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Biomedical subjects

P Yu-Wai-Man

Publications and source records attributed to P Yu-Wai-Man.

7 recordsLinked to original sources
PubMed2005

Surgery for traumatic optic neuropathy.

BACKGROUND: Traumatic optic neuropathy (TON) is an important cause of severe visual loss following blunt or penetrating head trauma. Following the initial insult optic nerve swelling within the optic nerve canal or compression by bone fragments are thought to result in secondary retinal ganglion cell loss. Optic nerve decompression with steroids or surgical interventions or both have therefore been advocated to improve visual prognosis in TON. OBJECTIVES: The aim of this review was to examine the effects and safety of surgical interventions in the management of TON. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (which contains the Cochrane Eyes and Vision Group Trials Register) on The Cochrane Library (Issue 3, 2005), MEDLINE (1966 to August 2005), EMBASE (1980 to 2005 wk 31), NRR 2005 Issue 3, LILACS (September 2004) and the reference lists of other reviews and book chapters on TON. We also contacted researchers in the field. There were no date or language restrictions in the electronic searches for trials. SELECTION CRITERIA: We planned to include only randomised controlled trials of TON in which any form of surgical intervention either on its own or in combination with steroids was compared to steroids alone or no treatment. DATA COLLECTION AND ANALYSIS: Two authors independently assessed the titles and abstracts identified from the search strategy. No studies were found that met our inclusion criteria and therefore none were included for analysis. MAIN RESULTS: No studies were found that met our inclusion criteria. AUTHORS' CONCLUSIONS: The current body of evidence consists mostly of small, retrospective case series. Given the wide range of surgical interventions used in TON it is very difficult to compare these studies, even qualitatively. However, there is a relatively high rate of spontaneous visual recovery and no evidence that surgical decompression of the optic nerve provides any additional benefit. On the other hand surgery carries a definite risk of complications such as postoperative cerebrospinal fluid leak and meningitis. The decision to proceed with surgery in TON therefore remains controversial and each case needs to be assessed on its own merits. Although there is an urgent need for an adequately powered, randomised controlled trial of surgical intervention in TON, this will prove a difficult endeavour.

Humans↗
PubMed2002

The epidemiology of Leber hereditary optic neuropathy in the North East of England.

We performed the first population-based clinical and molecular genetic study of Leber hereditary optic neuropathy (LHON) in a population of 2,173,800 individuals in the North East of England. We identified 16 genealogically unrelated families who harbor one of the three primary mitochondrial DNA (mtDNA) mutations that cause LHON. Two of these families were found to be linked genetically to a common maternal founder. A de novo mtDNA mutation (G3460A) was identified in one family. The minimum point prevalence of visual failure due to LHON within this population was 3.22 per 100,000 (95% CI 2.47-3.97 per 100,000), and the minimum point prevalence for mtDNA LHON mutations was 11.82 per 100,000 (95% CI 10.38-13.27 per 100,000). These results indicate that LHON is not rare but has a population prevalence similar to autosomally inherited neurological disorders. The majority of individuals harbored only mutant mtDNA (homoplasmy), but heteroplasmy was detected in approximately 12% of individuals. Overall, however, approximately 33% of families with LHON had at least one heteroplasmic individual. The high incidence of heteroplasmy in pedigrees with LHON raises the possibility that a closely related maternal relative of an index case may not harbor the mtDNA mutation, highlighting the importance of molecular genetic testing for each maternal family member seeking advice about their risks of visual failure.

Adult↗
PubMed2002

Leber hereditary optic neuropathy.

Leber hereditary optic neuropathy (LHON) is a mitochondrial genetic disease that preferentially causes blindness in young adult males, affecting about 1 in 25 000 of the British population. It is characterised by bilateral subacute loss of central vision owing to focal degeneration of the retinal ganglion cell layer and optic nerve. Over 95% of LHON cases are primarily the result of one of three mitochondrial DNA (mtDNA) point mutations, G3460A, G11778A, and T14484C, which all involve genes encoding complex I subunits of the respiratory chain. An intriguing feature of LHON is that only approximately 50% of males and approximately 10% of females who harbour a pathogenic mtDNA mutation actually develop the optic neuropathy. This marked incomplete penetrance and gender bias imply that additional mitochondrial and/or nuclear genetic factors must be modulating the phenotypic expression of LHON. It is also likely that environmental factors contribute to the onset of visual failure. However, these secondary precipitating factors remain poorly defined at present. In this review, we describe the natural history of this optic nerve disorder and highlight issues relating to clinical diagnosis, management, and genetic counselling. We also discuss the findings of recently published studies and the light they shed on the complex aetiology and pathophysiology of LHON.

DNA, Mitochondrial↗