Clinical Practice: A Proposed Standardized Ophthalmological Assessment for Patients with Cystinosis

Typical Manifestations of the Different Corneal Deposits by In Vivo Confocal Microscopy (IVCM): A Review

In vivo confocal microscopy (IVCM) is a highly useful tool in ophthalmology for investigating a wide range of corneal pathologies. It provides high resolution images with minimal light scattering and is particularly useful in determining the nature of various corneal deposits. Deposits may arise within any layer of the cornea and may occur due to various reasons such as infections (e.g., crystalline deposits), metabolic bodily processes, systemic diseases, pharmacological agents and toxins. Deposits may as a general rule, be linear versus non-linear in shape or hyperreflective or hyporeflective in nature. Non-linear deposits can further be subdivided into granular, round, amorphous, or whorl-like patterns of deposits. This article will attempt to not only summarise all of the currently recognised corneal deposits but also utilise the morphology of the varying types of corneal deposits as seen in IVCM and categorise them within a table.

Ocular Cystinosis Experience in Southwestern Ontario

PURPOSE

To evaluate ocular treatment adherence and its impact on clinical outcomes in patients with cystinosis in southwestern Ontario, where the disease incidence is higher due to a founder effect in the Old Order Amish population.

METHODS

This was a retrospective case series of patients with ocular cystinosis seen at Victoria Hospital and the Ivey Eye Institute at St Joseph's Health Care in London, Ontario, Canada, from 2008 to 2023. The authors investigated the demographics, ocular manifestations, and visual outcomes and characteristics in pediatric patients with ocular cystinosis. They also conducted qualitative analysis to characterize medication compliance and identify treatment barriers to compliance.

RESULTS

This study included 14 patients with ocular cystinosis. In southwestern Ontario, the incidence of cystinosis is approximately 1 in 4,700 live births. Most patients were Old Order Amish, with a family history of cystinosis and consanguineous parents. During treatment, patients were typically asymptomatic, but photophobia was the most reported symptom. Slit-lamp examination revealed cystine crystals in the cornea of all patients; however, best corrected visual acuity and intraocular pressure were unremarkable in every case. A Fisher's exact test revealed a trend toward lower compliance in Amish patients compared to non-Amish patients (odds ratio: 0.067, P = .103). Significant treatment barriers for patients with ocular cystinosis were identified, including compliance issues with frequent eye drop regimens, educational and financial burdens, and geographical and cultural challenges, all impacting patient care and follow-up.

CONCLUSIONS

This study highlights the need for improved strategies to improve treatment compliance and overcome barriers to care for patients with ocular cystinosis, particularly within the Old Order Amish population in southwestern Ontario, to ensure better clinical outcomes and quality of life. [J Pediatr Ophthalmol Strabismus. 2025;62(2):105-115.].

Theranostic Contact Lens for Ocular Cystinosis Utilizing Gold Nanoparticles

Ocular cystinosis is a disease in which accumulated cystine crystals cause damage to the eyes, necessitating timely treatment and ongoing monitoring of cystine levels. The current treatment involves frequent administration of cysteamine eye drops, which suffer from low bioavailability and can lead to drug toxicity, making it essential to prescribe an appropriate dosage based on the patient's condition. Additionally, cystine crystal levels are typically assessed subjectively via slit-lamp examination, requiring frequent clinical visits and causing discomfort for the patient. In this study, we propose a theranostic contact lens that simultaneously performs therapy and diagnosis on a single platform utilizing gold nanoparticles (GNPs). The binding interactions between GNPs and cystine were confirmed in solution, and thermodynamic analysis further elucidated the bonding force between the two substances. With a comprehensive understanding of these interactions, we investigated the potential of the theranostic GNP-loaded contact lens (GNP-CL). Upon exposure to various concentrations of cystine, the GNP-CL demonstrated distinct color changes, transitioning from red to blue. This color shift enabled quantitative monitoring of cystine levels. The treatment efficacy was validated by confirming a reduction in cystine concentration following the reaction. This platform has the potential to improve disease management in ocular cystinosis by reducing the reliance on cysteamine and offering an objective self-monitoring tool that does not require specialized equipment.

Development and Evaluation of Different Electrospun Cysteamine-Loaded Nanofibrous Webs: A Promising Option for Treating a Rare Lysosomal Storage Disorder

Nanofibers can be utilized to overcome the challenges faced by conventional ophthalmic formulations. This study aimed to develop and characterize cysteamine (Cys)-loaded nanofiber-based ophthalmic inserts (OIs) as a potential candidate for the treatment of ophthalmic cystinosis using water-soluble polyvinyl alcohol (PVA)/poloxamer 407 (PO-407) and water-insoluble tetraethoxysilane (TEOS)/PVA nanofibers. Plain and Cys-loaded fibers in different proportions were prepared by the electrospinning method and studied for their morphological, physicochemical, release study, cytocompatibility effects, and stability study. The fiber formation was confirmed by scanning electron microscopy, while Fourier transform infrared spectra showed the most critical peaks for the Cys and the excipients. The release of the Cys was fast from the two polymeric matrices (≤20 min). The release from TEOS/PVA nanofibers is characterized by Case II transport (0.75 < β < 1), while the release from PVA/PO-407 nanofibers follows Fickian diffusion (β < 0.75). The cytocompatibility of compositions was confirmed by hen eggs tested on the chorioallantoic membrane (HET-CAM) of chick embryos. All formulations remained stable under stress conditions (40 ± 2 °C, 75 ± 5% relative humidity) regarding morphology and physicochemical characteristics. The developed nanofibrous mats could be an excellent alternative to available Cys drops, with better stability and convenience of self-administration as OIs.

Comparison of Scheimpflug Corneal Tomography and Anterior Segment Optical Coherence Tomography Measurements in Corneal Cystinosis: A Case Series

PURPOSE

To report the clinical course and compare the utility of Scheimpflug tomography (ST) and anterior segment optical coherence tomography (AS-OCT) for central corneal thickness (CCT) and corneal densitometry (CD) assessment in patients with corneal crystals owing to nephropathic cystinosis.

METHODS

A retrospective chart analysis of three patients with nephropathic cystinosis and the presence of corneal cystine crystals in both eyes was performed. All patients underwent clinical examination and anterior segment photography, ST, and AS-OCT scans. Corneal densitometry was exported from built-in proprietary software for ST and from custom-made validated software for AS-OCT. Anterior segment optical coherence tomography images were rescaled to grayscale units from 0 (maximum transparency) to 100 (minimum transparency) to match built-in ST densitometry readings. Furthermore, the mean pixel intensity, representative of CD, was calculated from the pixels corresponding to the segmented cornea.

RESULTS

All three patients had pathognomonic cystine crystals deposits in the cornea and were treated with cysteamine medications that resulted in clinical improvement. The CCT measured using ST exhibited a range from 560 to 958 μm. Conversely, when assessed with AS-OCT, the CCT varied within the range of 548 to 610 μm. Both examinations could be performed, but in the more severe cases, AS-OCT showed far greater utility to estimate CD. In four of six eyes examined, ST showed disproportionate CCT values, compared with the AS-OCT, whereas reliable CD measurements were only available in AS-OCT.

CONCLUSION

The AS-OCT could be considered a baseline ocular measurement in cystinosis and in the evaluation of disease progression and treatment efficacy.

A Comparative Pharmacokinetic Study for Cysteamine-Containing Eye Drops as an Orphan Topical Therapy in Cystinosis

Cystinosis is a low-prevalence lysosomal storage disease. The pathomechanism involves abnormal functioning of the cystinosine lysosomal cystine transporter (CTNS), causing intraliposomal accumulation of the amino acid cysteine disulfide, which crystallizes and deposits in several parts of the body. The most common ophthalmic complication of cystinosis is the deposition of "gold dust" cystine crystals on the cornea, which already occurs in infancy and leads to severe photosensitivity and dry eyes as it gradually progresses with age. In the specific treatment of cystinosis, preparations containing cysteamine (CYA) are used. The availability of commercialized eyedrops for the targeted treatment is scarce, and only Cystadrops® are commercially available with strong limitations. Thus, magistral CYA-containing compounded eyedrops (CYA-CED) could have a key role in patient care; however, a rationally designed comprehensive study on the commercialized and magistral products is still missing. This work aims to build up a comprehensive study about commercialized and magistral CYA eye drops, involving pharmacokinetic and physicochemical characterization (applying mucoadhesivity, rheology test, investigation of drug release, and parallel artificial membrane permeability assays), as well as ex vivo tests, well supported by statistical analysis.

Event-related potential (ERP) evidence for visual processing differences in children and adults with cystinosis (CTNS gene mutations)

BACKGROUND

Cystinosis, a rare lysosomal storage disease caused by mutations in the CTNS gene, is characterized by cystine crystallization and accumulation within multiple tissues, including kidney and brain. Its impact on neural function appears mild relative to its effects on other organs during early disease, but since therapeutic advances have led to substantially increased life expectancy, neurological implications are of increasing interest, necessitating deeper understanding of the impact of cystinosis on neurocognitive function. Behavioral difficulties have been reported in cystinosis in the visual domain. Very little is known, however, about how the brains of people living with cystinosis process visual information. This is especially interesting given that cystine accumulation in the cornea and posterior ocular structures is a hallmark of cystinosis.

METHODS

Here, high-density scalp electrophysiology was recorded to visual stimuli (during a Go/No-Go task) to investigate visual processing in individuals with cystinosis, compared to age-matched controls. Analyses focused on early stages of cortical visual processing.

RESULTS

The groups differed in their initial cortical response, with individuals with cystinosis exhibiting a significantly larger visual evoked potential (VEP) in the 130-150 ms time window. The groups also differed in the associations between neural responses and verbal abilities: While controls with higher IQ scores presented larger neural responses, that relationship was not observed in cystinosis.

CONCLUSIONS

The enlarged VEP in cystinosis could be the result of cortical hyperexcitability and/or differences in attentional engagement and explain, at least partially, the visual and visual-spatial difficulties described in this population.

Development of Innovative Electrospun Nepafenac-Loaded Nanofibers-based Ophthalmic Inserts

Electrospun nanofibers can be utilized to develop patient-centric ophthalmic formulations with reasonable bioavailability at the targeted site. The current study aimed to develop 0.1% w/w of nepafenac-loaded electrospun nanofibrous webs as potential candidates for ocular delivery of nepafenac with improved solubility and stability. Nine different formulations were prepared by electrospinning and investigated for morphology, physicochemical properties, drug release, cytocompatibility, and in vitro and ex vivo permeability. The scanning electron microscopy images showed fibrous samples. Fourier transform infrared spectroscopy and X-ray diffraction confirmed the polymer cross-linking and the formation of amorphous solid dispersion. All formulations showed complete and fast release of nepafenac (≤ 60 minutes), and the release followed first-order kinetics (β values for all formulations were <1). The formulations (F3, F6, and F9) showed considerable in vitro and ex vivo permeability. The Raman studies revealed comparable corneal distributions of F3 and the commercial Nevanac® suspension at 60 min (p value = 0.6433). The fibrous composition remains stable under stress conditions (40 ± 2 °C, 75 ± 5% relative humidity). The formulation composition showed good cytocompatibility with hen eggs tested on the chorioallantoic membrane of chick embryos. The developed nanofiber webs could be a promising candidate for nepafenac-loaded ophthalmic inserts. Chemical compounds studied in this article Nepafenac (PubChem CID151075); Polyvinyl alcohol (PubChem CID 11199); Poloxamer 407 (PubChem CID 24751); Chloroform (PubChem CID 6212); Methanol (PubChem CID 887); L-α-phosphatidylcholine (PubChem CID 10425706); Ethylenediaminetetraacetic acid (PubChem CID 6049).

Event-related potential (ERP) evidence for early visual processing differences in children and adults with Cystinosis (CTNS gene mutations)

Background

Cystinosis, a rare lysosomal storage disease caused by mutations in the CTNS gene, is characterized by cystine crystallization and accumulation within multiple tissues, including kidney and brain. Its impact on neural function appears mild relative to its effects on other organs during early disease, but since therapeutic advances have led to substantially increased life expectancy, neurological implications are of increasing interest, necessitating deeper understanding of the impact of cystinosis on neurocognitive function. Behavioral difficulties have been reported in cystinosis in the visual domain. Very little is known, however, about how the brains of people living with cystinosis process visual information. This is especially interesting given that cystine accumulation in the cornea and posterior ocular structures is a hallmark of cystinosis.

Methods

Here, high-density scalp electrophysiology was recorded to visual stimuli (during a Go/No-Go task) to investigate early visual processing in individuals with cystinosis, compared to age-matched controls. Analyses focused on early stages of cortical visual processing.

Results

The groups differed in their initial cortical response, with individuals with cystinosis exhibiting a significantly larger visual evoked potential (VEP) in the 130-150 ms time window. The groups also differed in the associations between neural responses and verbal abilities: While controls with higher IQ scores presented larger neural responses, that relationship was not observed in cystinosis.

Conclusions

The enlarged VEP in cystinosis could be the result of cortical hyperexcitability and/or differences in attentional engagement and explain, at least partially, the visual and visual-spatial difficulties described in this population.

The gene therapy for corneal pathology with novel nonsense cystinosis mouse lines created by CRISPR Gene Editing

PURPOSE

Cystinosis is an autosomal recessive lysosomal storage disease (LSDs) caused by mutations in the gene encoding cystinosin (CTNS) that leads to cystine crystal accumulation in the lysosome that compromises cellular functions resulting in tissue damage and organ failure, especially in kidneys and eyes. However, the underlying molecular mechanism of its pathogenesis remains elusive. Two novel mice lines created via CRISPR are used to examine the pathogenesis of cystinosis in the kidney and cornea and the treatment efficacy of corneal pathology using self-complimentary Adeno-associated viral (scAAV-CTNS) vector.

METHODS

The CRISPR technique generated two novel cystinotic mouse lines, Ctnsis1 (an insertional mutation) and Ctnsis2 (a nonsense mutation). Immune histochemistry, renal functions test and HRT2 in vivo confocal microscopy were used to evaluate the age-related renal pathogenesis and treatment efficacy of the scAAV-CTNS virus in corneal pathology.

RESULTS

Both mutations lead to the production of truncated Ctns proteins. Ctnsis1 and Ctnsis 2 mice exhibit the characteristic of cystinotic corneal crystal phenotype at four-week-old. Treatment with the scAAV-CTNS viral vector decreased the corneal crystals in the treated mice cornea. Ctnsis 1 show renal abnormalities manifested by increased urine volume, reduced urine osmolality, and the loss of response to Desmopressin (dDAVP) at 22-month-old but Ctnsis2 don't manifest renal pathology up to 2 years of age.

CONCLUSIONS

Both Ctnsis1 and Ctnsis2 mice exhibit phenotypes resembling human intermediate nephropathic and ocular cystinosis, respectively. scAAV-CTNS viral vectors reduce the corneal cystine crystals and have a great potential as a therapeutic strategy for treating patients suffering from cystinosis.

Event-related potential (ERP) evidence of early visual processing differences in cystinosis

Cystinosis, a rare lysosomal storage disease, is characterized by cystine crystallization and accumulation within tissues and organs, including the kidneys and brain. Its impact on neural function appears mild relative to its effects on other organs, but therapeutic advances have led to substantially increased life expectancy, necessitating deeper understanding of its impact on neurocognitive function. Behavioral difficulties have been reported in cystinosis in the visual and visual-processing domain. Very little is known, however, about how the brains of people living with cystinosis process visual information, although cysteamine accumulation in the retina is a prominent feature of cystinosis. Here, electrophysiology was recorded during a Go/No-Go task to investigate early visual processing in cystinosis, compared to an age-matched control group. Analyses focused on early stages of cortical visual processing. The groups differed in their initial cortical response, with individuals with cystinosis exhibiting a significantly larger visual evoked potential (VEP) in the 130 to 150 ms time window. The timing and topography of this response suggested an enhanced P1 in cystinosis that could be the result of cortical hyperexcitability and/or differences in attentional engagement and explain, at least partially, the visual and visual-spatial difficulties described in this population. The groups also differed in the associations between neural responses and verbal abilities: While controls with higher IQ scores presented larger neural responses, that relationship was not observed in cystinosis.

Corneal Densitometry to Assess the Corneal Cystine Deposits in Patients With Cystinosis

PURPOSE

The purpose of this study was to assess the suitability of corneal densitometry measurements obtained with Scheimpflug imaging in estimating the corneal changes caused by cystine deposits in the cornea in patients with cystinosis.

METHODS

Scheimpflug imaging (Pentacam) was performed for 14 patients with cystinosis and 16 age-matched controls. Pentacam data were used for analysis of the corneal densitometry at different zones in the cornea for patients with cystinosis and controls. Densitometry measurements were compared with the corneal crystal scores obtained from the slitlamp images for patients with cystinosis.

RESULTS

There was no statistically significant difference in keratometry measurements between the 2 groups ( P > 0.05). Corneal thickness was found to be significantly higher in the control group when compared with the cystinosis group ( P = 0.0004). The mean corneal densitometry was significantly higher in patients with cystinosis when compared with controls at most of the corneal layers and zones. The corneal densitometry readings for the right and left eyes showed moderate positive correlation with the corneal crystal score with a ceiling effect being reached at the maximum corneal crystal score of 3.

CONCLUSIONS

Corneal densitometry obtained through Pentacam can be used as an objective estimate of the level of cystine crystals present in patients with cystinosis. The clinical estimate of corneal crystal score, although effective at low levels of crystal deposition, does not allow for accurate estimates of change when the level of crystal deposition is high leading to limited utility when assessing treatment effects. Hence, densitometry measurements can potentially be used to assess treatment efficacy of cystinosis treatments in clinical settings.

Patients With Infantile Nephropathic Cystinosis in Germany and Austria: A Retrospective Cohort Study

Background

Infantile nephropathic cystinosis (INC) is a rare lysosomal storage disorder resulting in progressive chronic kidney disease (CKD) and a variety of extrarenal manifestations. This orphan disease remains a challenge for patients, their families and health care providers. There is currently no comprehensive study on patients' clinical course in Germany and Austria.

Methods

A retrospective cohort study including 74 patients at eleven centers of care was conducted. Data on time of diagnosis, CKD stage, leukocyte cystine levels (LCL), extrarenal manifestations, and treatment was collected from medical charts and subsequently analyzed using explorative statistics. Age at initiation of kidney replacement therapy (KRT) was evaluated by Kaplan-Meier analyses for different groups of patients.

Results

Patients were diagnosed at a median age of 15 months (IQR: 10-29, range: 0-110), more recent year of birth was not associated with earlier diagnosis. Oral cystine-depleting therapy (i.e., cysteamine) was prescribed at a median dose of 1.26 g/m² per day (IQR: 1.03-1.48, range: 0.22-1.99). 69.2% of all 198 LCL measurements of 67 patients were within the desired target range (≤ 1 nmol cystine/mg protein). Median time-averaged LCLs per patient (n = 65) amounted to 0.57 nmol cystine/mg protein (IQR: 0.33-0.98, range: 0.07-3.13) when considering only values at least 1 year after initiation of therapy. The overall median height of 242 measurements of 68 patients was at the 7^th percentile (IQR: 1-25, range: 1-99). 40.5% of the values were ≤ the 3^rd percentile. Patient sex and year of birth were not associated with age at initiation of KRT, but patients diagnosed before the age of 18 months required KRT significantly later than those patients diagnosed at the age of ≥ 18 months (p = 0.033): median renal survival was 21 years (95% CI: 16, -) vs. 13 years (95% CI, 10, -), respectively.

Conclusion

Early diagnosis and initiation of cystine depleting therapy is important for renal survival in children with INC. Cysteamine doses and LCL showed that treatment in this cohort met international standards although there is great interindividual variety. Patient growth and other aspects of the disease should be managed more effectively in the future.

Molecular characterization of CTNS mutations in Tunisian patients with ocular cystinosis

Background

Ocular cystinosis is a rare autosomal recessive disorder characterized by intralysosomal cystine accumulation in renal, ophthalmic (cornea, conjunctiva), and other organ abnormalities. Patients with ocular cystinosis are mostly asymptomatic and typically experience mild photophobia due to cystine crystals in the cornea observed accidently during a routine ocular examination. The ocular cystinosis is associated with different mutations in CTNS gene. Cysteamine therapy mostly corrects the organ abnormalities.

Methods

This study was performed in collaboration with the department of ophthalmology of Farhat Hached Hospital. The Optical Coherence Tomography (OCT) of the cornea and retinal photography were used to search cystine crystals within the corneas and conjunctiva in eight Tunisian patients. Screening for the common 57-kb deletion was performed by standard multiplex PCR, followed by direct sequencing of the entire CTNS gene.

Results

The studied patients were found to have cystine crystal limited anterior corneal stroma and the conjunctiva associated with retinal crystals accumulation. CTNS gene sequencing disclosed 7 mutations: three missense mutations (G308R, p.Q88K, and p.S139Y); one duplication (C.829dup), one framshift mutation (p.G258f), one splice site mutation (c.681 + 7delC) and a large deletion (20,327-bp deletion). Crystallographic structure analysis suggests that the novel mutation p.S139Y is buried in a first transmembrane helix closed to the lipid bilayer polar region, introducing a difference in hydrophobicity which could affect the hydrophobic interactions with the membrane lipids. The second novel mutation p.Q88K which is located in the lysosomal lumen close to the lipid membrane polar head region, introduced a basic amino acid in a region which tolerate only uncharged residue. The third missense mutation introduces a positive change in nonpolar tail region of the phospholipid bilayer membrane affecting the folding and stability of the protein in the lipid bilayer.

Conclusions

Our data demonstrate that impaired transport of cystine out of lysosomes is the most common, which is obviously associated with the mutations of transmembrane domains of cystinosine resulting from a total loss of its activity.

Expert guidance on the multidisciplinary management of cystinosis in adolescent and adult patients

Cystinosis, a rare autosomal recessive lysosomal storage disorder, results in an abnormal accumulation of the amino acid cystine in multiple organs and tissues of the body. Renal symptoms typically develop in the first few months of life, with extra-renal manifestations becoming apparent over the next 10–20 years, which require coordinated multidisciplinary care. Here, we describe a consensus-based guidance to support the management of adolescents and adults living with cystinosis. The programme was led by a Steering Committee (SC) of six experts in the management of patients with cystinosis, who identified a list of 15 key questions reflecting the multi-organ effects of cystinosis. An Extended Faculty (EF) of eight additional specialists was invited to answer the questions via an online digital platform using a quasi-Delphi approach. The consolidated answers were summarized into recommendations. Where evidence was lacking, recommendations were developed using collective expert consensus. The EF was asked to agree/disagree with the clinical recommendations. The expert-agreed clinical recommendations provide guidance that considers both renal and extra-renal systems. The topics covered are advice on fertility and family planning, consideration of the nervous, muscular, ophthalmic, cardio-respiratory, endocrine, dermatological and gastrointestinal systems, as well as guidance on dental care, diet, lifestyle, and improving quality of life and psychological well-being. In summary, this work outlines recommendations and a checklist for clinicians with a vision for improving and standardizing the multidisciplinary care for patients with cystinosis.

Limitations and Challenges in the Stability of Cysteamine Eye Drop Compounded Formulations

Accumulation of cystine crystals in the cornea of patients suffering from cystinosis is considered pathognomonic and can lead to severe ocular complications. Cysteamine eye drop compounded formulations, commonly prepared by hospital pharmacy services, are meant to diminish the build-up of corneal cystine crystals. The objective of this work was to analyze whether the shelf life proposed for six formulations prepared following different protocols used in hospital pharmacies is adequate to guarantee the quality and efficacy of cysteamine eye drops. The long-term and in-use stabilities of these preparations were studied using different parameters: content of cysteamine and its main degradation product cystamine; appearance, color and odor; pH and viscosity; and microbiological analysis. The results obtained show that degradation of cysteamine was between 20% and 50% after one month of storage in the long-term stability study and between 35% and 60% in the in-use study. These data confirm that cysteamine is a very unstable molecule in aqueous solution, the presence of oxygen being the main degradation factor. Saturation with nitrogen gas of the solutions offers a means of reducing cysteamine degradation. Overall, all the formulae studied presented high instability at the end of their shelf life, suggesting that their clinical efficacy might be dramatically compromised.

Posterior segment optical coherence tomography findings in a case of nephropathic cystinosis

Cystinosis is a rare autosomal recessive lysosomal storage disorder characterized by abnormal accumulation of intracellular cystine in various tissues including the brain, kidneys, bones, and eyes. Infantile nephropathic cystinosis is the most severe phenotype of cystinosis that has been associated with a wide spectrum of ocular features. In this report, the author describes a posterior segment spectral-domain optical coherence tomography (SD-OCT) finding that has not been previously reported in a case of nephropathic cystinosis.

Examination of corneal deposits in nephropathic cystinosis using in vivo confocal microscopy and anterior segment optical coherence tomography: an age-dependent cross sectional study

Background

Presence of corneal cystine crystals is the main ocular manifestation of cystinosis, although controversial findings concerning the corneal layer with the highest density have been reported. The aim of this study was the analysis of the characteristics of crystal arrangement in different corneal layers and the assessment of corneal morphological changes with age.

Methods

A cross sectional study was carried out in three children and three adults who had nephropathic cystinosis and corneal cystine depositions. All patients underwent a comprehensive ophthalmological examination including best corrected distance visual acuity, slit-lamp examination, in vivo confocal microscopy and anterior segment optical coherence tomography. An evaluation of the depth of crystal deposits and crystal density in different corneal layers was also performed. Due to the low number of subjects no statistical comparison was performed.

Results

Anterior segment optical coherence tomography images revealed deposition of hyperreflective crystals from limbus to limbus in each patient. Crystals appeared as randomly oriented hyperreflective, elongated structures on in vivo confocal microscopy images in all corneal layers except the endothelium. In children the deposits occurred predominantly in the anterior stroma, while in adults, the crystals were mostly localized in the posterior corneal stroma with the depth of crystal deposition showing an increasing tendency with age (mean depth of crystal density was 353.17 ± 49.23 μm in children and it was 555.75 ± 25.27 μm in adults). Mean crystal density of the epithelium was 1.47 ± 1.17 (median: 1.5; interquartile range: 0.3–2.4). Mean crystal density of the anterior and posterior stroma of children and adults was 3.37 ± 0.34 (median: 3.4; interquartile range: 3.25–3.55) vs. 1.23 ± 0.23 (median: 1.2; interquartile range: 1.05–1.35) and 0.76 ± 0.49 (median: 0.7; interquartile range: 0.4–1.15) vs. 3.63 ± 0.29 (median: 3.7; interquartile range: 3.45–3.8), respectively. Endothelium had intact structure in all cases. Some hexagonal crystals were observed in two subjects.

Conclusions

In vivo confocal microscopy and anterior segment optical coherence tomography confirmed an age-related pattern of crystal deposition. In children, crystals tend to locate anteriorly, while in adults, deposits are found posteriorly in corneal stroma.

Ophthalmic Outcome in a Belgian Cohort of Cystinosis Patients Treated with a Compounded Preparation of Cysteamine Eye Drops: Retrospective Analysis

INTRODUCTION

Treatment of the anterior segment problems in cystinosis is challenging as oral cysteamine is ineffective in the treatment of corneal problems because of its avascular structure. Although cysteamine eye drops have been formulated to counter this issue, the stability of cysteamine in these off-licensed formulations and treatment compliance are major problems. The aim of this retrospective study was to determine the efficacy of a compounded preparation of aqueous 0.5% cysteamine eye drops in the management of corneal complications of cystinosis.

METHODS

Data of patients attending the multidisciplinary cystinosis clinic at the University Hospitals Leuven, Belgium between January 2015 and December 2018 were analyzed. All cystinosis patients were treated with the compounded preparation of aqueous 0.5% cysteamine eye drops and oral cysteamine.

RESULTS

A total of 12 patients were treated with the compounded preparation of aqueous 0.5% cysteamine eye drops, of whom 75% were aged > 18 years (n = 9). The mean instillation frequency of the cysteamine eye drops was 3.3 drops/eye per day, and the mean number of hospital visits was two per year. All patients showed photophobia, > 30% corneal infiltration, blepharospasm, eye pain and conjunctival hyperemia during the study period. None of these symptoms improved with treatment with aqueous compounded 0.5% cysteamine eye drops. The corneal cystine crystal score was ≥ 2 in all patients at the last  visit.

CONCLUSION

Treatment with the compounded preparation of aqueous 0.5% cysteamine eye drops, combined with oral cysteamine, was not effective in reducing corneal cystine crystal deposition and other ocular symptoms in these patients with cystinosis.

FUNDING

Recordati Rare Diseases.

The Ocular Status of Cystinosis Patients Receiving a Hospital Pharmacy-Made Preparation of Cysteamine Eye Drops: A Case Series

Introduction

Infantile nephropathic cystinosis (INC) is an autosomal recessive lysosomal disorder in which patients develop deposits of cystine crystals in their kidneys and corneas from a young age.

Methods

We conducted a retrospective analysis of children with INC seen by ophthalmologists at the Manchester Royal Eye Hospital between 2002 and 2018, to evaluate clinical findings, symptoms and treatment.

Results

Twenty-two children diagnosed with INC from age 0 (prenatally) to 11 years were assessed. All evaluable patients had corneal cystine crystal deposits, and 15 had mild to moderate photophobia. Ten patients had other ocular conditions including blepharitis/chalzion (n = 6), swollen optic nerve (n = 3), punctate epitheliopathy (n = 3), corneal scarring (n = 1),and elevated intraocular pressure (n = 2). Confocal imaging identified nerve abnormalities in two patients (enlarged corneal nerve + abnormal-looking tortuous nerves in one patient and beaded nerves in the sub-basal plexus in the other), both of whom had significant crystal deposition in the anterior stroma. Visual acuity was relatively unaffected. All 22 patients were receiving oral cysteamine, and 21 were applying cysteamine eye drops (galenic preparation of 0.55% concentration, compounded by a hospital pharmacy). Recommended application frequency was at least eight times per day in all patients with dosing information available.

Conclusions

This case series of patients with INC highlights the consistent pattern of corneal cystine crystal deposition, which is universally present from a young age in this condition, and the high incidence of photophobia even in young children. Corneal manifestations of INC persisted despite frequent administration of the hospital pharmacy-made eye drop preparation. Reasons for this lack of efficacy may include the lag period between diagnosis and first prescription of cysteamine eye drops and the difficulty in maintaining rigorous compliance with this treatment. In addition, the challenge for patients of maintaining optimal storage conditions may adversely affect the stability and efficacy of cysteamine within this preparation.

Funding

Editorial assistance was funded by Orphan Europe Ltd.

Latest Clinical Approaches in the Ocular Management of Cystinosis: A Review of Current Practice and Opinion from the Ophthalmology Cystinosis Forum

Cystinosis, a rare autosomal recessive disease caused by intracellular cystine accumulation, occurs in an estimated 1/100,000-200,000 live births. Ocular non-nephropathic cystinosis is typically diagnosed during adulthood, when patients present with corneal crystal deposition and no systemic involvement. Due to the rarity of the condition, diagnosis is often delayed and can have a significant impact on the overall prognosis of the disease. Early diagnosis is therefore imperative to ensure successful treatment and improve quality of life, as most of its clinical manifestations can be prevented or delayed. Early detection strategies and practical approaches for the ocular management of cystinosis were discussed during the Ophthalmology Cystinosis Forum, a 1-day meeting held in Berlin, Germany during June 2017. Recommendations for early detection comprise ophthalmic assessment, including self- and clinician-assessed recording of photophobia, and visual acuity, slit-lamp examination and tonometry ophthalmic examinations. In vivo confocal microscopy and anterior segment optical coherence tomography were highlighted as valuable techniques in evaluating cystine crystals in the cornea, in vivo and non-invasively. The mainstay of ocular cystinosis treatment is the cystine-depleting aminothiol cysteamine. Indeed, early treatment with and strict adherence to cysteamine therapy has a considerable impact on the long-term prognosis of ocular cystinosis. In rare diseases such as ocular cystinosis, standardised guidelines and recommendations for detection, patient care and follow-up assessments are essential. Such guidelines provide a support tool for healthcare professionals caring for ocular cystinosis patients. Multidisciplinary teams (MDTs) are essential for delivering gold standard care and improving quality of life for patients and their families. This review paper highlights current early detection policies, clinical treatment strategies and practical approaches for the ocular management of cystinosis, including implementing a cystinosis MDT. Additionally, discussions of the Ophthalmology Cystinosis Forum held in 2017 are summarised. FUNDING: Orphan Europe. Plain language summary available for this article.