July 2018


EyeWorld journal club
Review of “An updated cataract surgery complexity stratification score for trainee ophthalmic surgeons”

by Angela Verkade, MD, Rizwan Shaikh, MD, Rishabh Date, MD, Zaina Al-Mohtaseb, MD, and Mitchell Weikert, MD, Cullen Eye Institute, Baylor College of Medicine, Houston

Mitchell Weikert, MD, residency program director, Cullen Eye Institute, Baylor College of Medicine

Zaina Al-Mohtaseb, MD, associate residency program director, Cullen Eye Institute, Baylor College of Medicine

Is there a way to accurately score cataract case complexity preoperatively for complication risk? I invited the Baylor residents to review this paper from the June issue of JCRS that proposes such a scoring system.

—David F. Chang, MD,
EyeWorld journal club editor


Rishabh Date, MD, Angela Verkade, MD, and Rizwan Shaikh, MD
Source: Baylor College of Medicine

Posterior capsular rupture (PCR) during cataract surgery and intraocular lens placement is one of the most feared resident surgeon complications. In an attempt to minimize complications, trainee programs aim to select cases appropriate for each resident level. Varying cataract grading systems have been suggested, but unfortunately complications can still occur at all levels.1,2,3,4,5 In “An updated cataract surgery complexity stratification score for trainee ophthalmic surgeons,” Nderitu et al. suggest a new, more easily quantifiable scoring system that incorporates all of the most recently established risk factors for PCR as determined by the Cataract National Dataset (CND).
The CND is a database that utilizes 55,567 operations compiled from the National Health Service (NHS) based in the United Kingdom.6 They analyzed risk factors for PCR and found 11 patient factors—increasing patient age, male gender, glaucoma, diabetic retinopathy, brunescent/white cataract, no view to fundus/vitreous opacities, pseudoexfoliation/phacodonesis, reduced pupil size, axial length, use of alpha blockers, or inability to lie flat—that resulted in a higher risk of PCR. In addition to these factors, Nderitu et al. included other risk factors suggestive of intraoperative complications including postoperative corneal edema, hearing impairment, and poor vision in the unoperated eye to their scoring system.
The authors calculated a preoperative composite risk score during their initial clinic appointment based on the risk factors listed above in order to stratify their patients to the appropriate surgeon based on operative experience. They compared PCR rates and other intraoperative and postoperative complications between surgeons. Surgeon training levels ranged from first year trainee surgeons to consultant surgeons with the most case experience. The consultant surgeons operated on the highly complex patients based on the quantified risk scoring system. Their goal was to establish a quantifiable risk scoring system in order to better match patients in their clinic with the appropriate surgeon, thereby decreasing postoperative/intraoperative complications such as PCR.
In the study, 11,468 cases were reviewed and 8,200 (71.2%) of them were assigned a complexity score. The remaining patients served as controls in their retrospective cohort design. Regardless of complexity score, consultant surgeons performed 61–85% of cases. They found that grade 5 (highest) complexity carried a 10% incidence of having a smaller pupil but a 7-fold increase in pupil expander use compared to grade 1 cases. Intermediate level trainees used pupil expanding devices more often than consultants did during these more complex cases. Both postoperative corneal edema and elevated intraocular pressure were associated with more complex cases. Interestingly, the authors found that there was no increase in posterior capsular rupture or zonular rupture (PCR/ZR) and vitreous loss (VL) with increasing complexity score. Junior trainees had statistically higher rates of PCR/ZR and VL in the study when compared to consultants, but not when compared to senior trainees. According to the authors’ risk stratification, patients with the highest complexity carried a 4-fold increase of intraoperative iris-phaco damage.
Higher complexity scores resulted in worse postoperative best distance visual acuity overall, but the highly complex patients had a greater mean improvement in postoperative vision when compared to less complex patients. Lastly, control patients without a complexity score were found to have higher intraoperative complications, thereby supporting the authors’ assertion that a scoring system is needed to better match these patients with an appropriately trained surgeon.
The authors present a unique evidence-based cataract complexity score that incorporates several established risk factors for PCR. Using logistic regression analysis they were able to show a correlation between the complexity score and intra- and postoperative complications. Utilizing a score like this in a training setting has the potential to significantly simplify and standardize the cataract surgery learning process. Stratifying surgeries by complexity level not only allows more effective tailoring to surgeon experience, but also optimizes the chance of achieving favorable outcomes for patients. Additionally, the complexity score can be a tool for counseling patients on surgical and postoperative expectations. Explaining their risk stratification process, the surgeons could minimize patient preoperative concerns with reassurance that a complex patient would not be inappropriately matched to a surgeon with less experience.
The study benefits from a large sample size obtained from an extensive and reliable database. The electronic medical record (EMR) at the study site’s clinic, which utilizes forced data entry, ensures that a complete preoperative profile is created for all patients. The authors collected data over 6 years of surgeries with inclusion of nearly 50 surgeons, which allows for a more uniform spread of surgical ability. However, the large majority of surgeries were not performed by the trainees for whom the complexity score is designed, which is a factor that will likely need to be addressed in future validations of this model.
In regard to the complexity score, the authors make the appropriate choice to incorporate evidence-based risk factors for PCR, which avoids the question of relevancy of these factors. They take their model a step further by considering other patient factors such as preoperative corneal edema or monocular status, which may not necessarily be predictive of PCR but are significant considerations when contemplating intraoperative risks. Unfortunately, as the authors point out, these risk factors were considered in aggregate when calculating the complexity score, therefore making it difficult to determine the contribution of each particular risk factor from this data alone. Additionally, the complexity score does not take into account several other risk factors, such as grading brunescent/density of cataract, history of prior surgery, history of trauma (though it does consider phacodonesis), or anatomical variations like large brows or deep sulci. These factors, while they may not necessarily predict PCR, do contribute to the difficulty of the surgery and are oftentimes a large component of determining the appropriate surgeon training level for the case. At the same time, it is also vital to recognize the importance of having a simple model that can be calculated and applied quickly. A complicated complexity score incorporating
too many variables can become cumbersome and inefficient. Thus, an effective model must strike a balance between simplicity and comprehensiveness.
The current study may also be affected by reporting bias, as all intraoperative and postoperative events may not necessarily be recorded in the EMR, thus a prospective study could reduce the presence of such bias. It is also crucial to consider evaluating the complexity score on populations outside the study site in order to demonstrate broader applicability of the model.
In summary, the authors present a new model for standardizing cataract evaluation and assignment of cases to trainees. Through several thousand cases they show that their complexity score does indeed correlate with intra- and postoperative complications. While this model would benefit from a prospective validation on a different population with more trainees, it does show promise for improving the cataract surgery learning process.


1. National Institute for Health and Care Excellence. Cataracts in adults: management. October 2017. www.nice.org.uk/guidance/ng77. Accessed June 11, 2018.
2. Najjar DM, Awwad ST. Cataract surgery risk score for residents and beginning surgeons. J Cataract Refract Surg. 2003;29:2036–7.
3. Muhtaseb M, et al. A system for preoperative stratification of cataract patients according to risk of intraoperative complications: a prospective analysis of 1441 cases. Br J Ophthalmol. 2004;88:1242–6.
4. Habib MS, et al. The role of case mix in the relation of volume and outcome in phacoemulsification. Br J Ophthalmol. 2005;89:1143–6.
5. Gupta A, et al. Cataract classification system for risk stratification in surgery. J Cataract Refract Surg. 2011;37:1363–4.
6. Narendran N, et al. The Cataract National Dataset electronic multicentre audit of 55,567 operations: risk stratification for posterior capsule rupture and vitreous loss. Eye (Lond). 2009;23:31–7.

Contact information

Weikert: mweikert@bcm.edu

Review of “An updated cataract surgery complexity stratification score for trainee ophthalmic surgeons” Review of “An updated cataract surgery complexity stratification score for trainee ophthalmic surgeons”
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