Detection of retinal nerve fiber layer in patients with high myopia complicated with glaucoma by optical coherence tomography

Abstract

Objective:

To detect the changes in the thickness of the Retinal Nerve Fiber Layer (RNFL) in patients with High Myopia (HM) complicated with glaucoma through Optical Coherence Tomography (OCT).

Methods:

80 patients (160 eyes) with HM complicated with glaucoma treated from March 2018 to March 2020 were enrolled as the experimental group, and 60 healthy volunteers (120 eyes) undergoing physical examination in the same period were selected as the control group. OCT measured their RNFL thicknesses.

Results:

Compared with that in the control group, the nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness in the experimental group was significantly decreased, while the temporal RNFL thickness was significantly increased in the experimental group (P < 0.05). According to the diopter, patients in the experimental group were assigned into group A (n = 25, 50 eyes, diopter range: ≥ −6.00 D and ≤ −8.00 D), group B (n = 30, 60 eyes, diopter range: > −8.00 D and ≤ −10.00 D) and group C (n = 25, 50 eyes, diopter range: > −10.00 D). The nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness in group A were significantly greater than those in groups B and C (P < 0.05). Spearman correlation analysis revealed that the absolute value of diopter was negatively correlated with the nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness (P < 0.05), and positively correlated with the thickness of temporal RNFL (P < 0.05).

Conclusion:

In patients with HM complicated with glaucoma, RNFL is thinner in all quadrants except for temporal RNFL.

Keywords

Optical coherence tomography high myopia glaucoma retinal nerve fibre layer thickness

1. Background

Glaucoma, triggered by chronic degenerative lesions of the optic nerve, is an irreversible eye disease that results in blindness. A series of eye conditions known as glaucoma are associated with increased intraocular pressure and cause gradual damage to the optic nerve. It is one of the world's main causes of permanent blindness; thus, early identification is essential. Surgery, laser therapy, and medication are available as forms of treatment. According to research, with the aggravation of the ageing population currently, the morbidity rate of this disease is increasing, and the age group shows a younger trend.¹ With the widespread application of mobile phones, computers and other electronic devices, the incidence rate of myopia, especially High Myopia (HM), has increased dramatically. Severe nearsightedness, known as high myopia (HM), results in an eye that is too long, making distant things look hazy. Early identification and treatment—such as surgical or corrective lenses—are essential to avoid problems and maintain vision. HM is a kind of severe ametropia, usually with diopter > −6.0 D or axial length >26 mm, with relatively severe fundus lesions accompanying it.² HM is an independent risk factor for glaucoma.³ The study of Usui et al. on 140 patients with various degrees of myopia suggested that the probability of Primary Open-Angle Glaucoma (POAG) was increased in patients with HM.⁴ In patients with HM, the ocular axis is longer, the anterior chamber is deeper, and the sclera of the eyeball wall is relatively soft. Moreover, the degeneration of the posterior pole of the fundus will produce various degrees of visual field changes. As a result, the intraocular pressure measured by a tonometer is generally affected by sclera hardness and is on the low side. Hence, effective diagnosis and treatment of patients with HM complicated with glaucoma is helpful to control the disease. Since the intraocular pressure of POAG may not increase obviously, the onset of the disease is insidious, and the disease progress is slow. HM combined with POAG makes the clinical features even more complicated. Moreover, the distant vision of HM patients is poor, and they lack sensitivity and alertness to vision decline. Therefore, searching for appropriate monitoring indexes for timely diagnosis and early intervention of the disease has been an urgent problem that needs to be solved by clinicians.⁵ Retinal Nerve Fiber Layer (RNFL) defect is one of the early changes of optic nerve damage in primary glaucoma, also considered the most important sign of glaucoma nerve degeneration.⁶ Retinal nerve fibre layer thinning can occur in people with high myopia and glaucoma, which can cause vision field abnormalities and possibly blindness. Improved early identification and treatment techniques can result from understanding this overlap in OCT imaging. Further study is required to pinpoint the precise RNFL thinning patterns that will result in improved OCT algorithms and novel imaging methods. RNFL thickness is a parameter that can reflect the function of retinal ganglion cells and monitor the progression of diseases.⁷ Therefore, quantitative measurement of RNFL thickness has become a research focus in the early diagnosis of glaucoma. Optical coherence tomography (OCT) is an imaging technique developed in recent years that utilizes the basic principle of weak coherence light interferometers and can measure the RNFL thickness quantitatively. A non-invasive imaging method called optical coherence tomography (OCT) uses light waves to create comprehensive retina and optic nerve pictures. This technology can help with the diagnosis and follow-up of several eye disorders, including age-related macular degeneration, diabetic retinopathy, and glaucoma. It has good diagnostic value for retinal ganglion cell apoptosis and nerve fibre loss in glaucoma.⁸ Naresh investigates how to process ECG signals in an Internet of Things (IoT) health monitoring system using the Discrete Wavelet Transform (DWT). It focuses on effective non-stationary signal analysis, acquisition, preprocessing, feature extraction, and real-time IoT-based transmission to cloud servers.⁹ Poovendran investigates how big data medical research may be improved by utilizing RFID and blockchain technologies in the healthcare industry. A blockchain-based architecture protects patient privacy, security, and data integrity by recording real-time physiological signal data. Massive data is managed by fog computing, which guarantees resilience and scalability. This strategy improves the efficacy of medical data exchange, helping patients and furthering medical research.¹⁰ Raj, a new technique, preprocesses the ALLIDB1 dataset with synthetic data to solve the problem of early detection of acute lymphoblastic leukaemia (ALL). It was trained using Improved You Only Look Once Version Four (YOLO v4) and uploaded into the Hadoop environment. This increases the accuracy of healthy and blast cell identification and detection, improving the overall management of this deadly malignancy.¹¹ In this study, OCT was used to study the thickness of RNFL in patients with HM complicated with glaucoma, which is reported as follows:

2. Methods

A total of 80 patients (160 eyes) with HM complicated with glaucoma treated in our hospital from March 2018 to March 2020 were enrolled as the experimental group, including 26 males and 54 females aged 19–31 years old, with a mean of (29.62 ± 3.52) years old. Inclusion criteria¹²: (1) Patients without a family history of glaucoma, (2) those with binocular disease, and (3) those without systemic diseases (such as diabetes, hypertension and intracranial lesions) that can cause eye lesions. Exclusion criteria¹³: (1) Patients showing poor cooperation during examination, (2) those diagnosed with amblyopia, severe cataract, keratopathy or other ophthalmopathy, (3) those with macular or other retinal diseases, (4) those in premonitory stage, acute attack stage, remission stage or absolute stage of primary acute angle-closure glaucoma, or (5) those with craniocerebral trauma or lesion, diabetes, hypertension or other systemic diseases or histories. Another 60 healthy volunteers (120 eyes) undergoing physical examination in our hospital during the same period were selected as the control group, including 19 males and 41 females aged 18–32 years old, with a mean of (29.71 ± 3.61) years old. Patients with corneal, lens or vitreous opacity, those with retinopathy, and those who could not cooperate in the relevant examinations in the present study were excluded from both groups. There were no significant differences in the general data, such as in the sex constituent ratio and age, between the two groups (P > 0.05), which were comparable. The Ethics Committee approved this study, and all the subjects were informed of this study and signed the informed consent.

2.1 Examination methods

OCT was conducted in both groups by the same examiner. The patients were asked to sit in their position with their mandible placed in the jaw frame. The internal fixation method was applied, and 200 × 200 optic papilla scanning mode was adopted for scanning. The circular tomography of 512 axial scanning points of the RNFL with a diameter of 3.46 mm centred on the optic disc was performed using the RNFL 3.46 program, and the RNFL thickness was obtained automatically by the computer. Patients in the experimental group were examined before treatment.¹³

2.2 Statistical analysis

SPSS16.0 software was utilized for statistical analysis. The numerical data were expressed as percentage (%), and the chi-square test (χ²) was employed for comparison between groups. SPSS was selected based on its extensive statistical toolkit, easy-to-use interface, and widespread application in academic and professional contexts. Its powerful data management and visualization features make it the perfect option for this study's investigation. The quantitative data were expressed as mean ± standard deviation (`χ ± s), and an independent-sample t-test was used for mean comparison between the two groups. One-way ANOVA was used for comparison between groups, LSD-t test was employed for further pairwise comparison, and Spearman correlation analysis was adopted for correlation analysis. P < 0.05 suggested that the difference was statistically significant.

3. Results

3.1 RNFL thicknesses of control and experimental groups

Compared with the control group, the nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness were significantly decreased. In contrast, the temporal RNFL thickness was significantly increased in the experimental group (P < 0.05) (Table 1).

Table 1.
RNFL thicknesses of control and experimental groups (`χ ± s, μm).

Control group (n = 120) Experimental group (n = 160) t P

Nasal 68.74 ± 8.27 45.37 ± 7.06 25.458 0.000

Supratemporal 110.95 ± 15.42 91.46 ± 15.87 19.681 0.000

Subnasal 111.52 ± 13.26 76.13 ± 15.61 20.003 0.000

Temporal 85.14 ± 9.59 97.28 ± 19.23 6.347 0.000

Supranasal 149.65 ± 14.11 131.41 ± 17.62 9.317 0.000

Infratemporal 156.35 ± 14.27 138.54 ± 13.41 10.699 0.000

Overall mean thickness 104.68 ± 6.62 90.35 ± 8.27 15.598 0.000

	Control group (n = 120)	Experimental group (n = 160)	t
Nasal	68.74 ± 8.27	45.37 ± 7.06	25.458
Supratemporal	110.95 ± 15.42	91.46 ± 15.87	19.681
Subnasal	111.52 ± 13.26	76.13 ± 15.61	20.003
Temporal	85.14 ± 9.59	97.28 ± 19.23	6.347
Supranasal	149.65 ± 14.11	131.41 ± 17.62	9.317
Infratemporal	156.35 ± 14.27	138.54 ± 13.41	10.699
Overall mean thickness	104.68 ± 6.62	90.35 ± 8.27	15.598

3.2 RNFL thicknesses of different diopters in the experimental group

According to the diopter, patients in the experimental group were assigned into group A (n = 25, 50 eyes, diopter range: ≥ −6.00 D and ≤ −8.00 D), group B (n = 30, 60 eyes, diopter range: > −8.00 D and ≤ −10.00 D) and group C (n = 25, 50 eyes, diopter range: > −10.00 D). The nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness in group A were significantly increased than that in groups B and C (P < 0.05) (Table 2).

Table 2.
RNFL thicknesses of different diopters in the experimental group (`χ ± s, μm).

Group A (n = 50) Group B (n = 60) Group C (n = 50) F P

Nasal 48.12 ± 6.67 43.22 ± 7.03* 37.19 ± 5.92^# 20.672 0.000

Supratemporal 94.25 ± 17.06 90.79 ± 12.12* 79.46 ± 17.61^# 8.547 0.000

Subnasal 83.33 ± 12.38 67.03 ± 13.25* 62.10 ± 11.21^# 2.478 0.000

Temporal 95.24 ± 19.08 100.23 ± 7.83* 102.07 ± 21.29^# 3.647 0.000

Supranasal 135.46 ± 15.27 121.63 ± 4.85* 128.33 ± 18.64^# 10.258 0.000

Infratemporal 143.42 ± 20.54 132.95 ± 6.36* 127.39 ± 16.90^# 11.308 0.000

Overall mean thickness 93.30 ± 7.56 88.65 ± 6.93* 81.12 ± 6.49^# 12.681 0.000

	Group A (n = 50)	Group B (n = 60)	Group C (n = 50)	F
Nasal	48.12 ± 6.67	43.22 ± 7.03*	37.19 ± 5.92^#	20.672
Supratemporal	94.25 ± 17.06	90.79 ± 12.12*	79.46 ± 17.61^#	8.547
Subnasal	83.33 ± 12.38	67.03 ± 13.25*	62.10 ± 11.21^#	2.478
Temporal	95.24 ± 19.08	100.23 ± 7.83*	102.07 ± 21.29^#	3.647
Supranasal	135.46 ± 15.27	121.63 ± 4.85*	128.33 ± 18.64^#	10.258
Infratemporal	143.42 ± 20.54	132.95 ± 6.36*	127.39 ± 16.90^#	11.308
Overall mean thickness	93.30 ± 7.56	88.65 ± 6.93*	81.12 ± 6.49^#	12.681

*P < 0.05 vs. group A, ^#P < 0.05 vs. group B.

3.3 Correlation between diopter and RNFL thickness in the experimental group

The absolute value of diopter was negatively correlated with the nasal, supratemporal, subnasal, and infratemporal RNFL thickness and overall mean RNFL thickness and positively correlated with the thickness of temporal RNFL (Table 3).

Table 3.
Correlation between diopter and RNFL thickness in the experimental group.

r P

Nasal −0.493 P < 0.001

Supratemporal −0.367 P < 0.001

Subnasal −0.483 P < 0.001

Temporal 0.227 0.04

Supranasal −0.219 0.05

Infratemporal −0.342 P < 0.001

Overall mean thickness −0.495 P < 0.001

	r	P
Nasal	−0.493	P < 0.001
Supratemporal	−0.367	P < 0.001
Subnasal	−0.483	P < 0.001
Temporal	0.227	0.04
Supranasal	−0.219	0.05
Infratemporal	−0.342	P < 0.001
Overall mean thickness	−0.495	P < 0.001

4. Discussion

Glaucoma is the second leading cause of blindness worldwide, the most typical manifestation of which is pathologically increased intraocular pressure, sunken atrophy of the optic nerve, defect, and reduction of the visual field. Its pathological damage is based on the damage of optic nerve cells and the loss of optic nerve fibres. Since the ganglion cell layer and nerve fibre layer account for 30–35% of the thickness of the overall retina, the pathological damage of glaucoma is manifested as the changes in the RNFL thickness.^14,15 However, in clinical research, the interference of other diseases, especially HM, often leads to the missed diagnosis of glaucoma. HM is a chronic latent glaucoma. The fundus of HM is usually accompanied by evident changes in the optic disc and retina, such as optic disc enlargement, deformation, discolouration, periodic lesions and retinal thinning. Retina, choroid atrophy, and posterior scleral staphyloma will occur in severe cases. As a result, when HM is complicated with POAG, the early fundus changes of POAG are easily covered by the fundus lesions of HM, which reduces the chances of early diagnosis and even delays treatment.¹⁶ Therefore, searching for accurate and sensitive detection indexes and simple and easy detection methods are helpful to the early screening, diagnosis and treatment of HM complicated with POAG and are conducive to improving patients’ quality of life and decreasing the blindness rate.

Although routine examinations such as fundus photography and ophthalmoscope play an important role in the examination of morphological changes of optic disc and RNFL, this method is subjective, and its accuracy depends on the accumulation of clinical experience of glaucoma doctors. The data obtained cannot or is not easily preserved, which is not conducive to comparison and later follow-up.¹⁷ However, OCT is a rapidly developing imaging technology in recent years, which mainly utilizes the principle of weak coherence interferometer to detect the signals to incident weakly coherent light at different depths and obtain the image of biological tissue structure by scanning to observe the subtle changes of retinal structure in vivo. It is a diagnostic method with high resolution, safety, good repeatability and non-invasiveness, which has been widely applied in the early diagnosis and follow-up of glaucoma.¹⁸

RNFL is composed of ganglion and glial cells, and there are only two layers around the retina, reflecting the number of ganglion cell axons. The survival of ganglion cells can be indirectly understood by measuring the RNFL thickness, which is currently one of the objective and quantifiable indexes for evaluating glaucoma.¹⁹ Herein, OCT was applied to detect the RNFL thickness in patients with HM complicated with glaucoma and normal controls. It was found that the thickness of nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness in patients with HM complicated with glaucoma were smaller than those in normal controls, suggesting that OCT can accurately measure the thickness of RNFL. OCT is a high-resolution imaging technique for biological tissues, which can obtain images of pathological changes in eye tissue in vivo. Moreover, OCT has relatively high resolution, so it has high accuracy in the early diagnosis of glaucoma. Previous clinical studies on the thickness of RNFL in patients with HM have found that the RNFL in the upper, lower and nasal quadrants of HM patients become thinner.²⁰ In this study, the RNFL thickness was compared among patients with HM complicated with glaucoma of different diopters. It was found that the nasal, supratemporal, subnasal, supranasal, and infratemporal RNFL thickness and overall mean RNFL thickness in group A (diopter range: −10.00 to −11.00 D) were significantly greater than those in group B (diopter range: −12.00 to −14.00 D) and group C (diopter range: ≥ −15.00 D), implying that the mean RNFL thickness decreases with the increase of diopter in HM. The results of Spearman correlation analysis manifested that the absolute value of diopter was negatively correlated with the nasal, supratemporal, subnasal, and infratemporal RNFL thickness and overall mean RNFL thickness and positively correlated with the thickness of temporal RNFL. The study of Zheng et al. showed a negative correlation between the absolute value of myopic diopter and the RNFL thickness, and the RNFL thickness decreased gradually with the increase of absolute diopter of myopia, in consistency with the results of this study.²¹

In summary, the RNFL in each quadrant of patients with HM complicated with glaucoma becomes thinner except the temporal RNFL. However, there were some limitations. The study's sample size and the region and race of the subjects were limited, and the observation index was relatively single, so the results of this study still need to be confirmed by further research.

Statements and declarations

Code availability

Not applicable.

Authors’ contributions

Xin Wang, Yinglang Zhang, is responsible for designing the framework, analyzing the performance, validating the results, and writing the article. Hongbo Hu, Ning Wei, is responsible for collecting the information required for the framework, provision of software, critical review, and administering the process.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability statement

No datasets were generated or analyzed during the current study.

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