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ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 2  |  Page : 646-652

Topographic corneal changes in children with vernal keratoconjunctivitis


1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Cairo, Egypt
2 Department of Ophthalmology, Kafr Al Zayat Central Hospital, Al Gharbia, Egypt

Date of Submission18-Dec-2019
Date of Decision19-Jan-2020
Date of Acceptance01-Feb-2020
Date of Web Publication27-Jun-2020

Correspondence Address:
Nagwan A Gad
Kafr Al Zayat Central Hospital, Al Gharbia
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_390_19

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  Abstract 


Objectives
To determine corneal topographic characteristics of children with vernal keratoconjunctivitis (VKC) and compare the corneal topographic indices between patients with VKC and normal participants.
Background
Keratoconus is the most common corneal ectatic disorder, the cause of which is largely unknown. Many factors have been implicated, and ocular allergy is one of them.
Patients and methods
A cross-sectional prospective study was conducted on children with VKC who attended outpatient clinic of Menoufia University Hospital, Faculty of Medicine, Menoufia University, in the period from February 2018 to February 2019. All study patients were divided in two groups: group I included 50 eyes of children with VKC aged between 7 and 18 years and group II included 30 eyes of normal age-matched and sex-matched participants. Full history, routine and physical examination, general topography, and Pentacam imaging were done.
Results
Children with VKC had significantly increased keratoconus index, index of surface variance, and index of vertical asymmetry than normal group. However, children with VKC had significantly decreased thinnest location (529.43 ± 34.72) than normal groups (569.30 ± 16.43) (P < 0.001). In addition, there were non statistical significant differences between the studied children regarding anterior chamber depth (P = 0.913) and corneal volume (P = 0.286). Moreover, max elevation front was significantly increased among children with VKC (9.03 ± 5.59) than normal groups (3.57 ± 1.28) (P < 0.001).
Conclusions
There was a higher prevalence of keratoconus-like topography in patients with VKC. However, owing to small sample size, being hospital-based study, lack of population-based randomized study, and lack of correlation between clinical findings and topographic findings, the data have limited role in extrapolation to the general population. So, patients with VKC should be advised to have corneal topography, especially when presentation of VKC is of long duration, a significant proportion of high refractive error is present, and Best Spectacle-Corrected Visual Acuity (BSCVA) is decreased.

Keywords: children, corneal topographic, keratoconus index, Pentacam imaging, vernal keratoconjunctivitis


How to cite this article:
Zaky AG, El-Sobky HM, Gad NA. Topographic corneal changes in children with vernal keratoconjunctivitis. Menoufia Med J 2020;33:646-52

How to cite this URL:
Zaky AG, El-Sobky HM, Gad NA. Topographic corneal changes in children with vernal keratoconjunctivitis. Menoufia Med J [serial online] 2020 [cited 2020 Jul 13];33:646-52. Available from: http://www.mmj.eg.net/text.asp?2020/33/2/646/287795




  Introduction Top


Vernal keratoconjunctivitis (VKC) is a recurrent ocular inflammatory disease that occurs seasonally. VKC is a disease showing great racial and geographical variation. It is most common and most severe in hot, arid environments such as the Mediterranean basin, West Africa, and the Indian subcontinent[1]. In these areas, up to 3% of eye clinic patients present with VKC and 10% of outpatient appointments are made for signs and symptoms related to VKC. Differences in prevalence could be owing to the diversity of gene pool, the environment (climate, socioeconomic status, and living styles), and gene–environment interaction[2].

The condition is more common in males, although this sex difference is less absolute in tropical climates. The sex discrepancy and the improvement seen during puberty have suggested a role for hormonal influence on disease burden. Climate and geography also correlate with the associated concurrence of asthma and eczema[3]. In temperate regions, 45–75% of patients with VKC have a history of atopy; in contrast, tropical regions have a much lower rate (5–40%). Limbal VKC is more often seen in patients of African or Asian descent, a racial susceptibility that appears even among those who have migrated to more temperate locales[3].

Patients from age 1 to 22 years old (mean, 6 ± 3.7 years) may present with signs and symptoms of VKC. Resolution is typically seen between the ages of 8 and 22 years. The disease usually lasts 4–10 years and resolves after puberty[4]. A family history of allergic diseases occurs in 35.5% of VKC cases, with positivity for other associated allergic states such as asthma, eczema, and/or rhinitis found in 37.1%. A positive skin prick test result has been identified in 51.4% of patients[5].

The first reported association between ocular allergy and VKC was described by Hilgartner in 1937. The association was controversial with few studies reporting an association ranging from 7 to 35%, whereas others did not show any relationship. However, more recent studies have proved that there is a definite association between allergy and VKC[6].

Keratoconus is the most common corneal ectatic disorder, the cause of which is largely unknown. Many factors have been implicated, with ocular allergy being one of them. The commonly proposed pathogenesis includes the release of inflammatory mediators owing to eye rubbing, which may alter the corneal collagen and lead to corneal ectasias[1]. The onset of keratoconus is often early in cases associated with allergy, and routine corneal topography may detect subtle forms of keratoconus[7]. These cases may require early keratoplasty and are at an increased risk of having acute corneal hydrops. Surgical outcomes are similar to primary keratoconus cases. However, postoperative epithelial breakdown may be a problem in these cases. Control of allergy and eye rubbing are the best measures to prevent corneal ectasias in cases of ocular allergy[8].

The aim of this study was to determine corneal topographic characteristics of children with VKC and compare the corneal topographic indices in patients with VKC with normal participants.


  Patients and Methods Top


A cross-sectional prospective study was conducted on children with VKC who attended outpatient clinic of Menoufia University Hospital, Faculty of Medicine, Menoufia University in the period from February 2018 to February 2019. All study patients were divided in two groups:

Group I: it included 50 eyes of children with VKC aged between 7 and 18 years.

Group II: it include 30 eyes of normal participants who were age and sex matched.

Ethical consideration

Approval of the study protocol by Ethical Scientific Committee of Menoufia University was obtained, and informed consent was taken from all children's parents before their enrollment in the study.

Inclusion criteria

Children having keratoconjunctivitis aged between 7 and 18 years and children having severe itching, photophobia, foreign body sensation, mucous discharge blepharospasm, and blurring of vision were included.

Exclusion criteria

Children with other ocular or systemic disease, high myopic children more than 6 D, children have ptosis or squint, and children with a history of previous ocular surgeries were excluded.

Clinically, VKC can be divided into three subtypes: conjunctival, limbal, and mixed presentations. Disease severity seems milder in limbal VKC, leading some to suspect that it is the early presentation of a spectrum of disease. However, there appears to be variability in the prevalence of certain types, based on geography and atopic history, which suggests that the pathogenesis of the two types may be different.

On external examination, the lids can be erythematous and thickened; a reactive ptosis may be present owing to photosensitivity. The classic finding of giant papillae (>1 mm diameter) is located most commonly on the upper tarsal conjunctiva. Lid eversion must be performed to visualize them. The tarsal conjunctiva develops a cobblestone appearance and, in active disease, can have mucus accumulation between the papillae.

In the limbal form, the conjunctiva may show a fine papillary reaction. Here the predominant findings are gelatinous limbal papillae associated with epithelial infiltrates called Horner–Trantas dots. These are focal collections of degenerated eosinophils and epithelial cells.

The cornea may become involved in VKC, and the corneal changes range from mild (punctate epithelial erosions) to severe (macroerosions and ulcers). Active palpebral disease may lead to development of superficial corneal neovascularization. Macroerosions form when inciting agents (e.g., eosinophilic major basic protein) released from the epithelium of the upper tarsal conjunctiva progress to corneal epithelial necrosis. Epithelial erosions may heal completely, with excellent visual outcomes; however, in severe or neglected cases, mucus and calcium deposition can prevent re-epithelialization, and a shield ulcer develops. Waxing and waning gray-white lipid deposits in the peripheral, superficial stroma create an arcuate infiltrate known as pseudogerontoxon.

Other conditions may coexist in children with VKC. Higher incidences of keratoconus (potentially due to eye rubbing) and abnormal corneal topography patterns have been reported. Complications of chronic steroid use, including steroid-induced cataracts, and glaucoma have been described in up to 20% of patients.

All cases were subjected to the following:

  1. History taking: patients were asked about age, medical history, surgical history, previous trauma, and last time they used contact lens if they are contact lens wearer. Uncorrected visual acuity, best-corrected visual acuity (BCVA), and retinoscopy were done
  2. Examination data: a thorough ophthalmic examination was done before Pentacam (Oculus, inc., Arlington city, Washington, USA), including uncorrected visual acuity and BCVA using Landolt chart and for statistical causes. Results are converted to Log MAR chart values. Slit lamp biomicroscopy was done to examine the cornea, and detect any abnormalities in the iris, lens, and anterior vitreous. Intraocular tension was assessed by Goldmann applanation tonometry.


  3. Fundus examination by slit lamp with + 90 D Volk lens: auxiliary lenses (+90 and + 78 D lenses) were used to examine central and peripheral retina to exclude possible pathology, for example, cystoid macular edema, retinal breaks, and macular scars.

  4. Investigation:


  5. Corneal topography: corneal topography was performed in most cases using Pentacam system to document advanced keratoconus. The mean curvature power of the cornea (Km) in the central 3 mm expressed in diopters was recorded.


General medical investigations: systemic evaluation was performed including blood sugar, complete blood count, liver function tests, kidney function tests, and ECG.

Pentacam imaging: written informed consents were acquired from all children's parents. In this study, we used Oculus Pentacam HR, where examination was performed in a dim illumination. The patient to be examined was positioned in front of the instrument, with the chin resting on the chin rest and the forehead resting against the forehead strap of the instrument. The eye to be examined was aligned with the black marks on the chin rest shaft, by adjusting the chin rest up or down, so the eye was in the center of the instrument. If the nose of the patient made an obstacle for proper alignment, the patient would be asked to turn his head slightly to get a clear image away from his nose. The patient was asked not to blink, open his eyes widely, fixate properly, and look into the fixation target of light in the instrument center. When the picture was properly aligned, the instrument would capture the image automatically, but if it was not, we should press the button on the keyboard to improve quality of picture. The rotating Scheimpflug camera captured 50 images automatically around the optical axis of the eye. Following parameters were recorded from the Pentacam maps: K1, K2, K max, central corneal thickness, ambrósio relational thickness (ART) max, index of surface variance (ISV), index of vertical asymmetry (IVA), keratoconus index (KI), anterior elevation, back elevation (according to Best Fit Sphere (BFS)), minimum progression, average progression, maximum progression, and net deviation.

Statistical analysis

Results were tabulated and statistically analyzed by using a personal computer using Microsoft Excel 2016 and SPSS v. 21 (SPSS Inc., Chicago, Illinois, USA). Statistical analysis was done using the following: descriptive, for example, percentage (%), mean and SD, and analytical, for example, Student t test, χ2, Fisher's exact test, and correlation coefficient test, as well as cutoff values by receiver operating characteristic (ROC) curve. A value of P value less than 0.05 was considered statistically significant.


  Results Top


Results showed that there were statistically significant differences between children with VKC and normal groups regarding age (P = 0.049) and sex (P < 0.001). Mean age of patients was 13.13 ± 2.92 and 14.67 ± 2.97 years for healthy children. Moreover, 53.33% of children with VKC were males and 46.77% were males, whereas all healthy children were females. On the contrary, there were no statistically significant differences between children with VKC and normal groups regarding side (P = 0.795) [Table 1].
Table 1: Comparison between children with vernal keratoconjunctivitis and normal groups regarding age, sex, and side

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The current study shows that children with VKC group had significantly increased of K1, K2, and K max than normal group. However, there was no comparison between children with VKC and normal groups regarding visual acuity and BCVA. Children with VKC group had significantly increased of KI, ISV, and IVA than normal group [Table 2].
Table 2: Comparison between patients with vernal keratoconjunctivitis and healthy groups regarding to visual acuity, best-corrected visual acuity, K1, K2, and K max

Click here to view


This study shows that children with VKC had significant decrease of thinnest location (529.43 ± 34.72) than normal groups (569.30 ± 16.43), with P value less than 0. 001. However, there were non statistical significant differences between children with VKC and normal groups regarding anterior chamber depth (P = 0.913) and corneal volume (P = 0.286). Moreover, max elevation front was significantly increased among children with VKC (9.03 ± 5.59) than normal groups (3.57 ± 1.28), with P value less than 0.001. However, max elevation back was not significantly different among children with VKC and normal groups (P = 0.104) [Table 3].
Table 3: Anterior chamber depth, thinnest location, and corneal volume among case and control groups

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In the present study, a significantly strong positive correlation was observed between K1, K2, and K max and astigmatism (refraction). Moreover, there was a strong positive correlation between K1, K2, and K max among children with VKC [Table 4].
Table 4: Correlation between astigmatism and K1, K2, and K max

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This study shows that there was a large area under the curve (AUC) for K1 (AUC = 0.772), with cutoff of 42.4, sensitivity of 56.7%, and specificity of 83.3%. However, the AUC was the greatest for the multimeric CCT (0.870), with cutoff of 518, sensitivity of 83%, specificity of 65.9%, followed by K2 (AUC = 0.867, cutoff 46.9, sensitivity 66.7%, and specificity 86.7%) and K max (AUC = 0.816, cutoff 43.1, sensitivity of 23.3%, and specificity of 76.7%), with highly significant differences (P < 0.001). Moreover, IVA, ISV, and KI cutoff values were 0.11, 25.5, and 0.563, with sensitivity of 83, 83, and 100 and specificity of 35.4, 47.6, and 15.9%, respectively [Figure 1].
Figure 1: ROC curve for CT, K1, K2, K max, ISV, IVA, and KI between the studied groups. ISV, index of surface variance; IVA, index of vertical asymmetry; KI, keratoconus index; ROC, receiver operating characteristic.

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  Discussion Top


In our study, children with VKC group had significantly increased K1, K2, and K max than normal group. However, there was no comparable difference between children with VKC and normal groups regarding visual acuity and BCVA. In the study done by Ekinci et al.[9], who compared the topographic corneal changes in patients with VKC with a control group, they found no statistically significant difference in K1, K2, and K average values, whereas the difference of K max values was found to be statistically significant (P < 0.05). When values of keratometry above 48 D are accepted as pathological, K2 and K max values' ratio of being above 48 D was found significantly high compared with the control group (P < 0.05). However, in the average sagittal curvature, no statistical difference was detected between groups (P > 0.05). However, when the values above 47 D are accepted as pathological, five eyes of 81 were accepted as pathological. On the contrary, in the study conducted by Barretto[10], sagittal curvature came out to be significantly higher compared with the control group (P < 0.05). These data showed that keratometry values might increase in the patients diagnosed with VKC. This increase might be the result of microtrauma in corneal structure, which occurs owing to intense itching. However, it was found that the mean curvature power of the cornea (Km) in the central 3 mm expressed in diopters is recorded preoperatively. Mean K was 57.9 ± 16.1 (range, 55.2–79). BCVA was 0.065 ± 0.178 in the patients group. On the contrary, it was 0.000 ± 0.000 in the control group. This shows that BCVA of the patients group was significantly higher than BCVA of the control group (P < 0.01).

Results of the current study show that children with VKC group had significantly increased KI, ISV, and IVA than normal group. Our results agree with Gautam et al.[11], who determined corneal topographic characteristics of children with VKC and compare the corneal topographic indices in patients with VKC with normal participants. They found that participants with VKC group had significantly increased keratoconus prediction index (9.5 ± 100.5), surface asymmetry index (0.5 ± 0.2), surface regularity index (0.5 ± 0.3), and differential sectoral index (3.7 ± 7.2) than normal group (0.2 ± 0.01, 0.4 ± 0.1, 0.3 ± 0.3, and 2.2 ± 0.5, respectively). However, Rabinowitz and Rasheed[12] reported the sensitivity of I–S ratio at 95.7% in the sample tested with keratoconus prediction index (KPI) index and keratoconus percentage index (KISA%) index.

In the current study, it was found that children with VKC had a significant decrease of thinnest location (529.43 ± 34.72) than normal groups (569.30 ± 16.43). However, there were statistically insignificant differences between children with VKC and normal groups regarding anterior chamber depth and corneal volume. In the study conducted by Nawaz et al.[13], who evaluated corneal topographic characteristics of patients with VKC and compared the corneal topographic indices in VKC participants with normal participants, they found that best spectacle corrected visual acuity and corrected intraocular pressure of VKC participants were not significantly different with normal participants. Central corneal thickness was found to be significantly decreased in patients with VKC (490.2 ± 8.7) compared with normal participants (510.4 ± 9.1). Central corneal thickness was even more significantly reduced in patients with VKC with suspected keratoconus-like topography (450.6 ± 12.2). These results agree with Gautam et al.[11], who determined corneal topographic characteristics of children with VKC and compare the corneal topographic indices in VKC patients with normal participants. They found that children with VKC had significantly decreased adjusted corneal thickness (507.2 ± 9.8 mm) than normal group (526.4 ± 8.6), with P value less than 0.001. On the contrary, Awad et al.[14] found that the keratometric reading (i.e., steep K, flat k, and mean K), difference between the central corneal thickness and thinnest location, difference between the posterior corneal elevation and back difference elevation, and D index measurement were significantly higher in eyes with keratoconus than in eyes of normal controls; the corneal thickness and Ambrósio relational thickness (ART average, ART min, and ART max) were significantly lower in eyes with keratoconus than in eyes of normal controls.

In the current study, there was a large AUC for K1. However, the AUC was the greatest for the multimeric CCT, followed by K2 and K max, with highly significant differences. Moreover, IVA, ISV, and KI had cutoff values of 0.11, 25.5, and 0.563, with sensitivity of 83, 83, and 100, and specificity of 35.4, 47.6, and 15.9%, respectively. Our results agree with Abdullah et al.[15], who evaluated the prevalence of keratoconus in patients with astigmatism more than 2 D using the data from the Pentacam Scheimpflug tomographer. They found that there was a large AUC for D, ART max, K max, K2, and PPI max. However, the AUC was the greatest for the multimeric D index (0.95). IVA has the largest area under the curve in keratoconus eyes compared with forme fruste eyes, followed by anterior elevation. IVA cutoff value was 0.29, with sensitivity and specificity of 75 and 88.9%, respectively. These results did not agree with Ucakhan et al.[16], who reported that posterior elevation had the largest area under the curve in keratoconus eyes. Ucakhan et al.[16] reported that posterior elevation cutoff was 6.26 μm, with sensitivity and specificity of 70 and 92% respectively. Moreover, in the study by Mihaltz et al.[17], ROC curve analysis indicated that posterior elevation was the most important criterion in the diagnosis of Keratoconus (KCN). This result does not correspond to our study. However, Awad et al.[14] found that the ROC analysis showed that the AUC values of the mean K, thinnest pachymetry, ART max, back difference elevation, D index, and PPI max were 0.82, 0.61, 0.88, 0.67, and 0.64, respectively. The contrast sensitivity and glare tests were significantly affected in the forme fruste cases.


  Conclusion Top


There was a higher prevalence of keratoconus-like topography in patients with VKC. However, owing to the small sample size, being hospital-based study, lack of population-based randomized study, and lack of correlation between clinical findings and topographic findings, the data have limited role in extrapolation to the general population. So, patients with VKC should be advised to have corneal topography, especially when presentation of VKC is of long duration, a significant proportion of high refractive error is present, and BSCVA is decreased.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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