Operating Microscopes in Ophthalmic Surgery
Hazard [Health Devices May 1988;17(5):168-9]
Exposure to light from an operating microscope during extracapsular
cataract extraction (ECCE) and intraocular lens (IOL) implantation can result in photic
retinopathy (light-induced retinal damage), particularly in patients with existing retinal
impairment. ECRI investigated several incidents in which eye lesions occurred in patients
who underwent ECCE with IOL implantation. The shape and orientation of these lesions were
consistent with those that would be expected from retinal exposure to excessive light
intensity from a fiberoptic, focused delivery system. Contributing factors were prolonged
exposure and high illumination levels. In an unrelated series of incidents, 11 separate
lawsuits were filed in 1985 against a hospital in connection with eye injuries allegedly
resulting from use of an operating microscope with a missing heat filter for ophthalmic
Clear visualization of the operating field is essential for successful
surgery. To enhance the surgeon's view of microscopic structures (e.g., nerves, blood and
lymphatic vessels, lesions), magnification is necessary. An operating microscope is needed
for procedures in which the surgeon requires adjustable focusing capability and greater
stability than offered by a loupe.
When an operating microscope is used, light is transmitted from a lamp
housing into the microscope's body through prisms or fiberoptic cables and is transmitted
through the objective lens to the operating field, concentric to the field of view. The
light reflected from the operating field passes through the objective lens, the
magnification changer, and the eyepieces, where the surgeon sees the image of the
operating field. When the patient's eye is exposed to intense light (especially short-wave
or near-ultraviolet wavelengths) for extended periods, problems such as cystoid macular
edema and postprocedural vision blurring may result. Photic retinopathy should be
considered when vision blurring persists following ECCE. Such blurring usually clears up
in less than two months; however, in 1-2% of all ECCE patients it does not.
The complex interaction of the many factors that affect retinal light
exposure has prevented standards for exposure limits from being established. Although
illumination must provide a clear operating field of view for the surgeon, the intensity
of illumination on the operating field depends on the surgeon's own visual acuity and the
efficiency of the microscope to transmit reflected light back from the operating field.
The duration of illumination is also an important factor in retinal damage. Thus,
different surgeons and procedures will subject the eye to varying levels and durations of
exposure. Additional variable factors such as anesthesia, light and heat filters, and
corneal protective devices (e.g., eclipse filters, semiopaque contact lenses) must also be
taken into consideration.
The only recommendations that can be made are cautionary. Even when
precautions are taken and users are properly trained, retinal damage is a recognized risk.
Phototoxic retinal exposure can be reduced by limiting the overall level and time of
illumination, irrigating the eye frequently, and covering the central cornea with a
semiopaque contact lens or alternative method before lens extraction and during wound
closure. Side-beam illuminators and IR/UV and yellow light filters are recommended to
decrease light exposure levels. Most manufacturers offer these filters for their
- Alert all ophthalmic surgeons to this report and
keep them informed of the most recent changes in user instructions issued by
microscope manufacturers. Surgeons should be up to date on any microscope
system upgrades, additional safety features, changes in patient selection
protocol as outlined by the manufacturer, and procedural changes.
- Use the lowest light intensity setting at which
acceptable operating field visualization can be achieved. Consistent with
clinical needs, surgeons should not decrease the aperture for added depth of
field. The benefits of the added depth may be outweighed by the risks of the
additional light needed for field visualization.
- Always use protective corneal covers except when
full visualization of the anterior chamber is necessary, and keep the eye
properly irrigated at all times.
- We recommended the use of side-beam illuminators and safety filters to
reduce the risk of patient injury. Surgeons should be knowledgeable in their
proper use. Add a safety check to the presurgical checklist to be sure that
all such devices are installed and functional.
- Missing heat filter triggers suit. Malpractice Rep
Microscopes, Operating [12-539]
Cause of Device-Related Incident
User errors: Failure to read label; Incorrect clinical use
Support system failure: Failure to train and/or credential
Mechanism of Injury or Death