The Relationship of Travel Distance to Postoperative Follow-up Care on Glaucoma Surgery Outcomes

Abstract

Purpose:

To investigate the relationship of patient travel distance and interstate access to glaucoma surgery postoperative follow-up visit attendance.

Methods and Participants:

Retrospective longitudinal chart review of all non-institutionalized adult glaucoma patients with initial trabeculectomies or drainage device implantations between April 4, 2014 and December 31, 2018. Patients were stratified into groups based on straight-line distance from residence to UNC-Chapel Hill Kittner Eye Center and distance from residence to interstate access. Corrective procedures, visual acuity (VA), appointment cancellations, no-shows, and insurance data were recorded. Means were compared via two-tailed Student’s t-test, Pearson’s chi-square, analysis of variance, and multivariate logistical regression determined odds ratios (OR) for loss to follow-up.

Results:

199 patients met all inclusion criteria. 6-months postoperatively, patients > 50 miles from clinic had greater odds of loss to follow-up compared to patients < 25 miles (OR 3.47 95% CI 1.24–4.12, P < .05). Patients > 50 miles from clinic had significantly more missed appointments than patients 25-50 miles away, and patients < 25 miles away (P = .008). Patients > 20 miles from interstate access had greater loss to follow-up than those < 10 miles (t(150) = 2.05, P < .05). Mean distance from clinic was 12.59 miles farther for patients lost to follow-up (t(197) = 3.29, P < .01). Patients with Medicaid coverage had more missed appointments than those with Medicare plans (t(144) = −2.193, P < .05).

Conclusions:

Increased distance from clinic and interstate access are associated with increased missed appointments and loss to follow-up. Glaucoma specialists should consider these factors when choosing surgical interventions requiring frequent postoperative evaluations.

PRÉCIS

This study addresses the paucity of literature examining glaucoma patients’ distance from clinic on postoperative follow-up outcomes. Greater distance from clinic was associated with higher likelihood of loss to follow-up and missed appointments.

INTRODUCTION

The current standard of treatment of glaucoma is the reduction of intraocular pressure (IOP) through topical medications, laser, and surgery to maintain quality of life and reduce vision loss. Surgical interventions such as trabeculectomy and tube shunt implantations require frequent follow-up and monitoring to assess their function, evolution, and possible complications.^1-4 The American Academy of Ophthalmology’s (AAO) Preferred Practice Pattern Guideline attributes long-term surgical success to follow-up retention, but lack recommendations considering the follow-up demands for each procedure and the adverse outcome risks for patients who may be more susceptible for loss to follow-up due to increased travel distance.²

Following trabeculectomy or tube shunt placement, surgical maturation, evidence of complications, and IOP progress are typically assessed in clinic with frequent postoperative visits. Additional appointments are scheduled at the surgeon’s discretion until expected surgical outcomes have been met.^3,5-7 Trabeculectomy, as compared to other glaucoma procedures, typically has more follow-up care and the possible need for medical or procedural intervention or surgical revision.^8,9

Investigating the relationship of travel distance to postoperative follow-up care on glaucoma surgery outcomes can enable specialists to make note of patients’ proximity to follow-up care when deciding a surgical treatment intervention.

The purpose of this study is to identify if patients’ distance to the University of North Carolina at Chapel Hill’s Kittner Eye Center is related to surgical follow-up visit attendance. We hypothesize that increased travel distance is associated with increased missed or canceled appointments and loss to follow-up.

METHODS

Data Source and Study Population

Institutional Review Board approval with informed consent exemption was granted for this retrospective study. This research adhered to the tenets of the Declaration of Helsinki and authors were trained in human subject research ethics by the Collaborative Institutional Training Initiative Program. Through the resources of the North Carolina Translation and Clinical Sciences Institute (NC TraCS), de-identified demographic, clinical, and insurance data from the Carolina Data Warehouse for Health were retrieved. Using the i2b2 application from NC TraCS, we obtained patient data from April 4, 2014 until December 31, 2018 for this longitudinal study. This timeframe allowed us to examine charts of patients who were surgically treated at the Kittner Eye Center of the University of North Carolina at Chapel Hill and compare distances between patient address to clinic.

The Kittner Eye Center is a tertiary academic referral center located in central North Carolina and serves a diverse and widespread patient population traveling from rural North Carolina for glaucoma management.

Study Design

Using the i2b2 interface, we specified International Classification of Diseases (ICD) 9 and 10 codes for glaucoma, age, Current Procedural Terminology (CPT) codes for relevant glaucoma surgical procedures, and clinic location. When establishing a patient set, patients with greater than one ICD or CPT code were only counted once via i2b2.

The inclusion criteria specified established diagnoses of glaucomas under ICD-9: 365 and ICD-10: H40. Specifically, we included ICD-10 codes for open-angle glaucoma, primary angle-closure glaucoma, glaucoma secondary to eye trauma, glaucoma secondary to eye inflammation, glaucoma secondary to other eye disorders, glaucoma secondary to drugs, other glaucoma, unspecified glaucoma, and glaucoma in diseases classified elsewhere. We also included ICD-9 codes for corticosteroid-induced glaucoma, glaucoma associated with congenital anomalies, dystrophies, and systemic syndromes, glaucoma associated with disorders of the lens, and glaucoma associated with other ocular disorders in addition to all classifications that were transferred to ICD-10.

The exclusion criteria for subjects included ICD-9: 365.0 borderline glaucoma and ICD-10 H40.00 preglaucoma. Patients under 18 years of age or with unknown ages were excluded from the data. Institutionalized patients or those with managed care at skilled nursing facilities, penal systems, retirement communities or other nursing homes were excluded based on the potential for confounding variables. Patients without listed home addresses or those who transferred care to other institutions or providers were excluded during chart review. Appendix A (see document, Supplemental Digital Content 1, http://links.lww.com/IJG/A427) contains a full list of exclusion and inclusion criteria. Included patients happead initial glaucoma surgeries performed from April 4, 2014 to December 31, 2018. The included CPT code for tube shunt placements was: 66180: Aqueous shunt to extraocular equatorial plate reservoir, external approach with graft. Trabeculectomy CPT codes were: 66170: Fistulization of sclera for glaucoma; trabeculectomy ab externo in absence of previous surgery, 66172: Fistulization of sclera for glaucoma; trabeculectomy ab externo with scarring from previous ocular surgery or trauma (includes injection of antifibrotic agents), and 66183: Insertion of anterior segment aqueous drainage device, without extraocular reservoir, external approach (i.e. Ex-PRESS Shunt).

Revision surgery CPTs for both tube shunt placement and trabeculectomy include: 66185: Revision of aqueous shunt to extraocular equatorial plate reservoir; with graft, and 66250: Revision or repair of operative wound of anterior segment, any type, early or late, major or minor procedure.

199 patients met the above inclusion criteria and their charts were reviewed for demographics, initial surgery CPT, surgery date, insurance coverage at the date of service, tube shunt type (if applicable), laterality, attending surgeon, preoperative IOP, and postoperative IOPs at one day, one week (5-9 days), one month (3-5 weeks), three months (± 2 weeks), and six months (± 3 weeks). Preoperative uncorrected visual acuity via Snellen chart examination was compared during chart review to six months postoperative visual acuity. A visual acuity decrease of ≥ 2 lines was classified as “Worsened”. Patients with a decline from counting fingers at six feet to counting fingers at four feet was considered a clinically significant decline. A change from count fingers to hand motion, hand motion to light perception, or light perception to no light perception was also considered clinically significant worsened visual acuity. Visual fields were tested via confrontation for most patients and perimetry was sporadic. Due to the inconsistent nature and mixed modalities of pre- and postoperative visual field examinations, these data were not included for statistical analysis.

Number of corrective and revision surgeries were recorded. Additional tube shunt placements or trabeculectomies within the global period, 90 days of the initial surgery, were considered to be corrective procedures. Additional tube shunt placements or trabeculectomies of the same eye beyond 90 days were considered to be surgical treatment for glaucoma disease progression and were not included in the data analysis.

Each patients’ office visit notes and telephone encounters were reviewed across the six-month follow-up period. “Lost to follow-up” status was designated to patients who missed or did not schedule postoperative follow-up appointments as recommended by the provider and did not return to clinic in the six-month postoperative period. Those who were suspected of being lost to follow-up were carefully reviewed for any indication of transfer of care to another provider (e.g. patient or outside provider requests for records). Patients who transferred care without documented approval or recommendation by the surgeon were considered “lost to follow-up”. Patients who transferred care with the provider’s approval or with the appropriate transfer of records were excluded from the study. If at any point the physician documented that a patient could return to clinic as needed and the patient did not schedule further appointments in the six-month postoperative period, the patient was not considered lost to follow-up.

Number of patient-initiated canceled/no-show appointments were recorded using comments provided by administrative encounters (e.g. lack of transportation) excluding provider or clinic-initiated cancellations (e.g. change of operating hours or provider schedule). Patients who canceled appointments and subsequently attended a rescheduled appointment within the time-period for each follow-up interval (e.g. three months ± two weeks) were noted to have “rescheduled” an appointment, and not counted as “missed”. The number of patient-initiated rescheduled appointments was explicitly noted and counted separately from those that were rescheduled from prior no-show appointments.

In addition to the clinical chart review, straight-line (Euclidean) distances from patients’ home addresses to the Kittner Eye Center were measured to create radii of incidence of postoperative complications. Straight-line distance from patients’ home addresses to nearest interstate access was measured to identify groups of patients from rural communities.

Outcome Measures

The patient sample was stratified into three distance radii groups: 0-25 miles, 25.5-50 miles, and greater than 50 miles from home address to Kittner Eye Center. Patients were secondarily stratified into three distance groups from home to interstate access: 0-10 miles, 10.5-20 miles, and greater than 20 miles. Distance and canceled or no-show appointments, loss to follow-up status, visual acuity outcomes, were documented and means compared by two-tailed Student’s t-test, Pearson’s chi-square analysis, and analysis of variance. Odds ratios (OR) were estimated using multivariate logistic regression models for distance from Kittner Eye Center and loss to follow-up, and distance to Kittner Eye Center and number of revision/corrective surgeries. Statistics were completed using R software (version 3.6.3; R Foundation for Statistical Computing, Vienna, Austria) and IBM SPSS® via the NC TraCS Institute.

RESULTS

Of the 199 patients that met inclusion criteria for the study, distances ranged from 0.5 miles to 114 miles from home address to Kittner Eye Center. The map of patient radii of distance from Kittner Eye Center to home addresses is presented in Figure 1. The accompanying table in Figure 1 includes information on percentage of patients lost to follow-up, percentage with worsened visual acuity, and average number of missed appointments between groups. Table 1 displays the demographic data and corresponding p-values the entire study population and distance subgroups, < 25 miles from Kittner Eye Center, 25-50 miles, and > 50 miles respectively. There were no significant differences in demographic proportions between distance groups. Table 2 displays the kind and number of each treatment modality used within each distance subgroup. Table 3 shows the relative percentages of follow-up and visual acuity outcomes for each distance subgroup and surgical treatment modality.

Figure 1.

Map of population home address radii and 6-month postoperative follow-up data.

Table 1.

Demographic Data of Study Population

	Study Population	Patients <25 Miles from Kittner Eye Center	25-50 Miles	>50 Miles	P value
N	199	115	57	27
Average Age (range)	64.94 (22-93)	65.93 (22-93)	64.84 (31-93)	60.89 (32-77)	0.2585
Average Distance from Kittner Eye Center (mi)	25.83	11.99	32	71.74	———
Sex (n)					0.8089
Males	100	59	29	12
Females	99	56	28	15
Race					0.1676
Black/African American	101	60	28	13
White/Caucasian	77	45	21	11
Asian	3	3	0	0
Other	17	7	8	2
American Indian/Alaskan Native	1	0	0	1
Ethnicity					0.1401
Non-Hispanic/Latino	183	109	49	25
Hispanic/Latino	16	6	8	2

Table 2.

Surgical Treatments Performed in Study Population Distance and Treatment Subgroups

Procedure Type
Ahmed® Glaucoma Valve (New World Medical Inc., Rancho Cucamonga, CA, USA)	n = 83
Patients < 25 Miles from Kittner Eye Center	51	(61.4%)
Patients 25-50 Miles	21	(25.3%)
Patients > 50 Miles	11	(13.3%)
Baerveldt Implant (Abbott Medical Optics, Abbott Park, IL, USA)	n = 70
Patients < 25 Miles	36	(51.4%)
Patients 25-50 Miles	21	(30.0%)
Patients > 50 Miles	13	(18.6%)
Trabeculectomy +/− Ex-PRESS Shunt (Optonol, Ltd., Neve Ilan, Israel)	n = 46
Patients < 25 Miles	28	(60.9%)
Patients 25-50 Miles	15	(32.6%)
Patients > 50 Miles from Kittner Eye Center	3	(6.5%)

Table 3.

Follow up and Visual Acuity Outcomes Across Treatment Groups

	Lost to Follow-up (%)	Worsened Visual Acuity (%)
Study Population	20.1	33.2
Patients < 25 Miles from Kittner Eye Center	13.9	31.3
Ahmed	50.0	52.8
Baerveldt	18.8	25.0
Trabeculectomy +/− Ex-PRESS	31.2	22.2
Patients 25-50 Miles from Kittner Eye Center	24.6	35.1
Ahmed	42.9	20.0
Baerveldt	35.7	45.0
Trabeculectomy +/− Ex-PRESS	21.4	35.0
Patients > 50 Miles from Kittner Eye Center	37.0	37.0
Ahmed	60.0	50.0
Baerveldt Shunt	30.0	30.0
Trabeculectomy +/− Ex-PRESS	10.0	20.0

Multivariate logistic regression analyses compared the effect of straight-line distance from home address to the Kittner Eye Center, straight-line distance from home to interstate access, number of corrective procedures, number of rescheduled appointments, treatment type, race, ethnicity, age, sex, and VA decline from preoperative appointment on loss to follow-up. Odds ratios (OR) of loss to follow-up were calculated for each group. Figure 2 is a plot of odds ratios and 95% confidence intervals for loss to follow-up based on tested patient demographic factors. Treatment type (tube shunt versus trabeculectomy), sex, age, and race were not significant predictors of loss to follow-up. A full summary of the loss to follow-up odds ratio data can be found in Table 4.

Figure 2.

Odds ratios for loss to follow up based on patient factors. (*) P < .10, (**) P<.05

Table 4.

Multivariate Logistic Regression Analysis of Factors for Loss to Follow up in Postoperative Glaucoma Patients (n = 199) at a Tertiary Referral Academic Hospital

Factors	Lower	Upper	OR	P value
Rescheduled Appointments (Range from 0-5)	0.069	0.9	0.33	0.086*
>50 Miles from Kittner (vs. <25 Miles from Kittner)	1.24	4.12	3.47	0.013**
Hispanic/Latino (yes vs. no)	0.92	8.72	2.93	0.056*
Race	0.71	2.70	1.37	0.35
Corrective Procedures (Range from 0-3)	0.0065	0.64	0.12	0.049**
Female Sex (yes vs. no)	0.29	1.34	0.626	0.23
Worsened Visual Acuity ≥ 2 lines (yes vs. no)	1.16	5.29	2.46	0.0193**
Age	0.97	1.02	0.99	0.76
Tube Shunt (vs. Trabeculectomy)	0.34	2.45	0.91	0.86

The logistic model revealed that patients living greater than 50 miles from the Kittner Eye Center had increased odds of loss to follow-up in comparison to those less than 25 miles away (OR 3.47 95% CI 1.24–4.12, P < .05). Patients 25 to 50 miles from the Kittner Eye Center were not more likely to be lost to follow-up compared to those living less than 25 miles away (OR 1.58, 95% CI 0.59–4.11, P = 0.35). Straight-line distance from home to interstate access was associated with significantly increased odds of loss to follow-up when analyzed in a logistic model independent of straight line distance from home to the Kittner Eye Center (OR 1.57 95% CI 1.01–2.43, P < .05). When both distances were analyzed together, only straight-line distance from home to Kittner Eye Center was significant.

Additionally, there was incidental evidence that individuals of Hispanic or Latino ethnicity had a marginally elevated, but not statistically significant, OR of being lost to follow-up (OR 2.93 95% CI 0.92–8.72, P = 0.056). Individuals with a reported decrease in uncorrected visual acuity of greater than two lines on Snellen chart from their preoperative appointments and their last attended appointments were found to have increased odds of being lost to follow-up (OR 2.46 95% CI 1.16–5.29, P < .05). There were no significant differences in the number of appointments scheduled between patients who had worsened VA compared to those who did not have VA decline (P > .05). 22 patients underwent at least one corrective procedure, which was associated with significantly decreased odds of loss to follow-up (OR 0.12 95% CI 0.0065–0.64, P < .05). The number of rescheduled appointments did not have the same level of significance for decreasing odds of loss to follow-up (OR 0.33 95% CI 0.069-0.90, P = 0.086).

Pearson’s chi-squared analysis and two-tailed independent samples Student’s t-tests were conducted on multiple outcome data between groups of patients living 0-25 miles from Kittner Eye Center and those living greater than 50 miles away. A chi-square test of independence revealed a significant association between distance from Kittner Eye Center and loss to follow-up (P = 0.016). There was no significant difference between the choice of initial surgical treatment (e.g. tube or trabeculectomy) in the three distance groups from home address to Kittner Eye Center (P = 0.46). A two-tailed test of proportions indicated no significant difference in proportion of patients undergoing trabeculectomy in each home to Kittner Eye Center distance group (P = 0.133). There was no significant difference in amount of corrective procedures done between patients who underwent trabeculectomy versus tube shunt implantation (t(197) = 0.96, MD = 0.06, 95% CI 0.076 to 0.18, P = .34).

Six-months postoperatively, patients residing > 50 miles from Kittner Eye Center were more likely to be lost to follow than patients living ≤ 25 miles from the eye center (t(140)=2.86, P < .01, Mean Difference (MD) = 0.23, 95% Confidence Interval [CI], 0.12 to 0.242). Patients greater than 20 miles from an interstate access had significantly greater loss to follow-up than those less than 10 miles from access (t(150) = 2.05, MD = 0.14, 95% CI 0.14 to 0.26, P < .05). One-way ANOVA with Tukey post hoc analysis revealed a significant difference of means of missed appointments between the three distance groups from home address to the Kittner Eye Center. Patients greater than 50 miles from Kittner had significantly more missed (canceled or no-showed and non-rescheduled) appointments than those 25-50 miles and those less than 25 miles away (P = .008). There was no significant difference in means of missed appointments between the three distance groups from home address to interstate access (P = .91). A comprehensive statistical summary of average missed appointments for both distance groups (1. home address to Kittner Eye Center and 2. home address to interstate access) can be found in Table 5. Similarly, Figure 3 displays the percentages of patients in both distance groups who were retained (not lost to follow-up) between each postoperative follow-up visit over the six-month period. Figure 4 displays the percentages of patients in both distance groups who attended scheduled appointments at each follow-up interval in the six-month postoperative period. In comparison to Figure 3, this figure illustrates the general follow-up adherence patterns in the study population.

Table 5.

ANOVA multiple comparisons of means of missed (cancelled or no-showed, and non-rescheduled) appointments between distance groups.

Kittner Distance Group (mean missed appointments)	Kittner Distance Group Compared	Mean Difference	Std. Error	P value	95% Confidence Interval
					Lower Bound	Upper Bound
0-25 Miles (1.17)	25-50 Miles	−0.195	0.251	0.719	−0.79	0.4
	> 50 Miles	−1.048*	0.331	0.005	−1.83	−0.27
25-50 Miles (1.36)	0-25 Miles	0.195	0.251	0.719	−0.4	0.79
	> 50 Miles	−0.854	0.362	0.05	−1.71	0
> 50 Miles (2.22)	0-25 Miles	1.048*	0.331	0.005	0.27	1.83
	25-50 Miles	0.854	0.362	0.05	0	1.71
Interstate Distance Group (mean missed appointments)	Interstate Distance Group Compared
< 10 Miles (1.39)	10-20 Miles	−0.01	0.277	0.999	−0.66	0.64
	> 20 Miles	0.115	0.286	0.914	−0.56	0.79
10-20 Miles (1.40)	< 10 Miles	0.01	0.277	0.999	−0.64	0.66
	> 20 Miles	0.125	0.335	0.926	−0.67	0.92
> 20 Miles (1.28)	< 10 Miles	−0.115	0.286	0.914	−0.79	0.56
	10-20 Miles	−0.125	0.335	0.926	−0.92	0.67

^*.The mean difference is significant at the 0.05 level.

Figure 3.

Percent of follow-up retention as a factor of distance traveled to Kittner Eye Center and distance to interstate access.

Figure 4.

Percent of patient attendance at each post-operative appointment interval as a factor of distance traveled to Kittner Eye Center and distance to interstate access from home address.

Insurance data were collected and analyzed to investigate the relationship of socioeconomic status on missed appointments and loss to follow-up. At the time of surgery, 114 (57.3%) of the 199 patients were enrolled in Medicare plans, 32 (16.1%) North Carolina Medicaid, 38 (19.1%) private or state employee insurance plans, and 15 (7.5%) were uninsured. On average, patients covered by North Carolina Medicaid had significantly more missed appointments than those with Medicare (t(144) = −2.19311, P < .05, M = 1.03, MD = 0.35, 95% CI, 0.57 to .87). Patients enrolled in Medicaid also had significantly higher rates of loss to follow-up compared to those with Medicare plans (t(144) = −2.444, P < .05, M = 0.38, MD = .20, 95% CI, −.361 to −.038). Patients with Medicaid were, on average, 12.41 miles farther from the Kittner Eye Center than patients with Medicare plans (P < .05, 95%CI 1.084 to 23.740). No significant differences in missed appointments, loss to follow-up, or visual acuity outcomes were found between privately insured patients and those with Medicare or Medicaid (P > .05).

Patients lost to follow-up were a mean distance of 35.89 miles from Kittner Eye Center, which was significantly higher than those not lost to follow-up (t(197) = 3.29, P < .01, M = 25.83, MD = 12.59, 95% CI, 22.8 to 28.9).

DISCUSSION

This study revealed that a significant proportion of patients located over 50 miles away from our clinic and patients located greater than 20 miles from interstate access were lost to follow-up and had a significantly higher number of missed postoperative appointments. Lower socioeconomic status (as estimated by Medicaid coverage) was also associated with increased missed appointments in the six-month postoperative period as well as higher rates of loss to follow-up and increased travel distance to clinic. Patients of all distances were equally likely to undergo trabeculectomy or tube shunt placement, and those with corrective procedures were more likely to adhere to the follow-up schedule. Additionally, patients who had a decline in VA of greater than or equal to two lines from their preoperative visit had higher odds of being lost to follow-up within the six-month postoperative period. Due to variable trends in VA after glaucoma surgery, a study examining long-term follow-up is needed to identify the association between functional visual acuity loss and missed appointments. ^20-22

Analyzing the number of attended rescheduled appointments allowed us to quantify a patient’s likelihood to follow the six-month postoperative follow-up course commonly seen in preferred practice guidelines, clinic practices, and related studies on surgical glaucoma management.^{2, 8, 21, 23} Many patients in this study were instructed to return to care approximately five times within the six-month follow-up period per physicians’ office visit notes. Because of this, there were no significant differences in the number of appointments anticipated to be scheduled for each patient, and missed appointments were the primary dependent variable for each subgroup of patients.

Over 40% of our study population was located greater than 25 miles from the Kittner Eye Center in Chapel Hill, North Carolina suggesting that a large, rural population beyond the Raleigh-Durham metropolitan area is served. Straight-line distance allowed us to reduce potential confounding variables relating to traffic patterns, road closures, individual access to public transport service routes, and patients’ choices for routes to clinic. The use of straight-line distance from patients’ addresses to healthcare services to estimate health outcomes and follow-up data has been validated in multiple metanalyses, epidemiological, and clinical studies.^24-27

Follow-up retention is integral to the long-term goals of glaucoma care, but the data suggest that distance is a barrier for patients. Our study supports the findings of prior interdisciplinary follow-up outcome literature, namely that distance is a significant predictor for loss to follow-up and increased appointment cancellations.^8-16 Our findings expand upon previous literature by suggesting long-term follow-up retention in a six-month postoperative period is affected by distance to clinic, distance to interstate access, functional VA loss, and SES.

The small sample of patients living greater than 50 miles from the Kittner Eye Center limits the ability to generalize the statistical results of follow-up outcomes to all patients commuting long distances. Specifically, when distance from interstate access and distance from the Kittner Eye Center were analyzed together in the logistical model, the distance to Kittner Eye Center was a greater predictor of loss to follow-up. This is likely due to the broader range of distances represented in the sample of patients in the “greater than 50 miles to Kittner Eye Center” distance group (50.5 miles to 114 miles) compared to the “greater than 20 miles to interstate access” distance group (20.5 miles to 34 miles). This result suggests that, while rurality is a predictor of follow-up adherence, straight-line distance to clinic has greater statistical influence. A larger sample of rural patients greater than 20 miles from interstate access and patients greater than 50 miles from clinic could help ameliorate this statistical disparity.

Patients’ insurance coverage was noted and analyzed for follow-up adherence outcomes as a metric for retrospectively evaluating socioeconomic status (SES). We found significant relationships suggesting that patients with financial need-based North Carolina Medicaid coverage were, on average, more likely to be lost to follow-up, and had more missed appointments within the six-month follow-up period. This is likely a multifaceted issue wherein patients with Medicaid may have to commute a greater distance to access an in-network glaucoma surgeon and may face greater follow-up limitations due to the financial burden of travel. Other possible contributing factors to follow-up nonadherence include barriers such as the inability for patients or caregivers to take time off from work or afford transportation costs and insurance expenses. These systemic predictors of health outcomes are difficult to assuage in a single clinic setting. Conditions such as uncorrectable low vision, dementia, fatigue, and systemic comorbidities significantly impacting patients’ health may also prohibit follow-up adherence, and these barriers should be considered by clinicians considering surgical interventions. In a study in rural China, simple interventions such as text reminders and distribution of free postoperative drops were sufficient to increase postoperative surgical follow-up, indicating either proactive provider-patient interaction and incentivization as effective means to remedy postoperative visit compliance.¹⁷

Bhargava et. al examined patients’ views on glaucoma surgery follow-up care and found that they prefer to travel short distances and to be seen by a physician (as opposed to an advanced practice provider).¹⁸ The current body of ophthalmological distance to follow-up literature has examined the attrition rates and clinical characteristics of patients who are lost to follow-up in ophthalmology clinics in developing nations.^11-16 Ashaye et al. retrospectively examined the specific characteristics of follow-up attrition in a Nigerian glaucoma clinic. They found that male sex, traveling distance, ophthalmic polypharmacy, patients with mild to moderate glaucoma, and those without a significant family history of vision loss were more likely to be lost to follow-up. ¹⁵ In India, Gupta et al. found that awareness of glaucoma disease progression, close proximity, and higher monthly income were associated with higher follow-up compliance.¹⁶ They also found that 88% of patients who dropped out incorrectly believed that surgery was curative for glaucoma.

Similar studies examined postoperative complications following cataract procedures in pediatric and adult populations in Mexico, sub-Saharan Africa, India, and South Asia. These have suggested that traveling distance is positively correlated with follow-up attrition.^11-16 Prior research has provided an epidemiological framework for this follow-up data study, but the cultural and resource variations between populations warrant a more generalizable sample for glaucoma specialists in the United States.

There is a scarcity of United States-based follow-up studies in ophthalmology. In 2005, Lara et. al similarly responded to the shortage of published data on factors contributing to patient follow-up adherence in regard to the American Society of Bariatric Surgery’s postoperative follow-up recommendations. They found that travel distance did not affect follow-up attendance at early postoperative appointments, however, they found that three-month and nine-month postoperative appointment attendance was negatively affected.¹⁹ Glaucoma and bariatric surgery both require long-term postoperative monitoring for outcomes and complications. Postoperative follow-up appointment retention studies can help quantify the importance of the follow-up schedule, to what extent access to care affects long-term outcomes, and identify future areas for intervention.

Due to the frequency of required surgical follow-up visits and magnitude of sight-threatening complications that may occur, the surgeon must consider the risks and benefits of surgical treatments for each individual patient. This complexity in surgical glaucoma care warrants further investigation into patient-specific factors that may help the surgeon decide on optimal management. We would suggest that these risks and benefits be weighed against the likelihood of patients maintaining follow-up visits and that the distance a patient must travel to maintain this care is an important factor that should be considered.

While this retrospective study decreases the potential for observer bias (Hawthorne effect) and examines recent outcomes of a large academic ophthalmology practice, there exist inherent limitations due to the design. Inclusion criteria regarding diagnoses, procedures, and strict home address requirement helped to reduce confounding variables related to treatment plans, and managed medical care. Institutionalized patients (e.g. those residing at skilled nursing facilities, assisted living communities, prisons, and psychiatric hospitals) may have greater adherence to follow-up appointments because they have hired professionals to arrange appointment scheduling and transportation. Another limitation of the study was due to bias. One of the treating surgeons suspected the influence of travel distance to follow-up care and therefore tended to choose tube shunt surgery for patients who were located far from the treatment center.

Additionally, although there is extensive documentation between provider networks in the electronic health records, it is possible that patients returned to referring providers or initiated care with a different practice. This could potentially result in the inclusion of patients who were analyzed as being lost to follow-up but were still receiving care. The effects of this possibility were moderated statistically through a multivariate logistic regression that would have pushed means toward the null hypothesis, which was rejected. Monitoring uncorrected visual acuity is another limitation of the study. Best-corrected visual acuity may be a more globally representative parameter to measure the evolution of functional ability. Patient presentations for glaucoma surgery may vary from longstanding uncontrolled IOP with gradual VA decline to those with acutely elevated IOP with vision loss independent of the follow-up course.

This study suggests that patients living greater than 50 miles away from follow-up care have increased follow-up cancellation or no-show rates. We speculate that the association between successful follow-up and postoperative outcomes is even more important in the setting of surgical techniques that require close monitoring and more frequent intervention such as trabeculectomy, which should be specifically examined in future investigations. Patients living greater than 50 miles from follow-up care at the treatment center or greater than 20 miles from interstate access were more likely to be lost to follow-up. This finding has important implications for rural populations being treated for glaucoma. In contrast, many patients in the study commuted 20-40 miles from other metropolitan areas while having closer access to the interstate, and these populations demonstrated superior follow-up retention. This suggests that patients commuting from rural areas, where there is a paucity of medical care and public transportation, and higher rates of poverty are particularly vulnerable to complications and attrition during the postoperative follow-up period.²⁸ Patients who underwent corrective procedures within 90 days of the original surgical intervention demonstrated a significantly decreased likelihood of being lost to follow-up. A prospective investigation is would enable researchers to contact lost to follow-up patients and their referring providers to identify specific barriers to care and to better understand treatment courses, disease progression, and other reasons for not returning to the Kittner Eye Center.

The results of this study suggest glaucoma specialists should make note of patients’ proximity to follow-up care when deciding a surgical treatment intervention. Further studies can explore specific factors contributing to follow-up attrition, follow-up scheduling guidelines, and potential telemedicine or educational strategies to improve postoperative follow-up retention.

Supplementary Material

Supplemental Content: Appendix A

Supplemental Digital Content 1: SCD Appendix A 6-13-20.pdf