Ansari E A, Sahni K, Etherington C, Morton A, Conway S P, Moya E, Littlewood J M
Department of Ophthalmology, St James's and Seacroft University Hospitals, Leeds LS14 6UH.
Br J Ophthalmol. 1999 Jun;83(6):688-91. doi: 10.1136/bjo.83.6.688.
BACKGROUND/AIMS: Patients with cystic fibrosis (CF) may have low plasma vitamin A levels from malabsorption, zinc deficiency, liver disease, or poor compliance with prescribed supplements. In view of the increasing number of adults with CF, many of whom drive cars, it is important to assess vitamin A status. In our centre an attempt has been made to achieve normal levels of fat soluble vitamins by annual estimation of plasma levels and appropriate oral supplementation. This study aimed to determine if this approach prevents vitamin A deficiency and the consequent problems with dark adaptation.
The study was conducted at the regional adult and paediatric cystic fibrosis unit and the patients were recruited from there. Dark adaptation studies were conducted at the department of ophthalmology, St James's University Hospital. All patients are regularly seen in the outpatient department by a CF specialist dietitian and have a comprehensive annual dietary assessment. 28 patients had the following investigations: serum retinol, plasma zinc, serum retinol binding protein, liver function tests, dark adaptation, contrast sensitivity, and anterior ocular surface status. 25 age and sex matched controls without CF or ocular pathology were also recruited for the dark adaptation study.
None of the patients had vitamin A deficiency, the median value of serum retinol being 48 microg/dl, range 31-80 microg/dl (normal range 30-80 microg/dl). Dark adaptation was normal in all cases compared with the control group where the mean value was 3.4 log units of threshold luminance (95% confidence interval 2.4-4.0). None of the test group had a value of threshold luminance 2 SD above the mean value for the control group. Eight patients had reduced contrast sensitivity. The median value for serum zinc was 14.2 micromol/ l, range 13-81 micromol/l (normal range 8-23 micromol/l) and the median value for retinol binding protein was 36 mg/l, range 13-81 mg/l (normal range 35-58 mg/l). There was no correlation between dark adaptation and serum retinol, zinc, or retinol binding protein. Two patients had clinical evidence of dry eye.
Regular estimates of plasma vitamin A together with appropriate supplementation and expert dietetic review can maintain normal dark adaptation in patients with cystic fibrosis. The occurrence of reduced contrast sensitivity function is well documented but remains an unexplained phenomenon and deserves further study.
背景/目的：囊性纤维化（CF）患者可能因吸收不良、锌缺乏、肝脏疾病或未严格遵医嘱补充维生素而出现血浆维生素A水平降低。鉴于成年CF患者数量不断增加，其中许多人还会开车，评估维生素A水平显得尤为重要。在我们中心，已尝试通过每年测定血浆水平并进行适当的口服补充，使脂溶性维生素水平达到正常。本研究旨在确定这种方法是否能预防维生素A缺乏以及由此导致的暗适应问题。
该研究在地区成人及儿童囊性纤维化科室进行，患者从该科室招募。暗适应研究在圣詹姆斯大学医院眼科进行。所有患者均由CF专科营养师定期在门诊进行检查，并每年进行一次全面的饮食评估。28例患者接受了以下检查：血清视黄醇、血浆锌、血清视黄醇结合蛋白、肝功能检查、暗适应、对比敏感度和眼前节表面状况。还招募了25名年龄和性别匹配、无CF或眼部病变的对照者进行暗适应研究。
所有患者均无维生素A缺乏，血清视黄醇中位数为48μg/dl，范围为31 - 80μg/dl（正常范围30 - 80μg/dl）。与对照组相比，所有病例的暗适应均正常，对照组平均阈值亮度为3.4对数单位（95%置信区间2.4 - 4.0）。测试组中没有患者的阈值亮度值比对照组平均值高2个标准差。8例患者对比敏感度降低。血清锌中位数为14.2μmol/l，范围为13 - 81μmol/l（正常范围8 - 23μmol/l），视黄醇结合蛋白中位数为36mg/l，范围为13 - 81mg/l（正常范围35 - 58mg/l）。暗适应与血清视黄醇、锌或视黄醇结合蛋白之间无相关性。2例患者有干眼的临床证据。
定期测定血浆维生素A水平，同时进行适当补充和专业饮食评估，可使囊性纤维化患者维持正常的暗适应。对比敏感度功能降低的情况已有充分记录，但仍是一个无法解释的现象，值得进一步研究。
