Influence Of Riboflavin/UVA Corneal Collagen Crosslinking On Corneal Endothelial Cells

Purpose:Riboflavin/UVA corneal collagen crosslinking is gradually becoming widely adopted in the clinical management of keratoconus as an effective treatment to control the development of keratoconus.The UVA used might have an adverse impact on the corneal endothelium.A 400um-depth can assure that the energetic density of UVA achieving endothelium is not enough to derive the endothelial cells in standard CXL.For advanced keraconic patients with thin corneas less than 400um,hypotonic riboflavin CXL is adopted to flatten the cornea to be thicker than the threshold before UVA irradiation and guarantee safety of the treatment process.Corneal endothelium is an important selective barrier for the cornea.The integrity of endothelial structure and function is the physical base of corneal clarity.Furthermore,endothelial cells cannot regernerate,and can only supplement the defective area by enlarging itself and migration.Thus,we designed this research to study the influence of riboflavin/UVA corneal collagen crosslinking on corneal endothelial cells by comparing the changes of endothelial cells after isotonic and hypotonic collagen crosslinking treatment.Methods:Selected 49 keratoconic eyes,32 patients,who accepted riboflavin/UVA corneal collagen crosslinking in our hospital from 2014 to 2015.The patients were divided into 2 groups according to the corneal central thickness:normal cornea group(>400um)and thin cornea group(<400um).After full preoperative preparation and well anesthetization,the central corneal epithelium was removed,Then administration of riboflavin solution(0.1%isotonic riboflavin solution for normal cornea group,and 0.1%hypotonic riboflavin solution for thin cornea group)is conducted every 3 minutes for 30 minutes.Slit-lamp and OCT examination were operated to guarantee that the full-thickness cornea and the anterior chamber was yellow flared and the CCT no less than 400um.Irradition was conduct on the cornea by UVA with a wavelength of 370nm and irradiation energy density of 3mW/cm2,at 5cm Irradiation distance.The total irradiation time lasted for 30 minutes.During the operation,the administration of riboflavin solution was continued every 3 minutes.Patients were asked to wear a soft contact lens after treatment,eye drops were also applied.The visual acuity(BCVA,UCVA),Kmax,CCT,ECC,CV and Hex were evaluated preoperatively and followed up at 3,6 monthsand 1 year intervals.Kmax value was acquired by waveLight oculyzer and CCT by OCT anterior segment examination.And statistics analysis with all kinds of above indices,comparing preoperative results and postoperative changes between 2 groups.Results:(1)Between 49 selected keratonic eyes that had received CXL treatment,18 eyes undergone hypotonic CXL(preoperative CCT<400 um),while the left 31 ones undergone isotonic CXL(400 um<preoperative CCT).(2)The average ECC of normal cornea group eyes was 3047.38±341.71/mm2 and that 1 year after treatment was 2924.03±474.08/mm2.The result has no significant statistically difference;The average ECC of thin cornea group eyes was 3056.53±387.26/mm2 and that 1 year after treatment was 2967.34±389.53/mm2.The result has no statistically difference.(3)The average CV of normal cornea group eyes was 36.76±4.95%and that 1 year after treatment was 35.56±5.30%.The result has no significant statistically difference;The average CV of thin cornea group eyes was 35.26±6.18%and that 1 year after treatment was 36.31±5.52%.The result has no significant statistically difference.(4)The average Hex%of normal cornea group eyes was 51.17±3.32%and that 1 year after treatment was 50.39±2.72%.The result has no significant statistically difference;The average Hex%of thin cornea group eyes was 58.90±3.08%and that 1 year after treatment was 55.61±3.05%.The result has no significant statistically difference.(6)The BCVA,UCVA and Kmax had statistically significant improvement after CXL treatment.Conclusions:Corneal collagen crosslinking with both isotonic and hypotonic riboflavin solution don’t have adverse effects on corneal endothelial cells.No significant changes in corneal endothelial cell shape or number were observed after CXL treatment.This suggests that CXL is a treatment of good validity and safety for keratoconus.