Changes in Corneal Higher-Order Aberrations and Ocular Biometric Measurements after Phacoemulsification Combined with Goniosynechialysis in Primary Angle Closure/Glaucoma Patients

Purpose To compare corneal higher-order aberrations (HOAs), refractive error, and ocular biological parameters before and after phacoemulsification combined with goniosynechialysis (Phaco-GSL) in primary angle closure/glaucoma (PAC/PACG) patients with different axial lengths (ALs). Methods In this prospective study, cataract patients diagnosed with PAC/PACG were categorized into two groups based on their ALs: the short AL group (AL ≤ 22.5 mm) and the normal AL group (22.5 < AL ≤ 24.5 mm). The pre- and postsurgery measurements of intraocular pressure (IOP) and best-corrected visual acuity (BCVA) were conducted at 1 day, 1 week, 1 month, 3 months, 6 months, and 12 months. Additionally, the assessments included corneal HOAs, the number of antiglaucoma medications, visual field parameters, manifest refraction, and other ocular biological parameters before surgery and at the final follow-up. Results Prior to surgery, the two groups exhibited no significant differences, except for AL, curvature value, and Z (4, 0) of the posterior corneal surface (all P < 0.01). Following surgery, BCVA improved, and IOP decreased significantly in both groups (P < 0.01). Both anterior and total corneal HOAs, along with Z (3, −3), increased in the two groups (all P < 0.05), with the normal AL group exhibiting a significantly greater increase in total cornea Z (3, −3) than the short AL group (P=0.047). The normal AL group also exhibited a slight tendency towards hyperopia (P < 0.01). Significant changes were observed in the visual field index and mean deviation in both groups (P < 0.05). Conclusions Phaco-GSL resulted in an increased corneal HOAs, particularly trefoil, with variations based on the patient's AL. Patients with normal ALs tended to shift towards hyperopia after surgery.


Introduction
Cataracts and glaucoma are the leading global causes of blindness, with Asians experiencing a higher incidence of primary angle closure (PAC) and PAC glaucoma (PACG) than Europeans and Africans [1].As the global population ages, there has been an increase in cases of concomitant PAC/PACG and cataract [2].In recent years, ophthalmologists have shown interest in a surgical technique called phacoemulsifcation combined with goniosynechialysis (Phaco-GSL), which involves stripping the peripheral anterior synechia (PAS) from the angle wall and restoring trabecular fltering function and has proven efective in lowering intraocular pressure (IOP) and preventing scarring of the fltering bleb after glaucoma fltration surgery [2][3][4].
Mounting evidence indicates that cataract surgery can induce corneal aberrations due to surgical incisions and alterations in ocular biological parameters, leading to refractive errors and abnormal visual quality [5,6].Tese higher-order aberrations (HOAs), such as trefoil, coma, and spherical aberrations, are signifcant distortions that cause visual disturbances such as dazzles and starbursts and have been associated with surgical procedures [5][6][7][8].HOAs are optical imperfections of the eye that can afect the retinal image quality and result in visual symptoms.Factors such as age, refractive error, near work, and accommodation can have varying efects on the type and magnitude of HOAs [9].Furthermore, during cataract development, the number of internal ocular HOAs tends to increase, with notable positive shifts in coma RMS and primary spherical aberrations (Z0,4) in cortical and nuclear cataracts, respectively [10,11].Te impact of HOAs on visual quality may vary among individuals, depending on factors such as pupil size, amount of aberration, individual visual system, and adaptability.Strategies such as refractive operations or the implementation of appropriate lenses may be considered to mitigate the efects of these aberrations on the visual quality.To the best of our knowledge, only a few studies have investigated corneal HOAs in patients with PAC/PACG and cataracts.Furthermore, PAC/PACG eyes exhibit distinct characteristics, including shallower anterior chambers, shorter axial lengths (ALs), zonular weakness, and larger lens capsule sizes [12], which complicate the prediction of intraocular lens (IOL) positioning after surgery.Determining IOL power in PAC/PACG eyes remains challenging, necessitating surgeons to warn patients about the higher risk of postoperative refractive error.Some studies have found a correlation between AL and unpredictable refractive outcomes after cataract surgery, with a longer AL being associated with greater refractive error [13,14].Additionally, the glaucoma fltration surgery typically results in a decreased AL [15].Terefore, the selection of IOLs for PAC/PACG patients should difer from that for patients with age-related cataracts only.
Given the limited available literature on this subject, our study aimed to compare corneal HOAs, ocular biological parameters, and refractive errors before and after phaco-GSL in patients with diferent ALs.We sought to identify factors associated with refractive outcomes and compare the success rate of IOP reduction after surgery.

Patient Selection.
Consecutive patients scheduled for phaco-GSL at the Daping Hospital of Chongqing, China, between January 2020 and July 2021 were enrolled in this prospective group study.Te study and all examinations adhered to the Declaration of Helsinki on Ethical Principles for Medical Research Involving Human Subjects and received approval from the hospital's Ethics Committee (TDLL 2020-90).All participants provided informed consent prior to inclusion in the study.

Inclusion and Exclusion
Criteria.Tis study included patients aged ≥50 years with a diagnosis of PAC/PACG and concomitant cataracts.Te diagnosis of PAC or PACG adhered to the criteria outlined by the International Society of Geographic and Epidemiologic Ophthalmology [16].For PAC patients, the diagnosis necessitated at least 180 °of iris trabecular contact during a gonioscopic examination, accompanied by increased IOP or PAS, without a diagnosis of glaucomatous optic neuropathy.In the case of PACG patients, the diagnosis required evidence of glaucomatous optic nerve damage in addition to the aforementioned criteria.Te exclusion criteria were fxed dilated pupils, secondary angle closure due to uveitis or ocular trauma, lens subluxation, ocular AL ≤20 mm, and a history of ocular surgery or other ocular diseases.Upon recruitment, patients were categorized into two groups based on their ALs: the short AL group (AL ≤ 22.5 mm) and the normal AL group (22.5 mm < AL ≤ 24.5 mm) [17,18].

Clinical Data Measurement.
Before surgery, a comprehensive ophthalmic examination was performed on all patients.Te collected data included patient demographics (age, sex, and number of antiglaucoma medications), IOP, manifest refraction, astigmatism, best-corrected visual acuity (BCVA), AL, keratometry (K) values, anterior chamber depth (ACD), corneal HOAs, and visual feld parameters.Te IOL-Master700 (Carl Zeiss Meditec, Jena, Germany) was used to measure the AL and K values, and the online Barrett Universal II formula was used for the IOL calculations.Te ACD was measured using ultrasound biomicroscopy (Tianjin Suowei Electronic Technology Co., Ltd.).Visual feld parameters were obtained using the Humphrey Field Analyzer 750II (Carl Zeiss Meditec, Dublin, CA).Te IOP and BCVA were reassessed on the frst postoperative day and during subsequent follow-up visits (1 week, 1 month, 3 months, 6 months, and 12 months).Manifest refraction, ACD, visual feld parameters, AL and K values, and the number of antiglaucoma medications were recorded again during the fnal follow-up visit.Combined drops were counted as two medications.Corneal HOAs were measured using a rotating Scheimpfug camera (Pentacam HR, Oculus, Wetzler, Germany) in a dark room, maintaining a 6.0-mm pupillary diameter.Te image was selected when the instrument displayed "OK."Te Zernike coefcients of individual patients were analyzed, including the root-mean-square (RMS) of HOAs, primary spherical aberration Z (4, 0), horizontal coma Z (3, 1), vertical coma Z (3, −1), oblique trefoil Z (3, 3), and vertical trefoil Z (3, −3) of the total cornea, anterior cornea surface, and posterior cornea surface.Multiple measurements were averaged for each parameter.
Te success rate of the procedure was determined using the following criteria: complete success, defned as achieving an IOP of 5 mmHg ≤ IOP ≤ 21 mmHg and at least ≥20% reduction in IOP without any glaucoma medications; qualifed success, defned as achieving an IOP of 5 mmHg ≤ IOP ≤ 21 mmHg and at least ≥20% reduction in IOP with glaucoma medications; and failure, defned as achieving an IOP >21 mmHg on maximally tolerated medications [19].

Surgical Technique.
A single experienced surgeon (LY) performed all Phaco-GSL surgeries.Te procedure commenced with topical anesthesia, followed by standard phacoemulsifcation using a 2.8-mm clear corneal incision at the 10 o'clock position and a 1-mm lateral incision.Subsequently, a hydrophilic acrylic intraocular lens (IOL) Journal of Ophthalmology (Akreos AO, Bausch & Lomb Inc., Rochester, NY, USA) was implanted into the capsule.Te operating microscope was angled at approximately 45 °, and the Swan Jacobs direct gonio lens (Ocular Instruments, Bellvue, WA, USA) was placed on the cornea for angle visualization.Viscoelasticity was measured along the peripheral anterior chamber to facilitate the opening of the PAS.A modifed iris repository was used to separate the residual PAS and expose the trabecular meshwork.Te viscoelastic material was thoroughly removed, and the incision was sealed by corneal stromal hydration.After surgery, all patients received prescriptions for pranoprofen medications (Pranopulin) and tobramycin dexamethasone eye drops (TobraDex) to be applied four times daily, with gradual dose tapering over 4-6 weeks.

Results
Initially  1. Notably, except for the AL, K values, and Z (4, 0) of the posterior corneal surface (all P < 0.01), no signifcant diferences were noted between the groups, with both groups comprising a higher proportion of female patients.
Figure 1 shows the time-dependent changes in BCVA (LogMAR chart records) and IOP.Preoperatively, the mean IOP with drug treatment was 23.42 ± 9.39 mmHg in the short AL group and 22.06 ± 7.89 mmHg in the normal AL group.Generalized estimation equation analysis demonstrated a signifcant decrease in IOP at each follow-up compared with that at baseline in both groups (P < 0.05).Te IOP had stabilized at the 1-month follow-up.Similarly, the mean preoperative BCVA was 0.41 ± 0.48 in the short AL group and 0.40 ± 0.34 in the normal AL group.Generalized estimation equation analysis demonstrated a signifcant improvement in BCVA at each postoperative follow-up compared with that at baseline in both groups (P < 0.05).At the fnal follow-up, BCVA improved to 0.13 ± 0.16 in the short AL group and 0.14 ± 0.16 in the normal AL group.In addition, the number of antiglaucoma drugs decreased from 2.60 ± 1.01 to 0.90 ± 0.88 in the short AL group and from 2.85 ± 0.80 to 0.69 ± 0.85 in the normal AL group, with no signifcant diference between the groups (P > 0.052).Te success rate at the fnal follow-up was 91.67% in the short AL group, comprising complete and qualifed success rates of 47.92% and 43.75%, respectively, and a failure rate of 8.33%.Te success rate was 95.83% in the normal AL group, with complete and qualifed success rates of 52.08% and 43.75%, respectively, and a failure rate of 4.17%.
Table 2 presents changes in corneal HOAs.Before surgery, the short AL group demonstrated signifcantly higher HOAs and posterior corneal Z (4, 0) than the normal AL group (P � 0.036, P < 0.01, respectively).After surgery, the normal AL group showed a signifcantly greater increase in total cornea Z (3, −3) than the short AL group (P � 0.047).When comparing changes in HOAs pre-and postsurgery within each group, both groups demonstrated an increase in postoperative HOAs and Z (3, −3) of the anterior surface and total cornea at the fnal follow-up (all P < 0.05).Moreover, the short AL group demonstrated an increase in anterior surface Z (3, 3) and posterior corneal Z (4, 0) (P � 0.009, P � 0.005).On the other hand, the normal AL group demonstrated an increase in posterior corneal HOAs (P � 0.021).
Refractive status is categorized as myopia (≤−0.50D), emmetropia (−0.50 to +0.50 D), and hyperopia (≥0.50 D).Almost half of the patients in each group demonstrated hyperopia, with the short AL group exhibiting a slightly higher proportion (n � 23, 47.9% versus n � 23, 43.8% in the normal AL group).Emmetropia was present in approximately one-third of the patients in both groups (short AL group: n � 18, 37.5% vs. normal AL group: n � 14, 29%).Only a small percentage of patients were myopic in the short AL group (14.6%, n � 7), whereas the normal AL group had a higher myopic representation (27.1%, n � 13).Table 1 shows the refractive error results, defned as the diference between the predicted and actual postoperative SE.No signifcant diferences were observed in the preoperative and predicted SE between the groups (P � 0.201 and P � 0.600, respectively); however, a signifcant diference was found in the postoperative refractive error between the groups (P � 0.046).Te normal AL group displayed a slight shift towards hyperopia (P < 0.01), whereas the short AL group did not exhibit a signifcant diference (P � 0.756).Table 3 shows an increased ACD postoperatively in both groups (P < 0.01), with no signifcant diference between the groups (P � 0.396, P � 0.233).Compared with the preoperative baseline, there were no signifcant diferences in the K values and AL changes between the groups (P > 0.05).
Visual feld assessment using the 24-2 SITA standard test indicated no signifcant diferences in the mean deviation Journal of Ophthalmology (MD), visual feld index (VFI), or pattern standard deviation (PSD) between the short and normal AL groups (P > 0.05; Table 1).Further examination, as shown in Table 4, revealed a reduction in MD (both P < 0.01) and an improvement in VFI (both P < 0.01) in both groups after surgery.However, there were no signifcant changes in the PSD in the either group (P � 0.05, short AL group; P � 0.052, normal AL group).

Discussion
Currently, Currently, Pd data and the Mann-d the study, performed the visualization, wrote the original draft, and wrote, reviewed, and edihaco-GSL is the primary treatment for PACG/PAC with cataracts.However, a discrepancy often exists between the expected and postoperative visual image quality, leading to suboptimal efcacy [20].A case-control study highlighted that PACG patients may experience a higher incidence of refractive errors after phacoemulsifcation than those with a single cataract or primary openangle glaucoma [21].Te presence of a shallow ACD and short AL in PACG patients contributes to poor refractive accuracy [21].HOAs also afect postoperative visual quality [7,8].However, limited research has been conducted on changes in HOAs and ocular biological characteristics in PACG/PAC patients with concomitant cataracts and different ALs.Terefore, in this study, we investigated these changes to identify the infuential factors.
We observed an increase in HOAs, particularly Z (3, −3) of the anterior surface and total cornea, in both groups at the fnal follow-up, consistent with the fndings of a previous randomized controlled trial conducted by Marcos et al. [22], which demonstrated a signifcant increase in corneal trefoil and tetrafoil after cataract surgery without any signifcant  changes in spherical aberration or coma.Te increase in HOAs could potentially be attributed to corneal infammation, edema, or remodeling of endothelial cells during the early stages of surgery, which gradually resolves over time [23,24].Although further research is needed to fully understand the role of HOAs in visual function, our study revealed, at the same cataract incision size, diferent increments in the anterior surface and total cornea Z (3, −3) in each group, indicating potential diferences in visual quality.
Trefoil, classifed as an HOA, can result in misfocusing of light on the retina, leading to blurred or distorted vision, reduced contrast sensitivity, compromised depth perception, halos, and starbursts, particularly in environments with low lighting conditions.Previous studies have established a correlation between trefoil and AL, highlighting its strengthening after surgery without compensatory adjustments from the internal optics of the eye [25,26].Moreover, a deeper anterior chamber can alter the trajectory of light upon entering the eye, potentially triggering an increase in HOAs.Te variation in AL   between the groups and alterations in ACD after surgery, as observed in this study, may explain the increase in Z (3, −3) after Phaco-GSL.Among the patients included in this study, no signifcant diference was noted in predicted SE between the two groups.However, the most recent postoperative manifest refraction revealed a tendency for the normal AL group to incline toward hyperopia after surgery.
Our observations also revealed that the ACD deepened in both groups after Phaco-GSL.Cataract removal can induce ACD deepening and subsequently trigger a hyperopic shift in PACG cases where the IOL is implanted in a more posterior position than initially planned [21].However, the precise mechanism underlying these refractive changes remains unclear.Factors such as large lens capsule size, IOL tilt, or eccentricity can contribute to inefective lens positioning [27].Although numerous studies have reported the occurrence of refractive shifts after cataract surgery, the underlying mechanisms remain elusive.Phaco-GSL involves the removal of the lens and deepening of the anterior chamber.According to Ning et al. [27], patients with a shorter preoperative ACD and AL tend to experience greater changes in ACD, leading to a drift towards myopia after cataract surgery.In contrast, patients with a deep preoperative ACD and long AL are more prone to drift towards hyperopia.Tese fndings underscore the predictive value of the ACD in determining refractive outcomes after age-related cataract surgery.Moreover, several studies have highlighted ACD as an indicator of the postoperative position of the IOL, with each 1-mm change in ACD potentially resulting in a refractive shift of at least 0.32D [27,28].
Visual feld examination revealed improvements in MD and VFI after surgery in both groups, with no signifcant changes in PSD.Tis suggests that PSD, which represents pathological visual feld loss due to lesions, remained unchanged after cataract extraction.Tese fndings were consistent with those of a previous study [29].Moreover, a reduction in the postoperative use of antiglaucoma medications and high success rates were observed, which are consistent with previous fndings [30].
However, it is important to acknowledge the limitations of this study.No PAC/PACG patients with AL >24.5 mm were included during the study period, which is consistent with other studies focusing on the AL of the PAC in Asian populations [31,32].Additionally, the absence of a control group undergoing cataract surgery alone among PACG/PAC patients makes it challenging to ascertain whether the observed changes in refractive and corneal HOAs are exclusively associated with GSL separation.Furthermore, although we explored the changes in corneal HOAs among patients, whether these aberrations were associated with vision quality has not yet been elucidated.Further research with larger sample sizes is imperative to investigate the mechanisms underlying changes in corneal HOAs and refractive errors after surgery in PACG/ PAC patients with cataracts and diferent ALs.

Conclusion
In conclusion, our study fndings indicated that phaco-GSL led to increased corneal HOAs, particularly trefoil, at the 1year follow-up.Tese changes varied depending on the ALs of the patients.Notably, the change in ACD was found to be the primary infuencer of the refractive error.Patients with normal ALs experienced a tendency towards a shift to hyperopia after surgery.Further prospective studies with larger sample sizes are warranted to elucidate the roles of diferent ALs in ocular changes after phaco-GSL.

Figure 1 :
Figure 1: Time-dependent changes in BCVA (LogMAR chart records) and IOP in the two groups.(a) Time-dependent changes in BCVA: the postoperative BCVA was lower than at baseline in both groups at each time point.Error bars represent standard error values.(b) Timedependent changes in IOP: the postoperative IOP was signifcantly lower than at baseline in both groups at each time point.

Table 3 :
Comparison of ocular biological parameters between the two groups.: P < 0.05, signifcant diferences between the two groups before surgery.† : P < 0.05, compared with the preoperative baseline in each group.ACD: anterior chamber depth; AL: axial length; D: diopter. *

Table 4 :
Comparison of visual feld parameters between the two groups.