The challenge of fitting astigmatic eyes: Rigid gas-permeable toric lenses

BCLA CLEAR - Scleral lenses

“…However, the recent development of technology to reliably quantify the scleral profile allows for empirical scleral lens design and fitting. Empirical rigid corneal lens fitting using corneal topography has a number of advantages including reduced chair time with higher first fit success rate [141], greater initial patient satisfaction [142], and optimised lens fitting [143]. Empirical fitting may also be a safer approach, since diagnostic multi-use lenses are not required, and the first lens applied as part of the fitting process is customised to the patient's eye [144].…”

An oblique bitoric rigid contact lens fitting for the management of lens subluxation in Marfan syndrome

“…Oblique bitoric lenses are difficult both to design and manufacture and therefore they are rarely prescribed. An extensive search of the ophthalmic literature reveals no previous case report or paper on this topic and this was only the second time the first author had seen the clinical indication for this type of lens in more than 30 years of optometric practice.…”

“…Using a front surface toric rigid lens in this case would certainly have obviated the need for the oblique bitoric lens and the subsequent difficulties in lens design and manufacture brought on by the combination of the toroidal back surface, the induced astigmatism and the oblique residual astigmatism. Designing a front surface toric rigid lens for the left eye would have simply involved choosing a spherical BOZR that was slightly steeper than the flattest keratometry reading, or ‘simulated keratometry’ reading if using videokeratoscopy, and then incorporating the cylinder that was obtained with the spherocylindrical refraction over the spherical diagnostic rigid lens onto the front surface of the lens.…”

“…Oblique bitoric lenses have a toroidal front and back surface; however, the principal meridians of the toroidal back and front surfaces are not parallel . The design, specification and manufacture of these lenses are very difficult . One solution is to design a diagnostic back surface toric rigid lens which has a toroidal back optic zone, with the appropriate back optic zone radii based on corneal curvature, and a spherical front surface.…”