contact lens primer
RGP Problem Solving 101
BY TIMOTHY B. EDRINGTON, OD, MS, FAAO, & JOSEPH T. BARR, OD, MS, FAAO
Acumen in successful contact lens problem-solving differentiates eyecare practitioners. When a contact lens patient presents with symptoms of poor vision, poor comfort or decreased wearing time decreased wearing time, the practitioner needs to correctly diagnose and manage the case. Solutions to common RGP problems are presented in this month's column.
An Eyelash in My Eye!
RGP comfort is related to interaction of the eyelids with the edge of the lens. When the discomfort is immediate and does not abate with wearing time, suspect edge contour as the culprit. To quickly test this hypothesis, pull the patient's eyelids away from the lens edge. If he immediately reports that the lens is comfortable, modify or reorder the lens to alter the interaction between the lens edge and eyelids by contouring or redesigning the edge profile, changing the fitting curvatures or changing the overall lens diameter. If lens edge inspection reveals a thick edge, thin the edge profile by modification.
If the edges are consistently too thick, instruct your lab to lenticulate, CN bevel or plus the edge contour for your minus power prescriptions (or find a new lab). If the edge appears too sharp, round the edge contour. Prescribing a steeper base curve and/or peripheral curves may reduce edge sensation by "tucking" the lens edge more toward the cornea and away from the eyelid. An alternate approach is to prescribe a flatter base curve to allow the lens to "attach" to the upper eyelid, reducing the frequency of lens edge interaction with the upper eyelid. If the lens edge contains a small chip, modify the lens in-office to reduce the overall diameter of the lens or truncate the area that is chipped. A new lens would also achieve your goal.
If your patient calls to complain of blurry vision in one eye, question him about any loss of vision, onset, etc. Ask the patient which eye is blurred and if vision is similarly blurred through spectacles. If the patient reports blurred vision through spectacles, schedule an office visit. If the patient's monocular vision through spectacles is good, suspect a lens switch (left lens applied to the right cornea and right lens applied to the left cornea). Consult the patient's file to determine what the over-refraction and resulting vision would be if the lenses were switched. Ask the patient to switch the lenses back and call you back to verify clear vision with each eye. To assist the patient in determining right from left lens, RGPs may be prescribed with a different tint for each eye (gReen for the right eye and bLue for the left eye), different overall diameters or a marking near the edge of the right lens.
How Dry I Am!
Solution misuse or a scratched lens surface may contribute to dry eye symptoms. Ask the patient to describe in detail lens care procedures after lens removal and prior to lens application. Many patients clean lenses immediately prior to application or do not adequately clean them. Instruct patients not to clean or reclean the lenses prior to application. Also, re-instruct and reinforce appropriate cleaning, rinsing and storage procedures upon lens removal. Always provide the rationale for your patient education. If the front surface of the lens is scratched, the lens may not wet well. Polish the front surface to enhance lens wettability and to decrease symptoms of dryness. Also provide a complete treatment plan of dry eye therapy.
Solving these complaints will breed loyalty among your contact lens patient base.
Dr. Edrington is a professor at the Southern California College of Optometry. E-mail him at firstname.lastname@example.org.
Dr. Barr is editor of Contact Lens Spectrum and assistant dean of Clinical Affairs at The Ohio State University College of Optometry.