Central corneal thickness is lower in osteogenesis imperfecta and negatively correlates with the presence of blue sclera

Ophthalmological screening guidelines for individuals with Osteogenesis Imperfecta: a scoping review

BACKGROUND

Osteogenesis imperfecta (OI) is a connective tissue disorder in which the Type 1 collagen is defective. The eye is a structure rich in collagen Type 1 and is heavily impacted by the disease. Many vision-threatening eye diseases have been associated with OI. The onset of these diseases also tend to occur at an earlier age in individuals with OI. Despite the research on these risks, appropriate ophthalmological screening or care guidelines for individuals with OI remain unknown. As such, the purpose of this scoping review was to explore and describe existing ophthalmological screening and care guidelines to orient OI patient care.

MAIN BODY

A scoping review based on the Joanna Briggs Institute (JBI) methodology was conducted. A search of databases (PubMed and Medline) was completed in consultation with a research librarian. A total of 256 studies were imported for screening. Primary sources matching the inclusion and exclusion criteria were screened, extracted, and analyzed using Covidence.

CONCLUSION

A total of 12 primary articles met inclusion and exclusion criteria, containing case reports, case series and cohort studies. Despite the risk of blindness associated with the consequences of OI on the eye, the primary literature fails to provide detailed screening and care guidelines aimed at identifying disease early. We provide general recommendations based on the review findings to guide the ophthalmological care of patients with OI and call upon the experts to convene globally to create screening guidelines. Further investigations of ophthalmological screening are warranted to limit these vision-threatening risks with early detection and treatment. Standardized ophthalmological screening guidelines for OI remain an area for research.

Reduced Retinal Blood Vessel Densities Measured by Optical Coherence Tomography Angiography in Keratoconus Patients Are Negatively Correlated with Keratoconus Severity

Keratoconus (KC) is the most common corneal ectasia. Optical coherence tomography angiography (OCT-A) is a relatively new non-invasive imaging technique that allows the visualization and quantification of retinal and choriocapillary blood vessels. The aim of this study is to assess retinal and choriocapillary vessel density (VD) differences between KC patients and healthy controls and to investigate correlations between VD and KC severity. Fifty-two eyes were included in this exploratory study: twenty-six eyes from 26 KC patients and twenty-six eyes from 26 age- and gender-matched healthy controls. All patients underwent Scheimpflug corneal topography with Pentacam, axis lengths measurement and optical coherence tomography angiography (OCT-A). The thinnest spot in corneal pachymetry, maximum K (Kmax) and KC severity indices from the Belin/Ambrósio enhanced ectasia display (BAD) were also assessed. There was a distinct reduction particularly in the retinal VD of the superficial capillary plexus (SCP). Correlation analyses showed strong and moderate negative correlations between the VD in the macular SCP and BAD KC scores and between the SCP VD and Kmax. There was no difference in retinal thickness between the KC and healthy controls. With this study, further evidence for altered VD measurements by OCT-A in KC patients is given. For the first time, we demonstrated negative correlations between BAD KC scores and retinal blood vessel alterations. A major limitation of the study is the relatively small sample size. Since an artefactual reduction of the quantitative OCT-A measurements due to irregular corneal topography in KC must be assumed, it remains to be investigated whether there are also actual changes in the retinal microcirculation in KC.

Emerging Landscape of Osteogenesis Imperfecta Pathogenesis and Therapeutic Approaches

Osteogenesis imperfecta (OI) is an uncommon genetic disorder characterized by shortness of stature, hearing loss, poor bone mass, recurrent fractures, and skeletal abnormalities. Pathogenic variations have been found in over 20 distinct genes that are involved in the pathophysiology of OI, contributing to the disorder's clinical and genetic variability. Although medications, surgical procedures, and other interventions can partially alleviate certain symptoms, there is still no known cure for OI. In this Review, we provide a comprehensive overview of genetic pathogenesis, existing treatment modalities, and new developments in biotechnologies such as gene editing, stem cell reprogramming, functional differentiation, and transplantation for potential future OI therapy.

Progressive Keratoconus in a Patient With Severe Pectus Excavatum and a Cartilage Oligomeric Matrix Protein Gene Mutation: A Case Report

INTRODUCTION

Keratoconus is a progressive ocular disorder associated with numerous systemic diseases, many of which affect the musculoskeletal system. Although the etiology and pathophysiology of the disorder remain elusive, recent studies suggest a significant role of genetic predisposition in the pathogenesis of keratoconus. This case report aims to elucidate a potential genetic association in a patient presenting with keratoconus, severe pectus excavatum, generalized muscular weakness, and skeletal deformities.

CASE DESCRIPTION

A 31-year-old Iranian man presented with progressively diminishing vision in both eyes over the years, eventually diagnosed with keratoconus. The patient's history and further examination indicated generalized muscular weakness, skeletal deformities, and severe pectus excavatum with cardiac and large vessel displacement. Whole-exome sequencing identified two heterozygous gene variants: one in the Cartilage Oligomeric Matrix Protein (COMP) gene and another in the Regulating Synaptic Membrane Exocytosis 1 gene. The patient's systemic and ocular symptoms, combined with the gene variants identified, suggested a connective tissue systemic disorder, potentially within the clinical spectrum of COMPopathies.

CONCLUSION

This is the first documented case of bilateral progressive keratoconus associated with severe pectus excavatum, generalized musculoskeletal dystrophy, and a COMP gene mutation. It highlights the necessity of continued search into the pathogenic genes of keratoconus, particularly in cases with coexisting systemic manifestations, to further our understanding of the etiology and pathogenesis of this complex disease.

Keratoconus tomographic indices in osteogenesis imperfecta

PURPOSE

Osteogenesis imperfecta (OI) is a rare inherited disease affecting collagen-rich tissues. Ocular complications have been reported such as thin corneas, low ocular rigidity, keratoconus, among others. The purpose of this study is to characterize corneal tomographic features in OI patients compared to unaffected patients, with particular focus on commonly studied keratoconus indices.

METHODS

Cross-sectional case-control study including 37 OI patients and 37 age-matched controls. Patients and controls underwent comprehensive ophthalmological examination including corneal Scheimpflug tomography with a Pentacam HR device (Oculus Optikgeräte GmbH, Wetzlar, Germany) to analyse and compare topometric, tomographic, pachymetric and Belin-Ambrósio Enhanced Ectasia Display III (BAD-D) data of both eyes of each patient.

RESULTS

Most OI patients had type I disease (n = 24; 65%) but type III-VII patients were also included. Two patients had clinically overt bilateral keratoconus. OI patients had significantly higher maximum keratometry (45.2 ± 2.1 vs. 43.7 ± 1.2; p = 0.0416), front and back elevation (3.0 ± 3.3 vs. 2.1 ± 1.3, p = 0.0201; 11.1 ± 8.2 vs. 5.0 ± 3.7, p < 0.0001), index of surface variance (25.5 ± 13 vs. 17.4 ± 8.3; p = 0.0016), index of vertical asymmetry (0.21 ± 0.14 vs. 0.15 ± 0.06; p = 0.0215), index of height asymmetry (9.2 ± 14 vs. 6.0 ± 4.5; p = 0.0421), index of height decentration (0.02 ± 0.01 vs. 0.01 ± 0.01; p < 0.0001) and average pachymetric progression (1.01 ± 0.19 vs. 0.88 ± 0.14; p < 0.0001) readings. Thinnest corneal thickness and maximum Ambrósio relational thickness were significantly lower (477 ± 52 vs. 543 ± 26; 387 ± 95 vs. 509 ± 49; p < 0.0001). Two-thirds of OI patients had corneas with a minimum thickness < 500 µm. BAD-D value was significantly higher in OI patients (2.1 ± 1.4 vs. 0.9 ± 0.2; p < 0.0001).

CONCLUSION

OI patients showed significant changes in corneal profiles compared with healthy subjects. A high proportion of patients had tomographically suspect corneas when using keratoconus diagnostic indices. Further studies are warranted to assess the true risk of corneal ectasia in OI patients.

Systemic Associations with Keratoconus

Keratoconus is a disease of the cornea that results in progressive steepening and thinning of the cornea and subsequent vision loss. It nearly always presents as a bilateral disease, suggesting that there is an underlying abnormality of the corneas that becomes manifest with time. However, the mechanisms underlying the development of keratoconus are largely unknown. Associations reported between keratoconus and systemic diseases are abundant in the literature, and the list of possible associations is very long. We found that atopy, Down syndrome, and various connective tissue diseases were the most frequently cited associations in our broad literature search. Additionally, Diabetes Mellitus has been increasingly studied as a possible protective factor against keratoconus. In this review, we have summarized the evidence for and against these particular systemic conditions and keratoconus and have discussed some of the implications of keratoconus patients having these conditions.

Assessment of the Retinal Nerve Fibre Layer, Retina, and Choroid in Osteogenesis Imperfecta

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic disorder in which there are problems in tissues containing type I collagen, predominantly the cornea and sclera in the eye. Although there are many studies on problems with the anterior segment of the eye in patients with OI, studies on posterior structures are limited. Involvement of the sclera may affect the retinal nerve fibre layer (RNFL), which is indirectly related to intraocular pressure. In addition, the retina and choroid containing type I collagen may be affected. The aim of the study was to compare the posterior segment structures of the eye, including the RNFL, retina, and choroid, in patients with OI to those of healthy control subjects.

METHODS

This cross-sectional study recruited 19 patients with OI, as well as 22 age- and gender-similar healthy control subjects. Measurements of the RNFL, retina, and choroid were obtained with optical coherence tomography (Spectralis SD-OCT, Heidelberg Engineering, Heidelberg, Germany).

RESULTS

Patients with OI (mean age 14.32 ± 5.08 years) and the control group (mean age 13.73 ± 3.56 years) had similar age, refractive error, and intraocular pressure values (p > 0.05). There was no difference between groups in terms of RNFL thickness, including the superonasal, nasal, inferonasal, inferotemporal, temporal, and superotemporal sectors, retinal thickness, and choroidal thickness from five different locations (p > 0.05, for all).

CONCLUSION

According to these results, OI does not clinically affect the RNFL, retina, and choroid in childhood.

Into the Tissues: Extracellular Matrix and Its Artificial Substitutes: Cell Signalling Mechanisms

The existence of orderly structures, such as tissues and organs is made possible by cell adhesion, i.e., the process by which cells attach to neighbouring cells and a supporting substance in the form of the extracellular matrix. The extracellular matrix is a three-dimensional structure composed of collagens, elastin, and various proteoglycans and glycoproteins. It is a storehouse for multiple signalling factors. Cells are informed of their correct connection to the matrix via receptors. Tissue disruption often prevents the natural reconstitution of the matrix. The use of appropriate implants is then required. This review is a compilation of crucial information on the structural and functional features of the extracellular matrix and the complex mechanisms of cell-cell connectivity. The possibilities of regenerating damaged tissues using an artificial matrix substitute are described, detailing the host response to the implant. An important issue is the surface properties of such an implant and the possibilities of their modification.

Ocular characteristics and complications in patients with osteogenesis imperfecta: a systematic review

PURPOSE

Osteogenesis imperfecta (OI) is a rare inherited heterogeneous connective tissue disorder characterized by bone fragility, low bone mineral density, skeletal deformity and blue sclera. The dominantly inherited forms of OI are predominantly caused by mutations in either the COL1A1 or COL1A2 gene. Collagen type I is one of the major structural proteins of the eyes and therefore is the eye theoretically prone to alterations in OI. The aim of this systematic review was to provide an overview of the known ocular problems reported in OI.

METHODS

A literature search (in PubMed, Embase and Scopus), which included articles from inception to August 2020, was performed in accordance with the PRISMA guidelines.

RESULTS

The results of this current review show that almost every component of the eye could be affected in OI. Decreased thickness of the cornea and sclera is an important factor causing eye problems in patients with OI such as blue sclera. Findings that stand out are ruptures, lacerations and other eye problems that occur after minor trauma, as well as complications from standard surgical procedures.

DISCUSSION

Alterations in collagen type I affect multiple structural components of the eye. It is recommended that OI patients wear protective glasses against accidental eye trauma. Furthermore, when surgery is required, it should be approached with caution. The prevalence of eye problems in different types of OI is still unknown. Additional research is required to obtain a better understanding of the ocular defects that may occur in OI patients and the underlying pathology.

Glaucoma Syndromes: Insights into Glaucoma Genetics and Pathogenesis from Monogenic Syndromic Disorders

Monogenic syndromic disorders frequently feature ocular manifestations, one of which is glaucoma. In many cases, glaucoma in children may go undetected, especially in those that have other severe systemic conditions that affect other parts of the eye and the body. Similarly, glaucoma may be the first presenting sign of a systemic syndrome. Awareness of syndromes associated with glaucoma is thus critical both for medical geneticists and ophthalmologists. In this review, we highlight six categories of disorders that feature glaucoma and other ocular or systemic manifestations: anterior segment dysgenesis syndromes, aniridia, metabolic disorders, collagen/vascular disorders, immunogenetic disorders, and nanophthalmos. The genetics, ocular and systemic features, and current and future treatment strategies are discussed. Findings from rare diseases also uncover important genes and pathways that may be involved in more common forms of glaucoma, and potential novel therapeutic strategies to target these pathways.

Controversy and Consideration of Refractive Surgery in Patients with Heritable Disorders of Connective Tissue

Heritable Disorders of Connective Tissue (HDCTs) are syndromes that disrupt connective tissue integrity. They include Osteogenesis Imperfecta (OI), Ehlers Danlos Syndrome (EDS), Marfan Syndrome (MFS), Loeys-Dietz Syndrome (LDS), Epidermolysis Bullosa (EB), Stickler Syndrome (STL), Wagner Syndrome, and Pseudoxanthoma Elasticum (PXE). Because many patients with HDCTs have ocular symptoms, commonly myopia, they will often present to the clinic seeking refractive surgery. Currently, corrective measures are limited, as the FDA contraindicates laser-assisted in-situ keratomileusis (LASIK) in EDS and discourages the procedure in OI and MFS due to a theoretically increased risk of post-LASIK ectasia, poor wound healing, poor refractive predictability, underlying keratoconus, and globe rupture. While these disorders present with a wide range of ocular manifestations that are associated with an increased risk of post-LASIK complications (e.g., thinned corneas, ocular fragility, keratoconus, glaucoma, ectopia lentis, retinal detachment, angioid streaks, and ocular surface disease), their occurrence and severity are highly variable among patients. Therefore, an HDCT diagnosis should not warrant an immediate disqualification for refractive surgery. Patients with minimal ocular manifestations can consider LASIK. In contrast, those with preoperative signs of corneal thinning and ocular fragility may find the combination of collagen cross-linking (CXL) with either photorefractive keratotomy (PRK), small incision lenticule extraction (SMILE) or a phakic intraocular lens (pIOL) implant to be more suitable options. However, evidence of refractive surgery performed on patients with HDCTs is limited, and surgeons must fully inform patients of the unknown risks and complications before proceeding. This paper serves as a guideline for future studies to evaluate refractive surgery outcomes in patients with HDCTs.

A Mouse Model of Brittle Cornea Syndrome caused by mutation in Zfp469

Brittle cornea syndrome (BCS) is a rare recessive condition characterised by extreme thinning of the cornea and sclera. BCS results from loss-of-function mutations in the poorly understood genes ZNF469 or PRDM5. In order to determine the function of ZNF469 and to elucidate pathogenic mechanisms, we used genome editing to recapitulate a human ZNF469 BCS mutation in the orthologous mouse gene Zfp469. Ophthalmic phenotyping showed that homozygous Zfp469 mutation causes significant central and peripheral corneal thinning arising from reduced stromal thickness. Expression of key components of the corneal stroma in primary keratocytes from Zfp469^BCS/BCS mice is affected, including decreased Col1a1 and Col1a2 expression. This alters the collagen type I/collagen type V ratio and results in collagen fibrils with smaller diameter and increased fibril density in homozygous mutant corneas, correlating with decreased biomechanical strength in the cornea. Cell-derived matrices generated by primary keratocytes show reduced deposition of collagen type I, offering an in vitro model for stromal dysfunction. Work remains to determine whether modulating ZNF469 activity will have therapeutic benefit in BCS or in conditions such as keratoconus in which the cornea thins progressively.

This article has an associated First Person interview with the first author of the paper.

Summary: A mouse model of brittle cornea syndrome was created to elucidate molecular mechanisms underlying the pathology of this rare connective tissue disorder in which extremely thin corneas rupture, causing irreversible blindness.

Diagnosis and management of pediatric metabolic bone diseases associated with skeletal fragility

PURPOSE OF REVIEW

The goal of this review is to give an overview of diagnosis and up-to-date management of major pediatric metabolic bone diseases that are associated with bone fragility, including nutritional rickets, hypophosphatemic rickets, osteogenesis imperfecta, Ehlers--Danlos syndrome, Marfan's syndrome, hypophosphatasia, osteopetrosis and skeletal fluorosis.

RECENT FINDINGS

During the past decade, a number of advanced treatment options have been introduced and shown to be an effective treatment in many metabolic bone disorders, such as burosumab for hypophosphatemic rickets and asfotase alfa for hypophosphatasia. On the other hand, other disorders, such as nutritional rickets and skeletal fluorosis continue to be underrecognized in many regions of the world. Genetic disorders of collagen-elastin, such as osteogenesis imperfecta, Ehlers--Danlos syndrome and Marfan's syndrome are also associated with skeletal fragility, which can be misdiagnosed as caused by non-accidental trauma/child abuse.

SUMMARY

It is essential to provide early and accurate diagnosis and treatment for pediatric patients with metabolic bone disorders in order to maintain growth and development as well as prevent fractures and metabolic complications.

Combined microinvasive glaucoma surgery in osteogenesis imperfecta patient with refractory open angle glaucoma

Purpose

To report a case of refractory open angle glaucoma (POAG) in an osteogenesis imperfecta patient who was successfully treated with combination microinvasive glaucoma surgery: combined kahook blade goniotomy and ciliary sulcus suprachoroidal microtube insertion.

Observation

A 57-year-old woman with a history of osteoporosis, breast cancer, osteogenesis imperfecta, with uncontrolled POAG in right more than left. Anterior segment examination revealed thin blue sclera, the optic nerve examination revealed glaucomatous cupping with cup to disc ration of 0.9 in right and 0.7 in left. Her IOP on six (6) medications was 26 mmHg in the right eye. After discussion of the risks and benefits, she agreed to undergo combined kahook blade goniotomy and ciliary sulcus suprachoroidal microtube insertion surgery to lower her intraocular pressure. Her IOP at 6 months follow up was 13 in the right eye and a decrease number of medications from six (6) to three.

Conclusion and importance

Patients with OI have homogenously thinner sclera and conjunctiva which pose a challenge to traditional subconjunctival surgical methods. Combined kahook blade goniotomy and ciliary sulcus suprachoroidal microtube insertion surgery are bleb sparing operations that enhances aqueous outflow to the aqueous veins and supraciliary space to lower intraocular pressure.

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Combined microinvasive surgery.

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Osteogenesis imperfecta.

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Refractory open angle glaucoma.

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Glaucoma, kahook blade goniotomy.

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Suprachoroidal microtube.

Comparison of Standard Versus Accelerated Corneal Collagen Cross-Linking for Keratoconus: A Meta-Analysis

Purpose

To systematically compare epithelial-off standard (SCXL) to accelerated corneal collagen cross-linking (ACXL) for the treatment of keratoconus.

Methods

PubMed, Embase, the Cochrane Library, and the US trial registry were searched for trials comparing SCXL and ACXL for keratoconus up to October 2017. Standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated. Primary outcomes were changes in uncorrected distance visual acuity, maximum keratometry (Kmax), and mean keratometry (mean K). Secondary outcomes were changes in corrected distance visual acuity, mean refractive spherical equivalent, central corneal thickness (CCT), and endothelial cell density (ECD).

Results

Eleven trials were included. For primary outcomes, SCXL showed a greater reduction in Kmax (SMD 0.32; 95% CI 0.16, 0.48) than ACXL. For secondary outcomes, the decrease in CCT (SMD 0.32; 95% CI 0.03, 0.61) and ECD (SMD 0.26; 95% CI 0.06, 0.46) was less with ACXL than with SCXL. For the other outcomes, there were no statistically significant differences.

Conclusions

SCXL has a greater effect in terms of reduction in Kmax than ACXL, while ACXL induces less reduction in CCT and ECD than SCXL. Further well-designed randomized controlled trials comparing ACXL and SCXL are indicated.

Osteogenesis imperfecta and the teeth, eyes, and ears-a study of non-skeletal phenotypes in adults

Osteogenesis imperfecta (OI) is a disease causing bone fragility; however, it potentially affects all organs with a high content of collagen, including ears, teeth, and eyes. The study is cross-sectional and compares non-skeletal characteristics in adults with OI that clinicians should be aware of when caring for patients with OI.

INTRODUCTION

Osteogenesis imperfecta (OI) is a hereditary connective tissue disorder. The skeletal fragility is pronounced; however, OI leads to a number of extra-skeletal symptoms related to the ubiquity of collagen type 1 throughout the human body. The vast majority of knowledge is derived from studies performed in the pediatric population. Thus, we aimed to investigate the nature and prevalence of ophthalmologic, odontologic, and otologic phenotypes in an adult population with OI.

METHODS

The study population comprises 85 Danish OI patients (age 44.9 ± 15.9 years). Fifty-eight patients had OI type I, 12 OI type III, and 15 OI type IV according to the classification by Sillence. Audiometric evaluations and dental examinations were performed in 62 and 73 patients, respectively. Ophthalmologic investigations were performed in 64 patients, including measurements of the central corneal thickness.

RESULTS

All patients, except two, had corneal thickness below the normal reference value. Patients with OI type I and patients with a quantitative collagen defect had thinner corneas compared to patients with OI type III and other patients with a qualitative collagen defect. One patient in this cohort was diagnosed with and treated for acute glaucoma. Dentinogenesis imperfecta was diagnosed in one fourth of the patients, based on clinical and radiographic findings. This condition was predominately seen in patients with moderate to severe OI. Hearing loss requiring treatment was found in 15 of 62 patients, of whom three were untreated. The most prevalent type of hearing loss (HL) was sensorineural hearing loss, whereas conductive HL was solely seen in patients with OI type III. The patients with the most severe degrees of HL were patients with mild forms of OI. Age was associated with increased HL.

CONCLUSION

Although significant health problems outside the skeleton are frequent in adult patients with OI, the patients are not consistently monitored and treated for their symptoms. Clinicians treating adult patients with OI should be aware of non-skeletal health issues and consider including regular interdisciplinary check-ups in the management plan for adult OI patients.

Multimodal imaging in a young male with osteogenesis imperfecta complicated with choroidal neovascularization

Purpose:

To evaluate the role of multimodal imaging in the diagnosis and monitoring of patients with osteogenesis imperfecta complicated with choroidal neovascularization.

Case report:

A 28-year-old man, diagnosed with osteogenesis imperfecta, was referred 2 months after the appearance of central scotoma and metamorphopsia in the right eye. The patient underwent a complete ophthalmological evaluation including visual acuity examination as well as ophthalmoscopy, spectral-domain optical coherence tomography, optical coherence tomography angiography, fundus autofluorescence imaging, fluorescein angiography and microperimetry. Complete examination revealed macular lacquer crack with subretinal haemorrhage. A further investigation with spectral-domain optical coherence tomography and fluorescein angiography revealed the presence of choroidal neovascularization without clear activity associated to the lacquer crack. After a 1-month follow-up, both visual acuity and retinal sensitivity improved spontaneously.

Conclusion:

Collagen deficiency of osteogenesis imperfecta leads to fragility of the Bruch’s membrane; tension forces probably act at this level determining ruptures with bleeding and choroidal neovascularization formation. Multimodal imaging and functional evaluation are needed to assess retinal alterations in patients with osteogenesis imperfecta, whereas treatment of choroidal neovascularization should be reserved only for active lesion to prevent evolution and visual acuity decrement.

Functional relevance for central cornea thickness-associated genetic variants by using integrative analyses

Background

The genetic architecture underlying central cornea thickness (CCT) is far from understood. Most of the CCT-associated variants are located in the non-coding regions, raising the difficulty of following functional characterizations. Thus, integrative functional analyses on CCT-associated loci might benefit in overcoming these issues by prioritizing the hub genes that are located in the center of CCT genetic network.

Methods

Integrative analyses including functional annotations, enrichment analysis, and protein-protein interaction analyses were performed on all reported CCT GWAS lead SNPs, together with their proxy variants. Functional annotations were conducted by CADD, GWAVA, and Eigen. Enrichment analyses for CCT-associated genes were performed using ToppGene suite. Protein-protein interaction network and gene co-expression analyses were performed by GeneMANIA.

Results

Functional annotations prioritized eight genes (ADAMSTS6, ARID5B, FOXO1, AKAP13, COL4A3, COL8A2, TBL1XR1, and KCMB2) harboring SNPs with strong evidence of regulatory potential. It was also shown that CCT-associated genes were significantly enriched in collagen-related pathways and the phenotype of keratoconus, and some of them were found to be involved in one interaction network.

Conclusion

This study revealed the hub genes that were located in the center of CCT genetic network and provided a new insight into the genetic regulation underlying CCT GWAS findings.

Corneal Manifestations of Systemic Sclerosis

Purpose: Corneal involvement in systemic sclerosis (SSc) is rare, but due to rich collagen composition cornea is especially vulnerable to connective tissue diseases. Therefore, our aim was to evaluate corneal parameters of SSc patients. Methods: The study included 32 SSc patients and 39 control subjects with no ocular symptoms or ocular surface disorders. All study participants underwent Pentacam evaluation and objective signs of dry eye disease (DED), and clinical parameters were evaluated. Results: All pachymetric values, most of the corneal front surface, corneal volume, as well as anterior chamber depth measurements were significantly lower in the SSc group than in the control group (p < 0.05). Significant negative correlation was found between corneal parameters and age on the one hand, and disease duration on the other. Conclusions: Early recognition of corneal impairment, a possible extraintestinal manifestation of SSc, should be included in the check-up of the disease in order to reduce sight-threatening complications.

Bilateral papilledema in a child with osteogenesis imperfecta

Background

To present a female child patient with osteogenesis imperfecta who had bilateral papilledema.

Case presentation

A twelve-year-old girl with osteogenesis imperfecta was referred to our clinic. Bilateral best corrected visual acuity of the patient was 5/10 (corrected with +3.50 for right eye, +5.00 for left eye) with a standard Snellen scale at a distance of a 6 m. Anterior chamber, iris and lens examination of both of her eyes were unremarkable. In her fundus examination, bilateral stage 2 papilledema and the wrinkles in papillomacular area were noticed. Optical coherence tomography images revealed the macular pucker and thickening in the retinal nerve fibre layers of both eyes. Computed tomography images revealed that there were ossifications in the optic chiasma and occlusion in all periorbital sinus areas.

Conclusion

Osteogenesis imperfecta is a rare, autosomal dominant connective tissue disorder characterised by bone fractures, deafness and blue sclera. We would like to draw attention to the clinical course of our patient with computed tomography, optical coherence tomography and visual field findings.

Corneal Sublayers Thickness in Patients With Mitral Valve Prolapse

OBJECTIVES

The aim of this study was to compare the thickness of each corneal sublayer in patients with mitral valve prolapse (MVP) and healthy individuals.

METHODS

A total of 38 eyes from 38 patients with MVP and 34 eyes from 34 age- and sex-matched healthy individuals were included in this study. The thickness of the corneal epithelium, Bowman layer, stroma, and Descemet membrane-endothelium complex were measured on the central cornea (i.e., corneal apex) and both the inferior and superior halves of the cornea with anterior segment module of spectral domain optical coherence tomography.

RESULTS

No statistically significant differences emerged between the study and control groups in terms of Bowman layer thickness in the central cornea and the cornea's superior half (P=0.092 and P=0.128, respectively). However, in the inferior half of the cornea, Bowman layer thickness among patients with MVP was 11.95±2.34 μm (range 7-16 μm) and in the control group was 13.03±1.62 μm (range 10-16 μm), which made for a statistically significant difference (P=0.025).

CONCLUSIONS

Our study revealed thinning of Bowman layer in the inferior half of the cornea in patients with MVP.

Advances in the Classification and Treatment of Osteogenesis Imperfecta

Osteogenesis imperfecta (OI) is a rare disorder of type 1 collagen with 13 currently identified types attributable to inherited abnormalities in type 1 collagen amount, structure, or processing. The disease is characterized by an increased susceptibility to bony fracture. In addition to the skeletal phenotype, common additional extraskeletal manifestations include blue sclerae, dentinogenesis imperfecta, vascular fragility, and hearing loss. Medical management is focused on minimizing the morbidity of fractures, pain, and bone deformities by maximizing bone health. Along with optimizing Vitamin D status and calcium intake and physical/occupational therapy, individualized surgical treatment may be indicated. Pharmacological therapy with bisphosphonate medications is now routinely utilized for moderate to severe forms and appears to have a good safety profile and bone health benefits. New therapies with other anti-resorptives as well as anabolic agents and transforming growth factor (TGF)β antibodies are in development. Other potential treatment modalities could include gene therapy or mesenchymal cell transplant. In the future, treatment choices will be further individualized in order to reduce disease morbidity and mortality.

WNT10A exonic variant increases the risk of keratoconus by decreasing corneal thickness

Keratoconus is a degenerative eye condition which results from thinning of the cornea and causes vision distortion. Treatments such as ultraviolet (UV) cross-linking have proved effective for management of keratoconus when performed in early stages of the disease. The central corneal thickness (CCT) is a highly heritable endophenotype of keratoconus, and it is estimated that up to 95% of its phenotypic variance is due to genetics. Genome-wide association efforts of CCT have identified common variants (i.e. minor allele frequency (MAF) >5%). However, these studies typically ignore the large set of exonic variants whose MAF is usually low. In this study, we performed a CCT exome-wide association analysis in a sample of 1029 individuals from a population-based study in Western Australia. We identified a genome-wide significant exonic variant rs121908120 (P = 6.63 × 10(-10)) in WNT10A. This gene is 437 kb from a gene previously associated with CCT (USP37). We showed in a conditional analysis that the WNT10A variant completely accounts for the signal previously seen at USP37. We replicated our finding in independent samples from the Brisbane Adolescent Twin Study, Twin Eye Study in Tasmania and the Rotterdam Study. Further, we genotyped rs121908120 in 621 keratoconus cases and compared the frequency to a sample of 1680 unscreened controls from the Queensland Twin Registry. We found that rs121908120 increases the risk of keratoconus two times (odds ratio 2.03, P = 5.41 × 10(-5)).

Scleral perforations during routine traction test in a patient with osteogenesis imperfecta

Osteogenesis imperfecta comprises a rare group of genetic disorders caused by abnormal collagen that results in increased bone fragility and other sequelae. We describe a 37-year-old woman with osteogenesis imperfecta in whom two full-thickness scleral perforations were created by adjacent teeth of 0.5 mm forceps during traction testing while undergoing routine strabismus surgery. This case reviews the ocular findings of osteogenesis imperfecta and highlights the potential risk of ocular surgical complications in these patients.

Enrichment of pathogenic alleles in the brittle cornea gene, ZNF469, in keratoconus

Keratoconus, a common inherited ocular disorder resulting in progressive corneal thinning, is the leading indication for corneal transplantation in the developed world. Genome-wide association studies have identified common SNPs 100 kb upstream of ZNF469 strongly associated with corneal thickness. Homozygous mutations in ZNF469 and PR domain-containing protein 5 (PRDM5) genes result in brittle cornea syndrome (BCS) Types 1 and 2, respectively. BCS is an autosomal recessive generalized connective tissue disorder associated with extreme corneal thinning and a high risk of corneal rupture. Some individuals with heterozygous PRDM5 mutations demonstrate a carrier ocular phenotype, which includes a mildly reduced corneal thickness, keratoconus and blue sclera. We hypothesized that heterozygous variants in PRDM5 and ZNF469 predispose to the development of isolated keratoconus. We found a significant enrichment of potentially pathologic heterozygous alleles in ZNF469 associated with the development of keratoconus (P = 0.00102) resulting in a relative risk of 12.0. This enrichment of rare potentially pathogenic alleles in ZNF469 in 12.5% of keratoconus patients represents a significant mutational load and highlights ZNF469 as the most significant genetic factor responsible for keratoconus identified to date.

The genetics of keratoconus

Keratoconus is a bilateral, non-inflammatory corneal ectasia characterized by progressive conical thinning and protrusion of the cornea. Its etiology has long been believed to be multifactorial, with environmental, behavioral, and genetic factors all contributing to the disease process. This review focuses specifically on examining the evidence that supports a genetic basis for keratoconus.

Increased central corneal thickness in patients with Turner syndrome

PURPOSE

To evaluate central corneal thickness (CCT) values in patients with Turner syndrome (TS) and compare these values with healthy subjects.

METHODS

A total of 31 subjects with TS and 67 age- and sex-matched healthy subjects made up the study and control group, respectively. The CCT values were measured by an ultrasound pachymeter in this cross-sectional prospective study. The ocular findings were recorded. We also evaluated to effect of karyotype analysis, recombinant growth hormone therapy (GHT), and mean duration of treatment on the CCT parameter in patients with TS.

RESULTS

The mean CCT values were 582.0 ± 40.8 µm (490-648) in the TS and 549.1 ± 34.6 µm (494-601) in the healthy group. The mean intraocular pressure (IOP) by Goldmann applanation tonometry was 16.3 ± 3.1 mm Hg (9-22) in the TS and 15.2 ± 2.5 mm Hg (10-21) in the healthy group. The mean CCT value was significantly higher in the TS group (p<0.05) but there was no statistically significant difference between the 2 groups for IOP (p>0.05). There was also no significant difference for CCT regarding the karyotype, GHT use, and mean duration of treatment in patients with TS (p>0.05).

CONCLUSIONS

Central corneal thickness values should be considered during measurement of IOP in individuals with TS as these values may be higher than in healthy subjects.

Genetic association of COL5A1 variants in keratoconus patients suggests a complex connection between corneal thinning and keratoconus

PURPOSE

Single nucleotide polymorphisms (SNPs) located near or within the COL5A1 gene, at 9q34.2-q34.3 chromosomal region have been reported in association with central corneal thickness (CCT). Using family linkage analysis, we identified a keratoconus susceptibility locus at 9q34. These findings led us to perform an association study between COL5A1 variation and keratoconus susceptibility.

METHODS

A Caucasian case-control cohort of 222 keratoconus patients and 3324 controls was selected as the discovery panel. An independent case-control panel of 304 cases and 518 controls and a family panel of 186 subjects were replicated for genotyping and association. Forty-four SNPs (21 for discovery and 23 for fine-mapping) spanning 300 kilobases in and around COL5A1 were genotyped and tested for genetic association. Logistic regression models implemented in PLINK were used to test for association in case controls. Generalized estimating equation models accounting for familial correlations implemented in genome-wide interaction analyses with family data were used for association testing in families.

RESULTS

Two CCT associated SNPs (rs1536482 and rs7044529 near and within COL5A1) were identified in the keratoconus discovery cohort (P values of 6.5 × 10(-3) and 7.4 × 10(-3)). SNP rs1536482 was replicated in the second case-control sample (P = 0.02), and SNP rs7044529 was replicated in a keratoconus family panel (P = 0.03). Meta P values of rs1536482 and rs7044529 in the keratoconus cohorts were 1.5 × 10(-4) (odds ratio [OR] = 1.30) and 2.9 × 10(-3) (OR = 1.39). After Bonferroni correction, the association of SNP rs1536482 remained significant (P = 6.5 × 10(-3)).

CONCLUSIONS

SNPs in the COL5A1 region, which regulate normal variation in CCT, may play a role in the thinning associated with keratoconus.

The impairment of lysyl oxidase in keratoconus and in keratoconus-associated disorders

Keratoconus (KC) is an eye disease characterized by the progressive thinning and protrusion of the cornea, which results in the loss of visual acuity. This disorder remains poorly understood, although recent studies indicate the involvement of genetic and environmental factors. Recently, we have found that the distribution of the cross-linking enzyme lysyl oxidase (LOX) is markedly decreased in about 63 % of keratoconic specimens. Similarly, LOX activity is significantly reduced by 38 % compared to control tissue. Nearly 70 systemic disorders have been reported in association with KC, most of them affecting the extracellular matrix. In this review we attempted to ascertain whether any KC-associated diseases exhibit signs that may reflect LOX impairment. We hypothesized that very similar changes in the extracellular matrix, particularly at the level of collagen metabolism, including LOX impairment in mitral leaflets, may reflect an association between KC and mitral valve prolapse. Moreover, this putative association is supported by the high frequency of Down syndrome in both diseases. Among other disorders that have been found to coincide with KC, we did not find any in which the LOX enzyme may be directly or indirectly impaired. On the other hand, in cases where KC is present along with other connective tissue disorders (Marfan syndrome, Ehlers-Danlos syndrome and others), KC may not arise as a localized manifestation, but rather may be induced as the result of a more complex connective tissue disorder.

Genome-wide association analyses identify multiple loci associated with central corneal thickness and keratoconus

Central corneal thickness (CCT) is associated with eye conditions including keratoconus and glaucoma. We performed a meta-analysis on >20,000 individuals in European and Asian populations that identified 16 new loci associated with CCT at genome-wide significance (P < 5 × 10(-8)). We further showed that 2 CCT-associated loci, FOXO1 and FNDC3B, conferred relatively large risks for keratoconus in 2 cohorts with 874 cases and 6,085 controls (rs2721051 near FOXO1 had odds ratio (OR) = 1.62, 95% confidence interval (CI) = 1.4-1.88, P = 2.7 × 10(-10), and rs4894535 in FNDC3B had OR = 1.47, 95% CI = 1.29-1.68, P = 4.9 × 10(-9)). FNDC3B was also associated with primary open-angle glaucoma (P = 5.6 × 10(-4); tested in 3 cohorts with 2,979 cases and 7,399 controls). Further analyses implicate the collagen and extracellular matrix pathways in the regulation of CCT.

[Osteogenesis imperfecta and glaucoma. A case report]

Osteogenesis imperfecta (OI) is a connective tissue metabolic disorder with autosomal inheritance. Ocular involvement includes blue sclera, myopia, glaucoma and keratoconus in addition to bone synthesis defects. We report the case of a male patient with OI who suffered from progressive visual field defects and advanced glaucomatous optic atrophy and underwent trabeculectomy on both eyes. Intraocular pressures (IOP) of 7-11 mmHg were measured 1 year postoperatively. This report illustrates peculiarities in the surgical therapy of open angle glaucoma in patients with OI as well as the options for complication management.

Intravitreal bevacizumab for treatment of choroidal neovascularization associated with osteogenesis imperfecta

A 12-year-old girl, diagnosed of osteogenesis imperfecta, presented with sudden visual loss in the left eye. Investigations revealed an active choroidal neovascular membrane. She underwent treatment with intravitreal Bevacizumab (1.25 mg/0.05 ml). Follow-up at 1 month revealed the development of lacquer crack running through the macula, underlying the fovea. The patient received two re-treatments at 1-month intervals, following which the choroidal neovascularization (CNV) regressed completely. However, further progression of lacquer cracks was noted. At the last follow-up, 6 months following the last injection, the fundus remained stable and vision was maintained at 20/200. Considering the natural history of the disease and the increased risk of rupture of the Bruch's membrane in such eyes, the possible complication of a lacquer crack developing must be borne in mind, before initiating treatment.

Central corneal thickness in patients with systemic sclerosis: a controlled study

PURPOSE

To compare the central corneal thickness (CCT) of patients with systemic sclerosis (SSc) and control subjects.

METHODS

The study group comprised 37 consecutive patients with SSc, and the control group comprised 23 healthy individuals similar in age and sex. CCT value was measured by ultrasound pachymetry.

RESULTS

In the SSc group, the mean CCT in the right eye was 534.9 ± 33.5 μm and 536.9 ± 32.4 μm in the left eye. In the control group, the mean CCT was 533.0 ± 32.9 μm in the right eye and 533.1 ± 33.6 μm in the left eye. The mean CCT was not significantly different in the SSc group compared with the control group for both the right (P = 0.83) and left (P = 0.67) eyes.

CONCLUSIONS

CCT measurements do not significantly differ in patients with SSc compared with healthy control subjects.

Osteogenesis Imperfecta: A Review with Clinical Examples

Osteogenesis imperfecta (OI) is characterized by susceptibility to bone fractures, with a severity ranging from subtle increase in fracture frequency to prenatal fractures. The first scientific description of OI dates from 1788. Since then, important milestones in OI research and treatment have, among others, been the classification of OI into 4 types (the 'Sillence classification'), the discovery of defects in collagen type I biosynthesis as a cause of most cases of OI and the use of bisphosphonate therapy. Furthermore, in the past 5 years, it has become clear that OI comprises a group of heterogeneous disorders, with an estimated 90% of cases due to a causative variant in the COL1A1 or COL1A2 genes and with the remaining 10% due to causative recessive variants in the 8 genes known so far, or in other currently unknown genes. This review aims to highlight the current knowledge around the history, epidemiology, pathogenesis, clinical/radiological features, management, and future prospects of OI. The text will be illustrated with clinical descriptions, including radiographs and, where possible, photographs of patients with OI.

Ethnic and mouse strain differences in central corneal thickness and association with pigmentation phenotype

The cornea is a transparent structure that permits the refraction of light into the eye. Evidence from a range of studies indicates that central corneal thickness (CCT) is strongly genetically determined. Support for a genetic component comes from data showing significant variation in CCT between different human ethnic groups. Interestingly, these studies also appear to show that skin pigmentation may influence CCT. To validate these observations, we undertook the first analysis of CCT in an oculocutaneous albinism (OCA) and Ugandan cohort, populations with distinct skin pigmentation phenotypes. There was a significant difference in the mean CCT of the OCA, Ugandan and Australian-Caucasian cohorts (Ugandan: 517.3±37 µm; Caucasian: 539.7±32.8 µm, OCA: 563.3±37.2 µm; p<0.001). A meta-analysis of 53 studies investigating the CCT of different ethnic groups was then performed and demonstrated that darker skin pigmentation is associated with a thinner CCT (p<0.001). To further verify these observations, we measured CCT in 13 different inbred mouse strains and found a significant difference between the albino and pigmented strains (p = 0.008). Specific mutations within the melanin synthesis pathway were then investigated in mice for an association with CCT. Significant differences between mutant and wild type strains were seen with the nonagouti (p<0.001), myosin VA (p<0.001), tyrosinase (p = 0.025) and tyrosinase related protein (p = 0.001) genes. These findings provide support for our hypothesis that pigmentation is associated with CCT and identifies pigment-related genes as candidates for developmental determination of a non-pigmented structure.

Central corneal thickness in children and adolescents with pediatric glaucoma and eye disorders at risk of developing glaucoma

BACKGROUND

To investigate central corneal thickness (CCT) in children with glaucoma and at risk for glaucoma.

METHODS

The study included 139 children with glaucoma: 66 at risk for glaucoma (ie, aphakia, aniridia, or uveitis) and 66 normal children. CCT was measured by ultrasound pachymetry and intraocular pressure (IOP) by applanation. Analysis of variance was used to compare CCT between groups. Correlation analysis assessed associations between CCT and ocular factors including spherical equivalent, cup-to-disc ratio, glaucoma medications, and number of intraocular surgeries.

RESULTS

CCT was significantly higher for 141 eyes with glaucoma (mean: 0.598 mm, P < .001) and 76 eyes at risk for glaucoma (mean: 0.604 mm, P = .001) than for 66 normal eyes (mean: 0.558 mm). No significant difference was observed between at-risk (P = .989) and glaucoma eyes. Eyes with aphakia (0.653 mm) and aniridia (0.639 mm) had the thickest CCT values. Thinnest CCT was found in anterior segment dysgenesis and uveitis (mean: 0.541 mm). A significant positive correlation between CCT and spherical equivalent was found for glaucoma (r = 0.413; P < .001) and at-risk (r = 0.412; P < .0003) eyes, and between CCT and intraocular surgery for at-risk eyes (P = .0066). A significant negative correlation was found between CCT and cup-to-disc ratio for glaucoma eyes (r = -0.223; P = .01).

CONCLUSION

This is the largest series of CCT in pediatric glaucoma and related disorders. The data suggest caution in application of standard formulas for IOP-to-CCT correction when evaluating children with glaucoma because their mean CCT values extend far beyond values reported for normal eyes.

Acquired central corneal thickness increase following removal of childhood cataracts

PURPOSE

To evaluate central corneal thickness (CCT) in children with congenital/developmental cataracts before and after cataract removal, to correlate CCT with corneal diameters before cataract surgery in this same group, and to evaluate CCT over time in a separate group of children who were already aphakic or pseudophakic at study entry.

DESIGN

Longitudinal study.

METHODS

Children with cataract (Group 1, with pre-cataract-removal CCT) and aphakia/pseudophakia (Group 2, presenting after cataract removal) were included. CCT measurements were performed using ultrasound pachymetry. Normal fellow eyes of unilaterally affected cases served as controls. In bilateral cases, right eyes were used for analyses.

RESULTS

Group 1 comprised 66 children. Before cataract surgery, unilateral cases (n = 31) showed similar CCT and strong association between the affected and fellow eyes (552.0 ± 32.9 μm vs 550.9 ± 40.4 μm, respectively; r(2) = 0.71, P = .0001). After cataract surgery, affected eyes (n = 13) showed mean CCT increase of 29.7 ± 43.1 μm (P = .03) while fellow eyes remained unchanged. Similarly, before cataract surgery, bilateral cases (n = 35) showed similar CCT between the right and left eyes. After cataract surgery, mean CCT increase was 27.4 ± 39.4 μm for first operated eyes of bilateral cases (n = 17, P = .01). Group 2 comprised 50 aphakic/pseudophakic children lacking pre-cataract-removal CCT. CCT was higher in eyes with glaucoma vs those without, at both first and last measurements (ΔCCT 58.9 ± 27.0 μm at first examination, P = .034, and 56.4 ± 27.1 μm at last examination, P = .043, respectively). There was no statistically significant CCT change over the study interval (median 28 months) for either Group 2 eyes with or those without glaucoma.

CONCLUSIONS

CCT in children with cataracts increases after cataract surgery while the fellow eye remains stable. This increase seems to occur early after surgery, likely remaining stable thereafter, though glaucoma can accentuate the increase.

Common genetic variants near the Brittle Cornea Syndrome locus ZNF469 influence the blinding disease risk factor central corneal thickness

Central corneal thickness (CCT), one of the most highly heritable human traits (h² typically>0.9), is important for the diagnosis of glaucoma and a potential risk factor for glaucoma susceptibility. We conducted genome-wide association studies in five cohorts from Australia and the United Kingdom (total N = 5058). Three cohorts were based on individually genotyped twin collections, with the remaining two cohorts genotyped on pooled samples from singletons with extreme trait values. The pooled sample findings were validated by individual genotyping the pooled samples together with additional samples also within extreme quantiles. We describe methods for efficient combined analysis of the results from these different study designs. We have identified and replicated quantitative trait loci on chromosomes 13 and 16 for association with CCT. The locus on chromosome 13 (nearest gene FOXO1) had an overall meta-analysis p-value for all the individually genotyped samples of 4.6×10⁻¹⁰. The locus on chromosome 16 was associated with CCT with p = 8.95×10⁻¹¹. The nearest gene to the associated chromosome 16 SNPs was ZNF469, a locus recently implicated in Brittle Cornea Syndrome (BCS), a very rare disorder characterized by abnormal thin corneas. Our findings suggest that in addition to rare variants in ZNF469 underlying CCT variation in BCS patients, more common variants near this gene may contribute to CCT variation in the general population.

Central corneal thickness (CCT) is an important eye measurement. It has been considered as a prognosticator for the development of glaucoma, with a thin cornea potentially increasing the risk of developing a subtype known as open-angle glaucoma. CCT is highly heritable, yet its genetic determinants are poorly characterized. We have revealed two loci near gene FOXO1 and ZNF469 associated with CCT in this multi-stage genome-wide association study examining over 5,000 samples. It is of particular interest that, while rare mutations in ZNF469 cause Brittle Cornea Syndrome, more common variants near this gene also contribute to CCT variation in the general population. Furthermore, given the relation between CCT and glaucoma, results from our CCT studies will implement the search for the disease-susceptibility genes of glaucoma.

Relation between central corneal thickness and intraocular pressure in Punjabi population

OBJECTIVE

The motive of this study was to determine the variation of central corneal thickness (CCT) in the Punjabi population and to examine its relationship with intraocular pressure (IOP) using a non-contact tonometer. The study and results emphasize the effects of age, sex and refraction on this relationship, which is important for the diagnosis and prevention of glaucoma in adequate time.

METHODS

The study design was a cross-sectional, population-based survey. The participants were 279 females and 253 males of Punjab Province, India, in the age group of 21-70 years. The CCT was measured using an ultrasonic pachymeter, and the IOP was measured using an air-puff tonometer in all subjects.

RESULTS

The mean values of CCT and IOP were observed to vary imprecisely with age. The measurement of both parameters was also affected by sex and refraction. The linear regression analysis suggests that the mean value of CCT grows progressively with increasing value of mean IOP. A significant positive correlation was identified between CCT and IOP in the age group of 21-70 years. The authors inferred that this correlation value varies prominently with age for both sexes, which needs to be investigated further.

CONCLUSIONS

The authors suggest that CCT is a noteworthy source of variation in IOP measurements for males as well as females belonging to different age groups, when assessing IOP as a risk for glaucoma in the Punjabi population.

Intraocular pressure change in orbital disease

Intraocular pressure change has been found concurrent with many orbital pathologies, particularly those involving proptosis. The objective of this review is to offer an inclusive classification of orbital disease-related intraocular pressure change, not only for oculoplastics and glaucoma specialists, but also for general ophthalmologists. Various orbital conditions associated with increased intraocular pressure and glaucoma are comprehensively summarized, and pathophysiology, clinical manifestations, and treatment options of these diseases are discussed. Graves disease, arterio-venous shunts, trauma, and orbital neoplasia, and other common conditions are discussed in detail; less frequent syndromes such as orbitocraniofacial deformities, phakomatoses, and mucopolysaccharidoses are included for the sake of comprehensiveness, but discussed less extensively.

Novel quantitative trait loci for central corneal thickness identified by candidate gene analysis of osteogenesis imperfecta genes

Osteogenesis imperfecta (OI) is a rare connective tissue disorder caused by mutations in the type I collagen genes, COL1A1 and COL1A2, and is characterised by low bone mass and bone fragility. In this study, we explored the relationship between type 1 collagen genes and the quantitative trait central corneal thickness (CCT). CCT was measured in a cohort of 28 Australian type I OI patients and mean CCT was found to be significantly lower compared to a normal population (P < 0.001). We then investigated CCT and corneal collagen fibril diameter and density in a mouse model of OI with a col1a2 mutation. Mean CCT was significantly lower in mutant mice (P = 0.002), as was corneal collagen fibril diameter (P = 0.034), whilst collagen fibril density was significantly greater in mutants (P = 0.034). Finally, we conducted a genetic study to determine whether common single nucleotide polymorphisms (SNPs) in COL1A1 and COL1A2 are associated with CCT variation in the normal human population. Polymorphism rs2696297 (P = 0.003) in COL1A1 and a three SNP haplotype in COL1A2 (P = 0.007) were all significantly associated with normal CCT variation. These data implicate type 1 collagen in the determination of CCT in both OI patients and normal individuals. This provides the first evidence of quantitative trait loci that influence CCT in a normal population and has potential implications for investigating genes involved in glaucoma pathogenesis, a common eye disease in which the severity and progression is influenced by CCT.

Increased central corneal thickness in children with cerebral palsy

PURPOSE

To evaluate central corneal thickness (CCT) values in children with cerebral palsy (CP).

METHODS

Sixty-seven children with CP and 58 healthy control children (125 children total) were enrolled into the study. The CCT value was measured by ultrasound pachymetry. The consecutive measurements were taken from the center of the cornea of each eye.

RESULTS

In the CP group, the mean CCT value was 568.46 +/- 31.94 microm in the right eye and 568.01 +/- 32.50 microm in the left eye. In the control group, the mean CCT value was 549.53 +/- 26.16 microm in the right eye and 549.62 +/- 27.58 microm in the left eye. The CCT value was significantly higher in the CP group than in the control group for both eyes (P < 0.001). There was no statistically significant difference between the right and left eyes of children with CP and intellectual disability (ID) and those with CP and no ID (P = 0.344 and 0.076, respectively).

CONCLUSIONS

Children with CP had an increased CCT compared with healthy control subjects. There was however no significant difference in CCT values between the children with and without ID in our CP group.

Apparent autosomal dominant keratoconus in a large Australian pedigree accounted for by digenic inheritance of two novel loci

Keratoconus is a debilitating ocular disease characterised by progressive asymmetrical thinning of the cornea, the clear covering at the front of the eye. The resulting protrusion of the cornea results in severe refractive error, in the most severe cases requiring corneal grafting. It is a complex disease with a genetic component. Despite several reports of linked loci, major gene identification has been elusive. A genome-wide linkage scan in a large Australian pedigree with apparent autosomal dominant keratoconus was conducted using the Affymetrix 10K SNP chip and two regions of linkage identified. Functional candidate genes from within both linkage peaks were assessed for corneal expression and screened for mutations in affected family members. Equal evidence of linkage was detected to both 1p36.23-36.21 and 8q13.1-q21.11 with LOD scores of 1.9. Analysis of both loci concurrently suggests digenic linkage with two-locus LOD score of 3.4. All affected individuals carry identical haplotypes at both loci. Carriers of either linked haplotype without the other do not have keratoconus. No mutations were identified in the following candidate genes expressed in the cornea: ENO1, CTNNBIP1, PLOD1, UBIAD1, SPSB1 or TCEB1. Although the pedigree appears to demonstrate simple autosomal dominant inheritance, the disorder is actually genetically complex. This pedigree may provide a link between inherited forms of keratoconus and sporadic cases.

Central corneal thickness and Diaton transpalpebral tonometry

BACKGROUND

To examine the effects of central corneal thickness on the measures obtained from transpalpebral tonometry (Diaton), and to identify correlations between intraocular pressure (IOP) measurements with Diaton and the Goldmann applanation tonometer (GAT).

METHODS

In this cross-sectional study, 162 eyes of 81 participants were included. Intraocular pressure measurements were obtained in all patients using Diaton and GAT. Central corneal thickness was determined by ultrasound pachymetry. The participants were stratified by corneal thickness: group I <530 microm (n = 56), group II 530-560 microm (n = 65), and group III >560 microm (n = 41).

RESULTS

There were moderate correlations between IOP readings obtained using the Diaton and corrected GAT (C-GAT) (r = 0.303; P < 0.0001), and between corrected Diaton (C-Diaton), and C-GAT (r = 0.399; P < 0.0001). The mean Diaton tonometer readings were lower than C-GAT measurements (Diaton-corrected GAT mean difference, 0.9 +/- 3.8 mmHg; c-Diaton-corrected GAT mean difference, 0.7 +/- 3.5 mmHg). Differences were detected between the groups of patients for the GAT values [2.4 +/- 3.6 mmHg for those with the thinnest corneas (<530 microm), 0.7 +/- 3.6 mmHg for those with moderate corneas (between 531 microm and 560 microm), and -0.6 +/- 3.6 mmHg for those with the thickest (>560 microm) corneas], whereas a significantly lower difference (0.9 +/- 3.8 mmHg) was noted for the Diaton values of all individuals.

CONCLUSIONS

The Diaton measurements show moderate correlation with those provided by applanation tonometry. The Diaton tonometer seems to be more affected by the corneal thickness, especially in the thinnest corneas.