Congenital Aniridia: Clinic, Genetics, Therapeutics, and Prognosis

Protein profiling of conjunctival impression cytology samples of aniridia subjects

PURPOSE

Congenital aniridia is a rare disease, which is in most cases related to PAX6 haploinsufficiency. Aniridia associated keratopathy (AAK) also belongs to ocular signs of congenital aniridia. In AAK, there is corneal epithelial thinning, corneal inflammation, vascularization and scarring. In advanced stage AAK, typically, conjunctival epithelial cells slowly replace the corneal epithelium. Based on previous results we hypothesize that alterations of the conjunctival cells in congenital aniridia may also support the corneal conjunctivalization process. The aim of this study was to identify deregulated proteins in conjunctival impression cytology samples of congenital aniridia subjects.

METHODS

Conjunctival impression cytology samples of eight patients with congenital aniridia [age 34.5 ± 9.9 (17-51) years, 50% female] and eight healthy subjects [age 34.1 ± 11.9 (15-54) years, 50% female] were collected and analysed using mass spectrometry. Proteomic profiles were analysed in terms of molecular functions, biological processes, cellular components and pathway enrichment using the protein annotation of the evolutionary relationship (PANTHER) classification system.

RESULTS

In total, 3323 proteins could be verified and there were 127 deregulated proteins (p < 0.01) in congenital aniridia. From the 127 deregulated proteins (DEPs), 82 altered biological processes, 63 deregulated cellular components, 27 significantly altered molecular functions and 31 enriched signalling pathways were identified. Pathological alteration of the biological processes and molecular functions of retinol binding and retinoic acid biosynthesis, as well as lipid metabolism and apoptosis related pathways could be demonstrated.

CONCLUSIONS

Protein profile of conjunctival impression cytology samples of aniridia subjects identifies alterations of retinol binding, retinoic acid biosynthesis, lipid metabolism and apoptosis related pathways. Whether these changes are directly related to PAX6 haploinsufficiency, must be investigated in further studies. These new findings offer the possibility to identify potential new drug targets.

Preclinical biocompatibility and biosafety evaluation of a new foldable brown diaphragm intraocular lens: An in vitro and in vivo study

BACKGROUND

A new foldable brown diaphragm intraocular lens (IOL) was preclinically evaluated in vitro and in vivo by comparing its biocompatibility and biosafety with those of a commercially available IOL.

METHODS

The new foldable iris-diaphragm IOL is composed of hydrophobic acrylic material, with a transparent optical zone and surrounding brown diaphragm. Cellular experiments evaluating lens epithelial cell morphology, adhesion, and migration were conducted to exclude cytotoxic effects. Twelve New Zealand rabbits underwent implantation of a brown diaphragm IOL in one eye, whilst an additional 12 had a commercially available foldable IOL implanted, followed by slit-lamp evaluations of inflammatory reactions and capsular opacification. Corneal endothelial cells density was measured before and after implantation. Aqueous humour samples were obtained weekly for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis to investigate dye leakage from the brown-diaphragm IOL. Following 12 weeks of observation, haematoxylin and eosin staining of ocular tissue and scanning electron microscopy (SEM) of the IOL surface were performed.

RESULTS

Results from in vivo experiments found no statistically significant differences between the two groups in terms of postoperative inflammation and capsular biocompatibility. No significant changes in corneal endothelial cell density were observed in either group before and after surgery. LC-MS/MS analysis showed that the target dye was not detected in aqueous humour samples. Histopathology of ocular sections and SEM imaging of IOL surfaces showed similar changes in both groups.

CONCLUSIONS

The newly invented IOL showed good biocompatibility and biosafety. Combined with its foldability and peripheral shading, it could be a new choice for patients with iris defects.

Novel mutations of the PAX6, FOXC1, and PITX2 genes cause abnormal development of the iris in Vietnamese individuals

PURPOSE

Congenital iris abnormality is a feature of several genetic conditions, such as aniridia syndrome and anterior segment degeneration (ASD) disorders. Aniridia syndrome is caused by mutations in the PAX6 gene or its regulatory elements in the locus 11p13 or deletions of contiguous genes, while ASDs are the result of mutations in various genes, such as PAX6, FOXC1, PITX2, and CYP1B1. This study aims to identify pathogenic mutations in Vietnamese individuals with congenital anomalies of the iris.

METHODS

Genomic DNA was extracted from peripheral blood of 24 patients belonging to 15 unrelated families and their available family members. Multiplex ligation-dependent probe amplification (MLPA) was used to detect the deletions or duplications in the 11p13-14 region, including the PAX6 gene and its neighboring genes. Direct PCR sequencing was used to screen mutations in 13 exons and flanking sequences of the PAX6 gene. The patients without mutation in the PAX6 locus were further analyzed with whole exome sequencing (WES). Identified mutations were tested with segregation analysis in proband family members.

RESULTS

We identified a total of 8 novel and 4 recurrent mutations in 20 of 24 affected individuals from 12 families. Among these mutations, one large deletion of the whole PAX6 gene and another deletion of the PAX6 downstream region containing the DCDC1 and ELP4 genes were identified. Eight mutations were detected in PAX6, including four nonsense, three frameshift, and one splice site. In addition, two point mutations were identified in the FOXC1 and PITX2 genes in patients without mutation in PAX6. Some of the mutations segregated in an autosomal dominant pattern where family members were available.

CONCLUSIONS

This study provides new data on causative mutations in individuals with abnormal development of iris tissue in Vietnam. These results contribute to clinical management and genetic counseling for affected people and their families.

Improving long-term intraocular pressure and visual outcomes in eyes with aniridic glaucoma

PURPOSE

To study the long-term intraocular pressure (IOP) and visual outcomes in treated aniridic glaucoma.

METHODS

A retrospective chart review of patients with aniridia and glaucoma, with ≥ 2-year follow-up, was performed. Eyes in early glaucomatous stages were medically managed, while moderate-severe stage eyes underwent a trabeculectomy with mitomycin-c (MMC). Success was termed 'complete' when average final IOP was ≤ 18 mmHg without usage of glaucoma medications, and 'qualified' when with/without topical glaucoma therapy. A significant change in vision was defined as > 2-line change on Snellen vision chart or > 0.2 change in logMAR units in in either direction (better or worse).

RESULTS

Thirty-five eyes of 20 patients were included. The mean duration of follow-up was 7.29 ± 5.75 years. Associated ocular anomalies were present in 19 eyes (54.29%). Twelve eyes (34.28%) were maintained on medical management, while 23 eyes (65.71%) had undergone a trabeculectomy with MMC. The mean baseline IOP was 31.46 ± 6.34 mmHg, and mean IOP on last follow-up was 13.25 ± 5.82 mmHg, p < 0.001. Seventy-five percent of the medically managed eyes achieved an IOP ≤ 18 mmHg. 52.17% and 95.65% of the surgically treated eyes achieved 'complete' and 'qualified' success respectively. The median best corrected visual acuity (BCVA) at baseline was 1.48(0.6-2) logMAR units and on final follow-up was 1.3 (0.48-5) logMAR units, p = 0.21. Fifty percent of the eyes remained stable, 35.71% showed an improvement and 14.29% a deterioration of > 0.2 logMAR units. Patients with a longer follow-up (> 10 years) and those who had undergone a trabeculectomy with MMC were more likely to show good IOP control (p = 0.003; p = 0.004 respectively).

CONCLUSION

Aniridic glaucoma can be managed efficiently by medications in early glaucomatous neuropathy, and with trabeculectomy augmented with mitomycin-C and releasable sutures for more advanced glaucomas, offering favourable long-term IOP control, visual stability and safety.

Longitudinal genotype-phenotype analysis in 86 patients with PAX6-related aniridia

Aniridia is most commonly caused by haploinsufficiency of the PAX6 gene, characterized by variable iris and foveal hypoplasia, nystagmus, cataracts, glaucoma, and aniridia-related keratopathy (ARK). Genotype-phenotype correlations have previously been described; however, detailed longitudinal studies of aniridia are less commonly reported. We identified 86 patients from 62 unrelated families with molecularly confirmed heterozygous PAX6 variants from a UK-based single-center ocular genetics service. They were categorized into mutation groups, and a retrospective review of clinical characteristics (ocular and systemic) from baseline to most recent was recorded. One hundred and seventy-two eyes were evaluated, with a mean follow-up period of 16.3 ± 12.7 years. Nystagmus was recorded in 87.2% of the eyes, and foveal hypoplasia was found in 75%. Cataracts were diagnosed in 70.3%, glaucoma in 20.6%, and ARK in 68.6% of eyes. Prevalence, age of diagnosis and surgical intervention, and need for surgical intervention varied among mutation groups. Overall, the missense mutation subgroup had the mildest phenotype, and surgically naive eyes maintained better visual acuity. Systemic evaluation identified type 2 diabetes in 12.8% of the study group, which is twice the UK prevalence. This is the largest longitudinal study of aniridia in the UK, and as such, it can provide insights into prognostic indicators for patients and guiding clinical management of both ocular and systemic features.

Congenital aniridia: clinical profile of children seen at the University College Hospital, Ibadan, South-West Nigeria

Purpose:

To describe the clinical features of patients younger than 16 years with aniridia presenting to the Paediatric Ophthalmology unit of the Eye Clinic, University College Hospital, Ibadan, Nigeria.

Methods:

The is a retrospective review of children with aniridia seen between May 2015 and April 2019 at the Paediatric Ophthalmology unit of the Eye Clinic, University College Hospital in Ibadan. Data on demographic characteristics, presenting complaints, ocular and systemic examination findings, and interventions were collected and descriptively summarised.

Results:

A total of 28 eyes of 14 patients were studied. The mean age was 6.37 ± 4.98 years. Seven (50%) patients were male. Aniridia was diagnosed in first-degree relatives of nine patients. The most common complaint at presentation was poor vision in 11 (78.6%) patients. Objective visual acuity assessment was obtained in 22 (78.6%) eyes. Presenting visual acuity was worse than 20/60 in all 22 eyes and worse than 20/400 in 8 (36.4%) eyes. Refraction was performed in 17 (60.7%) eyes and revealed a mean spherical equivalent of −3.93 ± 5.99 diopters. Twenty (71.4%) eyes had corneal opacities, and lenticular opacities were seen in 15 (62.5%) of 24 eyes. Mean intraocular pressure (IOP) at presentation was 21.62 ± 10.4 mmHg; 12 (41.4%) eyes had elevated IOP at presentation. Ten (35.7%) eyes had cataract surgery and six (21.4%) eyes had glaucoma surgery.

Conclusion:

Familial aniridia was common in this study, and most of the patients presented with moderate to severe visual impairment. The common ocular associations were refractive error, cataract, corneal opacity and glaucoma.

Germline CRISPR/Cas9-Mediated Gene Editing Prevents Vision Loss in a Novel Mouse Model of Aniridia

Aniridia is a rare eye disorder, which is caused by mutations in the paired box 6 (PAX6) gene and results in vision loss due to the lack of a long-term vision-saving therapy. One potential approach to treating aniridia is targeted CRISPR-based genome editing. To enable the Pax6 small eye (Sey) mouse model of aniridia, which carries the same mutation found in patients, for preclinical testing of CRISPR-based therapeutic approaches, we endogenously tagged the Sey allele, allowing for the differential detection of protein from each allele. We optimized a correction strategy in vitro then tested it in vivo in the germline of our new mouse to validate the causality of the Sey mutation. The genomic manipulations were analyzed by PCR, as well as by Sanger and next-generation sequencing. The mice were studied by slit lamp imaging, immunohistochemistry, and western blot analyses. We successfully achieved both in vitro and in vivo germline correction of the Sey mutation, with the former resulting in an average 34.8% ± 4.6% SD correction, and the latter in restoration of 3xFLAG-tagged PAX6 expression and normal eyes. Hence, in this study we have created a novel mouse model for aniridia, demonstrated that germline correction of the Sey mutation alone rescues the mutant phenotype, and developed an allele-distinguishing CRISPR-based strategy for aniridia.

Bilateral aniridia and congenital ureteral valve: Role of genetic testing

Background

Congenital aniridia involves total or partial hypoplasia of the iris and is due to a deficiency in PAX6 gene expression. WAGR syndrome is comprised of Wilms tumor, aniridia, genitourinary abnormalities, and intellectual disability. Numerous genitourinary pathologies may be associated with WAGR syndrome, necessitating an evaluation of the genitourinary anatomy. The WT1 is vital for the development of kidneys, ovaries in females, and testes in males. WT1 gene mutations result in a WT1 protein with a decreased ability to bind to DNA, leading to uncontrolled growth, and cell division in the kidney which permits the development of Wilms tumor. A congenital ureteral valve is an exceedingly rare cause of obstructive uropathy.

Results

A renal and bladder ultrasound demonstrated a renal cyst. A voiding cystourethrogram revealed grade 3 vesicoureteral reflux, and a MAG3 renal scan showed ureteropelvic junction obstruction and hydronephrosis. A ureteral stent was inserted at 3 months of age after which the renal cyst resolved. The patient was urinary tract infection‐free at 27 months of age. Genetic testing confirmed a heterozygous alteration in PAX6 (c.495delG, p.Thr166Leufs*41) and no abnormalities of WT1, excluding WAGR syndrome.

Conclusion

The genitourinary risks potentially associated with aniridia necessitate prompt genetic analysis to evaluate for WAGR syndrome.

Nystagmus associated with macular dysplasia

Purpose: To describe Optical Coherence Tomography (OCT) findings of the macula in patients with nystagmus, mainly the relationship between spectral-domain OCT (SD-OCT) images and nystagmus in macular dysplasia.Methods: In this study, 17 cases (29 eyes) with congenital macular abnormalities in patients with albinism, macular heterotopias, congenital aniridia, foveal hypoplasia, congenital macular coloboma, and congenital retinoschisis were retrospectively analyzed. Patients underwent multimodal retinal imaging examinations including ultra-widefield fundus imaging, SD-OCT, autofluorescence, and visual field. When the pit was not clearly presented, SD-OCT imaging was centered at the expected foveal center.Results: In cases of oculocutaneous albinism SD-OCT showed the absence of the foveal pit and increased foveal thickness, with nystagmus. Their fundus revealed a lack of pigment in retinal pigment epithelium with visible large choroidal vessels. SD-OCT in congenital aniridia showed a planar fovea in the macula with the lack of a foveal pit and nystagmus. SD-OCT showed the absence of a foveal pit in foveal hypoplasia with nystagmus. In cases of monocular macular heterotopia, no nystagmus was found; the fellow eye had good vision and the macular morphology was usually normal. Nystagmus was not found in patients with congenital macular coloboma and congenital retinoschisis in this study.Conclusion: SD-OCT plays an important role in the diagnosis and prognosis of macular dysplasia in patients with nystagmus. Absence of a normal foveal pit is an OCT-imaging characteristic of macular dysplasia associated with nystagmus.

Optical Coherence Tomography Findings After Childhood Lensectomy

Purpose

To explore the impact of childhood lensectomy on posterior segment development.

Methods

Cross-sectional observational study at children's eye clinics at a tertiary referral center in London, UK. We included 45 children age 4 to 16 years with healthy eyes and 38 who had undergone lensectomy. We acquired posterior segment optical coherence tomography scans of both eyes. We used parametric and nonparametric tests in SPSS24 for the comparison of parameters between groups and within individuals; a P value less than 0.05 was considered significant. The main outcome measures were foveal pit depth and subfoveal choroidal thickness (CT). Secondary outcomes were inner and outer ring CT and photoreceptor layer parameters, macular and peripapillary retinal nerve fiber layer thickness.

Results

Foveal pit depth and subfoveal CT are significantly reduced in eyes that have undergone lensectomy compared with nonoperated eyes. Inner ring CT and outer ring CT are reduced. Foveal inner retinal layer thickness is increased. Mean inner retinal and outer nuclear layer thickness are not affected.

Conclusions

Childhood lensectomy is associated with a reduction in developmental foveal pit deepening and lack of developmental thickening of the posterior choroid. Mechanical and optical disruption of foveal and subfoveal choroidal development may affect structural foveal development after childhood lensectomy.

Black Diaphragm Intraocular Lens Implantation in Patients with Aniridia

Purpose

To review the management outcomes of black diaphragm intraocular (BDI) lens implantation in Arab patients with aniridia.

Methods

Patients with aniridia undergone BDI lens implantation at our institution between 2013 and 2014 were included. Uncorrected visual acuity (UCVA), manifest refraction, and best-corrected visual acuity (BCVA) were evaluated before and 6 months and yearly after BDI lens implant surgery until the last visit. Intra- and postoperative complications were noted.

Results

Our series comprised 14 patients (8 males) with aniridia. The median duration of follow-up was 30 months (25% quartile). Ocular parameters, refractive status, and vison were all significantly improved at the last follow-up compared to the preoperative values (P < 0.05 for all comparisons). All patients reported a significant decrease in photophobia and glare. Postoperatively, 11 eyes (78%) gained 2 or more lines of UCVA. At the last follow-up, BCVA increased by 2 or more lines in all cases. Early postoperative complications included main wound leakage (one eye) and anterior chamber hyphema (one eye). Late (≥6 months) complications included corneal decompensation (one eye), failed penetrating keratoplasty graft (2 eyes), and subluxation of a scleral fixated BDI lens (one eye). Surgical interventions performed to manage complications included penetrating keratoplasty in 2 eyes with corneal decompensation and failed graft (one each), and re-suturing of a subluxated intraocular lens (one eye).

Conclusion

BDI lenses seem to be a safe and effective iris prosthetic with intraocular lens combination surgery for patients with congenital or traumatic aniridia. Periodic evaluation and prompt management of complications are recommended.

Two Paired Box 6 mutations identified in Chinese patients with classic congenital aniridia and cataract

Congenital aniridia is a rare genetic disorder characterized by a variable degree of hypoplasia or absence of iris. It is frequently associated with keratopathy, cataract, juvenile-onset glaucoma and foveal and optic nerve hypoplasia. Mutations in the Paired Box 6 (PAX6) gene on chromosome 11p13 have been demonstrated to cause aniridia. The aim of the present study was to investigate the genetic variations of PAX6 in two sporadic patients from southern China with classic congenital aniridia and cataract. Complete ophthalmic and physical examinations were performed, including best-corrected visual acuity, intraocular pressure, slit-lamp examination, fundus examination, optical coherence tomography, ultrasound biomicroscopy, and Pentacam scanning. Genomic DNA was extracted from leukocytes of peripheral blood collected from the two patients, their unaffected parents and 200 unrelated control subjects from the same population. Exons 4–13 of the PAX6 gene were amplified by polymerase chain reaction and sequenced directly. Patient 1 was affected with aniridia accompanied by congenital cataract and nystagmus. A novel heterozygous PAX6 frameshift mutation c.277delG (p.Glu93SerfsX31) in exon 6 was identified in this patient. Patient 2 was presented with aniridia, congenital cataract, lens subluxation and glaucoma. A recurrent nonsense mutation c.718C>T (p.Arg240X) in exon 9 was identified in this patient. The present results expand the mutation spectrum of PAX6 and will be valuable for genetic counseling in the affected families. Additionally, the identification of these mutations reiterates the importance of PAX6 in ocular development and sheds light on the pathogenesis of congenital aniridia.

Outcome of Pediatric Cataract Surgeries in a Tertiary Center in Switzerland

Purpose

To determine and to analyze the outcome of pediatric cataract surgery.

Methods

A retrospective chart review of individuals aged up to 10 years who underwent cataract surgery between January 1, 2004, and December 31, 2014, at the UniversityHospital Zurich, Switzerland.

Results

63 children (94 affected eyes) with bilateral (68/94) or unilateral (26/94) cataract were identified. Surgery was performed at a median age of 1.5 months (IQR: 1.3–2.6 months) for the aphakic group (45/94) and of 50.7 months (IQR: 38.0–78.4 months) for the IOL group (49/94). At the last follow-up visit (median 31.1 months, IQR: 18.4–50.2 months), visual acuity was better in bilateral than in unilateral cataract cases. Posterior capsular opacification (PCO) was diagnosed in 30.9% of eyes without a significant difference in the IOL and aphakic groups (p = 0.12). Aphakic glaucoma was diagnosed in 12/45 eyes at a median of 6.8 months (IQR 2.1–13.3 months) after surgery. Microcornea (5/12) and anterior segment anomalies (8/12) were associated with glaucoma development (p < 0.05).

Conclusion

Laterality and timing of surgery influence the outcome of pediatric cataract surgery. PCO was the most frequent postoperative complication. Aphakic glaucoma is often associated with ocular developmental abnormalities and a poor visual outcome.

Novel use of fibrin sealant for scleral suture free placement of a glaucoma drainage device in advanced scleral thinning

Purpose

This reports a case using fibrin glue to secure a glaucoma drainage device plate to the sclera where there is a concern with the use of suture.

Observations

A 13-year-old patient with congenital aniridia and associated glaucoma refractory to topical medications underwent implantation of a glaucoma drainage device (GDD) for improved intraocular pressure (IOP) control. The patient had substantial scleral thinning with staphyloma formation, potentially making the use of traditional suturing techniques problematic. Fibrin glue was used to attach the GDD plate, as well the tube and patch graft which has been previously described, without sutures. The patient tolerated the procedure well with a 41% reduction in IOP at six months follow-up with no migration of the GDD from its original position.

Conclusions and importance

The use of fibrin glue in ophthalmology can be expanded to include attachment of the GDD plate to the sclera in patients with suturing contraindications.