Druginduced accommodative and nonaccommodative conditions are different from stimulusinduced accommo

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Drug-induced accommodative and non-accommodative
conditions are different from stimulus-induced
accommodative condition

• Masahiro Maeda, M.D., Hideki Nakamura,M.D.,
  Kazuo Ichikawa,M.D., PhD
• Social Insurance Chukyo Hospital
• Nagoya, Japan

No Financial Interests
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Purpose

• Pilocarpine and tropicamide are used for making
  an accommodation and non-accommodation because
  ciliary muscle is contracted by pilocarpine and
  is relaxed by tropicamide. We examined the
  crystalline lens thickness before and after
  application of pilocarpine and tropicamide using
  AC Master (partial coherence interferometory
  Zeiss) to confirm if there are differences
  between stimulus-induced accommodation status and
  drug-induced accommodation status of the anterior
  structures.

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AC Master partial coherence interferometory
beam splitter
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The internal fixation target, a Badal lens
system, was used to maintain constant size at all
distances of the target. The measurement was
performed along the optic axis by aliening
Purkinje-Sanson image. The error margin of
ACMaster is reported only about 10 µm.

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Method

• 50 eyes of 36 normal volunteers
• They had no history of ocular diseases, trauma or
  surgery besides ametropia.
• During accommodation, anterior chamber depth
  (ACD) and crystalline lens thickness (LT) were
  measured at 60 min after application of 2
  pilocarpine or at 30 min after application of
  0.5 tropicamide ophthalmic solutions.
• Following abbreviations are used.
• ACD Anterior lens surface (ALS)
• ACD LT Posterior lens surface (PLS)

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Result The mean change of the crystalline lens
thickness
The mean change of the crystalline lens thickness
compared to baseline. 1.0-4.0D 50.631.4µm/D
in stimulus-induced accommodation
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The mean change of ALS PLSstimulus-induced
accommodation-
The mean change of the ALS and PLS compared to
baseline (meanSD). Negative values indicate a
forward movement, positive values indicate a
backward movement of ALS and PLS,
respectively. 2.0D-4.0D significant anterior
movement is observed ONLY on ALS (Plt0.001)
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The mean change of ALS PLSdrug-induced
accommodation-
pilocarpine
tropicamide
The mean change of the ALS and PLS compared to
baseline of 0D without instillation. Negative
values indicate a forward movement, positive
values indicate a backward movement of ALS and
PLS, respectively. Significant differences are
observed on changes of ALS PLS ( Plt0.001
paired-t test)
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The mean change of the crystalline lens
thicknessdrug-induced accommodation-
Significant difference is observed on both
changes compared to baseline of 0D without
instillation (Plt0.001Wilcoxon signed-rank test)
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Discussion

• In accommodation, ciliary muscle contraction
  releases its tension on the zonules, which allows
  the lens to become thicker. The changes of
  crystalline lens thickness per diopter was
  50.631.4µm/D, which is in agreement with the
  results of other previous reports. (Beauchamp
  Mitchell, 198559µm/D Storey Rabie,1983
  54µm/D Garner Yap, 1997 57µm/D Dubbleman,
  2005 45µm/D) .

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• Pilocarpine is a cholinergic drug which acts on
  a  muscarinic receptor subtype (M3) in the
  sphincter muscle and ciliary muscle, and causes
  the contraction on these muscles.
• Tropicamide is a rapidly acting parasympatholytic
  drug which causes a relaxation of the ciliary
  muscle and induces cycloplegia and mydriasis for
  short duration.
• Because of these effects of the drugs,
  pilocarpine and tropicamide have been used to
  study about the accommodation and
  pseudo-accommodation.

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• In accommodation, not only LT, but also radius of
  curvatures and refractive index are changed. From
  this point, we should avoid judging
  accommodation by LT change only. While 50.6µm/D
  is observed in LT change for a normal
  accommodation, 152µm is observed after the
  application of pilocarpine and tropicamide.
• From the facts above (also the fact that a
  catastasis of PLS changed for 60µm), it is
  possible that 1.5-2.0D of accommodation is
  induced by the drug effect only.
• Koeppl et al. reported that pilocarpine acts
  physiologically in young phakic subjects, but
  is a super stimulus in presbyopic phakic
  subjects. But in this study,
  drug-induced accommodation is unphysiological
  even in young subjects.

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Conclusion

• Stimulus-induced accommodation does not moves
  the PLS, however, pilocarpine moves the PLS
  forward and tropicamide moves it backward.

• This study suggests that we should take into
  consideration that drug-induced accommodation
  status and relaxation of accommodation are
  different from the stimulus-induced accommodation
  status.