RVO is the world's second most blinding retinal vascular disease after diabetic retinopathy, with a prevalence of approximately 0.77% [15]. VEGF factor plays an essential role in developing RVO, making the intravitreal injection of anti-VEGF drugs the first-line treatment for RVO-ME patients [16]. During the initial phase of anti-VEGF, most patients have a positive response, but some patients still need repeated treatment to block disease progression and achieve the stable vision. Patient compliance determines the frequency of treatment and follow-up. Anti-VEGF treatment improves visual acuity and anatomy at six and 12 months in RVO-ME patients [17]. At least six months of follow-up is required to determine treatment effects and adverse effects. This presents that LTFU in RVO-ME patients is an essential factor affecting their visual quality of RVO-ME. We frequently use a 3 + PRN regimen, combined with research practice [11–14], and define RVO-ME patients who do not attend outpatient follow-up for more than six months as lost to follow-up.
This study analyzed the causes of lost visits to LTFU after intravitreal injection of anti-VEGF for RVO-ME, as well as the effect of LTFU on the prognosis of RVO-ME patients who received intravitreal injection of anti-VEGF. Our study demonstrated that 49.2% of patients would LTFU after anti-VEGF treatment. Among 125 LTFU patients, 82.4% of RVO-ME patients did not return more than six months after the last injection, whereas only 17.6% of patients treated with intravitreal anti-VEGF injections returned more than six months after LTFU. Currently, irregular treatment of RVO patients has been reported in other countries. Kelkar et al. [18] retrospectively studied the compliance of patients with DME, AMD, and RVO in Indian society who received anti-VEGF therapy, presenting that 50% of the patients did not revisit the clinic for more than a year. Another research team published a retrospective cohort study [10], revealing that 25.4% of RVO-ME patients treated with intravitreal anti-VEGF injections developed LTFU in at least one of the five years after receiving intravitreal injections. The difference in the rate of loss to follow-up may be related to the local level of care, infrastructure, and patients' willingness to visit the clinic.
In this study, the common causes of LTFU were "no improvement in vision" and "transport inconvenience." The number of injections before LTFU was a risk factor. This agrees with Kelkar et al. [18], who presented that the common causes of LTFU were "no improvement in vision" and "non-affordability." In contrast, most patients had LTFU after one injections, suggesting that the causes of LTFU are related to the number of injections patients receive. "Financial reasons" may be related to the patient’s inability to pay the high cost and refusal to continue treatment without significant improvement in visual acuity. However, Yang et al. [11] indicated "noncompliance" as the primary reason, which may be related to the inclusion of RVO patients with a mean age of 60.2 ± 7.2 years and poorer compliance in middle-aged and elderly people. A retrospective study by Gao et al. [10] indicated that race, age, type of RVO, and distance from the hospital were risk factors for LTFU. This differs from the present study’s results, probably due to ethnicity and sample size differences.
There are various treatment options for RVO, such as 1 + PRN, 3 + PRN, and TAE. Regardless of the treatment option, treatment frequency is fundamental in the first year. The number of injections with the PRN regimen in RVO patients is approximately seven to eight in the first year [20, 21]. Additionally, RVO treatment is complemented by follow-up, with approximately half of RVO patients requiring long-term treatment, particularly CRVO patients who may require more frequent follow-up visits [22, 23]. However, patients who have received more than three injections frequently lose confidence in continuing treatment due to "no improvement in vision." In contrast, others choose LTFU after one treatment for "financial reasons," perhaps because their vision does not meet the requirements for special drug medical insurance or their families cannot afford the high cost of treatment, thus abandoning the treatment. Some elderly patients refuse to return to the hospital due to their personalities or are non-accompanied by family members. Distance is also the reason for LTFU for some patients. Some patients do not visit the hospital within the prescribed time or visit other hospitals because they live in remote towns or are more than 20 km away from the hospital due to the need for frequent follow-up visits. These reasons can lead to treatment interruptions and missed optimal treatment time for RVO-ME patients, posing a significant challenge to standardizing treatment for RVO-ME patients.
One study [19] exhibited that 70% of RVO patients had deteriorating vision in the affected eye after long-term LTFU recovery, with only 33% recovering to pre-LTFU levels after restarting anti-VEGF therapy. Another study reported [11] that CMT was measured in the affected eyes of RVO patients at a follow-up visit after treatment interruption. All eyes had more significant ME than baseline. Consistent with our analysis of the prognosis of RVO patients who returned after LTFU, the current study confirms that the BCVA and CMT of the affected eye at the time of the return visit were worse in RVO patients after LTFU compared to before LTFU. This also demonstrates the importance of regular follow-up and continuous treatment to recover visual acuity and anatomical form. We discovered that 50% of the revisiters had no complications, with the analysis presenting an improvement in their BCVA and CMT than the initial treatment, the CMT of these patients being less than 250 µm. The visual outcome and anatomical morphology improvement may have prevented this patient group from continuing to LTFU, but 50% of the patients still had varying degrees of complications, resulting in vision deterioration and return to the clinic. Our analysis of the best visual acuity at the return visit after LTFU revealed that logMAR at the initial visit, CMT at the initial visit, CMT before the LTFU, and CMT after the LTFU were all factors influencing the visual acuity at the return visit. A retrospective study discovered [24] that untreated BCVA was a predictor of visual quality in CRVO patients receiving anti-VEGF therapy. Sen et al. [25] similarly confirmed that baseline BCVA and CMT affect final BCVA after anti-VEGF therapy, with baseline BCVA being the known predictor of the final visual outcome. Similarly, the results of a retrospective study conducted by Salabati et al. [19] confirmed the above. However, Yang et al. [11] demonstrate a correlation between visual prognosis and LTFU length. Pre-LTFU and post-return CMT affect visual acuity at the final return visit has not been explored. This is the first to reveal that four major factors, baseline visual acuity and CMT, pre-LTFU, and post-LTFU CMT, can affect visual acuity at the return visit after RVO-ME patients receive anti-VEGF treatment for LTFU. It provides a new theoretical basis for regular follow-up and on-demand anti-VEGF treatment of ME in RVO-ME patients and strong evidence that reducing CMT in RVO-ME patients can improve visual quality. Earlier detection, better diagnosis, faster treatment, and regular follow-up should be carried out to avoid further deterioration of visual quality and missing the best treatment time to save vision in RVO-ME patients. Our study has several limitations. First, this was a retrospective study which might be subject to selection bias. Since we could only collect information on patients who visited our hospital instead of all hospital visits in our area, some patients might have visited other hospitals for personal reasons. Consequently, we lost the follow-up management of this patient group. Second, this was a single-center clinical study with a small included sample size and a lack of support from the results of multicenter clinical studies, limiting our further analysis of the follow-up treatment of patients who returned for a second visit. Therefore, we can combine multicenter studies while expanding the sample size to improve the study results further in the future. Third, we request patients to choose only one reason for LTFU, while the telephone questioning style is subjective; therefore, patients avoid the question and prefer a more conservative response.