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Frederick T Collison, Gerald A. Fishman; Structural and functional monitoring of extramacular cystoid spaces in X-linked retinoschisis treated with carbonic anhydrase inhibitors. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):3833. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of carbonic anydrase inhibitors (CAI) on extramacular cystoid spaces in patients with X-linked retinoschisis (XLRS) by performing structural and functional testing.
Baseline extramacular microperimetry (MP) was obtained on four XLRS patients (P1-P4, age range 18-44 years) who exhibited cystoid spaces beyond the macula on spectral-domain optical coherence tomography (SD-OCT). Eight visually normal subjects (age range 24-38 years) were tested with MP in one eye. Both MP and SD-OCT were performed on an Optos Spectral OCT/SLO microperimeter (Optos, Scotland, UK). All four patients were treated with a topical CAI and were re-tested with SD-OCT at follow-up. Follow-up MP was performed if a reduction in retinal thickness was observed. A fifth XLRS patient (P5, age 55) with extensive extramacular cystoid splitting was treated with oral extended-release acetazolamide 500 mg/day and underwent full-field ERG testing at both baseline and follow-up.<br />
Baseline extramacular mean thresholds for P1-P4 averaged 14.2 dB (SD 4.1), whereas normal subjects’ extramacular mean thresholds averaged 14.1 dB (SD 2.2). Two patients (P1 and P2) failed to respond with thickness reduction on SD-OCT. Considering three eyes of two responders (P3 and P4), focal retinal thickness was reduced at follow-up by at least 10 microns (mean 52.4 microns) at all 49 locations where cystoid spaces were visible on SD-OCT at baseline, with at least an 11% reduction at all but three points. The mean MP threshold change at those 49 points was -0.5 dB, with improvements of 2 dB or more at 17 points, and losses of 2 dB or more at 23 points. Although P5 exhibited a resolution of cystoid spaces throughout his retina, his dark-adapted single flash full-field ERG was distinctly electronegative at both baseline and follow-up.
To our knowledge, this is the first reported study of follow-up MP and ERG testing in CAI treatment responders with XLRS. MP thresholds of points overlying extramacular cystoid spaces were within the normal range at baseline. While we could not demonstrate functional improvement, three cases did demonstrate an anatomical reduction of extramacular cystoid spaces. These findings add to a published single case report in which we first noted that extramacular cystoid spaces observed in XLRS may respond to CAI treatment. <br />
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