Heidi Hunter, Optometrist, Marketown Optical Newcastle
A persistent misconception is that toric lenses take longer to fit than spheres but with today’s designs, materials and affordable pricing, optometrists are now better able to meet the specific needs of this patient group.
Paying attention to specific needs is important. What may appear as clinically insignificant to you can often make a big difference to the patient, their lifestyle and to sales.
Forty-five per cent of patients have a cylinder of -0.75 D or more1 and although toric lens prescribing continues to rise, torics account for only 33 per cent of local contact lens fittings.1
Case report 1
SH is a 49-year-old female in monovision who wears a distance spherical contact lens in the right eye. At her three-month after-care visit, she considers returning to wearing spectacles as distance vision is inadequate for night driving. However, her near vision is great.
Habitual distance VA: RE 6/6-3. Distance over-refraction: RE +0.25/-0.75 x 20 (6/5-2).
Although the cylinder is low, I decide it is worth upgrading to a toric lens (Air Optix for Astigmatism). The Air Optix toric lens uses the Precision Balance 8|4 design—a modified prism ballast with a low prism optic zone and the thickest parts of the lens at four and eight o’clock (Figure 1). Spreading the ballast like this and thinning the lens at six o’clock improves lens stability and comfort against the lower lid.2,3
The trial lens immediately adjusts, centres well and is stable on horizontal and diagonal eye movements.
One week later, SH says that she no longer experiences flare and haloes around lights while driving at night, and reports ‘fantastic’ distance vision. Correcting a low cylinder for this patient has given her confidence and enabled her to continue with monovision.
Figure 1. Air Optix for Astigmatism design.
Scribe marks at 3, 6 and 9 o’clock make it
easy to observe lens rotation and stability.
The thickest points of the lens are at 8
and 4 o’clock.
Case report 2
SJ, a 30-year-old female, presents for a second opinion about her soft toric contact lenses fitted at another practice. She is disappointed with the quality of her vision, especially as the day progresses. She wears daily-wear balafilcon A toric lenses and her current pair is three weeks old. A number of different-powered lenses were trialled at the previous fitting. Binocular visual acuity with contact lenses is 6/7.5 and N6.
Current CL Rx: R -1.00/-1.75 x 90; L -1.50/-1.25 x 90. Over-refraction: R 0.00; L +0.25/-0.25 x 90.
Biomicroscopy reveals a rough, uneven specular reflection from the contact lens front surface5 (Figures 2 and 3). Topography over the contact lens confirms an irregular front surface and tear film instability. You can easily visualise the placido ring disturbances, especially between blinks (Figure 4).
Figure 2. Irregular specular reflection from
the contact lens front surface (low magnification)
Figure 3. Irregular specular reflection from the
contact lens front surface (high magnification)
Figure 4. Topography over irregular lens surface shows placido ring disturbance
Based on the end-of-day symptoms and surface condition, I decide to change the lens material, rather than changing the care regime or adding artificial tear supplements. I trial Air Optix for Astigmatism (lotrafilcon B), which uses a permanent plasma treatment, to create a continuous hydrophilic lens surface, for better wettability and deposit resistance.6,7 The trial lenses orientate well and remain stable with blinking and eye movements.
At the three-week after-care visit, SJ is surprised by the dramatic improvement in vision quality and comfort. Biomicroscopy shows a smooth, even lens surface and stable tear film. The topographer placido images are impeccable, with no observable tear degradation between blinks, despite the lens age (Figure 5). The stable images are consistent with the improvement to symptoms and show how assessing the surface late in the wearing period helps you understand lens performance.
Figure 5. Topography over the smooth contact lens front surface
shows intact placido rings, with no observable tear degradation between blinks
Case report 3
AF, a male high school student, presents with an optometric referral for behavioural assessment as he is having trouble changing focus and copying from the board when wearing contact lenses. Artificial tear eye-drops do not help. He has no symptoms with his single vision spectacles but he is an active, sporty teenager and would rather wear contact lenses. The referring optometrist recommended progressive lenses as over-spectacles for classwork but AF is not keen.
Contact Lens VA: R 6/6; L 6/6-3. Stereopsis (Titmus circles): Number 7 circles (with effort). Near phoria: 2 eso. Over-refraction: R +0.25/-0.75 x180 (6/5-3); L +0.25/-1.00 x180 (6/5-1)
The symptoms and over-refraction suggest correcting the astigmatism may help. A trial frame over-refraction is an easy way to show AF the benefit to upgrade to a toric lens. VA with Over-Rx: R 6/5-3; L 6/5-1. Stereopsis with Over-Rx: Number 9 circle (with ease, 40 sec arc). Near phoria with Over-Rx ortho.
Air Optix for Astigmatism contact lenses are prescribed and at the one-week review, the lenses are perfectly aligned and stable. AF reports he no longer has a delay in changing focus from the board and binocular tests are stable. The toric lenses provide noticeable relief of eyestrain and improve comfort.
A toric providing more comfort than a spherical lens goes against what you would expect clinically, based on lens thickness, but shows the ‘psychological’ comfort provided by clearer vision. Correcting the cylinder for Patient AF has removed the effort he needed to see well.
Astigmatic patients leaving your practice with unexpected improvement in vision or comfort will tell their friends about their experience. Knowing how to provide a positive contact lens experience for these patients is about looking for the details that make the difference; fixing a low uncorrected cylinder, providing a better lens surface and improving all aspects of eye comfort.
You can see from these examples that modern toric lenses are extremely easy to fit and orient almost instantly, which makes it all the easier for you to turn a patient’s situation around.
Optometrist Heidi Hunter of Marketown Optical Newcastle was commissioned by Alcon to contributed this article. Air Optix and Precision Balance 8|4 are trademarks of Alcon.
Jenny Saunders is thanked for her editorial assistance.
- Morgan PB et al. International Contact Lens Prescribing in 2012. Contact Lens Spectrum www.clspectrum.com/articleviewer.aspx?articleID=107854 accessed 25/8/13.
- Support documentation for Air Optix for Astigmatism, Data on file, 2006.
- Neubert, Soft Toric In-Market Validation US Trial, Data on File, 2005.
- Lens specifications are as published on the manufacturers’ websites and also in Contact Lenses 2012, supplement to Australian Optometry, Optometrists Association Australia. 2012: 30-32.
- Jagmohan S. Smooth, even reflection is a good sign. Australian Optometry May 2013. p9.
- Santos L, Rodrigues D, Lira M, Oliveira MECDR, Oliveira R, Vilar EY-P, Azeredo J. The influence of surface treatment on hydrophobicity, protein adsorption and microbial colonisation of silicone hydrogel contact lenses. Contact Lens & Anterior Eye 2007; 30: 3: 183–188. doi:10.1016/j.clae.2006.12.007.
- Nash W, Manal G, Mowrey-McKee M. A comparison of various silicone hydrogels lenses; lipid and protein deposition as a result of daily wear. American Academy of Optometry 2010; p. E–abstract 105110. Retrieved from http://www.aaopt.org/meetings/submissions/search