Fundus Evaluation in Myopia: Essential for Pre- and Post-refractive Surgery

doi:10.21203/rs.3.rs-4941967/v1

Objective

To evaluate fundus conditions and analyze ocular examination parameters among myopic patients before and after refractive surgery.

Methods

This retrospective study enrolled 116 patients (144 eyes) divided into three groups: normal retina (normal group), retinal lesion not requiring treatment (untreated group) and retinal lesion requiring treatment (treated group). The treated group received preventive treatment for retinal diseases before refractive surgery. Demographic information, visual acuity, refraction, intraocular pressure (IOP), axis length (Axl), pupil diameter (PD), corneal tomography, and fundus images were collected and compared pre-operatively and post-operatively at 1 day, 6 months and 12 months.

Results

The treated group exhibited significantly higher pre-operative Axl and SE value compared to the other groups (P < 0.05). This group also displayed the most severe retinal diseases, with 52.5% presenting retinal holes or tears and 47.5% exhibiting lattice degeneration. SMILE surgery was performed in 78% of the normal group, 50% of the untreated group and 32.5% of the treated group. Postoperatively, all three groups demonstrated positive surgical outcomes with stable retinal conditions, and no new retinal holes or detachments during follow-ups.

Conclusions

Higher myopia and longer axial lengths increased retinopathy risk. Detailed preoperative fundus exams, long-term follow-ups and prophylactic treatment before surgery are essential.

myopia

refractive surgery

fundus examination

retinal lesion

Myopia, commonly known as nearsightedness, is a vision disorder where light focuses in front of the retina instead of directly on it, leading to blurry distant objects^1–3. Myopia can significantly affect daily activities like watching and driving⁴. Severe myopia increases the risk of serious ocular issues such as retinal detachment, glaucoma, and cataracts, which can lead to irreversible vision loss if not treated adequately^5–8.

Refractive surgery offers several advantages in myopia treatment, featuring a quick recovery period, with many individuals reporting enhanced vision within just 24 hours post-operatively^{9, 10}. However, surgical procedures may impact retinal structures¹¹. For example, laser-assisted surgical techniques can create a substantial rise in intraocular pressure (IOP) due to the application of a suction ring or an acoustic shock wave generated during laser ablation, potentially damaging the retina^{12, 13}. Arevalo and colleagues found that 20 eyes developed rhegmatogenous retinal detachment (RRD) after laser in situ keratomileusis (LASIK) in a review of 31,739 myopic eyes¹⁴. Additionally, Yang et al. reported that 19.94% of myopic eyes from refractive surgery candidates had peripheral retinal lesions, with 4.35% having holes or tears¹⁵.

Furthermore, it’s commonly believed that patients with high myopia are prone to retinal disorders, leading to a neglect of fundus evaluation among patients with low myopia^{16, 17}. However, clinical practice has revealed that low myopia patients can also exhibit retinal lesions, some as severe as those in high myopia. Since most preoperative examinations focus on the anterior segment of the eye and overlook the posterior segment, potentially leaving pre-existing retinal lesions undetected.

Given the limited research on these issues and their confinement to case reports, our study addressed a crucial gap by conducting pre- and post-operative fundus evaluations in myopic patients. By analyzing various ocular parameters, we aimed to provide valuable insights to enhance clinical practice and ensure better patient outcomes.

Ethical approval

This retrospective study evaluated the database in Zibo Central Hospital from August 2019 to December 2022 and was conducted in accordance with the tenets of the Declaration of Helsinki. Ethical approval was achieved from the Institutional Review Board of Zibo Central Hospital. All participants provided written informed consent to use their data for analysis and publication.

Study population

A total of 144 myopic eyes from 116 patients undergoing refractive surgery were enrolled in this study. The 144 myopic eyes were divided into three groups based on pre-surgical retinal conditions: normal retina (normal group, n=50), retinal lesion not requiring treatment (untreated group, n=54) and retinal lesion requiring treatment (treated group, n=40). In the treated group, retinal diseases were preventively treated with laser photocoagulation before refractive surgery. And refractive surgery was recommended to perform after at least a 14-day interval following laser photocoagulation. The treatment criteria were as follows, according to the guidelines of Tongren fundus laser treatment manual¹⁸.

Treatment recommendations for retinal degenerations

Treat promptly: Horseshoe tears, operculated holes, lattice degeneration with retinal holes, symptomatic lattice degenerations without retinal holes and atrophic holes.
Observe: Asymptomatic lattice degeneration without retinal holes, pigmented lattice.
Consider treatment: Atrophic holes or lattice degeneration if the fellow eye has developed retinal detachment.

Preoperative and postoperative examination

Demographic information and various ocular parameters were collected before surgery, including uncorrected distance visual acuity (UDVA), IOP (Topcon, CT-800, Japan), and spherical equivalent (SE) (Topcon, KR-800, Japan). Scheimpflug tomography (OCULUS, Pentacam AXL, Germany) was used to measure anterior and posterior surface curvatures, anterior and posterior surface heights, central corneal thickness (CCT), Axl, PD. Fundus evaluation was performed via two methods: a standard dilated fundus examination conducted by a retinal specialist with a Goldmann three-mirror lens (Ocular, Bellevue, Washington) after full pupil dilation, and fundus images captured via ultrawide-field fundus photography (Daytona, Optos, UK). UDVA, IOP, SE and fundus manifestations were also collected at 1 day, 6 months and 12 months postoperatively. Data analysis between various ocular parameters were conducted.

Prophylatic treatment

Argon laser photocoagulation (Guantel Medical, SUPRA SCAN 577, France) was performed in treated group before refractory surgery. Laser parameters were set as follows: the diameter of the peripheral photocoagulation spot ranged from 200 to 300 µm, with an exposure time of 0.2 to 0.3 seconds and a class 3 spot reaction. The photocoagulation spots enclosed the retinal lattice degeneration area in 1 to 2 rows and the retinal hole in 2 to 3 rows. For horseshoe holes and holes with vitreoretinal traction, the spots surrounded 3 to 4 rows. Each spot was connected but not fused with the adjacent one. Additional laser photocoagulation was performed as necessary during follow-up. If the fundus condition recovered well and no complications occured within 14 days post-treatment, the patient can be prepared for refractive surgery.

Refractory surgery

Standard surgical procedures were performed for all subjects by experienced surgeons. In small incision lenticule extraction (SMILE) surgery, the procedure was performed using a VisuMax femtosecond laser (Carl Zeiss Meditec, Jena, Germany): a stromal lenticule was removed, leaving a cap ranging in thickness from 110 to 135 µm, and a 2 mm incision was made at the 120° position for subsequent lenticule dissection and extraction. In femtosecond laser assisted-laser in-situ keratomileusis (FS-LASIK) surgery lamellar flaps with a superior hinge, thickness of 100 to 110 µm, and diameter of 8.5 to 9 mm were created with a VisuMax femtosecond laser. FS-LASIK ablation was then performed using a 1050 Hz excimer laser (Carl Zeiss Meditec, Mel 90, Germany). In laser-assisted subepithelial keratomileusis surgery, a corneal epithelial flap was created with 20% alcohol solution instilled inside the trephine centered on the pupil, leaving a superior hinge. The ablation was performed with a Mel 90 1050Hz excimer laser over an optical diameter ranging from 6.2 to 6.8 mm, surrounded by a 1.5 mm transition zone.

Statistical analysis

All statistical analyses were performed using the Statistical Package for Social Sciences (SPSS) software version 26 (IBM Corporation, Armonk, NY, USA). Data were presented as mean ± standard deviation (SD) for continuous variables and frequencies (percentages) for categorical variables. Ocular parameter comparison was performed via analysis of variance (ANOVA). P value of less than 0.05 was considered statistically significant.

Baseline characteristics

Information of baseline characteristics were summarized in Table 1. In this study, a total of 144 myopic eyes from 116 patients were divided into three groups based on pre-surgical retinal conditions: normal group (n=50), untreated group (n=54), and treated group (n=40). The gender distribution showed a majority of males in the normal and treated groups, and a balanced distribution in the untreated group. The average age was around 23 years old across all groups.

Regarding refractive surgery types, a high percentage (78%) of the normal group underwent SMILE surgery, which was higher compared to the untreated (50%) and treated (32.5%) groups. The untreated group showed a more balanced distribution between SMILE (50%) and FS-LASIK (44.44%), with a small percentage (5.56%) opting for EK. The treated group had the lowest percentage of SMILE surgeries (32.5%) and a relatively high percentage of FS-LASIK (44%) and EK (12.5%).

Pre-operative ocular parameters

Table 2 presented the comparison of preoperative ocular parameters among three groups. Axl and SE showed significant differences among the groups. The treated group exhibited the longest Axl (25.78 ± 1.265 mm), followed by the untreated group (25.24 ± 0.866 mm) and the normal group (25.02 ± 1.018 mm) (P = 0.0041). Similarly, the treated group had the most negative mean SE (-5.43 ± 2.145 D), indicating more severe myopia compared to the untreated (-5.17 ± 1.860 D) and normal groups (-4.19 ± 1.723 D) (P = 0.0045).

Other parameters, including UDVA, IOP, corneal curvature, corneal elevation, and PD, showed no significant differences among the groups (P > 0.05).

Preoperative characteristics of retinal lesions

Preoperative retinal lesions were demonstrated in Table 3. In the untreated group, the prevalence of atrophic holes was 3.7%. There were no cases of operculated holes or horseshoe tears in this group. Peripheral retinal degeneration was more common, with 62.96% showing white without pressure, 11.11% with pigmented degeneration, 7.41% with snail-track degeneration, and 5.56% with vitreous traction and snowflake degeneration. Lattice degeneration was present in 3.7% of the untreated group.

In the treated group, retinal holes or tears were more prevalent, with 20% having atrophic holes, 17.5% with operculated holes, and 15% with horseshoe tears. In peripheral retinal degeneration, only lattice degeneration was noted and significantly higher (47.5%).

We also exhibited several fundus images of typical retinal lesions observed in this study. Figure 1 showed the fundus images of retinal lesions in the untreated group, illustrating various types of retinal degeneration: (A) White without pressure, characterized by translucent white areas without associated retinal elevation or pressure; (B) Snail-track degeneration, displaying a shiny, whitish appearance resembling a snail trail; (C) Pigmented degeneration, indicating areas of retinal thinning or atrophy with pigmentation changes; and (D) Snowflake degeneration, with small, white, snowflake-like lesions located in the superior temporal peripheral retina.

Figure 2 showed the fundus images of retinal lesions in the treated group, illustrating various types of retinal degeneration and lesions: (A) Horseshoe tear, a common type of retinal break; (B) Horseshoe tear with prophylactic laser barrage, demonstrating the sealing of the tear to prevent further retinal detachment; (C) Lattice degeneration with hole, showing areas of thinning and tearing in the peripheral retina; and (D) Atrophic hole, a round, well-defined retinal break without significant traction.

Post-operative ocular parameters

Table 4 presented the postoperative ocular parameters among the normal, untreated, and treated groups at 1 day, 6 months, and 12 months after surgery. Across all groups, there were no new cases of peripheral retinopathy observed post-operatively. Visual acuity improved in all groups, with the UDVA showing consistent enhancement: at 12 months, mean logMAR values were -0.08±0.059 for the normal group, -0.04±0.054 for the untreated group, and -0.03±0.057 for the treated group. Other parameters, including SE and IOP, remained stable throughout the follow-up period, indicating overall stability and successful surgical outcomes.

Refractive surgery is a common intervention for correcting myopia, yet the presence of retinal lesions in patients poses unique challenges that necessitate careful consideration.

We strategically divided study eyes into three groups based on fundus conditions: normal group (normal fundus), untreated group (retinal lesion not requiring interventions), and treated group (retinal lesion necessitating preventive treatments). Pre-operative UDVA was worst in the treated group, indicating more severe baseline myopia or associated myopic pathology. Consistently, Axl and SE value were also highest in the treated group, reinforcing the observation that more severe myopia was associated with a higher likely hood of needing treatment. The treated group exhibited a higher incidence of severe retinal diseases, such as retinal tears or holes, compared to the untreated group, suggesting that more severe myopia results in more severe retinal lesions.

Our observations aligned with literatures indicating that excessive elongation of Axl in high myopia often leads to significant stretching and thinning of the retina, which can increase the risk of retinal detachment and tears¹⁹. And the elongation can also reduce choroidal blood flow, causing atrophy and fragile new vessels prone to bleeding²⁰. A cross-sectional survey in 213 myopic patients revealed a high prevalence of peripheral retinal degenerations in high myopia, with retinal holes positively correlated with an axial length of ≥30mm²¹. Zhang et al. previously performed fundus examination in a total of 120 subjects with high myopia and found that snowflake retinal degeneration (27.5%), white without pressure (27.5%), snail-track degeneration (15%), and lattice degeneration (15%) were the most common peripheral retinal changes²². Therefore, early detection of fundus conditions and preventive interventions if necessary are very important before surgeries to ensure patient safety and outcome.

Postoperative follow-ups demonstrated enhanced visual acuity across all patients, with improvements remaining stable at 12 months, highlighting the effectiveness of surgical interventions. Furthermore, the absence of new retinal diseases, in any group postoperatively suggests that the procedures are safe concerning retina structural integrity. Preventive treatment for peripheral retinopathy prior to refractive surgery can further ensure patient safety. Although no new fundus abnormalities were observed during the 12-month follow-up of our study, previous case reports have indicated that RRD can occur 60 months post-refractive surgery²³. Thus, long-term monitoring of fundus condition after surgery is essential, and we strongly advise that the follow-up period be extended as much as possible.

Regarding the selection of refractive surgery, SMILE is currently the least invasive technique with the quickest recovery^{24, 25}. While it still remains some safety concerns due to increased suction time during surgery, despite decreased suction pressure, thereby inducing IOP changes²⁶. For patients without obvious retinal disorders, SMILE would be the preferred choice, consistent with our findings that the normal group had the highest number of SMILE. Conversely, the majority of treated group received FS-LASIK surgery, likely because FS-LASIK exerts a lesser impact on IOP compared to SMILE^{27, 28}, potentially minimizing the exacerbation of pre-existing retinal disorders postoperatively. In the untreated group, the choice between SMILE and FS-LASIK surgeries was evenly split, likely considering the advantages and disadvantages of each technique and patient preferences. The number of EK was the lowest across all groups, as EK has been almost abandoned due to several drawbacks such as severe eye pain or corneal haze postoperatively^{29, 30}.

Our study has some limitations, including a small sample size and insufficient follow-up duration. Future research should involve larger population with longer follow-up periods. Additionally, the fundus examination was limited to fundus photography. Future studies could include additional examination methods to comprehensively assess patients' fundus conditions.

Our study highlights the increased risk of retinal changes in patients with high myopia, emphasizing the need for careful fundus monitoring in refractive surgery candidates pre- and post-operation. These findings support routine fundus evaluations to enhance patient safety and treatment outcomes, potentially leading to more personalized surgical protocols.

Acknowledgements

Not applicable.

Authors’ information

1. Department of Ophthalmology, Zibo Central Hospital, No.54, Gongqingtuan West Road, Zhangdian District, Zibo 255000, Shandong Province, PR China

2. Department of Otorhinolaryngology Head and Neck Surgery，Zibo Central Hospital, No.54, Gongqingtuan West Road, Zhangdian District, Zibo 255000, Shandong Province, PR China

3. Department of Ophthalmology, Aier Eye Hospital Group, Hubin Aier Eye Hospital, Binzhou 256600, Shandong Province, PR China.

Authors’ contributions

Design of the work: Linlin Xu and Yunfei Han. Drafting of the work and substantive revision: Linlin Xu and Yunfei Han. Acquisition and analysis of data: Linlin Xu, Wenqi Song and Huijun Xu. Interpretation of data: Yunfei Han, Huijun Xu and Wenqi Song.

Funding

There was no funding received for this study.

Data Availability

All data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.

Ethic approval and consent to participate

This study followed the tenets of the Declaration of Helsinki and was approved by the Ethics Committee of Zibo Central Hospital, approval number [IEC-form-030-2.0]. The study has been granted an exemption from requiring written informed consent by the Ethics Committee of Zibo Central Hospital. All methods were carried out in accordance with relevant guidelines and regulations.

Consent for publication

Not applicable.

Confict of interest

The authors declare that they have no confict of interest.

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Table 1 Baseline characteristics
	Normal group	Untreated group	Treated group
	(n=50)	(n=54)	(n=40)
Gender (%) Male Female	32(64%) 18(36%)	27(50%) 27(50%)	28(70%) 12(30%)
Age(y)	22.72	23.67	22.93
Surgical technique (%) SMILE FS-LASIK EK	78% 16% 6%	50% 44.44% 5.56%	32.5% 44% 12.5%

Table 2 Comparison of pre-operative ocular parameters
	Normal group	Untreated group	Treated group	P value
	(n=50)	(n=54)	(n=40)
UDVA (logMar)	0.76±0.350	0.79±0.332	0.84±0.385	0.5725
Axl (mm)	25.02±1.018	25.24±0.866	25.78±1.265	0.0041
SE (D)	-4.19±1.723	-5.17±1.860	-5.43±2.145	0.0045
IOP (mmHg)	15.42±2.363	15.29±2.190	15.61±2.666	0.8148
Corneal curvature Front (D) Back (D)	43.14±1.411 -6.28±0.227	43.10±1.433 -6.24±0.230	42.54±1.152 -6.18±0.213	0.0750 0.1215
Corneal elevation Front (D) Back (D)	+1.96±1.212 +2.36±2.481	+2.35±1.216 +1.96±2.046	+2.03±1.143 +1.95±2.791	0.2252 0.5619
PD (mm)	3.22±0.481	3.46±0.830	3.21±0.530	0.4518
CCT (μm)	546.96±25.595	544.41±26.725	555.73±26.839	0.1372

Table 3 Preoperative characteristics of retinal lesions
	Untreated group		Treated group
	(n=54)		(n=40)
Retinal holes or tears
Atrophic hole	2(3.7%)		8(20%)
Operculated holes			7(17.5%)
Horseshoe tear			6(15%)
Peripheral retinal degeneration
White without pressure	34(62.96%)
Pigmented degeneration	6(11.11%)
Snail-track degeneration	4(7.41%)
Vitreous traction	3(5.56%)
Snowflake degeneration	3(5.56%)
Lattice degeneration	2(3.7%)	19(47.5%)

Table 4 Postoperative ocular parameters
	Normal group	Untreated group	Treated group
	(n=50)	(n=54)	(n=40)
1 day
UDVA (logMar)	-0.08±0.059	-0.04±0.054	-0.03±0.057
SE (D)	+0.20±0.313	+0.17±0.281	+0.02±0.304
IOP (mmHg)	11.29±2.312	11.95±2.291	11.09±2.341
Fundus evaluation		No new fundus lesions were observed.

6 months
UDVA (logMar)	-0.09±0.054	-0.04±0.055	-0.04±0.059
SE (D)	+0.19±0.291	+0.17±0.309	+0.43±0.294
IOP (mmHg)	11.42±2.129	12.29±2.332	11.61±2.285
Fundus evaluation		No new fundus lesions were observed.

12 months
UDVA (LogMar)	-0.07±0.060	-0.05±0.055	-0.03±0.058
SE(D)	+0.26±0.311	+0.25±0.295	+0.30±0.301
IOP (mmHg)	11.40±2.324	12.18±2.315	11.33±2.177
Fundus evaluation		No new fundus lesions were observed.

No competing interests reported.

Fundus Evaluation in Myopia: Essential for Pre- and Post-refractive Surgery

Status:

Version 1

Abstract

Objective

Methods

Results

Conclusions

Figures

Backgroud

Methods

Results

Discussion

Declarations

References

Tables

Additional Declarations

Status:

Version 1