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Lutein & Vitamin A May Slow Mid-Peripheral Vision Loss in Retinitis Pigmentosa
Lutein and Vitamin A in Retinitis Pigmentosa
Retinitis pigmentosa (RP) causes progressive vision loss to about 1 in 4000 people worldwide. Patients typically report deficient night vision in adolescence, and loss of mid-peripheral and then far peripheral field in adulthood with development of tunnel vision. Central vision is usually lost after age 60.
The previous issue of EduFacts (Vol. 11, No. 1) summarized an investigation that found macular pigment optical density (MPOD) to be independently related to serum lutein in patients with retinitis pigmentosa (1). Provocative results from a new clinical trial suggest that lutein and vitamin A supplements might help preserve mid-peripheral vision in RP (2).
Study Design
The objective of this randomized, controlled, double-masked trial was to determine whether lutein supplementation slows visual function decline in patients with RP also receiving vitamin A at a level previously reported by the same investigators to slow the rate of RP progression.
Two hundred twenty five non-smoking patients, aged 18 to 60 years, were evaluated over a 4-year interval. Patients received 12 mg of lutein or placebo daily in addition to 15,000 IU/day of vitamin A palmitate. Randomization took into account genetic type and baseline serum lutein level.
The primary outcome was the total point score for the Humphrey Field Analyzer (HFA) program that measures central visual field (program 30-2). Secondary outcomes were the total point scores for the program that measures mid-peripheral visual field (program 60-4) and for these two programs combined, along with 30-Hz electro-retinogram amplitude, and Early Treatment Diabetic Retinopathy Study acuity.
Results
While there was no difference between groups in the rate of vision loss for the primary outcome measure, a significant effect of treatment on the rate of loss for the mid-peripheral visual field was observed (HFA 60-4 total point score, p=.05).
Mean decline in mid-peripheral loss was slower among those with the highest serum lutein level or with the highest increase in MPOD at follow up (p=.01 and .006, respectively).
Those with the highest increase in MPOD also had the slowest decline in central and mid-peripheral loss (HFA 30-2 and 60-4 combined field sensitivity, p=.005).
Comments
The researchers conclude that their data support the use of 12 mg/d of lutein to slow visual field loss among nonsmoking adults with retinitis pigmentosa taking vitamin A. Based on the randomized comparison, the authors estimate that the benefit in preserving mid-peripheral field sensitivity would be an additional 3 years. Based on MPOD observational results, they estimate that the benefit would be 10 additional years.
In the latter case, a patient taking vitamin A who begins supplemental lutein at age 40 could expect to lose mid-peripheral field by age 61 compared to age 51 for those not taking lutein according to the authors. Patient follow-up would be needed to confirm these estimates.
An accompanying editorial (3) points out that the study was well designed and executed, but questions how much weight should be placed on clinical recommendations that are based on secondary analyses. Others, however, might well argue that there is no other viable treatment for RP and the conclusions drawn by the investigators are reasonable.
Reference
1. Sandberg MA, et al. The relationship of macular pigment optical density to serum lutein in retinitis pigmentosa. Invest Ophthalmol Vis 51:1086–91, 2010.
2. Berson EL, et al. Clinical trial of lutein in patients with retinitis pigmentosa receiving vitamin A. Arch Ophthalmol 128:403-11, 2010.
3. Massof RW and Fishman GA. How strong is the evidence that nutritional supplements slow the progression of retinitis pigmentosa? Arch Opthalmol 128:493-5, 2010.
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