FormalPara Key Summary Points

Why carry out this study?

The primary purpose was to investigate the effects of pituitary adenoma surgery on the integrity of the visual pathway, focusing on the retinal structure, vascular density, and neural conduction functionality.

This research aimed to identify key factors that could predict and enhance recovery of visual function post surgery, a critical aspect given the frequent visual impairments associated with pituitary adenomas.

What was learned from the study?

The study uncovered significant changes in the visual pathway following surgery, including alterations in the retinal structure and neural conduction.

It was discovered that the thickness of the preoperative macular ganglion cell layer might serve as a predictive indicator for early postoperative visual function recovery, particularly regarding neural fiber conduction and visual field.

Introduction

Pituitary adenomas (PA), common benign tumors in the sellar region, often impair vision and visual field [1]. Transsphenoidal surgery, a prevalent and safe method, aims to decompress the optic chiasm and enhance vision, but predicting visual recovery post surgery is difficult [2]. Visual function recovery generally has an early phase post surgery and a later phase within 1–4 months [3]. PAs compress the optic chiasm, affecting the entire visual pathway [4]. Preoperative and various postoperative stages require comprehensive evaluation of these changes.

Optical coherence tomography (OCT) is commonly used for assessing optic nerve damage, providing quantitative, in vivo measurements, especially of the macular region and optic nerve head fibers. Key markers include the ganglion cell layer (GCL), ganglion cell complex (GCC), and the circumpapillary retinal nerve fiber layer (CP-RNFL). Studies have shown that patients with PA can have reduced CP-RNFL thickness without visual field anomalies [5, 9, 10]. Key DTI metrics include fractional anisotropy (FA) and apparent diffusion coefficient (ADC) or mean diffusivity (MD). FA measures the directionality of water diffusion, indicating white matter integrity, while ADC assesses the overall level of diffusion, which can increase in conditions like edema or axonal damage [10]. Changes in FA and ADC values can indicate nerve fiber recovery [11]. DTI has potential in predicting postsurgery vision recovery in patients with PA. Studies suggest that specific thresholds of FA and MD values can forecast surgical outcomes and visual function recovery [12, 13].

Our initial study combined OCT and DTI to evaluate preoperative visual impairment in patients with PA. In this research, we integrate DTI, OCT, and OCTA to assess early postoperative retinal structure, blood flow, and visual pathway function. We also explore factors predicting postoperative visual recovery. This study, first of its kind, aims to assess the effectiveness of using DTI, OCT, and OCTA together for early postoperative evaluation in patients with PA and to identify factors influencing visual function recovery. Our goal is to enhance clinical management and prognosis in patients undergoing transsphenoidal surgery for PA through a comprehensive assessment using these technologies.

Methods

This study is a retrospective clinical analysis involving 28 patients (56 eyes) who were initially diagnosed with PA at the Affiliated Hospital of Guangdong Medical University between June 2022 and August 2023. According to the medical records, all patients underwent comprehensive evaluations before and after surgery, including assessments of best-corrected visual acuity (BCVA), visual field testing, OCT of the optic disc, and OCT analysis of the macula. Furthermore, the records indicate that DTI was performed to examine the visual pathways. Among them, 15 patients (30 eyes) underwent additional preoperative and postoperative OCTA examinations. The OCTA examination was performed on only 15 patients because of limitations in resources and time. These patients were randomly selected from medical records to ensure the representativeness of the study. The OCTA test is very important for us to understand the changes in retinal and optic nerve blood flow density (BFD) after surgery. All participants provided informed consent.

In line with the standards of the Helsinki Declaration, this research strictly adhered to its guidelines and received approval from the Ethical Committee of the Affiliated Hospital of Guangdong Medical University (Approval number KT2022-038). All participating patients had provided their informed consent, as this was a retrospective review of clinical data.

Inclusion and Exclusion Criteria

1. A brain MRI scan with contrast indicates the presence of a PA, all cases were diagnosed with macroadenomas. The first postoperative MRI imaging is conducted within 4 weeks after surgery. This is aimed at effectively capturing the early changes post surgery, while also avoiding the potential impact of late physiological changes on the outcomes; 2. Endoscopic sinus surgery is used to remove the whole PA after histological confirmation; 3. Age between 18 and 60 years, clinically diagnosed with non-functional PA; 4. Intraocular pressure without contact is at or below 21 mmHg (Note: 1 mmHg is equivalent to 0.133 kPa); 5. Absence of prior conditions or events such as intracranial disorders, injuries, or surgeries; moreover, no history of eye injuries, glaucoma, retinal and optic nerve disorders, or intraocular procedures; 6. For spherical lenses, the refractive disparity is less than ± 6.00 D, and for cylindrical lenses, it is less than 3.00 D; 7. Crisp OCT and OCTA pictures with high-quality DTI images; 8. Exclusion of those whose chiasm becomes thin as a result of compression and cannot obtain the area of interest.

Visual Field Assessment

Patients had a visual field examination both prior to surgery and 1 month following correction of refractive defects, utilizing the Kowa AP7000 Precise Perimeter from Kowa, Japan. Two reliable visual field tests were conducted, assessing the central 30°. If fixation is lost, or if there are false positives or negatives exceeding 20%, the test is considered unreliable. The MD metric assesses the total visual field impairment.

For Tumor Analysis

Each patient was subjected to a presurgery MRI scan of the head with contrast to calculate the tumor’s size. The 3.0 T MRI examinations in this study were conducted using a Discovery MR750 scanner produced by General Electrics (Milwaukee, Wisconsin, USA). The specific measurement method for the diameter of PA is as follows: 1. Measure the tumor’s maximum vertical diameter from the sagittal view, perpendicular to the horizontal plane. 2. From the vertical line of the maximum vertical diameter, locate the tumor’s maximum anteroposterior diameter on the axial view. 3. On the determined axial view, measure the tumor’s maximum anteroposterior diameter and left–right diameter, which are perpendicular to each other. 4. Identify a horizontal line between the anterior and posterior nodes of the sellar diaphragm. Measure the height by which the tumor extends above this line, perpendicular to it, to determine the suprasellar height.

OCT Measurement of Retinal Nerve Fiber Layer (RNFL), GCC, Inner Plexus Layer (IPL), and GCL Thickness

The OCT device used in this study is the Heidelberg Engineering Spectralis OCT, a high-precision ophthalmic imaging equipment manufactured by Heidelberg Engineering in Germany. The Spectralis benchmarking software automatically determined and computed the mean thickness of CP-RNFL. Additionally, it evaluated the CP-RNFL’s nasal, superior, temporal, and inferior segments’ thickness. Moreover, it gauged the thickness of GCL, IPL, and RNFL within the central 1-mm zone of the macula. The nasal, superior, temporal, and inferior regions of GCL, IPL, and RNFL were measured for the thickness of the inner ring (within 1–3 mm from the central fovea) and the outer ring (3–6 mm from the central fovea). The GCC thickness is the combined total of RNFL, GCL, and IPL thicknesses as measured by the system (Fig. 1).

Fig. 1
figure 1

Optical coherence tomography Images of the optic disc and Macular Region. A retinal nerve fiber layer (RNFL) thickness in the macular region. B Optic disc circumpapillary RNFL thickness. C Macular region ganglion cell layer thickness. D Macular region inner plexus layer thickness. OD oculus dexter, OS oculus sinister, TMP temporal, SUP superior, NAS nasal, INF inferior, ETDRS Early Treatment of Diabetic Retinopathy Study

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BFD Measurement with OCTA in the Optic Disc and Macula

The Heidelberg Engineering Spectralis, a German-made device, was employed to scan both the optic disc and the macular area. The scanning resolution was set to High Res (5.7 μm/pixel). An OCTA image capturing various layers vessel density (VD) of the macular region was obtained with the central fovea as the center, covering an area of 3 mm × 3 mm (with 6-μm intervals, 512 A-scans). For the optic disc, an OCTA capturing various layers of VD image was centered on the optic disc, covering an area of 6 mm × 6 mm. The optic disc VD is composed of the following structures: the RPCP, the deep vascular complex (DVC), the deep capillary plexus (DCP), the superficial vascular plexus (SVP), the intermediate capillary plexus (ICP), and the superficial vascular complex (SVC). The VD of the macular area consists of DCP, SVP, ICP, DVC, and SVC. Raw images of the optic disc and macular area for SVC, DVC, SVP, ICP, and DCP VD were exported using the OCTA database. The Image J program (version 1.53) was then used to process and compute these pictures, setting the image threshold and an 8-bit grayscale format. After binarizing the images to make micro-vessels easy to detect, the VD of the various strata was computed. As seen in Fig. 2, VD represents the proportion of the picture area that is taken up by vessels [14].

Fig. 2
figure 2

Binarized blood flow density images of various layers of the optic disc and macular region for the case group (A–K). A Optic disc deep capillary plexus (DCP) layer. B Optic disc deep vascular complex (DVC) layer. C Optic disc intermediate capillary plexus (ICP) layer. D Optic disc superficial vascular complex (SVC) layer. E Optic disc superficial vascular plexus (SVP) layer. F Optic disc radial peripapillary capillaries plexus layer. G Macular DCP layer. H Macular DVC layer. I Macular ICP layer. J Macular SVC layer. K Macular SVP layer

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DTI Inspection and Image Post-processing

All individuals were scanned using a 16-channel phased-array head coil with a focus on T1WI and DTI imaging using the GE 3.0 T Optima MR360 system. Examination configuration for T1WI employed the Ax 3D BRAVO sequence with the subsequent parameters: 1 NEX, 0 mm interval, 240 × 240 mm field of view (FOV), 1.4 mm slice thickness, and 256 × 256 matrix. After adjustment of the values, the TR/TE was 12.3/5.1 ms. DTI used a one-time DW-SE-EPI protocol with 128 × 128 matrix, 240 mm by 240 mm FOV, and TR/TE at 9000/100.1 ms as example settings. It was set for a singular capture with 25 orientations for the diffusion gradient, a b-value set to 1000 s/mm2, and specified slice measurements at 2 mm thickness with 0 mm spacing in an axial orientation. Such parameters enable the gathering of color-marked tensor FA diagrams as well as ADC charts, to name a few.

DTI Data Pre-processing

Tensor FA and ADC maps were color coded according to a conventional scheme: left–right is red, anterior–posterior is green, and superior–inferior is blue. For each participant, measurements were taken of the optic nerve, optic tract, and front, center, and rear portions of the optic radiation. The left, center, and right parts of the optic chiasm were also evaluated. All of these assessments were conducted using the ADW 4.2 function tool that is included into the GE 3.0 T MRI scanner. We were able to determine the FA and ADC metrics by choosing three distinct regions of interest (ROIs) from the best images of the paired optic nerve, optic chiasm, both optic tracts, and optic radiation. The definition and measurement methods of the ROI were based on classic neuroanatomical descriptions and related literature [15]. The ROI size ranged from 8 to 12 mm2. When the optic chiasm was compressed, the shape of the ROI changed accordingly, but its size remained within the specified range. All the data, including the FA and ADC metrics of the optic nerve, optic chiasm, optic tract, and optic radiation in the three ROIs, were evaluated by the same physician (Fig. 3).

Fig. 3
figure 3

Diffusion tensor imaging seed point values of the visual pathway preoperatively for the case group. A, E Fractional anisotropy (FA)/apparent diffusion coefficient (ADC) values of the anterior, middle, and posterior segments of the optic nerve. B, F FA/ADC values of the left, middle, and right segments of the optic chiasm. C, G FA/ADC values of the anterior, middle, and posterior segments of the optic tract. D, H FA/ADC values of the anterior, middle, and posterior segments of the visual radiation

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Statistical Analysis

The statistical evaluations were carried out using IBM SPSS 24.0 tool. All data were subjected to the Shapiro–Wilk test and found to conform to a normal distribution. Data that displayed a normal distribution are shown as mean ± standard variation. In the patient cohort, a comparison was made between the OCT, OCTA, and DTI measurements before and after surgery using paired t tests. To evaluate the relationship between the parameters, we used Pearson’s correlation. P values were considered statistically significant if they were less than 0.05. All OCT and OCTA measurements were performed by the same specially trained technician to ensure consistency and accuracy. To further ensure objectivity, two independent experts conducted a blind analysis of the final data.

Results

The research encompassed 28 patients with PA, 16 male and 12 female. The average time for early postoperative radiological assessment was 13.821 ± 5.004 days post surgery. The pathological types consisted of 4 cases of corticotropin-secreting adenoma, 1 case of mixed growth hormone and prolactin-secreting adenoma, 2 cases of growth hormone-secreting adenoma, 1 case of prolactin-secreting adenoma, and 20 cases of non-functional PA. There were no statistically significant differences in pre- and postoperative BCVA, chiasm thickness, and visual field MD value. Although the visual field MD value did not statistically differ, there was a noticeable decrease post operation compared to pre operation (Table 1). All patients presented with large adenomas. The height above the sella ranged from 1.91 to 20.00 mm, with an average of 8.232 ± 4.448 mm. The tumor length varied from 13.60 to 28.96 mm, averaging 19.680 ± 3.642 mm. Tumor width was recorded between 10.25 and 20.76 mm, with an average of 15.853 ± 3.273 mm. The tumor height spanned from 9.77 to 23.63 mm, with a mean of 18.697 ± 5.201 mm.

Table 1 Comparison of visual acuity and visual field before and after surgery
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Changes in OCT and OCTA Parameters Before and After Operation

Postoperative mean CP-RNFL and nasal side CP-RNFL thicknesses decreased compared to pre operation, with P values of 0.040 and 0.023, respectively. There were no statistically significant differences in the thickness of the other quadrants of postoperative CP-RNFL compared to preoperative measurements (all P > 0.05) (Table 2).

Table 2 Early postoperative comparison of patient CP-RNFL thickness before and after surgery
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Early postoperative macular central 1 mm IPL and GCC thickness increased compared to pre operation, and the external nasal side of the macular RNFL thickened, with statistical significance; P = 0.012, 0.038, and 0.048, respectively. The internal quadrants and the external nasal and upper IPL decreased, with P = 0.016, 0.002, 0.000, 0.002, 0.013, and 0.002, respectively. Temporal internal GCL and temporal and lower GCC layers also decreased, with P = 0.005, 0.000, and 0.005, respectively (Table 3).

Table 3 Early postoperative comparison of patient GCC, IPL, and GCL thickness before and after surgery
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The early postoperative superficial RPCP density decreased compared to pre operation, with P = 0.045 (Table 4).

Table 4 Early postoperative comparison of optic disc and macular OCTA parameters before and after surgery
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Changes in Visual Pathway FA and ADC Values Pre and Post Operation

Early postoperative values for the left optic chiasm and posterior optic nerve FA increased, while the middle optic nerve FA decreased, with P values of 0.032, 0.040, and 0.043, respectively. The right optic chiasm, anterior optic nerve, middle optic nerve, and anterior visual tract ADC values increased postoperatively, with P values of 0.033, 0.014, 0.002, and 0.043, respectively. This suggests an early postoperative recovery of the conduction function of the left optic chiasm and the posterior optic nerve. In contrast, the functionality of the right optic chiasm, anterior and middle optic nerves, and anterior visual tract decreased postoperatively (Tables 5, 6).

Table 5 Early postoperative comparison of patient visual pathway FA parameters before and after surgery
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Table 6 Comparison of ADC parameters before and after surgery
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Correlation of Preoperative Macular Quadrant GCL Thickness with Postoperative Radiative FA, ADC, and Visual Field MD Values

1. Positive correlation was seen between the inner and outer macular quadrant GCL thicknesses and postoperative radiative FA values, whereas negative correlation was observed with postoperative radiative ADC values (all P < 0.05); 2. Inner quadrant GCL thicknesses correlated negatively with postoperative visual field MD values (all P < 0.05), with the strongest correlations observed for the temporal inner GCL and upper inner GCL with the postoperative visual field MD values, with r = − 0.473 and − 0.449, respectively, and P = 0.001 and 0.002, respectively.

Strongest Correlation Between Preoperative CP-RNFL, IPL, GCC, Optic Disk, and Macular OCTA Parameters with Postoperative Visual Pathway DTI Parameters

1. The strongest positive correlations were observed between preoperative upper external macular GCL thickness and postoperative optic nerve FA value (r = 0.384, P = 0.010); temporal inner RNFL thickness and postoperative chiasm FA value (r = 0.524, P = 0.000); nasal inner GCL thickness and postoperative visual tract FA value (r = 0.401, P = 0.007); and the lower inner GCL thickness and postoperative radiative ADC value showed the strongest negative correlation (r = − 0.588, P = 0.000); 2. The strongest negative correlations were observed between preoperative optic disk ICP density and postoperative optic nerve ADC value (r = − 0.422, P = 0.020); optic disk SVP and postoperative chiasm ADC value (r = − 0.429, P = 0.018); and optic disk DCP and postoperative visual tract ADC value (r = − 0.411, P = 0.024). No statistical correlations were found between preoperative CP-RNFL, optic disk, and macular area OCTA parameters with postoperative visual fields.

To provide a more comprehensive understanding of the changes observed in our study, we detail below the outcomes of two typical cases which illustrate the effects of PA surgery on the visual pathway. Case 1 involves a 33-year-old female patient diagnosed with a large pituitary macroadenoma. Before and after surgery, her visual acuity remained at 1.0, with a slight change in mean deviation values for both eyes. OCT and OCTA analysis showed a mix of thinning and thickening in various retinal layers and a decrease in peripapillary retinal BFD. DTI results indicated a recovery in neural conduction function, with most seed points of the ADC decreasing and FA values increasing postoperatively. Case 2 features a 53-year-old female patient with a sparsely granulated prolactin cell adenoma. Post surgery, her visual acuity improved, and MD values slightly changed. The patient experienced changes in the thickness of retinal layers similar to case 1. The peripapillary BFD showed mixed results, with an increase in the right eye and a decrease in the left eye. DTI findings suggested a partial recovery of neural conduction function, as indicated by changes in ADC and FA values. These case studies highlight the variable effects of PA surgery on the visual pathway, underscoring the importance of individualized patient analysis for optimal management.

Discussion

This retrospective study investigated the changes in the visual pathway following PA surgery, with a particular focus on alterations in retinal structure, vascular density, and neural conduction functions. Our principal findings include postoperative thinning of specific retinal layers, variability in neural conduction, and a reduction in the capillary density on the surface of the optic disc. Additionally, we observed that the thickness of the GCL in the macular region prior to surgery could potentially serve as a significant predictor for the restoration of visual functions postoperatively.

Changes in Retinal Structure and Visual Pathway Neural Conduction Before and After Surgery

There are multiple possible mechanisms for vision loss following compression of the optic chiasm in PA, including ischemic injury, demyelination, retrograde degeneration, and anterograde degeneration [4]. Soon after the optic chiasm is compressed, action potentials cannot propagate through the compressed point, leading to conduction blockage. Retrograde degeneration occurs when axonal damage leads to the death of the cell body, while anterograde degeneration is a result of damage to the cell body leading to axonal loss [16]. Compression of the optic chiasm causes retrograde degeneration of the axons leading to changes in the optic nerve, RNFL, and the GCC in the retina. Numerous studies, including our previous ones, have confirmed this [17]. Several studies [18] have also confirmed that anterograde degeneration leads to abnormal function of the visual tract and that transsynaptic anterograde degeneration can result in changes in the lateral geniculate nucleus, optic radiation, and visual cortex neurons.

Recovery of visual function happens in phases following the optic chiasm’s compression being released. Previous studies have suggested that the recovery of visual function following surgery involves at least two phases: an early phase occurring within a few days post surgery [3] and a later phase spanning 1–4 months postoperatively. According to earlier studies [19], the early rapid recovery phase is thought to happen in the initial hours and days following surgery and is mainly caused by the release of pressure on the visual pathway, which allows for the restoration of signal conduction. The second phase, which lasts for several years and is marked by a delayed recovery, is brought on by axonal transit, remyelination, and regeneration of the optic nerve’s vascular myelin sheath. There is a dearth of current studies on early-stage recovery of visual function. In order to mimic an expanding orbital tumor, Clifford-Jones et al. [20] conducted an early investigation in which they inflated a silicone rubber balloon in a cat’s orbit. The cat’s nerve fibers underwent significant demyelination during the first week; some fibers even underwent total degeneration, either partially or fully demyelinated. Five weeks later, however, numerous axons displayed myelin regeneration even though the orbital mass remained there. It can be inferred that even though the optic chiasm is compressed by the tumor, leading to axonal demyelination, the overall course is slow, with many axons regenerating their myelin. Factors related to the early stage of visual function recovery after optic chiasm decompression include 1. relief from compression on undamaged myelinated axons; 2. whether demyelinated axons showed signs of remyelination before decompression. The final outcome is reflected in the extent of recovery of neural fiber action potential conduction. In this retrospective analysis, we evaluated the neural conduction capacity of the visual pathway in the early postoperative period using DTI. We found that there was an improvement in neural conduction performance in certain areas of the posterior optic nerve and the optic chiasm, as shown by the FA values in those locations. This observation is at variance with the results reported by Mohamadzadeh and colleagues [13]. In DTI, two primary parameters are commonly utilized: FA and ADC, also known as MD. The FA value indicates the degree of directionality in water diffusion, ranging between 0 and 1. A value closer to 1 suggests better directional integrity and structural integrity of the white matter. The ADC value reflects the extent of water diffusion and may increase in certain pathological conditions, such as in vasogenic edema or the accumulation of cellular debris following axonal injury [9]. In injured neural fibers, an increase in FA value and/or a decrease in ADC value in subsequent DTI scans may indicate the recovery of neural fibers [11]. In their study involving 13 patients with PA, the researchers discerned no significant variation in the FA and MD metrics for the optic nerve, optic tract, and optic chiasm when comparing preoperative and 3-month postoperative data. This discrepancy may be related to different follow-up time points.

In our study, we observed that early postoperative mean and nasal CP-RNFL thickness were thinner than pre operation, the macular inner ring quadrants and the outer nasal and upper IPL were thinner; the inner temporal and lower GCL and GCC layers were also thinner. This is consistent with Lee et al. [21], who found that the macular area RNFL, RGC layer, and IPL layer gradually thinned over a period of up to 1 year. At the same time, this study also found that the neural conduction function of some optic chiasm, anterior, and middle optic nerve and optic tracts deteriorated in the early postoperative period. A possible explanation is that before decompression, some ganglion cells function normally, some are atrophied, and some are in a dysfunctional state. After decompression, the first two are unaffected, while the dysfunctional ones may have partially recovered, with others continuing retrograde and anterograde degeneration. The end result is manifested as quadrant CP-RNFL, GCL, IPL, and GCC layers thickening or thinning, with some visual pathway neural functions recovering, while others deteriorate. The study also observed that the early postoperative central 1 mm IPL and GCC layer of the macula were thicker than before surgery, and the outer nasal RNFL was thicker, which also explained the improvement of postoperative visual field MD value, although not statistically significant.

Regarding the changes in OCTA parameters, our study found that postoperative optic disc RPCP density was lower than before surgery. This is similar to the findings of Ben Ghezala et al. [8], who found that 6 months after decompression surgery, RPCP density was still lower than before surgery. The current explanation for the decrease in preoperative optic disc RPCP density is that after the optic chiasm is compressed, damage to the ganglion cells and axons will reduce the metabolic activity of the inner layer of the retina, leading to decreased demand for oxygen and blood. This decrease may result in the degeneration of the superficial capillary network. Wang et al. [22] also confirmed that retinal BFD is significantly related to CP-RNFL and GCC layer. We speculate that the decrease in postoperative optic disc RPCP is also due to the postoperative nasal and average CP-RNFL being thinner than before surgery, further reducing the demand for oxygen and blood, leading to further atrophy of the superficial vessels.

Factors Predicting Postoperative Visual Function Recovery

The recovery of visual function after surgery has always been a research hotspot. The GCC plays a diagnostic and prognostic function, as evidenced by recent studies [23]. According to research by Santorini et al. [24], the inner inferior ring ganglion cell thickness appears to be the strongest predictor of visual field loss within the limits of macular thickness. It is speculated that this area is first compressed below the optic chiasm. Our study found that the preoperative thickness of the GCL in the macular inner inferior ring has the closest relationship with the early postoperative visual radiative ADC value, with a correlation coefficient of r = − 0.588. In other words, the preoperative GCL thickness at this site has predictive value for early postoperative visual radiation recovery.

Santorini et al.’s research also found the highest correlation between the thickness of the GCL in the upper central macula and the lower central visual field. In a 2-year study, Meyer et al. [25] directly compared preoperative mGCL and pRNFL OCT parameters for the prognostic utility of chiasmal compression and long-term follow-up. The results indicated that mGCL parameters are more accurate than pRNFL, and the best predictor of the degree of long-term visual field recovery is the thickness of the GCL in the upper macular inner ring. In particular, the preoperative GCL thickness in the temporal inner ring and the upper inner ring of the macula have the strongest correlation with the postoperative visual field MD value, indicating that the GCL thickness at these two sites preoperatively may have predictive value for the recovery of early postoperative visual field damage. Our research revealed that the thickness of the GCL in all quadrants of the macular inner ring is negatively correlated with the MD value of the visual field. Previous research [4] suggested that retrograde degeneration, or the spread of injury from the optic chiasm to the retina’s cell bodies, was the cause of axonal injury to retinal ganglion cells. As a result, the thickness of the GCL is a good indicator of the degree of retinal layer atrophy and can be used to predict visual outcomes following surgery. Our research also confirmed this.

Some studies [26] believe that the BFD near the preoperative optic disc is related to the postoperative visual field and may be a prognostic factor. The results of our study, however, contradict this; they are similar to those of Ben Ghezala et al. [8], who found no correlation between the postoperative visual field’s MD value and the BFD around the preoperative optic disc. With a correlation coefficient of r = − 0.422, our data showed a clear negative relationship between the preoperative optic disc ICP density and the postoperative optic nerve ADC value. Likewise, there is a noteworthy inverse association (r = − 0.429) between the preoperative optic disc SVP and the postoperative optic chiasm ADC value; and the preoperative optic disc DCP has the strongest negative correlation with the postoperative optic tract ADC value, r = − 0.411. This suggests that the BFD near the optic disc may also have a role in predicting postoperative visual pathway nerve conduction function.

The constraints of this research encompass the following: primarily, it is conducted at a single institution and involves a comparatively limited participant pool, and subgroup analyses, such as research on tumors compressing the optic chiasm to different extents, were not conducted. Second, because the follow-up time was so brief, longer-term research is still required to identify the variables influencing the recovery of visual function. Besides, despite non-random patient selection, bias was reduced through strict criteria and comprehensive case evaluations. Statistical analyses like the paired t test and Pearson correlation were applied for accurate assessment of surgical outcomes. Recognizing this limitation, results were interpreted with care, and future studies will use randomized methods to improve representativeness and reliability. Lastly, this study utilized external software in the application of OCTA and employed unconventional segmentation of the optic nerve head (ONH) area. We recognize that this approach may differ from the standard or traditional methods used in other studies, which could affect the generalizability of our results. Moreover, the use of external software and unconventional segmentation methods may introduce additional biases that were not fully explored in our study. Therefore, future research will consider adopting more standardized OCTA analysis techniques to enhance the comparability and universality of the findings.

Conclusions

This retrospective study on postsurgical changes in patients with PA highlights key findings: thinning of certain retinal layers, variability in neural conduction, and decreased capillary density post operation. Significantly, preoperative macular GCL thickness may predict visual recovery. These insights, despite the study’s limited sample size and duration, emphasize the importance of comprehensive pre and postoperative evaluations for understanding and predicting visual pathway recovery.