Technology is used in ophthalmology in many ways. Some of the most interesting parts of this field are research and the development of new technology.
One of Edmund’s favorite parts about ophthalmology is the variety of imaging modalities they have. They can see things that we couldn’t before and characterize different eye diseases.
Axial Length Scanning
In ophthalmology, measuring axial length of the eye is a key technology used in measuring refractive state and for tracking changes in lens shape. The metric is also useful for monitoring treatment success in orthokeratology.
Axial length measurements can be obtained by either applanation or immersion ultrasound biometry. The immersion technique does not involve touching the cornea with an ultrasound probe, thereby eliminating variable corneal compression and enabling more accurate measurements.
However, this method is difficult for ophthalmic technicians to perform and requires more technical expertise than the contact method. Thus, it is not recommended for use by surgeons who do not have experience performing immersion measurements.
To assess the repeatability of axial biometry of the entire eye, we imaged 37 and 12 adult subjects using ultra-long scan depth optical coherence tomography (ultra-long scan depth-OCT) and the IOLMaster instrument (Carl Zeiss Meditec, Dublin, CA). Comparison of axial length measurements between ultra-long scan depth-OCT and IOLMaster showed good agreement with within-subject standard deviation 0.01 mm.
Retinal Imaging
Retinal imaging takes digital pictures of the back of your eye, showing your retina (where light and images hit), optic disk (a spot on the retina that holds the optic nerve, which sends information to the brain) and blood vessels. This helps your optometrist or ophthalmologist find certain diseases and check your eye health.
Retina imaging can help detect early signs of eye disease, including age-related macular degeneration, diabetic retinopathy, glaucoma, and retinal detachment. These conditions can be treated successfully if detected early and the damage does not progress to a more serious stage.
Retinal imaging is also used during a regular exam, where your doctor can compare the two views side by side. This allows them to see subtle changes and explain treatment more thoroughly.
Optic Nerve Head Analyzer
The Optic Nerve Head Analyzer is a technology used in ophthalmology to document optic nerve head morphology. It is particularly useful for assessing thinning of the retinal nerve fiber layer (RNFL) as this can be a sign of glaucomatous damage.
The OCT uses a pair of laser beams to measure RNFL thickness. The light beams are positioned at different locations on the retinal surface and when the path lengths of the two light beams coincide, this provides a measure of depth and reflectivity of the tissue.
It is an ideal tool for tracking disease progression since RNFL thinning can be a marker of glaucomatous damage. It can also be useful for evaluating the progress of optic neuropathies.
OCT
Optical Coherence Tomography (OCT) is a technology used in ophthalmology to produce cross-sectional images of tissue. It is most commonly used to measure retinal thickness and nerve fiber layer thickness, which can improve diagnosis of glaucoma, macula disease, diabetic retinopathy and other eye disorders.
OCT is based on a low-coherence interferometer and measures the echo time delay of reflected light. This measurement is very fast and can be done on a scale of less than 30 fsec (30 x 10-15 sec).
To detect the echo time delay of a reflected light beam, OCT utilizes a Michelson type interferometer that emits a light beam which is directed and scanned on the sample being imaged. The reflected or backscattering light is then correlated with a reference path.
As the reflected light travels through the sample, it interferes with the emitted light which is traveling a reference path. The interference signal is then detected by a photodiode. The resulting OCT signal is then converted into digital data by an analog-digital converter. The resulting digitized OCT signal is then reconstructed into an image.
