Perumalsamy Vijayalakshmi

Incomplete penetrance and phenotypic variability characterize Gdf6-attributable oculo-skeletal phenotypes

Proteins of the bone morphogenetic protein (BMP) family are known to have a role in ocular and skeletal development; however, because of their widespread expression and functional redundancy, less progress has been made identifying the roles of individual BMPs in human disease. We identified seven heterozygous mutations in growth differentiation factor 6 (GDF6), a member of the BMP family, in patients with both ocular and vertebral anomalies, characterized their effects with a SOX9-reporter assay and western analysis, and demonstrated comparable phenotypes in model organisms with reduced Gdf6 function. We observed a spectrum of ocular and skeletal anomalies in morphant zebrafish, the latter encompassing defective tail formation and altered expression of somite markers noggin1 and noggin2. Gdf6(+/-) mice exhibited variable ocular phenotypes compatible with phenotypes observed in patients and zebrafish. Key differences evident between patients and animal models included pleiotropic effects, variable expressivity and incomplete penetrance. These data establish the important role of this determinant in ocular and vertebral development, demonstrate the complex genetic inheritance of these phenotypes, and further understanding of BMP function and its contributions to human disease.

CRYBA4, a Novel Human Cataract Gene, Is Also Involved in Microphthalmia

Genetic analysis of a large Indian family with an autosomal dominant cataract phenotype allowed us to identify a novel cataract gene, CRYBA4. After a genomewide screen, linkage analysis identified a maximum LOD score of 3.20 (recombination fraction [theta] 0.001) with marker D22S1167 of the beta -crystallin gene cluster on chromosome 22. To date, CRYBA4 was the only gene in this cluster not associated with either human or murine cataracts. A pathogenic mutation was identified in exon 4 that segregated with the disease status. The c.317T-->C sequence change is predicted to replace the highly conserved hydrophobic amino acid phenylalanine94 with the hydrophilic amino acid serine. Modeling suggests that this substitution would significantly reduce the intrinsic stability of the crystalline monomer, which would impair its ability to form the association modes critical for lens transparency. Considering that CRYBA4 associates with CRYBB2 and that the latter protein has been implicated in microphthalmia, mutational analysis of CRYBA4 was performed in 32 patients affected with microphthalmia (small eye). We identified a c.242T-->C (Leu69Pro) sequence change in exon 4 in one patient, which is predicted here to disrupt the beta -sheet structure in CRYBA4. Protein folding would consequently be impaired, most probably leading to a structure with reduced stability in the mutant. This is the first report linking mutations in CRYBA4 to cataractogenesis and microphthalmia.

Laboratory confirmation of congenital rubella syndrome in infants: an eye hospital based investigation.

A total of 190 specimens from South Indian children aged 0–59 months with ocular anomalies consistent with suspected congenital rubella syndrome (CRS) were investigated. Twenty‐six of the 65 infants (40%) were confirmed as CRS by detection of rubella specific IgM. Rubella RNA was detected in 41 samples from 26 infants by both real‐time and block based PCR. The PCR results correlated well with the presence of anti‐rubella IgM/IgG (23/27 cases with rubella IgM were PCR positive). Whereas, only 17 of 26 infants met the WHO CRS case definition. Amongst the various specimens tested from the sero‐confirmed cases (n = 27), a high percentage of positives were detected in lens (92%) and oral fluid (60%) specimens, when compared to other samples. The quantification of viral load by real‐time PCR demonstrated higher copy number of virus in lens samples of 0–11 months infants. The rubella viruses were characterized and revealed the circulation of genotype 2B in three South Indian states. The integrated analysis of clinical manifestations, serological and molecular data in the study has generated baseline information of rubella infection and CRS in infants with ocular anomalies. J. Med. Virol. 80:536–546, 2008.

Rubella serosurveys at three Aravind Eye Hospitals in Tamil Nadu, India

OBJECTIVE To determine the susceptibility of female eye hospital staff to rubella infection and the potential risk for hospital-based rubella outbreaks. METHODS A prospective cohort study on the seroprevalence of rubella IgG antibodies was conducted at three large eye hospitals in Coimbatore, Madurai and Tirunelveli, Tamil Nadu, India, where young children with eye abnormalities attributable to congenital rubella are treated. A total of 1000 female hospital employees aged 18-40 years agreed to participate and gave written informed consent. FINDINGS The proportions of rubella-seronegative women were: 11.7% at Coimbatore, with a 95% confidence interval (CI) of 8.1-16.5; 15% at Madurai (95% CI = 12.3-18.1), and 20.8 at Tirunelveli (95% CI = 14.7-28.6). For the entire cohort the proportion seronegative was significantly higher among married women (21.5%) than among single women (14.0%) (P = 0.02). Rates of seronegativity were highest among physicians and lowest among housekeepers. All 150 seronegative women in the study sample accepted a dose of rubella vaccine. CONCLUSION These are the first rubella serosurveys to have been reported from eye hospitals in any country. The relatively high rate of susceptibility indicated a risk of a rubella outbreak, and this was reduced by vaccinating all seronegative women. A policy has been established at all three hospitals for the provision of rubella vaccine to new employees. Other hospitals, especially eye hospitals and hospitals in countries without routine rubella immunization, should consider the rubella susceptibility of staff and the risk of hospital-based rubella outbreaks.

PAX6 gene variations associated with aniridia in south India

BackgroundMutations in the transcription factor gene PAX6 have been shown to be the cause of the aniridia phenotype. The purpose of this study was to analyze patients with aniridia to uncover PAX6 gene mutations in south Indian population.MethodsTotal genomic DNA was isolated from peripheral blood of twenty-eight members of six clinically diagnosed aniridia families and 60 normal healthy controls. The coding exons of the human PAX6 gene were amplified by PCR and allele specific variations were detected by single strand conformation polymorphism (SSCP) followed by automated sequencing.ResultsThe sequencing results revealed novel PAX6 mutations in three patients with sporadic aniridia: c.715ins5, [c.1201delA; c.1239A>G] and c.901delA. Two previously reported nonsense mutations were also found: c.482C>A, c.830G>A. A neutral polymorphism was detected (IVS9-12C>T) at the boundary of intron 9 and exon 10. The two nonsense mutations found in the coding region of human PAX6 gene are reported for the first time in the south Indian population.ConclusionThe genetic analysis confirms that haploinsuffiency of the PAX6 gene causes the classic aniridia phenotype. Most of the point mutations detected in our study results in stop codons. Here we add three novel PAX6 gene mutations in south Indian population to the existing spectrum of mutations, which is not a well-studied ethnic group. Our study supports the hypothesis that a mutation in the PAX6 gene correlates with expression of aniridia.

Bilateral persistent fetal vasculature: A study of 11 cases

PURPOSE To describe the clinical and radiologic features of patients with bilateral persistent fetal vasculature (PFV). METHODS All patients diagnosed with symmetric, bilateral PFV over a 3.5-year period were included in this representative, observational case series. Only patients with more or less symmetrical disease in both eyes were included. Examination under anesthesia was performed in all but 1 case. B-scan ultrasonography of the eye was performed in all cases. A computed tomographic or magnetic resonance imaging scan was done if the ocular ultrasonography was inconclusive. A systemic workup was performed to rule out associated systemic anomalies. RESULTS The study group included 11 patients. Of the 22 eyes studied, 20 (91%) showed features of both the anterior and the posterior forms of PFV. Two children tested positive for IgM rubella antibodies. Ten eyes (45.5%) had a horizontal corneal diameter of less than 10 mm. Fifteen eyes (68.2%) had cataract at presentation. Intraocular pressure was >21 mm Hg in 17 eyes (77.3%). CONCLUSIONS Microcornea and cataract were common findings. Bilateral PFV cases were more commonly associated with combined anterior and posterior PFV. Bilateral PFV, although infrequent, should be considered in the differential diagnosis of bilateral leukocoria.

Visual outcome of cataract surgery in children with congenital rubella syndrome

PURPOSE To evaluate visual outcome after cataract surgery in children with congenital rubella syndrome (CRS). METHODS A retrospective analysis was conducted on 40 eyes of 22 children with CRS who underwent cataract surgery. Thirty-six eyes underwent lensectomy with anterior vitrectomy, and 4 eyes underwent extracapsular cataract extraction with primary posterior capsulectomy. The median age at surgery was 6 months, and median duration of postoperative follow up was 68.5 months. Each follow-up visit consisted of visual acuity estimation, refraction, anterior and posterior segment examination, and intraocular pressure measurements. RESULTS Visual acuity at final follow up was 6/24 or better in 6 (15.0%) eyes, and 22 (55.0%) eyes had visual acuity less than 3/60. Postoperative complications included transient corneal edema in 18 (45.0%) eyes, glaucoma in 5 (12.5%) eyes, after cataract in 1 (2.5%) eye, and hyphema in 1 (2.5%) eye. Ocular disorders affecting visual outcome included stimulus deprivation amblyopia, glaucoma, optic atrophy, corneal opacity, and after cataract. Associated systemic disorders included neurological problems in 15 (68.2%), hearing loss in 12 (54.6%), cardiovascular problems in 9 (40.9%), and speech abnormalities in 7 (31.8%) children. CONCLUSIONS The less-than-optimal postoperative visual outcome suggests the need to look at primary prevention of rubella, especially in developing countries.

Surgical outcome in monocular elevation deficit: A retrospective interventional study

Background and Aim: Monocular elevation deficiency (MED) is characterized by a unilateral defect in elevation, caused by paretic, restrictive or combined etiology. Treatment of this multifactorial entity is therefore varied. In this study, we performed different surgical procedures in patients of MED and evaluated their outcome, based on ocular alignment, improvement in elevation and binocular functions. Study Design: Retrospective interventional study. Materials and Methods: Twenty-eight patients were included in this study, from June 2003 to August 2006. Five patients underwent Knapp procedure, with or without horizontal squint surgery, 17 patients had inferior rectus recession, with or without horizontal squint surgery, three patients had combined inferior rectus recession and Knapp procedure and three patients had inferior rectus recession combined with contralateral superior rectus or inferior oblique surgery. The choice of procedure was based on the results of forced duction test (FDT). Results: Forced duction test was positive in 23 cases (82%). Twenty-four of 28 patients (86%) were aligned to within 10 prism diopters. Elevation improved in 10 patients (36%) from no elevation above primary position (-4) to only slight limitation of elevation (-1). Five patients had preoperative binocular vision and none gained it postoperatively. No significant postoperative complications or duction abnormalities were observed during the follow-up period. Conclusion: Management of MED depends upon selection of the correct surgical technique based on employing the results of FDT, for a satisfactory outcome.

Improvement in visual acuity following surgery for correction of head posture in infantile nystagmus syndrome.

PURPOSE To report the effect of the abnormal head posture (AHP) correcting procedures on the visual acuity improvement in patients with infantile nystagmus syndrome (INS) and the visual acuity improvement outcomes in different AHP correcting surgeries in INS. METHODS This was a prospective, non-randomized, interventional study. Twenty-eight patients underwent the Anderson-Kestenbaum procedure or the modified Anderson procedure with or without tenotomy of at least one horizontal recti for correction of AHP. Best-corrected binocular null zone acuity and degree of AHP was recorded preoperatively and compared with those done 1 month postoperatively. RESULTS The average null zone logarithm of the minimum angle of resolution acuity was 0.42 preoperatively, which improved significantly to 0.33 postoperatively (P = .002). The AHP ranged from 10° to 40° (mean: 20.89°), which improved significantly to a mean of 3.21° (P = .000). No significant difference (P = .65) was found in the visual acuity improvement among patients who underwent the Anderson-Kestenbaum procedure or the modified Anderson procedure with or without tenotomy. No significant difference in the visual acuity improvement was seen in patients who underwent tenotomy of at least one horizontal rectus muscle along with the modified Anderson procedure compared to those who underwent the modified Anderson procedure alone (P = .28). CONCLUSION The procedures used mainly for correction of AHP in INS do yield significant improvement in the visual acuity. This improvement is seen in patients undergoing surgery for both horizontal and vertical AHP.

Prevalence of eye signs in congenital rubella syndrome in South India: A role for population screening

Purpose: Congenital rubella syndrome (CRS) resulting from maternal rubella infection, especially in the first trimester, affects an estimated 100 000 infants each year worldwide. Immunisation has reduced its occurrence in the developed world, though it remains a problem in countries with poor immunisation coverage. This population-based study was aimed at screening children below 5 years of age for ocular signs suspicious of CRS. Methods: Suspected CRS cases were recruited from hospital and outreach services of the Aravind Eye Care System over a 24-month period. Clinical confirmation was based on the fulfilment of the World Health Organization (WHO) definition, and laboratory confirmation was based on a positive test for IgM antibody. Results: Children under 5 years of age (n = 51 548) with ocular complaints were screened for eye signs suspicious of CRS; CRS compatible signs were detected in 1.92% (1090) children. Of these suspects (299), 27.42% were subsequently confirmed clinically according to WHO definition, and (46) 4.2% were serologically (Laboratory) confirmed. Of all the eye signs evaluated for screening, cataracts were the most sensitive (80.43%). Conclusions: Cataracts among children have a high sensitivity for detecting CRS in India. It is the only clinical eye finding that has a high enough sensitivity and specificity to be useful as a screening tool for CRS.