B Optovue XR - Cam ITA
B Optovue XR - Cam ITA
B Optovue XR - Cam ITA
Model CAM
RTVue XR
Version 2014
Optovue Inc.
Fremont, CA 94538
USA
Phone : 510-623-8868
Fax: 510-623-8668
www.optovue.com
e-mail: info@optovue.com
Revision Control
Intended Use
The CAM, an auxiliary lens adapter, when used in conjunction with XR, is indicated
for in vivo imaging and measurement of the cornea and other ocular structures of the
anterior segment of the eye, including pachymetry and corneal power.
Product Compliance
European Conformity
European Representative
Warning: Phototoxicity
The CAM Option is an accessory only for the RTVue XR system and has no function
what-so-ever as an independent product. As such, the CAM option may not be used
independently of the RTVue XR system, and should be kept in the storage (wooden)
box when not in use.
There is no increase in the risk of phototoxicity from the RTVue XR system when used
in conjunction with the CAM option. Please refer to the RTVue XR Users Manual for
all Safety Notes pertaining to the use of the system.
XR/CAM is comprised of the XR system and the CAM option (cornea lens
adapter) for use in imaging the cornea and anterior chamber of the eye.
The lens adapter is attached and removed by a trained operator. The cornea
scan patterns and analysis functions are enabled only after the XR/CAM license
is purchased.
1. XR Scanner:
2. Computer:
3. System Table:
4. Monitor (Computer Display):
5. Keyboard and Mouse
6. Printer
7. Cornea lens adapter (CAM)
Cornea Illuminators
(red LED)
CAM-L
Pull the scanner head all the way back, align using the live IR
video image of the patient’s eye, then gradually move the
scanner head forward until OCT scan is in the target area.
This will coincide approximately with the patient’s iris coming
into focus in the live IR video image.
Select scan pattern from pop up list and mouse click to activate scan
acquisition (a list of scan patterns and specifications is provided in
section 9).
OCT scan window: Place the cornea B-scan image in between the two red
guide lines to optimize the cornea scan images. Pachymetry and cross line
scans will have two OCT windows, one for vertical b- scan, and one for
horizontal b- scan.
1. Pachymetry scan: Align the aiming circle (inner circle is 4mm diameter
and outer circle is 6mm diameter) to the center of the pupil.
2. Angle scan: Use the external fixation (yellow light on gooseneck cable) to
guide the patients fixation (of the fellow eye) until the cornea/sclera edge
is parallel and located in the red guided lines region. Place center of
scan line pattern on the limbus and cornea/scleral OCT image parallel to
the red horizontal guidelines.
3. line, cross line, 3-D cornea: these scans be centered on the pupil or
particular area of interest.
1. Shape change (like the bending of the straw): This is caused by the
cornea surface that is not perpendicular to the scan beam. This cannot
be avoided when scanning a length greater than 3mm of the cornea. If
you scan on a relative flat surface of cornea or sclera, the incident beam
is relatively perpendicular to the surface. In this instance the beam will
not be bent or warped. For example, if you make the straw perpendicular
to the water surface, the straw does not look bent or warped at the water
and air interface.
2. Distance Change: The straw looks thicker because the index of refraction
(n) of water is 1.33 times of the air (n=1.33). The cornea (n= 1.38) and
aqueous (n=1.34) are very similar but are at a higher index than that of
air. To make the physical distance measurement, the tissue thickness
needs to be divided by the index of refraction of the media.
A dewarp calculation is used on the cornea Line, Cross line and Pachymetry
scans to transfer the OCT image into a physical image of the cornea for both
shape and distance. For all other scans, the live scan image is placed within
the red dashed lines, so the incident beam is relatively perpendicular to the
tissue surface. A distance scale factor is only applied in the measurement
tool to get accurate distance and area measurements.
6.2 Measurement
Please refer to XR Users Manual
6.3.1 Line
On both Line & Cross line scans, if the image saved is an average processed image,
then both the averaged and single frame image will be saved.
Note:
The artifact in the image is from an interference signal caused by the strong
signal on both anterior and posterior cornea surface. The artifact is “fixed” at
the same location. To avoid or remove the artifact from your scan, use the
joystick to move the scan on the eye slightly up/down, left or right. (you may
also use the chinrest elevation control up/down switch for chin adjustment
down to avoid the artifact).
6.3.3 Angle
TISA (Trabecular Iris Surface Area) Measurement tool is used to measure the angle
area and AOD (angle open distance) in the anterior chamber angle. The number 500
or 750 is the distance (in microns) measured between the two upper points along the
posterior cornea surface. One of these two upper points shall be located on the
sclera spur and the other one on the posterior cornea surface 500 or 750µm away
from sclera spur. The AOD is the distance from cornea to iris. The area is measured
as the trapezoidal area encompassed by these four points.
6.3.4 3D Cornea
The Cornea 3D scan has scan density of 513 A-scans and 101 B-scans.
The pachymetry report is a comprehensive collection of maps, tables, and images that
provide qualitative and quantitative assessment of the cornea.
Cornea thickness results are presented as a color-coded map (6mm) and a color
scale provides reference values for colors. Thicker values are hot colors like red and
orange, while thinner values are cool colors like blue and black.
Individual B-scans are displayed in the presentation window above the map. Different
B-scans can be displayed by clicking on the thickness map (making it interactive) and
moving the cursor around slowly to the white lines (scan location indicators).
The Pachymetry analysis provides some key thickness parameters in the table to the
left of the Pachymetry report (note the values in the red circle above). It is suggested
in literature that a difference (delta) of 50 microns or more between the superior and
inferior sectors being compared is suspect.
Change Analysis results for Pachymetry, Cornea Power and Epithelial Map
The Corneal Power feature is available to customers who have purchased the
Corneal Power upgrade. For information on how to install and validate the cornea
power tool, please refer to installation manual.
Summary description
Corneal power is one of the key input parameters for IOL power calculation in cataract
surgery. In clinical practice, corneal power is commonly measured by manual or
automated keratometry or by simulated keratometry (Sim-K) from Placido-ring corneal
topographers. Corneal power provided by keratometry or topography is based on
measuring the anterior surface curvature of the cornea and assuming a fixed ratio of
3
0.883 between posterior and anterior curvature to compute the total corneal power.
Corneal power measurement with keratometer or topographer works well enough in
normal eyes, but the assumption of fixed ratio between anterior and posterior
curvature could lead to erroneous corneal power assessment in eyes with corneal
1,2,3
pathology or eyes with prior refractive surgery for obvious reasons. Therefore,
direct measurement of both anterior and posterior corneal curvatures to assess
corneal refractive power as implemented in XR CAM could be advantageous.
The XR CAM net corneal power is not clinically interchangeable with keratometric
corneal power measurements or Pentacam net corneal power measurement for IOL
Power calculation. In other words, the XR CAM corneal power measurements cannot
be directly applied in existing IOL power formulas developed based on measurements
provided by other devices, such as keratometer or Pentacam
XR corneal power scan is performed with CAM adaptor and with the “Pachymetry”
scan protocol which consists of 5 sets of pachymetry scan. Each set of pachymetry
scan consists of 8 evenly spaced meridian scans (6 mm in length each) centered on
the pupil.
The corneal curvature radii are derived based on best fit sphere to the central 3 mm
for anterior and posterior surfaces. The anterior and posterior corneal power is
calculated based on refractive indices of 1.376 for the cornea and 1.336 for the
aqueous. The net corneal power is calculated using a thick lens formula based on
anterior corneal power, posterior corneal power, taking into account the central
thickness of the cornea. See Appendix A for additional description.
When acquiring Corneal Power scan, the following steps should be observed.
Correct patient fixation and alignment centered on pupil are both critical to
produce consistent corneal power measurement.
Repeatability
The repeatability (standard deviation) of the corneal power scan with XR CAM is
summarized in the table below. The repeatability of corneal power parameters is
better than 0.25D for a single scan in the normal eye and the post-laser refractive
surgery eyes. For clinical use, it is recommended that a user takes at least 3 corneal
power scans and calculate mean corneal power to further reduce measurement
variability.
Pathological or
Post-Laser Refractive
Normal Post-Incisional
Surgery
Surgery
Net Corneal Power (D) 0.21 0.17 0.35
Anterior Corneal Power (n=1.3375) (D) 0.20 0.16 0.39
Posterior Corneal Power (D) 0.05 0.05 0.16
Anterior Radius of Curvature (mm) 0.034 0.030 0.064
Posterior Radius of Curvature (mm) 0.050 0.048 0.172
Central Corneal Thickness (µm) 2.1 1.9 3.8
Thinnest Corneal Thickness (µm) 3.8 1.3 18.0
Validation
To ensure system stability overtime, the corneal power software automatically
prompts for a weekly validation test. The validation test is performed with the corneal
power validation tool stored with the instrument. The result of the validation test is
compared with the stored value obtained during the initial corneal power calibration to
verify system stability. The limit of acceptable difference is ±0.25D; if exceeded, the
software will not allow acquisition of corneal power scan. A warning message is
displayed on screen with instructions for further actions. See Appendix A for
instructions to perform the Validation Test.
If the weekly validation test is not performed on schedule, the corneal power feature
will be automatically disabled and only pachymetry measurement will be produced. To
reactivate corneal power measurement, select the validation test and perform the test
according to instruction.
References:
There is a clinical need to measure epithelial cell layer separately from the
pachymetry of the cornea. The thickness distribution of the layer is useful in the
evaluation and follow up of patients for irregularities and/or changes due to
pathologies, contact lens, or refractive surgeries. Epithelium Thickness measures
the thickness from the epithelial cell surface to Bowman’s membrane. The Epithelium
Thickness Mapping feature is an upgrade to the pachymetry scan – a sample
pachymetry report with epithelium thickness mapping is shown below.
The scan report of epithelium thickness displays an Epithelium Map to the right of the
pachymetry scan. Note: the Epithelium Map uses a different color legend than that for
the Pachymetry Map. An Epithelium Thickness analysis is displayed underneath the
Pachymetry analysis as well.
1. Keep the Corneal Power Validation Tool in the wooden case provided
when not in use.
2. Routinely check the lens for dust, fingerprints, or smudges.
3. Use the same cleaning methods as is recommended in the XR User
manual to clean the front ocular lens of the XR.
B. Cornea Imager:
Monochrome CCD Camera: 811x 508 pixel 1/3” CCD Format
NIR Illumination: 735nm LED
C. Patient Interface:
Working distance:
CAM-L: 13 mm
D. Measurement Features:
Cornea Analysis:
- CAM-L:
i. Pachymetry map
1. Cornea thickness map
2. Flap/Stroma thickness Measurement
3. Pachymetry Assessment
4. Corneal Power Assessment
ii. Line: Flap/Stroma, Distance/Area measurement
iii. Cross line : Flap/Stroma, Distance, Area measurement
iv. Angle Scan (3mm scan length, 2.3mm depth)
1. AOD 500/750 measurement
2. TISA 500/750 measurement
3. Angle in degrees
This feature is a license controlled revenue product and payment for the license
is in advance only.
Please follow the activation instructions provided with the license key in the document
titled “Corneal Power License Key – Activation Instructions.”
1. Attach the CAM lens onto the RTVue XR machine and slip the calibration tool
on the end of the lens until it stops. Tighten the white lock nut as shown in
the figure below.
5. Click that the two images are between the red parallel lines. The 2 images
are in the X and Y axis planes.
6. Using the mouse, click and hold the target on the aiming screen and move the
aim LEFT or RIGHT to get a wide reflection on the image and to align the
center of the reflection to the center guideline on the X Axis plane.
7. Using the mouse, click and hold the target on the aiming screen and move the
aim UP or DOWN to get a wide reflection on the image and to align the center
of the reflection to the center guideline on the Y Axis plane.
12. Re-install the Validation tool over the CAM lens until it stops, tighten the white
lock screw and retry validation.
13. If error message continues to appear when attempting the Validation, the TCP
requires a re-installation. Contact your Optovue service department for
assistance.
The corneal power scan consists of 5 sets of pachymetry scans in rapid succession.
Each set of pachymetry scan consists of 8 meridian scans of 6mm in length centered
on the pupil.
As illustrated in the figure below, the anterior and posterior corneal curvature radii are
calculated from 8 meridian corneal cross-sectional images based on the central 3 mm
zone. The corneal anterior power ( K a ) and posterior power ( K p ) are calculated
based on the anterior radius ( Ra ) and the posterior radius ( Rp ) as follow:
n1 n0 n2 n1
Ka , Kp
Ra Rp
where n0 = 1, n1 = 1.376 and n2 = 1.336.
Occasionally, eyelid or eyelash artifact in meridians other than the vertical one (due to
blinking) could cause obvious artifact in the pachymetry map but no obvious impact on
CCPNet measurement quality.
Pupil blocked by eyelid in the video image and alignment cannot be assessed.
This feature is a license controlled revenue product and payment for the license
is in advance only.
Please follow the activation instructions provided with the license key in the document
titled “Epithelium Mapping License Key – Activation Instructions.”
The automatic algorithm measures epithelial thickness from corneal anterior surface
to the posterior boundary of the epithelia. The posterior boundary is defined as the
interface of epithelia and Bowman’s Layer. When the Bowman’s layer is absent as in
post-PRK eyes, the posterior boundary is defined as the interface of epithelia and the
corneal stroma. There is characteristic reflectivity change at the interfaces which is
utilized in the automatic algorithm for boundary detection. The automatic
segmentation of the corneal anterior and posterior boundaries and epithelial posterior
boundary and resulting corneal thickness map and epithelial thickness map are
illustrated with a post-LASIK eye and with a post-PRK eye as illustrated in the
following two images respectively. Because of the difference in the characteristics in
the epithelial posterior boundary in LASIK and PRK eyes, for this validation study, we
separated the post-laser refractive surgery eyes into LASIK group and PRK group in
the data analysis.
Check epithelial map for obvious segmentation error along the 8 meridian scan lines.
When segmentation error was noted, corresponding cross-sectional OCT image with
segmentation line overlay was reviewed for confirmation.
Examples of scans from the same eyes with successful segmentation and with
obvious segmentation error are shown in the figure below.
Pachymetry maps (Left) and epithelial maps (Right) of a 44 yrs. old KCN patient. The
st
epithelial segmentation was acceptable for the 1 scan (Top row) but failed in
nd
meridian 2 (M-2) in the 2 scan (Bottom row). The segmentation error is easily
recognized based on sharp color change along the scan lines.
Manual correction is quite feasible when the error is limited to a small number of
meridians, and could be helpful when imaging difficult eyes. As illustrated in the figure
below, the segmentation error in meridian 6 causing a visible artifact in the epithelial
map (Top row), and with manual correction of the segmentation error in meridian 6,
the artifact in the epithelial map is much reduced. Note that manual correction of the
posterior boundary of the epithelial layer didn’t affect the pachymetry map. If a scan
has segmentation error in multiple meridians, it is probably more efficient to retake the
scan instead of manually correcting each affected meridian.
Clinical validation of the software was performed based on the following study groups
Normal cornea with no contact lens wearing history (Normal)
Normal cornea with regular contact lens wearing history (CL)
Post-laser refractive surgery cornea (Post-LRS), which was further
separated into two sub groups in the analysis: post-LASIK group
(LASIK) and post-PRK group (PRK)
Keratoconus cornea (KCN)
While we do not expect the dry eye syndrome group to pose extra difficulty in the
epithelial thickness automatic measurement algorithm as compared to the KCN group
or the LASIK and PRK groups, the performance data for the dry eye syndrome
group has not been established and extra caution is recommended when using
the device for the measurement of the dry eye subject group.
12.4.1.2 CL
Subjects were recruited from staff volunteers, patients seeking refractive
surgery consultation, and patients seeking cataract surgery consultation
according to the following criteria
18 years of age or older
A regular contact lens wearer
No corneal pathology
No prior ocular surgery and no prior laser refractive surgery
12.4.1.3 LASIK
Subjects were recruited from the pool of post-LASIK patients according to the
following criteria
18 years of age or older
No corneal pathology
No prior ocular surgery except laser refractive surgery
At least 1 week post laser refractive surgery without complication
12.4.1.4 PRK
Subjects were recruited from the pool of post-PRK patients according to the
following criteria
18 years of age or older
No corneal pathology
No prior ocular surgery except laser refractive surgery
12.4.1.5 KCN
Subjects were recruited from the pool of patients with keratoconus diagnosis
according to the following criteria
18 years of age or older
Clinical diagnosis of keratoconus
No prior laser refractive surgery
The descriptive statistics for the epithelial thickness map derived parameters are
provided in the tables below.
Descriptive statistics for standard deviation of the epithelial map by study group.
For the automatic algorithm, the repeatability was assessed for the 6 measurement
parameters respectively.