The Benefits of Using Laser Retinal Imaging

What Is Laser Retinal Imaging (OCT)?

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Optical Coherence Tomography or OCT is a modern imaging technique that eye health care professionals use to capture images of your retina. It works like a typical ultrasound device. Only that instead of sound, this technology uses light waves that reflect from the eye tissues. The pictures they get are of high resolution, making it one of the best imaging devices to date. The technology is so advanced that it can take cross-sectional images of the distinctive layers in the eye. These provide eye doctors with three-dimensional images to help with their diagnosis.
 

What to Expect During OCT

During an OCT exam, your eye doctor may use special eye drops to dilate your pupils. This will help widen your pupil, making it easier for them to inspect your retina. Then, they will ask you to sit in front of the OCT machine. You will use a headrest to keep motionless. Then, your doctor will calibrate this medical imaging instrument. They will ask you to look at a fixed point inside the OCT machine. Your doctor will ask you to stare at this light target to keep your eyes still. They will also ask you to avoid blinking for short periods as the machine takes images. The equipment will scan your eye for about five minutes or so without touching it. They will then receive the images.

An OCT exam is generally performed to evaluate various eye conditions, including:
 

Cancer

The presence of a dark spot behind your eye may indicate malignant growth in your retina.

Glaucoma

This disease, which causes optic nerve damage, may result in irreversible blindness. It currently has no cure. But with early detection and intervention, patients can stop or slow down its progression.

Macular Edema

This occurs when your retinal blood vessels leak, causing them to swell.
 

Vitreous Traction

As you age, your vitreous cortex may gradually detach from your retina. This can cause blurred vision.

Diabetic Retinopathy

This is a complication from diabetes, causing damage to the blood vessels of the retina.
 

Central Serous Retinopathy

This occurs when there’s fluid buildup behind the retina, causing partial retinal detachment.
 

Pre-Retinal Macular Fibrosis

This is a condition characterized by a thin membrane of scar-like tissue covering the macular surface.
 

Age-Related Macular Degeneration

This is a common condition that can blur your central vision. It’s common in older people.

Not every patient requires dilation. But if your doctor used the special eye drops, your eyes might become sensitive to light for a few hours following the test procedure.
 

Benefits of OCT

Laser retinal imaging lets your eye doctor detect signs of eye disease that couldn’t be seen before. An OCT test is non-invasive and painless. The results are also easy for your doctor to interpret. The images they obtain from an OCT exam can be stored on a computer and compared with other test scans.

Your medical insurance, not your vision insurance, may cover your OCT exam. This will depend on the reasons why you need that test and the terms of your insurance policy.

Find out more about laser retinal imaging & OCT testing, contact Lifetime Vision and Eye Care in Miami Gardens, FL at (305) 902-3320 to book your appointment.

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High quality ophthalmic care depends on the accurate assessment of ocular disease. Conventional direct ophthalmoscopy is used widely and provides good two dimensional views of the retina. However, the true nature of retinal disease is apparent only in three dimensions. In diabetic maculopathy, direct ophthalmoscopy can reveal retinal exudates, but the degree of macula oedema, which usually underlies the decision to treat by laser photocoagulation,1 is less clear. In glaucoma, the earliest damage can be seen as thinning of the retinal nerve fibre layer with increased cupping of the optic disc.2 These changes are best viewed stereoscopically. In both cases, disease of the retinal or optic nerve head will change the surface contour of the retina, either elevating or depressing the retinal surface by up to several hundred micrometres. Clearly, the objective quantification of these changes would be of immense benefit in diagnosing disease and monitoring disease progression and response to treatment.

Summary points

• In diseases such as diabetic maculopathy and glaucoma changes in retinal structure precede visual symptoms

• Earlier detection of these changes allows early intervention and improves the prognosis

• Scanning laser ophthalmoscopes provide rapidly acquired views of the retina that enable the detection of these early changes

• Clinical studies have shown the value of these devices in the diagnosis of glaucoma and diabetic maculopathy

• The costs of these devices is falling and serious consideration should be given to their introduction into hospital based eye services

Diagnosing and monitoring disease

Several studies have examined the ability of these devices to detect glaucoma13–15and diabetic macula oedema.16 The tomographic scanning laser ophthalmoscope has been shown to detect glaucoma with high sensitivity (over 80%) and specificity (over 95%).14 These impressive statistics have been achieved without expert ophthalmic assessment and are based on the computerised analysis of retinal structure by the scanning laser ophthalmoscope. These ophthalmoscopes may therefore have a role in detection of glaucoma in primary care.

This technology may also help detect progressive disease in patients who have already had glaucoma or diabetes diagnosed. The ability to detect structural change is an important advantage since these changes usually occur before the onset of clinically detectable visual deficits such as a reduction in visual acuity or loss of visual field. The delay between the structural and visual changes reflects the redundancy of neural components that is built into the visual system. Thus, in glaucoma, it has been estimated that up to 50% of the retinal ganglion cells at any particular location can be lost before a visual field defect is detectable using currently available clinical methods.17 Consequently, if we rely on tests of visual acuity or visual field, significant retinal damage may have already occurred by the time that disease is detected, leading to a poorer visual prognosis.

Early detection also gives clinicians greater flexibility in managing patients. In glaucoma, quantification of the rate of optic disc cupping allows clinicians to estimate the onset of serious visual field loss, which can help when discussing the timing and possible outcomes of treatment. In diabetic maculopathy it may help improve targeting of focal laser treatment. These factors are important since the diseases have mild symptoms in the early stages, and treatment in the form of eye drops, laser, or surgery can have a greater effect on a patient's quality of life than the disease itself.

The other major advantage of these imaging technologies is that they require little patient interaction. This contrasts with commonly used clinical tests such as automated perimetry, which can be arduous for some elderly patients. Furthermore, it is likely that fewer laser images will be needed than visual field tests to detect progression of disease since the noise in a scanning laser ophthalmoscope image is much less than that seen in perimetric tests.18,19 Finally, these devices provide important documentation of the retina and optic disc, which can be valuable when discussing the prognosis or considering the medicolegal aspects of a case.

Implementation of laser technology

The main barrier to the use of scanning laser ophthalmoscopes is that they are expensive. In addition to the initial capital costs, they require experienced staff to operate them and need specialist maintenance. Taking images can, in some cases, be trying for the patient. The eye needs to be relatively immobile while the image is taken and, although the process is rapid for a single image (1.6 seconds for the scanning laser tomograph), three images are usually required to generate a clinically useful topographic map of the retinal surface. Indeed, a recent report of scanning laser ophthalmoscopy in an unselected patient population showed that up to 19% of patients could not provide satisfactory images.20 Patients may also be anxious about the new technology since lasers are often portrayed as powerful agents of destruction; their use as diagnostic tools requires careful explanation.

Further evidence is required to justify the widespread clinical use of scanning laser ophthalmoscopes. Given that the role of the NHS is to deliver a uniform high standard of patient care, the evidence that scanning laser ophthalmoscopes help diagnose diseases such as glaucoma and diabetic maculopathy argues for their installation in most ophthalmic units. However, in many units in the United Kingdom the appearance of the optic disc and macula is still documented by hand, which provides a poor objective record of retinal disease. The introduction of simpler techniques such as stereoscopic optic disc photography, which uses existing fundus cameras, may therefore provide the best value for money since these images have been shown to be of value in distinguishing normal from glaucomatous eyes.21 Similarly, the institution of free eye tests for people aged over 60 is probably a more useful first step than the widespread introduction of scanning laser ophthalmoscopes.22 When so many basic steps have yet to be taken in clinical assessment it may be premature to consider the large scale introduction of such advanced imaging equipment.

Despite these caveats, scanning laser ophthalmoscopy holds great promise for the diagnosis of ophthalmic disease, and it is important that we research its clinical application. In considering the benefits of this technology, we must not conclude that the relentless accrual of data always leads to improvements in patient care. Most patients want to spend as little time in clinic as possible and to receive the minimum necessary investigation and treatment. That said, if detailed topographic images can be acquired rapidly and with minimal discomfort, the wishes of both patient and clinician will be met. The cost of these devices remains a difficult issue. However, as with other electronic devices, this is likely to fall greatly over the next decade as development costs are recouped and computing and electronic costs are reduced. If these developments continue, the widespread use of laser imaging technology in routine clinical practice seems likely.

Footnotes

Funding: Welsh Office of Research and Development

Competing interests: None declared.

Laser Retinal ImagingLaser Retinal Imaging (OCT) - Lifetime Vision and Eye Care

Using lasers to image the retina - PMC