years to become apparent.
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Other Journals summaries are written by Marianne Doran and edited by Deepak P. Edward, MD.
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