[Clinical study on treatment of secondary keratoconus with special designed rigid gas permeable contact lens]

To investigate the clinical effects of special designed rigid gas permeable contact lens (RGPCL) in the treatment of secondary keratoconus.

Retrospective study. The results of correction of secondary keratoconus by the RGPCL in 89 cases (102 eyes) at the Optometry & Ophthalmology Center were analyzed, including history, slit lamp microscope, computer assisted corneal topography, phoropter, corneal endothelial cell examinations and A-scan corneal thickness measurements. We selected and designed the contact lens with different materials for refractive correction according to different corneal deformations. Visual stability and corneal changes were regularly observed. We compared corrected vision, corneal curvature and corneal topography before and after wearing spectacles and RGPCL by using a paired-t test.

Secondary keratoconus after keratorefractive operation in 56 cases (67 eyes), including post-LASIK in 53 eyes, post-PRK in 4 eyes and post-RK in 10 eyes were observed. The cornea thickness in the lesion region was less than 0.4 mm, with nebula or macula. Corneal topography showed different local protrusions, Steep K ranged 47.56 D to 69.72 D, corneal astigmatism ranged 4.00 D to 14.00 D, with irregular deformations, visible different degrees matrix strips pattern changes and Fleischer ring. Secondary keratoconus in 31 cases (31 eyes) was developed after corneal injury. The lesions included opaque scar, decrease of corneal endothelial density, multi-deformations and aphakia in 15 eyes. In addition, there were different degrees of damage in pupil, iris, vitreous and retina. Secondary keratoconus in one case (2 eyes) was developed after anti-glaucoma and pediatric cataract extraction operations (with intraocular lens implantation). Another case was secondary to repeated bilateral keratitis episodes, with large macula, mild thinning of cornea, neovascularization and roughness of corneal surface. The uncorrected visual acuity in these eyes was poor. After wearing the aspherical, Rose K, Piggyback and other special design of RGPCL made by high oxygen permeability materials, visual acuity could be raised to 4.9 or more in 90% cases. Corrected visual acuity remained stable and increased in some cases. Corneal topography showed that the corneal astigmatism, SRI and SAI values were reduced after wearing RGPCL, and the differences were statistically significant (t = 2.389, 2.645, 2.255, P < 0.05).

By using special designed RGPCL in secondary keratoconus after corneal refractive surgery or trauma, satisfactory corrected vision, flattened cornea and regular corneal shapes could be obtained.