PRPH2-Related Retinal Dystrophies: Mutational Spectrum in 103 Families from a Spanish Cohort.

PRPH2, one of the most frequently inherited retinal dystrophy (IRD)-causing genes, implies a high phenotypic variability. This study aims to analyze the PRPH2 mutational spectrum in one of the largest cohorts worldwide, and to describe novel pathogenic variants and genotype-phenotype correlations. A study of 220 patients from 103 families recruited from a database of 5000 families. A molecular diagnosis was performed using classical molecular approaches and next-generation sequencing. Common haplotypes were ascertained by analyzing single-nucleotide polymorphisms. We identified 56 variants, including 11 novel variants. Most of them were missense variants (64%) and were located in the D2-loop protein domain (77%). The most frequently occurring variants were p.Gly167Ser, p.Gly208Asp and p.Pro221_Cys222del. Haplotype analysis revealed a shared region in families carrying p.Leu41Pro or p.Pro221_Cys222del. Patients with retinitis pigmentosa presented an earlier disease onset. We describe the largest cohort of IRD families associated with PRPH2 from a single center. Most variants were located in the D2-loop domain, highlighting its importance in interacting with other proteins. Our work suggests a likely founder effect for the variants p.Leu41Pro and p.Pro221_Cys222del in our Spanish cohort. Phenotypes with a primary rod alteration presented more severe affectation. Finally, the high phenotypic variability in PRPH2 hinders the possibility of drawing genotype-phenotype correlations.

Retinal Toxicity of Medical Devices Used during Vitreoretinal Surgery: A Critical Overview.

Retinal toxicity/biocompatibility of medical devices in direct contact with the retina is an important subject for clinicians and scientists. As these effects are not very frequent, there is also a relative lack of information for many clinicians. The past has taught us multiple times that there is a significant safety problem associated with severe loss of vision in affected patients. In this review, we want to classify medical products that are used in the back of the eye, describe recent examples of toxicity, critically reflect on the regulations that exist and suggest improvements that can be done to ensure patient safety without hindering innovation. METHODS: Critical review of the recent papers and personal experience of the authors in this issue. Medical devices used in the back of the eye and recent examples of toxicity are described, regulations that exist are critically reflected and improvements suggested that can ensure patient safety without hindering innovation. RESULTS: There is clear evidence of toxicity after intraocular surgery in any category. Some cytotoxic indirect methods have failed in detecting this toxicity. Some ISO rules do not seem appropriate. Postmarketing safety is missing. There is little data on this issue. CONCLUSIONS: The absence of a clear regulation of the production, purification and evaluation of the toxic effects of the medical devices supposes the possibility that products are not sufficiently safe to obtain the CE mark.

A Cost-Effective Mutation Screening Strategy for Inherited Retinal Dystrophies.

OBJECTIVE: We developed a simple, time- and cost-effective Excel-based genetic screening strategy for the diagnosis of inherited retinal dystrophies (IRD). DESIGN: 76 patients diagnosed with IRD and 112 nonaffected family members, from 55 unrelated families, were included. DNA samples were analyzed using Axiom Exome Genotyping Array Plates (Affymetrix) that contain over 300,000 genetic variants, including more than 5,000 variants present in 181 genes involved in IRD. We used a simple Excel-based data mining strategy in order to screen IRD variants likely involved in the development of IRD. RESULTS: A total of 5 relevant genetic variants were found in 5 IRD genes. Four variants were reported either as pathogenic or with a prediction of probably damaging, and 1 variant was reported to affect a regulatory region. These variants were present in 14 patients and in 11 carriers, in 10 unrelated families. CONCLUSION: Using our Excel-based data screening strategy, we were able to assign likely genetic diagnoses in a fast and cost-effective manner to over 18% of patients analyzed, with a comparable ratio of genetic findings to that reported with retina-specific arrays for about 1/5 of the cost. Our approach proved efficient in reducing costs and time for IRD diagnosis as a first tier genetic screening method.

Genetic high throughput screening in Retinitis Pigmentosa based on high resolution melting (HRM) analysis.

Retinitis Pigmentosa (RP) involves a group of genetically determined retinal diseases caused by a large number of mutations that result in rod photoreceptor cell death followed by gradual death of cone cells. Most cases of RP are monogenic, with more than 80 associated genes identified so far. The high number of genes and variants involved in RP, among other factors, is making the molecular characterization of RP a real challenge for many patients. Although HRM has been used for the analysis of isolated variants or single RP genes, as far as we are concerned, this is the first study that uses HRM analysis for a high-throughput screening of several RP genes. Our main goal was to test the suitability of HRM analysis as a genetic screening technique in RP, and to compare its performance with two of the most widely used NGS platforms, Illumina and PGM-Ion Torrent technologies. RP patients (n = 96) were clinically diagnosed at the Ophthalmology Department of Donostia University Hospital, Spain. We analyzed a total of 16 RP genes that meet the following inclusion criteria: 1) size: genes with transcripts of less than 4 kb; 2) number of exons: genes with up to 22 exons; and 3) prevalence: genes reported to account for, at least, 0.4% of total RP cases worldwide. For comparison purposes, RHO gene was also sequenced with Illumina (GAII; Illumina), Ion semiconductor technologies (PGM; Life Technologies) and Sanger sequencing (ABI 3130xl platform; Applied Biosystems). Detected variants were confirmed in all cases by Sanger sequencing and tested for co-segregation in the family of affected probands. We identified a total of 65 genetic variants, 15 of which (23%) were novel, in 49 out of 96 patients. Among them, 14 (4 novel) are probable disease-causing genetic variants in 7 RP genes, affecting 15 patients. Our HRM analysis-based study, proved to be a cost-effective and rapid method that provides an accurate identification of genetic RP variants. This approach is effective for medium sized (<4 kb transcript) RP genes, which constitute over 80% of the total of known RP genes.

ABCA4 c.6480-35A>G, a novel branchpoint variant associated with Stargardt disease.

Introduction: Inherited retinal dystrophies (IRDs) can be caused by variants in more than 280 genes. The ATP-binding cassette transporter type A4 (ABCA4) gene is one of these genes and has been linked to Stargardt disease type 1 (STGD1), fundus flavimaculatus, cone-rod dystrophy (CRD), and pan-retinal CRD. Approximately 25% of the reported ABCA4 variants affect RNA splicing. In most cases, it is necessary to perform a functional assay to determine the effect of these variants. Methods: Whole genome sequencing (WGS) was performed in one Spanish proband with Stargardt disease. The putative pathogenicity of c.6480-35A>G on splicing was investigated both in silico and in vitro. The in silico approach was based on the deep-learning tool SpliceAI. For the in vitro approach we used a midigene splice assay in HEK293T cells, based on a previously established wild-type midigene (BA29) containing ABCA4 exons 46 to 48. Results: Through the analysis of WGS data, we identified two candidate variants in ABCA4 in one proband: a previously described deletion, c.699_768+342del (p.(Gln234Phefs*5)), and a novel branchpoint variant, c.6480-35A>G. Segregation analysis confirmed that the variants were in trans. For the branchpoint variant, SpliceAI predicted an acceptor gain with a high score (0.47) at position c.6480-47. A midigene splice assay in HEK293T cells revealed the inclusion of the last 47 nucleotides of intron 47 creating a premature stop codon and allowed to categorize the variant as moderately severe. Subsequent analysis revealed the presence of this variant as a second allele besides c.1958G>A p.(Arg653His) in an additional Spanish proband in a large cohort of IRD cases. Conclusion: A splice-altering effect of the branchpoint variant, confirmed by the midigene splice assay, along with the identification of this variant in a second unrelated individual affected with STGD, provides sufficient evidence to classify the variant as likely pathogenic. In addition, this research highlights the importance of studying non-coding regions and performing functional assays to provide a conclusive molecular diagnosis.

Endophthalmitis following intravitreal injections.

BACKGROUND: To report the clinical features, culture results, management and visual outcome of patients with endophthalmitis following intravitreal injections. METHODS: Retrospective review of all patients with suspected endophthalmitis after intravitreal injections treated with intravitreal antibiotics (teicoplanin and ciprofloxacin) at a referral centre between January 2003 and December 2010. RESULTS: Nineteen cases that had aqueous or vitreous biopsy were identified. Nine had negative culture. Ten had positive culture; Staphylococcus species in 4/10, Streptococcus species in 4/10, E. coli in 1/10 and gram-negative bacilli in 1/10. Symptoms developed within the first 48 hours in all. One of ten culture-positive cases had no pain on presentation, while 5/9 patients with negative culture reported pain. Initial treatment consisted of intravitreal antibiotics in all cases, 6/19 cases required a second intravitreal antibiotic injection, 4/19 underwent vitrectomy as secondary therapy. At the last follow up, 7/19 patients had visual acuity of 6/18 or better, 9/19 had visual acuity of 6/60 or worse. CONCLUSION: The overall numbers of patients with endophthalmitis following intravitreal injections has risen dramatically over the past years. In contrast to earlier reports of multicentre studies, outcome of patients is relatively poor in the current treatment settings. We did not find clinical features useful in identifying cases with negative culture.

Retrospective review of 50 eyes with long-term silicone oil tamponade for more than 12 months.

BACKGROUND: Silicone oil (SO) is an established tamponade in treating complex vitreoretinal diseases. Although SO is intended to be removed after several weeks to months, permanent SO might be unavoidable in a small subgroup of patients with an extremely complicated clinical course. The aim of this study is to describe the long-term effects of intraocular SO tamponade. METHODS: This retrospective study included 50 patients with intraocular SO (Oxane 5700 Bausch & Lomb, Kingston-upon-Thames, UK) for at least 12 months. The most common reasons for long-term SO tamponade were: retinal re-detachment (re-RD), proliferative diabetic retinopathy (PDR), ocular trauma, and persistent hypotony. RESULTS: Mean age was 59.2 ± 18.4 years, and mean duration of silicone oil in the eye was 54.5 ± 58.6 months (median, 30 months). The average number of previous surgeries were 2.2 ± 1.5. Anatomic success was achieved in 37/50 (74%) of patients. Visual acuities (logMAR) were 1.8 ± 0.6, 1.6 ± 0.6, 2 ± 0.7 and intraocular pressures (mmHg) were 15.6 ± 7, 15.7 ± 5.5, 16.5 ± 7.1 at 3 months, 1 year and at last follow-up respectively. The main long-term silicone-oil-related complications observed were: band keratopathy (8%), corneal decompensation (12%), iris rubeosis (14%), and optic neuropathy (28%). Forty percent of patients achieved ambulatory vision in the SO-filled eye at final follow-up. CONCLUSION: Long-term silicone oil can be a last-resort option in selected patients with severe vitreoretinal disease. Anterior and posterior segment complications did occur at significant rates. Forty percent of our patients maintained ambulatory vision. The actual number of patients that achieved satisfactory stereopsis and benefited functionally from long-term SO was much less [7/50 (14%)].

Safety and efficacy of a novel retrograde route for femoral bone graft harvesting by Reamer-Irrigator-Aspirator: a pilot study on 24 patients.

BACKGROUND: The Reamer-Irrigator-Aspirator system was initially developed to reduce fat embolism and thermic necrosis during reamed intramedullary nail fixation of femoral shaft fractures. Currently, this system is used in extended applications including accessing large volume of autologous bone graft, as alternative for iliac crest harvesting. Antegrade femoral bone graft harvesting using the Reamer-Irrigator-Aspirator system is considered the standard technique. The aim of our study is to evaluate the efficacy (bone graft volume) and the complications (blood loss, postoperative pain, and incidence of iatrogenic fractures) of the Reamer-Irrigator-Aspirator system through the retrograde femoral route in a series of patients with post-traumatic bone defects or nonunions. METHODS: A non-controlled single center retrospective observational cohort study was conducted in a level1 trauma center to evaluate all patients who were treated using the RIA system. Between November 2015 and May 2019, 24 patients (8 women and 16 men; mean age: 41 years [range 27-55 years]) with bone defects or nonunions underwent bone graft harvesting using the Reamer-Irrigator-Aspirator system through retrograde femoral route. Postoperative pain, complications, and bone graft volume were analyzed. Inclusion criteria was patients older than 18 years with a diagnosis of post-traumatic bone defect or associated tibial or femoral nonunion, with minimum 6-months follow, treated using the RIA. We hypothesized that the retrograde route of the RIA system is a safe and efficacious method for bone harvesting. RESULTS: The average volume of collected graft was 45 cc (range 30-60 cc). In 83% of the cases, bone grafting was sufficient, while in 17% it was necessary to add iliac crest bone graft to completely fill the bone defect. A mean drop in postoperative hemoglobin of 4.1 g / dL (range 0.5-6.0 g / dL) was evidenced. In 4 cases (33%), a unit of packed red blood cells was required. Regarding postoperative pain, visual analogue scale after 3 months postoperatively was 1.6 in average. After 6 months, the value has decreased to 0.4. There were no perioperative or postoperative complications at 6-month follow-up. CONCLUSION: In this limited case series, large volumes of bone graft were harvested using the retrograde route of the RIA system and there were no intra-/ postoperative complications observed at 6-month follow-up. Therefore this novel technique appears safe and efficacious. However, it's important to highlight that future prospective controlled studies are necessary to validate the insights from this pilot study.

Assessing the Utility and Patient Satisfaction of Virtual Retina Clinics During COVID-19 Pandemic.

PURPOSE: To explore whether the virtual retina clinic (VRC) has been a useful and safe platform for monitoring retinal diseases during the COVID-19 pandemic and assessing patient satisfaction. METHODS: A prospective observational study was conducted for patients with stable retinal diseases in Donostia University Hospital's Ophthalmology Service during the pandemic. All patients were assessed in the VRC with optical coherence tomography of the macula and widefield retinography, plus visual field tests in hydroxychloroquine retinopathy screenings. The VRC´s effectiveness was evaluated with repeat blind assessments and patient satisfaction with an adapted SERVQUAL scale. RESULTS: The most common diseases were diabetic retinopathy (30.3%) and age-related macular degeneration (21.8%). Most patients (74%) were eligible to continue in the VRC, 19.3% were referred to face-to-face (F2F) appointments and 6.6% were discharged. Patients underwent repeat blind assessments in F2F appointments to monitor VRC performance in 23.7% of the cases. The sensitivity to detect disease progression was 100%. The specificity was 80.1%. The VRC took half the time. The patient overall satisfaction rating was 9.8/10. CONCLUSION: The VRC, as an additional platform, supports F2F appointments. Almost three-quarters of patients could continue being safely seen in the VRC. The virtual approach decreases SARS-CoV-2 exposure. Patient satisfaction is very good. TRANSLATIONAL RELEVANCE: The VRC enables us to attend patients safely with decreased SARS-CoV-2 exposure.

Subretinal Injection Techniques for Retinal Disease: A Review.

Inherited retinal dystrophies (IRDs) affect an estimated 1 in every 2000 people, this corresponding to nearly 2 million cases worldwide. Currently, 270 genes have been associated with IRDs, most of them altering the function of photoreceptors and retinal pigment epithelium. Gene therapy has been proposed as a potential tool for improving visual function in these patients. Clinical trials in animal models and humans have been successful in various types of IRDs. Recently, voretigene neparvovec (Luxturna®) has been approved by the US Food and Drug Administration for the treatment of biallelic mutations in the RPE65 gene. The current state of the art in gene therapy involves the delivery of various types of viral vectors into the subretinal space to effectively transduce diseased photoreceptors and retinal pigment epithelium. For this, subretinal injection is becoming increasingly popular among researchers and clinicians. To date, several approaches for subretinal injection have been described in the scientific literature, all of them effective in accessing the subretinal space. The growth and development of gene therapy give rise to the need for a standardized procedure for subretinal injection that ensures the efficacy and safety of this new approach to drug delivery. The goal of this review is to offer an insight into the current subretinal injection techniques and understand the key factors in the success of this procedure.

Incidence and Risk Factors Affecting the Recurrence of Primary Retinal Detachment in a Tertiary Hospital in Spain.

(1) Objective: To determine the incidence, visual outcomes and risk factors associated with the recurrence of primary retinal detachment (RD) in a tertiary hospital. (2) Methods: A retrospective observational study was conducted, and data were collected on all eyes diagnosed with primary RD between January 2017 and December 2020. A detailed database was generated with data on anatomic and visual outcomes, and surgical technique information, for all the cases. (3) Results: 570 eyes with primary RD were included. Mean annual incidence of primary RD was 21.8 cases per 100,000 inhabitants. Mean follow-up time was 465 (±410.5) days. Mean time to redetachment was 114.4 (±215.8) days, with the median being 35 days. Statistically significant variables related to a higher risk of recurrence were: male sex (p = 0.04), type of tamponade (p = 0.01), surgeon (p = 0.035), inferonasal (p = 0.002) and inferotemporal (p = 0.032) involvement, complex RD (p < 0.001) and ocular comorbidity (p < 0.001). More satisfactory final visual acuity (VA) in patients not suffering redetachment was associated with shorter duration of central vision loss. (4) Conclusions: Sex, type of tamponade, inferior detachment, RD complexity, surgeon and ocular comorbidity were identified as prognostic factors for recurrence. Worse final postoperative VA was found in patients referring central vision loss for more than 4 days before surgery.

Is there a role for long-term silicone oil tamponade for more than twelve months in vitreoretinal surgery?

Despite modern and sophisticated vitreoretinal techniques, the authors are convinced that an underreported patient group exists, for whom long-term silicone oil tamponade is unavoidable. We conducted a literature review of the current evidence base in order to provide guidance on the ocular tolerance and side effects of long-term silicone oil, weighing up benefits against complications as well as providing an outlook on future silicone oils with improved physical properties. We advocate the removal of silicone oil in all cases; however, one has to recognise that long-term silicone oil tamponade may have to be considered as a measure of last resort for selected patients. There is a clinical need to develop novel, emulsification-resistant tamponades.

NEUROPATHY, ATAXIA, AND RETINITIS PIGMENTOSA SYNDROME: A MULTIDISCIPLINARY DIAGNOSIS.

PURPOSE: To report a case of neuropathy, ataxia, and retinitis pigmentosa syndrome, a rare and undiagnosed disease in ophthalmology due to the need for multidisciplinary evaluation. METHODS: Multimodal testing was performed, including neurologic, ophthalmologic, and genetic assessments. The neurologic tests comprised electromyogram and muscle biopsy; the ophthalmologic examination consisted of slit-lamp and fundus examinations, optical coherence tomography, visual field testing, and electrophysiology tests such as a full-field electroretinogram and multifocal electroretinogram; and genetic tests were performed for spinocerebellar ataxia. In addition, the patient underwent magnetic resonance imaging, an electrocardiogram, cerebrospinal fluid analysis with lactate levels, and a blood workup including antineuronal, antithyroid peroxidase, antinuclear, antimitochondrial, and antitransglutaminase antibodies and fat-soluble vitamins (A, D, E, K). RESULTS: The ocular fundus examination showed bone spicules with retinal pigment epithelium alteration, optic nerve pallor, and arterial attenuation. Optical coherence tomography demonstrated macular atrophy. Visual field testing revealed concentric reduction. Electrophysiology examinations showed involvement of rods and cones in both eyes. The muscle biopsy was compatible with mitochondrial disease, and electromyogram demonstrated sensory axonal damage. However, genetic tests for spinocerebellar ataxia were negative. Magnetic resonance imaging showed cerebellar atrophy, whereas the electrocardiogram did not detect any abnormalities. Cerebrospinal fluid lactate levels were above normal but antibody levels in blood were normal. CONCLUSION: This is the first report of macular atrophy demonstrated by optical coherence tomography in a patient with neuropathy, ataxia, and retinitis pigmentosa syndrome. For the diagnosis, a multidisciplinary team including a neurologist, a geneticist, and an ophthalmologist was essential. Patients with suspected mitochondrial disease could greatly benefit from an ophthalmology examination like that conducted in this case because it was the key factor that led to the suspicion of syndromic disease, and ultimately the diagnosis.

Author Correction: A new approach based on targeted pooled DNA sequencing identifies novel mutations in patients with Inherited Retinal Dystrophies.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Foldable toric intraocular lens for astigmatism correction in cataract patients.

PURPOSE: To evaluate the results of AcrySof toric intraocular lens (IOL) (Alcon) implantation to correct preexisting astigmatism in patients having cataract surgery. SETTING: Ophthalmology Service, Donostia Hospital, San Sebastián, Spain. METHODS: This prospective observational study included 30 eyes of 15 consecutive patients with more than 1.00 diopter (D) of preexisting corneal astigmatism having cataract surgery. Bilateral implantation of the AcrySof toric IOL was performed after phacoemulsification. The uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), residual refractive sphere, residual keratometric and refractive cylinders, and toric IOL axis were measured. RESULTS: The UCVA was 20/40 or better in 93.3% of eyes and 20/25 or better in 66.6%. All eyes achieved 20/25 or better BCVA. The mean refractive cylinder decreased significantly after surgery from -2.34 D +/- 1.28 (SD) to -0.72 +/- 0.43 D (P<.01). Vector analysis of attempted versus achieved correction showed that 100% of eyes were within +/-1.00 D and 80% and 93.9% were within +/-0.50 D for J(0) and J(45), respectively. The mean toric IOL axis rotation was 3.63 +/- 3.11 degrees, with rotation less than 10 degrees in 96.7% of eyes. CONCLUSIONS: The results indicate that phacoemulsification and posterior chamber AcrySof toric IOL implantation is an effective option to correct preexisting astigmatism in cataract surgery. The AcrySof toric IOL showed good rotational stability.

A new approach based on targeted pooled DNA sequencing identifies novel mutations in patients with Inherited Retinal Dystrophies.

Inherited retinal diseases (IRD) are a heterogeneous group of diseases that mainly affect the retina; more than 250 genes have been linked to the disease and more than 20 different clinical phenotypes have been described. This heterogeneity both at the clinical and genetic levels complicates the identification of causative mutations. Therefore, a detailed genetic characterization is important for genetic counselling and decisions regarding treatment. In this study, we developed a method consisting on pooled targeted next generation sequencing (NGS) that we applied to 316 eye disease related genes, followed by High Resolution Melting and copy number variation analysis. DNA from 115 unrelated test samples was pooled and samples with known mutations were used as positive controls to assess the sensitivity of our approach. Causal mutations for IRDs were found in 36 patients achieving a detection rate of 31.3%. Overall, 49 likely causative mutations were identified in characterized patients, 14 of which were first described in this study (28.6%). Our study shows that this new approach is a cost-effective tool for detection of causative mutations in patients with inherited retinopathies.

High prevalence of mutations affecting the splicing process in a Spanish cohort with autosomal dominant retinitis pigmentosa.

Retinitis pigmentosa is the most frequent group of inherited retinal dystrophies. It is highly heterogeneous, with more than 80 disease-causing genes 27 of which are known to cause autosomal dominant RP (adRP), having been identified. In this study a total of 29 index cases were ascertained based on a family tree compatible with adRP. A custom panel of 31 adRP genes was analysed by targeted next-generation sequencing using the Ion PGM platform in combination with Sanger sequencing. This allowed us to detect putative disease-causing mutations in 14 out of the 29 (48.28%) families analysed. Remarkably, around 38% of all adRP cases analysed showed mutations affecting the splicing process, mainly due to mutations in genes coding for spliceosome factors (SNRNP200 and PRPF8) but also due to splice-site mutations in RHO. Twelve of the 14 mutations found had been reported previously and two were novel mutations found in PRPF8 in two unrelated patients. In conclusion, our results will lead to more accurate genetic counselling and will contribute to a better characterisation of the disease. In addition, they may have a therapeutic impact in the future given the large number of studies currently underway based on targeted RNA splicing for therapeutic purposes.

Co-isolation of Vahlkampfia and acanthamoeba in acanthamoeba-like keratitis in a Spanish population.

PURPOSE: To report the co-isolation incidence of Acanthamoeba and Vahlkampfia in amoebic keratitis from a tertiary care institution in Madrid, Spain. METHODS: In this retrospective case series, 7 eyes of 7 consecutive patients with culture-proven or polymerase chain reaction-positive Acanthamoeba keratitis were seen at a tertiary care institution from January 2010 to April 2011, and their charts were reviewed. RESULTS: Two of 7 patients showed mixed Acanthamoeba and Vahlkampfia keratitis. Good clinical response to the treatment was strongly correlated with early diagnosis, whereas delayed diagnosis resulted in poor response to the treatment in single or mixed infection. CONCLUSIONS: Co-isolation of Vahlkampfia and Acanthamoeba in Acanthamoeba-like keratitis has recently been detected in our population. This finding should raise awareness of the existence of other amoeba different from Acanthamoeba causing keratitis. There are not enough cases yet to determine the impact of mixed amoebic keratitis in the prognosis of this disease.

Current mutation discovery approaches in Retinitis Pigmentosa.

With a worldwide prevalence of about 1 in 3500-5000 individuals, Retinitis Pigmentosa (RP) is the most common form of hereditary retinal degeneration. It is an extremely heterogeneous group of genetically determined retinal diseases leading to progressive loss of vision due to impairment of rod and cone photoreceptors. RP can be inherited as an autosomal-recessive, autosomal-dominant, or X-linked trait. Non-Mendelian inheritance patterns such as digenic, maternal (mitochondrial) or compound heterozygosity have also been reported. To date, more than 65 genes have been implicated in syndromic and non-syndromic forms of RP, which account for only about 60% of all RP cases. Due to this high heterogeneity and diversity of inheritance patterns, the molecular diagnosis of syndromic and non-syndromic RP is very challenging, and the heritability of 40% of total RP cases worldwide remains unknown. However new sequencing methodologies, boosted by the human genome project, have contributed to exponential plummeting in sequencing costs, thereby making it feasible to include molecular testing for RP patients in routine clinical practice within the coming years. Here, we summarize the most widely used state-of-the-art technologies currently applied for the molecular diagnosis of RP, and address their strengths and weaknesses for the molecular diagnosis of such a complex genetic disease.

Therapeutic challenges to retinitis pigmentosa: from neuroprotection to gene therapy.

Syndromic retinitis pigmentosa (RP) is the result of several mutations expressed in rod photoreceptors, over 40 of which have so far been identified. Enormous efforts are being made to relate the advances in unraveling the patho-physiological mechanisms to therapeutic approaches in animal models, and eventually in clinical trials on humans. This review summarizes briefly the current clinical management of RP and focuses on the new exciting treatment possibilities. To date, there is no approved therapy able to stop the evolution of RP or restore vision. The current management includes an attempt at slowing down the degenerative process by vitamin supplementation, trying to treat ocular complications and to provide psychological support to blind patients. Novel therapeutic may be tailored dependant on the stage of the disease and can be divided in three groups. In the early stages, when there are surviving photoreceptors, the first approach would be to try to halt the degeneration by correction of the underlying biochemical abnormality in the visual cycle using gene therapy or pharmacological treatment. A second approach aims to cope with photoreceptor cell death using neurotrophic growth factors or anti-apoptotic factors, reducing the production of retino-toxic molecules, and limiting oxidative damage. In advanced stages, when there are few or no functional photoreceptors, strategies that may benefit include retinal transplantation, electronic retinal implants or a newly described optogenetic technique using a light-activated channel to genetically resensitize remnant cone-photoreceptor cells.