Assessment and diagnosis of suspected glaucoma in patients with mucopolysaccharidosis

Childhood glaucoma: Implications for genetic counselling

Childhood glaucoma is a heterogeneous group of ocular disorders defined by an age of onset from birth to 18 years. These vision-threatening disorders require early diagnosis, timely treatment, and lifelong management to maintain vision and minimise irreversible blindness. The genetics of childhood glaucoma is complex with both phenotypic and genetic heterogeneity. The purpose of this review is to summarise the different types of childhood glaucoma and their genetic architecture to aid in the genetic counselling process with patients and their families. We provide an overview of associated syndromes and discuss implications for genetic counselling, including genetic testing strategies, cascade genetic testing, and reproductive options.

Genetic Aspects of Glaucoma: An Updated Review

Glaucoma is a group of diverse diseases characterized by cupping of the optic nerve head due to the loss of retinal ganglion cells. It is the most common cause of irreversible blindness throughout the world; therefore, its timely diagnosis and early detection through an ophthalmological examination are very important. We, herein, present the information on the epidemiology, pathophysiology, clinical diagnosis, and treatment of glaucoma. We also emphasize the investigations of the last decades that have allowed identifying numerous genes and susceptibility genetic factors. We have also described in detail the genes whose mutations cause or contribute to the development of the disease.

Mucopolysaccharidosis

Mucopolysaccharidosis are group of inherited metabolic diseases caused by the absence or malfunctioning of lysosomal enzymes resulting in accumulation of glycosaminoglycans. Over time this accumulation damages cells, tissues, and organs. There are seven types of MPS and 13 subtypes that are associated with multiple organ systems, such as the respiratory, liver, spleen, central nervous systems, arteries, skeletons, eyes, joints, ears, skin, and/or teeth. The various types share some common ocular features that differ in terms of the severity of the affection. Visual loss in MPS patients is varied and can be due to corneal clouding, glaucoma, retinopathy, and optic neuropathy. The primary focus of this review is on changes in the cornea and anterior segment in MPS patients, including clinical and novel investigative modalities, current surgical management, effects of systemic therapy like hematopoietic stem cell transplants (HSCT)and enzyme replacement therapy (ERT), as well as significant research developments.

Objectively measuring anterior segment alterations in the eyes of mucopolysaccharidoses: Its utility in early diagnosis of glaucoma

Purpose

Our study aimed to evaluate the utility of the anterior segment morphometry for objectively assessing anterior segment architectural changes of corneal clouding in the mucopolysaccharidoses (MPS) cohort and to investigate whether these measurements correlate with the slit-lamp findings on the cornea and early diagnosis of glaucoma.

Methods

This retrospective study involved 70 eyes of 35 children with cloudy cornea due to MPS variants. Anterior segment architectural alterations were measured using anterior segment imaging and biometry in MPS children and compared with controls.

Results

Mean age of the cohort at the time of assessment was 7.9 ± 4.5 years. Males constituted two-thirds of the cohort. Variants of MPS with cloudy cornea were as follows: Type I (62%), Type IV (11%), and Type VI (22%). Morphometric measurements were available in 22 eyes of 11 MPS children and an age-matched healthy control group. There were significant differences between MPS cohort and controls in refraction in Diopters (5.03 ± 0.39 and 0.01 ± 0.04; P < 0.0001), axial length (AXL) in mm (21.39 ± 0.28 and 23.04 ± 0.28; P = 0.0002), average keratometry in Diopters (40.67 ± 0.44 and 42.83 ± 0.44; P < 0.0001), anterior chamber depth (ACD) in mm (2.92 ± 0.07 and 3.65 ± 0.07; P < 0.0001), and intraocular pressure (IOP) in mmHg (25.2 ± 2.0 and 14.1 ± 2.3; P = 0.0003). Secondary glaucoma was observed in 28% of the MPS cohort.

Conclusion

The anterior segment morphometry in the cloudy cornea due to MPS provides an objective measurement of anterior segment architectural changes, thus diagnosing early-onset secondary glaucoma. These findings highlight that cloudy cornea due to MPS variants merits close monitoring throughout life.

Mucopolysaccharidosis: A broad review

Mucopolysaccharidosis (MPS) is a group of genetic disorders with seven types and 13 subgroups which are characterized by an inherent deficiency of the enzymes responsible for the degradation of glycosaminoglycans (GAGs). Defective breakdown of GAG products leads to their widespread accumulation within the lysosomes of various organs involving the eye, central nervous system, skeletal, ocular, nervous, respiratory, cardiac, and the gastrointestinal systems. Clinical spectrum varies from mild systemic and ocular abnormalities with a normal life span to severe phenotype, fatal in the first few months of life. Visual disability due to corneal clouding, retinopathy, and optic nerve involvement causes additional impairment of physical and cognitive functions. Treatment modalities such as bone marrow transplantation and enzyme replacement therapies help in increasing the life span as well as the quality of life of the affected patients. For patients with significant corneal clouding, keratoplasty is the answer. The decision to proceed with keratoplasty is governed by various factors such as the motivation of the patient and his family, other systemic affections and anesthesia concerns. A detailed preoperative counseling should be done regarding the expected visual outcomes in the presence of other ocular comorbidities and the postoperative complication such as graft re-opacification, rejection and glaucoma. Future treatment options such as targeted gene therapy and substrate reduction therapy hold promise to reverse corneal clouding, thereby obviating the need for corneal transplantation. These treatment therapies are still in the experimental stages and human trials are needed to validate their outcomes.

Increased Choroidal Thickness in Morquio Syndrome

The purpose of this clinical case report is to describe a case of mucopolysaccharidosis type IVA (MPS IVA), or Morquio syndrome, with increased choroidal thickness in enhanced-depth imaging optical coherence tomography (EDI-OCT) which can represent choroidal deposition of glycosaminoglycans (GAGs). A 21-year-old male with genetically confirmed diagnosis of MPS IVA was examined at our Pediatric Ophthalmology clinic as part of our follow-up protocol for MPS patients. His best-corrected visual acuity was 4/10 in his right eye (OD) and 6/10 in the left eye (OS). Mild diffuse corneal opacification was evident. Intraocular pressure was within normal range. Fundus examination and color fundus photography revealed no abnormalities. EDI-OCT revealed significantly increased choroidal thickness in his right eye and in his left eye, suggesting the presence of choroidal deposition of GAGs, despite absence of retinal or optic disc GAG deposition or other chorioretinal involvement. To our knowledge, this is the first case of MPS IVA described in the literature with suspected choroidal deposition of GAGs. With improved control of systemic features of MPS IVA, life expectancy of these patients has increased, allowing for more ocular manifestations to develop. The parallel development of technology in ophthalmology, such as the EDI-OCT, further contributes to the detection of these unprecedented ocular features in MPSs.

Management of Corneal Clouding in Patients with Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a rare group of lysosomal storage disorders characterized by the accumulation of incompletely degraded glycosaminoglycans (GAGs) in multiple organ systems including the eye. Visual loss occurs in MPS predominantly due to corneal clouding and retinopathy, but the sclera, trabecular meshwork and optic nerve may all be affected. Despite the success of therapies such as enzyme replacement therapy (ERT) and hematopoietic stem-cell transplantation (HSCT) in improving many of the systemic manifestations of MPS, their effect on corneal clouding is minimal. The only current definitive treatment for corneal clouding is corneal transplantation, usually in the form of a penetrating keratoplasty or a deep anterior lamellar keratoplasty. This article aims to provide an overview of corneal clouding, its current clinical and surgical management, and significant research progress.

Glaucoma in mucopolysaccharidoses

Mucopolysaccharidoses are a group of lysosomal storage disorders that are caused by deficiency of enzymes involved in glycosaminoglycans degradation. Due to low prevalence and high childhood mortality, researches on mucopolysaccharidoses were mainly focused on the fatal manifestations. With the development of treatments, more and more mucopolysaccharidoses patients were treated by approved therapies, thereby getting prolonged life span and improved quality of life. Abnormal accumulation of glycosaminoglycans in the eye may block trabecular meshwork, thicken sclera and change mechanical behavior of lamina cribrosa, which, by increasing intraocular pressure and damaging optic nerve, could cause glaucoma. Glaucoma was the leading cause of irreversible blindness worldwide, but it was rarely reported in mucopolysaccharidoses patients. Although non-fatal, it seriously affected quality of life. Prevalence of glaucoma in mucopolysaccharidoses patients (ranged from 2.1 to 12.5%) indicated that glaucoma in patients with mucopolysaccharidoses was worthy of attention and further study, thereby improving the quality of life for MPSs patients.

Ophthalmologic manifestations in Taiwanese patients with mucopolysaccharidoses

Background

Mucopolysaccharidoses (MPSs) are a group of rare lysosomal storage disorders characterized by the accumulation of glycosaminoglycans in various tissues and organs. Ocular problems that affect the cornea, trabecular meshwork, sclera, retina, and optic nerve are very common in these patients. However, there was limited literature focusing on comprehensive ocular findings in different types of MPS.

Methods

We retrospectively reviewed the clinical ophthalmologic features and electrodiagnostic results of 50 Taiwanese patients with a diagnosis of MPS (34 males and 16 females; age range, 1.1–34.9 years; nine with MPS I, 17 with MPS II, 17 with MPS IV, and seven with MPS VI).

Results

Among 44 patients with available data for visual acuity, 15 patients (34%) had a visual acuity of less than 0.5 (6/12) equivalent in their better eye, including 71% of those with MPS VI, 38% with MPS IV, 29% with MPS I, and 14% with MPS II. Severe corneal opacities existed in 57% of MPS VI patients and 11% of MPS I patients, compared with none for MPS II and MPS IV patients. Among 80 eyes with available data of refraction, 11 eyes (14%) had myopia (≦−0.50 D), 55 eyes (69%) had hyperopia (≧0.50 D), and 55 eyes (69%) had high astigmatism (≧1.50 D). Ocular hypertension was found in 45% (28/62) of eyes. There were 16% (14/90), 11% (10/90), 13% (12/90), 31% (27/86), and 79% (30/38) of MPS eyes with lens opacities, optic disc swelling, optic disc cupped, retinopathy, and visual pathway dysfunction, respectively. Intraocular pressure was positively correlated with the severity of corneal opacity (p < 0.01).

Conclusions

Ocular complications with significant reduction in visual acuity are common in MPS patients. Diagnostic problems may arise in these patients with severe corneal opacification, especially for those with MPS VI and MPS I.

Children with mucopolysaccharidosis risk progressive visual dysfunction despite haematopoietic stem cell transplants

AIM

This prospective study assessed the long-term ocular and visual outcomes of children with mucopolysaccharidoses type I Hurler syndrome (MPS IH) who were treated with haematopoietic stem cell transplants (HSCT).

METHODS

Clinical ophthalmological assessments were performed on eight patients at the St Erik Eye Hospital, Huddinge, Stockholm, Sweden, from 2001-2018: The median age at diagnosis and HSCT were 12.2 (range 5.0-16.4) and 16.7 (8.0-20.4) months. The last eye examination was at a median of 13.4 (6.3-19.0) years and follow-up lasted a median of 12.0 (5.0-17.4) years.

RESULTS

Poor visual acuity, poor night vision and, or, photophobia were reported by six children. The best corrected visual acuity at the last visit was a median of 0.4 and 0.5 in the right and left eye and had declined significantly in two patients. Corneal opacities had increased despite HSCT in five patients. High hyperopia, at a median of +6 Dioptres, occurred in all patients and stiff corneas in all four patients that were measured. The patients' corrected intraocular pressures were normal. Retinal degeneration was identified in two patients.

CONCLUSION

Despite HSCT, the long-term follow-up of patients with MPS IH showed reduced visual acuity due to corneal opacities or retinal degeneration.

Structural features of eyelid connective tissue in patients with primary open-angle glaucoma

PURPOSE

To study the connective tissue (CT) structure of upper eyelid skin of primary open-angle glaucoma (POAG) patients.

PATIENTS AND METHODS

Forty-seven patients aged 47-91 expecting blepharoplasty formed 3 groups: group 1 [16 subjects without POAG, median age 55 years (interquartile range 54-55.5)], group 2 [12 subjects without POAG, median age 73 (72-76.5)], and group 3 [(19 subjects with POAG, median age 74 (70-80.5)]. Age differences between groups 1 and 2 and groups 1 and 3 are significant (p < 0.05). Thermodynamic parameters of skin samples taken during blepharoplasty: Endothermic peak ([Formula: see text], °C) and denaturation enthalpy ([Formula: see text], J/g of dry weight) were determined using differential scanning calorimetry.

RESULTS

[Formula: see text] and [Formula: see text] in groups 1-3 were, respectively, 8.41 (7.42-10.25) and 66.55 (59.9-66.7); 7.10 (5.76-10.17) and 67.35 (67.0-68.03); 11.40 (9.0-14.9) and 67.70 (67.05-68.45). [Formula: see text] differences between groups 1 and 2 are significant (p < 0.05), and Spearman's correlation between the age and [Formula: see text] is direct, medium (R = 0.638) and significant. [Formula: see text] in group 3 is significantly higher than in group 2. [Formula: see text] and [Formula: see text] in patients without POAG (groups 1 and 2) and those with POAG (group 3) are, respectively, 7.79 (6.9-10.17) and 66.6 (61.2-67,3); 11.40 (9.0-14.9); 67.7 (67.05-68.45); the respective differences are significant.

CONCLUSION

Patients without POAG show a significant increase in [Formula: see text] with age, while [Formula: see text] slightly decreases. In POAG, [Formula: see text] is significantly higher and [Formula: see text] tends to grow, which may indicate structural changes in eyelid CT (collagen accumulation and cross-linking level rise). Since the upper lid is unaffected by increasing IOP directly, the changes may be viewed as manifestations of systemic CT pathology.

Influence of Corneal Opacity on Intraocular Pressure Assessment in Patients with Lysosomal Storage Diseases

AIMS

To investigate an influence of mucopolysaccharidosis (MPS)- and Morbus Fabry-associated corneal opacities on intraocular pressure (IOP) measurements and to evaluate the concordance of the different tonometry methods.

METHODS

25 MPS patients with or without corneal clouding, 25 Fabry patients with cornea verticillata ≥ grade 2 and 25 healthy age matched controls were prospectively included into this study. Outcome measures: Goldmann applanation tonometry (GAT); palpatory assessment of IOP; Goldmann-correlated intraocular pressure (IOPg), corneal-compensated intraocular pressure (IOPcc), corneal resistance factor (CRF) and corneal hysteresis (CH) assessed by Ocular Response Analyzer (ORA); central corneal thickness (CCT) and density assessed with Pentacam. Statistical analysis was performed using linear mixed effect models and Spearman correlation coefficients. The concordance between tonometry methods was assessed using Bland-Altman analysis.

RESULTS

There was no relevant difference between study groups regarding median GAT, IOPg, IOPcc and CCT measurements. The limits of agreement between GAT and IOPcc/IOPg/palpatory IOP in MPS were: [-11.7 to 12.1mmHg], [-8.6 to 15.5 mmHg] and [- 5.4 to 10.1 mmHg] respectively. Limits of agreement were less wide in healthy subjects and Fabry patients. Palpatory IOP was higher in MPS than in healthy controls and Fabry patients. Corneal opacity correlated more strongly with GAT, IOPg, CH, CRF, CCT and corneal density in MPS (r = 0.4, 0.5, 0.5, 0.7, 0.6, 0.6 respectively) than in Fabry patients (r = 0.3, 0.2, -0.03, 0.1, 0.3, -0.2 respectively). In contrast, IOPcc revealed less correlation with corneal opacity than GAT in MPS (r = 0.2 vs. 0.4).

CONCLUSIONS

ORA and GAT render less comparable IOP-values in patients suffering from MPS-associated corneal opacity in comparison to Fabry and healthy controls. The IOP seems to be overestimated in opaque MPS-affected corneas. GAT, IOPg and biomechanical parameters of the cornea correlate more strongly with the corneal clouding than IOPcc in MPS patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01695161.

Use of new imaging in detecting and monitoring ocular manifestations of the mucopolysaccharidoses

The aim of this review is to summate the eye involvement in patients with mucopolysaccharidoses (MPS) using current ocular imaging techniques, their advantages and disadvantages and how they may aid diagnosis, management and monitoring. We critically reviewed the current literature surrounding MPS and recent imaging technology as well as histology. Primary searches of PubMed and Web of Science were performed. We reviewed all papers on the topic published and summarized the findings of each medical device as well as the advantages and disadvantages of using these for the MPS patient. We discussed the potential of each of these devices to monitor potential ocular pathology in the MPS cohorts in the order of MPS subtype. We reviewed imaging techniques involving use of the Iris Camera, Pentacam, Optical Coherence Tomography (OCT) as well as ultrasound and Heidelberg OCT. The need for reliable objective quantification of eye findings in MPS has led to utilization of new imaging technologies described here, and future use will enhance our understanding of the unique eye features in MPS. In particular, we note that the Pentacam and iris camera are able to provide objective measurements of corneal haze and monitor ocular response to treatment.

Ocular and electrophysiological findings in a patient with Sly syndrome

BACKGROUND

Sly syndrome (Mucopolysaccharidosis Type VII) is an autosomal recessive metabolic storage disorder due to mutations in the GUSB gene encoding the enzyme beta-glucuronidase. Deficiency of this lysosomal enzyme impairs the body's ability to break down the glycosaminoglycans - dermatan, heparan and chondroitin sulphate. Coarse facial features and macrocephaly are typically seen along with bony and skeletal abnormalities, including joint contractures and short stature. Widespread involvement occurs in many other tissues including cardiopulmonary, gastrointestinal, and neurological systems. In view of the rarity of Sly syndrome the ophthalmic features have not been well described.

MATERIALS AND METHODS

Case report of a 16-year-old boy with Sly syndrome with serial OCT, ocular ultrasound, and electroretinogram (ERG).

RESULTS

Corneal clouding was present but there was no evidence of glaucoma or optic neuropathy. Despite no clinical evidence of retinopathy, electrophysiology showed reduced photopic and scotopic responses, particularly involving the b-wave which appears progressive. OCT showed normal foveal architecture and normal retinal nerve fiber thickness.

CONCLUSION

Corneal clouding was noted in this patient and there is no evidence of glaucoma or optic neuropathy. Although retinopathy has not been previously described in Sly syndrome, the ERG changes in this patient suggest that retinopathy may be a feature of MPS VII.

A review of the role of ultrasound biomicroscopy in glaucoma associated with rare diseases of the anterior segment

Ultrasound biomicroscopy is a non-invasive imaging technique, which allows high-resolution evaluation of the anatomical features of the anterior segment of the eye regardless of optical media transparency. This technique provides diagnostically significant information in vivo for the cornea, anterior chamber, chamber angle, iris, posterior chamber, zonules, ciliary body, and lens, and is of great value in assessment of the mechanisms of glaucoma onset. The purpose of this paper is to review the use of ultrasound biomicroscopy in the diagnosis and management of rare diseases of the anterior segment such as mesodermal dysgenesis of the neural crest, iridocorneal endothelial syndrome, phakomatoses, and metabolic disorders.

Social/economic costs and health-related quality of life of mucopolysaccharidosis patients and their caregivers in Europe

OBJECTIVES

To assess the health-related quality of life (HRQOL) of patients with mucopolysaccharidosis (MPS) and their caregivers and to quantify the disease-related costs from a societal perspective.

METHODS

In the context of a multi-country study of rare diseases (BURQOL-RD project), a cross-sectional survey was performed among MPS patients in seven European countries. Data on demographic characteristics, health resource utilization, informal care, and loss of labor productivity were collected. The EQ-5D, Barthel index (BI), and Zarit burden interview (ZBI) questionnaires were used to assess patients' and their informal caregivers' quality of life, patients' functional ability, and caregivers' burden, respectively.

RESULTS

Altogether, 120 patients (children 62 %, females 40 %) and 66 caregivers completed the questionnaire. Patients' mean age was 16.5 years and median age at diagnosis was 3 years. Adult patients' average EQ-5D and EQ VAS scores varied across countries from 0.13 to 0.43 and 30.0 to 62.2, respectively, mean BI was 46.7, and ZBI was 32.7. Mean informal care time was 51.3 h/week. The mean total annual cost per patient (reference year 2012) was €24,520 in Hungary, €25,993 in France, €84,921 in Italy, €94,384 in Spain, and €209,420 in Germany. Costs are also shown to differ between children and adults. Direct costs accounted for most of the costs in all five countries (80, 100, 99, 98, and 93 %, respectively).

CONCLUSIONS

MPS patients experience substantial loss of HRQOL and their families take a remarkable part in their care. Although utilization of health and social care resources varies significantly across countries, MPS incurs considerable societal costs in all the countries studied.

Rare Diseases Leading to Childhood Glaucoma: Epidemiology, Pathophysiogenesis, and Management

Noteworthy heterogeneity exists in the rare diseases associated with childhood glaucoma. Primary congenital glaucoma is mostly sporadic; however, 10% to 40% of cases are familial. CYP1B1 gene mutations seem to account for 87% of familial cases and 27% of sporadic cases. Childhood glaucoma is classified in primary and secondary congenital glaucoma, further divided as glaucoma arising in dysgenesis associated with neural crest anomalies, phakomatoses, metabolic disorders, mitotic diseases, congenital disorders, and acquired conditions. Neural crest alterations lead to the wide spectrum of iridocorneal trabeculodysgenesis. Systemic diseases associated with childhood glaucoma include the heterogenous group of phakomatoses where glaucoma is frequently encountered in the Sturge-Weber syndrome and its variants, in phakomatosis pigmentovascularis associated with oculodermal melanocytosis, and more rarely in neurofibromatosis type 1. Childhood glaucoma is also described in systemic disorders of mitotic and metabolic activity. Acquired secondary glaucoma has been associated with uveitis, trauma, drugs, and neoplastic diseases. A database research revealed reports of childhood glaucoma in rare diseases, which do not include glaucoma in their manifestation. These are otopalatodigital syndrome, complete androgen insensitivity, pseudotrisomy 13, Brachmann-de Lange syndrome, acrofrontofacionasal dysostosis, caudal regression syndrome, and Wolf-Hirschhorn syndrome.

Comparison of Rebound Tonometry, Perkins Applanation Tonometry and Ocular Response Analyser in Mucopolysaccharidosis Patients

AIMS

To investigate the feasibility and to compare three devices measuring intraocular pressure (IOP) in mucopolysaccharidosis patients (MPS): iCare rebound tonometer (RT), Perkins applanation tonometer (PAT) and ocular response analyzer (ORA).

METHODS

MPS patients who underwent at least two examinations out of: RT, PAT and ORA at the same visit were identified and retrospectively analyzed in this study.

RESULTS

17 patients fulfilled the inclusion criterion. In all 17 patients IOP measurements were performed with RT (34 eyes) and ORA (33 eyes), while PAT measurement was possible in only 12 (24 eyes) patients. The RT, corneal-compensated intraocular pressure (IOPcc) and Goldmann-correlated intraocular pressure (IOPg) differed relevantly from IOP assessed with PAT. Corneal clouding in MPS patients correlated positively with PAT, RT and IOPg (r = 0.3, 0.5, and 0.5 respectively), but not with IOPcc (r = 0.07). The MPS-related corneal clouding correlated positively with biomechanical corneal parameters assessed with ORA: corneal hysteresis (r = 0.77) and corneal resistance factor (r = 0.77) either.

CONCLUSIONS

RT and ORA measurements were tolerated better than applanation tonometry in MPS patients. IOP measurements assessed with RT and ORA differed relevantly from PAT. Corneal-compensated IOP assessed with ORA seems to be less affected by the MPS-related corneal clouding than applanation or rebound tonometry. RT and ORA measurements should be preferred for IOP assessment in patients with MPS.