The material characteristics of hydrogel
contact lenses are generally more forgiving than those of GP lenses.
Yet the wearing of virtually any type of contact lens including a
soft lens can result in undesired effects on the cornea.
surface distortion associated with hydrogel lens wear isn't common
in clinical practice, and consequently you may miss it if you don't
include it as a possibility while working through a clinical
differential diagnosis. The following represents just such a case of
hydrogel lens-related corneal distortion.
24-year-old male who wore Acuvue 2 (Vistakon) lenses on a daily wear
basis for his -6.25DS of myopia presented with a complaint of double
vision in his right eye only. The patient reported that the diplopia
was mild, the onset occurred sometime during the previous three
weeks, it wasn't getting worse and it wasn't associated with any
event or activity. The visual disturbance was present with or
without his contact lenses. He had no general health problems and
was not taking any medications.
vision was slightly reduced in the affected eye, with best
correction and preliminary tests indicating full versions and
vergences, no tropia and no significant phorias. I performed
topography OU (Figure 1a) and
noted some distortion of each eye at this initial visit.
Figure 1a and 1b. Axial maps OU at the initial presentation (top)
and after one month daily wear of higher-Dk, silicone hydrogel
(2003) recommended using lenses with higher oxygen transmissibility
to alleviate the relative hypoxia that may be associated with
hydrogel contact lens-induced corneal warpage. With this in mind, I
dispensed Acuvue Advance (Vistakon) lenses (Dk = 60) of identical
design to the patient's Acuvue 2 (Dk = 28) lenses.
patient returned one month later reporting that his double vision
was gone and that he had no continuing problems. His corrected
visual acuity was now 20/20 in his right eye and topography
indicated a more regular corneal surface (Figure
distortion of some degree is expected in lens wearers, and its
effects on corneal surface regularity are typically sub clinical and
insignificant. Even so, it's one reason why a lens wearer must cease
lens wear for a period of time before undergoing evaluation as a
refractive surgery candidate.
reminds us that corneal distortion associated with hydrogel lens
wear can progress to a level at which it affects vision.
Fortunately, the effects seem reversible over time by increasing
oxygen delivery to the cornea. But do remember the value of
assessing the regularity of the corneal surface when contact lens
wearers present with visual disturbances that are unusual or
unexplained by more routine causes.