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Relative Genetic and Environmental Contributions to Variations in Human Retinal Electrical Responses Quantified in a Twin Study.
Ophthalmology 2017; 124(8):1175-1185O

Abstract

PURPOSE

To estimate heritability of parameters of human retinal electrophysiology and to explore which parameters change with age.

DESIGN

Prospective, classic twin study.

PARTICIPANTS

Adult monozygotic and dizygotic twin pairs recruited from the TwinsUK cohort.

METHODS

Electroretinogram responses were recorded using conductive fiber electrodes in response to stimuli incorporating standards set by the International Society for the Clinical Electrophysiology of Vision. These parameters were extracted; in addition, photopic negative-response (PhNR; originating from retinal ganglion cells) and i-wave components were extracted from responses to the photopic single flash. Parameter values were averaged from both eyes.

MAIN OUTCOME MEASURES

Mean values were calculated for the cohort. Correlation coefficients with age were calculated (averaging parameters from both twins from each pair). Coefficients of intrapair correlation were calculated for monozygotic and dizygotic twins. Age-adjusted heritability estimates were derived using standard maximum likelihood structural equation twin modeling.

RESULTS

Responses were recorded from 210 participants in total (59 monozygotic and 46 dizygotic twin pairs). Ninety-three percent were women. Mean age for the cohort was 62.4 years (standard deviation, 11.4 years). In general, response amplitudes correlated negatively, and implicit times positively, with age. Correlations were statistically significant (P < 0.05) and moderate or strong (coefficient, >0.35) for the following parameters: scotopic standard and bright-flash a-wave implicit times, photopic 30-Hz flicker and single-flash b-wave implicit times, and PhNR and i-wave implicit times. Intrapair correlations were higher for monozygotic than dizygotic twins, suggesting important genetic influences. Age-adjusted estimates of heritability were significant for all parameters (except scotopic dim-flash b-wave implicit time), ranging from 0.34 to 0.85. Highest estimates were for photopic single-flash a-wave and b-wave amplitudes (0.84 and 0.85, respectively).

CONCLUSIONS

This study explored heritability of retinal electrophysiologic parameters and included measurements reflecting ganglion cell function. Most parameters showed significant heritability, indicating that genetic factors are important, determining up to 85% of the variance in some cone system response parameters. Scotopic responses tended to show lower heritability (possibly relating to greater rod system susceptibility to environmental factors). Future studies can explore the identity of these genetic factors, improving our understanding of how they shape retinal function.

Authors+Show Affiliations

Department of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Department of Twin Research and Genetic Epidemiology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom.Department of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Department of Twin Research and Genetic Epidemiology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom.Department of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Department of Twin Research and Genetic Epidemiology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom.Department of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Department of Twin Research and Genetic Epidemiology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom.Department of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Department of Twin Research and Genetic Epidemiology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom.Department of Ophthalmology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Department of Twin Research and Genetic Epidemiology, King's College London, St. Thomas' Hospital Campus, London, United Kingdom; Retinal Service, Moorfields Eye Hospital, London, United Kingdom; University College London Institute of Ophthalmology, London, United Kingdom; Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, United Kingdom. Electronic address: oarm2@cam.ac.uk.

Pub Type(s)

Journal Article
Twin Study
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

28434717

Citation

Bhatti, Taha, et al. "Relative Genetic and Environmental Contributions to Variations in Human Retinal Electrical Responses Quantified in a Twin Study." Ophthalmology, vol. 124, no. 8, 2017, pp. 1175-1185.
Bhatti T, Tariq A, Shen T, et al. Relative Genetic and Environmental Contributions to Variations in Human Retinal Electrical Responses Quantified in a Twin Study. Ophthalmology. 2017;124(8):1175-1185.
Bhatti, T., Tariq, A., Shen, T., Williams, K. M., Hammond, C. J., & Mahroo, O. A. (2017). Relative Genetic and Environmental Contributions to Variations in Human Retinal Electrical Responses Quantified in a Twin Study. Ophthalmology, 124(8), pp. 1175-1185. doi:10.1016/j.ophtha.2017.03.017.
Bhatti T, et al. Relative Genetic and Environmental Contributions to Variations in Human Retinal Electrical Responses Quantified in a Twin Study. Ophthalmology. 2017;124(8):1175-1185. PubMed PMID: 28434717.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Relative Genetic and Environmental Contributions to Variations in Human Retinal Electrical Responses Quantified in a Twin Study. AU - Bhatti,Taha, AU - Tariq,Ambreen, AU - Shen,Ting, AU - Williams,Katie M, AU - Hammond,Christopher J, AU - Mahroo,Omar A, Y1 - 2017/04/20/ PY - 2016/12/13/received PY - 2017/03/08/revised PY - 2017/03/09/accepted PY - 2017/4/25/pubmed PY - 2017/8/2/medline PY - 2017/4/25/entrez SP - 1175 EP - 1185 JF - Ophthalmology JO - Ophthalmology VL - 124 IS - 8 N2 - PURPOSE: To estimate heritability of parameters of human retinal electrophysiology and to explore which parameters change with age. DESIGN: Prospective, classic twin study. PARTICIPANTS: Adult monozygotic and dizygotic twin pairs recruited from the TwinsUK cohort. METHODS: Electroretinogram responses were recorded using conductive fiber electrodes in response to stimuli incorporating standards set by the International Society for the Clinical Electrophysiology of Vision. These parameters were extracted; in addition, photopic negative-response (PhNR; originating from retinal ganglion cells) and i-wave components were extracted from responses to the photopic single flash. Parameter values were averaged from both eyes. MAIN OUTCOME MEASURES: Mean values were calculated for the cohort. Correlation coefficients with age were calculated (averaging parameters from both twins from each pair). Coefficients of intrapair correlation were calculated for monozygotic and dizygotic twins. Age-adjusted heritability estimates were derived using standard maximum likelihood structural equation twin modeling. RESULTS: Responses were recorded from 210 participants in total (59 monozygotic and 46 dizygotic twin pairs). Ninety-three percent were women. Mean age for the cohort was 62.4 years (standard deviation, 11.4 years). In general, response amplitudes correlated negatively, and implicit times positively, with age. Correlations were statistically significant (P < 0.05) and moderate or strong (coefficient, >0.35) for the following parameters: scotopic standard and bright-flash a-wave implicit times, photopic 30-Hz flicker and single-flash b-wave implicit times, and PhNR and i-wave implicit times. Intrapair correlations were higher for monozygotic than dizygotic twins, suggesting important genetic influences. Age-adjusted estimates of heritability were significant for all parameters (except scotopic dim-flash b-wave implicit time), ranging from 0.34 to 0.85. Highest estimates were for photopic single-flash a-wave and b-wave amplitudes (0.84 and 0.85, respectively). CONCLUSIONS: This study explored heritability of retinal electrophysiologic parameters and included measurements reflecting ganglion cell function. Most parameters showed significant heritability, indicating that genetic factors are important, determining up to 85% of the variance in some cone system response parameters. Scotopic responses tended to show lower heritability (possibly relating to greater rod system susceptibility to environmental factors). Future studies can explore the identity of these genetic factors, improving our understanding of how they shape retinal function. SN - 1549-4713 UR - https://www.unboundmedicine.com/medline/citation/28434717/Relative_Genetic_and_Environmental_Contributions_to_Variations_in_Human_Retinal_Electrical_Responses_Quantified_in_a_Twin_Study_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0161-6420(16)32318-1 DB - PRIME DP - Unbound Medicine ER -