Reply: Suture-related complications after cataract surgery: A patient safety issue

LETTERS

evaluation of corneal biomechanical properties after phacoemulsification, IOPcc showed a significant decrease whereas CH returned to almost preoperative values 3 months postoperatively, indicating that factors other than CCT and IOP, ie, diabetes, aphakia, and vitrectomy, influence the CH. This area needs further investigation.dRaciha Beril Kucumen, MD

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Suture-related complications after cataract surgery: A patient safety issue

1. Lee BJ, Smith SD, Jeng BH. Suture-related corneal infections after clear corneal cataract surgery. J Cataract Refract Surg 2009; 35:939–942 2. Kelly SP, Ajit RR, Glenister HM. Hazards of redundant corneal sutures: a safety message [letter]. J Cataract Refract Surg 2004; 30:1151–1152 3. The Royal College of Ophthalmologists. Ophthalmic Services Guidance. Patient Safety in Ophthalmology. London, The Royal College of Ophthalmologists, 2008; Available from: http:// www.rcophth.ac.uk/docs/profstands/ophthalmic-services/Patient SafetyInOphthalmology1stOctober2008.pdf. Accessed July 28, 2009

The recent case series by Lee et al.1 highlights the potential morbidity that may result from a retained corneal suture placed during routine cataract surgery via a clear corneal incision. We managed a similar case at our institution. Cataract extraction and intraocular lens implantation via a superotemporal corneal incision had been performed in the right eye of a 67-year-old man 18 months previously at another hospital. The clinical appearance was suggestive of small-incision cataract surgery. On presentation to us, a retained 10-0 nylon corneal suture was found at 10 o’clock, associated with a 1.5 mm stromal abscess and hypopyon. The suture was loose. Microbiological culture of the suture revealed heavy growth of Staphylococcus aureus. The infective keratitis responded well to antibiotic therapy, and the patient retained a corrected distance visual acuity of 20/30 despite residual corneal scarring. We reported this case2 and also described the occurrence of such a complication as a ‘‘system failure.’’ The ‘‘active failure’’ (ie, unsafe act) was failure to remove the corneal suture. Several ‘‘latent failures’’ (ie, suboptimal preconditions) were also identified. We proposed the following safeguards to reduce the incidence of suture-related complications after phacoemulsification cataract surgery: (1) rigorous documentation in the surgery notes regarding suture insertion and plans for removal; (2) improved communication with the patient, care providers, and general practitioner in relation to corneal sutures; (3) increased awareness among the multidisciplinary team. The message is simple: Nonabsorbable corneal sutures must be removed, and the responsibility for this lies with the operating team supported by patient involvement. Efforts to improve patient safety are important, international, and topical. The Royal College of Ophthalmologists provides guidance on patient safety in ophthalmology, drawing on a growing understanding of the general principles involved.3 Roxane J. Hillier, MRCOphth Rajitha R. Ajit, FRCSEdOphth Simon P. Kelly, FRCOphth Manchester, United Kingdom

REPLY: The case presented by Hillier et al. had a clinical course similar to those in our series, and it strengthens our suggestion that exposed sutures should be removed during the early postoperative period. In the letter to which Hillier et al refer,1 Kelly et al. were commenting on the report of a series of endophthalmitis cases resulting from corneal sutures placed after extracapsular cataract extraction.2 Specifically, they commented that after small-incision cataract surgery, corneal sutures should be removed prior to discharge from ophthalmic care. We fully agree with this recommendation and believe that our cases support this assertion. In the current letter, Hillier et al. suggest having ‘‘prebooked’’ suture removal appointments. This is an excellent idea, but it requires an extra visit (and therefore time) for the patient, as well as an extra patient slot for the ophthalmologist. It may be more practical to incorporate the planned suture removal into the existing postoperative follow-up schedule. For example, most of our surgeons see patients 1 day, 1 week, and approximately 1 month after cataract surgery. During the 1-week follow-up visit, the suture, if used, is removed. In addition, during the first week postoperatively, our patients are treated with topical antibiotic eyedrops; therefore, the ocular surface and the suture are less likely to be colonized with bacteria that might inoculate the corneal stroma as the suture is removed. Furthermore, suture removal at this point allows suture-induced astigmatism to be relieved prior to the final refraction at the 1-month postoperative visit. Of course, in the case of corneal wound burns or extremely short wounds, the corneal sutures may have to remain in place longer, but in these instances, scheduling an additional follow-up visit to remove the suture within the first month of surgery would be warranted. In the process of reviewing the cases in our series, we found that the incidence of suture-related infections at our institution was 0.0 per 1000 patient-years (Poisson confidence interval 0 to 0.94 infections per 1000 patient-years) among surgeons who routinely remove

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the sutures and 2.2 per 1000 patient-years (Poisson confidence interval 0.46 to 6.6 infections per 1000 patient-years) among surgeons who do not routinely remove the sutures. The between-group difference was statistically significant (P Z .02) (unpublished data). We agree with Hillier et al. that nonabsorbable corneal sutures must be removed after routine phacoemulsification surgery. We hope that our series of patients along with the suggestions from Hillier et al. will encourage others to have a heightened awareness of this problem and to consider changing their practice patterns if they do not routinely remove these sutures.dBrian J. Lee, MD, Scott D. Smith, MD, MPH, Bennie H. Jeng, MD REFERENCES 1. Kelly SP, Ajit RR, Glenister HM. Hazards of redundant corneal sutures: a safety message [letter]. J Cataract Refract Surg 2004; 30:1151–1152 2. Khurshid GS, Fahy GT. Endophthalmitis secondary to corneal sutures: series of delayed-onset keratitis requiring intravitreal antibiotics. J Cataract Refract Surg 2003; 29:1370–1372

Analysis of post-DSEK corneal profile and relationship to hyperopic shift We were interested in the article by Holz et al.1 because in our experience, patients having Descemet stripping endothelial keratoplasty (DSEK) exhibit varying degrees of hyperopic shift; one of our patients showed a C4 diopter shift in the refractive status postoperatively. The authors’ explanation for this apparent shift using corneal profiling with anterior segment optical coherence tomography (AS-OCT) is an interesting concept as there seems to be a definite alteration in the posterior profile of the cornea, thus altering the refractive power of the cornea. However, several other factors may contribute to the hyperopic shift. In the thick lens equation,2 the focal length is dependent on several variables: 1. The thickness of the cornea: According to the thick lens equation (http://www.lightmachinery.com/ thick-lens. Accessed August 4, 2009), any increase in the thickness of a lens would result in an increase in focal length. As we are adding stromal tissue to the recipient’s cornea, one would expect an induced hyperopic shift. Assuming the corneal thickness increased from 550 mm preoperatively to 700 mm postoperatively and all other variables were stable (corneal refractive index Z 1.3771, R1 Z 7.8 mm, R2 Z 6.5 mm),3 the power of the cornea would decrease by 30%. This reduction would induce a significant hyperopic shift. It would have been useful to know the pachymetry readings preoperatively and

postoperatively and to assess whether patients who have a significant hyperopic shift also had a larger than expected increase in central corneal thickness. 2. The posterior radial curvature of the cornea: As the radius of curvature of the posterior surface of the cornea decreases (as demonstrated by AS-OCT), there is an increase in the focal length of the cornea, thus inducing a hyperopic shift. A change in the posterior curvature from 6.5 mm to 5.5 mm would result in an 11% hyperopic shift in the power of the cornea. 3. The corneal epithelium: It has been demonstrated that the corneal epithelium induces a hyperopic shift in the power of the cornea.4 The ability of the corneal epithelium to remodel after laser in situ keratomileusis has been shown,5 and we postulate that the recipient’s corneal epithelium will remodel as the cornea recompensates following endothelial transplantation. This effect could contribute to the hyperopic shift seen. It would also be interesting for future studies to investigate whether there is any demonstrable difference in the profiles of precut tissue compared with manually dissected tissue, as one would expect that with the latter, there may well be more irregular peripheral dissection. Rakesh Jayaswal, MRCOphth, FCRS(Ed) Philip Alexander, MRCOphth V. Senthil Maharajan, DO, DNB, FRCS, DM Nottingham, United Kingdom REFERENCES 1. Holz HA, Meyer JJ, Espandar L, Tabin GC, Mifflin MD, Moshirfar M. Corneal profile analysis after Descemet stripping endothelial keratoplasty and its relationship to postoperative hyperopic shift. J Cataract Refract Surg 2008; 34:211–214 2. Morgan J. Introduction to Geometrical and Physical Optics. New York, NY, McGraw-Hill, 1953; 57 3. Wyszecki G, Stiles WS. Color Science; Concepts and Methods, Quantitative Data and Formulae 2nd ed. New York, NY, John Wiley & Sons, 1982 4. Simon G, Legeais JM, Parel JM. Optical power of the corneal epithelium. J Fr Ophthalmol 1993; 16:41–47 5. Reinstein DZ, Silverman RH, Sutton HFS, Coleman DJ. Very high-frequency ultrasound corneal analysis identifies anatomic correlates of optical complications of lamellar refractive surgery; anatomic diagnosis in lamellar surgery. Ophthalmology 1999; 106:474–482

REPLY: We thank Jayaswal et al. for continuing to investigate factors that may contribute to hyperopic shift following DSEK. Concerning the 3 variables they proposed as causes of hyperopic shift, we agree with 2 of them: increased central corneal thickness

J CATARACT REFRACT SURG - VOL 35, NOVEMBER 2009