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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 60  |  Issue : 1  |  Page : 15-18

Characteristics of pediatric keratoconus and the role of corneal topography in early diagnosis: A prospective study


1 Rajan Eye Care Hospital Pvt Ltd., Chennai, Tamil Nadu, India
2 Sankara Nethralaya, Kolkata, West Bengal, India
3 Narayana Nethralaya, Bengaluru, Karnataka, India

Date of Submission14-Jan-2021
Date of Decision04-Mar-2021
Date of Acceptance13-Jan-2022
Date of Web Publication22-Mar-2022

Correspondence Address:
Dr. Sujatha Mohan
Rajan Eye Care Hospital Pvt Ltd., No. 5 Vidyodaya, 2nd Cross Street, T. Nagar, Chennai, Tamil Nadu
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_3_21

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  Abstract 


Purpose: The purpose of this study is to describe the clinical and topographical features of keratoconus in children and to emphasize the role of corneal topography in early diagnosis of keratoconus in eyes with astigmatism. Materials and Methods: It was a prospective study done to screen children below 18 years with astigmatism of 1.50 Diopter or greater for presence of keratoconus. Ophthalmic evaluation included retinoscopy, cycloplegic refraction, and detailed slit lamp examination for clinical diagnosis of keratoconus. All eyes underwent corneal topography and tomography. Eyes were followed up for progression with both refraction and corneal topographic imaging. Progressive cases later underwent Accelerated Collagen Crosslinking (ACXL). Results: 700 eyes of 350 patients with astigmatism were screened for keratoconus. 44 eyes of 28 patients were diagnosed with keratoconus. Mean age of the diagnosed children was 11.7 years (6–18 years), 18 boys and 10 girls. Overall, most common clinical association was allergic conjunctivitis. Twenty-five eyes (57%) had clinical evidence of keratoconus while other 19 eyes (43%) required corneal topography to establish the diagnosis. Based on the Amsler-Muckenheim tomographical classification, 22 of 44 eyes (50%) were grouped in prestage level followed by 13 eyes (29.5%) in Stage 1, 5 eyes (11.4%) in Stage 2, and 4 eyes (9.1%) in Stage 3. Thirty-five eyes of 21 patients showed progression and underwent ACXL. Conclusion: Early detection of keratoconus in children with astigmatism is of utmost importance to avoid visual impairment and surgical intervention. Even in the absence of clinical signs, corneal topography and tomography should be performed as a screening tool to rule out keratoconus in these children.

Keywords: Astigmatism, corneal topography, keratoconus, pediatric


How to cite this article:
Mohan S, Banerjee M, Annavajjhala S. Characteristics of pediatric keratoconus and the role of corneal topography in early diagnosis: A prospective study. TNOA J Ophthalmic Sci Res 2022;60:15-8

How to cite this URL:
Mohan S, Banerjee M, Annavajjhala S. Characteristics of pediatric keratoconus and the role of corneal topography in early diagnosis: A prospective study. TNOA J Ophthalmic Sci Res [serial online] 2022 [cited 2022 May 29];60:15-8. Available from: https://www.tnoajosr.com/text.asp?2022/60/1/15/340362




  Introduction Top


Keratoconus is a progressive ectatic corneal condition leading to irregular astigmatism and visual impairment, secondary to noninflammatory changes in the corneal stromal collagen.[1] The disease typically manifests during puberty and progresses till another 2 decades and has clear association with ocular allergy and eye rubbing.[2],[3] Contrary to the previous belief of it being an adolescent disease, several studies have shown that keratoconus manifests in children even before puberty.[4],[5],[6] To date, the reported youngest age of presentation is 4 years.[7] The incidence of keratoconus in general population varies from 50 to 230 per 100,000 (approximately 1 per 2000).[6] The prevalence in central India was estimated to be 2300 per 100,000 (0.0003%–2.3%).[8] Pediatric keratoconus poses several challenges to the clinician with respect to its under diagnosis, asymmetric presentation and amblyopia, rapid progression, and modifications in the treatment options.[4] Treatment depends on the severity of the condition and can range from glasses or contact lenses, to collagen cross linking and penetrating or lamellar keratoplasties. Most of the literature emphasized the epidemiological characteristics and treatment options of pediatric keratoconus in Indian population but did not highlight the importance of routine topographical screening in eyes with significant astigmatism for its earlier detection.[6],[7],[9] This present study emphasizes the use of corneal topography and tomography as an important diagnostic tool in detecting keratoconus in children with significant astigmatism as well as eyes lacking clinically detectable signs.


  Materials and Methods Top


It was a prospective, nonrandomized study in a tertiary eye care center. The study was approved by the Institutional Review Board and the Ethics Committee. All patients <18 years of age with astigmatism were screened for the presence of either clinical or topographical evidence of any stage of keratoconus and associated ocular or systemic risk factors over a period of 1 year (December 2016–December 2017). Astigmatism ≥1.50 D was taken as the cut off for this study. A thorough ophthalmic evaluation including uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA) using Snellen's chart, cycloplegic refraction, and dilated fundus evaluation was performed in all cases. Clinical diagnosis was established based on detailed slit lamp examination with or without the presence of scissoring reflex in retinoscopy. Corneal topography was done using TOMEY - Topographic Modelling System (TMS-4) (TOMEY corporation, Noritakshinmachi, Nagoya, Japan) and Klyce Smolek multivariate index in TMS-4 system was used to reach a diagnosis of keratoconus in cases with high astigmatism and lacking clinical evidence of keratoconus. All cases also underwent pachymetry analysis and tomographical analysis using PentacamWave light Oculyzer II. Suspected cases were then confirmed using Belin Ambrosio display map in pentacam followed by classification into stages according to Amsler-Muckenheim classification.

Following ocular examination, all children were visually rehabilitated with spectacles by choice. The eyes diagnosed with keratoconus were followed up for progression and any associated co-morbid conditions every 3 months. We defined progression as any documented increase of 0.5Dioptre of astigmatism in refraction in the next 3 months with a corresponding change in the surface asymmetry index/symmetry index (SAI/SI index >0.5) in corneal topography documented by a single senior optometrist.[10] The progressive cases were planned for accelerated collagen cross linking (ACXL) provided their corneal thickness at the thinnest point was more than 400 microns. Cases with severe dry eye, any active or healed infective or inflammatory pathology, were excluded. Data were entered in a Microsoft excel sheet and were analyzed using the Statistical Package for the Social Sciences software (SPSS Inc., Chicago, IL, version 21.0 for Windows Evaluation Version). All quantitative variables were estimated using measures of central location (mean, median) and measures of dispersion (standard deviation). Visual acuity was converted to logMAR values for statistical analysis.


  Results Top


A total of 700 eyes of 350 children with significant astigmatism were screened for clinical and/or topographical evidence of keratoconus. Forty-four eyes of 28 patients (18 boys and 10 girls) were diagnosed with keratoconus either clinically and/or topographically. Mean age of the diagnosed children was 11.7 ± 4.3 years (6–18 years). Sixteen of 28 patients had bilateral involvement while 12 had unilateral disease. Overall most common clinical association was eye rubbing due to allergic conjunctivitis in more than half of the patients (15/28). Family history of keratoconus and history of asthma was found in 4 patients each. Out of 44 eyes, 25 eyes (57%) had clinical signs of keratoconus while 19 eyes (43%) presented without any clinical evidence and needed topography to establish the diagnosis. The distribution of the clinical signs is shown in [Figure 1]. Hydrops-related corneal complication was found in only one patient aged 12 years at the time of presentation. According to classification given by Buxton et al., the keratoconus severity in our patients was graded into mild, moderate, advanced, and severe disease with distribution of eyes with or without clinical signs as shown in [Table 1].[11] Sixty percent each of mild and advanced group eyes and 35% of moderately affected eyes did not show any clinical evidence of keratoconus.
Figure 1: Distribution of overall clinical findings in eyes with keratoconus

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Table 1: Severity grading of keratoconus according to Mean K and the distribution of eyes with or without clinical signs in each grade

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Scissoring reflex in retinoscopy was found in 36 eyes while 8 eyes had clear reflex. UCVA, BCVA, mean astigmatism, and the topographical parameters are shown in [Table 2]. Mean pachymetry was 509.17 microns. 26 (59%) eyes had pachymetry more than 500 microns, 14 (31%) eyes had between 450 and 500 μ, and 4 eyes (9%) had <450 μ. One of the eyes with pachymetry of 455 μ had hydrops-related corneal opacity. He was found to have −6.0 D of astigmatism, with mean K reading of 68.9 D. His BCVA improved from 1 to 0.3 log MAR with spectacles.
Table 2: Various visual and topographical parameters of the eyes diagnosed with keratoconus

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Based on the Amsler-Muckenheim classification, 22 of 44 eyes (50%) were grouped in prestage level followed by 13 eyes (29.5%) in Stage 1, 5 eyes (11.4%) in Stage 2, and 4 eyes (9.1%) in Stage 3. Tomographical diagnosis was established before the onset of clinical signs of keratoconus in these eyes. The topographical patterns found in our study are shown in [Table 3]. Two eyes (4.5%) did not show any topographical changes but showed tomographical changes on pentacam.
Table 3: Different topographical patterns in the eyes diagnosed with keratoconus

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Pentacam analysis of Belin Ambrosio Enhanced Ectatic display map showed abnormal deviation of front elevation difference map (Df) in 11eyes (25%), abnormal deviation of back elevation difference map (Db) in 6 eyes (13.7%), and abnormality in both parameters (Df and Db) in 27 eyes (61.3%).


  Discussion Top


Keratoconus, in its milder form, can cause visual impairment due to induced irregular astigmatism, often leading to refractive amblyopia in children. In severe form, it can lead to hydrops-related corneal opacities, posing risk of amblyopia and need for surgical procedures. Thus, visual impairment in childhood, in any form, can affect educational and social life and can negatively impact the quality of life of children. In India, the incidence of keratoconus is 4.4 times higher than the Caucasians and presents at a much younger age as compared to the western population.[12],[13] It has been reported that geographical locations with plenty of sunshine can induce oxidative stress in the cornea leading to keratoconus.[14] Keratoconus in children is unique in certain characteristics. The disease tends to be more aggressive due to the dynamic environment of the cornea and ongoing collagen remodeling, with a higher rate of progression compared to adults.[1],[6],[15] Léoni-Mesplié et al. in their retrospective study reported that keratoconus in children was more severe at diagnosis (27.8% in Stage 4) as compared to adults (7.8% at Stage 4).[5] In our study, mean age at presentation was 11.7 years, the youngest being 6 years of age. Furthermore, Tuft et al. have shown that young age itself is an independent risk factor for keratoconus progression.[16] In his study, patients younger than 18 years at presentation progressed faster to transplantation than those older than 18 years of age. Thirty-five eyes of 21 patients in our study showed progression according to criteria mentioned by Caporossi et al. and required collagen cross linking to stabilize the cornea.[10]

Pediatric keratoconus is usually bilateral though often it can be asymmetrical at presentation. Sixteen patients (57%) in this study were found to have bilateral keratoconus and 12 patients (43%) had unilateral involvement at presentation which is consistent with other reports.[15],[17] Hence, the unilateral cases need to be followed up more closely for early detection documenting the onset of keratoconus in other eye.

As per previous literature, keratoconus is mostly an isolated disease, but often it can be associated with positive family history, connective tissue disorders, eye rubbing and ocular conditions such as atopy, vernal keratoconjunctivitis, and retinal dystrophies.[1],[6],[17] In our study, we screened 700 eyes diagnosed with significant astigmatism for any clinical or topographical evidence of keratoconus. The most common ocular association found in our study was eye rubbing due to allergic conjunctivitis seen in 15 patients (53.5%). Eye rubbing either habitual or due to ocular allergy releases metalloproteinases and interleukins leading to development as well as progression of keratoconus.[3] Frequently, allergic disorders can be the single reason for eye examination.[3] Furthermore, coexisting ocular allergies can lead to rapid progression of keratoconus as compared to normal eyes.[2],[3] Even after successful treatment of keratoconus, progression has been documented due to constant rubbing of eyes in such cases.[3] Hence, treatment of co-morbidities is equally important for long-term stabilization of cornea. Family history of keratoconus was present in 4 patients (14%) of our study which is consistent with various other studies where a positive family history has been noted in 6%–10% of cases.[1],[6] Thus, screening of the parents as well as siblings with the help of clinical and topographical assessment should also be considered as a part of the keratoconus diagnosis.

Identification of pediatric keratoconus is a diagnostic challenge as often children with keratoconus present without clinically detectable signs resulting in under diagnosis.[4] In this present study, 56% of eyes only had clinical evidence of keratoconus while 43% showed only topographical evidence of keratoconus without any clinically detectable signs. Mild, moderate, advanced, and severe keratoconus (according to Mean K) was found in 10, 28, 5, and 1 eyes, respectively. Clinically detectable signs were much less (40%) in mild disease, whereas in moderate disease, it increased to 64.2%. Hence, most of the eyes with mild disease were diagnosed on the basis of topography and pentacam. Moreover, most of these eyes diagnosed only by tomography were already found to have some stage of keratoconus, such as, prestage (22 eyes) or Stage 1 (15 eyes) according to the Amsler-Muckenheim classification. This re-emphasizes on corneal topography and tomography being the best available screening tool in the present day for early detection of keratoconus, especially in milder stage of the disease. Among the topographical patterns documented in previous literature, our study showed asymmetric bow tie pattern with inferior steepening as the most common presentation.[6]

Progressive keratoconus cases require treatment in some form, ranging from CXL to keratoplasty. In the literature for pediatric keratoconus, studies vary in their definition of progression. Some studies define progression as occurring within 3 months,[10],[18],[19] 6 months,[20] 12 months[21] with multiple parameters for consideration without emphasizing on a specific single parameter or index to note for progression. On the other hand, authors have also suggested that it is inappropriate to wait for signs of progression for planning treatment, in view of the rapidity with which keratoconus evolves in children. Soeters et al. reported range of keratoconus progression in children, 2.6 D in a week to 5.0 D in a year.[18] Hence, unlike adults, treatment in pediatric keratoconus should be offered at diagnosis.[22] In our study, we followed the progression criteria almost similar to Caporossi et al. where eyes showing a change in 0.5 D in cylindrical component along with SAI/SI index change in topography were considered as progressive cases.[10] Out of 44 eyes, 35 (79.5%) eyes had documented progression and underwent ACXL in our study.


  Conclusion Top


This is a prospective study which gives a holistic view of diagnosis and characteristics of keratoconus in children. Even in the absence of clinical signs, corneal topography and tomography should be performed as a screening tool to rule out keratoconus in children with astigmatism, with or without allergic conjunctivitis. Early diagnosis either clinical or topographical, documentation of progression, appropriate intervention and rehabilitation form integral parts in the management of pediatric keratoconus.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Léoni-Mesplié S, Mortemousque B, Mesplié N, Touboul D, Praud D, Malet F, et al. Epidemiological aspects of keratoconus in children. J Fr Ophtalmol 2012;35:776-85.  Back to cited text no. 5
    
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Amsler M. Some data on the problem of keratoconus. Bull Soc Belge Ophtalmol 1961;129:331-54.  Back to cited text no. 15
    
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