The ophthalmic experience: unanticipated primary findings in the era of next generation sequencing

Endophthalmitis: Microbiology and Organism Identification Using Current and Emerging Techniques

Endophthalmitis is an ophthalmological emergency requiring timely and appropriate diagnosis and treatment. Microbiological methods of microscopy (Gram's staining) and culture are the current gold standard for organism identification. However, a significant proportion of endophthalmitis remains culture-negative-perhaps the inflammation is non-infectious in origin, results from a novel organism are unidentifiable or because the causative organism is non-culturable often due to pre-treatment with antibiotics. This review outlines the microbiological profile of endophthalmitis, current clinically used methods for organism identification, and the newer molecular techniques of polymerase chain reaction (PCR) and next-generation sequencing (NGS) technology as diagnostic tools for endophthalmitis. They offer the potential to improve organism identification rates and clinical outcomes in infectious diseases, representing an exciting future direction for organism identification in endophthalmitis. Based on the largest ophthalmic hospital in Australia, we highlight the key practical challenges faced by Australian diagnostic laboratories for their use in a clinical setting.

Inherited retinal disorders: a genotype-phenotype correlation in an Indian cohort and the importance of genetic testing and genetic counselling

PURPOSE

Recent advances in sequencing technologies have enabled radical and rapid progress in the genetic diagnosis of inherited retinal disorders (IRDs). Although the list of gene variations continues to grow, it lacks the genetic etiology of ethnic groups like South Asians. Differences in racial backgrounds and consanguinity add to genetic heterogeneity and phenotypic overlaps.

METHODS

This retrospective study includes documented data from the Gen-Eye clinic from years 2014 to 2019. Medical records and pedigrees of 591 IRD patients of Indian origin and genetic reports of 117 probands were reviewed. Genotype-phenotype correlations were performed to classify as correlating, non-correlating and unsolved cases.

RESULTS

Among the 591 patients, we observed a higher prevalence of clinically diagnosed retinitis pigmentosa (38.9%) followed by unspecified diagnoses (28.5%). Consanguinity was reported to be high (55.6%) in this cohort. Among the variants identified in 117 probands, 36.4% of variants were pathogenic, 19.2% were likely pathogenic, and 44.4% were of uncertain significance. Among the pathogenic and likely pathogenic variants, autosomal recessive inheritance showed higher prevalence. About 35% (41/117) of cases showed genotype-phenotype correlation. Within the correlating cases, retinitis pigmentosa and Stargardt disease were predominant. Novel variants identified in RP, Stargardt, and LCA are reported here.

CONCLUSION

This first-of-a-kind report on an Indian cohort contributes to existing knowledge and expansion of variant databases, presenting relevant and plausible novel variants. Phenotypic overlap and variability lead to a differential diagnosis and hence a clear genotype-phenotype correlation helps in precise clinical confirmation. The study also emphasizes the importance of genetic counselling and testing for personalized vision care in a tertiary eye hospital.

Genotype-Phenotype Analysis of RPGR Variations: Reporting of 62 Chinese Families and a Literature Review

Purpose

RPGR is the most common cause of X-linked retinitis pigmentosa (RP), of which female carriers are also frequently affected. The aim of the current study was to explore the RPGR variation spectrum and associated phenotype based on the data from our lab and previous studies.

Methods

Variants in RPGR were selected from exome sequencing data of 7,092 probands with different eye conditions. The probands and their available family members underwent comprehensive ocular examinations. Similar data were collected from previous reports through searches in PubMed, Web of Science, and Google Scholar. Systematic analyses of genotypes, phenotypes and their correlations were performed.

Results

A total of 46 likely pathogenic variants, including nine missense and one in-frame variants in RCC1-like domain and 36 truncation variants, in RPGR were detected in 62 unrelated families in our in-house cohort. In addition, a total of 585 variants, including 491 (83.9%) truncation variants, were identified from the literature. Systematic analysis of variants from our in-house dataset, literature, and gnomAD suggested that most of the pathogenic variants of RPGR were truncation variants while pathogenic missense and in-frame variants were enriched in the RCC1-like domain. Phenotypic variations were present between males and female carriers, including more severe refractive error but better best corrected visual acuity (BCVA) in female carriers than those in males. The male patients showed a significant reduction of BCVA with increase of age and males with exon1-14 variants presented a better BCVA than those with ORF15 variants. For female carriers, the BCVA also showed significant reduction with increase of age, but BCVA in females with exon1-14 variants was not significant difference compared with those with ORF15 variants.

Conclusion

Most pathogenic variants of RPGR are truncations. Missense and in-frame variants located outside of the RCC1-like domain might be benign and the pathogenicity criteria for these variants should be considered with greater caution. The BCVA and refractive error are different between males and female carriers. Increase of age and location of variants in ORF15 contribute to the reduction of BCVA in males. These results are valuable for understanding genotypes and phenotypes of RPGR.