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Outcomes of cataract extraction in seeing eyes of functionally monocular versus completely monocular patients

Miller, Adam R. MD; Miller, Kevin M. MD

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Journal of Cataract & Refractive Surgery: May 2010 - Volume 36 - Issue 5 - p 712-717
doi: 10.1016/j.jcrs.2009.11.014
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Abstract

Functionally monocular patients are encountered frequently in ophthalmology practice and are a distinct challenge in terms of management because they have a higher prevalence of ocular comorbidity than binocularly sighted patients.1 When a monocular patient develops a cataract in the better-seeing eye, ophthalmologists may be reluctant to recommend cataract surgery because of concerns that surgical complications may lead to bilateral blindness, an event that has been documented.2,3 In light of this concern, studies report generally favorable results supporting the judicious use of cataract extraction in monocular cases.1,4,5

A distinction can be drawn between monocular patients who have no light perception (NLP) in the blind eye and those who are functionally monocular (but retain visual acuity worse than 20/200 in their blind eye). When weighing risks and benefits, ophthalmologists may feel more comfortable performing cataract extraction in the seeing eyes of functionally monocular patients than in completely or truly monocular patients because of the decreased theoretical risk for complete bilateral blindness in the event of a surgical complication.

We believe this opinion may benefit from reevaluation because these 2 subtypes of patients may present with different types and severities of comorbidity that may affect surgical outcomes in the eye with better vision. It was our hypothesis that completely monocular patients may have an increased prevalence of surgical or traumatic comorbidities that are likely to be confined to the blind eye. In contrast, functionally monocular patients may have a higher prevalence of disease processes (eg, macular degeneration, diabetic retinopathy) that may affect their eyes bilaterally and complicate surgery or long-term vision results in the good eye.

In this study, we examined the outcomes of cataract surgery in the seeing eyes of monocular patients, making a distinction between patients with NLP in the blind eye and those whose visual acuity in that eyes ranged between light perception (LP) and 20/200. Preoperative comorbidities in the seeing (surgical) eyes and fellow eyes were compared between the 2 groups. Other outcome measures included postoperative corrected distance visual acuity (CDVA), additional postoperative procedures, and surgical complications.

PATIENTS AND METHODS

This nonrandomized consecutive retrospective study was performed with institutional review board approval. The work was compliant with the U.S. Health Insurance Portability and Accountability Act of 1996.

Consecutive functionally monocular patients with very poor or no vision in 1 eye and a cataractous lens in the better-seeing eye who had cataract surgery in the better eye between January 1995 and March 2006 were identified. Patients were included if they were monocular, defined as a CDVA of 20/200 or worse in the nonoperated blind eye and better than 20/200 in the good eye. The patients were divided into 2 groups. Group 1 included patients whose CDVA ranged from LP to 20/200 in the blind eye. Group 2 included patients with NLP in the blind eye.

Preoperatively, a thorough history was obtained and slitlamp examination performed to assess the potential for improvement in CDVA after cataract surgery. The same surgeon (K.M.M.) performed all cataract extractions and all preoperative and postoperative examinations. All cataract surgery was by the phacoemulsification technique. In most cases, a posterior chamber intraocular lens (IOL) was implanted in the capsular bag. The type of anesthesia was selected based on the patient's needs.

Patients were examined preoperatively and postoperatively at 1 day and 1 to 2 weeks; subsequent examinations were performed as needed. Comorbidities other than cataract were recorded whether or not they increased the odds of surgical complications or reduced the potential for visual improvement. Changes in CDVA, complications, and recommendations for additional procedures were also recorded at each patient visit.

RESULTS

The study included 105 patients. Table 1 shows the patients' demographic information by group. The median follow-up was 10 months in Group 1 and 9 months in Group 2 and the mean follow-up, 21 months and 15 months, respectively (P = .34, Kruskal-Wallis test).

Table 1
Table 1:
Demographic information.

Table 2 shows the preoperative comorbidities present in the operated eyes. Table 3 shows the preoperative comorbidities present in the blind eyes.

Table 2
Table 2:
Comorbidities in better-seeing operated eyes.
Table 3
Table 3:
Comorbidities in blind fellow eyes.
Table 3
Table 3:
(continued)

Figure 1 shows the postoperative visual acuity at 2 weeks and at the final examination. The reasons for the loss of CDVA at the final examination are noted. At the 2-week examination (Figure 1, A and C), the CDVA was worse in 3 patients (4.1%) in Group 1 and 1 patient (3.1%) in Group 2 (P = 1.00, Fisher exact test). All patients in Group 1 with reduced CDVA at 2 weeks had improved visual acuity at the final examination. At the final examination (Figure 1, B and D), 14 patients (19.2%) in Group 1 and 2 patients (6.3%) in Group 2 lost CDVA (P = .22, log rank tests).

Figure 1
Figure 1:
Scattergrams of preoperative vs postoperative CDVA. A: Group 1 at the 2-week postoperative examination. B: Group 1 at the final postoperative examination. C: Group 2 at the 2-week postoperative examination. D: Group 2 at the final postoperative examination (AMD = age-related macular degeneration; BRVO = branch retinal vein occlusion; CDVA = corrected distance visual acuity; CF = count fingers; DR = diabetic retinopathy; HM = hand motions; IOL = intraocular lens; LP = light perception; NLP = no light perception; PCO = posterior capsule opacification; SCC = squamous cell carcinoma).

Table 4 shows the intraoperative and postoperative procedures in addition to cataract surgery. In Group 1, 19 (26.0%) additional procedures were performed intraoperatively and 26 (35.6%) additional procedures were performed postoperatively. In Group 2, 10 (31.3%) additional procedures were performed intraoperatively and 16 (50.0%) additional procedures were performed postoperatively.

Table 4
Table 4:
Additional intraoperative and postoperative procedures.

Table 5 shows all intraoperative and postoperative complications. In Group 1, 6 patients (8.2%) had intraoperative complications, 1 patient (1.4%) developed complications during the first postoperative week, and 37 patients (50.7%) developed complications after the first postoperative week. In Group 2, 5 patients (15.6%) had intraoperative complications, 1 patient (3.1%) developed complications during the first postoperative week, and 20 patients (62.5%) developed complications after the first postoperative week.

Table 5
Table 5:
Intraoperative and postoperative complications.

DISCUSSION

This study compared the outcomes of cataract extraction in the seeing eyes of completely monocular patients and functionally monocular patients. We evaluated the preoperative comorbidities in operated eyes and blind eyes in both groups. Outcome measures included changes in CDVA, additional procedures performed intraoperatively or postoperatively, and complications in the operated eyes.

In defining the groups for the study, we did not use terms such as legally blind or truly monocular. By visual acuity criteria, persons who are legally blind in the United States have an acuity of 20/200 or worse in both eyes. Patients who are truly monocular have only 1 seeing eye.

Patients in both groups in our study had comparable numbers of preoperative comorbidities in the operated eyes. Except for 1 surgical comorbidity in Group 2, all preoperative comorbidities were medical. Similarly, there were no differences between groups in the numbers of comorbidities in the blind eyes. There was, however, a statistically significant between-group difference in the types of comorbidities noted. Group 1 had significantly more medical comorbidity than Group 2, while Group 2 had significantly more surgical comorbidity than Group 1. We expected these findings before the study. No cataract in a blind eye was considered visually limiting.

There was no significant difference between the 2 groups in the number of additional procedures required intraoperatively or postoperatively or in complications.

At the 2-week postoperative examination, there was no statistically significant difference in CDVA between the 2 groups. Although 3 patients in Group 1 lost 1 to 2 lines of CDVA, the acuity improved in all cases by the last postoperative visit recorded in the medical record. However, 19.2% of patients in Group 1 lost CDVA by the final examination compared with 6.3% of patients in Group 2. Although the difference between groups did not reach statistical significance, it appears to be clinically relevant and might have reached statistical significance with longer follow-up. We believe that the difference in visual outcomes between groups is related to the discrepancy between medical comorbidity and surgical comorbidity in the blind eyes. Surgical causes of blindness, such as trauma, endophthalmitis, and retinal detachment, are generally unilateral with a low likelihood of complicating surgery in the fellow eye. On the other hand, medical causes of blindness, such as diabetic retinopathy, glaucoma, and macular degeneration, are usually bilateral processes, even if the manifestations are more severe in 1 eye. Thus, when considering cataract extraction in the seeing eye of a functionally monocular patient with retained but limited vision in the blind eye, surgeons should consider that CDVA in the good eye may worsen in the later postoperative period as a consequence of progression of medical comorbidity.

Although the median follow-up was similar between the groups, the mean interval was slightly different; that is, 21 months in Group 1 and 15 months in Group 2. These data did not fit a normal distribution, nor did the difference reach statistical significance. It is likely that Group 2 patients chose to terminate follow-up earlier than Group 1 patients because they were more satisfied with their vision after surgery.

Patients become monocular with varying severities of blindness in the affected eye. Blindness may result from a variety of medical or surgical etiologies. Our results show that patients who with NLP in the blind eye tend to fare better than patients who retain some poor vision in the blind eye after cataract surgery in the better-seeing eye. This may be counterintuitive. Based on the results in this study, ophthalmologists should be relieved that short-term results are no worse for patients with NLP in the fellow eye. However, they should consider counseling patients who have limited vision in the fellow eye that despite initially successful cataract surgery, they may lose visual acuity over the long term as a result of medical comorbidities.

REFERENCES

1. Trotter WL, Miller KM. Outcomes of cataract extraction in functionally monocular patients: case-control study. J Cataract Refract Surg. 2002;28:1348-1354.
2. Rodríguez AA, Olson MD, Miller KM. Bilateral blindness in a monocular patient after cataract surgery. J Cataract Refract Surg. 2005;31:438-440.
3. Morris R, Camesasca FI, Byrne J, John G. Postoperative endophthalmitis resulting from prosthesis contamination in a monocular patient. Am J Ophthalmol. 1993;116:346-349.
4. Bergwerk KL, Miller KM. Outcomes of cataract surgery in monocular patients. J Cataract Refract Surg. 2000;26:1631-1637.
5. Pomberg ML, Miller KM. Functional visual outcomes of cataract extraction in monocular versus binocular patients. Am J Ophthalmol. 2004;138:125-132.
© 2010 by Lippincott Williams & Wilkins, Inc.