***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: PURPOSE Docosahexaenoic acid ( DHA ) was supplemented in a single-site , placebo-controlled , r and omized clinical trial design ed to slow vision loss associated with X-linked retinitis pigmentosa ( XLRP ) ; the DHAX Trial . We previously reported no significant differences between supplemented and placebo groups in intent-to-treat analysis of primary ERG outcomes . Assessed herein are hypothesis-generating measures of ancillary visual function outcomes in participants fully adhering to trial protocol . METHODS Male participants with XLRP ( range , 7 - 31 years ) received 30 mg DHA/kg/d ( n = 29 ) or placebo ( n = 22 ) for 4 years . Visual outcomes were measured annually and red blood cell ( RBC ) DHA determined every 6 months . RESULTS Oral DHA supplementation increased mean RBC-DHA levels by 4-fold ( P < 0.0001 ) over placebo . No group differences in progression were found for visual acuity ( P = 0.11 ) , shape discrimination ( P = 0.18 ) , or fundus appearance ( P = 0.70 ) . Optical coherence tomography ( OCT ) became available during year 2 of the trial ; no group differences were seen in ellipsoid zone constriction ( P = 0.87 ) over 2 years . Yearly rates of progression were reduced for dark-adapted thresholds ( P = 0.06 ) and visual field sensitivity for foveal , macular , peripheral , total , and ellipsoid zone regions by DHA supplementation ( P = 0.039 , P = 0.031 , P < 0.0001 , P < 0.0001 , and P = 0.033 ) . Rates of visual field sensitivity decline were dependent on RBC-DHA ( P = 0.046 to < 0.0001 ) . CONCLUSIONS Supplementation of DHA significantly elevated blood DHA levels and reduced the rate of progression in final dark-adapted thresholds and visual field sensitivity . From the relationship between RBC-DHA and the rate of field sensitivity loss , we can extrapolate that an RBC-DHA level of 17 % could minimize the decline in field sensitivity . ( Clinical Trials.gov number , NCT00100230 . OBJECTIVE To determine whether supplements of vitamin A or vitamin E alone or in combination affect the course of retinitis pigmentosa . DESIGN R and omized , controlled , double-masked trial with 2 x 2 factorial design and duration of 4 to 6 years . Electroretinograms , visual field area , and visual acuity were measured annually . SETTING Clinical research facility . PATIENTS 601 patients aged 18 through 49 years with retinitis pigmentosa meeting preset eligibility criteria . Ninety-five percent of the patients completed the study . There were no adverse reactions . INTERVENTION Patients were assigned to one of four treatment groups receiving 15,000 IU/d of vitamin A , 15,000 IU/d of vitamin A plus 400 IU/d of vitamin E , trace amounts of both vitamins , or 400 IU/d of vitamin E. MAIN OUTCOME MEASURE Cone electroretinogram amplitude . RESULTS The two groups receiving 15,000 IU/d of vitamin A had on average a slower rate of decline of retinal function than the two groups not receiving this dosage ( P = .01 ) . Among 354 patients with higher initial amplitudes , the two groups receiving 15,000 IU/d of vitamin A were 32 % less likely to have a decline in amplitude of 50 % or more from baseline in a given year than those not receiving this dosage ( P = .01 ) , while the two groups receiving 400 IU/d of vitamin E were 42 % more likely to have a decline in amplitude of 50 % or more from baseline than those not receiving this dosage ( P = .03 ) . While not statistically significant , similar trends were observed for rates of decline of visual field area . Visual acuity declined about 1 letter per year in all groups . CONCLUSIONS These results support a beneficial effect of 15,000 IU/d of vitamin A and suggest an adverse effect of 400 IU/d of vitamin E on the course of retinitis pigmentosa This pilot aims to better underst and the market for childcare in Saudi Arabia – both the supply and dem and sides – and to design a r and omized controlled experiment to test whether access to affordable day care ( in the form of subsidies , for example ) would incentivize Saudi mothers to search actively for employment and to remain employed once they are hired . In addition , the study seeks to underst and the degree to which employment early on in one ’s life impacts employment in later stages . The pilot will provide information on the groups of women the experiment should target , appropriate levels for the childcare subsidy , and the quality and current geographic locations of daycare sites . Expected Impact Determine the effects of facilitating childcare access on Saudi women ’s employment . PRINCIPAL INVESTIGATORS  Boston University Patricia Cortes  Harvard University Claudia Goldin  Swarthmore College Jennifer BACKGROUND Vitamin A supplementation is being used successfully to treat some forms of cancer and the degenerative eye disease retinitis pigmentosa . The daily biological need for vitamin A is estimated to be 800 retinol equivalents (RE)/d ( 2667 IU/d ) for adult women and 1000 RE/d ( 3300 IU/d ) for adult men ; doses > or = 7500 RE ( > or = 25000 IU)/d are considered potentially toxic over the long term . OBJECTIVE We assessed the safety in adults of long-term vitamin A supplementation with doses above the daily biological need but < 7500 RE ( < 25000 IU)/d . DESIGN Adults aged 18 - 54 y with retinitis pigmentosa but in generally good health ( n = 146 ) were supplemented with 4500 RE ( 15000 IU ) vitamin A/d for < or = 12 y ( group A ) and compared with a similar group ( n = 149 ) that received 23 RE ( 75 IU)/d ( trace group ) . Mean total consumption of vitamin A  in group A was 5583 RE ( 18609 IU)/d ( range : 4911 - 7296 RE/d , or 16369 - 24318 IU/d ) and that in the trace group was 1053 RE ( 3511 IU)/d ( range : 401 - 3192 RE/d , or 1338 - 10638 IU/d ) . RESULTS Patients in group A showed an 8 % increase in mean serum retinol concentration at 5 y and an 18 % increase at 12 y ( P < 0.001 ) ; no retinol value exceeded the upper normal limit ( 3.49 micromol/L , or 100 microg/dL ) . Mean serum retinyl esters were elevated approximately 1.7-fold at 5 y and remained relatively stable thereafter . No clinical symptoms or signs of liver toxicity attributable to vitamin A excess were detected . CONCLUSIONS Prolonged daily consumption of < 7500 RE ( < 25000 IU ) vitamin A/d can be considered safe in this age group Background There is no generally accepted medical or surgical treatment to stop the progressive course of retinitis pigmentosa . Previous studies have suggested lutein as a potential treatment with positive effects on macular pigment density . The objective of this study was to examine the effect of lutein supplementation on preservation of visual function in patients with retinitis pigmentosa ( RP ) Methods In a double-masked r and omized placebo-controlled phase I/II clinical trial with a cross-over design , 34 adult patients with RP were r and omized to two groups . One group , consisted of 16 participants , received lutein supplementation ( 10 mg/d for 12 wks followed by 30 mg/d ) for the first 24 weeks and then placebo for the following 24 weeks , while the other group included 18 participants for whom placebo ( 24 weeks ) was administered prior to lutein .  Visual acuity , contrast sensitivity , and central visual field were measured at different illumination levels at baseline and every week using a PC-based test at home . Results For visual acuity ( VA ) at normal illumination level , treatment with lutein reduced logMAR , i.e. improved VA , but this effect was not statistically significant . The changes in normal ( 100 % ) , low ( 4 % ) , and very low ( 0.1 % ) illumination log CS were not statistically significant ( p-values : 0.34 , 0.23 , and 0.32 , respectively ) . Lutein had a statistically significant effect on visual field ( p-value : 0.038 ) and this effect increased in the model assuming a 6-week delay in effect of lutein . Comparing the development of vision measures against the natural loss expected to occur over the course of 48 weeks , most measures showed reduced decline , and these reductions were significant for normal illumination VA and CS . Conclusion These results suggest that lutein supplementation improves visual field and also might improve visual acuity slightly , although these results should be interpreted cautiously . As a combined phase I and II clinical trial , this study demonstrated the efficacy and safety of lutein supplementation IMPORTANCE X-linked retinitis pigmentosa is a severe inherited retinal degenerative disease with a frequency of 1 in 100,000 persons . Because no cure is available for this orphan disease and treatment options are limited , slowing of disease progression would be a meaningful outcome . OBJECTIVE To determine whether high-dose docosahexaenoic acid ( DHA ) , an ω-3 polyunsaturated fatty acid , slows progression of X-linked retinitis pigmentosa measured by cone electroretinography ( ERG ) . DESIGN , SETTING , AND PARTICIPANTS A 4-year , single-site , r and omized , placebo-controlled , double-masked phase 2 clinical trial at a research center specializing in medical retina . Seventy-eight male patients diagnosed as having X-linked retinitis pigmentosa were r and omized to DHA or placebo . Data were omitted for 2 patients with non-X-linked retinitis pigmentosa and 16 patients who were unable to follow protocol during the first year . The remaining participants were tested annually and composed a modified intent-to-treat cohort ( DHA group , n = 33 ; placebo group , n = 27 ) . INTERVENTIONS All participants received a multivitamin and were r and omly assigned to oral DHA ( 30 mg/kg/d ) or placebo . MAIN OUTCOMES AND MEASURES The primary outcome was the rate of loss of cone ERG function . Secondary outcomes were rod and maximal ERG amplitudes and cone ERG implicit times . Capsule counts and red blood cell DHA levels were assessed to monitor adherence . RESULTS Average ( 6-month to 4-year ) red blood cell DHA levels were 4-fold higher in the DHA group than in the placebo group ( P < .001 ) . There was no difference between the DHA and placebo groups in the rate of cone ERG functional loss ( 0.028 vs 0.022 log µV/y , respectively ; P = .30 ) . No group differences were evident for change in rod ERG ( P = .27 ) , maximal ERG ( P = .65 ) , or cone implicit time ( no change over 4 years ) . The rate of cone loss ( ie , event rate ) was markedly reduced compared with rates in previous studies . No severe treatment-emergent adverse events were found . CONCLUSIONS AND RELEVANCE Long-term DHA supplementation was not effective in slowing the loss of cone or rod ERG function associated with X-linked retinitis pigmentosa . Participant dropout and lower-than-expected disease event rate limited power to detect statistical significance . A larger sample size , longer trial , and attainment of a target blood DHA level ( 13 % ) would be desirable . While DHA supplementation at 30 mg/kg/d does not present serious adverse effects , routine monitoring of gastrointestinal tolerance is prudent . TRIAL REGISTRATION clinical trials.gov Identifier : NCT00100230 Background Fundus albipunctatus is a retinal dystrophy caused by a mutation in the gene encoding 11-cis-retinol dehydrogenase which delays the recovery of rod photoreceptor cells from light stimulation leading to night blindness . A recent study of a mouse model of fundus albipunctatus treated with 9-cis-retinal showed an improvement in visual function and structure . Methods Seven patients with fundus albipunctatus were given a daily food supplement of four capsules containing high-dose 9-cis-β-carotene for 90 days . The subjects were tested before and after treatment by visual field and electroretinogram in both eyes . This non-r and omised prospect i ve phase I study was registered at http://www . clinical trials.gov ( NCT00478530 ) . Results All patients showed significant improvements in peripheral visual field ( mean deviation improved from −4.77±2.0 to −3.28±2.28 , p=0.009 , t test ) and a highly significant improvement in rod recovery rates measured electroretinographically ( maximal scotopic b-wave amplitude responses , improved from 197±49 μV to 292±48 μV , p<0.001 , t test 
    Output:
    
Different DHA doses has no effect on RP or Best disease .
No supplement showed severe adverse effects in the selected studies although strong evidence of toxicity exists for high doses of vitamin A and β-carotene in certain population s. The selected studies concluded that there may be a small beneficial effect of vitamin A , lutein and β-carotene on the progression of RP .