Outcomes of Cataract Surgery: Probability of Success in Patients with Ocular and Health Comorbidities
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A cataract is a clouding o f the lens o f the eye, which develops when some destructive factor such as excessive sunlight, smoking, disease, drugs, or aging, causes proteins in the lens to aggregate It has been reported that about half o f Americans aged 65 to 74 have a cataract and approximately 70% o f those age 75 and over have a cataract (Agency for Health Care Policy and Research [AHCPR], 1998). Because o f the large number o f people having cataract surgery, and the larger number o f people estimated to need cataract surgery in the future, assessment o f cataract surgery outcomes is needed to justify this increasing expense. "Medicare beneficiaries undergo more than 1.35 million cataract extractions each year, at an estimated cost o f $3.4 billion." (Agency for Health Care Policy and Research [AHCPR], 1995). Predictors o f surgical success and failure need to be identified not only to plan for Medicare funding, but also to better counsel prospective cataract surgery patients about their probable visual outcome following surgery. A study done by Tielsch, et al., (1995) evaluated preoperative patient expectations and post-operative outcomes among patients undergoing first eye cataract surgery. Findings were that older patients and patients with some comorbidity had a high discrepancy between expected results o f surgery and actual visual outcome. Although success rates for all patients undergoing cataract removal are high, those individuals with ocular comorbidities and older age have a greater probability o f having visual outcomes that are disappointing. Therefore, there is a need to predict the probability o f outcomes based on individual patient characteristics.
The purpose o f this study was to investigate predictors o f low visual acuity outcomes following cataract removal and intra-ocular lens (IOL) insertion. Using the methods o f a previous researcher, Julie Borders, surgical outcomes and patient data were abstracted from patients’ files at a local ophthalmology practice (Borders, 1998). Borders’s thesis analyzed 140 surgeries, separating them into two groups: worse than previous visual acuity, better than previous visual acuity. Slight modifications to Borders methodology were implemented to achieve this study’s goals. Outcomes were classified into 2 groups based on their final corrected post-operative visual acuity taken at their final refractive visit: Good Outcome = 20/15 - 20/40, Poor Outcome = 20/50 or worse. M ost studies use Snellen notation o f20/40 to define a “successful” outcome. Appendix B contains an explanation o f the Snellen visual acuity scale and its decimal conversions as shown in most major ophthalomolgy journals. Logistic regression was used to estimate the probability o f achieving 20/50 or worse visual acuity, with a special emphasis placed on those individuals with ocular comorbidities or other poor outcome predictors.
The sample consisted o f236 surgeries performed by 2 surgeons in San Marcos, Texas. Subjects were limited to those receiving either first or second eye cataract surgery with no concomitant surgical procedure and no previous surgery on the operated eye. Surgical data were abstracted during 2 six-month periods: January through June 1997 (collected by Julie Borders) and October through March 2000 (collected by author). One hundred and twenty surgeries used in this study came from the database o f Julie Borders, while 116 surgical records were collected by the author. Appendix D contains a copy o f the data collection form used for both studies. Data from the collection form can be divided into 3 major areas: pre-existing variables, surgical variables, and post-operative variables.
Poor outcome was more likely to be associated with ages 81-100 than with younger ages (odds ratio, 6.038; 95% Cl, 1.837 to 19.842), with ages 71 - 80 than with younger ages (odds ratio, 3.159; 95% Cl, 1.038 to 9.616), with diabetics rather than nondiabetics (odds ratio, 4.164; 95% Cl, 1.722 to 10.068), with patients with ARMD rather than patients without ARMD (odds ratio, 2.945; 95% Cl, 1.258 to 6.892), and with high degrees o f nuclear sclerosis rather than low degrees o f nuclear sclerosis (odds ratio, 2.863; 95% Cl, 1.099 to 7.463). Within this sample, the smallest single threat (that was studied) to achieving visual acuity o f20/40 or better is nuclear sclerosis. Those 71 - 80 with nuclear sclerosis alone only have a 25.3% probability o f a poor outcome. For those 81 - 100, the probability increases to 39.3%. Within this sample, the largest single threat (that was studied) to achieving visual acuity o f20/40 or better for individuals o f all age groups is diabetes. Those 71 - 80 with diabetes and no other comorbidity have a 33.0% probability o f a poor outcome. Those 8 1 -1 0 0 with diabetes and no other comorbidity have a 48.5% probability o f a poor outcome. The probability o f a poor outcome increases within each age group for patients with multiple comorbidities. For example, patients 8 1 -1 0 0 with diabetes and ARMD have a 73.5% probability o f a poor outcome. A complete listing o f all calculated probabilities can be found in Table 4.18.
CitationDieterle, G. (2000). Outcomes of cataract surgery: Probability of success in patients with ocular and health comorbidities (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.
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