Correlation of Change in Intraocular Pressure with Anterior Chamber Depth

1
Correlation of Change in Intraocular Pressure
with Anterior Chamber Depth Angle after
Cataract Surgery as measured by Anterior Segment
OCT

• Shilpi Pradhan, MD1,3 Martin Wilkes, MD1
  Christopher T. Leffler, MD, MPH1,2 Dennis Pratt,
  MD1,2 Muneera Mahmood, MD1,2

Authors have no financial interests.
1 Medical College of Virginia, Virginia
Commonwealth University, Richmond, Virginia 2
Hunter Holmes McGuire Veterans Affairs Hospital,
Richmond, Virginia 3 Current Cornea Fellow at
University of Pittsburgh Medical Center,
Pittsburgh, Pennsylvania
2
Background

• Studies have shown that cataract surgery on
  average decreases the intraocular pressure (IOP)
  over the long term
• Mean reduction of 2-3 mmHg as well as a decrease
  in number of IOP lowering medications (Shingleton
  et al Pohjalainen et al)
• IOP is reduced more in Primary Angle Closure
  Glaucoma (PACG) compared to Primary Open Angle
  Glaucoma (Hayaski et al) and in glaucoma
  patients compared to patients without glaucoma
  (Dimitrov et al)
• Hypothesis
• The cataractous lens pushes the lens-iris
  diaphragm forward, with narrowing of the AC angle
  and an increase in IOP

3

• Goals and Objectives
• To correlate the change in the anterior chamber
  depth and angle pre- and post-operatively with
  the change in intraocular pressure in patients
  undergoing cataract removal.
• To determine the utility of Anterior Segment
  Optical Coherence Tomography (AS-OCT) in
  pre-operative cataract surgery evaluation.
• Study Design
• IRB approved prospective consecutive case series
  of uncomplicated cataract surgeries with in the
  bag implantation of Alcon SA60AT intraocular lens
  from March 2008 to June 2008 at the Hunter Holmes
  McGuire VA Medical Center, Richmond, VA.

4
Data Collected

• Demographics including age, race, gender
• Approach to surgery, IOL location, and
  complications
• Pre-op IOL Master or immersion A-scan IOL
  calculations
• Pre- and Post-op (4-6 wks) vision, refraction,
  horizontal single line scan un-dilated AS-OCT,
  gonioscopy, ultrasound pachymetry, IOP
  measurement by applanation tonometry
• Measurements taken from AS-OCT Anterior Chamber
  (AC) diameter, AC depth, nasal and temporal
  horizontal AC angle measurements, pachymetry and
  pupil size

5
Visante AS-OCT

• Visante Anterior Segment OCT scans the anterior
  segment of the eye using 1310 nm wavelength of
  light. It takes 4000 axial scans or 8 frames per
  second with a lateral resolution of 60 µm and
  axial resolution of 18 µm (Dada et al).
• May be a more sensitive way to detect narrow or
  closed angles than gonioscopy (Sakata et al)
• Angle width was found to be significantly smaller
  with the presence of peripheral anterior
  synechiae in PACG and allowed quantification of
  the angle in an Asian population (Su et al)
• Horizontal (nasal and temporal) angles were found
  to be most accurate and reproducible (Radkrishnan
  et al)
• Comparable to Ultrasound biomicroscopic images
  and measurements (Dada et al)
• AS-OCT pachymetry correlates with ultrasound (US)
  pachymetry but has slightly lower measurements
  (Li et al)

6
Pre-operative measurements
Post-operative measurements
7
RESULTS

• 72 eyes in 72 patients were studied.
• Mean Age 69.9 years old (SD 10.1)
• 70 out of 72 patients were male
• 61 patients were white and 11 patients were black
  

8

• Table 1. Preoperative and postoperative
  clinical parameters.
• Pre-op Post-op
• Mean (SD) Mean (SD) p value
• OCT findings
• Anterior chamber depth (mm) 2.74 (0.44) 4.14
  (0.32) lt0.001
• Anterior chamber angle (degrees) 27.0 (7.0) 38.0
  (5.2) lt0.001
• Anterior chamber diameter (mm) 12.1 (0.5) 12.2
  (0.4) 0.007
• Corneal thickness (um) 547 (38) 538 (56) 0.30
• Other findings
• Intraocular pressure (mean, mmHg) 14.8
  (2.7) 11.8 (2.8) lt0.001
• postoperative day 1 -- 18.2 (6.6) lt0.001
• postoperative week 1 -- 12.8 (3.6) lt0.001
• postoperative month 1 -- 10.8 (3.1) lt0.001
• Refraction (SE, D) 0.23 (2.5) -0.17 (0.7)
  0.15
• Gonioscopy (Schaffer scale) 2.8 (0.5) 3.2
  (0.5) lt0.001
• Visual acuity (LogMar) 0.49 (0.29) 0.10
  (0.22) lt0.001

9

• Prediction of intraocular pressure
• Pre-operative IOP was predictive of
  post-operative IOP at all times points (plt0.001)
• Pre-operative AS-OCT variables (anterior chamber
  depth, anterior chamber angle, anterior chamber
  diameter) did not predict post-operative IOP
  (pgt0.5, r20.02)
• Intra-operative ultrasound time mean 146 sec
  (SD105) independently predicted post-operative
  day 1 IOP (p0.009)
• The only predictor of post-operative week 1 IOP
  was pre-operative mean IOP (plt0.001, r20.25)
• Post-operative month 1 and mean post-operative
  IOP were independently predicted by pre-operative
  mean IOP (plt0.001) and pre-operative visual
  acuity (plt0.002)
• Comparison of pachymetry values
• Pre-operative AS-OCT 546 um (SD38) US 561 um
  (SD41), r20.88
• Post-operative AS-OCT 545 um (SD40) US 562 um
  (SD47), r20.92
• Similar value pre- and post-operative by AS-OCT
  p0.30

10
Prediction of Post-operative Anterior Segment
Anatomy

• Preoperative AC depth and angle by AS-OCT, lens
  power implanted, pre-operative gonioscopy, axial
  length and keratometry all predicted
  post-operative AC depth in univariate analyses.
• When pre-operative AC depth was controlled for,
  only pre-operative gonioscopy was independently
  predictive (p0.04)
• Post-operative AC angle, AC diameter and
  pachymetry by AS-OCT were all independently
  predicted by their pre-operative values (plt0.001)
• Post-operative gonioscopy was poorly predicted by
  pre-operative gonioscopy (p0.15)

11
Conclusions

• Cataract surgery does lower IOP and increase
  anterior chamber depth and anterior chamber angle
  as measured by Visante AS-OCT.
• Pre-operative anterior segment anatomy by AS-OCT
  did not predict post-operative IOP following
  uncomplicated phacoemulsification in our group of
  patients.
• Higher pre-operative IOP and worse pre-operative
  visual acuity were associated with higher IOP 6-8
  weeks post-operatively.
• Pre-operative gonioscopy and AC depth were
  independent predictors of post-operative AC
  depth.
• Larger sample size and longer follow-up may
  elucidate the utility of AS-OCT in patients who
  need combined cataract and glaucoma surgery.

12
References

• Chandrasekaran S. Cumming RG. Rochtchina E.
  Mitchell P. Associations between elevated
  intraocular pressure and glaucoma, use of
  glaucoma medications, and 5-year incident
  cataract the Blue Mountains Eye Study.
  Ophthalmology. 113(3)417-24, 2006 Mar.
• Dada T. Sihota R. Gadia R. Aggarwal A. Mandal S.
  Gupta V. Comparison of anterior segment optical
  coherence tomography and ultrasound biomicroscopy
  for assessment of the anterior segment. Journal
  of Cataract Refractive Surgery. 33(5)837-40,
  2007 May.
• Dimitrov PN. Mukesh BN. Taylor HR. McCarty CA.
  Intraocular pressure before and after cataract
  surgery in participants of the Melbourne Visual
  Impairment Project. Clinical Experimental
  Ophthalmology. 29(3)128-32, 2001 Jun.
• Hayashi K. Hayashi H. Nakao F. Hayashi F. Effect
  of cataract surgery on intraocular pressure
  control in glaucoma patients. Journal of Cataract
  Refractive Surgery. 27(11)1779-86, 2001 Nov.
• Issa SA. Pacheco J. Mahmood U. Nolan J. Beatty S.
  A novel index for predicting intraocular pressure
  reduction following cataract surgery. British
  Journal of Ophthalmology. 89(5)543-6, 2005 May.
• Li H. Leung CK. Wong L. Cheung CY. Pang CP.
  Weinreb RN. Lam DS. Comparative study of central
  corneal thickness measurement with slit-lamp
  optical coherence tomography and visante optical
  coherence tomography. Ophthalmology.
  115(5)796-801.e2, 2008.
• Pohjalainen T. Vesti E. Uusitalo RJ. Laatikainen
  L. Phacoemulsification and intraocular lens
  implantation in eyes with open-angle glaucoma.
  Acta Ophthalmologica Scandinavica. 79(3)313-6,
  2001 Jun.
• Radhakrishnan S. See J. Smith SD. Nolan WP. Ce Z.
  Friedman DS. Huang D. Li Y. Aung T. Chew PT.
  Reproducibility of anterior chamber angle
  measurements obtained with anterior segment
  optical coherence tomography. Investigative
  Ophthalmology Visual Science. 48(8)3683-8,
  2007 Aug.
• Sakata LM. Lavanya R. Friedman DS. Aung HT. Gao
  H. Kumar RS. Foster PJ. Aung T. Comparison of
  gonioscopy and anterior segment ocular coherence
  tomography in detecting angle closure in
  different quadrants of the anterior chamber
  angle. Ophthalmology. 115(5)769-74, 2008 May.
• Shingleton BJ, Gamell LS, ODonoghue MW, Baylus
  SL, King R. Long-term changes in intraocular
  pressure after clear corneal phacoemulsification
  normal patients versus glaucoma suspect and
  glaucoma patients. J Cataract Refract Surg. 1999
  Jul 25(7)885-90.
• Su DH. Friedman DS. See JL. Chew PT. Chan YH.
  Nolan WP. Smith SD. Huang D. Zheng C. Li Y.
  Foster PJ. Aung T. Degree of angle closure and
  extent of peripheral anterior synechiae an
  anterior segment OCT study. British Journal of
  Ophthalmology. 92(1)103-7, 2008 Jan.
• Vass C. Menapace R. Surgical strategies in
  patients with combined cataract and glaucoma.
  Current Opinion in Ophthalmology. 15(1)61-6,
  2004 Feb.