Cystic fibrosis and new trends by ophthalmological evaluation: a pilot study

The role of CFTR in the eye, and the effect of early highly effective modulator treatment for cystic fibrosis on eye health

Cystic fibrosis transmembrane conductance regulator (CFTR) is a protein that plays a crucial role in various human organs, including the respiratory and digestive systems. Dysfunctional CFTR is the key variant of the lethal genetic disorder, cystic fibrosis (CF). In the past decade, highly effective CFTR modulator therapies, including elexacaftor-tezacaftor-ivacaftor, have revolutionised CF management by correcting the underlying molecular defect to improve patient outcomes and life expectancy. Despite demonstrating multiorgan efficacy, clinical studies have largely overlooked the potential for ocular disturbances with CFTR modulator therapy, with the exception of a few case studies reporting the presence of crystalline lens pathologies in young children on CFTR modulators, and in breastfed infants born to individuals who were on CFTR modulator treatment during pregnancy. CFTR is present in multiple tissues during embryonic development, including the eye, and its expression can be influenced by genetic and environmental factors. This review summarises the role of CFTR in the eye, and the potential impact of CFTR on eye function and vision later in life. This information provides a framework for understanding the use and possible effects of CFTR-modulating therapeutics in the context of eye health, including the potential to leverage the eye for non-invasive and accessible diagnostic and monitoring capabilities in patients with CF.

Glycemic Variability and the Thickness of Retinal Layers in Cystic Fibrosis Patients with and without Cystic Fibrosis Related Diabetes

PURPOSE

Patients with cystic fibrosis (CF) are at risk to develop CF related diabetes (CFRD) and subsequently even diabetic neuro- and/or vasculopathy. We sought to determine if there are typical signs of diabetes-related retinal alterations present in CF patients with preserved and impaired glycemic control.

METHODS

During routine annual examination CF patients were offered an additional 7-day period of real time continuous glucose monitoring (rtCGM) and an ophthalmological examination including retinal optical coherence tomography (OCT). Patients were categorized according to the glycemic control, i.e. the results of an oral glucose tolerance test (OGTT) and rtCGM were taken into consideration. OCT data was analyzed by our previously published visual analysis software generating dedicated and spatially resolved deviation maps for visualization and quantification of differences in total retinal thickness and thickness of retinal nerve fiber layer (RNFL) as well as ganglion cell layer (GCL) in comparison to age-matched healthy controls and patients with either type 1 or type 2 diabetes mellitus.

RESULTS

Results of the rtCGM and/or OGTT enabled discrimination between patients with normal glycemic control (CFNG; n = 6), with abnormal glycemic control (CFAG; n = 6) and overt CFRD (n = 4). OCT data indicates gradually increasing retinal thinning in all 3 groups, depending on the degree of glucose metabolism disorder compared to healthy controls. At the foveal region total retinal thickness and GCL thickness were significantly thinner in CFRD patients compared to CFNG patients (total retinal thickness: 260.4 µm (239.3-270.8) vs. 275.4 µm (254.3-289.5); GCL: 11.82 µm (11.16-15.25) vs. 17.30 µm (13.95-19.82); each p < 0.05).

CONCLUSION

Although we investigated a rather small number of patients, we obtained evidence that intraretinal neurodegenerative changes occur in each of our subgroups (CFNG, CFAG, CFRD). Beyond this, our results favor the detrimental role of additional diabetes, as the deviations from healthy controls were most pronounced in the CFRD group and are similar to those seen in patients suffering from type 1 or type 2 diabetes.

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.

The pathological association between the anterior eye segment and the retina in a murine model of neovascular glaucoma

Neovascular glaucoma (NVG) is caused by the formation of new blood vessels in the angle, iris, and cornea in retinal ischemic disease, such as proliferative diabetic retinopathy (PDR) and retinal vein occlusion (RVO), which can reduce the visual acuity. However, the pathophysiological symptoms of NVG are still not well understood because there is no model for the formation of NVG in the angle, iris, and cornea. The aim of this study was to investigate the involvement of NVG during ischemic disease, in a murine model of retinal ischemia. We evaluated the changes of the intraocular pressure (IOP) and pathological symptoms in the anterior eye segment and retina in this model, and the changes in the RNA or protein expression of vascular endothelial growth factor (VEGF) and fibrosis-related factors were analyzed in the retina and cornea by quantitative real-time polymerase chain reaction or western blot, respectively. Furthermore, we examined the changes in IOP after intravitreal injection of an anti-VEGF antibody. First, NVG formed in the retinal ischemic murine model, and the IOP was elevated in mice with NVG formation. Interestingly, VEGF expression was decreased in the retina but increased in the cornea in the murine model of NVG. On the other hand, fibrosis-related factors were increased in the retina and also significantly increased in the cornea in NVG. Moreover, the administration of anti-VEGF antibody immediately after vessel occlusion suppressed the increase in IOP, but administration at 7 days after vessel occlusion accelerated the increase in IOP. These findings suggest that the formation of NVG may be correlated with the pathological symptoms of retinal ischemic disease, via changes in VEGF and fibrosis-related factor expression.

Advantages and Disadvantages of Using Magnetic Nanoparticles for the Treatment of Complicated Ocular Disorders

Nanomaterials provide enormous opportunities to overcome the limitations of conventional ocular delivery systems, such as low therapeutic efficacy, side effects due to the systemic exposure, or invasive surgery. Apart from the more common ocular disorders, there are some genetic diseases, such as cystic fibrosis, that develop ocular disorders as secondary effects as long as the disease progresses. These patients are more difficult to be pharmacologically treated using conventional drug routes (topically, systemic), since specific pharmacological formulations can be incompatible, display increased toxicity, or their therapeutic efficacy decreases with the administration of different kind of chemical molecules. Magnetic nanoparticles can be used as potent drug carriers and magnetic hyperthermia agents due to their response to an external magnetic field. Drugs can be concentrated in the target point, limiting the damage to other tissues. The other advantage of these magnetic nanoparticles is that they can act as magnetic resonance imaging agents, allowing the detection of the exact location of the disease. However, there are some drawbacks related to their use in drug delivery, such as the limitation to maintain efficacy in the target organ once the magnetic field is removed from outside. Another disadvantage is the difficulty in maintaining the therapeutic action in three dimensions inside the human body. This review summarizes all the application possibilities related to magnetic nanoparticles in ocular diseases.

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.

Correlation between optic nerve involvement and chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a major public health problem worldwide. The aim of this study was to evaluate the rate of optic neuropathy in COPD patients.

METHODS

Forty patients diagnosed with COPD and 60 healthy subjects as control group enrolled. After examination by a pulmonary subspecialist, patients were ranked by Global initiative for chronic Obstructive Lung Disease (GOLD) criteria, and patients with zero grades on GOLD criteria were excluded. Visual evoked potential by checkerboard (raster background) method with a frequency of 2 Hz were done for all participants. P-values less than 0.05 were considered as significant.

RESULTS

Fifty-five percent of COPD patients had visual evoked potential abnormalities. Mean P100 latency in both eyes was significantly longer in COPD patients. Average P100/N140 amplitude in both eyes were insignificantly higher in COPD.

CONCLUSION

Higher P100 latency in COPD patients shows demyelinating type of optic nerve involvement; however, further investigation in this area is needed.