Lean Six Sigma Process Improvement in the Retina Clinic

Clinic efficiency can be improved using manufacturing analysis systems.


The US health care system serves a rapidly expanding elderly population undergoing increasingly complex medical care shifted to an outpatient clinic environment. Retina specialists can have particularly busy clinics due to the high incidence of diabetic retinopathy and neovascular AMD (nAMD) that affect the population, and the need for frequent monitoring of the disease response to treatment. The frequent involvement of OCT and FA contribute to additional throughput time for the patient and can cause bottlenecks in the clinic, as multiple patients may need imaging at the same time. Intravitreal injections have become an increasingly common clinic-based treatment for a variety of exudative retinal diseases since anti-VEGF pharmacotherapy was introduced in the early 2000s. The resulting increased visit frequency has created service pressures on ophthalmology departments.1 Furthermore, the associated inventory management, preparation, administration, and billing processes for these intravitreal injections requires additional process development and labor.


Without corresponding process improvement, these changes have potential to significantly prolong patient wait and total visit times. Enhancing patient flow is key to maximizing revenue and patient satisfaction. Patient visit time includes patient care tasks and patient waiting time, which correlates with overall patient satisfaction, as demonstrated in one study conducted in an ophthalmology clinic.2 Patient satisfaction will also play a role in physician reimbursement, because the Medicare Act and CHIP Reauthorization Act (MACRA) and Merit-Based Incentive Payment System (MIPS) will reward or penalize physicians based on resource use and clinical practice improvement (of which patient satisfaction is an essential component).

While waiting time is commonly accepted as a measure of patient satisfaction, health care providers have not yet commonly recognized prolonged waiting time as a defect in care that can be formally assessed through traditional manufacturing measurement and techniques including Lean and Six Sigma (Figure 1). Derived from the Toyota Production System, Lean emphasizes streamlining process by eliminating waste such as transportation, inventory, motion, waiting, over-processing, and excessive production.3 From an operations standpoint, Lean can be applied to health care, because processing a patient through an office visit represents the creation of relative value units through multiple steps, including check-in, intake, treatment, and check-out.

Figure 1. Outpatient care process improvement.

Six Sigma, developed by Motorola in 1986 and popularized by Jack Welch’s adoption at General Electric in 1995, aims to identify and eliminate defects and to reduce variation in processes. The Greek letter sigma is used by statisticians to represent standard deviation, a measurement of the variability in any process; the six sigma standard represents 3.4 defects per million opportunities. Six Sigma is a statistically and organizationally rigorous process improvement method that follows 5 steps to define, measure, analyze, improve, and control a problematic process (corresponding to the acronym, “DMAIC”).3 Processes with poor reproducibility, wasted resources, and/or high variation are often identified as having defects.

High variations in patient visit time are common, as the flow through the office varies, depending on whether patients are new or established, and whether they require extensive testing and/or treatments. This variation contributes to clinic inefficiencies and prolonged waiting times, and also represents a defect in care. Although Six Sigma techniques are widely used in the manufacturing industry, there is very little literature describing their use to improve waiting times in ophthalmology outpatient clinics. Lean and Six Sigma have considerable overlap, hence the term “Lean Six Sigma” being used with greater frequency. Process improvement requires aspects of both approaches to maximize positive results. Lean focuses on waste reduction, whereas Six Sigma focuses on variation reduction.

Although waiting time represents a common and important measure of patient satisfaction and quality in health care, from an operations standpoint, it represents waste. However, waiting is only one form of waste according to Lean principles. Waste in ophthalmology clinics can be categorized into 7 types according to Lean principles:

  1. Overproduction: Inappropriate testing or treatment represents a form of overproduction. Although this is generally not billed to or paid by payers, it represents a misallocation of resources, adding to staffing expenses, equipment expenses, space expenses, and waiting times to others’ visits. Causes can include inappropriate work-up protocols and poor communication.
  2. Inventory: Patients waiting to be serviced represent inventory. This creates waste as they must be tracked, require waiting room space that does not generate revenue, and requires extra staffing, expensive chairs, water coolers, coffee, televisions, and so on. Causes of patient waiting include variation in patient type or visit type, overscheduling, unbalanced workload, inadequate staffing, and inadequate facilities.
  3. Waiting: Idle space, diagnostic testing, and staff all represent waiting. This creates waste, as there is underutilization of resources, decreased productivity, and increased investment. Causes include inappropriate scheduling, unbalanced workload, and long set-up times.
  4. Unnecessary transport: Patients being placed in incorrect areas of the clinic (incorrect exam room, incorrect testing room) represents unnecessary transport. Unnecessarily moving elderly patients in walkers or wheelchairs creates potential for injury. Causes include poor scheduling, communication, and flow design.
  5. Unnecessary processing: Inappropriate referrals, when a patient should have been referred to another type of physician for a different problem, represents unnecessary processing. This misallocation of resources creates waste on numerous levels: for the patient and his or her family who spend time in the office, for those paying for the visit, for the patient whose appropriate visit was bumped by the inappropriate referral, and for the practice, which likely foregoes higher revenue associated with treating a more appropriate referral. Also, this adds to staffing expenses, equipment expenses, space expenses, and waiting times to others’ visits. Causes include poor communication between the referring and referral practice.
  6. Unnecessary human motions: Poor layout of the office can force staff to travel unnecessary distances, reducing productivity, and contributing to staff fatigue as well as musculoskeletal problems. For example, having work-up, exam, testing and treatment rooms in nonsequential, noncontiguous, and/or distal locations can cause this form of waste. Poor protocols or communications can also contribute to this form of waste; for example, if a patient is required to have a test that should have already been performed (ie, “going backwards” in the patient flow path), this would contribute to this form of waste.
  7. Defects: Poor medical or surgical outcomes represent waste from product defects. Although these are sometimes unavoidable, they do require retreatment, requiring additional time and resources, and likely result in disability for the patient. Avoidable causes include lack of process controls and error proofing (incorrect surgical site, incorrect procedure, incorrect medication, incorrect dose). Additional causes include poor communication and improper training.


Figure 1 shows Lean and Six Sigma processes in outpatient care, involving multiple steps, which depend on the patient type (new vs established) and visit type (examination and/or testing and/or treatment). There are multiple processing steps during the visit, involving initial check-in at the reception desk, initial paperwork, work-up by the technician, examination by the physician, diagnostic testing, explanation by the physician, possible same-day treatment, and check-out. From an operations standpoint, processing a patient through an office visit represents creation of relative value units as the patient progresses along a production path of receptionists, waiting rooms, patient care assistants, physician examination, diagnostic tests, and treatment.

In this case, task B consumes the greatest task time in clinic, creating a bottleneck of waiting patients, which represents waste. Task B also determines the clinic throughput, the amount of time between completion of visits, which is known as the process cycle time and equals the bottleneck task time of 6 minutes. In this example, hiring another worker for task B reduces its task time to 3 minutes, and the bottleneck shifts to task A, which has a task time of 5 minutes. The clinic’s process cycle time improves to 5 minutes, and the clinic’s process output improves from 10 patients per hour to 12 patients per hour. Task A can then be targeted for improvement to continue to improve clinic process flow.

In a recent study we conducted, Lean Six Sigma process improvement was employed in a typical retina clinic setting to decrease patient visit time, demonstrating that this approach can yield enormous aggregate improvement in health care4 In this study, process flow maps were created to determine the most common care pathways within clinic. Three months of visits from the electronic medical record system, which tracks patient visit times at each process step in the office were collected.

Care tasks and care pathways consuming the greatest time and variation were objectively identified and modified. Follow-up analysis from 6 weeks of visits was conducted to assess and quantitate improvement. This analysis revealed that nearly all the patients took 1 of 5 paths through the office. This facilitated redesign of patient flow to eliminate some waiting room time by having staff members immediately start patients into 1 of those 5 paths. The follow-up analysis revealed a statistically significant decline in mean visit time by 18% and in visit time standard deviation by 4.6%. There was no reduction in patient–provider contact time and the patient and employee satisfaction scores improved as well. The benefits multiply when considered in the aggregate. A typical clinic schedule of 40 patients per day translates to approximately 10,000 patient visits per year, saving more than 3,000 hours per year from the improvements.

Basic process improvement in the retina clinic involves the following:

  1. Diagram patient flow pathways: Patient flow pathways are diagrammed to characterize the patient’s journey through the clinic. The major pathways are identified and assessed to determine whether they run in series, parallel, or combination with some common process steps; these common steps have greater risk of bottleneck formation. For example, if the new patient pathway, established follow-up patient pathway, and intravitreal injection patient pathway all converge on an OCT testing station, then the potential for bottleneck formation at the OCT testing station is high.
  2. Assess pathways for waste: Using a Lean approach, the pathways are assessed to potentially eliminate waste such as unnecessary or excessive staff, patient movement, or redundant steps.
  3. Measure waiting times: Using a Six Sigma approach, prolonged waiting times are defined as a defect and then measured, either through automated systems such as the EMR or through a manual approach. Wait times are longest at bottlenecks, which are targeted for improvement.
  4. Measure patient flow times: Patient flow time includes not only patient care tasks, but also patient waiting time. The patient flow times are analyzed to objectively identify the tasks and care pathways consuming the greatest times and variation, as well as the greatest accumulated time and variation. These tasks and pathways are prioritized for potential operational improvements.
  5. Implement improvements: Operational improvements may include office reconfiguration to eliminate unnecessary staff or patient movement, or additional exam rooms or staff to increase capacity at bottlenecks. Schedule optimization around room utilization, staffing, or patient characteristics can also enhance patient flow. Commonly utilized problematic flow pathways can be improved by implementing a separate dedicated process flow, which eliminates sharing of steps with other separate pathways. For example, the intravitreal injection patient pathway would utilize its own waiting room area, staff, exam rooms, and diagnostic equipment; these enhancements would decrease variation and limit bottleneck formation.


Lean Six Sigma process improvement applied to intravitreal medication inventory management represents another important advance in retina practice. Intravitreal injections can involve the majority of visits and employ selection from several medications to treat multiple conditions. Patients must receive the correct medication, in the correct eye, prior to medication expiration date, for the correct diagnosis. These medications are expensive and require preauthorization. Practices must properly order, inventory, store, and bill for these medications. These medications must be stored in a refrigerator and expiration dates must be monitored. If errors in this supply chain process occur, the practice incurs significant costs.

Inventory management strategy has evolved significantly in health care (Table 1). In retina practices, 2 systems are increasingly used to facilitate inventory management. For the CubixxMD system ( ), each dose of medication is labeled with an RFID tag that is coupled with an RFID system build into a specially designed refrigerator, which is locked, and requires codes that identify the individual who opened the refrigerator as well as the patient (requiring a patient chart number). The RFID system tracks the medication that was taken, which is automatically entered into the electronic medical record system and billing system (along with the lot number, in case of drug recalls, infection, etc). The system notifies the user of temperature deviations, upcoming expirations, and low inventory. Automated reordering can be performed to maintain a steady stock based on known usage patterns. Inventory processes can be monitored via an internet based application. The Podis system ( ) is similar, but it uses bar codes instead of RFID tagging. Data surrounding usage, when aggregated, has tremendous value for vendors, as ordering can be automated to “push” inventory through the supply chain.

Table 1: Inventory Management Strategies
CUSTOMER-OWNED Customer-owned & customer-managed Customer-owned & vendor-managed
CONSIGNMENT Consignment & customer-managed Consignment & vendor-managed

Inventory management is evolving in health care from a traditional customer-owned and customer-managed strategy to a customer-owned and vendor-managed strategy to reduce waste, lower costs, and improve quality. Consignment inventories are typically employed for high-value products used in the operating room. With a consignment strategy, supply chain risks, such as spoilage and expiration, are shifted to the supplier. Vendor management can lower labor and other inventory holding costs for the health provider system. Product availability often improves. Evolving technology for inventory management can improve timing and accuracy surrounding order fulfillment, while also lowering costs.


Reduction in patient visit times and improved inventory management leads to several potential measurable business benefits including enhanced patient satisfaction, fewer medication and billing errors, and the potential for increased revenue through more efficient throughput. The Lean Six Sigma process employed in our study can be applied to other clinics in which waiting times and inventory management are problematic. If similar approaches were implemented across entire institutions, the benefits aggregate even further, improving health care delivery and satisfaction — at a marginal cost.

In summary, increasingly elderly populations, insured by taxpayer-funded Medicare programs, are undergoing increasingly complex care in an increasingly outpatient environment with prolonged waiting times. Lean Six Sigma process improvement concepts can enhance patient satisfaction and clinic capacity with minimal increase in cost. This advances the quality of care with concurrent cost containment, the holy grail of health care. RP


  1. Keenan TD, Kelly SP, Sallam A, et al. Incidence and baseline clinical characteristics of treated neovascular age-related macular degeneration in a well-defined region of the UK. Br J Ophthalmol. 2013;97(9):1168-1172.
  2. McMullen M, Netland PA. Wait time as a driver of overall patient satisfaction in an ophthalmology clinic. Clin Ophthalmol. 2013;7:1655-1660.
  3. Pyzdek T, Keller PA. The six sigma handbook. Fourth ed. 2014, New York: McGraw-Hill Education.
  4. Ciulla T, Tatikonda M, ElMaraghi Y, et al. Lean Six Sigma techniques to improve ophthalmology clinic efficiency. Retina. 2017. [Epub ahead of print.]