Medical technology advances at an increasingly rapid pace, and ophthalmology has benefited greatly from this progress. We rely on wonderful diagnostic and therapeutic devices every day to help us treat our patients. As ophthalmologists, we probably have more “gadgets” than any of our colleagues in other specialties. Chief among these are imaging technologies, which represent an integral part of our field.
When I was in training, the imaging technology for ophthalmologists was essentially limited to basic photography, ultrasound, corneal topography, and specular microscopy. These modalities were primarily utilized by retina specialists (fundus photos, fluorescein angiograms, and B-scan images), oculoplastic surgeons (pre-op and post-op eyelid/adnexae images), cataract surgeons (A-scan biometry), and cornea/refractive surgeons (corneal topography and specular microscopy). We also used radiologic studies (x-ray, CT, and MRI) for trauma and neuro-ophthalmic indications.
Over the past two decades, we have witnessed an increase in the number and types of imaging technologies. The technology that truly revolutionized ophthalmic imaging was optical coherence tomography (OCT). Initially, OCT was a specialized test in academic centers to study macular and optic nerve structural changes. Now it is a ubiquitous device in just about every ophthalmology office.
There have also been dramatic improvements in other anterior and posterior segment imaging instruments. Current trends include combination devices (various technologies in one device) with smaller footprints, improved user friendliness, and better connectivity. Here is a brief update on some of these products:
Corneal Analysis Systems
In addition to traditional Placido disc technology, there are now many more options such as Scheimpflug imaging, ray-tracing, and wavefront aberrometry devices. Besides measuring corneal curvature values, modern devices are multifunctional, providing numerous other information like refraction, pupil size, angle kappa, angle alpha, higher-order aberrations, corneal pachymetry, anterior chamber depth, lens density and thickness, external photography, and tear layer imaging.
Some of the newest machines are:
- ATLAS™ 9000 from Zeiss: a Placido disc unit that produces standard maps, identifies abnormal topographies, and aids in contact lens fitting.
- Keratograph® 5M from Oculus: a combined keratometer and camera for evaluation of Meibomian glands and tear film.
- Pentacam® from Oculus: a Scheimpflug camera that provides information about the entire anterior segment.
- iTrace™ Visual Function Analyzer from Tracey Technologies: a ray tracing technology that integrates wavefront aberrometry and corneal topography.
- Galilei™ G2 from Ziemer: a combined Scheimpflug imaging and placido 3D imaging system.
- OPD-Scan III from Nidek: a multifunction corneal analyzer.
Many adapters and handheld devices can now be used to obtain high resolution images of the eye.
Examples include the iNview™ and Pictor Plus from Volk, iExaminer from Welch Allyn, and Mobile Terry i-Slit Lamp™ from EyePhotoDoc.
Many are now easier to use, automatic, non-mydriatic, and can also capture anterior segment photos.
The TRC NW400 from Topcon is a traditional fundus camera, while the EIDON from CenterVue uses confocal scanning technology.
Spectral-domain OCT has replaced the original time-domain technology, and now some products have fluorescein angiography (OCTA) capability as well.
Current devices include:
- Cirrus™ HD-OCT 5000 from Zeiss: a posterior segment OCT, which can be ordered with extras such as the Anterior Segment Premier Module (replaces the anterior segment Visante OCT unit) or the Cirrus photo (a mydriatic/non-mydriatic fundus camera).
- Spectralis® from Heidelberg Engineering: a device combining SD-OCT with confocal scanning laser ophthalmoscopy (cSLO), which also comes with the option of the Anterior Segment Module for imaging the cornea, sclera, and anterior chamber angle.
- RTVue® Premier from Optovue: another SD-OCT that performs both anterior and posterior segment imaging. Optovue also manufactures the AngioVue, which is an OCTA system.
The IOLMaster® 700 from Zeiss with SWEPT source OCT and the LENSTAR LS 900® from Haag-Streit are the newest generation devices for optical biometry. Both of them capture numerous measurements of ocular dimensions necessary for planning cataract surgery.
The newer ultrasound devices are also evolving towards more compact, portable units and combining various applications (i.e., A-scan, B- scan, UBM, and pachymetry) by including multiple probes:
- Eye Cubed™ from Ellex: a triple function device containing A-scan, B-scan, and UBM modalities.
- VuMAX™ from SonomedEscalon: an integrated A-scan, B-scan, and UBM device.
- Aviso™ from Quantel: another A-scan, B-scan, and UBM instrument.
- US-4000 from Nidek: a combination unit with B-scan, biometry, and pachymetry functions.