The effect of long-term use of soft contact lens on corneal epithelium, corneal volume, corneal endothelial cell properties and corneal biomechanics

PURPOSE: To evaluate the effect of the use of contact lenses on corneal morphology, endothelial cell layer and biomechanics MATERIAL-METHOD: In this study, 100 eyes of 50 patients who used soft contact lenses regularly and controlled in Manisa Celal Bayar University Faculty of Medicine Department of Ophthalmology, were compared with age and refractory matched control group. All patients underwent a detailed ophthalmologic examination. Lens and solution brands and duration of use were recorded in contact lens group. In all cases, refraction measurement with Canon RK-F2 autorefractometer, noncontact specular microscopy, Scheimpflug camera, anterior segment optical coherence tomography and external corneal lens epithelial thickness map measurement, ocular response analyzer and biomechanical evaluation were performed. Corneal features of all patients were evaluated with Canon RK-F2 (Tokyo-Japan) autorefractometer, noncontact specular microscopy (Konan CellChek XL, Medical USA, Torrance, CA, USA), Scheimpflug camera (Pentacam, Oculus Optikgerate GmbH, Wetzlar, Germany), anterior segment optical coherence tomography (Carl Zeiss Meditec, Inc. Dublin, CA) and ocular response analyzer (Reichert Ophthalmic Instruments, Depew, New York, USA). All parameters were compared statistically between groups and p <0.05 values were considered significant. RESULTS: In the contact lens group; There were 27 males (54%) and 23 females (46%) and the mean age of the patients was 24.54 ± 3.06 years. In control group; There were 25 males (50%) and 25 females (50%) and the mean age of the subjects was 23.38 ± 2.33 years. There was no significant difference between contact lens group and control group in age and gender (respectively p=0.24 p=0.44). The mean duration of contact lens use was 5.94 ± 3.08 (1-12) years. The refraction values of the groups were respectively -3.30 ± 1.57 D (-1.0 , -9.0), -3.31 ± 1.72D (-1.0 , -8.50) (p = 0.36). Among contact lens users, 15 (30%) had Balafilcon A (PureVision™ Bausch & Lomb, Rochester, NY, USA), 13 (26%) had Lotrafilcon B(Air Optix® AQUA, Ciba Vision, Duluth, GA, USA) and 22 (44%) had Senofilcon A(Acuvue Oasys, Johnson & Johnson, Jacksonville, FL).The mean r1 value 7.86 ± 0.23 mm, r2 value 7.67 ± 0.25 mm, anterior chamber depth 3.14 ± 0.25 mm, corneal volume 60.68 ± 3.28 mm3, anterior chamber volume 210 ± 33.96mm3 and CCT 531 ± 27.18 µm were measured in contact lens group. The mean r1 value 7.93 ± 0.22 mm, r2 value 7.75 ± 0.23 mm, anterior chamber depth 3.18 ± 0.29mm, corneal volume 59.85 ± 4.64mm3, anterior chamber volume 208 ± 31,28mm3 and CCT 546 ± 31,49 µm were measured in control group. (p=0.02, p=0.02, p=0.14, p=0.21, p=0.16, p=0.001) The mean CD: 2925 ± 164.32 cells/mm2, CV: % 28.56 ± 3.09, HEX: % 49.33 ± 6.41 were measured in contact lens group and the mean CD: 2887 ± 187.92 cells/mm2, CV: % 28.31 ± 3.61, HEX: % 49.77 ± 7.46 were measured in control group (respectively p=0.13,p=0,60,p=0,65). The mean GİBcc: 16.57 ± 2.65 mmHg, GİBg: 15.63 ± 2.61 mmHg, CRH: 10.04 ± 1.83 mmHg, CH: 9.97 ±1.88 mmHg were measured with ORA in contact lens group and the mean GİBcc: 15.86 ± 2.80mmHg, GİBg: 15.66 ± 3.03 mmHg, CRH: 10.70 ± 2.0 mmHg, CH: 10.66 ±1.83 mmHg were measured in control group (respectively p=0,68, p=0,94, p=0,01, p=0,01). Epithelial thickness in contact lens and control group was 47.31 ± 3.51 µm, 48.64 ± 4.09 µm in the central quadrant, 46.56 ± 3.67 µm, 47.83 ± 3.96 in nasal quadrant of paracentral region and 45.44 ± 3.72 µm, 46.75 ± 4.21 µm in temporal quadrant of paracentral quadrant, respectively (respectively p=0.01, p=0.02, p=0.02). CONCLUSION: Amongst the eyes have same amount of refractive error, when the contact lens wearers compared to non-wearers, they have thinner CCT, flatter anterior curvature of cornea, lower CH and CRH values lower and thinner epithelial thickness in the central quadrant and nasal and temporal quadrant of paracentral region . No significant difference was found between the two groups in terms of CD, CV and HEX. Furthermore, if the effects of hypoxia on corneal morphology are considered, the use of contact lens with high Dk / t ratio is extremely important for preventing hypoxia. Key words: contact lens, corneal endothelium, corneal biomechanics, corneal epithelial thickness