Cause of Device-Related Incident
Support system failures; User errors

Clinical Specialty or Hospital Department
Ophthalmology; OR / Surgery

Device Factors
*Not stated

Document Type
Hazard Reports

External Factors
*Not stated

Mechanism of Injury or Death
Blindness

Support System Failures
Failure to train and / or credential

Tampering and/or Sabotage
*Not stated

User Errors
Failure to read label; Incorrect clinical use

UMDNS
Microscopes, Operating [12-539]

Operating Microscopes in Ophthalmic Surgery



Hazard [Health Devices May 1988;17(5):168-9]

Problem

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 surgery.(1)

Discussion

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 microscope systems.

Recommendations

  1. 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.
  2. 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.
  3. Always use protective corneal covers except when full visualization of the anterior chamber is necessary, and keep the eye properly irrigated at all times.
  4. 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.

Note

  1. Missing heat filter triggers suit. Malpractice Rep 1985;(Jun):10.

UMDNS Term

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

Blindness


[Home]    [About]    [Help]    [Site Map]
Copyright © 2017 ECRI
All rights reserved
www.ecri.org