Patient Safety Bulletin Number 2

Patient Safety Bulletin Number 2: Minimizing Wrong IOL Placement

A Joint Statement of the American Academy of Ophthalmology , the American Society of Ophthalmic Registered Nurses and the American Association of Eye and Ear Hospitals

Purpose and Background for Patient Safety Bulletins

In 1999, The Institute of Medicine (IOM) of the National Academy of Sciences, issued its report, To Err is Human: Building a Safer Health System.¹ The report brought increased national focus to issues regarding patient safety, stimulating public and private initiatives to tackle underlying systematic errors in health care delivery. The IOM outlined five major goals: establish a national focus for leadership and knowledge, identify and learn from errors, pass legislation to protect a voluntary reporting system, set performance standards and expectations for safety, and implement safety systems in health care organizations.

In 1999, the National Patient Safety Foundation approved an Agenda for Research and Development in Patient Safety. The National Patient Safety Foundation’s agenda defines patient safety as " the avoidance, prevention and improvement of adverse outcomes or injuries stemming from the processes of health care. Safety emerges from the interaction of the system’s components; it does not reside in a person, device or department. Improving safety depends on learning how safety emerges from interactions of the components. Patient safety is a subset of health care quality."²

The American Academy of Ophthalmology, representing over 95% of practicing ophthalmologists in the United States, is committed to promoting high-quality eye care and its continuous improvement. The AAO supports the IOM’s goal to reduce medical errors and to improve safety of health care. The AAO also supports the National Patient Safety Foundation’s mission to improve health care safety by studying how errors occur and implementing safeguards. To cultivate a climate of learning about incidents and how to implement systems that will advance patient safety, the Academy is launching this small series of Patient Safety Bulletins to increase the visibility of patient safety and to inform ophthalmologists of systematic practices that can prevent errors from occurring.

The Academy is committed to improving patient care through its ongoing quality of care activities. These include the evidence-based development and dissemination of clinical practice guidelines, ophthalmic technology assessments, and complementary therapy assessments, collection of outcomes and performance measures, and development of a standard clinical reference terminology and digital imaging standards to improve access to timely and comprehensive information for medical decisionmaking. The American Society of Ophthalmic Registered Nurses (ASORN) and the American Association of Eye and Ear Hospitals (AAEEH) are collaborative partners with the Academy’s commitment to quality patient care and its ongoing quality of care activities. ASORN is a society of registered nurses whose mission is to foster excellence in ophthalmic patient care and to support the ophthalmic team through individual development, education, and evidence-based practice. AAEEH is composed of domestic and international institutions, which are dedicated to quality medicine, research, education and surgical excellence.

Wrong IOL Placement: Definition of the Problem

After cataract surgery, patients often expect excellent visual acuity without needing glasses. If the IOL implanted does not meet their visual acuity expectations, additional postoperative correction, possibly even a subsequent procedure to exchange the IOL, may be required. But, in reality, the patient often needs minimal eyeglass correction to obtain maximum visual acuity after eye surgery. Although rare in occurrence, one error that can occur is the insertion of an incorrect intraocular lens (IOL) in cataract surgery. The IOL can be the wrong power, wrong size or wrong type, which can lead to postoperative refractive errors and less satisfactory vision for the patient.³ The surgeon is ultimately responsible for assuring that the correct lens is placed at the time of surgery.

One series of 700 medico legal cases in ophthalmology conducted in the 1980s found that 154 cases were related to cataract extractions, about 22% of the total.⁴ Within this group, IOLs were the primary cause in about one-third of these claims. Three claims were based on gross miscalculation of the IOL power.

A review of 168 cataract surgery claims was conducted from data at the Ophthalmic Mutual Insurance Company (OMIC).⁵ This data was collected from 1987 to 1997, and the cataract procedures represented 33% of all claims closed during this period. It was reported that intraocular lenses constituted the largest single group of claims in this sample. These included cases in which the plaintiff claimed the wrong power, size or type of IOL was used, a defective IOL was used, or an IOL was dislocated or decentered after surgery. Claims of a wrong size, power or type of IOL were defensible, if there was documentation explaining why the surgeon selected the IOL, and reporting the measurement of the eye for IOL power calculation.

In the group of claims only involving IOLs, the claims accounting for the greatest percentage of cases involved insertion of a wrong power IOL. Specific events associated with the use of the wrong power IOL included: use of the SRK I formula for ametropia, handing the surgeon the wrong IOL in the operating room, an incorrectly labeled IOL, confusion over the manufacturer’s number for the IOL, and incorrect biometry or keratometry.

Contributing Factors to the Problem:

Potential errors leading to the placement of a wrong IOL include:

use of an older, outdated IOL formula for the patient
incorrect measurement of the eye’s axial length (biometry)
incorrect keratometry readings
mistakes in entering the data into the IOL calculation program
incorrect labeling or packaging of the IOL by the manufacturer
mistakes in providing the IOL at the time of surgery, such as a mix-up with an IOL for another patient

Axial length measurement is an important factor in determining an accurate IOL power calculation.⁶ One study of 584 IOL implantations evaluated errors in predicted refraction after implantation.⁷ It found that 54% of the error was attributed to axial length measurement errors, 8% to corneal power measurement errors, and 38% to aniot chamber depth (ACD) estimation errors. Current devices should measure within 0.1mm accuracy and reproducibility for axial length. However, an error of 0.1 mm can cause a postoperative refractive error of 0.25 diopters. Measurements may need to be repeated in difficult cases, or cases in which the results are unexpected or unusual. For patients with high hyperopia, small errors in measured axial length become more important when determining IOL power. For example, an error of 0.1 mm can result in up to 3.75D of IOL error. Bilateral measurements help to assess the reliability of results by comparing the two eyes. A significant disparity should prompt a rechecking of the measurements. The ophthalmologist is ultimately responsible for reviewing the biometry and keratometry results, even when other staff members perform the tests.

Errors in IOL manufacturing or labeling are rare but have been reported. Most IOL manufacturers claim that there is a tolerance standard of + 0.25 D error. Given this error range, IOL power is estimated to contribute less than 1% of the postoperative refractive error.⁸ However, one report found that a particular lens product was independently associated with overcorrection in a series of 523 patients undergoing cataract surgery.⁹

There has also been at least two reports in the literature suggesting that an IOL was mislabeled on the packaging.^3,10 In one report, the IOL was optically measured at 12.48D, but was labelled as 9.00 D. This resulted in patient dissatisfaction and another operation for IOL exchange.

Suggestions for Improving Patient Safety:

The following suggestions may minimize the placement of wrong IOLs:⁴

Ensure that the technicians are well trained, experienced and attentive to details in performing biometry and keratometry.
Check calibration of A-scan unit and keratometer on a daily basis.
Perform the measurements in both eyes, for comparison.
Repeat or double-check the measurements, if appropriate. For the same eye , measurement must be repeatable within 0.2mm. Between the 2 eyes there cannot be more than 0.3 mm difference (unless there is a good explanation, such as anisometropia).
Calculate scan with the appropriate third-generation formula (i.e., Holladay, Hoffer Q and SRK T)
After calculating the scan, double check numbers to ensure the proper numbers were inserted into the program.
Have a sheet or form that contains patient information; keratometry, and axial length, primary lens and alternate lens/es. Check the IOL information directly against the IOL calculation printout or form, and any pertinent patient data in the chart.
Invest in an automated software program that performs the above calculations, provides IOL selections and documents patient visual outcome.
Have good communications among the surgeon/assistant surgeon and operating room personnel, and check the lens power against the medical record in the operating room.¹¹
The correct lens should be in the operating room prior to sedation/anesthesia.

Note: The approximate IOL power, if emmetropia is desired, can be quickly calculated by using an initial power of 18D and adding the patient’s preoperative refractive state multiplied by 1.6. This can be used as a quick check for the calculated IOL power.

SUGGESTED MULTIPLE IOL VERIFICATION PROCEDURE IN THE OPERATING ROOM FOR MINIMIZING WRONG IOL PLACEMENT

PLEASE READ THIS DISCLAIMER:

These are suggested ideas for verification procedure, however, they may not be appropriate, feasible or desirable in all settings and for all patients. This verification procedure should not be deemed inclusive of all proper methods to verify the appropriate IOL, or exclusive of other protocols that are reasonable at obtaining the same results. The ultimate judgment regarding the utility and application of suggestions listed herein must be made by the operating surgeon (in collaboration with nursing staff) in light of all the circumstances presented by the patient, setting of care, and other factors.

The ophthalmic history and exam and form that contains keratometry and axial length, primary and alternate lens/es for each patient are available in the operating room.

The surgeon/ assistant surgeon selects the primary and alternate IOL/s before the start of the case. The surgeon verifies the IOL number, diopter, optic, A constant, and length against the appropriate form or documentation and/or patient medical record.

When the surgeon requests the IOL, the circulating nurse shows the IOL box to the surgeon and verbally states the IOL model number and lens power and the surgeon acknowledges the communication.

The circulating nurse then repeats this procedure with the scrub nurse/technician (i.e. shows the IOL box and verbally states the model number and lens power).

The scrub nurse/technician verbally states the model number and lens power as he/she passes the lens to the surgeon for implantation.

The surgeon performs visual inspection of the IOL under the microscope for

appropriateness and any lens defect or deposit.

If there is a discrepancy the surgeon reviews the ophthalmic history and exam and /or designated institute form.

The circulating nurse puts the IOL labels on the IOL card, operative record/patient chart right after the surgeon implants the IOL. He/ she documents the check procedure in the patient record.

Developed by the AAO Quality of Care Secretariat in collaboration with ASORN and AAEEH

References:

Institute of Medicine: To Err is Human: Building a Safer Health System. National Academy Press, 1999, Washington DC.
National Patient Safety Foundation Research Agenda, 1999. Chicago Illinois
Kohnen S: Postoperative refractive error resulting from incorrectly labeled intraocular lens power. J Cataract Refract Surg 2000; 26:777-8.
Smith HE: The incidence of liability claims in ophthalmology as compared with other specialties. Ophthalmology 1990; 97:1376-8.
Brick DC: Risk management lessons from a review of 168 cataract surgery claims. Surv Ophthalmol 1999; 43:356-60. http://63.99.42.134/resources/risk_man/deskref/clinical/41.cfm
Ellis JH: Faulty A-Scan readings present potential liability. ARGUS, 1994, AAO, San Francisco. http://63.99.42.134/resources/risk_man/deskref/clinical/21.cfm
Olsen T: Sources of error in intraocular lens power calculation. J Cataract Refrac Surg 1992; 18:125-9.
Norrby N, Grossman L, Geraghty E et al: Accuracy in determining intraocular lens dioptric power assessed by interlaboratory tests. J Cataract Refract Surg 1996; 22:983-93.
Courtright P, Paton K, McCarthy JM et al: An epidemiologic investigation of unexpected refractive errors following cataract surgery. Can J Ophthalmol 1998; 33:210-5.
Olsen T, Olesen H: IOL power mislabeling. Acta Ophthalmol (Copenh) 1993; 71:99-102.
Morris R: Wrong power IOL inserted during cataract surgery. OMIC Digest, Winter 2000, Vol 11, No. 1.

June 2001