Association between tear meniscus dimensions and higher-order aberrations in patients with surgically treated lacrimal passage obstruction

To analyze the relationship between tear meniscus dimensions and higher-order aberrations (HOAs) in patients with lacrimal passage obstruction using anterior segment optical coherence tomography (AS-OCT). This study was a retrospective observational study of 71 eyes of 49 patients with lacrimal passage obstruction. These patients received sheath-guided dacryoendoscopic probing and bicanalicular intubation (SG-BCI) at Toyama University Hospital between August 2020 and October 2021. Using AS-OCT, tear meniscus height (TMH), tear meniscus area (TMA), and total corneal HOAs values were measured before and after surgery. Surgical success was achieved in 69 eyes (97.1%). At the final observation, 62 eyes showed lacrimal patency (89.8%). The preoperative TMH, TMA, and HOAs values were 1.55 ± 0.96 mm, 0.11 ± 0.14 mm2, and 0.37 ± 0.27 µm, respectively, and the final postoperative TMH, TMA, and HOAs values were 0.97 ± 0.74 mm (p < 0.0001), 0.06 ± 0.11 mm2 (p = 0.02), and 0.29 ± 0.16 µm (p = 0.001), respectively. The results showed a significant improvement. The changes in HOAs before and after surgery were positively correlated with the changes in TMH (r = 0.3476, p = 0.0241) and TMA (r = 0.3653, p = 0.0174). SG-BCI for lacrimal passage obstruction resulted in a significant decrease in measured HOAs. The decrease in HOAs was correlated with decreases in tear meniscus dimensions.


Introduction
Lacrimal passage obstruction is a common disease in the field of ophthalmology and is caused by inflammation, trauma, neoplasia, or infection of the lacrimal passage [1]. Lacrimal passage obstruction has been reported to cause a variety of symptoms, including epiphora, blurred vision, ocular discharge, conjunctivitis, and blepharitis [2], as well as reduced visionrelated quality of life (QOL) [3][4][5][6]. Therefore, treatment of lacrimal passage obstruction is considered important to improving visual function and QOL.
In the treatment of lacrimal passage obstruction, dacryocystorhinostomy (DCR), in which a new passage is made between the lacrimal sac and the nasal cavity, has a long history and is considered to be a curative treatment. Recently, bicanalicular intubation

Abstract
Purpose To analyze the relationship between tear meniscus dimensions and higher-order aberrations (HOAs) in patients with lacrimal passage obstruction using anterior segment optical coherence tomography (AS-OCT). Methods This study was a retrospective observational study of 71 eyes of 49 patients with lacrimal passage obstruction. These patients received sheathguided dacryoendoscopic probing and bicanalicular intubation (SG-BCI) at Toyama University Hospital between August 2020 and October 2021. Using AS-OCT, tear meniscus height (TMH), tear meniscus area (TMA), and total corneal HOAs values were measured before and after surgery. Results Surgical success was achieved in 69 eyes (97.1%). At the final observation, 62 eyes showed lacrimal patency (89.8%). The preoperative TMH, TMA, and HOAs values were 1.55 ± 0.96 mm, 0.11 ± 0.14 mm 2 , and 0.37 ± 0.27 µm, respectively, and the final postoperative TMH, TMA, and HOAs values were 0.97 ± 0.74 mm (p < 0.0001), 0.06 ± 0.11 mm 2 (p = 0.02), and 0.29 ± 0.16 µm (p = 0.001), respectively. The results showed a significant improvement. The changes in HOAs before A. Taniguchi · T. Yunoki (*) · T. Oiwake · A. Hayashi Departments of Ophthalmology, Graduate School of Medicine and Pharmaceutical Sciences, University of Toyama, 2630 Sugitani, Toyama 930-0194, Japan e-mail: yunokiki@med.u-toyama.ac.jp (BCI) has been introduced as an alternative to DCR for lacrimal passage obstruction, but its success rate is still low compared to DCR [7][8][9][10][11]. However, BCI has the advantage of being less invasive, and recently the use of dacryoendoscopes has improved treatment outcomes [12,13]. Furthermore, the sheathguided dacryoendoscopic probing and intubation technique for BCI (SG-BCI) has improved the safety and success rate of BCI, with a reported postoperative patency rate of 88.7% [14]. Thus, BCI has become an important therapeutic choice for the treatment of lacrimal passage obstruction.
The quality, quantity, and properties of the tear film are known to affect visual function [15]. Therefore, in lacrimal obstruction, observation of the tear meniscus is an important index for therapeutic evaluation. Recently, quantitative and noninvasive assessment of the tear meniscus has been performed using anterior segment optical coherence tomography (AS-OCT) [16][17][18]. Tear volume is thought to affect visual function. Functional visual acuity, contrast sensitivity, and higher-order aberrations (HOAs) have been reported as indicators that reflect the ocular surface conditions impacted by tear meniscus dimensions [19][20][21][22]. In patients with lacrimal passage obstruction, normalizing the tear meniscus through surgical intervention is expected to result in good visual function.
In this study, we performed SG-BCI on patients with lacrimal passage obstruction, evaluated tear meniscus dimensions using AS-OCT, and analyzed the relationship between tear meniscus and HOA measurements, which are important indicators affecting visual function.

Subjects
Between August 2020 and October 2021, 71 eyes of 49 patients with lacrimal passage obstruction who underwent SG-BCI at Toyama University Hospital were included in this study. A lacrimal irrigation test was performed on patients who were aware of epiphora, and patients with no passage were diagnosed as having lacrimal passage obstruction. Patients with functional epiphora (i.e., without a lacrimal duct obstruction), lacrimal canaliculitis, congenital lacrimal duct obstruction, and previous lacrimal duct surgery were excluded. The study was approved by the Institutional Review Board of University of Toyama (No. R2021145). All procedures conformed to the tenets of the Declaration of Helsinki. Written informed consent was obtained from all patients after they had received an explanation of the study procedures.

Treatment protocols
Surgical treatment was performed by one of the authors (TY). SG-BCI was performed in all cases. This technique does not involve blind manipulation using a dacryoendoscope and has been reported to be safe and effective [14]. Topical anesthesia and infratrochlear nerve block were achieved by 2% lidocaine. After dilating the upper and lower lacrimal puncta with a dilating needle, an 18-gauge plastic cannula (Terumo Co., Ltd., Tokyo, Japan) was attached to a dacryoendoscope (Fibertech Co., Ltd., Tokyo, Japan) as a sheath and inserted through the lacrimal punctum. The sheath-guided dacryoendoscope was advanced into the lacrimal canal, and the sheath was used to push through the stenotic site. When it reached the nasal cavity, the sheath was implanted and the dacryoendoscope removed. Then, a Nunchaku-style silicon tube (Lacrifast stents, Kaneka Co., Ltd., Tokyo, Japan) with an outer diameter of approximately 1.0 mm was implanted through the sheath into the nasal cavity, and the sheath was removed. A similar technique was performed from the other lacrimal punctum, and a second lacrimal tube was inserted.
Examination protocol and evaluation using AS-OCT After the BCI, antibiotic and low-concentration steroid eye drops were administered. Lacrimal irrigation was performed every two weeks to clean the inside of the artificial tear duct. In all patients, the silicon tube was removed about 2 months after surgery. After removal, an irrigation test was performed to evaluate the passage and to confirm lacrimal duct patency. Standard ophthalmic examinations such as visual acuity and slit lamp microscopy were performed at each visit. Corrected distance visual acuity (CDVA) was used to convert decimal visual acuity to logarithm of the minimum angle of resolution (logMAR) units for statistical analysis. The total corneal total HOAs and tear meniscus dimensions were evaluated using Fourier-domain swept-source AS-OCT (CASIA SS-2000; Tomey, Nagoya, Japan) with a wavelength of 1310 nm both before and after surgery. The acquisition speed of the instrument was 50,000 A-scans per second. The axial and transverse resolutions were 10 and 30 µm, respectively. Total corneal HOAs were measured at 4 mm in diameter by an automatic calculation with CASIA SS-2000 software. The measurement was taken using an eyelid opener; eyegenie™ (T.M.I Company, Saitama, Japan), such that pressure was not applied to the cornea or eyelid. The main reason for using an eyelid opener is to standardize the measurement technique, so that there are no differences across different measurers. The tear meniscus was evaluated by the cross-sectional OCT images of the lower tear meniscus height (TMH) and lower tear meniscus area (TMA) based on previous reports [16,18,21]. The measurements were taken about 1 s after a spontaneous opening blink of the eyelids. All OCT measurements were taken by trained orthoptists.

Statistical analysis
The patients' ages are expressed as means ± standard deviations. We used the paired t-test to compare the values of the parameters measured before and after surgery. The changes in TMH, TMA, and HOAs between preoperative and final postoperative final observation were calculated (Δ = preoperative value-postoperative value). Correlation between ΔHOAs and Δ tear meniscus (TM) values was evaluated by Pearson correlation analysis. All statistical analyses were performed with JMP® 14 (SAS Institute, Cary, NC, USA). P-values < 0.05 were considered significant.

Results
The clinical characteristics of the patients are summarized in Table 1. The mean age of the 49 patients (13 males and 36 females) was 68.1 ± 15.2 years (range 23-97 years). The affected eye was the right eye in 13 patients, left eye in 14 patients, and both eyes in 22. Baseline CDVA and intraocular pressure of the treated eye were logMAR 0.16 ± 0.48 and 14.4 ± 2.9 mmHg, respectively. Table 2 shows the classification of the occlusion site and the postoperative results.
Of the 71 eyes, 30 had common canalicular obstruction, 15 had canalicular obstruction, 7 had nasolacrimal duct obstruction, 14 had punctal obstruction, and 5 had common canalicular obstruction combined with nasolacrimal duct obstruction. Surgical success was defined as when the lacrimal tube could be correctly implanted during surgery, and surgical success was achieved on 69 eyes (97.1%) at the time of last observation. Surgical failure was observed in one case each of canalicular obstruction and punctal obstruction. The mean implantation period of the lacrimal tube was 62.8 ± 5.1 days, and the mean postoperative follow-up period was 130.2 ± 19.6 days. During the follow-up, a lacrimal irrigation test was performed, and patency was defined as when passage was confirmed. At the final observation, patency was obtained for 62 eyes (89.8%). The patency by site of obstruction was as follows: 29 (96.6%) of the common canalicular obstructions, 11 (78.6%) of the canalicular obstructions, 6 (85.7%) of the nasolacrimal duct obstructions, 11 (84.6%) of the punctal obstructions, and 5 (100%) of the common canalicular obstructions combined with nasolacrimal duct obstruction.
AS-OCT was used to evaluate the tear meniscus before and after surgery. Data on mean TMH are shown in Fig. 1. Mean TMH decreased significantly from baseline after surgery. Mean TMH was 1.55 ± 0.96 mm at baseline, 1.10 ± 0.70 mm at 1 month after surgery (p = 0.00088), 1.15 ± 0.86 mm at 2 months after surgery (p = 0.0065), and 0.97 ± 0.74 mm at the final observation (p < 0.0001). Data on mean TMA are shown in Fig. 2. Mean TMA decreased significantly from baseline after surgery. Mean TMA was 0.11 ± 0.14 mm 2 at baseline, 0.06 ± 0.08 mm 2 at 1 month after surgery (p = 0.02), 0.07 ± 0.09 mm 2 at 2 months after surgery (p = 0.02), and 0.06 ± 0.11 mm 2 at final observation (p = 0.02). AS-OCT was also used to evaluate the HOAs before and after surgery. Data on mean HOAs values are shown in Fig. 3. Mean HOAs were 0.37 ± 0.27 µm at baseline, 0.30 ± 0.11 µm at 1 month after surgery (p = 0.05), 0.30 ± 0.12 µm at 2 months after surgery (p = 0.02), and 0.29 ± 0.16 µm at final observation (p = 0.001). Significant decreases were at the final observation.

Discussion
Lacrimal passage obstruction is a common and important disease that causes visual dysfunction and decreased QOL. In this study, we performed SG-BCI for lacrimal passage obstruction and obtained good surgical success and postoperative patency. AS-OCT analysis quantitatively assessed the tear meniscus and showed significant postoperative decreases in height and area. Furthermore, there was a significant postoperative decrease in HOAs, indicating a correlation between the decrease in the tear meniscus dimensions and the decrease in HOAs. These results indicate that SG-BCI for lacrimal passage obstruction leads to improvement in HOAs with a decrease in the overall tear meniscus. Lacrimal tube intubation for lacrimal passage obstruction is a less invasive treatment than DCR as it does not require bone resection. However, because of individual variations in the morphology of the lacrimal passage [23], the surgical success rates of silicon tube intubation, which requires blind manipulation, had been reported at 50-80% [8,9,24]. Recently, however, silicon tube intubation using a dacryoendoscope has become widespread, especially in Japan, and the success rate has improved to about 89% because the obstructed area of the lacrimal duct can be directly observed, and the tube can be inserted more safely [10,12,13]. SG-BCI has also been developed. Because the sheath can push past the obstructed area and a lacrimal tube can be inserted into the sheath, the risk of lacrimal duct injury and false lacrimal passage is low, and it is considered a minimally invasive lacrimal surgery. It has been reported that lacrimal mucosal trauma associated with lacrimal tube insertion is a risk factor for surgical failure [12,25]. In this study, SG-BCI resulted in 97.1% surgical success and 89.8% postoperative patency, which was comparable to results from previous reports [14].
As shown in Table 2, we were able to obtain relatively high surgical success and patency regardless of the occlusion site. The postoperative patency of nasolacrimal duct obstruction cases was 85.7%, and that of common canalicular obstruction combined with nasolacrimal duct obstruction was 100%. In the past, nasolacrimal duct obstruction with dacryocystitis has been reported to have poor outcomes with lacrimal duct intubation, with approximately 50% of patients experiencing reobstruction at 12 months [12]. In our hospital, DCR is often chosen for cases with a large amount of pus drainage or after acute dacryocystitis; this may explain our relatively good results for nasolacrimal duct obstruction. In the future, it will be necessary to examine the results of treatment according to the presence or absence of dacryocystitis.
Recently, AS-OCT has been used for tear meniscus assessment [16-18, 21, 22]. Using AS-OCT, the height of the lower meniscus and the cross-sectional area of the lower meniscus can be measured objectively and noninvasively. Its efficacy in postoperative tear meniscus evaluation of DCR and lacrimal tube intubation has been reported [16,18]. In this study, we found a significant decrease in TMH and TMA after SG-BCI using AS-OCT, which may be a useful method for pre-and postoperative evaluation. Excessive tear fluid has been shown to affect various visual functions. Lacrimal passage obstruction is associated with decreased vision-related QOL, and lacrimal tube intubation has been reported to improve national eye institute visual function questionnaire (NEIVFQ-25) scores and Glasgow Benefit Inventory scores [6,10,14]. There are also reports of improved contrast sensitivity [22] and functional visual acuity [21] with lacrimal tube intubation. Associations between tear meniscus dimensions and HOAs have also been noted. HOA measurements are suitable to assess ocular surface conditions due to tear fluid, and it has been reported that epiphora is involved in the deterioration of HOAs [20,21]. In a study based on wavefront aberrometer, Koh et al. reported a significant decrease in ocular HOAs after lacrimal passage intubation, and our results on corneal tomography also showed a similar decrease in corneal HOAs [21]. Furthermore, we have shown for the first time that there is a positive correlation between tear meniscus reduction and HOA reduction. By contrast, excessive tear fluid, tear film, and delayed tear clearance due to lacrimal passage obstruction may worsen HOAs.
The limitations of this study are that it is a singlecenter retrospective study of a relatively small number of patients, all Japanese, with a short postoperative follow-up period. There was also a lack of evaluation of the ocular surfaces affecting the HOAs, such as conjunctival chalasis, tear break-up time, and the Schirmer test. It has also been reported that excessive retention of tear film may cause an infero-superior asymmetrical distribution in the precorneal tear-film thickness, possibly leading to increased coma-like aberrations [20]. Therefore, we need to consider not only total corneal HOAs, but also coma and spherical aberrations. In addition, when measuring OCT, it is necessary to consider the repeatability of the data and the difference in results when measurements are done with and without the eyelid opener. Further research is needed in the future.
In summary, SG-BCI for lacrimal passage obstruction showed good surgical success and lacrimal patency. Using AS-OCT we were able to noninvasively quantify postoperative tear meniscus reduction. Furthermore, we found a positive correlation between the decreases in tear meniscus dimensions and HOAs. Therefore, SG-BCI can result in improved HOAs, and the deterioration of HOAs in lacrimal passage obstruction could be a parameter indicating surgical intervention. Furthermore, the findings of the HOAs in this study may help to elucidate the pathogenesis of visual deterioration due to epiphora.