Corneal densitometry in patients with keratoconus undergoing intrastromal Ferrara ring implantation

Rodrigues, Pablo Felipe; Moscovici, Bernardo Kaplan; Ferrara, Guilherme; Lamazales, Luciano; Freitas, Marcela Mara Silva; Torquetti, Leonardo; Ambrósio, Renato; Gomes, José Álvaro Pereira

doi:10.1177/11206721211020631

Cited by 8 publications

(11 citation statements)

References 22 publications

(39 reference statements)

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“…The increased of CD values at 4 years after ICL surgery correlated with age, preoperative spherical equivalent, uncorrected distance visual acuity, and intraocular pressure (IOP), may be related to the changes in metabolism and collagen fiber arrangement of the corneal endothelial cells due to age (23). CD in the anterior layer of the cornea is reduced after intrastromal corneal ring segments 10.3389/fmed.2023.1184318 implantation in patients with keratoconus and is correlated with corneal keratometry (22).…”

Section: Discussionmentioning

confidence: 99%

“…Many ocular surface diseases, such as keratoconus, vernal keratitis, dry eye, and primary congenital glaucoma have an impact on CD (17)(18)(19)(20). Anterior segment surgeries including small incision lenticule extraction (SMILE), femtosecond Laser-assisted In Situ Keratomileusis (FS-LASIK), implantable collamer lens (ICL) V4c implantation, and intrastromal Ferrara ring implantation also affect CD (21)(22)(23).…”

Section: Introductionmentioning

confidence: 99%

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The influence of pterygium on corneal densitometry evaluated using the Oculus Pentacam system

Zhang

et al. 2023

Front. Med.

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PurposeTo assess the effect of pterygium on corneal densitometry (CD) values.MethodsOne hundred and nine patients (155 eyes) with primary pterygium were divided into a severe pterygium group (79 eyes) and a mild-to-moderate pterygium group (76 eyes) according to pterygium severity. Among them, 63 patients had monocular pterygium; and 25 patients (38 eyes) underwent pterygium excision combined with conjunctival autograft follow-up. A Pentacam anterior segment analyzer was used to obtain the CD values and corneal morphological parameters, including central corneal thickness (CCT), flat-axis keratometry (K1), steep-axis keratometry (K2), corneal astigmatism, irregular astigmatism, and spherical aberration. CD was subdivided into four concentric radial regions based on corneal diameter and three layers according to depth.ResultsCD values at 0–12 mm of the anterior 120 μm layer, 0–10 mm of the center layer and full thickness, and 2–6 mm of the posterior 60 μm layer were significantly higher in eyes affected by pterygium than in the contralateral unaffected eyes (all P < 0.05). CD values were significantly higher in the severe pterygium group than in the mild to moderate pterygium group (all P < 0.05). Corneal astigmatism, irregular astigmatism, K1, K2, CCT, and spherical aberration correlated with CD values in eyes with pterygium (all P < 0.05). CD values at 6–10, 0–12 mm in the anterior 120 μm layer and full thickness, 10–12 and 0–12 mm in the center layer were significantly decreased 1 month after pterygium surgery compared with those before surgery (all P < 0.05).ConclusionPatients with pterygium had increased CD values, particularly in the anterior and central layers. CD values were correlated with pterygium severity grading and corneal parameters. Pterygium surgery partially reduced the CD values.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The influence of pterygium on corneal densitometry evaluated using the Oculus Pentacam system

Zhang

et al. 2023

Front. Med.

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“…The mean maximum K was 54.01D (SD ± 3.38) preoperatively and 51.50D (SD ± 2.90) postoperatively. The mean anterior densitometric value was 18.26 (SD ± 2.03) preoperatively and 17.66 (SD ± 1.84) postoperatively [16].…”

Section: Major Findingsmentioning

confidence: 94%

Ferrara ring and the nomogram as the main strategy for correcting keratoconus: a systematic review of clinical findings

Moura¹,

Daher²,

Ferrari³

et al. 2023

MedNEXT

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Introduction: In the setting of corneal ectasias, keratoconus (KC) is a bilateral and asymmetrical disease that results in progressive thinning and tilting of the cornea, leading to irregular astigmatism and decreased visual acuity. The condition affects all ethnicities and both sexes. KC prevalence and incidence rates are close to between 0.2 and 4790 per 100,000 people and 1.5 and 25 cases per 100,000 person-years, respectively. For surgeons who implant Ferrara rings, the manufacturer has developed an online nomogram aimed at optimizing patient outcomes. Objective: The present study carried out a systematic review to present the main clinical outcomes of keratoconus treatment using the Ferrara ring. Methods: The systematic review rules of the PRISMA Platform were followed. The literature search was carried out from January to February 2023 in Scopus, PubMed, Science Direct, Scielo, and Google Scholar databases. Scientific articles from the last 15 years were selected. The quality of the studies was based on the GRADE instrument. The risk of bias was analyzed according to the Cochrane instrument. Results and Conclusion: A total of 60 articles were found, of which only 21 were part of this systematic review, after an eligibility analysis.It was concluded that the insertion of Ferrara rings in keratoconic eyes with previous cross-linking history using the company's nomogram results in significant improvements in visual, refractive, and tomographic results. Corneal densitometry in the anterior layer of the cornea decreases after the implantation of intrastromal corneal ring segments and correlates with corneal keratometry. Over 5 years, Ferrara-type intrastromal corneal ring segment implantation is a safe, effective, and stable procedure for restoring vision in pediatric patients with keratoconus old.

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“…Corneal densitometry is increasingly being used as a clinical tool to monitor and assist in the diagnosis of ocular conditions such as high myopia [9,10], corneal dystrophy [11], monoclonal gammopathy [12], corneal biomechanics [13,14], and KC [2,[15][16][17]. In addition, densitometry is frequently used to assess corneal transparency at different stages of KC [15,18]; therefore, it is useful to understand the effects of any artefacts inherent in the measurement system.…”

Section: Introductionmentioning

confidence: 99%

Investigation of How Corneal Densitometry Artefacts Affect the Imaging of Normal and Keratoconic Corneas

Alanazi,

Esporcatte,

White

et al. 2024

Bioengineering

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Purpose: To investigate corneal densitometry artefacts found in Pentacam Scheimpflug scans and their potential effect on assessing keratoconic (KC) corneas compared to normal (N) corneas. Methods: The current study utilises Pentacam data of 458 N eyes, aged 35.6 ± 15.8 (range 10–87), referred to as the “N group”, and 314 KC eyes, aged 31.6 ± 10.8 (range 10–72), referred to as the “KC group”, where densitometry data were extracted and analysed via a custom-built MATLAB code. Radial summations of the densitometry were calculated at diameters ranging from 0.5 mm to 5.0 mm. The minimum normalised radial summation of densitometry (NRSD) value and angle were determined at each diameter and then linked. KC cone locations and areas of pathology were determined, and a comparison between N and KC groups was carried out both within the averaged area of pathology and over the corneal surface. Results: Joining minimum NRSD trajectory points marked a clear distortion line pointing to the nasal-superior direction at 65° from the nasal meridian. The findings were found to be independent of eye laterality or ocular condition. Consistency was detected in the right and left eyes among both the N and KC groups. The location of the KC cone centre and the area of pathology were determined, and the densitometry output was compared both within the area of pathology and over the whole cornea. When the average densitometry was compared between N and KC eyes within the KC area of pathology, the N group recorded a 16.37 ± 3.15 normalised grey-scale unit (NGSU), and the KC group recorded 17.74 ± 3.4 NGSU (p = 0.0001). However, when the whole cornea was considered, the N group recorded 16.71 ± 5.5 NGSU, and the KC group recorded 15.72 ± 3.98 NGSU (p = 0.0467). A weak correlation was found between the Bad D index and NGSU when the whole measured cornea was considered (R = −0.01); however, a better correlation was recorded within the KC area of pathology (R = 0.21). Conclusions: Nasal-superior artefacts are observed in the densitometry Pentacam maps, and analysis shows no significant differences in their appearance between N or KC corneas. When analysing KC corneas, it was found that the cone positions are mostly on the temporal-inferior side of the cornea, opposite to the densitometry artefact NRSD trajectory. The analysis suggests that the corneal densitometry artefacts do not interfere with the KC area of pathology as it reaches its extreme in the opposite direction; therefore, weighting the densitometry map to increase the contribution of the inferior-temporal cornea and decreasing that of the superior-nasal area would improve the classification or identification of KC if densitometry is to be used as a KC metric.

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Corneal densitometry in patients with keratoconus undergoing intrastromal Ferrara ring implantation

Cited by 8 publications

References 22 publications

The influence of pterygium on corneal densitometry evaluated using the Oculus Pentacam system

The influence of pterygium on corneal densitometry evaluated using the Oculus Pentacam system

Ferrara ring and the nomogram as the main strategy for correcting keratoconus: a systematic review of clinical findings

Investigation of How Corneal Densitometry Artefacts Affect the Imaging of Normal and Keratoconic Corneas

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