Analysis Of Visual Performance Corrected By RGPCL In Keratoconus And Long-Term Observation

Background:Keratoconus is a progressive noninflammatory disease of the central cornea which causes central stromal thinning, apical protrusion, and irregular astigmatism. Etiology of this disease is not clear. Keratoconus may be more devastating than was previously thought because its impact is on people who are younger. Its impact on vision-related quality of life even cause a number of characteristics of increased anxiety and reactivity to stressful situations.The irregular astigmatism created by ectasia of the central cornea can be sufficiently corrected with rigid gas permeable (RGP) contact lenses, and RGP CL have become the the best choice of non-surgical treatment. But visual acuity does not fully reflect the visual quality. Contrast sensitivity and wavefront aberration are more sensitive indicators to reflect the visual quality.This reasch aim to analyze comprehensively the visual quality of keratoconus corrected by RGPCL compared with myopic patients and to search the factors that affect the visual quality. Another aim is to search the control effect of RGPCL for keratoconus after long-term wearing. Part one:Analysis of visual performance corrected by RGPCL in keratoconusObjective:To analysis the visual performance in keratoconus with rigid gas permeable contact lens (RGPCL).Methods:75 eyes of 45 keratoconic patients who were fitted with RGP CL(KC-RGP group) were enrolled. According to the SimKmax value, the keratoconus were divided into two groups:mild keratoconus group and the moderate to severe keratoconus group. Sim Kmax> 47D as mild keratoconus (30 eyes) and Sim Kmax> 55.0D as moderate to severe keratoconus (45eyes).Visual acuity(VA) and contrast sensitivity (CS) were examined to evaluate the visual performance(VP). Corneal astigmatism and wavefront error were measured to analyze the influential factors for visual quality.54 eyes of 27 myopic patients with RGP CL were as control group.Results:All keratoconic eyes got corrected VA of 0.6 or better.66.67% of them reached 1.0. The VA of all mild keratoconus group got 1.0. The RGPCL reduced SimKmax and corneal astigmatism from 55.23±4.52 D to 46.12±3.66D and 6.25±3.68D to 1.25±0.65D respctively in KC-RGP group. Meanwhile, in the myopia group,the corneal astigmatism was reduced from 1.28±0.34D to 0.42±0.09D. There was no difference between three groups in low frequency of CS (P>0.01).But in the middle frequency of light off CS and the high frequency of CS,the KC-RGP group was significantly lower than myopia group(P<0.01).But there was no significant difference between two KC-RGP group. The root-mean-square (RMS)of total higher-order aberrations (HOAs),coma-like aberration and spherical-like aberrations in the KC-RGP group were significantly higher than that of myopia group(P<0.01).Conclusion:The visual performance in keratoconic eyes with RGPCL degrades compared with myopic eyes with RGPCL, even if the corrected VA is good. The degradation is assumed to be related to residual corneal astigmatism and HOAs in keratoconic eyes with a RGPCL. Part two:Long-term observation of RGPCL treatment for different degrees of keratoconusObjective:To investigate the long-term effects of rigid gas permeable contact lens (RGPCL)for different degrees of keratoconus.Methods:45 cases of primary keratoconus (75 eyes) wearing RGP CL were enrolled. According to the SimKmax value, the keratoconus were divided into two groups:mild keratoconus group and the moderate to severe keratoconus group. Sim Kmax> 47D as mild keratoconus (30 eyes) and Sim Kmax> 55.OD as moderate to severe keratoconus (45eyes).The follow-up time was 1 to 3 years, average of 1.5 years. Followed up included visual acuity, slit lamp examination, OrbscanⅡexamination.The Sim Kmax, astigmatic index, Diff values and the thinnest corneal thickness were recorded.Results:The visual acuity(VA)of mild keratoconus patients reached 1.0 during the followed-up.At the early stage,44.44%(20/45) of moderate to severe keratoconus have the VA of 1.0,but at the end of stage, only 22.22%(10/45) of the patients wearing RGPCL can reach 1.0.5 patients in mild group replaced lenses because of the development of the cone during follow-up. In the moderate to severe keratoconus group,15 patients (33.33%)gave up the original lenses,10 cases of them changed new lenses,5 cases received deep lamellar keratoplasty or penetrating keratoplasty due to corneal scarring and acute cone.The Sim Kmax, astigmatic index, Diff values had increasing trend in both group during the observation process. At 6 months,The Sim Kmax, astigmatic index, the Diff values of anterior corneal surface had no significant difference compared with beginning, but statistically significant difference was founded at 12 months. The Diff values of posterior corneal surface in mild keratoconus group were significantly increased at 12 months compared with begining,and in severe keratoconus group the change occurred in 6 months.The thinnest corneal thickness had slow downward trend in both groups, but decreased more obvious in severe group. Conclusion:Keratoconus can obtain long-term good visual acuity by RGPCL wearing, especially for mild keratoconus. Mild keratoconus can get better control than moderate to severe ones through long-term RGPCL wearing.