Importancia de la electrofisiología ocular en el diagnóstico de las distrofias retinianas / Importance of ocular electrophysiology in the diagnosis of retinal dystrophies

Antecedentes y objetivo: El diagnóstico de las distrofias retinianas es complejo y se basa en estudio oftalmológico completo, estudio genético y los estudios electrofisiológicos (EEF). En este estudio pretendemos evaluar el papel de las pruebas electrofisiológicas y del médico solicitante en el diagnóstico de las distrofias de retina. Materiales y métodos: Estudio observacional retrospectivo. Se seleccionaron 50 pacientes atendidos en el Servicio de Neurofisiología del Hospital Universitario Virgen Macarena. Se valoró el sexo, la edad, el hospital de origen, motivo por el que se solicitó los EEF, diagnóstico de presunción tras examen oftalmológico, EEF realizados, estudio genético y el diagnóstico definitivo tras realización de EEF. Se elaboró un sistema de clasificación que otorga a cada caso un valor comprendido entre 0 y 2, en función de la contribución de las pruebas electrofisiológicas al diagnóstico final. Resultados: La edad media fue 44,34 ± 18,03 años (60% mujeres). Retinosis pigmentaria, neuropatía óptica y enfermedad de Stargardt fueron los diagnósticos más frecuentes. Los EEF modificaron el diagnóstico de presunción en el 48% de los casos, confirmaron el diagnóstico en el 44% y no aportaron información en el 8%. La contribución de los EEF fue mayor en pacientes atendidos en el Hospital Universitario Virgen Macarena y cuando se solicitaban por hallazgos en la exploración (p = 0,001). Los falsos positivos para distrofia retiniana fueron del 60% en pacientes no valorados en dicho hospital. Conclusiones: Las pruebas electrofisiológicas y el manejo especializado de los pacientes con distrofias retinianas desempeñan un papel importante en el diagnóstico de estas patologías

Background and objective; The diagnosis of retinal dystrophies is complex and is based on complete ophthalmological study, genetic study and electrophysiological studies (EPS). In this study, we intend to evaluate the role of electrophysiological and medical tests in the diagnosis of retinal dystrophies. Material and methods: A retrospective observational study was conducted on 50 selected patients that attended the Neurophysiology Department of the University Hospital Virgen Macarena. An analysis was made of the variables that included, gender, age, referral hospital, reason for which the EPS was requested, applied EPS, genetic study, presumed diagnosis, and definitive diagnosis after EPS. A classification system was subsequently developed, which gives each case a value between 0 and 2, depending on the contribution of the electrophysiological tests to the final diagnosis. Results: The mean age was 44.34 ± 18.03 years (60% women). Retinitis pigmentosa (24%), optic neuropathy (12%), and Stargardt's disease (8%) were the most frequent diagnoses. The EPS modified the presumed diagnosis in 48% of the cases, confirmed the diagnosis in 44%, and did not provide any useful information in 8%. The contribution of the EPS was greater in patients seen in the HUVM and when requested by findings in the examination (P = .001). The false positives in the diagnosis of retinal dystrophy were 60% in patients not evaluated by the University Hospital Virgen Macarena. Conclusions: Electrophysiological test and specialised management of patients with retinal dystrophies play an important role in the diagnosis of these conditions

[Objective method to recognize warning signs in peripheral vitreoretinal dystrophies]. / Sposob opredeleniya priznakov prognosticheskoi opasnosti perifericheskikh vitreoretinal'nykh distrofii.

AIM: to compare the effectiveness of biomicroscopy (BMS) and optical coherence tomography (OCT) in recognizing prognostically unfavorable signs in peripheral vitreoretinal dystrophy (PVRD) patients. MATERIAL AND METHODS: A total of 131 cases of equatorial PVRD (91 eyes of 56 patients) were assessed. The mean patient's age was 24.7 years. The length of the anterior-posterior axis of the eyeball averaged 25.36±1.12 mm. Prevalence of particular warning signs in PVRD patients at BMS or OCT was comparatively analyzed. RESULTS: In 46 eyes with lattice dystrophy it was difficult to determine the presence of vitreoretinal traction at BMS; at OCT, areas of retinal adhesion to the posterior hyaloid membrane (PHM) along the edges of PVRD zones were revealed in all eyes. Of 31 eyes with «snail tracks¼ defects of the retina, 6 were diagnosed at BMS; in OCT scans of these patients, the PHM appeared firmly fixed along the edges of PVRD zones in all cases. As to horseshoe retinal tears (valve-like tears), BMS allowed to visualize vitreoretinal tractions in 7 of 12 eyes, while OCT revealed a tight contact between the PHM and the apex of the retinal flap in 11 of 12 eyes. In 7 eyes with retinoschisis we failed to detect any retinal traction at either BMS or OCT. In «non-differentiable¼ PVRD, BMS was also not able to reveal any vitreoretinal traction, while OCT was - in all 12 cases. CONCLUSION: OCT has proved much more effective than BMS in recognizing prognostically unfavorable signs in particular clinical forms of PVRD, such as vitreoretinal tractions, retinal defects, and intraretinal cavities.

Prevalence of generalized retinal dystrophy in Denmark.

PURPOSE: Generalized retinal dystrophy is a frequent cause of visual impairment and blindness in younger individuals and a subject of new clinical intervention trials. Nonetheless, there are few nation-wide population-based epidemiological data of generalized retinal dystrophy. The purpose of this study was to examine the prevalence and diagnostic spectrum of generalized retinal dystrophy in the Danish population. METHODS: A population-based cross-sectional study with data from the Danish Retinitis Pigmentosa Registry that comprises all patients in Denmark with generalized retinal and chorioretinal dystrophies from the 19th century to the present. Among 3076 registered cases, the primary diagnosis of generalized retinal dystrophy was assessed by chart review, including fundus photographs and electroretinograms. Demographic data on the Danish population were retrieved from Statistics Denmark. RESULTS: Of the 5,602,628 Danish citizens on January 1, 2013, 1622 patients were registered as having a generalized retinal dystrophy and were alive and living in Denmark, corresponding to a prevalence of 1:3,454. In 28% of cases the eye condition was part of a syndrome, while the remaining 72% had eye disease only. Aside from simplex cases (45%), the most common hereditary pattern was autosomal recessive (23%). CONCLUSION: This epidemiological survey demonstrates that the prevalence of generalized retinal dystrophy in the Danish population is 1:3454. Many of the dystrophies are the subjects of clinical intervention trials, and nation-wide epidemiological data can help assess the burden of the disease and the future need for treatment.

[Inherited retinal dystrophies: contributions of molecular genetics]. / Les dystrophies rétiniennes héréditaires : apports de la génétique moléculaire.

Inherited retinal dystrophies are Mendelian neurodegenerative conditions. The mutations of the responsible genes lead both to cell dysfunction and cell death in the retina. The majority of these diseases are responsible for a progressive vision loss ending in almost complete blindness. Recent breakthroughs in molecular genetics technologies (microchips, next generation sequencing) resulted in a much better understanding of these conditions. Their genetic heterogeneity is extremely large, with 191 causal genes disclosed today, knowing that this number will increase in the next years as a significant proportion of cases, especially those with retinitis pigmentosa, do not have mutations in the currently identified genes. A single phenotype is often caused by mutations in several different genes. In addition, exhaustive gene knowledge led to recognize gene-specific clinical features found in several different phenotypes and thus to propose a pathophysiological hypothesis available for experimental testing. Importantly, this vast field of knowledge opens the way to pre-clinical and clinical therapeutic trials, currently increasing exponentially, and eagerly awaited by the patients for whom the only issue until now was ineluctable blindness.

Mitochondrial retinal dystrophy associated with the m.3243A>G mutation.

OBJECTIVE: To describe the spectrum of retinal abnormalities associated with the m.3243A>G mutation in the mitochondrial MTTL1 gene and to analyze putative correlations among the severity of retinal abnormalities, disease severity in other organ systems, and heteroplasmy levels. DESIGN: Observational, cohort-based, cross-sectional study. PARTICIPANTS: Twenty-nine patients carrying the m.3243A>G mutation. METHODS: Extensive clinical examinations, including visual acuity testing, indirect ophthalmoscopy, color fundus photography, fundus autofluorescence (FAF), high-resolution optical coherence tomography (OCT), and central visual field analysis. In selected patients, Goldmann perimetry, fluorescein angiography, full-field electroretinography (ERG) and electro-oculography (EOG), and color vision testing were performed. Heteroplasmy levels of the m.3243A>G mutation were measured in leukocytes, urinary epithelial cells (UECs), and buccal mucosa. The Newcastle Mitochondrial Disease Adult Scale (NMDAS) score was measured for all patients. MAIN OUTCOME MEASURES: Age at onset, visual acuity, fundus appearance, FAF, OCT findings, systemic disease features, heteroplasmy levels, and NMDAS scores. RESULTS: Twenty-five of the 29 mutation carriers (86%) had retinal abnormalities that could be classified into 4 grades. Six patients (21%) had grade 1 retinal dystrophy with fine pigment abnormalities that were clearly visible with FAF and fluorescein angiography. Eleven patients (38%) had grade 2 abnormalities that were characterized by yellowish or mildly pigmented deposits in the early stage; in advanced grade 2, these pigment changes encompassed the entire macula and often encircled the optic disc. Six patients (21%) had grade 3 disease in which profound chorioretinal atrophy was present outside the fovea. Two patients (7%) with retinal abnormalities had grade 4 disease, in which the fovea was affected by atrophy, with marked loss of visual acuity. The grade of mitochondrial retinal dystrophy correlated significantly with both age (r = -0.483, P = 0.008) and visual acuity (r = -0.614, P < 0.001), whereas no correlation was observed with heteroplasmy level or overall disease involvement. CONCLUSIONS: Mitochondrial retinal dystrophy associated with the m.3243A>G mutation has specific characteristics that can be classified into 4 grades based on the findings on ophthalmoscopy, FAF, and OCT. However, because the maternal inheritance pattern can be masked and the systemic disease associations can be variable or even absent, the disease may be misdiagnosed.

[Genetic diagnostic testing in inherited retinal dystrophies]. / Genetische diagnostik bei erblichen netzhautdystrophien.

Inherited retinal dystrophies are clinically and genetically highly heterogeneous. They can be divided according to the clinical phenotype and course of the disease, as well as the underlying mode of inheritance. Isolated retinal dystrophies (i.e., retinitis pigmentosa, Leber's congenital amaurosis, cone and cone-rod dystrophy, macular dystrophy, achromatopsia, congenital stationary nightblindness) and syndromal forms (i.e., Usher syndrome, Bardet-Biedl syndrome) can be differentiated. To date almost 180 genes and thousands of distinct mutations have been identified that are responsible for the different forms of these blinding illnesses. Until recently, there was no adequate diagnostic genetic testing available. With the development of the next generation sequencing technologies, a comprehensive genetic screening analysis for all known genes for inherited retinal dystrophies has been established at reasonable costs and in appropriate turn-around times. Depending on the primary clinical diagnosis and the presumed mode of inheritance, different diagnostic panels can be chosen for genetic testing. Statistics show that in 55-80 % of the cases the genetic defect of the inherited retinal dystrophy can be identified with this approach, depending on the initial clinical diagnosis. The aim of any genetic diagnostics is to define the genetic cause of a given illness within the affected patient and family and thereby i) confirm the clinical diagnosis, ii) provide targeted genetic testing in family members, iii) enable therapeutic intervention, iv) give a prognosis on disease course and progression and v) in the long run provide the basis for novel therapeutic approaches and personalised medicine.