First Author: B.Can Ermerak TURKEY
Co Author(s): O. Yalcinbayir C. Erseven E. Eren E. Sobu A. Yucel
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Diabetic retinopathy (DR) is a leading cause of visual impairment that requires lifelong control and monitoring. Recent studies suggest that retinal damage is accompanied by vascular changes of choroid throughout the disease course. The choroid is responsible for nutrition and oxygenation for outer layers of retina and avascular fovea; therefore choroidal alterations may induce retinal vulnerability against hypoxia. We designed our study in paediatric Type 1 Diabetes Mellitus (T1DM) patients without visible signs of DR, for evaluating macular and peripapillary choroidal thickness (CT) using enhanced depth imagining optical coherence tomography (EDI-OCT) therefore to define the early stage choroidal changes.
This prospective and cross-sectional study was conducted at the Uludag University, Department of Ophthalmology. Local ethics committee approval was obtained and the study adhered to the tenets of the Declaration of Helsinki.
Two hundred and six eyes of 103 paediatric T1DM patients without diabetic retinopathy and 88 eyes of 44 age-matched healthy controls were enrolled. The exclusion criteria were; concurrent ocular disease, previous ocular surgery, systemic disease except for T1DM, refractive errors higher than ± 3.50 diopters. Each participant underwent a complete ophthalmic examination and spectral domain optical coherence tomography (SD-OCT) evaluation on Heidelberg Spectralis (Heidelberg Engineering,Heidelberg, Germany). Age, gender, refractive error, best corrected visual acuity (BCVA), intraocular pressure (IOP), axial length (AL), disease duration and serum glycosylated haemoglobin (HbA1c) were noted for each participant. Choroidal thickness measurements were performed manually using provided software; the distance between retina pigment epithelium and choroid-sclera interface was taken into account. Posterior pole CT measurements consisted of three points; subfoveal, 1500 µm nasal and 1500 µm temporal intervals from the fovea. Peripapillary scan was performed by the standard protocol for retinal nerve fibre layer (RNFL) assessment (using a 360 degrees 3,4-mm diameter circle centreed at the optic disc) and CT was measured at eight sectors (superior, superonasal, nasal, inferonasal, inferior, inferotemporal, temporal, superotemporal) along the scan. Central macular thickness (CMT), overall and the same eight sector peripapillary RNFL thickness values were also recorded for each participant.
Mean age of patients with T1DM (the study group) was 13.09±2.93 (range 7-18) years; mean age of controls was 13.45±3.94 (range 8-18) years. There was no significant difference among two groups in terms of age (p=0.364), IOP (p=0.072 ), and AL (p=0.081). At the study group, the mean duration of T1DM was 5.17±3.07 (range 1-14) years, and the mean HbA1c was %9.57±1.98 (range 5.6-14.8). Choroidal thickness measurement values of subfoveal, nasal and temporal macula were thinner in the study group but no statistical significance was found (p=0.835, p=0.305, p=0.054). Peripapillary choroidal thickness measurements of eight sectors were also thinner in the study group; however superonasal, nasal, inferonasal and inferior sector values were significantly different (p=0.010, p=0.020, p=0.019, p=0.018). We did not detect any statistical significance between groups in terms of average CMT (p=0.742). Even though overall and eight sector RNFL thickness measurements were thinner in the study group; only temporal sector value showed statistical significance (p=0.032). With regard to the correlation analysis that was performed; CT measurements were not associated with HbA1c levels or duration of disease. Also, no correlation was found between peripapillary CT values and RNFL values at the same sectors.
As a result, our study showed subfoveal, nasal and temporal macular choroidal thickness values are thinner in diabetic eyes without visible signs of DR compare to control group. Nevertheles, we couldn’t detect any significancy. In terms of peripapillary CT; superonasal, nasal, inferonasal and inferior sectors were significantly thinner in the study group. A number of studies demonstrated different results on choroidal thickness changes in diabetic patients, yet the relationship with diabetic retinopathy is not clearly identified. To our knowledge, this is the first research to describe peripapillary and posterior pole CT changes (except than subfoveal) in children with T1DM and no DR. We believe, choroidal thickness may be an early indicator for diabetic retinal disease; however further prospective and longitudinal studies in larger patient groups with later stages of retinopathy are needed.