Epidemiologic study of myopia in a population of schoolchildren in Tunisia.

BACKGROUND: Uncorrected refractive error has recently been identified as the leading cause of visual impairment in children worldwide. The prevalence of myopia is increasing. Determination of the epidemiology of myopia is important to develop screening strategy. PURPOSE: to estimate the prevalence and the degree of severity of myopia among primary schoolchildren in Tunisia and to assess its effect on school performance. METHODS: A random cluster design was used to recruit children from primary schools across urban and rural settings in Tunisia, during 2009 to 2012. A total of 6192 students aged 6 to 14 years old were enrolled. Students with visual acuity of 9/10 or worse underwent a complete ophthalmic examination, and cycloplegic autorefraction was used to determine refractive error. Myopia was defined as a spherical equivalent (SE) of - 0.50 dioptre (D) or worse. We also searched for a possible relation between uncorrected myopia and academic failure. RESULTS: The prevalence of myopia was 3.71%. Mean and SD of spherical equivalent was -3,10 ± 0,86 D. The myopia rate increased significantly with age (p=0.04), but was not significantly related to gender (p=0.823). There was no significant association between the student's area of residence and myopia (p=0.932). 85.21% of myopic students experienced unsatisfactory academic performances. CONCLUSION: The present study reveals the prevalence of myopia among schoolchildren in Tunisia. The high rate of academic failure in myopic schoolchildren emphasizes an unmet need for its screening and its correction.

Whole exome sequencing identifies mutations in Usher syndrome genes in profoundly deaf Tunisian patients.

Usher syndrome (USH) is an autosomal recessive disorder characterized by combined deafness-blindness. It accounts for about 50% of all hereditary deafness blindness cases. Three clinical subtypes (USH1, USH2, and USH3) are described, of which USH1 is the most severe form, characterized by congenital profound deafness, constant vestibular dysfunction, and a prepubertal onset of retinitis pigmentosa. We performed whole exome sequencing in four unrelated Tunisian patients affected by apparently isolated, congenital profound deafness, with reportedly normal ocular fundus examination. Four biallelic mutations were identified in two USH1 genes: a splice acceptor site mutation, c.2283-1G>T, and a novel missense mutation, c.5434G>A (p.Glu1812Lys), in MYO7A, and two previously unreported mutations in USH1G, i.e. a frameshift mutation, c.1195_1196delAG (p.Leu399Alafs*24), and a nonsense mutation, c.52A>T (p.Lys18*). Another ophthalmological examination including optical coherence tomography actually showed the presence of retinitis pigmentosa in all the patients. Our findings provide evidence that USH is under-diagnosed in Tunisian deaf patients. Yet, early diagnosis of USH is of utmost importance because these patients should undergo cochlear implant surgery in early childhood, in anticipation of the visual loss.

[Molecular exploration of the R91W (RPE65 gene) in Tunisian patients with early onset retinal dystrophy and early onset retinitis pigmentosa]. / Exploration moléculaire de la R91W (gene RPE65) chez des patients Tunisiens atteints de "Early Onset Retinal Dystrophy" et de la rétinopathie pigmentaire à age de début précoce.

BACKGROUND: Inherited retinal dystrophies are the major causes of blindness and visual impairment. Visual loss is due to neurosensory retinal and pigment epithelium cells degeneration. The most severe were Leber Congenital amaurosis (LCA), juvenile retinitis pigmentosa (RP) and early onset RP. The LCA and juvenile RP are called «Early Onset Retinal Dystrophy¼ (EORD). OBJECTIVE: Molecular exploration of the R91W (RPE65 gene) in Tunisian patients with Early Onset Retinal Dystrophy and early onset RP. METHODS: All patients underwent a complete ophthalmological and a general examinations. The R91W exploration was performed by direct sequencing of exon 4 of the RPE65 gene and enzyme digestion. RESULTS: Among 47 patients, 13 were from Nabeul. Twenty three had an EROD with a visual loss under the age of 2 years. Twenty four were with early onset RP and had these symptoms between the ages of 4 and 10 years. The best corrected visual acuity ranged from 2/10 to 1/60. Among the explored 94 chromosomes, the R91W (325C>T) allele was identified in heterozygous state in a sibling from Nabeul. The allele frequency was 2.12% (2/94). CONCLUSION: All our patients had severe forms of RP with a decrease in visual acuity and a wide advanced retinal degeneration. The R91W mutation (325C>T) was not the major cause of EORD and early onset RP among Tunisian patients.

[Epidemiologic study of hyperopia in schoolchildren in Tunisia]. / Profit épidémiologique de l'hypermétropie en milieu scolaire primaire en Tunise: à propos de 6192 enfants.

AIM: To study the epidemiological profile and the degree of severity of hyperopia in Tunisia primary school and to assess its effect on school performance. METHODS: A cross-sectional, descriptive survey was conducted among 6-14 aged Tunisian children attending primary urban and rural schools. A total of 6192 children were selected using stratified random cluster sampling. Cycloplegic refractive error was measured among all children with uncorrected visual acuity less than 9/10 or signs of astheniopia. Hyperopia was defined as spherical equivalent (SE) 2.0 diopters (D). We have also searched a possible relation between degree of severity of hyperopia and school performance. RESULTS: The prevalence of hyperopia was 2.61%. The spherical equivalent mean was + 3.73 ± 0.94 D. The mean age was 9.67 ± 0.44 years. This prevalence was 2.77% in boys and 2.47% in girls. 3.13% of students were living in urban areas and 1.42% in rural areas. The hyperopia rate decreased significantly with age (p = 0.021), but it was not significantly related to gender (p=0.54). The difference in the prevalence of hyperopia between urban and rural areas was not statistically significant (p = 0.067). There was no significant association between the degree of severity of hyperopia and school performance (p=0.41). CONCLUSION: In our study, the prevalence of hyperopia among schoolage children in Tunisia was 2.61%.The identification of this refractive error and its correction as soon as possible would ensure these children better visual comfort and a better education.

[Clinical characterization of the Stargardt disease and molecular exploration of the c.2041C>T mutation (ABCA4 gene) in Tunisian patients]. / Caractérisation clinique de la maladie de Stargardt et exploration moléculaire de la c.2041C>T (gène ABCA4) chez des patients tunisiens.

In order to charaterize the Stargardt disease, the molecular exploration of the c.2041C>T mutation (ABCA4 gene) and genotype phenotype correlation in Tunisian patients, seven unrelated propositi underwent a complete ophthalmological examination. The search for the mutation was performed by a direct sequencing after a specific amplification of exon 14 of the ABCA4 gene. Baseline, the average age of propositi was 20.7 ± 15 years and the sex-ratio was 1.3. The age of the visual impairment perception was 8.1 ± 3.2 years. In all patients, the loss of visual acuity was bilateral and ranged from "counting fingers" to 3.2/10. Fundus and retinal fluorescein angiography examination showed advanced stages of the disease. The allele frequency of the c.2041C>T was 28.5% (4/14). We have reported this mutation in two patients. Their average age at onset was 5 and a half years and the disease progression was rapid with a severe visual loss after 1 and 5 years. All patients had a juvenile macular dystrophy with flavimaculatus flecks. To our knowledge, we reported for the first time the homozygous state of the c.2041C>T mutation. Among homozygous patients, the age at onset was early, the loss of visual acuity was important and the prognosis was severe. Due to the severity of the phenotype and the high rate of inbreeding, genetic counseling for healthy heterozygotes is essential.

Posterior microphthalmia and nanophthalmia in Tunisia caused by a founder c.1059_1066insC mutation of the PRSS56 gene.

Congenital microphthalmia (CMIC) is a common developmental ocular disorder characterized by a small, and sometimes malformed, eye. Posterior microphthalmia (PM) and nanophthalmia are two rare subtypes of isolated CMIC characterized by extreme hyperopia due to short axial length and elevated lens/eye volume ratio. While nanophthalmia is associated with a reduced size in both anterior and posterior segments, PM involves a normal-size anterior chamber but a small posterior segment. Several genes encoding transcription and non-transcription regulators have been identified in different forms of CMIC. MFRP gene mutations have, for instance, been associated with nanophthalmia, and mutations in the recently identified PRSS56 gene have been linked to PM. So far, these two forms of CMIC have been associated with 9 mutations in PRSS56. Of particular interest, a c.1059_1066insC mutation has recently been reported in four Tunisian families with isolated PM and one Tunisian family with nanophthalmia. Here, we performed a genome-wide scan using a high density single nucleotide polymorphism (SNP) array 50 K in a large consanguineous Tunisian family (PM7) affected with PM and identified the same causative disease mutation. A total of 24 polymorphic markers spanning the PRSS56 gene in 6 families originating from different regions of Tunisia were analyzed to investigate the origin of the c.1059_1066insC mutation and to determine whether it arose in a common ancestor. A highly significant disease-associated haplotype, spanning across the 146 kb of the 2q37.1 chromosome, was conserved in those families, suggesting that c.1059_1066insC arose from a common founder. The age of the mutation in this haplotype was estimated to be around 1,850 years. The identification of such 'founder effects' may greatly simplify diagnostic genetic screening and lead to better prognostic counseling.

A novel homozygous R764H mutation in crumbs homolog 1 causes autosomal recessive retinitis pigmentosa.

PURPOSE: Retinitis pigmentosa (RP; MIM 268000) is a hereditary disease characterized by poor night vision and progressive loss of photoreceptors, eventually leading to blindness. This degenerative process primarily affects peripheral vision due to the loss of rods. Autosomal recessive RP (arRP) is clinically and genetically heterogeneous. It has been associated with mutations in different genes, including CRB1 (crumbs homolog 1). The aim of this study was to determine the causative gene in a Tunisian patient with arRP born to non-consanguineous parents. METHODS: Four accessible family members were included. They underwent full ophthalmic examination with best-corrected Snellen visual acuity, fundus photography and fluorescein angiography. Haplotype analysis was used to evaluate homozygosity in the family to 20 arRP loci. All exons and intron-exon junctions of candidate genes not excluded by haplotype analysis were PCR amplified and directly sequenced. RESULTS: The proband was a 43-year-old female patient. Best-corrected visual acuity was 20/63 (right eye) and 20/80 (left eye). Visual loss began during the third decade. Funduscopic examination and fluorescein angiography revealed typical advanced RP changes with bone spicule-like pigment deposits in the posterior pole and the midperiphery along with retinal atrophy, narrowing of the vessels, and waxy optic discs. Haplotype analysis revealed homozygosity with microsatellite markers D1S412 and D1S413 on chromosome 1q31.3. These markers flanked CRB1. Our results excluded linkage of all the other arRP loci/genes tested. Sequencing of the 12 coding exons and splice sites of CRB1 disclosed a homozygous missense mutation in exon 7 at nucleotide c. 2291G>A, resulting in an arginine to histidine substitution (p.R764H). CONCLUSIONS: R764H is a novel mutation associated with CRB1-related arRP. Previously, an R764C mutation was reported. Extending the mutation spectrum of CRB1 with additional families is important for genotype-phenotype correlations and characterization of the scope of mutation.

Clinical polymorphism of stargardt disease in a large consanguineous tunisian family; implications for nosology.

PURPOSE: To describe the polymorphic expression of Stargardt disease in a large Tunisian family with clinical intra- and interfamilial variation of the condition. METHODS: Twelve subjects from two related families with autosomal recessive Stargardt disease were enrolled. A detailed clinical examination including visual acuity and visual field measurement, fundus photography, fluorescein angiography, electroretinography (ERG) and color vision testing was performed for all subjects. RESULTS: The youngest child from family A manifested typical Stargardt disease while her two brothers presented with Stargardt disease-fundus flavimaculatus (STGD-FFM) and her two sisters demonstrated a peculiar phenotype overlapping Stargardt disease and cone-rod dystrophy; their phenotypic manifestation corresponded well with ERG groups I, II and III, respectively. This uncommon occurrence of an age-related decline in ERG amplitude and worsening of fundus changes is suggestive of a grading pattern in Stargardt disease. Their two cousins in family B, displayed the STGD-FFM phenotype. Despite clinically similar STGD-FFM patterns in both families, age of onset and progression of the phenotype in family B differed from family A. CONCLUSION: This is the first report on phenotypic variation of Stargardt disease in a large Tunisian family. Regarding phenotype and severity of visual symptoms, family A demonstrated Stargardt disease at various stages of progression. In addition, STGD-FFM appeared to be an independent clinical entity in family B. These findings imply that further parameters are required to classify Stargardt's disease.

Choroidal thickness measurement in highly myopic eyes using SD-OCT.

BACKGROUND AND OBJECTIVE: To measure macular choroidal thickness (CT) using spectral-domain optical coherence tomography (OCT) and to investigate the correlation between CT and age, degree of myopia, and history of macular choroidal neovascularization (CNV). PATIENTS AND METHODS: A cross-sectional study included 187 highly myopic eyes of 187 patients examined between January and December 2010. The choroid was imaged with spectral-domain OCT by changing the reference position from the vitreous to the choroid. CT was measured from the outer border of the hyperreflective line corresponding to the retinal pigment epithelium to the inner scleral border. RESULTS: The mean age was 47.21 ± 14.24 years, the mean spherical equivalent refractive error was -13.66 ± 5.77, and the mean subfoveal CT was 100.71 ± 59.98 µm. CT was correlated negatively with age (P < 10(-3)) and refractive error (P < 10(-3)). Forty-two eyes had a history of CNV, the mean CT was 55.45 ± 24.46 µm, and this was significantly thinner than in eyes without CNV (P < 10(-3)). CONCLUSION: In highly myopic eyes, the choroid is thin and undergoes further attenuation with age and increasing myopia. In addition, these findings suggest that the choroid may play a role in the pathogenesis of CNV.

Clinical and genetic investigation of a large Tunisian family with complete achromatopsia: identification of a new nonsense mutation in GNAT2 gene.

Complete achromatopsia is a rare autosomal recessive disease associated with CNGA3, CNGB3, GNAT2 and PDE6C mutations. This retinal disorder is characterized by complete loss of color discrimination due to the absence or alteration of the cones function. The purpose of the present study was the clinical and the genetic characterization of achromatopsia in a large consanguineous Tunisian family. Ophthalmic evaluation included a full clinical examination, color vision testing and electroretinography. Linkage analysis using microsatellite markers flanking CNGA3, CNGB3, GNAT2 and PDE6C genes was performed. Mutations were screened by direct sequencing. A total of 12 individuals were diagnosed with congenital complete achromatopsia. They are members of six nuclear consanguineous families belonging to the same large consanguineous family. Linkage analysis revealed linkage to GNAT2. Mutational screening of GNAT2 revealed three intronic variations c.119-69G>C, c.161+66A>T and c.875-31G>C that co-segregated with a novel mutation p.R313X. An identical GNAT2 haplotype segregating with this mutation was identified, indicating a founder mutation. All patients were homozygous for the p.R313X mutation. This is the first report of the clinical and genetic investigation of complete achromatopsia in North Africa and the largest family with recessive achromatopsia involving GNAT2; thus, providing a unique opportunity for genotype-phenotype correlation for this extremely rare condition.

Optical Coherence Tomographic Findings in Berlin's Edema.

PURPOSE: To describe optical coherence tomography (OCT) findings in a patient with Berlin's edema following blunt ocular trauma. CASE REPORT: A 26-year-old man presented with acute loss of vision in his left eye following blunt trauma. He underwent a complete ophthalmologic examination and OCT. Fundus examination revealed abnormal yellow discoloration in the macula. OCT disclosed thickening of outer retinal structures and increased reflectivity in the area of photoreceptor outer segments with preservation of inner retinal architecture. Re-examination was conducted one month later at the time which OCT changes resolved leading to a surprisingly normal appearance. CONCLUSION: OCT can be a useful tool in the diagnosis and follow-up of eyes with Berlin's edema and may reveal ultrastructural macular changes.

Identification of a novel mutation in FOXL2 gene that leads to blepharophimosis ptosis epicanthus inversus and telecanthus syndrome in a Tunisian consanguineous family.

Mutations in FOXL2 gene are responsible for blepharophimosis ptosis epicanthus inversus and telecanthus syndrome (BPES). The BPES syndrome is a rare autosomal dominant genetic disease characterized by eyelid malformations associated with premature ovarian failure (BPES type I) or not (BPES type II). The human FOXL2 protein (376 aa) contains a 100 amino-acid DNA-binding forkhead domain (residues 52-152) and a polyalanine tract (residues 221-234). In the present study, we report the molecular investigation of four affected members with BPES syndrome in a Tunisian consanguineous family. To identify the causative mutation, we performed a direct sequencing of the FOXL2 gene. The sequence analysis of the coding exon revealed a novel frameshift mutation g.1113 dup C, c.876 dup C, p.P292 Fs. The mutation is located downstream of the polyalanine tract and causes the protein extension to 532 aa. This study reports for the first time a novel frameshift mutation in two-generation consanguineous Tunisian family with BPES. Our results expand the spectrum of FOXL2 mutations.