Therapeutic effects of rigid gas permeable contact lenses on refractive errors in keratoconus

Objective To study the therapeutic effects of rigid gas permeable contact lenses(RGPCL) on the treatment of refractory errors in keratoconus. Methods This was a retrospective study. Thirty-two patients(62 eyes) with keratoconus were included. There were 24 males and 8 females,aged from 15 to 38 years old and averaged at 23. 3 years.Subjects were divided into 4 groups according to the severity of keratoconus: phase I group( n = 22),corneal refraction was ≤48. 00 D; phase II group( n = 15),corneal refraction ≤53. 00 D,no corneal scar,and corneal thickness ≥400μm; phase III group( n =13),cornealrefraction 53.00 D,the refractive error of myopia or astigmatism was up to-8.00 ~- 10. 00 D,and the corneal thickness was thinned to 200 ~ 400μm,but no corneal scar; phase IV group( n = 12),corneal refraction was not measureable and there were corneal scars. Except 3 eyes in phase IV groupthat were waiting forelective keratoplasty,other 59 eyes were prescribed with RGPCL,and best corrected visual acuity(BCVA) were compared for spectacles and RGPCL wearing using a paired t-test. The follow-up periods were between 3 and 24 months afterwards.Results(1) BCVA achieved with spectacles in phase I,II,III,and IV groups were 0. 823 ± 0. 182,0. 468 ± 0. 248,0. 289 ± 0. 178,and 0. 151 ± 0. 147,respectively. Accordingly,BCVA achieved with RGPCL were 0. 955 ± 0. 106,0. 933± 0. 123,0. 831 ± 0. 197,and 0. 678 ± 0. 277. Both spectacles and RGPCL BCVA generally deteriorated with the severity of keratoconus. BCVA achieved with RGPCL was significantly better than with spectacles at every disease phase. Paired ttest results in phase I,II,III,and IV were t =- 3. 321,P = 0. 003; t =- 8. 882,P = 0. 000; t =- 7. 408,P = 0. 000;and t =- 8. 262,P = 0. 000. 2) BCVA achieved with RGPCL was significantly better than with spectacles in all 59 eyes as a whole group( t =- 10. 218,P = 0. 000). 3) There were 29 eyes(49. 2%) prescribed with specially designed RGPCL and 30 eyes(50. 8%) prescribed with regular spherical or non-spherical RGPCL. 4) No severe complicationssuch as corneal neovascularization or corneal ulcers were reported. There were 23% mild to moderate corneal staining,which occurred mainly in phase III and IV patients. Conclusion We demonstrated that RGPCL was effective in refractive correction for keratoconus. Early treatment with RGPCL will result in better visual acuity outcomes.