Proposed therapy, developed in a Pcdh15-deficient mouse, for progressive loss of vision in human Usher Syndrome

Usher syndrome type I (USH1) is characterized by deafness, vestibular areflexia and progressive retinal degeneration. The protein-truncating p.Arg245* founder variant of PCDH15 (USH1F) has an ~2% carrier frequency amongst Ashkenazi Jews accountings for ~60% of their USH1 cases. Here, longitudinal phenotyping in thirteen USH1F individuals revealed progressive retinal degeneration, leading to severe vision loss with macular atrophy by the sixth decade. Half of the affected individuals were legally blind by their mid-fifties. The mouse Pcdh15R250X variant is equivalent to human p.Arg245*. Homozygous Pcdh15R250X mice also have visual deficits and aberrant light-dependent translocation of the phototransduction cascade proteins, arrestin and transducin. Retinal pigment epithelium- (RPE) specific retinoid cycle proteins, RPE65 and CRALBP, were also reduced in Pcdh15R250X mice, indicating a dual role for protocadherin-15 in photoreceptors and RPE. Exogenous 9-cis retinal improved ERG amplitudes in Pcdh15R250X mice, suggesting a basis for a clinical trial of FDA approved retinoids to preserve vision in USH1F patients.

Cryo-EM structures of the ABCA4 importer reveal mechanisms underlying substrate binding and Stargardt disease

ABCA4 is an ATP-binding cassette (ABC) transporter that flips N-retinylidene-phosphatidylethanolamine (N-Ret-PE) from the lumen to the cytoplasmic leaflet of photoreceptor membranes. Loss-of-function mutations cause Stargardt disease (STGD1), a macular dystrophy associated with severe vision loss. To define the mechanisms underlying substrate binding and STGD1, we determine the cryo-EM structure of ABCA4 in its substrate-free and bound states. The two structures are similar and delineate an elongated protein with the two transmembrane domains (TMD) forming an outward facing conformation, extended and twisted exocytoplasmic domains (ECD), and closely opposed nucleotide binding domains. N-Ret-PE is wedged between the two TMDs and a loop from ECD1 within the lumen leaflet consistent with a lateral access mechanism and is stabilized through hydrophobic and ionic interactions with residues from the TMDs and ECDs. Our studies provide a framework for further elucidating the molecular mechanism associated with lipid transport and disease and developing promising disease interventions.

Supramolecular Host–Guest Hydrogels for Corneal Regeneration

Over 6.2 million people worldwide suffer from moderate to severe vision loss due to corneal disease. While transplantation with allogenic donor tissue is sight-restoring for many patients with corneal blindness, this treatment modality is limited by long waiting lists and high rejection rates, particularly in patients with severe tissue damage and ocular surface pathologies. Hydrogel biomaterials represent a promising alternative to donor tissue for scalable, nonimmunogenic corneal reconstruction. However, implanted hydrogel materials require invasive surgeries and do not precisely conform to tissue defects, increasing the risk of patient discomfort, infection, and visual distortions. Moreover, most hydrogel crosslinking chemistries for the in situ formation of hydrogels exhibit off-target effects such as cross-reactivity with biological structures and/or result in extractable solutes that can have an impact on wound-healing and inflammation. To address the need for cytocompatible, minimally invasive, injectable tissue substitutes, host–guest interactions have emerged as an important crosslinking strategy. This review provides an overview of host–guest hydrogels as injectable therapeutics and highlights the potential application of host–guest interactions in the design of corneal stromal tissue substitutes.

Toward the Treatment of Inherited Diseases of the Retina Using CRISPR-Based Gene Editing

Inherited retinal dystrophies [IRDs] are a common cause of severe vision loss resulting from pathogenic genetic variants. The eye is an attractive target organ for testing clinical translational approaches in inherited diseases. This has been demonstrated by the approval of the first gene supplementation therapy to treat an autosomal recessive IRD, RPE65-linked Leber congenital amaurosis (type 2), 4 years ago. However, not all diseases are amenable for treatment using gene supplementation therapy, highlighting the need for alternative strategies to overcome the limitations of this supplementation therapeutic modality. Gene editing has become of increasing interest with the discovery of the CRISPR-Cas9 platform. CRISPR-Cas9 offers several advantages over previous gene editing technologies as it facilitates targeted gene editing in an efficient, specific, and modifiable manner. Progress with CRISPR-Cas9 research now means that gene editing is a feasible strategy for the treatment of IRDs. This review will focus on the background of CRISPR-Cas9 and will stress the differences between gene editing using CRISPR-Cas9 and traditional gene supplementation therapy. Additionally, we will review research that has led to the first CRISPR-Cas9 trial for the treatment of CEP290-linked Leber congenital amaurosis (type 10), as well as outline future directions for CRISPR-Cas9 technology in the treatment of IRDs.

Socio-economic disparity in visual impairment from cataract

AIM: To investigate the association of visual impairment from cataract with human development index (HDI) by years lived with disability (YLDs). METHODS: Published data on national age-standardized YLD rates caused by cataract and national HDIs in 2019 were obtained. Age-standardized YLD rates from 1990 to 2019 were analyzed to explore cataract burden among patients with different income levels. Age-standardized YLD rates in different HDI groups were compared by different degrees of visual impairment. Association between national age-standardized YLD rates and HDI in 2019 was analyzed. RESULTS: The age-standardized YLD rates of populations with visual impairment or blindness due to cataract declined from 1990 to 2019, especially among those with lower middle income. Multiple comparison tests revealed that countries with low HDI had significantly higher age-standardized YLD rates of blindness due to cataract than those with high and very high HDI (P<0.001). The age-standardized YLD rates of populations with blindness (β= -0.588, P<0.001), severe vision loss (β=-0.378, P<0.001), and moderate vision loss (β=-0.389, P<0.001) inversely correlated with HDI. CONCLUSION: Age-standardized YLD rates caused by cataract have declined since 1990. The burden of visual impairment due to cataract inversely correlate with national socioeconomic development and is more concentrated in countries with low HDI than those with high HDI, especially among the blind. These findings highlight the need to provide additional cataract services and cataract surgery coverage to developing countries to decrease the burden of avoidable blindness caused by cataract.

Effects of the First COVID-19 Lockdown on Ophthalmological Patient Care

Purpose To determine the effect of lockdown on medical care, with the example of ophthalmology. Methods Patients in a period during the first lockdown were compared to a non-lockdown period, with a total of 12 259 patients included in an observational study. Changes in different areas (elective, emergency, inpatients, surgeries) and eye care subspecialties were compared. Emergency patients were analyzed according to severity and urgency. Patients showing hints requiring treatment for urgent cardiovascular diseases were determined. Differences in patients who would have suffered severe vision loss without treatment were identified and the QALY (quality-adjusted life years) loss was determined accordingly. A model to prioritize patient visits after the end of lockdown or in future lockdown scenarios was developed. Data were collected at the University Eye Hospital LMU Munich and patient files were reviewed individually by ophthalmologists. Results The average patient number decreased by − 59.4% (p < 0.001), with a significant loss in all areas (elective, emergency, inpatients, surgeries; p < 0.001). There was a decline of − 39.6% for patients at high risk/high severity. Patients with indications of a risk factor of future stroke declined significantly (p = 0.003). QALY loss at the university eye hospital was 171, which was estimated to be 3160 – 24 143 for all of Germany. Working up high losses of outpatients during these 8 weeks of projected lockdown in Germany would take 7 – 23 weeks under normal circumstances, depending on ophthalmologist density. The prioritization model can reduce morbidity by up to 78%. Conclusion There was marked loss of emergency cases and patients with chronic diseases. Making up for the losses in examinations and treatments will theoretically take weeks to months. To reduce the risk of morbidity, we recommend a prioritization model for rescheduling and future lockdown scenarios.

Susceptibility of bacterial endophthalmitis isolates to vancomycin, ceftazidime, and amikacin

Bacterial endophthalmitis is a rare intraocular infection, and prompt administration of intravitreal antibiotics is crucial for preventing severe vision loss. The retrospective study is to investigate the in vitro susceptibility to the antibiotics vancomycin, amikacin, and ceftazidime of bacterial endophthalmitis isolates in specimens at a tertiary referral center from January 1996 to April 2019 in Taiwan. Overall, 450 (49.9%) isolates were Gram positive, 447 (49.6%) were Gram negative, and 4 (0.4%) were Gram variable. In Gram-positive isolates, coagulase-negative staphylococci were the most commonly cultured bacteria (158, 35.1%), followed by Streptococci (100, 22.2%), Enterococci (75, 16.7%), and Staphylococcus aureus (70, 15.6%). In Gram-negative isolates, they were Klebsiella pneumoniae (166, 37.1%) and Pseudomonas aeruginosa (131, 29.3%). All Gram-positive organisms were susceptible to vancomycin, with the exception of one Enterococcus faecium isolate (1/450, 0.2%). Of the Gram-negative isolates, 96.9% and 93.7% were susceptible to ceftazidime and amikacin, respectively. Nine isolates (9/447, 2.0%) were multidrug-resistant Gram-negative bacteria, comprising K. pneumoniae (4/164, 2.4%), Acinetobacter baumannii (2/3, 67%), and Stenotrophomonas maltophilia (3/18, 17%). In conclusion, in vitro susceptibility testing revealed that vancomycin remains the suitable antibiotic treatment for Gram-positive endophthalmitis. Ceftazidime and amikacin provide approximately the same degree of Gram-negative coverage. Multidrug-resistant bacterial endophthalmitis was uncommon.

Rare occurrence of severe blindness and deafness in Friedreich ataxia: a case report

Background Friedreich ataxia is the most frequent hereditary ataxia worldwide. Subclinical visual and auditory involvement has been recognized in these patients, with co-occurrence of severe blindness and deafness being rare. Case report We describe a patient, homozygous for a 873 GAA expansion in the FXN gene, whose first symptoms appeared by the age of 8. At 22 years-old he developed sensorineural deafness, and at 26 visual impairment. Deafness had a progressive course over 11 years, until a stage of extreme severity which hindered communication. Visual acuity had a catastrophic deterioration, with blindness 3 years after visual impairment was first noticed. Audiograms documented progressive sensorineural deafness, most striking for low frequencies. Visual evoked potentials disclosed bilaterally increased P100 latency. He passed away at the age of 41 years old, at a stage of extreme disability, blind and deaf, in addition to the complete phenotype of a patient with Friedreich ataxia of more than 30 years duration. Discussion Severe vision loss and extreme deafness has been described in very few patients with Friedreich ataxia. Long duration, severe disease and large expanded alleles may account for such an extreme phenotype; nonetheless, the role of factors as modifying genes warrants further investigation in this subset of patients.

Insinuate Orbital Cellulitis Associated With Diesel Explosion-Induced Injury

Background: Diesel-related orbital cellulitis is uncommon, it has an insinuate appearance whereas develops aggressively, leading to severe vision loss or poor reconstruction. Here we present a case of diesel explosion-associated eyelid trauma with toxic orbital cellulitis, who at last obtained relatively sound vision and appearance after several rounds of surgeries, which is rarely seen for the trauma itself. Case presentation: A 33-year-old male was injured in the right eye by diesel engine explosion. He was initially treated for right eye eyelid laceration however the trauma developed into toxic orbital cellulitis on the next day. Orbital debridement and removing of the orbital residual diesel fluid was performed on him immediately. However, on the second day necrosis developed in the eyelid and sub-dermal tissue. Therefore he received another orbital debridement to remove the necrotized tissue and awaited the subsequent right eyelid skin grafting surgery. The patient finally got his right eye vision saved as well as maintaining a relatively sound structure of the eyelid.Conclusion: Timely debridement and removing the residual diesel in the orbit is necessary for the recovery of patient with diesel-related toxic orbital cellulitis.