Congenital Aniridia and the Ocular Surface.

Aniridia is a congenital pan-ocular disorder caused by haplo-insufficiency of Pax6, a crucial gene for proper development of the eye. Aniridia affects a range of eye structures, including the cornea, iris, anterior chamber angle, lens, and fovea. The ocular surface, in particular, can be severely affected by a progressive pathology termed aniridia-associated keratopathy (AAK), markedly contributing to impaired vision. The purpose of this review is to provide an update of the current knowledge of the genetic, clinical, micro-morphological, and molecular aspects of AAK. We draw upon material presented in the literature and from our own observations in large aniridia cohorts. We summarize signs and symptoms of AAK, describe current options for management, and discuss the latest research findings that may lead to better diagnosis and new treatment or prevention strategies for this debilitating ocular surface condition.

Analysis of protein composition and protein expression in the tear fluid of patients with congenital aniridia.

Aniridia is a rare congenital genetic disorder caused by haploinsuffiency of the PAX6 gene, the master gene for development of the eye. The expression of tear proteins in aniridia is unknown. To screen for proteins involved in the aniridia pathophysiology, the tear fluid of patients with diagnosed congenital aniridia was examined using two-dimensional electrophoresis (2-DE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two-dimensional map of tear proteins in aniridia has been established and 7 proteins were differentially expressed with P<0.01 between aniridia patients and control subjects. Five of them were more abundant in healthy subjects, particularly α-enolase, peroxiredoxin 6, cystatin S, gelsolin, apolipoprotein A-1 and two other proteins, zinc-α2-glycoprotein and lactoferrin were more expressed in the tears of aniridia patients. Moreover, immunoblot analysis revealed elevated levels of vascular endothelial growth factor (VEGF) in aniridia tears which is in concordance with clinical finding of pathological blood and lymph vessels in the central and peripheral cornea of aniridia patients. The proteins with different expression in patients' tears may be new candidate molecules involved in the pathophysiology of aniridia and thus may be helpful for development of novel treatment strategies for the symptomatic therapy of this vision threatening condition. BIOLOGICAL SIGNIFICANCE: This study is first to demonstrate protein composition and protein expression in aniridic tears and identifies proteins with different abundance in tear fluid from patients with congenital aniridia vs. healthy tears.

In vivo morphology of the limbal palisades of vogt correlates with progressive stem cell deficiency in aniridia-related keratopathy.

PURPOSE: To investigate morphologic alterations in the limbal palisades of Vogt in a progressive form of limbal stem cell deficiency. METHODS: Twenty Norwegian subjects (40 eyes) with congenital aniridia and 9 healthy family members (18 eyes) without aniridia were examined. Clinical grade of aniridia-related keratopathy (ARK) was assessed by slit-lamp biomicroscopy, and tear production and quality, corneal thickness, and sensitivity were additionally measured. The superior and inferior limbal palisades of Vogt and central cornea were examined by laser scanning in vivo confocal microscopy (IVCM). RESULTS: In an aniridia patient with grade 0 ARK, a transparent cornea and normal limbal palisade morphology were found. In grade 1 ARK, 5 of 12 eyes had degraded palisade structures. In the remaining grade 1 eyes and in all 20 eyes with stage 2, 3, and 4 ARK, palisade structures were absent by IVCM. Increasing ARK grade significantly correlated with reduced visual acuity and corneal sensitivity, increased corneal thickness, degree of degradation of superior and inferior palisade structures, reduced peripheral nerves, increased inflammatory cell invasion, and reduced density of basal epithelial cells and central subbasal nerves. Moreover, limbal basal epithelial cell density and central corneal subbasal nerve density were both significantly reduced in aniridia compared to healthy corneas (P = 0.002 and 0.003, respectively). CONCLUSIONS: Progression of limbal stem cell deficiency in aniridia correlates with degradation of palisade structures, gradual transformation of epithelial phenotype, onset of inflammation, and a corneal nerve deficit. IVCM can be useful in monitoring early- to late-stage degenerative changes in stem cell-deficient patients.

Pathologic epithelial and anterior corneal nerve morphology in early-stage congenital aniridic keratopathy.

OBJECTIVE: To document the clinical and morphologic corneal findings in the early stages of congenital aniridic keratopathy in Swedish families. DESIGN: Prospective, observational, comparative case series. PARTICIPANTS: A total of 16 eyes of 16 subjects with congenital aniridic keratopathy and a clear central cornea, and 6 eyes from 6 healthy controls (unaffected relatives). Nine of the 16 eyes with aniridia came from 5 families with a documented familial history of aniridia. METHODS: Detailed ophthalmic examinations included best spectacle-corrected visual acuity (BSCVA), tear film production, tear break-up time (BUT), corneal touch sensitivity, intraocular pressure measurement, ultrasound pachymetry, slit-lamp biomicroscopy, and laser scanning in vivo confocal microscopy (IVCM). MAIN OUTCOME MEASURES: Confirmed stage of aniridic keratopathy, clinical parameters of cornea and tear film (visual acuity, sensitivity, corneal thickness, tear production, and BUT), and the morphologic status of corneal epithelium, sub-basal nerves, and limbal palisades of Vogt. RESULTS: In early-stage aniridic keratopathy, BSCVA and tear BUT were reduced relative to controls (P < 0.001 for both), and corneal thickness was increased (P=0.01). Inflammatory dendritic cells were present in the central epithelium in aniridia, with significantly increased density relative to controls (P = 0.001). Discrete focal opacities in the basal epithelial region were present in 5 of 11 aniridia cases with an otherwise clear cornea. Opacities were associated with dendritic cells and harbored structures presumed to be goblet cells. Sub-basal nerves were extremely dense in 3 aniridia cases, and a prominent whorl pattern of nerves and epithelial cells was observed in 1 case. Normal limbal palisade morphology was absent in aniridia but present in controls. CONCLUSIONS: Early-stage aniridic keratopathy is characterized by the development of focal opacities in the basal epithelium, altered sub-basal nerves, infiltration of the central epithelium by dendritic cells, tear film instability, and increased corneal thickness and degradation of limbal palisade architecture. These findings may help to elucidate the pathogenesis of aniridic keratopathy.

Corneal involvement in congenital aniridia.

PURPOSE: The purpose of this research is 2-fold. First of all, the level of keratopathy development in patients with congenital aniridia is studied. In addition, a correlation between the effects of ocular surgery on the severity of keratopathy is made. METHODS: A thorough search for the total number of patients with aniridia in Sweden and Norway was performed. One hundred eighty-one patients were identified and 124 (69%) of these were examined. Three artificial eyes, 16 eyes with corneal transplants, and 1 eye with a corneal limbal allograft were excluded from the study. All participating patients underwent clinical ophthalmologic examinations, including photographs, and their medical history was recorded. A slit lamp was used to examine the presence of keratopathy. RESULTS: Visible keratopathy was found in 80% of the eyes. Keratopathy that caused impaired visual acuity was found in 26% of the eyes. The study displayed a significant correlation between the level of keratopathy and the patient's age. A significant correlation between the level of keratopathy and intraocular surgery exists. This is irrespective of the patient's age. The study also found that irrespective of the patient's age, a significant correlation between the level of keratopathy and impaired corneal sensitivity exists. CONCLUSIONS: This research identified the presence of visible keratopathy in 80% of eyes. In addition, 26% of eyes had a keratopathy level that caused visual disturbances. The study showed that the prevalence and severity of keratopathy increased with the patient's age. Further conclusions are that intraocular surgery increases the severity of keratopathy and that the severity of keratopathy is correlated to reduced corneal sensitivity. Finally, extreme care should be taken when selecting patients for intraocular surgery because this procedure can trigger the development of keratopathy.

Aniridia among children and teenagers in Sweden and Norway.

PURPOSE: To investigate patients under the age of 20 with aniridia in Sweden and Norway in order to estimate the prevalence of aniridia, to describe clinical signs and identify complications in the young, which will help improve diagnostic tools and treatment. METHODS: A thorough search for patients with aniridia (of all ages) was performed. Sixty-two of the 181 patients were under the age of 20. Fifty-two of them were examined and they constituted the study population. Patient history was obtained and all participants underwent clinical ophthalmologic examination, including photography. Blood samples were taken for mutation analysis. RESULTS: Epidemiological data are only based on the results in Sweden. The age-specific prevalence in Sweden was 1:47,000, male/female ratio was 0.57, mean age 12 years and median age 14 years. The proportion of sporadic cases including WAGR (Wilms tumour, Aniridia, Genitourinary abnormalities, Mental Retardation) and Gillespie syndrome (aniridia, cerebellar ataxia and mental retardation) was 48%. In the entire study population (Sweden and Norway), the mean visual acuity (VA) was 0.2 (range 0.04-0.9). We found VA < 0.3 in 80% and <0.1 in 18% of the patients. Twenty-two patients (42%) had one or more of the sight threatening complications such as cataract/lens luxation, corneal clouding or glaucoma. CONCLUSION: Descriptions of aniridia in the younger are rare. This study shows that aniridia seems to be more common than previously estimated and that some complications appear early in life. Watchfulness as regards these complications and regular examinations are essential even in the youngest.

Epidemiology of aniridia in Sweden and Norway.

PURPOSE: To investigate the epidemiology of aniridia in the populations of Sweden and Norway. METHODS: A thorough search for aniridia patients has been performed in Sweden and Norway. All participants had a clinical ophthalmological examination documented through photography. Blood samples were taken for mutation analysis and pedigrees were established. RESULTS: A total of 181 patients with aniridia were identified in the two countries. This gives an age-specific prevalence of 1:72,000 in the entire region, 1:70,000 in Sweden and 1:76,000 in Norway. A total of 124 individuals (69%) were examined. Male/female ratio was 0.94 (Sweden 0.85 and Norway 1.2). Mean age of the examined patients was 29 years and median age 25 years. We did not find any significant age difference between the two countries. The mean visual acuity (VA) was 0.19 (Sweden 0.19 and Norway 0.18).The number of families with more than one affected member was 31 and the number of sporadic cases was 40. CONCLUSION: We have done a thorough search of the literature, but we have found no earlier studies describing aniridia in an entire country and only a few reports from larger areas. We assume that most aniridia patients have been found and the aniridia prevalence of 1:72,000 can be regarded as well supported. Further studies on other aspects of aniridia are in progress, and information from these can contribute to guidelines for the care of patients with this rare but serious disease.