Date Posted: 10 September 2009
A US study led by the Scheie Eye Institute in Pennsylvania has identified regions of normal and damaged retinal architecture in a cohort of USH1B (Usher syndrome type 1B) patients with MYO7A mutations. The finding may have implications for the design and evaluation of new treatment approaches such as sub-retinal gene therapy. Focusing initial treatments on regions of both obvious and progressing damage presents a higher chance of slowing or halting the pathology. In addition, the use of OCT (optical coherence tomography) technology should prove useful in defining the safety and efficacy of any proposed experimental treatments.
USH1B is thought to be one of the most severe forms of "Usher's syndrome", the term given to a group of heterogeneous autosomal recessive disorders leading to loss of both hearing and vision. While gene therapy may represent a potential therapeutic approach the field has suffered from the absence of a good animal model to approximate the human phenotype. However, recent advances in (OCT) have allowed for real time imaging of the detailed retinal architecture in patients with USH1B.
A study on such patients, led by Prof. Samuel Jacobson at the Scheie Eye Institute, has shown that large regions of the retina can be normal in structure and function. These normal regions reside adjacent to identifiable "transition zones" which then lead into severely abnormal retinal architecture. Such a finding was not expected based on full-field ERG studies which had traditionally indicated a retina-wide pathology. If sub-retinal gene therapy in such a disorder is to be optimised, treatment focused on specific transition zones in the retina should provide valuable guidance in conducting sub-retinal injections. Subsequent evaluation of a given therapeutic approach may be facilitated by comparing injected to non-injected sites that show similar baseline properties) before and after treatment. [Jacobson et al., IOVS, 2009, Vol. 50, No.4, 1886-1894].
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