Alterations of the macular anatomy following pars plana vitrectomy for pseudophakic ...

195 Pages·2017·1.28 MB·English

“Alterations of the macular anatomy following pars plana vitrectomy for
pseudophakic rhegmatogenous retinal detachment as prognostic factors for the final
visual outcome: a spectral – domain optical coherence tomography based study”

by
Dimitrios K. Tsouris

Thesis
submitted in partial fulfilment
of the requirements for the Degree of
Master in Medical Research Methodology

Aristotle University of Thessaloniki

Faculty of Health Sciences - Department of Medicine

Thessaloniki, May 2017
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Supervisor
Professor Nikolaos Ziakas

Members of Assessment Committee
Professor Panagiotis Oikonomides
Professor Fotios Topouzis

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“…the storm inside…”

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Acknowledgments

During the lifelong, blessed journey to our cavafian Ithaca, we may come across a
small company of particular people gifted with unique personalities that share the
intrinsic capability of inflicting a positive shock to our mentality. There is a word for
them: mentors.
I was fortunate to encounter this special breed during my recent MSc studies at the
Aristotle University and they have names: Professor Anna-Bettina Haidich, Professor
Apostolos Tsapas and Professor Dimitrios Goulis. They all share common
characteristics such as kindness, patience, wisdom. Each one of them guided me into
new paths of knowledge and opened for me a whole new world of science. “It
mattered not how strait the gate, how charged with punishments the scroll”. At the
end of the course, through their assistance, the mission was accomplished.
The end product of this intense effort of mental discipline, the present Thesis, was
evaluated by a committee of three eminent Professors of Ophthalmology: Nikolaos
Ziakas, Panagiotis Oikonomides and Fotios Topouzis. Their valuable remarks were
the beacons that tremendously succored me to improve and finally conclude the
dissertation. In order to fulfill this role, they invested time, an asset extremely
precious for scientists of their caliber. Sincere gratitude is verily owed.
The MSc tutorials were delivered through a carefully selected team of young tutors,
each one of them brilliant and always keen on answering my endless questions.
Konstantinos Bugiukas, Georgia Vourli, Stergios Polyzos, Gesthimani Mintziori,
Thomas Karagiannis, Aris Liakos and Pascalis Paschos, supported by the restless
Alexandra Karagianni comprised an amazing team that acted with choreographic
elegance and stamina. I feel the need to specifically mention Dr. Fani Apostolidou
Kiouti, whose kind contribution during the statistical analysis was of paramount
importance.
Last but not least, it is a sacred impetus to express my gratitude to my precious family
through these lines. Once again, during this endeavor, I had to demand unconditional
support and limitless patience of Job on behalf of my wife Maria and my two
daughters Olga and Elizabeth. Once again, they unquestionably delivered. They give
meaning to my world. The breath of my life.

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Word count (excluding Tables, Figures and the Appendix): 9886

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Table of Contents

I. Abbreviations ......................................................................................................... 8
II. List of Tables ......................................................................................................... 9
III. List of Figures ...................................................................................................... 10
IV. GENERAL PART ................................................................................................ 12
A. Introduction ................................................................................................... 12
B. Main entities .................................................................................................. 12
1. Retina and Vitreous ................................................................................... 12
2. Rhegmatogenous Retinal Detachment ....................................................... 15
3. Phacoemulsification................................................................................... 17
4. Pars Plana Vitrectomy ............................................................................... 19
5. Spectral - Domain Optical Coherence Tomography (SD-OCT) ............... 21
V. SPECIAL PART .................................................................................................. 23
A. Aim............................................................................................................... 23
B. Material and Method ................................................................................... 24
1. Study characteristics………………………………………..……………...24
C. Patients: inclusion and exclusion criteria ..................................................... 25
1. Inclusion criteria………………………………………………………....25
2. Exclusion criteria………………………………………………………...25
D. Method: study protocol, techniques, instrumentation ................................... 26
E. Study outcomes ............................................................................................. 28
F. Ethics ............................................................................................................. 30
G. Statistics ......................................................................................................... 30
H. Data presentation............................................................................................ 32
1. Descriptive statistics .................................................................................. 32
2. Measures of association ............................................................................. 33
3. Results interpretation ................................................................................. 33
4. Hypothesis testing of a continuous outcome in two independent samples 34
5. Univariate linear regression analysis ...................................................... 35
6. Multivariate linear regression analysis ...................................................... 36
I. Results ......................................................................................................... 39
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1. Main aim .................................................................................................... 39
2. Secondary aims .......................................................................................... 39
J. Tables ........................................................................................................... 40
K. Figures .......................................................................................................... 44
L. Discussion.................................................................................................... 55
1. Research question and principal findings .................................................. 55
2. Strengths and weaknesses .......................................................................... 56
3. Critical appraisal of the literature .............................................................. 57
4. Clinical implications .................................................................................. 58
5. Future research .......................................................................................... 59
6. Conclusions ............................................................................................... 60
VI. References.................................................................................................... 62
VII. Appendix ...................................................................................................... 67

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I. Abbreviations

AIC: Akaike Information Criterion
BCVA: Best Corrected Visual Acuity
C3F8: Perfluoropropane
CI (95%): Confidence Interval (95%)
ELM: External Limiting Membrane
ERM: Epiretinal Membrane
GCL: Ganglion Cell Layer
ILM: Internal Limiting Membrane
INL: Inner Nuclear Layer
IPL: Inner Plexiform Layer
IQR: Interquartile Range
IS / OS: Inner Segment / Outer Segment (junctional zone of the photoreceptors)
logMAR: logarithm of Minimal Angle of Resolution
NFL: Nerve Fiber Layer
ONL: Outer Nuclear Layer
OPL: Outer Plexiform Layer
OR: Odds Ratio
PPV: Pars Plana Vitrectomy
PVD: Posterior Vitreous Detachment
RD: Retinal Detachment
RPE: Retinal Pigment Epithelium
RRD: Rhegmatogenous Retinal Detachment
RSE: Residual Standard Error
SD: Standard Deviation
SD - OCT: Spectral Domain Optical Coherence Tomography
SF6: Sulfur Hexafluoride
VIF: Variance Inflation Factor

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II. List of Tables

Table 1: Descriptive statistics of the continuous variables .......................................... 40
Table 2: Measures of association ................................................................................. 40
Table 3: Normality tests p – values (Shapiro – Wilk) ................................................. 41
Table 4: Mann – Whitney U tests p – values of the outcome variable “BCVA post op”
population distributions ............................................................................................... 41
Table 5: Mann – Whitney U test of the postoperative anatomical parameters in
relation to the preoperative macular status .................................................................. 41
Table 6: Univariate Linear Regression analysis cumulative results ............................ 42
Table 7: Comparative cumulative results of the Univariate and Multivariate Linear
regression analysis ....................................................................................................... 43

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III. List of Figures

Figure 1: Diagnostic plots for the multiple regression model...................................... 37
Figure 2: Scatter plots of the “BCVA post op”, “Fovea” and “Ganglion” variables... 38
Figure 3: Bar plot of the variable “Gender” ................................................................. 44
Figure 4: Bar plot of the variable “Macular status – preoperatively” .......................... 44
Figure 5: Pie chart of the “Gas” type used as tamponade agent .................................. 44
Figure 6: Bar plot of the variable intraoperative drainage “Retinotomy” ................... 45
Figure 7: Bar plot of the variable intraoperative “IVTA” use ..................................... 45
Figure 8: Bar plot of the variable postoperative “ERM” ............................................. 45
Figure 9: Bar plot of the variable postoperative “CME” ............................................. 46
Figure 10: Bar plot of the variable postoperative “IS/OS” junctional zone integrity .. 46
Figure 11: Bar plot of the variable “Submacular fluid” presence ................................ 46
Figure 12: Bar plot of the variable postoperative “ELM” integrity ............................. 47
Figure 13: Histogram of the variable “Age” ................................................................ 47
Figure 14: Q – Q plot of the variable “Age” ................................................................ 47
Figure 15: Histogram of the variable “BCVA preop” ................................................. 48
Figure 16: Q – Q plot of the variable “BCVA preop” ................................................. 48
Figure 17: Histogram of the variable “BCVA post op” ............................................... 48
Figure 18: Q – Q plot of the variable “BCVA post op” ............................................... 49
Figure 19: Histogram of the variable “Fovea” ............................................................. 49
Figure 20: Q – Q plot of the variable “Fovea” ............................................................. 49
Figure 21: Histogram of the variable “Volume” .......................................................... 50
Figure 22: Q – Q plot of the variable “Volume” ......................................................... 50
Figure 23: Histogram of the variable “Average Thickness” ........................................ 50
Figure 24: Q – Q plot of the variable “Average Thickness” ........................................ 51
Figure 25: Histogram of the variable “Ganglion” ........................................................ 51
Figure 26: Q – Q plot of the variable “Ganglion” ....................................................... 51
Figure 27: Box – whisker plot of the variable “BCVA preop” in relationship to the
“preoperative macular status” ...................................................................................... 52
Figure 28: Box – whisker plot of the variable “BCVA postop” in relationship to the
“preoperative macular status” ...................................................................................... 52
Figure 29: Box – whisker plot of the variable “BCVA postop” in relationship to the
postoperative integrity of the “IS/OS” junctional zone ............................................... 52
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