Evaluation of Post-Trabeculectomy Visual Function Using Orbscan

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Evaluation of Post-TrabeculectomyVisual Function
Using Orbscan

• Kozue Kasai MD1
• Tadashi Nakano MD1 Takahiko Noro MD1
• Hideki Matsuda MD1 Yoshinori Itou MD1
• Masayuki Tatemichi MD2 Hiroshi Tsuneoka MD1

1 The Jikei University School of Medicine
Department of Ophthalmology 2 Showa University
2
Purpose

• 1. To evaluate changes in corneal topographic
• characteristics of patients
• after trabeculectomy (LEC).
• 2. To study the relationship of central corneal
• thickness using Orbscan.

3
Methods and Patients
Post-trabeculectomy group with OAG 24
eyes Control group 16 eyes (nonoperated
eyes of post-LEC patients or volunteer
eyes) TOTAL 40 eyes (24 patients were
examined with Orbscan at our glaucoma outpatient
clinic)
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Methods
Post-LEC group 20 patients 24 eyes Control group 13 patients 16 eyes p value
Age (years) 58.815.2 67.35.6 0.580
Sex (man / woman) 11 / 9 8 / 5 0.508
Visual acuity (log) 0.600.58 1.000.17 0.001
Spherical equivalent D -3.723.45 -1.143.50 0.001
Corneal astigmatism D -1.590.96 -0.800.50 0.004
Tonometry mmHg 11.44.72 16.35.64 0.009
Corneal thickness ?m 55638.6 55843.7 0.978
Postoperative period months 48.151.3
NIDEK ARK-700A Mann-Whitney U-test
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ORBSCAN ver 3.0Evaluation items

• Using an illuminated ring pattern and a beam of
  light,
• Orbscan shows surface power and the front and
  back shapes.
• Not effected by eye dryness. Time less than
  2 seconds

Using two groups (3-mm and 5-mm zone irregularity
ZI)
Mean power The average of the maximum and
the minimum of the cornea refractivity in the
arbitrary measurement point astigmatic power
The difference of the maximum and the minimum of
the cornea refractivity in the arbitrary
measurement point
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Methods
1. Zone Irregularity
5-3-mm ZI Difference between 5-mm ZI and 3-mm ZI
(5-3-mm ZI) as an index of the peripheral area
3-mm ZI Central corneal Irregularity miosis
(daytime condition)
5-mm ZI Corneal irregularity of paracentral
quadrants mydriasis (night condition)
2. Corneal thickness
Corneal thickness was measured by Orbscan
slit scan pachymetry. A representation of the
central corneal thickness. (within a 3-mm
circle from the center)
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Results 1 Irregularity vs treatment

Irregularity


Post-LEC Control
Post-LEC Control
Post-LEC Control
3-mm Zone
5-mm Zone
5-3-mm Zone
Mann-Whitney U-test
P lt 0.5 P lt 0.01 P lt 0.001
Irregularity was greater in the Post-LEC group
than in the control group in all zones.
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Results 2 Irregularity vs Corneal thickness
Irregularity

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10

8
6
4
2
0
lt540 ?m ?540 ?m
lt540 ?m ?540 ?m
lt540 ?m ?540 ?m
3-mm Zone
5-mm Zone
5-3-mm Zone
Mann-Whitney U-test
P lt 0.5 P lt 0.01 P lt 0.001
Irregularity was greater with corneal thickness lt
540?m than with corneal thickness ?540 ?m in the
zones.
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• Report of Evaluation of Post-trabeculectomy
• 1. Video-keratoscopy
• After LEC, the peripheral parts of the cornea
  near the scleral flap area become steep.
• After LEC, visual acuity decreased with
  topographic changes near the scleral flap.
• 2. TMS-1 TMS-2 Video-keratoscopy
• After LEC, there are no changes in SRI or SAI
  as indexes of astigmatic irregularity.
• 3. TMS-1
• After LEC, The steep area around the cornea
  does not influence the corneal center.
• 4. OPD-scan
• After LEC, surgically induced astigmatism and
  higher-order aberrations increase
• significantly. Contrast sensitivity is
  decreased.
• Back Ground
• 1. The importance of quality of vision (QOV) is
  widely recognized.
• 2. Towards the Standaridization of QOV (Quality
  of vision),the list of clinical useful
• parameters need to be evaluated.
• 3. Corneal astigmatism is a factor in QOV. It
  cant be predicted before surgery.

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Conclusion 1

• 1. Irregularity was significantly greater in the
  post-LEC group.
• ZI may serve as a new index of postoperative
  quality of vision.
• 2. Irregularity was significantly greater when
  corneal thickness
• was less than 540?m.
• Central cornea thickness may be a useful
  predictor of surgically
• induced astigmatism.

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Conclusion 2

• 1. Orbscan is an effective method for evaluating
• visual function after trabeculectomy.
• 2. The results of this study suggest that corneal
  
• thickness may have a significant effect on
  changes
• in corneal shape after glaucoma surgery.

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References

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