Silicone hydrogel lenses have been available for more than six years now and have become an accepted and necessary part of clinicians’ inventories. Although myopic and hyperopic lens wearers have received the benefits of greater oxygen transmissibility, astigmatic soft contact lens wearers have until very recently been precluded from these benefits and have not had the option other than daily wear schedules. This year three silicone hydrogel toric lenses will be available to various markets around the world allowing practitioners to offer their patients equivalent levels of oxygen transmissibility to currently marketed spherical silicone hydrogels.
In this case study, we present a patient from our clinic who transferred from spherical soft lenses to silicone hydrogel toric lenses. The patient was a male caucasian, 34 years old, and was an experienced contact lens wearer with low level against-the-rule astigmatism. The patient had an unremarkable medical history, was not taking any medication and had no ocular abnormalities. His presenting spectacle refraction and visual acuity were:
OD –3.00 / -1.00 X 100 6/4.8-2
OS –2.50 / -0.75 X 85 6/4.8
Binocular 6/3.8
The patient was prescribed OD –3.50 D and OS –3.00 D spherical soft lenses for 6-nights extended wear. At dispensing, lens fit was acceptable with good centration and movement, and after 3 months of lens wear visual acuity was satisfactory (Table 1).
Table 1: Visual acuity with spherical soft contact lenses
|
Dispensing |
After 1 month |
After 3 months |
OD |
6/7.5+2 |
6/7.5+1 |
6/7.5+1 |
OS |
6/6.0+2 |
6/7.5+1 |
6/4.8-1 |
Binocular |
6/7.5+2 |
6/6.0-2 |
6/4.8 |
After several months of lens wear, the patient was re-examined and transferred to toric silicone hydrogel lenses. At re-examination his spectacle refraction and visual acuity were :
OD –3.0/-0.75 X 80 6/4.8+1
OS –3.25/-0.75 X 85 6/4.8+1
Binocular 6/4.8+2
He was prescribed silicone hydrogel toric lenses (OD –3.00 / -0.75 X 80; OS –3.25 / -0.75 X 90). At dispensing, lens fit was equivalent to that achieved with spherical soft lenses with good lens orientation. Visual acuity was superior at dispensing compared to his visual acuity with spherical soft lenses, and remained relatively constant over the 3 months of follow-up (Table 2).
Table 2: Visual acuity with toric silicone hydrogel lenses
|
Dispensing |
After 1 month |
After 3 months |
OD |
6/3.8-1 |
6/3.8-2 |
6/3.8 |
OS |
6/4.8 |
6/3.8-2 |
6/3.8 |
Binocular |
6/3.8 |
6/3.8-2 |
6/3.8 |
The patient was very satisfied with his vision. Levels of comfort and ocular redness were no worse than those with his spherical soft lenses, and the patient indicated that he would remain with his toric silicone hydrogels in the future.
A major hindrance to the prescription of toric lenses in the past has been the perception of this lens type as a ‘specialty’ lens requiring more comprehensive and time consuming fitting compared to spherical lenses. Fortunately, recent advances in toric contact lens technology, particularly in design and manufacture, have provided practitioners with readily available frequent replacement toric lenses that are simpler to fit, and offer more consistent performance at relatively lower cost than earlier designs. This shift has meant that toric lenses can be prescribed with the same level of confidence as a spherical lens.
The availability of a range of toric silicone hydrogel lenses means that astigmatic patients can now take advantage of the physiological benefits of higher oxygen transmissibility and to a greater flexibility in wear schedules. These lenses have widened the options practitioners can offer their patients and will be a useful addition to the clinician’s armoury of lenses.
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Jerome Ozkan - B. Optom, UNSW, Sydney, Australia