GP Lens Case Grand Rounds Troubleshooting Guide – 14

Continuous Wear: Robert M. Grohe, OD, FAAO

Background

TH is a GP continuous wearer who has recently experienced a tendency for either lens to unpredictably pop out during the day. This has required two lens replacements in the last three months. She feels this has occurred because of defective lenses. Upon questioning, the patient admits to aggressively rubbing and grinding away the lenses between her fingers until they are “squeaky clean.” She has cleaned her lenses this way for years and is not about to change her “successful” habit. She has worn GP lenses on a daily or continuous wear basis for eleven years.

Test Procedures, Fitting/Refitting, Design and Ordering

Visual Acuity (with GP Lenses)/Over-Refraction:

OD: 20/30 +0.75 DS 20/20
OS: 20/40- +1.00 DS 20/20

Manifest Refraction:

OD: -10.00 DS 20/20-1
OS: -11.00 DS 20/20

*Current GP Lenses Verified As:

ODOS

Base Curve Radius (BCR): 7.89mm 7.95mm
Overall Diameter (OAD): 9.40mm 9.40mm
Power: -11.00D -11.50D

* (Both current base curve mires were fuzzy and slightly doubled.)

Original GP Lenses Dispensed Two Years Ago:

ODOS

Base Curve Radius (BCR): 7.76mm 7.83mm
Overall Diameter (OAD): 9.40mm 9.40mm
Power: -10.25D -10.50D

Ordering of New GP Lenses:

Some of the original lens parameters, with current power adjustments to best match with an appropriate lens-to-cornea fitting relationship, were selected.

ODOS

BCR: 7.76mm 7.83mm
OAD**OZD: 9.40/7.60mm 9.40/7.60mm
***SCR/W: 10.0/.4mm 10.0/.4mm
****PCR/W: 12.0/.4mm 12.0/.4mm
Power: -9.25D -10.00D

**OZD = Optical Zone Diameter
***SCR/W = Secondary Curve Radius/width
**** PCR/W = Peripheral Curve Radius/width

Patient Consultation and Education

The key factor in eliminating lens ejection and radical base curve flattening is to establish new handling techniques for the patient. Periodically re-verifying lens parameters, especially base curve radius and power, can be very helpful in identifying early lens parameter mishandling changes. Many follow-up visits may be consumed by reviewing and educating reluctant patients to alter their previously successful rub and grind mishandling in favor of the kinder and gentler approach in the palm of the hand. Handouts, as well as staff and practitioner demonstration and encouragement, are essential in-office educational tools to retrain patients as to updated handling of current GP lens materials.

Follow-Up Care/Final Outcome

TH resumed seven day continuous wear but quickly lost a lens. An extensive lens handling update was conducted including redundant instruction by both contact lens technicians and the practitioner. It was emphasized that new GP lenses are safer yet require kinder and gentler handling that is different from previous handling techniques. After some reluctance and several handling relapses, TH slowly acquired the patience to use the new kinder and gentler handling habit. With these new techniques, she found her continuous wear increase from one to two weeks as no subsequent lens damage or loss occurred over a two year period. After two years, visual acuity with the same lenses was 20/20 OD, 20/20+ OS and 20/20+ OU.

Discussion, Alternative Management Options

While the best kept secret in continuous contact lens wear is the success of GP lenses, the most frustrating challenge can be a longstanding habit of patient lens mishandling. Before dispensing the new lenses it is helpful to inform the patient of recent lens quality inspection and verification for defect-free lenses. Establishing that newly dispensed lenses are defect-free sets the stage for future success and eliminates claims against lens material.

In GP continuous wear it is also important to consider any long term lens parameter change by periodically verifying lens parameters for stability. The most common parameter changes include increases in minus power, radical base curve flattening and annular calcium-like deposit build-up on the anterior surface peripheral bevel.

Power changes and base curve radius changes can usually be avoided with proper handling. Calcium build-up may require the combined use of Miraflow (Ciba Vision) and an abrasive surfactant at each lens removal. If this fails, converting to six month disposable GP lenses should eliminate this recurring and stubborn deposit problem.

Other options may include the use of more durable GP materials such as Paragon HDS 100 (Paragon Vision Sciences) or Boston XO (Polymer Technology Corporation) to prevent parameter shifting. Increasing the lens thickness by 0.03mm can also reinforce long term lens structural integrity.

Ultimately, both the staff and practitioner should assume some degree of handling regression and ask the patient every visit to briefly demonstrate how they clean their lenses. This will avoid future lens flexure or breakage and discourage any blame against lens material quality.

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