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Abstract
Background Carbonic anhydrase inhibitors (CAIs) are frequently used as an initial step to treat retinitis pigmentosa-associated cystoid macular oedema (RP-CMO). Interestingly, it has been postulated that CAIs might reduce outer nuclear layer (ONL) fluid more effectively than inner nuclear layer (INL) fluid due to better access to retinal pigment epithelium basolateral membrane than neurosensory retina. This retrospective cohort study explores if an association between spatial distribution of cystoid spaces in RP-CMO and CAI response exists.
Methods Two independent graders reviewed pretreatment and post-treatment optical coherence tomography (OCT) images of 25 patients (43 eyes) initiated on topical and/or oral CAIs between January 2013 and December 2014. Documentation included the presence/absence of fluid (and layer(s) involved), external limiting membrane, epiretinal membrane (ERM), vitreomacular adhesion/traction, lamellar/full-thickness macular hole and central macular thickness (CMT)/volume.
Results INL fluid was found in all study eyes. All 13 ‘responders’ (at least 11% reduction of CMT after treatment) demonstrated pretreatment ONL fluid. In seven patients (four responders and three non-responders), complete clearance of ONL fluid was achieved despite persistence of INL fluid. ERM presence was similar in responders and non-responders.
Conclusion In this study, INL fluid was found to be the most common spatial distribution of RP-CMO. However, patients who were classed as a ‘responder’ to CAI treatment all demonstrated coexisting ONL fluid on their pretreatment OCT scans. This may be explained by CAIs having better access to retinal pigment epithelium basolateral membrane than neurosensory retina. Our study also suggests a minimal impact on response to CAIs by ERM.
- carbonic anhydrase inhibitor
- cystoid macular oedema
- imaging
- macular oedema
- optical coherence tomography
- retinal diseases
- retinitis pigmentosa
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Footnotes
Contributors SAS: substantial contributions to the design of the work; acquisition, analysis and interpretation of data for the work; drafting the work; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. NH: substantial contributions to the design of the work; acquisition, analysis and interpretation of data for the work; revising the work critically for important intellectual content; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AQ: substantial contributions to the design of the work; analysis and interpretation of data for the work; drafting the work; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. AK: final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. MM: substantial contributions to the conception and design of the work; acquisition, analysis and interpretation of data for the work; revising the work critically for important intellectual content; final approval of the version to be published; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.
Funding This work was supported by grants from the National Institute for Health Research Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust and UCL Institute of Ophthalmology, Fight For Sight (UK), the Macular Society (UK), Moorfields Eye Hospital Special Trustees, Moorfields Eye Charity, by a multiuser equipment grant from the Wellcome Trust (099173/Z/12/Z), the Foundation Fighting Blindness (FFB; USA), Bayer UK, and Retinitis Pigmentosa Fighting Blindness. MM is a recipient of an FFB Career Development Award.
Competing interests None declared.
Patient consent Not required.
Ethics approval This study was IRB-approved.
Provenance and peer review Not commissioned; externally peer reviewed.
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