CME With Different Fluidic Parameters
Condition: Cystoid Macular Edema Following Cataract Surgery
MeSH terms: Cataract; Macular Edema
Study type: Interventional
Phase: Phase 4

Summary: 
      Understanding and modulating fluid parameters is an important, but often overlooked aspect of
      phacoemulsification. In a previous study we compared the impact of using high fluid
      parameters versus low fluidic parameters on real-time IOP measured during
      phacoemulsification. The investigators found that using high parameters resulted in a higher
      absolute rise in IOP as well as higher fluctuations in the IOP when compared to low
      parameters. Clinically these higher fluctuations in IOP would translate in a higher chamber
      instability. Based on the results of this study, the investigators decided to take it further
      and study the impact of using high parameters (and thus, higher chamber instability) on
      macular edema and thickness following surgery, in an otherwise uncomplicated surgery.

      Higher fluid parameters during phacoemulsification predisposes the eye to increased macular
      thickness
    

Detailed description: 
      Several studies have shown the adverse impact of an increase in the IOP and IOP fluctuations
      that occur during anterior segment intervention on the posterior segment structures. In human
      volunteers with each incremental increase in IOP the systolic and diastolic flow velocities
      in the short posterior ciliary arteries decreased linearly. This implies that the normal
      healthy eye is not able to autoregulate to maintain posterior ciliary artery blood flow
      velocities in response to acute large elevations in IOP. Vascular insufficiency due to
      abnormal autoregulation has been proposed as a major factor in the development of glaucoma. 1

      It has been postulated that IOP elevation during the LASIK procedure causes mechanical stress
      which may induce tangential stress on the posterior segment.2, 3 Some studies have reported
      that the increase in IOP damages the retinal ganglion cells causing visual field defects.
      Also sudden increases in IOP, although well tolerated may induce changes in the peripheral
      retina.4,5,6

      Several reports propose the occurrence of macular hole, lacquer cracks and choroidal
      neovascular membranes following the LASIK procedure. 3 It has been observed that the rapidly
      fluctuating pressure variations may be detrimental, particularly in susceptible persons with
      compromised ocular blood flow. Rapid IOP changes across a 30-mm Hg range would be predicted
      to influence posterior segment blood vessels.

      In a previous study we compared the impact of using high fluid parameters versus low fluidic
      parameters on real-time IOP measured during phacoemulsification. We found that using high
      parameters resulted in a higher absolute rise in IOP as well as higher fluctuations in the
      IOP when compared to low parameters. Clinically these higher fluctuations in IOP would
      translate in a higher chamber instability.

      We hypothesize that although transient, the increased IOP that occurs during
      phacoemulsification when using high parameters could cause mechanical stress on the eye.
      These higher fluid parameters during phacoemulsification can predispose the eye to increased
      macular thickness.

      To the best of our knowledge there are no published data on impact of IOP changes and
      fluctuation that are induced during cataract surgery on the macula. To investigate this
      further, we decided to study the impact of using high parameters (and thus, higher chamber
      instability) on macular thickness following surgery, in an otherwise uncomplicated surgery.
    

Intervention name(s): microcoaxial phacoemulsification
Intervention type(s): Procedure
Intervention description(s): conventional longitudinal ultrasound
Other intervention name(s): phacoemulsification; small incision cataract surgery
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Quadruple (Participant, Care Provider, Investigator, Outcomes Assessor)
Primary purpose: Prevention
Keywords: CME; OCT; Optical coherence tomography; macular thickness