Abstract
This study aimed to compare the outcomes of Optical Coherence Tomography-Angiography (OCT-A) with the clinical assessments conducted by an experienced ophthalmologist, as well as to analyze the alterations in the conjunctiva of individuals utilizing spherical scleral contact lenses. OCT-A imaging was conducted on 13 patients (mean age: 34.1 years, 10 males) in a prospective study at two time points: at least 8 h post-lens removal and 1-hour post-lens application. The scleral region in the quadrants (superior, inferior, temporal, and nasal) was designated as the region of interest (ROI), located 3 mm from the limbus. This ROI was further divided into two bands: Band 1 (1.5 mm width under the lens) and Band 2 (1.5 mm width outside the lens). The vascular density ratios in the inferior quadrant were significantly reduced after the lens fitting: ROI (0.362 ± 0.074 post-lens vs. 0.452 ± 0.099 pre-lens, adjusted P-value = 0.027) and Band 1 (0.353 ± 0.075 post-lens vs. 0.462 ± 0.095 pre-lens, adjusted P-value = 0.008). In the superior (P-value = 0.026), inferior (P-value < 0.001), and temporal (P-value < 0.001) quadrants, the degree of conjunctival impingement, as scored by an experienced ophthalmologist using slit photographs, was significantly correlated with OCT-A findings. In conclusion, OCT-A identifies microvascular changes undetectable by slit-lamp examination, providing quantitative insights into vascular alterations from scleral lens use and complementing clinical evaluations.
Keywords: Spherical scleral contact lens, Optical coherence tomography angiography, Conjunctiva
Subject terms: Medical research, Outcomes research
Introduction
Mini scleral contact lenses combine the optical performance of a gas-permeable lens with the larger diameter of other lenses1. These lenses use a standard gas-permeable material, while the overall diameter of the lens is 13 to 18 mm. The large diameter of these lenses increases the stability and comfort of using for the patient. Patients with irregular corneal topography, such as keratoconus (KCN) or after keratoplasty, can easily use mini scleral lenses2–5. Mini scleral lenses can be used to form a “liquid corneal bandage”. On the other hand, the mentioned contact lenses have proven benefits, including their application in treating ocular surface diseases and alleviating pain associated with bullous keratopathy1,2,6–8.
Given the irregular anatomy of the sclera and conjunctiva, as opposed to the uniform design of the contact lens, there is a potential for impingement of the conjunctival vessels during lens wear. This could result in reduced wearing time tolerance for the lens or refractive shifts due to alterations in the tear film beneath the lens2,9.
Optical coherence tomography (OCT) is an interferometric and non-invasive imaging method that provides imaging of retinal and optic nerve layers. Since the introduction of this imaging in 1991, a tremendous change in the diagnosis of various retinal diseases happened10–13. Recent advances, with the introduction of optical coherence tomography-angiography (OCT-A) technology in 2016, have created a key role in investigating functional disorders simultaneously with structural disorders14. OCT-A actually uses the same light source and recording parts as conventional OCT devices. However, since OCT-A measures dynamic changes in OCT data to extract blood flow parameters, it needs a higher speed, better resolution, and higher scanning speed15–17.
The slit-lamp examination is an essential method for assessing the conjunctival response to scleral contact lens use; however, its effectiveness is primarily qualitative and dependent on the observer’s evaluation. Conversely, OCT-A offers a comprehensive, quantitative assessment of vascular density and perfusion18. This sophisticated imaging method facilitates the identification of subtle microvascular changes that may remain undetected during slit-lamp examination18. Probably, OCT-A delivers precise, reproducible data regarding conjunctival vascular alterations, so improving our understanding of the impact of scleral lenses on the ocular surface and assisting in the optimization of lens fitting methodologies18.
In this study, we aimed to investigate the vascular condition of the conjunctiva and to determine its association with the duration of lens wear and the patient’s comfort, utilizing OCT-A imaging. We also aimed to evaluate the parameters observed by OCT-A in comparison with the evaluation of an experienced ophthalmologist. Currently, the trial lens testing time before prescription is limited to a maximum of thirty minutes, making it challenging to predict the degree to which conjunctival impingement may cause intolerance to lens wear over extended periods19. Considering the high cost of these lenses, developing an improved assessment technique for lens fitting and a more precise prediction of potential tolerance is highly beneficial, both clinically and economically.
Methods
Design and setting
The study protocol has been approved by the Tehran University of Medical Science’s Institutional Review Board (IR.TUMS.MEDICINE.REC.1401.056). The guidelines set out in the Helsinki Declaration have been followed by this study. The sample size was calculated based on a previous study18, with a significance level of 0.05 and power of 0.8, yielding 21 eyes, and 22 eyes were enrolled to ensure sufficient statistical power. In this prospective study, all the participants had been wearing scleral contact lenses for a duration of one to two years and had been diagnosed with either KCN or pellucid marginal degeneration (PMD). In the presence of glaucoma, cataracts, diabetic retinopathy, congenital eye disorders, history of thermal and chemical injuries, superior limbic keratoconjunctivitis (SLK), significant corneal opacity or evidence of corneal neovascularization, a history of surgery on the conjunctiva, and the low quality of images obtained with OCT-A, patients were excluded from the study. Also, patients with dry eyes (tear breakup time (TBUT) results below 10 s) were excluded. Any patient had to stop using contact lenses due to corneal neovascularization was also excluded.
Data collection
Patients were subjected to OCT-A (Optovue, RTVue-XR, Zeiss, Cirrus, 5000-HD-OCT) at least 8 h after removing the contact lens and one hour after wearing (without using anesthetic drops and in a room with sufficient light and a temperature of 25–28 C°). OCT-A imaging of conjunctival vessels was performed in all meridians (vertical, horizontal, and oblique) before and after lens wear. Lens insertion was done by the patient and the fit of the lens was confirmed by an experienced ophthalmologist.
Complete slit lamp examinations were performed and slit photos were also taken from patients before and one hour after contact lens fitting (using a Canon EOS D30 SLR camera). A well-experienced ophthalmologist determined the level of impingement across various meridians for each patient, rating it on a scale from 0 to 4 based on slit-lamp photographic analysis, with 4 indicating the most severe degree. Refraction on the lens was performed for the patient and compared with the refraction at the time of prescription. A questionnaire was completed regarding the hours of lens wearing per day and eye redness after removing the lens, as well as vision fluctuations during the wearing time.
The average corneal diameter is 12 mm, while the average diameter of scleral lenses is 15.8 mm. The scleral region in the quadrants (superior, inferior, temporal, and nasal) was identified as the region of interest (ROI), situated 3 mm from the limbus. The ROI was divided into two bands: Band 1, which corresponds to the 1.5 mm region directly beneath the lens, and Band 2, which refers to the adjacent 1.5 mm area outside the lens. The objective of this division was to evaluate vascular alterations in the region directly affected by the lens (Band 1) and in the neighboring, unaffected area (Band 2). The vascular density in both bands was assessed before and after lens application. The total vascular density in each quadrant (superior, inferior, temporal, and nasal) was assessed before and after the application of contact lenses. Examinations took place in November and December 2023.
Image analysis
OCT-A images were extracted. The next steps were done using MATLAB software version 2021b. At first, by using the contrast-limited adaptive histogram equalization (CLAHE) method, the contrast of the vessels in the gray-scale image was improved. The target vessels in the ROI area were separated from the background image and edges. The edge of the limbus was determined and according to the distance from the limbus, the ROI was divided into Band 1 and Band 2 (the radius of each is 1.5 mm). In the next step, Otsu’s thresholding method was used to convert the gray-scale image to binary. This algorithm selects a threshold that minimizes the intra-class variance of black and white pixels in the threshold image. Then, according to the length of the vessels and the calculation of the surface of the vessels, the ratio of the vessel’s area to the entire target area was calculated. Figures 1 and 2, and 3 demonstrate the calculation of vascular density using an OCT-A device before and after scleral lens fitting in different areas of ROI, Band 1, and Band 2 (Figs. 1 and 2, and 3).
Fig. 1.
OCT-A imaging and defining the measurement areas of vascular densities.
Fig. 2.
Slit photo and conjunctival vessels densitometry before and after scleral lens fitting. (A) Ocular surface photo before scleral lens wearing, (B) Vascular densitometry measured with OCT-A before scleral lens wearing, (C) Ocular surface photo in the same patient after the fit of the scleral lens, (D) Vascular densitometry measured with the OCT-A after wearing the scleral lens (the rim of the scleral lens can be recognized as a shadow, which is the border of the Band 1 and Band 2 regions (red arrows)).
Fig. 3.
Image processing for vascular density analysis. (A) The raw OCT-A image obtained during the study. (B) The processed OCT-A image with the region of interest (ROI) delineated in green, showing the targeted analysis area. (C) Overlay of Band 1 (blue) and Band 2 (red) boundaries on the raw OCT-A image, illustrating the segmentation of the ROI based on distance from the limbus. (D) Binarized OCT-A image with Band 1 (blue) and Band 2 (red) overlays, highlighting vessel segmentation for vascular density quantification.
Statistical analyses
Mean (M), standard deviation (SD), median, range, frequency, and percentage were used to present the data. The generalized estimating equation (GEE) method was used to compare the values before and after fitting contact lenses and to compensate for the possible correlation of measurements in two eyes and at two times. Pearson correlation coefficients were employed to assess the relationships between daily hours of contact lens wear and clinical evaluation scores or OCT-A findings across various quadrants. Regression analyses were performed to evaluate the relationship between clinical evaluation scores and vascular density parameters. Regression coefficients (B) indicate the strength and direction of the association between clinical judgment scores and vascular density parameters. All statistical analyses performed by SPSS (IBM Corp. Released 2020. IBM SPSS Statistics for Windows, Version 26.0. Armonk, NY: IBM Corp) and P-value less than 0.05 was considered statistically significant. The analyses were adjusted according to age and gender.
Results
In this study, 13 patients (22 eyes) with a mean age of 34.1 ± 7.6 years (range; 22 to 48 years) participated, of which 10 patients (76.9%) were male. Table 1 summarizes the demographic characteristics of the study subjects (Table 1).
Table 1.
Demographic characteristics of study participants (OD; Oculus Dexter (right eye), OS; Oculus Sinister (left eye), OU; Oculus Uterque (both eyes), KCN; Keratoconus, PMD; Pellucid Marginal Degeneration).
| Parameters | Subgroup | Frequency (percentage %) |
|---|---|---|
| Gender | Male | 10 (76.9) |
| Female | 3 (23.1) | |
| Side involved | Only OD | 3 (23.1) |
| Only OS | 1 (7.7) | |
| OU | 9 (69.2) | |
| Underlying disease | KCN | 11 (84.6) |
| PMD | 2 (15.4) |
Table 2 indicates the parameters of OCT-A before and after using the scleral lens and the changes in these parameters in different quadrants. The total vascular density ratio of ROI in the inferior quadrant was significantly reduced after using the scleral lens (0.362 ± 0.074 after vs. 0.452 ± 0.099 before; un-adjusted p-value = 0.021 and adjusted p-value = 0.027). In the superior quadrant (0.355 ± 0.071 after vs. 0.426 ± 0.114 before; un-adjusted p-value = 0.091 and adjusted p-value = 0.103) and temporal (0.407 ± 0.077 after vs. 0.411 ± 0.055 before; un-adjusted p-value = 0.837 and adjusted p-value = 0.150) the trend of vascular density changes was also decreasing, but these changes were not statistically significant. In contrast, the nasal quadrant exhibited a different trend compared to the other quadrants, showing an increase in vascular density after the lens was used; however, this change was also not statistically significant (0.387 ± 0.059 after vs. 0.348 ± 0.081 before; un-adjusted p-value = 0.186 and adjusted p-value = 0.135) (Table 2; Fig. 4).
Table 2.
Changes of OCT-A variables before and after the spherical scleral contact lens fitting (ROI; Region Of Interest, M; Mean, SD; Standard Deviation, CI; Confidence Interval).
| Parameter | Quadrant | Vascular density (M ± SD) | Change | 95% CI | Un-adjusted P-value | Adjusted P-value | ||
|---|---|---|---|---|---|---|---|---|
| Pre | Post | Lower | Upper | |||||
| ROI | Inferior | 0.452 ± 0.099 | 0.362 ± 0.074 | − 0.091 | 0.014 | 0.167 | 0.021 | 0.027 |
| Nasal | 0.348 ± 0.081 | 0.387 ± 0.059 | 0.042 | − 0.103 | 0.020 | 0.186 | 0.135 | |
| Superior | 0.426 ± 0.114 | 0.355 ± 0.071 | − 0.077 | − 0.012 | 0.167 | 0.091 | 0.103 | |
| Temporal | 0.411 ± 0.055 | 0.407 ± 0.077 | − 0.004 | − 0.037 | 0.045 | 0.837 | 0.150 | |
| Band 1 | Inferior | 0.462 ± 0.095 | 0.353 ± 0.075 | − 0.111 | 0.035 | 0.185 | 0.004 | 0.008 |
| Nasal | 0.37 ± 0.081 | 0.401 ± 0.072 | 0.032 | − 0.092 | 0.028 | 0.297 | 0.232 | |
| Superior | 0.423 ± 0.117 | 0.362 ± 0.079 | − 0.068 | − 0.028 | 0.164 | 0.167 | 0.181 | |
| Temporal | 0.404 ± 0.056 | 0.393 ± 0.09 | − 0.014 | − 0.032 | 0.059 | 0.558 | 0.526 | |
| Band 2 | Inferior | 0.397 ± 0.093 | 0.413 ± 0.095 | 0.027 | − 0.128 | 0.074 | 0.602 | 0.711 |
| Nasal | 0.31 ± 0.09 | 0.367 ± 0.074 | 0.058 | − 0.144 | 0.028 | 0.185 | 0.200 | |
| Superior | 0.379 ± 0.058 | 0.348 ± 0.08 | − 0.031 | − 0.023 | 0.086 | 0.261 | 0.447 | |
| Temporal | 0.438 ± 0.083 | 0.408 ± 0.094 | − 0.034 | − 0.002 | 0.071 | 0.068 | 0.054 | |
Significant values are in bold.
Fig. 4.
Vascular density changes in ROI region in different quadrants after scleral lens fitting.
The vascular density ratio in Band 1 in the inferior quadrant was significantly reduced after using the scleral lens (0.353 ± 0.075 after vs. 0.462 ± 0.095 before; un-adjusted p-value = 0.004 and adjusted p-value = 0.008). In the superior (0.362 ± 0.079 after vs. 0.423 ± 0.117 before; un-adjusted p-value = 0.167 and adjusted p-value = 0.171) and temporal quadrants (0.393 ± 0.09 after vs. 0.404 ± 0.056 before; un-adjusted p-value = 0.558 and adjusted p-value = 0.526) there were also decreasing trend in vascular density changes, but these changes were not statistically significant. The changes in the nasal quadrant had a different trend from the other quadrants and the vascular density increased after using the lens, although this change was not statistically significant (0.401 ± 0.072 after vs. 0.370 ± 0.081 before; un-adjusted p-value = 0.297 and adjusted p-value = 0.232). Vascular density in Band 2 region in the superior (0.348 ± 0.08 after vs. 0.379 ± 0.058 before; un-adjusted p-value = 0.261 and adjusted p-value = 0.447) and temporal quadrants (0.408 ± 0.094 after vs. 0.438 ± 0.083 before; un-adjusted p-value = 0.068 and adjusted p-value = 0.054) indicated a decreasing trend but these changes were not statistically significant. However, this trend in the inferior (0.413 ± 0.095 after vs. 0.397 ± 0.093 before; un-adjusted p-value = 0.602 and adjusted p-value = 0.711) and nasal quadrants (0.367 ± 0.074 after vs. 0.310 ± 0.09 before; un-adjusted p-value = 0.185 and adjusted p-value = 0.200) was increasing, but it was not statistically significant (Figs. 5 and 6).
Fig. 5.
Vascular density changes in Band 1 region in different quadrants after scleral lens fitting.
Fig. 6.
Vascular density changes in Band 2 region in different quadrants after scleral lens fitting.
Table 3 shows the relationship between the quality criteria of clinical judgment evaluated by an experienced ophthalmologist (0 to 4) with the calculated vascular densities in ROI, Band 1, and Band 2 regions by the OCT-A. The results indicate that the clinical judgment of an experienced ophthalmologist in the superior quadrant had a significant association with the findings of OCT-A in ROI region (B = 0.065, P-value = 0.026), while parameters evaluated in other quadrants did not indicate a statistically significant association with OCT-A findings. Similarly, clinical evaluation in the Band 1 region did not show a significant association, however, a significant association in the inferior (B=-0.035, P-value < 0.001) and temporal quadrant (B = 0.028, P-value < 0.001) of the Band 2 region was observed (Table 3).
Table 3.
Correlation of clinical judgment of an experienced ophthalmologist with OCT-A findings (ROI; Region of Interest, CI; Confidence Interval).
| Parameters | Quadrants | B | 95% CI | P-value | |
|---|---|---|---|---|---|
| Lower | Upper | ||||
| Examiner evaluation/ROI | Inferior | 0.047 | − 0.017 | 0.110 | 0.148 |
| Nasal | − 0.006 | − 0.044 | 0.031 | 0.742 | |
| Superior | 0.065 | 0.008 | 0.122 | 0.026 | |
| Temporal | 0.004 | − 0.041 | 0.049 | 0.871 | |
| Examiner evaluation/Band 1 | Inferior | 0.067 | − 0.015 | 0.148 | 0.110 |
| Nasal | − 0.046 | − 0.107 | 0.014 | 0.131 | |
| Superior | 0.053 | − 0.029 | 0.135 | 0.208 | |
| Temporal | 0.022 | − 0.024 | 0.068 | 0.351 | |
| Examiner evaluation/Band 2 | Inferior | − 0.035 | − 0.044 | − 0.026 | < 0.001 |
| Nasal | 0.010 | − 0.133 | 0.154 | 0.888 | |
| Superior | 0.061 | − 0.008 | 0.130 | 0.083 | |
| Temporal | 0.028 | 0.028 | 0.028 | < 0.001 | |
Significant values are in bold.
Table 4 indicates the association between contact lens wearing hours per day and clinical findings observed by an experienced ophthalmologist and OCT-A findings in different quadrants. There is a significant association between hours of contact lens wearing per day and clinical evaluation by an experienced ophthalmologist in the nasal (Pearson correlation; -0.806, p-value; <0.001) and temporal (Pearson correlation; -0.760, P-value; <0.001) quadrants, however, this association is not statistically significant in the inferior and superior quadrants. Also, there is no significant association between the OCT-A imaging findings and contact lens wearing hours per day (Table 4).
Table 4.
Correlation of contact lens wearing hours per day with clinical findings observed by an experienced ophthalmologist and OCT-A findings (ROI; Region Of Interest).
| Quadrants | Clinical evaluation | ROI | Band 1 | Band 2 |
|---|---|---|---|---|
| Inferior | ||||
| Pearson correlation | − 0.347 | − 0.167 | − 0.132 | − 0.260 |
| P-value | 0.114 | 0.603 | 0.716 | 0.672 |
| Nasal | ||||
| Pearson correlation | − 0.806 | − 0.099 | − 0.393 | − 0.086 |
| P-value | < 0.001 | 0.726 | 0.232 | 0.871 |
| Superior | ||||
| Pearson correlation | − 0.367 | − 0.101 | − 0.160 | − 0.297 |
| P-value | 0.101 | 0.743 | 0.659 | 0.808 |
| Temporal | ||||
| Pearson correlation | − 0.760 | 0.085 | 0.079 | 0.430 |
| P-value | < 0.001 | 0.764 | 0.787 | 0.215 |
Significant values are in bold.
Discussion
In summary, our results indicated that total vascular density in ROI and vascular density in Band 1 in the inferior quadrant were significantly reduced after wearing the scleral lens. On the other hand, the clinical judgment of an experienced physician on the degree of conjunctival impingement in the superior quadrant had a significant association with the findings obtained from the calculated vessel density in the ROI region by OCT-A. The clinical judgment of the ophthalmologist had a significant association with the findings of OCT-A in Band 2 in the inferior and temporal quadrants. There was a significant correlation between the hours of contact lens wearing per day and the clinical assessment of conjunctival impingement in the nasal and temporal quadrants, but the changes in OCT-A parameters have no significant correlation with the hours of scleral lens wearing.
According to the results of our study and review of existing literature, this study is a pioneering study on the clinical application of OCT-A for the conjunctival vasculature in scleral lens wearers. These findings indicate that OCT-A may be a promising non-invasive imaging tool for investigating and tracking changes in conjunctival vessels18. Generally, the results of the study indicate that the vascular density of the conjunctiva decreases in many quadrants after fitting spherical scleral contact lenses although this trend was increasing in the nasal quadrant of ROI, band 1, and 2 area. According to the previous studies, it seems that the reason for this different trend in the nasal quadrant compared to other quadrants is more flattening of the nasal sclera secondary to the anterior insertion of the medial rectus muscle compared to other rectus muscles20,21. Of course, the changes in many of the quadrants were not statistically significant, but it would be possible to make a more accurate assessment by increasing the sample size of the study. These findings may raise questions about the long-term use of contact lenses due to possible changes in the vascular layer of the conjunctiva that can cause unwanted consequences such as corneal edema, epithelial defects, peripheral corneal neovascularization, and scarring22,23.
In the study of Jesus et al.18, the density of conjunctival vessels in patients using scleral contact lenses was investigated in 23 patients diagnosed with KCN using OCT-A. In this study, a different approach was taken compared to our method, as only a 6 × 6 mm area within the nasal sclera of the patients was assessed for conjunctival vascular density while wearing the contact lens and 15 min after its removal. The results of this study revealed that the vascular density in contact lens users was significantly lower than in patients without contact lenses (69.81 ± 2.63% compared to 71.75 ± 2.97%). Therefore, a hypothesis is raised that the use of a scleral contact lens can reduce the vascular density of the areas under the contact lens by creating prolonged indentation of conjunctival vessels. In line with this hypothesis, Gimenez-Sanchis et al. investigated the potential use of OCT-A to assess the peripheral fit of scleral contact lenses in a 27-year-old male emmetropic volunteer with a healthy cornea. Three lenses were fitted with sagittal heights of 4200, 4800, and 5600 micrometers respectively (the standard measurement suggested a scleral lens with a sagittal height of 4200 micrometers). Using OCT-A, the effect of the scleral lens on conjunctival vascular flow was evaluated by observing the area of vascular occlusion of 0, 25, and 75% respectively with 4200, 4800, and 5600 μm lenses (according to sagittal height)24.
The notable disparities in vascular density alterations between the inferior and superior quadrants across ROI, Band 1, and Band 2 regions are significant yet difficult to elucidate decisively. Although we excluded participants with SLK and other conjunctival disorders, factors such as previous medication usage, toxic drug reactions, eyelid abnormalities, or asymmetrical mechanical effects of scleral lenses may have influenced these quadrant-specific variations. The reduction in vascular density in the inferior and superior quadrants of the ROI and Band 1 was consistent; however, statistical significance was attained only in the inferior quadrant, suggesting the potential relevance of localized factors. The differing patterns noted in Band 2, characterized by an increase in vascular density in the inferior quadrant and a decrease in the superior quadrant, underscore the complexity of these interactions. The findings underscore the necessity for further research involving larger sample sizes and more comprehensive criteria, including conditions such as SLK, eyelid abnormalities, and toxic conjunctival reactions, to improve the understanding of the biomechanical and vascular effects of scleral lenses.
In our study, an additional method was utilized to assess the changes in conjunctival vessels following contact lenses wearing. This involved a clinical examination conducted by a skilled ophthalmologist using slit photography, with the results being compared to the findings of OCT-A. The results demonstrated that in some areas clinical observations were in line with the OCT-A findings however, this association was not seen in most of the quadrants. It seems that perhaps the use of slit photos instead of a slit lamp examination has reduced the accuracy of the clinical evaluation. Therefore, some recommendations such as increasing the quality of slit photos and conventional slit lamp examination should be considered to increase the reliability of clinical evaluation. Also, in the next studies, the slit lamp examination should be compared with slit photos in the evaluation of impingement of conjunctival vessels after scleral lens wear. If the facilities for OCT-A imaging are not available, performing a slit photo of the patient and evaluating it by a remote physician (telemedicine) can help in investigating the conjunctival impingement and causes of contact lens intolerance.
Originally in this study OCT-A was used to estimate the structure and flow of the conjunctival vasculature, and is still being tested for other clinical applications and could be a promising tool for evaluating proper contact lens fitting25–27. However, it seems that it is possible to overcome existing concerns by using custom-made contact lenses, which are designed based on the mapping of the cornea and sclera of each patient28,29.
Our study had some limitations one of them was the small sample size. Another is the inclusion of only patients with corneal ectasia (KCN and PMD). Another limitation, which was also mentioned in other similar studies18,24, is that the imaging parameters measured in our study were for a short period (less than 60 min after contact lens wearing). Perhaps, in the case of longer follow-up of patients and longer use of contact lenses (more than 1 h), the parameters of vascular density will decrease more and the changes will be significant. Therefore, it is recommended to design a study with a larger sample size that examines the changes in the vascular density of the conjunctiva for a longer period. On the other hand, the ability of OCT-A device segmentation is not optimal for separating the conjunctival vessels from the superficial scleral vessels25–27, and it seems that by increasing the capabilities of the device, we can achieve more accurate results.
Conclusion
To conclude, OCT-A can be an appropriate device to evaluate conjunctival vessels after fitting spherical scleral contact lenses to prevent indentation of conjunctival vessels and decrease in pre-limbal blood flow. Also, sometimes clinical observation of an experienced ophthalmologist could be associated with the changes in OCT-A findings and predict conjunctival impingement after scleral lens fitting.
Acknowledgements
The authors would like to appreciate the outstanding support of Dr. Majid Zamani and Mrs. Leila Noori for conducting this study.
Author contributions
F.A and P.A prepared idea, M.S and M.K prepared proposal, F.A, M.S, and Z.M collected data, F.A and M.S analyzed data and H.A prepared and finalized draft. All authors read and proofed final article.
Funding
There were no specific funding sources for this study.
Data availability
The data that support the findings of this study are available upon reasonable request from the corresponding author.
Declarations
Competing interests
The authors declare no competing interests.
Ethics declarations
The study had been approved by the local ethics committee of Tehran University of Medical Sciences according to Helsinki ethical principles (IR.TUMS.MEDICINE.REC.1401.056).
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The data that support the findings of this study are available upon reasonable request from the corresponding author.