Ocular findings in cystic fibrosis

Ocular Changes in Cystic Fibrosis: A Review

Cystic fibrosis (CF), also known as mucoviscidosis, is the most common autosomal recessive genetic disease in the Caucasian population, with an estimated frequency of 1:2000-3000 live births. CF results from the mutation of the cystic fibrosis transmembrane conductance regulator (CFTR) gene localized in the long arm of chromosome 7. The product of CFTR gene expression is CFTR protein, an adenosine triphosphate (ATP)-binding cassette (ABC) transporter that regulates the transport of chloride ions (Cl-) across the apical cell membrane. Primary manifestations of CF include chronic lung and pancreas function impairment secondary to the production of thick, sticky mucus resulting from dehydrated secretions. It is well known that CF can cause both anterior and posterior ocular abnormalities. Conjunctival and corneal xerosis and dry eye disease symptoms are the most characteristic manifestations in the anterior segment. In contrast, the most typical anatomical and functional changes relating to the posterior segment of the eye include defects in the retinal nerve fiber layer (RNFL), vascular abnormalities, and visual disturbances, such as reduced contrast sensitivity and abnormal dark adaptation. However, the complete background of ophthalmic manifestations in the course of CF has yet to be discovered. This review summarizes the current knowledge regarding ocular changes in cystic fibrosis.

Ophthalmologic manifestations of adult patients with cystic fibrosis

INTRODUCTION

Cystic fibrosis (CF) is the most common life-shortening recessive genetic disease in Caucasians, affecting primarily the lungs. The objective of our study was to investigate potential ophthalmologic involvement in adult patients with CF.

METHODS

Fifty adult patients with cystic fibrosis and 60 age- and sex-matched controls underwent complete ophthalmologic examination including tear-film Break-Up Time (BUT), Macular Thickness, and peripapillary Retinal Nerve Fiber Layer (pRNFL) thickness measurements using Spectral Domain-OCT.

RESULTS

CF patients had significantly lower nasal-inferior pRNFL thickness (median 82 IQR 67-102 vs 92.5 IQR 82-107, p = 0.005) and lower percentage of normal tear Break-Up Time (56.0% vs 96.7%, p = 0.001) than healthy controls. All CF patients with BUT <10 s were diagnosed with blepharitis at the time of our assessement. The subgroup of patients homozygous for the most common CF mutation, F508del, had lower nasal-inferior pRNFL thickness (p = 0.014) and lower percentage of normal tear Break-Up Time (p = 0.001) compared to the control group. Additional findings, present in the CF group only, were punctuate retinal hemorrhages (four patients), vessel tortuosity (four patients), snail-track degeneration, and retinal tufts (two patients without refractive error). There were no significant differences in visual acuity, refractive errors, gonioscopic findings, or intraocular pressure between the groups.

CONCLUSIONS

Our study is, to the best of our knowledge, the largest ophthalmologic study of patients with cystic fibrosis. We found that CF patients had significantly decreased inferior-quadrant peripapillary retinal nerve fiber layer thickness and decreased tear-film break-up time compared to controls. We highlight the importance of careful regular ophthalmologic assessment and follow-up of these patients.

Acute retinal vein occlusion and cystic fibrosis

Background

The ocular manifestations of cystic fibrosis typically present with surface irritation or nyctalopia due to Vitamin A deficiency, however, there have been two previous reports of patients with cystic fibrosis that developed retinal vein occlusions. These reports hypothesized that either elevated fibrinogen levels due to chronic infections or elevated homocysteine levels have predisposed patients with cystic fibrosis to develop retinal vein occlusions.

Case presentation

We present a case of a 35-year-old male with cystic fibrosis complicated by chronic sinusitis with no history of organ transplantation or chronic pulmonary infections who presented with an acute branch retinal vein occlusion in his left eye with associated macular edema. Evaluation revealed an elevated fibrinogen level, while the rest of his workup was relatively unremarkable including a normal homocysteine level. His vision remained 20/20 throughout his care and he did not require treatment of his macular edema.

Conclusions

Patients with cystic fibrosis are at an increased risk of developing retinal vein occlusions likely due to a variety of systemic thrombogenic factors rather than a single risk factor which had been reported previously. Elevated fibrinogen levels in these patients may not be due to chronic infections, but inherent to the cystic fibrosis.

Diabetes: a major co-morbidity of cystic fibrosis

Cystic fibrosis-related diabetes (CFRD) is a frequent complication of cystic fibrosis, its prevalence increases with age of patient and is close to 30% at the age of 30 years. As life expectancy greatly increases, the number of cystic fibrosis patients developing diabetes will increase too. CFRD shares some features with type 1 and type 2 diabetes, initial phase is characterised by postprandial hyperglycaemia followed by a progression toward insulin deficiency. Insulin deficiency is an essential factor in the development of diabetes with an additional contribution of insulin resistance. Systematic screening with an oral glucose tolerance test is recommended from the age of 14 years because clinical signs of CFRD are often confused with signs of pulmonary infection and CFRD occurrence is associated with weight and pulmonary function deterioration. In observational studies CFRD diagnosis is associated with a significant increase in mortality, while treatment allow correction of weight and lung deterioration suggesting that CFRD has a significant impact on CF evolution. Microvascular complications are recognised, although paucity of data does not permit a clear description of their natural history. Annual screening for microvascular complication is recommended. There is no evidence by now that CF patients develop macrovascular complications. The only recommended pharmacological treatment is insulin therapy.

Lutein, zeaxanthin, macular pigment, and visual function in adult cystic fibrosis patients

BACKGROUND

Pancreatic insufficiency in cystic fibrosis (CF), even with replacement pancreatic enzyme therapy, is often associated with decreased carotenoid absorption. Because the macular pigment of the retina is largely derived from 2 carotenoids, lutein and zeaxanthin, the decreased serum concentrations seen in CF may have consequences for ocular and retinal health

OBJECTIVES

Our aims were to determine plasma carotenoid concentrations, determine absorption and distribution of macular pigment, and assess retinal health and visual function in CF patients.

DESIGN

In 10 adult CF patients (ages 21-47 y) and 10 age- and sex-matched healthy control subjects, we measured macular pigment density in vivo, measured serum lutein and zeaxanthin concentrations, and comprehensively assessed visual performance (including contrast sensitivity, color discrimination, and retinal function) under conditions of daylight illumination.

RESULTS

Serum lutein and zeaxanthin were significantly reduced (P < 0.005) in CF patients ( +/- SD: 87 +/- 36.1 and 27 +/- 15.8 nmol/L, respectively) compared with control subjects (190 +/- 72.1 and 75 +/- 23.6 nmol/L, respectively). Although macular pigment optical density was significantly lower (P < 0.0001) in the CF group (0.24 +/- 0.11) than in the control group (0.53 +/- 0.12), no significant differences in visual function were observed.

CONCLUSIONS

Adults with CF have dramatically low serum and macular concentrations of carotenoids (lutein and zeaxanthin), but their ocular status and visual function are surprisingly good. The clinical implications of low plasma concentrations of carotenoids in CF are yet to be clarified.

The eye in cystic fibrosis

PURPOSE

To investigate modifications of ocular surface and lens transparency in patients with cystic fibrosis in relation to the stage of digestive insufficiency.

METHODS

Forty consecutive patients with cystic fibrosis and 24 age- and sex-matched healthy volunteers were examined. The tear tests (Schirmer's basic test, tear film break-up time) and conjunctival exfoliative cytology (CC) were used to study the ocular surface. The lens transparency was measured with the Opacity Lens Meter 701 (OLM 701, Interzeag AG, Switzerland). Digestive insufficiency was evaluated by the steatocrit method.

RESULTS

Significant changes in conjunctival cytology and lens opacity, and abnormal tear tests were detected in CF patients; the alterations were more pronounced in patients with severe digestive insufficiency.

CONCLUSIONS

Cystic fibrosis patients present ocular surface abnormalities and lens transparency modifications and their severity is related to the digestive insufficiency. Simple, rapid and non-invasive tear tests and cytological procedures might be used as additional tests for assessing the severity of cystic fibrosis.

Ocular signs and symptoms and vitamin A status in patients with cystic fibrosis treated with daily vitamin A supplements

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Ocular findings in cystic fibrosis patients receiving vitamin A supplementation

BACKGROUND

Vitamin A deficiency with eye symptoms has been reported in patients with cystic fibrosis who received the recommended daily intake of vitamin A.

METHODS

We measured serum retinol, dark adaptation, contrast sensitivity, and dry eye status in 35 adult cystic fibrosis patients to ascertain whether they had ocular signs or symptoms.

RESULTS

Median serum retinol concentration was 1.95 mumol/l, range 1.08-4.01 mumol/l, with no values indicating vitamin A deficiency. Retinal light sensitivity was normal. Nineteen patients had reduced contrast sensitivity. Conjunctival imprints all showed plenty of goblet cells, but were characteristic of dry eye in 42% of patients (n = 14). Decreased tear film stability was found in 49% (n = 17), tear production was low in 31% (n = 11), and 23% (n = 8) showed an increased amount of dying epithelial cells. Nine patients (26%) had keratoconjunctivitis sicca according to the Copenhagen criteria.

CONCLUSION

Our patients had no biochemical or clinical signs of vitamin A deficiency. We speculate that the high incidence of dry eye could be a primary manifestation of cystic fibrosis.

A multicenter study of alternate-day prednisone therapy in patients with cystic fibrosis. Cystic Fibrosis Foundation Prednisone Trial Group

The purpose of this study was to evaluate the efficacy and safety of alternate-day prednisone therapy in treating patients with mild-to-moderate cystic fibrosis during a 4-year period. In 15 North American cystic fibrosis centers, we screened 320 patients and enrolled 285 patients from April 1986 to December 1987. Patients were randomly assigned to take prednisone, 1 mg/kg per dose or 2 mg/kg per dose, or a matching placebo given on alternate days. Lung function, clinical status, hospitalizations, growth, and steroid side effects were monitored. During the first 24 months the percentage of the predicted forced vital capacity was greater in the 1 mg/kg group (p < 0.0001) and the 2 mg/kg group (p < 0.01) when each was compared with placebo. Patients in the 1 mg/kg group had a higher percentage of predicted forced vital capacity than placebo patients during the entire 48 months (p < 0.0025), but only in the group of patients who were colonized with Pseudomonas aeruginosa at baseline. For 48 months, the 1 mg/kg group had a higher percentage of predicted forced expiratory volume in 1 second than patients given placebo (p < 0.02). The prednisone-treated groups had a reduction in serum IgG concentrations (1 mg/kg vs placebo, p < 0.007; 2 mg/kg vs placebo, p < 0.003). From 6 months onward, height z scores fell in the 2 mg/kg group compared with those given placebo (p < 0.001). For the 1 mg/kg group, height z scores were lower from 24 months. An excess of abnormalities in glucose metabolism was seen in the 2 mg/kg group compared with the placebo group (p < 0.005). Our findings suggest a role for alternate-day prednisone therapy at a dose of 1 mg/kg in patients with mild to moderate cystic fibrosis. The benefit of improved lung function appears to outweigh the potential for adverse effects when the treatment period is less than 24 months.

Insulin sensitivity and metabolic clearance rate of insulin in cystic fibrosis

We have evaluated the metabolic clearance rate (MCR) of insulin and insulin sensitivity in 12 older patients with cystic fibrosis (CF) using the hyperinsulinemic euglycemic clamp method. Compared with a control group matched accurately for age and body mass index (BMI), the MCR of insulin was significantly enhanced in CF CF = 21.85 +/- 1.17 v controls = 16.01 +/- 0.92 mL/kg/min, P < .005), and this difference persisted after correction for lean body mass ([LBM] CF = 26.32 +/- 1.28 v controls = 19.09 +/- 1.09 mL/kg LBM/min, P < .005). Glucose disposal rates (M) were similar in the two groups during the clamp (CF = 7.28 +/- 0.41 v controls = 6.83 +/- 0.60 mg/kg/min, P > .5), but the insulin sensitivity index, M/I x 100 (I = steady-state insulin concentration), was markedly increased in the CF group (CF = 17.62 +/- 1.30 v controls = 11.75 +/- 0.71, P < .005). In conclusion, the MCR of insulin is enhanced in CF, which is in keeping with previous observations on drug metabolism in this disorder. Second, insulin sensitivity is increased in CF, and this points to a compensatory mechanism to counteract the insulinopenia.

Loss of contrast sensitivity in cystic fibrosis

We measured the contrast sensitivity function in a 16-year-old boy with cystic fibrosis, before and during vitamin A supplementation. Before vitamin A supplementation, serum levels of vitamin A were abnormally low, the electroretinogram was reduced, and contrast sensitivity was abnormally low at all spatial frequencies. During vitamin A supplementation (25,000 IU/day), serum levels of vitamin A became low normal, the electroretinogram returned to normal, and the overall contrast sensitivity function improved by 94%. We propose that the contrast sensitivity function may be abnormal in patients with cystic fibrosis who have reduced retinal function secondary to vitamin A deficiency.

Risk factors for the development of posterior subcapsular cataracts in patients with cystic fibrosis and allergic bronchopulmonary aspergillosis treated with corticosteroids

Posterior subcapsular cataracts (PSCC) occur in a high percentage of patients treated with long-term systemic corticosteroids (Naumann Gott, Apple DJ, eds: Pathology of the Eye. New York: Springer-Verlag, 1986). Fifteen patients with cystic fibrosis treated at Duke University Medical Center between January 1982 and October 1987 required prednisone for treatment of allergic bronchopulmonary aspergillosis (ABPA). Two of these patients (13.3%) were noted to have PSCC during prednisone therapy. We retrospectively examined factors associated with steroid administration that may have been predictive of the development of PSCC in these patients including: 1) steroid therapy for longer than 2 years, 2) steroid dose of 10 mg/day or greater for longer than 6 months, 3) steroid dose of 40 mg/day or greater for longer than 2 months, and 4) change in linear growth pattern during steroid therapy. None of these factors predicted the risk of developing PSCC. Therefore, we recommend that all patients with cystic fibrosis who receive steroids for the treatment of a concomitant condition such as ABPA should undergo careful examination for opacities of the ocular lens at each clinical visit regardless of the duration or dose of steroids.