Optical coherence tomography (OCT)
Harmless light waves take cross-section pictures of the retina, a little like an ultrasound scan but with light instead of sound.
Surgical and diagnostic technology
All of the technology on this page is used by and available to Dr Chen at Vision Eye Institute Chatswood. These advanced, state-of-the-art imaging, laser and surgical systems support his cataract and retinal care. Each has a specific job: to measure the eye accurately, to see the retina in detail, or to make surgery more controlled.
What technology does Dr Chen use to examine the retina?
Dr Chen’s clinic uses ultra-widefield retinal imaging, optical coherence tomography (OCT), OCT angiography (OCTA), ultrasound and visual field testing. Together they show the whole retina, its layers and its blood vessels.
Ultra-widefield retinal imaging (Optos)
Photographs most of the retina in one image, including the far edge where tears and detachments often begin.
- Autofluorescence shows stress in the retina’s supporting cells and helps track geographic atrophy and inherited retinal conditions.
- Fluorescein angiography shows how blood flows through the retina.
OCT angiography (OCTA)
The same scanner maps the retina’s small blood vessels without an injection of dye, which helps with macular degeneration and vein occlusions.
Ultrasound (B-scan)
Looks inside the eye when bleeding or a dense cataract blocks the view, to check whether the retina is attached.
Visual field testing
Measures side vision when glaucoma or another condition may also be affecting the eye.
How is the eye measured before cataract or lens surgery?
Your eye is measured with optical biometry, several methods of corneal mapping and specular microscopy, so the lens power and surgical plan rest on cross-checked measurements. Some eyes also need anterior segment OCT or a retinal acuity meter test.
- Cornea
- Natural lens
- Retina
- Optic nerve
Optical biometry (ZEISS IOLMaster 700)
Measures the length and shape of the eye to calculate the power of the lens implant. Its swept-source OCT can measure through dense cataracts, and it shows an image of the centre of the retina to confirm you were looking straight at the target. It also measures the back surface of the cornea, which improves astigmatism planning.
- What it measures: the length of the eye, the curvature of the front and back of the cornea, the depth of the front chamber, the thickness of the natural lens and the width of the cornea.
- What you do: rest your chin on the chin rest and look at a small light for a few seconds. Nothing touches the eye.
- Why it matters: a 1 mm difference in the length of the eye changes the lens power needed by roughly 2.5 to 3 dioptres, so small measuring errors matter.
Corneal mapping: topography, tomography and aberrometry
The cornea provides about two-thirds of the eye’s focusing power, so its shape is mapped with more than one method and the results are compared with the biometry.
- Placido-disc corneal topography: reads the reflection of illuminated rings from the front of the cornea to map its shape. It also checks the tear film, which must be healthy for accurate measurements.
- Scheimpflug corneal tomography: a rotating camera images the cornea in three dimensions, front and back, and measures its thickness. It helps detect keratoconus and plan surgery after laser eye surgery.
- Topography with wavefront aberrometry: available for selected eyes. It measures how light is distorted through the whole eye, separating the cornea from the inside of the eye, and measures pupil size in different lighting.
If the maps disagree, or the tear film is unstable, the measurements are repeated, sometimes after a course of lubricating drops. How dry eye affects cataract measurements →
Specular microscopy
A specular microscope photographs the single layer of cells lining the back of the cornea, the endothelium. These cells pump fluid out of the cornea to keep it clear. They do not regrow, and some are lost during any eye operation, so their health matters before complex or combined surgery.
What does a specular microscopy printout show?
- A photograph of the cells: a mosaic of mostly six-sided cells, like the image shown here.
- Cell density: the number of cells in each square millimetre. Healthy adult corneas commonly have around 2,000 to 3,000, and the number falls slowly with age.
- Cell size and shape: how much the cells vary in size, and the proportion that are six-sided. Even, regular cells suggest a healthy layer.
- Corneal thickness: which increases when the endothelium struggles to keep the cornea clear.
It is used for eyes with Fuchs’ endothelial dystrophy, previous eye surgery or injury, and before combined or complex surgery.
CorneaFront chamberIrisDrainage angleAnterior segment OCT (AS-OCT)
Optical coherence tomography of the front of the eye. Like a retinal OCT, it uses harmless light to take a cross-section picture, but of the cornea, the front chamber, the iris and the lens.
What does an anterior segment OCT scan show?
- The cornea: its thickness across its whole width, and any scarring or irregularity.
- The front chamber: the depth of the space between the cornea and the iris.
- The drainage angle: whether the angle where the iris meets the cornea is open or narrow.
- Lens implants: the position of an existing lens implant or a piggyback lens, and the space behind the iris where some lenses sit.
It is used for selected eyes, for example before a lens exchange or piggyback lens, or when the drainage angle is narrow. It is not needed routinely before cataract surgery.
Retinal acuity meter
Estimates how well the retina could see once a cataract is removed. The meter directs a narrow beam carrying a small letter chart through the clearest part of the lens, so the letters reach the retina with less blur from the cataract.
- What you do: look into the instrument in a darkened room and read the smallest letters you can. The test takes a few minutes.
- When it helps: when a cataract and a retinal condition, such as macular degeneration or an epiretinal membrane, occur together and it is unclear how much each is affecting your sight.
- Its limits: the result is an estimate. It can underestimate vision through a very dense cataract and overestimate it in some macular conditions.
How are the measurements turned into a surgical plan?
Dr Chen uses ZEISS FORUM to bring the measurements from the clinic’s instruments into one secure record, and ZEISS EQ Workplace to plan cataract surgery. The measurements travel electronically from the IOLMaster 700 to the planning software and on to the operating microscope, instead of being copied by hand.
ZEISS FORUM
FORUM is the clinic’s ophthalmic data management system. Scans and measurements from the diagnostic instruments are stored centrally in your record, so Dr Chen can review them side by side, compare them with earlier visits and check that they agree.
ZEISS EQ Workplace
EQ Workplace is cataract surgery planning software built on FORUM. It imports your IOLMaster 700 measurements automatically, including total keratometry, which accounts for the back surface of the cornea. Dr Chen uses it to compare lens calculation formulas, choose the lens power and, for a toric lens, plan the axis. The finished plan, with the incision positions, the capsule opening and the toric axis, is sent to the ZEISS CALLISTO eye system in the operating microscope.
Step 1
Measure
The IOLMaster 700 measures your eye.
Step 2
Store
The results go straight into FORUM, beside your other scans.
Step 3
Plan
EQ Workplace calculates the lens power and plans the operation.
Step 4
Guide
The plan appears in the operating microscope through CALLISTO eye.
Why does electronic transfer reduce the risk of error?
Choosing a lens implant involves many numbers: the measurements, the lens constants, the calculated power and the axis of a toric lens. When numbers are copied by hand from a printout into a calculator, a record or a theatre list, each copy is a chance for a typing or reading mistake. Reviews of incidents in which the wrong lens was implanted in England and Wales found that transcription and documentation errors were among the most common contributing factors.
Studies of digital cataract workflows show that they reduce the number of times data must be copied. Fewer manual steps mean fewer opportunities for error. Technology does not replace checking: Dr Chen personally checks every lens calculation for every patient he operates on, and the lens is confirmed again in the operating theatre before it is implanted.
Sources
- Kelly and Jalil: wrong intraocular lens implant, learning from reported patient safety incidents, Eye, 2011
- Steeples and colleagues: wrong intraocular lens events, incidents reported 2010–2014, Eye, 2016
- Healthcare Safety Investigation Branch: insertion of an incorrect intraocular lens, 2018
- Shetty and colleagues: digital cataract workflow, time and motion study, Journal of Cataract and Refractive Surgery, 2024
- Amaral and colleagues: digital versus manual workflows for cataract surgery, systematic review, 2025
How does Dr Chen make lens calculations as accurate as possible?
Lens power is calculated with latest-generation formulas from several independent measurements, then checked by an experienced, dedicated team in every case, routine or complex.
Step 1
Measure
Several instruments measure the eye independently, so any result that does not fit can be spotted and repeated.
Step 2
Calculate
Lens power is calculated with latest-generation formulas, including specialised methods for eyes that have had previous surgery.
Step 3
Check
Vision Eye Institute is a long-established cataract and refractive surgery practice, and its team has decades of combined experience in lens calculations. Dr Chen personally checks every calculation for every patient he operates on.
Which eyes need extra care with lens calculations?
- Previous LASIK, PRK or other laser vision correction
- Previous radial keratotomy
- Keratoconus and other irregular corneas
- Very high short-sightedness
- Very high long-sightedness
- Intraocular lens exchange
Which lasers are used in Dr Chen’s clinic?
Dr Chen’s clinic has a pattern scanning retinal laser, a YAG laser and a selective laser trabeculoplasty (SLT) laser.
Pattern scanning retinal laser
Delivers short pulses in patterns rather than single spots. Treatment is quicker and usually more comfortable than older single-spot laser, with less spread of heat into surrounding tissue.
YAG laser
Clears cloudiness behind a lens implant, makes a small drainage opening in the iris when needed, and is used for YAG laser vitreolysis in selected floaters.
Selective laser trabeculoplasty (SLT)
Lowers eye pressure in open-angle glaucoma.
What is laser treatment in the clinic like?
Clinic lasers are used at a slit lamp. After numbing drops, a special contact lens is usually placed on the eye to focus the laser, and treatment takes a few minutes. Most people go home straight afterwards.
- YAG laser after cataract surgery: the thin capsule behind a lens implant can become cloudy months or years later. The YAG laser makes a small opening in it, and vision usually clears within a day or so.
- Selective laser trabeculoplasty: low-energy pulses treat the eye’s drainage meshwork to help fluid leave the eye and lower the pressure.
- Pattern scanning retinal laser: seals retinal tears and treats leaking or poorly supplied retina, for example after a retinal vein occlusion.
What technology is used during cataract surgery?
Cataract surgery in Dr Chen’s day surgery uses ZEISS CALLISTO eye digital guidance, the Alcon UNITY Vitreoretinal Cataract System (VCS), a femtosecond laser for selected patients and a high-resolution operating microscope.
- Iris
- Cataract, seen through the pupil
- Capsule opening guide, 5.0 mm
- Toric lens axis, 20°
- Incision guide
Digital guidance (ZEISS CALLISTO eye)
A reference image of your eye is taken when it is measured. In theatre, the system recognises your eye and overlays guides in the microscope: where to place the incisions, the size and position of the capsule opening, and the exact alignment of a toric lens. No ink marks are needed.
Alcon UNITY Vitreoretinal Cataract System (VCS)
The system that removes the cataract.
- Intelligent Fluidics measures pressure and flow in the eye continuously and adjusts in real time.
- Intelligent Sentry senses sudden changes in flow and responds within moments to keep the front of the eye stable.
- 4D phaco uses a gentle multi-directional ultrasound movement to break up the cataract efficiently.
- Thermal Sentry monitors heat at the incision and adjusts the ultrasound to protect the cornea.
Femtosecond laser
For selected patients, a laser creates the incisions and a round capsule opening and softens the cataract before it is removed.
Femtosecond laser cataract surgeryOperating microscope
A high-resolution surgical microscope with coaxial illumination gives a bright, stable red reflex, the orange glow that shows the lens capsule clearly.
What technology is used during retinal surgery?
Retinal surgery (vitrectomy) uses the Alcon UNITY Vitreoretinal Cataract System (VCS) with a cutter that works at up to 30,000 cuts per minute, stitchless 23, 25 or 27 gauge instruments, ZEISS RESIGHT wide-angle viewing and laser, freezing, dye and gas or oil treatments inside the eye.
1. Vitrectomy probe2. Floaters3. Light pipe4. Retina5. Infusion line
Alcon UNITY Vitreoretinal Cataract System (VCS)
Dr Chen’s vitrectomy platform. Its HyperVit cutter works at up to 30,000 cuts per minute. Faster cutting means each cut takes a smaller bite of the vitreous gel, which is designed to reduce pulling on the retina. The system controls pressure inside the eye throughout, and the same system is used for cataract surgery.
Small-gauge, stitchless surgery
Instruments pass through tiny self-sealing openings of 23, 25 or 27 gauge, about 0.6 to 0.4 mm across. Stitches are rarely needed.
Wide-angle viewing (ZEISS RESIGHT)
Lets Dr Chen see to the far edge of the retina during surgery, where tears are found and treated.
How is the retina treated during surgery?
Curved and illuminated laser probes seal retinal tears. Diathermy controls bleeding. Freezing treatment (cryotherapy) and a head-mounted laser treat tears far forward.
Dyes, heavy liquids, gas and oil
A specialised dual dye makes fine membranes visible for peeling. Heavy liquids, gas and silicone oil flatten and support the retina.
Gas and oil after vitrectomyWhat options are there for complex lens problems?
Dr Chen can offer any intraocular lens commercially available in Australia, piggyback lenses, custom-made high-, low- and negative-power lenses, and specialised instruments for lens exchange and scleral fixation.
Every lens available in Australia
Dr Chen is not tied to any single manufacturer, so the advice is tailored to your eye.
Lens choicesPiggyback and custom lenses
Piggyback lenses such as the Sulcoflex and 1stQ AddOn can sit in front of an existing implant. Custom-made lenses suit eyes outside the standard range: high-power lenses for very long-sighted eyes, and low-power or negative-power lenses for very high short-sightedness (myopia). Dr Chen has extensive experience in cataract surgery for very short-sighted eyes and regularly uses custom-made lenses made to each patient’s measurements.
Lens exchange and fixation
Specialised microsurgical forceps handle and remove lens implants. Dedicated equipment supports the stitchless Yamane technique and sutured scleral fixation.
IOL exchange and complex cataractWhy is it useful that the clinic and day surgery share a building?
Dr Chen’s clinic (level 3) and the day surgery (level 4) share one building, so assessment, surgery and follow-up happen in one place, and urgent surgery can sometimes happen very soon after assessment.
- Level 4: operating theatre
- Level 4: recovery area
- Lift
- Level 3: consultation
- Level 3: scans and measurements
- Level 3: waiting area
- Quicker access to surgery when it is urgentFor some urgent problems, such as certain retinal detachments, Dr Chen may be able to operate soon after your assessment, occasionally on the same day. This depends on theatre, anaesthetic and nursing availability, so it cannot be guaranteed, but being in the same building makes it possible more often.
- One place for your whole journeyConsultations, scans, surgery and follow-up visits happen at the same address.
- Your information stays togetherThe measurements used to plan your operation are taken by the same team, in the same building, as the surgery.
- Simpler arrangementsOne team coordinates your clinic appointments and your surgery booking.
- Easier for family and carersOne familiar place to drop you off and collect you. Chatswood station is a short walk away, with parking across the road at Chatswood Chase.
- Prompt review if something worries youDr Chen works one floor away, so a concern after surgery can be reviewed quickly.
- Familiar surroundingsMany people find surgery less daunting in a place, and with a team, they already know.
Dr Chen also operates at Chatswood Private Hospital.
Common questions about the technology
Is all of this technology available in Dr Chen’s practice?
Yes. All of the technology on this page is used by and available to Dr Chen at Vision Eye Institute Chatswood.
What does OCT stand for?
OCT stands for optical coherence tomography. It uses harmless light waves to take detailed cross-section pictures of the retina, a little like an ultrasound scan but with light instead of sound. OCT angiography (OCTA) uses the same scanner to map the retina’s small blood vessels without an injection of dye.
What is the Alcon UNITY VCS?
The Alcon UNITY Vitreoretinal Cataract System (VCS) is the surgical system Dr Chen uses for both cataract and retinal surgery. It controls pressure inside the eye in real time, and its vitreous cutter works at up to 30,000 cuts per minute.
Can surgery happen on the same day as my assessment?
Sometimes, for urgent problems such as certain retinal detachments. The clinic and day surgery are in the same building, but same-day surgery depends on theatre, anaesthetic and nursing availability and cannot be guaranteed.
Does advanced technology guarantee a better result?
No. Good equipment supports careful surgery, but results depend on the eye, the condition and surgical judgement. Dr Chen will explain what is realistic for your eye.
What are ZEISS FORUM and EQ Workplace?
ZEISS FORUM is the clinic’s ophthalmic data management system, which stores scans and measurements from the diagnostic instruments in one record. ZEISS EQ Workplace is cataract surgery planning software built on FORUM. It imports the IOLMaster 700 measurements automatically, helps calculate the lens power and plan a toric lens axis, and sends the plan to the operating microscope, so numbers do not need to be copied by hand. Dr Chen personally checks every lens calculation for every patient he operates on.
What does a specular microscopy test show?
Specular microscopy photographs the cells lining the back of the cornea. The printout shows the cell density, how much the cells vary in size and shape, and the thickness of the cornea. These cells keep the cornea clear and do not regrow, so their health matters before complex or combined surgery.
Where can I read more about this equipment?
The manufacturers publish technical information for readers who want more detail. Dr Chen will explain which of these are relevant to your eye at your consultation.
How do I make an appointment with Dr Chen?
Appointments and enquiries are made through Vision Eye Institute Chatswood.
Level 3, 270 Victoria Avenue, Chatswood NSW 2067For new flashes, suddenly increased floaters, a shadow or curtain, or sudden loss of vision, see the urgent assessment advice.
For referrers
Optometrists, GPs and ophthalmologists can refer through Oculo or with the PDF referral form.
Vision Eye Institute confirms your appointment after you submit your request. The request form is not for emergencies. A referral is not strictly essential to request an appointment, but you need a valid one to claim a Medicare rebate for your consultation.