Abstract
Abstract: :
Purpose: With the recent introduction of ‘accommodative’ intraocular lenses (IOL) there is a need for a method to evaluate their accommodative potential. In most studies, psychophysical measures such as near visual acuity are taken as an indirect ‘proof’ of the funtioning of these new IOLs. However, these measures are strongly influenced by depth of focus or pseudoaccommodation. Actual measurement of IOL movement, or change in anterior chamber depth (ACD), is the most promising way of direct evidence of such an IOL working. This study evaluated whether pilocarpine’s action is similar to physiological ciliary muscle contraction. Methods:Ten healthy emmetropic presbyopic (age: 55 – 60 years), 10 emmetropic young subjects (19 – 25 years) and 30 pseudophakic subjects were included in this study. In the pseudophakic patients, the IOLs implanted were the ‘accommodative’ 1CU IOL (Humanoptics) and 2 open loop 3–piece IOLs (Pfizer 911A, AMO AR40e). ACD and lens thickness (in the phakic subjects only) were assessed with partial coherence laserinterferometry (PCI). For measurements of accommodation to the subjective near–point, a moveable standardized stimulus was coupled to the PCI equipment. ACD was measured with the stimulus at infinity and at the individual near–point. Additionally, PCI measurements were taken 30 minutes after application of 2 drops of 2% pilocarpine. Results: The biometric changes in young phakic subjects under pilocarpine and near stimulus were similar, showing no statistically significant differences. However, in the presbyopic phakic subjects, near point stimulation induced no lens changes, but pilocarpine induced a forward shift of 143 µm ± 82 µm (p<0.001) of the crystalline lens. In the pseudophakic eyes, the 1CU IOLs showed some moderate forward movement 314 µm under pilocarpine application, but not under near point stimulation (p<0.001). There were no significant changes with the standard IOLs. Conclusion: We found pilocarpine to be very similar to near point stimulation in young phakic subjects. However, this is not the case in presbyopic phakic subjects, where pilocarpine seems to act as a ‘super–stimulus’. Similiarily, in pseudophakic eyes, pilocarpine induced more IOL movement than near point fixation.
Keywords: treatment outcomes of cataract surgery • ciliary muscle • anterior chamber