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Trial registered on ANZCTR

Registration number
Ethics application status
Date submitted
Date registered
Date last updated
Type of registration
Prospectively registered

Titles & IDs
Public title
The determinants of corneal curvature in healthy participants and in cataract surgery patients
Scientific title
Analysis of corneal refractive power changes associated with accommodation, corneal biomechanics and cataract surgery
Secondary ID [1] 290447 0
Nil known
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Cornea after Cataract surgery 300814 0
Condition category
Condition code
Eye 300636 300636 0 0
Diseases / disorders of the eye

Study type
Patient registry
Target follow-up duration
Target follow-up type
Description of intervention(s) / exposure
All the investigations involved in this study are non-invasive and non-contact procedures that are routinely used in clinical ophthalmology.

The first part of the study comparative diagnostic trial to compare clinical aberrometers. Participants will be examined on 4 different types of aberrometers (as described below) at a single half an hour long visit This part will commence in the first instance, approximately a month before the first cataract patient is assessed.

The second is non randomized observational trial to examine changes in corneal curvature associated with ocular accommodation assessed with corneal tomography and aberrometry and the relative influence of corneal biomechanics. Healthy participants will undergo corneal tomography and aberrometry, (Galilei 2 and Orbscan) and corneal biomehanics (Corvis-ST), as described below. The assessments will only take up to half an hour at a single visit. The second part will run concurrently with the third part of the study.

The final and arguably the most important part, is observational cohort study to characterise the relationship between corneal incision architecture and corneal biomechanics on two different incision sizes of surgically induced astigmatism following cataract surgery, using clinical aberrometry, corneal accommodation using tomography and corneal biomechanics. In this part, all the patients will be assessed at least a few hours once before the surgery, and 3 times after the surgery, which is standard of care for patients after cataract surgery. Assessments only take about 30 additional minutes more than their regular follow-up visit.

Visual acuity: Vision will be assessed using a letter chart. This is done as a standard of care for all the patients undergoing cataract surgery.

Slit-lamp biomicroscopy: Standard eye examination will be performed using a special microscope called a slit-lamp, which is used in every eye clinic room.

Aberrometry and tomography: The curvature of the front part of eye will be measured using special instruments known as the Orbscan II, Zywave, OPDIII, iDesign and Galilei 2 (only Galilei 2 for the third part). The instruments are used to assess the shape, refractive properties and thickness of cornea.

Biomechanical properties of cornea: The biomechanics (rigidity and flexibility) of the front part of your eye will be measured with a special instrument called Corvis-ST. This instrument also uses a gentle air puff for measurement. It does not cause any discomfort or pain to the eyes.

Optical Coherence Tomography: The instrument produces high resolution images the front of the eye with a special laser camera called anterior segment - Optical Coherence Tomographer (AS-OCT).

Specular microscopy: This technique is used to evaluate the health of corneal endothelium. The endothelial cell density will be quantified after obtaining clinical images.

Intervention code [1] 296301 0
Diagnosis / Prognosis
Comparator / control treatment
No control group
Control group

Primary outcome [1] 300047 0
Relationship between biomechanics of the cornea, using Corvis-ST, and surgically induced astigmatism, using tomographer (Galilei 2), following cataract surgery.

Timepoint [1] 300047 0
Patients will be assessed at least a few hours before surgery, and, one day, one month and three months after the surgery.
Primary outcome [2] 300076 0
Relationship between biomechanics of the cornea and wound architecture following cataract surgery. Biomechanics of the cornea will be measured by Corvis-ST and wound architecture by anterior segment optical coherence tomographer (AS-OCT) and Specular microscopy.

Timepoint [2] 300076 0
Patients will be assessed at least a few hours before surgery, and, one day, one month and three months after surgery.
Secondary outcome [1] 328919 0
Topographical maps and corneal higher order aberrations obtained by 4 different aberrometers (Zywave, OPDIII, iTrace and Galilei 2) will be compared. This is a composite secondary outcome.
Timepoint [1] 328919 0
This is the first part of the study. Three months from the commencement of the project.

Key inclusion criteria
Part 1 and 2: Ametropia <1D (defocus or astigmatism). Participants can be healthy volunteers.
Part 3: Patients scheduled for routine cataract surgery.
Minimum age
18 Years
Maximum age
No limit
Both males and females
Can healthy volunteers participate?
Key exclusion criteria
Part 1: Ametropia >1D (defocus or astigmatism)
Part 1, 2 and 3: Pre-existing ocular pathology or previous ocular surgery, Contact lens use,
Strabismus, Previous ocular trauma

Study design
Statistical methods / analysis
All statistical analysis will be completed using the R statistical software package and Microsoft Excel.
Part 1: The difference in total and individual HOA will be investigated using basic plots to visualise the raw data, investigate outliers and the spread of the data. Analysis of variance (ANOVA) and multivariate analysis of variance (MANOVA) and canonical discriminat analysis will be used to compare HOA with post hoc tests where required. Non-normal data will be analysed using non-parametric tests.
Part 2: Statistical analysis will include analysis as described for Part 1 in addition to correlation and regression analysis to investigate the relationship between Corvis-ST data and accommodation induced corneal tomographic changes.
Part 3: Surgically induced astigmatism (SAI) will be calculated for all patients based on pre and post-operative tomography data using vector analysis. The relationship between SIA magnitude, corneal biomechanics, and corneal wound architecture will be modelled using regression analysis.

Recruitment status
Active, not recruiting
Date of first participant enrolment
Date of last participant enrolment
Date of last data collection
Sample size
Accrual to date
Recruitment outside Australia
Country [1] 8366 0
New Zealand
State/province [1] 8366 0

Funding & Sponsors
Funding source category [1] 294862 0
Name [1] 294862 0
The University of Auckland
Address [1] 294862 0
Department of Ophthalmology
New Zealand National Eye Centre
Faculty of Medical and Health Sciences
The University of Auckland,
Private Bag 92019
Auckland 1142
Country [1] 294862 0
New Zealand
Primary sponsor type
The University of Auckland
Department of Ophthalmology
New Zealand National Eye Centre
Faculty of Medical and Health Sciences
The University of Auckland,
Private Bag 92019
Auckland 1142
New Zealand
Secondary sponsor category [1] 293702 0
Name [1] 293702 0
Address [1] 293702 0
Country [1] 293702 0

Ethics approval
Ethics application status
Ethics committee name [1] 296246 0
Health and Disability Ethics Committee
Ethics committee address [1] 296246 0
Health and Disability Ethics Committees
Ministry of Health
Freyberg Building
20 Aitken Street
PO Box 5013
Ethics committee country [1] 296246 0
New Zealand
Date submitted for ethics approval [1] 296246 0
Approval date [1] 296246 0
Ethics approval number [1] 296246 0
HDEC 16/CEN/132

Brief summary
Following removal of a cataract, an intraocular lens (IOL) is implanted during surgery to enable refractive correction of the eye to maximise vision following surgery. Selecting the correct model and refractive power of the IOL is critical to achieve the appropriate refractive target. A sub-optimally selected IOL will typically result in post-operative residual refractive error, and decreased unaided vision that may be associated with falls and decreased quality of life in many cases.

Refractive error is caused by the combined effect of the cornea and the lens and can be divided into lower order aberrations (LOA) and higher order aberrations (HOA).
To select an appropriate model IOL to minimise total spherical aberration and accurate assessment of corneal aberration is required prior to surgery. The first part of this study will compare four clinical aberrometers that use different optical principals to assess HOA in the eye.

Ocular accommodation is the process by which the crystalline lens adjusts the focus of the eye through conformational changes. A new strategy to accurately assess corneal curvature changes will be developed using 3D printed modifications to existing clinical tomographers and aberromters to allow corneal curvature assessment at near and distance fixation. Using this strategy even small changes in the corneal periphery should be quantifiable to definitively establish of the role of the cornea in accommodation. This is the second part of the project.

Cataract surgery typically involves small incisions placed in the peripheral cornea to extract the cataract using phacoemulsification, and to enable implantation of an intraocular lens following cataract removal. The size of the corneal incisions depends on the IOL that is selected and the lens cartridge that is required for insertion.

The final part of this study will aim to characterise the relative contribution of wound architecture and corneal biomechanics on surgically induced astigmatism.
Trial website
Trial related presentations / publications
Public notes

Principal investigator
Name 69358 0
Dr James McKelvie
Address 69358 0
Department of Ophthalmology
New Zealand National Eye Centre
Faculty of Medical and Health Sciences
The University of Auckland,
Private Bag 92019
Auckland 1142
Country 69358 0
New Zealand
Phone 69358 0
+64 9 923 6712
Fax 69358 0
Email 69358 0
Contact person for public queries
Name 69359 0
Dr James McKelvie
Address 69359 0
Department of Ophthalmology
New Zealand National Eye Centre
Faculty of Medical and Health Sciences
The University of Auckland,
Private Bag 92019
Auckland 1142
Country 69359 0
New Zealand
Phone 69359 0
+64 9 923 6712
Fax 69359 0
Email 69359 0
Contact person for scientific queries
Name 69360 0
Dr James McKelvie
Address 69360 0
Department of Ophthalmology
New Zealand National Eye Centre
Faculty of Medical and Health Sciences
The University of Auckland,
Private Bag 92019
Auckland 1142
Country 69360 0
New Zealand
Phone 69360 0
+64 9 923 6712
Fax 69360 0
Email 69360 0

No information has been provided regarding IPD availability
Summary results
Have study results been published in a peer-reviewed journal?
Other publications
Have study results been made publicly available in another format?
Results – basic reporting
Results – plain English summary