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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 35  |  Issue : 3  |  Page : 1479-1486

Evaluation of manual keratoscope-assisted implantation of intrastromal cornealring segments in patients with keratoconus


1 Department of Ophthal mology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Ophthalmology, Eye City Center, Al Sadat City, Menoufia, Egypt

Date of Submission21-Jan-2022
Date of Decision04-Mar-2022
Date of Acceptance08-Mar-2022
Date of Web Publication29-Oct-2022

Correspondence Address:
Hend G. A. Ghonemy
Department of Ophthalmology, Eye City Center, Al Sadat City, Menoufia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_33_22

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  Abstract 


Objective
To evaluate the use of manual keratoscope intraoperative to improve the outcome of intracorneal ring segment (ICRS) implantation in patients with keratoconus.
Background
Keratoconus is a bilateral, progressive, noninflammatory disease of the cornea that often leads to high myopia and astigmatism. It seems to be a multifactorial disease with an unknown exact etiology that impairs the quantity and quality of vision secondary to thinning in and protrusion of the cornea. This results in irregular astigmatism with or without myopia.
Methods
This was a randomized prospective cohort, interventional case series study conducted at Tiba Ophthalmic Center, Menoufia during the period from September 2018 to September 2020 on patients with keratoconus. The study included a sample of keratoconus patients planned for femto-laser-assisted ICRS implantation. The participants were randomly divided into two subgroups according to the use of manual keratoscope intraoperatively: Group A: blind implantation of ICRS without keratoscope. Group B: keratoscope-assisted ICRS implantation.
Results
According to K and Max elevation, there was a statistically significant difference between groups. Regarding Max elevation, Group B showed a higher Max elevation (front) than Group A. Within each group, there was a statistically significant difference postoperative.
Conclusion
The use of manual keratoscope improved best spectacle-corrected visual acuity with better maximum front elevation and anterior chamber depth of cornea in keratoconus patients' postoperative when compared with the blind implantation of ICRS.

Keywords: cornea, intracorneal ring segments, keratoconus, keratoscope


How to cite this article:
Khairy HA, Abdelaziz MS, Ghonemy HG, Zaky MA. Evaluation of manual keratoscope-assisted implantation of intrastromal cornealring segments in patients with keratoconus. Menoufia Med J 2022;35:1479-86

How to cite this URL:
Khairy HA, Abdelaziz MS, Ghonemy HG, Zaky MA. Evaluation of manual keratoscope-assisted implantation of intrastromal cornealring segments in patients with keratoconus. Menoufia Med J [serial online] 2022 [cited 2024 Mar 29];35:1479-86. Available from: http://www.mmj.eg.net/text.asp?2022/35/3/1479/359501




  Introduction Top


Keratoconus is a bilateral, progressive, noninflammatory disease of the cornea that often leads to high myopia and astigmatism with an estimated prevalence of ~1 in 2000[1]. In the general population, the incidence of keratoconus is estimated to be between 50 and 230 per 100 000[2]. It seems to be a multifactorial disease with an unknown exact etiology that impairs the quantity and quality of vision secondary to thinning in and protrusion of the cornea. This results in irregular astigmatism with or without myopia[3]. Despite the fact that only one eye may be affected initially, keratoconus ultimately affects both eyes.

The conservative management of keratoconus in the early stages consists of spectacle correction or rigid contact lenses[4]. In more advanced stages with severe corneal irregular astigmatism and stromal opacities, surgical treatment with deep lamellar keratoplasty and penetrating keratoplasty (PK) should be considered[5]. Intracorneal ring segments (ICRS) were designed with the goal of delaying or avoiding corneal grafts in keratoconus patients. It represents a prominent evolution in the management of keratoconus through flattening the central corneal curvature to achieve a refractive adjustment due to the removable and tissue-saving nature of the technique.

The high efficiency of Intacs in correcting keratoconic eyes has been reported by several authors. ICRS implantation in post-Lasik ectasia appears to be safe and effective in decreasing myopia, corneal steepness, and decentration of the corneal apex and offers potential improvement of uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) in keratoconus patients[6]. The segments induce an “arc-shortening effect” on the corneal lamellae and flatten the corneal center, as well as shift the corneal apex to a more central position that improves contact lens fit and comfort, thereby optimizing best-corrected visual acuity (BCVA).

The ideal candidates for ICRS have moderate spherical equivalents (SE) and average keratometry readings of less than 65 D[6]. The high accuracy cuts to the corneal tissue demonstrated by femtosecond lasers in refractive surgery have generated new inquiry on their application into tunnel creation for precision ICRS insertion.

The advantages of femtosecond channel creation over mechanical approaches are the following: a more uniform dissection is created; the results and ICRS placement are more consistent; and because it is minimally invasive, there is less patient discomfort and quicker recovery[7].

Information about corneal curvature can be obtained with a variety of instruments that reflect the images of multiple concentric circles from the corneal surface. These devices allow an analysis of corneal curvature in zones both central and peripheral to those measured by keratometry. In general, on steeper parts of the cornea, the reflected mires appear closer together and thinner and the axis of the central mire is shorter. Conversely, along the flat axis, the mires are farther apart and thicker, and the central mire is longer.

The handheld Placido disk is a keratoscope with a flat target. Collimating keratoscopes use rings inside a column or a curve to maximize the area of the ocular surface that can reflect the target mires. Photo keratoscopy preserves the virtual image of concentric circles on film, and video keratoscopy stores the images on video[8]. The aim of this study was to evaluate the use of manual keratoscope intraoperative to improve the outcome of ICRS implantation in patients with keratoconus.


  Methods Top


A randomized prospective cohort study was conducted at Tiba Ophthalmic Center, Menoufia during the period from September 2018 to September 2020 on patients with keratoconus. The study included a sample of keratoconus patients planned for femto-laser-assisted ICRS implantation. The participants were randomly divided into two subgroups according to the use of manual keratoscope intraoperatively: Group A: blind implantation of ICRS without keratoscope. Group B: keratoscope-assisted ICRS implantation.

Ethical considerations: all study procedures were carried out after approval by the Ethical Committee of Menoufia Faculty of Medicine with a serial number (3-2-0190PHT45). Participants' names were kept on a password-protected database and linked only with a study identification number for this research. All participants in this study received a detailed explanation about the aim, objectives, and methodology of the study before enrollment.

All participants included in this study were selected according to inclusion and exclusion criteria as follows. Inclusion criteria: age between 15 and 35 years, phakic patients with clear lenses, confirmed keratoconus based on clinical and topography findings, corneal thinnest point >500 μm at the incision site (5.5 mm from corneal center), and maximum keratometry of 60 D based on Penta Cam readings.

Exclusion criteria: pseudophakic or cataract, corneal thinnest point <500 μm at the incision site, corneal scarring in either eye, previous eye surgery (including corneal cross-linking), ocular surface or tear problems, and coexistence of ocular pathology other than keratoconus.

All selected patients included in this study were subjected to the following: complete history taking: personal history including: age, complaint, ocular, trauma or disease, optical correction: glasses, contact lenses, and any systemic medical diseases, for example, diabetes mellitus. Ophthalmic examination included the BCVA. After refraction, BCVA was estimated using pin hole and Landolt's broken ring chart that was recorded as its decimal equivalent, Slit-lamp bio microscopy: the cornea was examined for evidence of the corneal scar, corneal edema, or keratotic precipitates. The anterior chamber examined for depth, regularity, aqueous flare, and cells and applanation tonometry to record baseline intraocular pressure. Fundus examination using auxiliary lenses (+78 D lenses) to examine central and mid-peripheral retina to exclude possible pathology for example, cystoid macular edema, retinal breaks, macular scars, etc., and special investigations (corneal topography) included corneal topography performed in all cases using a pentacam system (Oculus Wetzlar, Germany) to document keratoconus.

Statistical analysis

Results were collected, tabulated, statistically analyzed by IBM personal computer and statistical package SPSS version 22 (IBM Corp, 2013, Armonk, NY). Two types of statistical analysis were done: descriptive statistics, for example, percentage (%), mean (x), and SD and analytic statistics included χ2, Student's t-test, and Analysis of variance (ANOVA) test. P value <0.05 was considered statistically significant and P value <0.01 was considered statistically significant.


  Results Top


According to demographic data: 20 patients ranged in age between 17.0 and 35.0 years with a mean age of 26.75±4.97 years for Group A and 20 patients ranged in age between 16.0 and 40.0 years with a mean age of 28.25±7.08 years for Group B. There was a statistically nonsignificant difference between the two groups regarding to mean of age. Group A had 16 males and 4 females, whereas Group B had 14 males and 6 females. There was a statistically nonsignificant difference between sex distributions in the two groups [Table 1].
Table 1: Comparison between the two studied groups according to demographic data

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Regarding refraction sphere (preoperative and postoperative), refraction cylinder sphere (preoperative and postoperative), and BSCVA (preoperative), there was a statistically nonsignificant difference between groups, whereas regarding BSCVA (postoperative), there was a statistically significant difference between groups. Group B showed a higher BSCVA than Group A [Table 2].
Table 2: Comparison between the two studied groups according to refraction and BSCVA

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There was a statistically nonsignificant difference between groups. Regarding SE (preoperative and postoperative) within each group, there was a statistically significant difference. Both groups showed a decrease in SE, whereas regarding anterior chamber depth (ACD) (preoperative and postoperative) within each group, there was a statistically significant difference in postoperative [Table 3].
Table 3: Comparison between the two studied groups according to SE and ACD

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Regarding K1 (preoperative), K2 (preoperative), K max (preoperative), Max elevation (front) (preoperative), and Max elevation (back) (preoperative and postoperative), there was a statistically nonsignificant difference between groups. Regarding K1 (postoperative), K2 (postoperative), K max (postoperative), Max elevation (front) (postoperative), there was a statistically significant difference between groups. Group B showed a higher BSCVA than Group A. Regarding K1 (postoperative), K2 (postoperative), K max (postoperative), Group B showed a lower K1, K2, and K max than Group A, whereas regarding Max elevation (front) (postoperative), Group B showed a higher Max elevation (front) than Group A, whereas within each group, there was a statistically a significant difference postoperative [Table 4].
Table 4: Comparison between the two studied groups according to K and Max elevation

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Regarding thinnest location and corneal volume (preoperative and postoperative), there was a statistically nonsignificant difference between groups. As well as within each group, there was a statistically nonsignificant difference [Table 5].
Table 5: Comparison between the two studied groups according to thinnest location and corneal volume

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  Discussion Top


Keratoconus, which was first described in detail in 1854, derives from the Greek words Kerato (cornea) and Konos (cone). Keratoconus is the most common primary ectasia. It is a bilateral and asymmetric corneal degeneration characterized by localized corneal thinning, leading to protrusion of the thinned cornea. Corneal thinning occurs typically in the inferior-temporal as well as the central cornea, although superior localizations have also been described[9].

The conservative management of keratoconus in the early stages consists of spectacle correction or rigid contact lenses. In more advanced phases with severe corneal irregular astigmatism and stromal opacities, surgical treatment with deep lamellar keratoplasty and PK should be considered[10]. Until the last decade of the century, keratoplasty procedures were the only alternative to treat this pathological condition. Nowadays, there are several therapeutic choices for the management of this condition, such as contact lens wearing, thermo keratoplasty procedures, corneal collagen cross-linking, ICRS implantation, and lamellar and PK[11].

ICRS are small devices made of synthetic material, which are implanted within the corneal stroma to induce a change in the geometry and the refractive power of the tissue[11]. ICRS was able to flatten the central cornea and regularize the tissue's asymmetry, thus leading to a reduction in the keratometric readings and an improvement in the refraction and vision of keratoconus patients[12]. This study aimed to evaluate the use of manual keratoscope intraoperative to improve the outcome of ICRS implantation in patients with keratoconus. To the best of our knowledge, we are considered from the novel researchers to evaluate the use of manual keratoscope intraoperatively in keratoconus patients during ICRS implantation. The current study revealed that there was statistically nonsignificant difference between the two groups regarding age and sex. Similar results were demonstrated by Hersh et al.[13], who evaluated ICRS used adjunctively and compared the safety and efficacy of concurrent vs. sequential surgery in 198 patients; they reported that the mean age of patients was 34±9 years, 80% of patients were males, whereas 20% were females. There was a statistically nonsignificant difference between the two groups regarding age and sex. Results of the current study revealed that nonsignificant differences were noted between the two studied groups and postoperative when compared with preoperative regarding refraction sphere, cylinder, and BSCVA.

Regarding BSCVA postoperative, Group B showed a higher BSCVA than Group A (3.611 vs. 3.601). Our results agreed with Jadidi et al.[14], who evaluated the implantation aided by pocket maker microkeratome for the correction of keratoconus; they reported that refraction sphere, refraction cylinder sphere, and BSCVA differed significantly postoperative when compared with preoperative.

In the present study regarding SE preoperative and postoperative, there was a statistically nonsignificant difference between groups, whereas within each group, there was a statistically significant difference. Both groups showed a decrease in SE. This was in accordance with Saelens et al.[15], who aimed to report refractive, topographic, and visual outcomes months after operated keratoconus with ICRS in eyes with progressive keratoconus and contact lens intolerance, the mean preoperative SE was − 4.16±2.41 D (range, 0.25 to 25.5 D) and after the treatment, mean SE measured − 0.68±1.49 D (range, 0.25 to − 3.0 D) showing a decrease of SE parameter.

Our study results showed that regarding preoperative K1, K2, K max, Max elevation (front), and Max elevation (back), there was a statistically nonsignificant difference between groups. Regarding K1 (postoperative) (P=0.004), K2 (postoperative) (P=0.006), K max (postoperative) (P=0.005), Max elevation (front) (postoperative) (P=0.001), there was a statistically significant difference between groups.

Regarding, K max (postoperative), Group B showed a lower K1 (42.40 vs. 44.70), K2 (45 vs. 48.50), and K max (50.2 vs. 55.10) than Group A, whereas regarding Max elevation (front) (postoperative), Group B showed a higher Max elevation (front) than Group A (28.10±9.88 vs. 18.53±6.17), whereas within each group, there was a statistically a significant difference postoperative. These results were in agree with Abdul Wahab et al.[16], who reported that the mean preoperative K1+SD was 48.50±4.67 D. The mean preoperative K2+SD was 52.51±5.65 D. The mean preoperative Km+SD was 50.48±5.18 D, which was decreased at the end of follow-up visits postoperatively to 45.86±5.49 D, 48.01±5.44 D, and 46.91±5.44 D, respectively. This also correlates with Mirazaei et al.[17], who reported preoperative clinically significant reduction in mean keratometry. Also, Km was improved and this correlates with the study done by Miraftab et al.[18]. The aim of ICRS implantation is not to treat or eliminate the existing disease, or should at least not be considered as a traditional refractive surgical procedure. However, ICRS is a surgical alternative to decrease astigmatisms and corneal abnormalities and, thus, increase the visual acuity to acceptable limits aiming to at least delay the need of corneal grafting[19].

Different approaches in ICRS implantation in keratoconus were based on either SE refraction or topographic values. In all of the studies in keratoconic eyes, statistically significant central flattening of the cornea was reported by El-Husseiny et al.[19]. Mean keratometric change after ICRS insertion was variable from 2.14 to 9.60 D. ICRS reduced the sphere, cylinder, and the SE in keratoconus. However, there were differences in the reported magnitude of the outcome. A regression in the spherical correction was observed in the medium and long-term[20].

There are conflicting results in terms of reduction of corneal higher-order aberrations, especially of the coma type. The favorable effect of ICRS is supported by the fact that most studies showed an improvement of BSCVA in 50% of cases[21]. Also, Carrasquillo et al.[22] found an 81% improvement in contact lens tolerance after Intacs implantation in keratoconus and post-LASIK ectasia. From the previous results, significant improvement of K readings, spherical errors, cylindrical errors as well as UCVA and BCVA was shown. The safety, efficacy, and predictability of the procedure were acceptable and in line with other studies. The current study revealed that regarding ACD (preoperative and postoperative), there was a statistically nonsignificant difference between groups, whereas within each group, there was a statistically a significant difference postoperative.

The results of the present study resemble to some extent the results of Rho et al.[23] study in which they aimed to compare changes in the anterior and the posterior corneal parameters and the ACD measured by a rotating Scheimpflug camera and scanning-slit topography before and after ICRS implantation; they reported that ACD decreased for all stages of the disease based on both rotating Scheimpflug camera and scanning-slit topography. Also, preoperative ACD in keratoconus stages from I to IV 3.09±0.23, 3.33±0.34, 3.31±0.23, and 3.32±0.27, respectively, which decreased to postoperatively to be 3.00±0.25, 3.21±0.37, 3.26±0.23, and 3.20±0.21, respectively. A significant postoperative decrease was noted compared with the preoperative value. The magnitude of the decrease was 120 μm in the rotating Scheimpflug camera and 90 μm in scanning-slit topography. This decrease in ACD reflects an overall flattening of the whole cornea[23].

Results of the current study showed that regarding thinnest location preoperative and postoperative, there was a statistically nonsignificant difference between groups. As well as within each group, there was a statistically nonsignificant difference. These results resemble to some extent the results of Larco et al.[24] study in which they aimed to evaluate the short-term safety and efficacy of ICRS implantation in keratoconus eyes of children. They reported that central corneal thickness showed nonsignificant difference postoperatively when compared with preoperation (445.77 μm and 451.42 μm, respectively, P=0.647).

Results of the current study showed regarding corneal volume (pre- and postoperative) that there was a statistically nonsignificant difference between groups. As well as within each group, there was a statistically nonsignificant difference. This is against results of Torquetti et al.[25] study in which they aimed to evaluate the clinical outcomes after implantation of a new 320°-arc length Ferrara ICRS (320-ICRS) in eyes of patients with keratoconus. They reported that corneal volume significantly increased postoperative (57.6±4.74) when compared with preoperative (56.2±4.28). Torquetti et al.[25] found a significant increase in corneal thickness after ICRS implantation. This difference can be explained by theoretical corneal collagen remodeling induced by implantation of the ICRS. Acting as spacers, the ring segments could interfere in corneal collagen turnover, with a consequent increase in central corneal pachymetry.

Also, with use of 320-ICRS, the manual technique or femtosecond laser–assisted procedure may differ from our procedure technique. From the previous results we can conclude that use of a manual keratoscope improved BSCVA with better maximum front elevation and ACD of cornea in keratoconus patients postoperative when compared with the blind implantation of ICRS. Further studies are needed and should include a larger number of keratoconus patients with different technique groups with an assessment of the role of use of manual keratoscope intraoperatively.


  Conclusion Top


The use of manual keratoscope improved BSCVA with better maximum front elevation and ACD of cornea in keratoconus patient's postoperative when compared with the blind implantation of ICRS.

Acknowledgements

Consent for publication: All authors had read, revised all paper sections, and agree to publishing.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]



 

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