Asymptomatic GP wearer has both dryness and redness. Deficiencies in tear quality and volume as well as meibomian gland dysfunction and giant papillary conjunctivitis have been ruled out. Both eyes have grade 1+ bulbar conjunctival injection and 1+ to 2 3 o’clock and 9 o’clock staining. Refraction is OD –6.50 –1.25 x 175 and OS –7.50 –1.00 x 005. Sim Ks are 43.25 @ 180/44.25 @ 180 OD and OS. Lens parameters are 0.15mm center thickness OD and OS; 9.6mm overall diameter OD and OS; base curve radii of 7.89mm OD and 7.85mm OS; power of –5.75D OD and –6.50D OS. Visual acuity fluctuates with the blink from 20/15 to 20/25 OD and OS. The lens is picked up superiorly with the blink and then drops inferiorly. The fluorescein pattern is aligned with excessive edge clearance, and there are no surface deposits.
Rule Out Factors These can include medications, environmental factors, and those pertaining to general health. From a lens design standpoint, you can likely rule out base curve radius (BCR); it is possible that a steeper BCR could improve centration, although the current lenses have an alignment pattern. A smaller diameter could reduce overall mass but would not be a primary factor.
Management Factors Several factors can help reduce or eliminate these symptoms and clinical signs:
- Edge Clearance Excessive edge clearance funnels the surrounding tears under the lens, which can result in desiccation in the exposed 3 o’clock and 9 o’clock areas along with conjunctival injection. Likewise, the excessive edge clearance superiorly can cause greater lens edge-lid interaction, possibly compromising blink quality and pushing the lens inferiorly (Musset and Stone, 1981).
Reduce edge clearance by steepening the peripheral curve radius, decreasing the peripheral curve width, or increasing the number of peripheral curve radii. A peripheral aspheric design can be used as well. When in doubt, your laboratory consultant can help with the changes.
- Ultrathin Design Most GP materials can be manufactured in an ultrathin design with a center thickness of 0.10mm to 0.12mm in high-minus powers. This would reduce mass 30% to 40% and likely improve centration.
- Lenticulate A plus-lenticular design is recommended for all high-minus powers. The greater edge thickness with a high-minus-power lens can result in greater lens edge-lid clearance interaction and similar negative outcomes as with a high edge. A plus-lenticular design will decrease edge thickness.
- Centration Regardless of the fitting relationship, a well-centered lens is more comfortable and optimizes the quality of the blink. A lens that decenters inferiorly results in a higher incidence of corneal desiccation (Henry et al, 1987). Fortunately, due to the availability of ultrathin designs and more consistent edge clearance peripheries, it is apparent that today’s designs are more likely to center well and result in less corneal desiccation (Azhar et al, 2015).
Where To Go for Help Your best aide when troubleshooting GP wearers is always your laboratory consultants. In addition, the GP Lens Institute has numerous resources available online at www.gpli.info . CLS
For references, please visit www.clspectrum.com/references and click on document #263.