131 CENTRAL CORNEAL THICKNESS AND ITS CORRELATION WITH THE SEVERITY OF DIABETIC RETINOPATHY AND HBA1C LEVELS IN DIABETES MELLITUS

Erum Waris Khateeb, *Mustafeez Zehra and Imtiyaz Ahmed

ABSTRACT

Background: Diabetic retinopathy (DR) is one of the most common causes of preventable blindness in the world. Chronic metabolic stress caused by hyperglycaemia has shown to affect corneal endothelial cells. Central corneal thickness (CCT) is an important indicator of functioning of corneal endothelial pump. It is key parameter for estimation of IOP and in refractive surgeries. Its role in diabetic patients thus needs to be researched upon. Materials & Methods: A cross-sectional observational study was conducted between May 2021 to Feb 2022 at the post-graduate department of Ophthalmology, SKIMS Medical college and Hospital after giving clearance by ethical committee of the institute. 100 subjects with type 2 diabetes mellitus & 100 age and sex matched controls were enrolled in the study. The study group was divided into 5 sub-groups according to Early Treatment Diabetic Retinopathy Study (ETDRS) classification. Eyes of subjects with prior history of ocular surface disease, corneal degeneration or dystrophy, ocular surgery, glaucoma, uveitis, on chronic topical medication or contact lens use were excluded. CCT was measured using SD-OCT (Zeiss Cirrus HD-OCT). Fasting blood sugar and HbA1c levels were done in all subjects of the study group. Results: Average CCT among the study group was 562±21μm and among the control group was 524±22μm. The mean CCT for patients with no diabetic retinopathy was 527.75±7.22. Mean CCT for patients with very mild & mild NPDR was 541.11±7.91, with moderate NPDR was 563.23±8.02, with severe and very severe NPDR was 583.66±7.65 and that with Proliferative diabetic retinopathy was 609.03±16.12 μm. The correlation was significant (p=0.001). Also mean CCT in patients with HbA1c levels between 4-5.6% was 535.64±12.86, in patients with HbA1c levels between 5.61-6.5% was 550.89±13.93 and those with HbA1c levels >6.5% mean CCT was 584.63±20.21μm. The correlation was statistically significant(p=0.01). Conclusion: This study demonstrates a strong positive correlation between CCT to the severity of DR and HbA1c levels. The corneas of Type 2 diabetics were significantly thicker, indicating that thick corneas are more likely to be found in advanced stage of the disease. Routine assessment of CCT in type 2 diabetic patients along with usual retinopathy assessment should be done. It should be a part of the pre-operative assessment undergoing intra-ocular surgeries like refractive surgery and keratoplasty.

Keywords: Central corneal thickness, Diabetes Mellitus, HbA1c levels, Diabetic retinopathy.