Journal of Refractive Surgery

The articles prior to January 2013 are part of the back file collection and are not available with a current paid subscription. To access the article, you may purchase it or purchase the complete back file collection here

Opinion 

20/20-HOW CLOSE MUST WE GET?

Theodore P Werblin, MD, PhD

Abstract

It has always been curious to me that despite the fact that refractive surgical patients preoperatively use glasses and/or contact lenses and usually achieve 20/20 or better visual acuity, postoperative visual acuity of less than "20/20" is felt to be "acceptable," ie, generates a "happy" patient. My experience in prescribing glasses and contact lenses in nonsurgical patients, however, teaches me that most patients who must use these devices are highly critical of any visual outcome less than perfect, and even the difference between 20/20 and 20/15 can be a major issue.

Why is it that refractive surgeons must use this new concept of "acceptable vision" or "a happy patient" to explain their imperfect art? This is not just a semantics issue, but creates very fundamental problems for both patients and surgeons. All would agree that stable 20/20 or 20/15 visual acuity after a refractive surgical procedure would be ideal. What happens when this is not an achievable goal and can we adequately inform our patients of this fact?

This issue comes up repeatedly with respect to many refractive procedures, and is especially relevant to radial keratotomy. Clearly, the instability of radial keratotomy, albeit small1,2, should create significant concern. Not to pick on radial keratotomy, but most corneal procedures have over time a significant element of instability. Planning for a small amount of ametropia so that the long-term result might be more acceptable presents conceptual problems for some patients. Surgeons who perform radial keratotomy tend to aim for a -0.50 diopters (D) to -0.75 D (about 20/25 to 20/30 uncorrected visual acuity). Undercorrection will move this refractive result closer to emmetropia when the hyperopic shift seen postoperatively in the first few years. Recently, I changed my operative philosophy from an emmetropia goal to a slightly myopic endpoint. However, my patient education results in convincing patients to stay slightly myopic have not been impressive. In my first year of performing radial keratotomy (between 1990 and 1991), 222 consecutive eyes had surgery attempting to fully correct distance visual acuity. The average refraction before surgery was -4.07 ± 1.89 D and at 1 year after surgery, it was -0.18 ± 0.54 D. As I followed these initial patients for a few years, hyperopic shift reared its head and I began to aim for a slight undercorrection. Three years after starting to perform radial keratotomy, I looked at a consecutive series of 237 distance corrected eyes. The mean preoperative refraction was -3.98 ± 1.85 D and the 1-year postoperative refraction was -0.34 ± 0.47 D. The operative technique was similar for both groups- confirmed by similar results for the primary surgery in both groups. The 1-month mean postoperative refraction was -0.58 D in the earlier group and -0.68 D in the later group. There were no statistically significant differences (p>0.05). However, the final refractive results were statistically different after enhancement procedures. The mean 3-month and 1-year enhancement results in the earlier group were -0.32 D and -0.18 D and in the more recent group were - 0.45 D and -0.34 D, respectively. Both were statistically significant differences, the more recent group showing a greater degree of postoperative residual myopia, albeit small. Why wasn't the difference greater, especially when the surgeon was aiming for between -0.50 to -0.75 D during the same 3-month to 1-year time period? The answer is very simple but surprisingly difficult to intuit. Patients are just not anxious to stay at 20/25 to 20/30 visual acuity, even for a short time (less than 1 year)- and even if they are told that their long-term visual acuity may be worse if they get…

It has always been curious to me that despite the fact that refractive surgical patients preoperatively use glasses and/or contact lenses and usually achieve 20/20 or better visual acuity, postoperative visual acuity of less than "20/20" is felt to be "acceptable," ie, generates a "happy" patient. My experience in prescribing glasses and contact lenses in nonsurgical patients, however, teaches me that most patients who must use these devices are highly critical of any visual outcome less than perfect, and even the difference between 20/20 and 20/15 can be a major issue.

Why is it that refractive surgeons must use this new concept of "acceptable vision" or "a happy patient" to explain their imperfect art? This is not just a semantics issue, but creates very fundamental problems for both patients and surgeons. All would agree that stable 20/20 or 20/15 visual acuity after a refractive surgical procedure would be ideal. What happens when this is not an achievable goal and can we adequately inform our patients of this fact?

This issue comes up repeatedly with respect to many refractive procedures, and is especially relevant to radial keratotomy. Clearly, the instability of radial keratotomy, albeit small1,2, should create significant concern. Not to pick on radial keratotomy, but most corneal procedures have over time a significant element of instability. Planning for a small amount of ametropia so that the long-term result might be more acceptable presents conceptual problems for some patients. Surgeons who perform radial keratotomy tend to aim for a -0.50 diopters (D) to -0.75 D (about 20/25 to 20/30 uncorrected visual acuity). Undercorrection will move this refractive result closer to emmetropia when the hyperopic shift seen postoperatively in the first few years. Recently, I changed my operative philosophy from an emmetropia goal to a slightly myopic endpoint. However, my patient education results in convincing patients to stay slightly myopic have not been impressive. In my first year of performing radial keratotomy (between 1990 and 1991), 222 consecutive eyes had surgery attempting to fully correct distance visual acuity. The average refraction before surgery was -4.07 ± 1.89 D and at 1 year after surgery, it was -0.18 ± 0.54 D. As I followed these initial patients for a few years, hyperopic shift reared its head and I began to aim for a slight undercorrection. Three years after starting to perform radial keratotomy, I looked at a consecutive series of 237 distance corrected eyes. The mean preoperative refraction was -3.98 ± 1.85 D and the 1-year postoperative refraction was -0.34 ± 0.47 D. The operative technique was similar for both groups- confirmed by similar results for the primary surgery in both groups. The 1-month mean postoperative refraction was -0.58 D in the earlier group and -0.68 D in the later group. There were no statistically significant differences (p>0.05). However, the final refractive results were statistically different after enhancement procedures. The mean 3-month and 1-year enhancement results in the earlier group were -0.32 D and -0.18 D and in the more recent group were - 0.45 D and -0.34 D, respectively. Both were statistically significant differences, the more recent group showing a greater degree of postoperative residual myopia, albeit small. Why wasn't the difference greater, especially when the surgeon was aiming for between -0.50 to -0.75 D during the same 3-month to 1-year time period? The answer is very simple but surprisingly difficult to intuit. Patients are just not anxious to stay at 20/25 to 20/30 visual acuity, even for a short time (less than 1 year)- and even if they are told that their long-term visual acuity may be worse if they get additional enhancements to achieve 20/20 in the short-term. Hours of frustrating discussion with patients occur on this subject and almost as much time is spent on concepts related to monovision and presbyopia. The bottom line is that many patients will not settle for a little less than their preoperative visual acuity! Patients will not be "happy" until refractive surgery is able to achieve results equal to or better than glasses and contacts, both in terms of stability and accuracy.3

REFERENCES

1. Werblin TP, Stafford GM. Three year results of refractive keratotomy using the Casebeer system. J Cataract Refract Surg 1996;22:1023-1029.

2. Werblin TP, Stafford GM. Hyperopic shift after refractive keratotomy using the Casebeer system. J Cataract Refract Surg 1996;22:1030-1036.

3. Werblin TP. Clear lens/cataract extraction for refractive purposes.In: Principles and Practice of Refractive Surgery. Philadelphia, PA: WB Saunders; 1996:449-458.

10.3928/1081-597X-19970501-17

Sign up to receive

Journal E-contents