Of the RGP Patient
BY LORETTA B. SZCZOTKA, OD, MS, FAAO
Aftercare procedures are equally, if not more, important as the original RGP lens fitting because the initially-fit lenses may have unanticipated complications which require correction at any time in the post-fitting care. In fact, most fitters believe that patients should be followed at minimum once annually; therefore, the aftercare of a contact lens patient can be considered never complete. Additionally, there is a general consensus that RGP patients should be examined more frequently during the first few months of initial RGP wear.
Many procedures can be performed at follow-up visits. I will highlight only three procedures that I often use to problem solve.
At any aftercare visit, over-refraction can reveal power changes required due to unanticipated lacrimal lens formations, changes in refractive error, patient-induced lens power changes, lens warpage or lens flexure. A common clinical technique during subjective refraction is obtaining both spherical and sphero-cylindrical endpoints. In cases of spherical lens fitting, spherical power modifications can be demonstrated and the resultant visual acuity measured. If the vision is inadequate, perform a sphero-cylindrical over-refraction. A repeatable cylindrical over-refraction can suggest spherical RGP lens flexure.
Thin RGP lenses can flex approximately one-third of the corneal toricity with increased chance of flexure with steeper and larger lenses. Flexure can be confirmed by manual or automated keratometry over the lenses. Any toricity detected will provide an index of lens flexure over a spherical RGP lens.
Evaluating the patient's head posture, blink habits and palpebral aperture can provide important information on lens adaptation and lid effects. New RGP lens wearers often present with partial blinks or a narrowing of their palpebral aperture in an attempt to decrease lid sensations. However, RGP wear has also been shown to induce true acquired non-senile blepharoptosis from mechanical manipulation of the eyelids or mild contact lens-induced lid inflammation. The palpebral aperture can decrease by approximately 0.5mm in eyes which wear RGP contact lenses.
Lastly, a fluorescein pattern evaluation should always be performed either with the Burton lamp, the biomicroscope or both. The Burton lamp is limited as a single method of assessment because of its limited magnification and inability to observe the fluorescein patterns of materials incorporating ultraviolet blockers. The biomicroscope should be enhanced with a cobalt blue and a yellow barrier filter (Wratten #12 yellow) to enhance the contrast of the tear film.
Assess the fluorescein pattern at every aftercare visit to see if the lens fit has changed. In the early aftercare phase, fluorescein pattern interpretations can vary as the patient adapts to his lenses and reflex tearing subsides. It is not uncommon for a lens to be judged fit with apical clearance at a dispensing visit, yet recorded to be fit with apical touch at a progress evaluation. Alternatively, the peripheral lens system may appear steeper than initially documented once reflex tearing has subsided. This can be detected by insufficient edge clearance, peripheral seal-off or even an epithelial indentation ring.
Because corneal shape and posterior lens tear film thickness changes may change as the patient adapts to new lenses (which influence the examiner's interpretation of the lens fit), often RGP lens parameter changes are made at the two- or four-week aftercare visit when lens fitting relationships have stabilized.
Dr. Szczotka is an assistant professor at Case Western Reserve University Dept. of Ophthalmology and Director of the Contact Lens Service at University Hospitals of
Contact Lens Spectrum, Issue: December 2001