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RCOphth Annual Congress 2026
18 - 21 May, 2026 | Manchester Central, Manchester
P208
Visual acuities and refractions in patients with PDE6C-associated achromatopsia
Poster Presenter
Part of Topic
Medical retina
Visual acuities and refractions in patients with PDE6C-associated achromatopsia
Background
•PDE6C encodes a subunit of the photoreceptor phosphodiesterase integral to cone phototransduction.
•Biallelic pathogenic variants cause cone dysfunction/achromatopsia.1,2
•Variants in this gene are a rarer cause of achromatopsia in the UK, compared with CNGA3 and CNGB3.3,4
•Here, we explored visual acuities and refractions in patients with molecularly confirmed disease.
Methods
•The database of a large inherited retinal disease service was retrospectively reviewed to identify patients with PDE6C-associated achromatopsia.
•Best recorded visual acuities from each clinical visit were analysed.
•Snellen visual acuities were converted to logMAR equivalents.
•Where refractive data was available, spherical equivalents were calculated for each patient.
Results
•Fourteen patients (10 females) from 13 families were identified.
Acuities at first visit
•Mean (SD) age at first visit was 26.1 (14.4) years (median 27.1; range 1.5 to 44.7).
•Mean (SD) acuity: 0.86 (0.27) for right eyes (median 0.95); 0.86 (0.29) for left eyes (median 1.00)
Acuities over time
•Follow up for more than 1 year was available for 13 patients
•Mean (SD) follow up, 10.1 (6.9) years; median 8.3 years.
•Mean (SD) ages at first and last visit: 25.3 (14.7) and 35.9 (18.9) yearsrespectively.
At 1st visit, mean (SD) acuities were 0.86 (0.28) right and 0.84 (0.30) left.
At last visit, mean (SD) acuities were 0.90 (0.15) right and 0.91 (0.14) left.
Refractions
•Refractions were available for 11 patients (Figure 1).
•Mean (SD) age was 34.1 (20.1) years (median 37.8; range 2.6 to 58.8 years).
•Right eyes: mean (SD) refraction: –5.82 (5.24) D (median –5.00; range–13.88 to +1.13)
•Left eyes: mean (SD) refraction: –5.30 (5.69) D (median -2.00; range –14.88 to +0.75)
•Five patients (45%) had more than 6 dioptres of myopia in both eyes.
Conclusions
•High myopia was present in nearly half of patients, contrasting with other genetic causes of achromatopsia.
•Understanding which cone dysfunction syndromes predispose to significant refractive error may yield insight into mechanisms underlying myopia development.
•These data can help inform prognostic discussions and the design of future therapeutic trials.
References
1.Thiadens et al. Am J Hum Genet. 2009 Aug;85(2):240-7.
2.Wong & Mahroo. Clin Exp Ophthalmol. 2025 Apr;53(3):260-280.
3.Pontikos et al. Ophthalmology. 2020 Oct;127(10):1384-1394.
4.Lin et al. Ophthalmol Retina. 2024 Jul;8(7):699-709.
Acknowledgements: Wellcome Trust, Medical Research Council, NIHR Biomedical Research Centre at Moorfields Eye Hospital and the UCL Institute of Ophthalmology. Views expressed are those of the authors and not the funding organisations.