Evaluation of visual impairment in Usher syndrome 1b and Usher syndrome 2a.
OBJECTIVE
To evaluate visual impairment in Usher syndrome 1b (USH1b) and Usher syndrome 2a (USH2a).


METHODS
We carried out a retrospective study of 19 USH1b patients and 40 USH2a patients. Cross-sectional regression analyses of the functional acuity score (FAS), functional field score (FFS) and functional vision score (FVS) related to age were performed. Statistical tests relating to regression lines and Student's t-test were used to compare between (sub)groups of patients. Parts of the available individual longitudinal data were used to obtain individual estimates of progressive deterioration and compare these to those obtained with cross-sectional analysis. Results were compared between subgroups of USH2a patients pertaining to combinations of different types of mutations.


RESULTS
Cross-sectional analyses revealed significant deterioration of the FAS (0.7% per year), FFS (1.0% per year) and FVS (1.5% per year) with advancing age in both patient groups, without a significant difference between the USH1b and USH2a patients. Individual estimates of the deterioration rates were substantially and significantly higher than the cross-sectional estimates in some USH2a cases, including values of about 5% per year (or even higher) for the FAS (age 35-50 years), 3-4% per year for the FFS and 4-5% per year for the FVS (age > 20 years). There was no difference in functional vision score behaviour detected between subgroups of patients pertaining to different biallelic combinations of specific types of mutations.


CONCLUSIONS
The FAS, FFS and FVS deteriorated significantly by 0.7-1.5% per year according to cross-sectional linear regression analysis in both USH1b and USH2a patients. Higher deterioration rates (3-5% per year) in any of these scores were attained, according to longitudinal data collected from individual USH2a patients. Score behaviour was similar across the patient groups and across different biallelic combinations of various types of mutations. However, more elaborate studies, preferably covering longitudinal data, are needed to obtain conclusive evidence.
Pennings
Ronald J E
RJ
Department of Ophthalmology, University Medical Centre St Radboud, Nijmegen, The Netherlands.
Huygen
Patrick L M
PL
Orten
Dana J
DJ
Wagenaar
Mariette
M
van Aarem
Annelies
A
Kremer
Hannie
H
Kimberling
William J
WJ
Cremers
Cor W R J
CW
Deutman
August F
AF
D000293:Adolescent; D000328:Adult; D003430:Cross-Sectional Studies; D004398:Dyneins; D016326:Extracellular Matrix Proteins / Q000235:genetics; D005838:Genotype; D006319:Hearing Loss, Sensorineural / Q000235:genetics / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D000081412:Myosin VIIa; D009218:Myosins / Q000235:genetics; D010641:Phenotype; D012174:Retinitis Pigmentosa / Q000235:genetics / Q000503:physiopathology*; D012189:Retrospective Studies; D013577:Syndrome; D014786:Vision Disorders / Q000235:genetics / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology; D014794:Visual Fields / Q000502:physiology; D019987:Persons with Visual Disabilities
D016326:Extracellular Matrix Proteins; C000631455:MYO7A protein, human; D000081412:Myosin VIIa; C112735:USH2A protein, human; D009218:Myosins; D004398:Dyneins