Study of Clinical Performance of Corneal Topography Measurement Using an Optical Biometer

Lenstar LS 900 Topography

Status

Completed

Phases

Unknown

Study type

Observational

Source

ClinicalTrials.gov

Registry ID

NCT01861925

Enrollment

Registered

2013-05-24

Start date

2013-06-30

Completion date

2013-07-31

Last updated

2014-06-05

For informational purposes only — not medical advice. Sourced from public registries and may not reflect the latest updates. Terms

Conditions

Corneal Topography

Brief summary

The purpose of this study is to quantify in-vivo repeatability of a new corneal topography measurement mode of an optical biometer, and the clinical performance of measurement in comparison to reference devices.

Interventions

None listed

Study design

Observational model

COHORT

Time perspective

PROSPECTIVE

Eligibility

Sex/Gender

ALL

Age

18 Years to No maximum

Healthy volunteers

Yes

Inclusion criteria

* 18 years or older

Exclusion criteria

* No corneal transplants * No corneal scar(s) * No acute infections of the eye * No weak fixation * No suspected lack of compliance * No vulnerable population

Design outcomes

Primary

Measure	Time frame	Description
In-vivo Repeatability of Corneal Topography Measurements With Lenstar LS 900 Topography: Sample Mean of Differences of Mean Power and Sample Mean of Std. Dev of Local Power Differences Between Two Consecutive Measurements	1 day of examination	Corneal topography is a measurement of the shape of the anterior cornea. The shape of a cornea can be fully quantified by providing a map of local power. Diopter is the unit of refractive power of a lens. In case of the cornea, the power K \[diopter\] is related to the radius (curvature) R \[mm\] of the best fitting sphere by the relation K=337.5/R. Here, corneal topography measurements are implemented by the Placido method, i.e. by analyzing the reflection image of a ring-shaped illumination. According to International Standards Organization (ISO) 19980-2012, repeatability of corneal topography is assessed on the central cornea: area with diameter d\<=3mm, and middle cornea: 3mm\<d\<=6mm. power difference (2 rep. meas.): sample mean and 95% C.I. of differences of spatial mean of corneal power between two consecutive measurements. power difference 2 std.dev.: sample mean of twice the deviation of local power differences (two consecutive measurements).

Secondary

Measure	Time frame	Description
Equivalence of Corneal Topography Measurement Between Lenstar LS 900 Topography and Atlas 9000: Sample Mean of Differences of Mean Power and Sample Mean of Std. Dev of Local Power Differences for One Measurement Per Device.	1 day of examination	For definition of corneal topography, corneal power in diopter, areas of evaluation and methods, see outcome 1. This outcome measure aims at testing the equivalence of corneal topography measurement between Lenstar LS 900 Topography (Haag Streit) and Atlas 9000 (Zeiss) by analyzing differences in measurement results for the same eye between both devices. power difference (2 devices) is the sample mean and 95% C.I. of differences of spatial mean of corneal power between two devices. This value quantifies systematic differences between devices (e.g. calibration), ignoring local variations of the power measurement. power difference (2 std.dev.) is the sample mean of twice the standard deviation of local power differences between measurements with both devices. This value quantifies the spatially resolved agreement of corneal shape measurement of the two devices.

Other

Measure	Time frame	Description
Equivalence of Corneal Topography Measurement Between Lenstar LS 900 Topography and Atlas 9000: Sample Mean of Std. Dev. of Local Corneal Elevation Differences for One Measurement Per Device.	1 day of examination	For definition of corneal topography, areas of evaluation and methods, see outcome 1 and 2. Corneal elevation refers to the distance between the measured corneal surface and the best fitting sphere, and is given in µm. This outcome measure aims at testing the equivalence of corneal topography measurement between Lenstar LS 900 Topography (Haag Streit) and Atlas 9000 (Zeiss) by analyzing differences in measurement results for the same eye between both devices. elevation difference (2 std. dev.) is the sample mean of twice the standard deviation of local corneal elevation differences between measurements with both devices. This value quantifies the spatially resolved agreement of corneal shape measurement of the two devices.
Equivalence of Keratometry Radius Measurement Between Lenstar LS 900 Topography and Lenstar LS 900: Population Mean of Differences of Keratometry Radius Measurement Between Both Devices.	1 day of examination	Keratometry radius refers to the corneal curvature R (see primary measure outcome). In this context, the cornea is approximated by a toric surface which can be characterized by a flat meridian (radius R1) and a steep meridian (radius R2) with an angle of 90 degrees between these meridians. This outcome measure aims at testing the equivalence of keratometry radius measurement between Lenstar LS 900 Topography and Lenstar LS 900 (both Haag Streit) by analyzing differences in measurement results for the same eye between both devices. Reported are: population mean of difference and 95% confidence interval of mean difference for radius of flat meridian (R1) and radius of steep meridian (R2).
Equivalence of Keratometry Axis Measurement Between Lenstar LS 900 Topography and Lenstar LS 900: Population Mean of Differences of Keratometry Axis Measurement Between Both Devices.	1 day of examination	Keratometry axis refers to the axis of the flat meridian of the toric representation of the cornea. For additional information see outcome 4. This outcome measure aims at testing the equivalence of keratometry axis measurement between Lenstar LS 900 Topography and Lenstar LS 900 (both Haag Streit) by analyzing differences in measurement results for the same eye between both devices. Reported are: population mean of difference and 95% confidence interval of mean difference for axis of flat meridian.

Countries

Switzerland

Participant flow

Participants by arm

Arm	Count
Normal Eye Astigmatism smaller than 1.5 diopters	34
Large Regular Astigmatism Astigmatism of \> 1.5 diopters, regular astigmatism.	8
Large Irregular Astigmatism Astigmatism of \> 1.5 diopters, irregular astigmatism.	8
Total	50

Baseline characteristics

Characteristic	Normal Eye	Large Regular Astigmatism	Large Irregular Astigmatism	Total
Age, Categorical <=18 years	0 Participants	0 Participants	0 Participants	0 Participants
Age, Categorical >=65 years	0 Participants	0 Participants	0 Participants	0 Participants
Age, Categorical Between 18 and 65 years	34 Participants	8 Participants	8 Participants	50 Participants
Age, Continuous	38.8 years STANDARD_DEVIATION 9.8	36.4 years STANDARD_DEVIATION 9	32.7 years STANDARD_DEVIATION 8.2	37.4 years STANDARD_DEVIATION 9.5
Region of Enrollment Switzerland	34 participants	8 participants	8 participants	50 participants
Sex: Female, Male Female	13 Participants	2 Participants	0 Participants	15 Participants
Sex: Female, Male Male	21 Participants	6 Participants	8 Participants	35 Participants

Adverse events

Event type	EG000 affected / at risk	EG001 affected / at risk	EG002 affected / at risk
deaths Total, all-cause mortality	— / —	— / —	— / —
other Total, other adverse events	0 / 34	0 / 8	0 / 8
serious Total, serious adverse events	0 / 34	0 / 8	0 / 8

Outcome results

Primary

In-vivo Repeatability of Corneal Topography Measurements With Lenstar LS 900 Topography: Sample Mean of Differences of Mean Power and Sample Mean of Std. Dev of Local Power Differences Between Two Consecutive Measurements

Corneal topography is a measurement of the shape of the anterior cornea. The shape of a cornea can be fully quantified by providing a map of local power. Diopter is the unit of refractive power of a lens. In case of the cornea, the power K \[diopter\] is related to the radius (curvature) R \[mm\] of the best fitting sphere by the relation K=337.5/R. Here, corneal topography measurements are implemented by the Placido method, i.e. by analyzing the reflection image of a ring-shaped illumination. According to International Standards Organization (ISO) 19980-2012, repeatability of corneal topography is assessed on the central cornea: area with diameter d\<=3mm, and middle cornea: 3mm\<d\<=6mm. power difference (2 rep. meas.): sample mean and 95% C.I. of differences of spatial mean of corneal power between two consecutive measurements. power difference 2 std.dev.: sample mean of twice the deviation of local power differences (two consecutive measurements).