CONTACT LENS OPTIONS FOR PRESBYOPIA

Fitting presbyopic contact lens corrections successfully is a very rewarding part of contact lens practice. It builds patient loyalty, creates more word of mouth referrals, and the practitioner reaps the financial benefit of servicing this largely untapped market. Silicone hydrogels can play an important role in providing presbyopic patients with excellent and convenient vision correction.

Figure 1 - Presbyopes: Global - click to enlarge Presbyopia Market The number of presbyopes worldwide is rising at a staggering rate, and is expected to reach 2.3 billion by the year 2020. In the US alone, 42% of the population or 135 million people will be presbyopic by 2020. These figures are 66% of the population or 66 million presbyopes in Japan, and 26% of the population or 344 million presbyopes in India by 2020.

Figure 2 - Patient attitudes - click to enlarge What patients want A survey by Edmunds and Reindel (2003) showed 91% of current contact lens wearers among 35 to 55 year olds are committed to continuing with contact lens wear. However, although 84% of the US population over 55 years of age require vision correction, only 5% wear contact lenses, whereas 50% of the US population between 25 to 34 years of age require vision correction, and about half wear contact lenses. The introduction of silicone hydrogels may provide a new boost to this market, by providing patients the convenience and comfort they want.

Figure 3 - All ages wear contact lenses - click to enlarge

One of the reasons for the current decline in contact lens use with age may be the relative complexity of providing satisfactory vision correction for presbyopia.

Contact lenses for the correction of presbyopia have been available for many years, and options include:

• Simultaneous vision designs - Each eye is corrected for distance and near simultaneously. The brain perceives two images at once from each eye, and therefore to see clearly, the presbyope learns to automatically process the image which is in focus for the particular viewing distance (distance or near). Patients wearing simultaneous vision design contact lenses often complain of haloes, ghosting and difficulty with night vision.
  
• Alternating vision designs - These utilize two distinct zones similar to "bifocal" spectacle lenses, one devoted to the distance prescription, and one to the near. Contact lenses must move upwards on the eye during downgaze (a phenomenon called "translation") while viewing close distances so that the correction zone over the eye changes from the distance prescription to the near. Patients wearing alternating vision design contact lenses often complain that lenses are uncomfortable, as the majority of translating contact lenses are gas permeable or truncated.
  
• Monovision - One eye is corrected with the distance prescription, while the other eye is corrected for near, and the presbyope automatically selects the in-focus image, providing relatively normal continuous vision. Depth perception can be somewhat compromised, however patients usually adapt quickly and learn to utilize alternate visual cues when judging distances. Monovision has proven to be the most successful correction option for presbyopes to date, with a fitting success rate of approximately 80%.

While silicone hydrogel lenses are not yet available in specific presbyopia designs such as bifocals, they are an excellent choice for monovision. Silicone hydrogel lenses are comfortable to wear, and offer the added convenience of extended wear, which minimizes the need to handle the lenses on a regular basis. They are particularly useful for patients who have difficulty seeing to insert and remove their lenses and who may find daily handling of contact lenses problematic.

High Dk lens materials also offer ocular health benefits, and mean the risk of neovascularisation and corneal oedema with conventional hydrogel contact lens wear, due to the corneal endothelial pump losing its efficiency with age, is minimized.

Monovision was the preferred mode of correction compared to bifocal contact lenses for subjects participating in a one year clinical trial by du Toit et. al., and was also selected as the first preference for practitioners fitting presbyopic corrections (Edmunds and Reindel, 2003)

Figure 4 - Preference at last visit - click to enlarge	Figure 5 - Practitioner attitudes - click to enlarge

By using silicone hydrogel lenses in a monovision mode, practitioners can provide their presbyopic patients with the most preferred and successful mode of correction, together with the added advantages of good ocular health with highly oxygen permeable materials, and the significant benefits of the convenience of continuous wear.

In the practice this month details how monovision silicone hydrogels have rejuvenated Narelle Hine's contact lens practice for presbyopic hyperopes.