Vernal keratoconjunctivitis (VKC) is characterized by bilateral severe chronic inflammation of the ocular surface. It is more prevalent in male population. It is usually seasonal with higher incidence found in hot weather and occasional flare-ups occurring during winters, which could lead to chronic and perennial disease. Various forms of VKC have variable global distribution with widely varying incidence, the palpebral form being more prevalent in Europe and the USA and the mixed and limbal forms being more common in Asia and Africa, respectively.
The hallmark characteristic of VKC is the presence of cobblestone-like papillae, mainly involving upper tarsal conjunctiva. Severe cases are associated with corneal changes like superficial punctate keratitis, corneal erosions, epithelial defect, plaque formation, and shield ulcers. In mild cases of VKC, clinical features may overlap with other ocular allergies like seasonal and perennial allergic conjunctivitis or giant papillary conjunctivitis, causing misdiagnosis of the disease, although the latter is often associated with contact lens wear or other foreign body response.
Among the established features of VKC, a new sign has been described in VKC as fine, golden brown pigmentation located in the perilimbal conjunctiva. This perilimbal pigmentation (PLP) is thought to be caused due to increase in melanocytic activity in response to inflammation of the surrounding connective tissue. Inflammation in VKC is due to both immediate and delayed hypersensitivity response, and limbus is actively involved in this immunology as it has melanocytes, mast cells, and Langerhans cells.[2,6]
This PLP may be a result of the ocular surface changes reflecting the effector limb of the immune response occurring after processing of the inciting antigen in the regional lymph nodes. As discussed, cells like mast cells and macrophages secrete proinflammatory cytokines (histamine, etc.), which causes melanogenesis seen as PLP.
Although this PLP has been established as a consistent finding in patients with VKC, our study makes an attempt to see its presence in Indian patients and correlate its extent with demographic factors, severity, and duration of VKC.
An observational, cross-sectional study was conducted at a tertiary eye care center in western Maharashtra from March 2019 to February 2020. It was approved by the institutional ethics committee (IEC/OCT/2018 dated October 23, 2018) and has been conducted in accordance with the Declaration of Helsinki. A written informed consent was taken from all the study subjects above 18 years of age (and from parents for subjects <18 years). The sample size was calculated to estimate 95% confidence interval for prevalence of PLP in cases of VKC with 5% absolute error of margin. The sample size worked out to be 152, assuming the prevalence to be 11% based on a previous study.
All clinically diagnosed cases of VKC were included in the study. Allergic conjunctivitis due to atopy, contact lens–induced conjunctivitis, and any previous trauma or ocular surgery were excluded. A detailed history was taken and slit-lamp examination was performed in all the cases. VKC was classified into palpebral (cobble stone-like papillae [discrete, >1 mm with flattened tops] involving upper tarsal conjunctiva only), limbal (gelatinous limbal thickening, Horner–Trantas dots, and limbal inflammation), and mixed forms based on the presence and location of characteristic signs. Corneal involvement with superficial punctate keratitis, corneal erosion, and recurrent epithelial defect or plaque formation (fibrin and mucus accumulation into macro-erosions) causing shield ulcer were noted. Family history included any known allergic eye diseases, asthma, allergic rhinitis, or eczema in the family. Personal history of non-ocular allergy included any known history of allergy disease in the body not involving the eye.
Severity of the disease was graded as mild (upper tarsal papillae), moderate (Horner–Trantas dots, focal limbal inflammation <6 clock hours, limbal thickening <6 clock hours, fine punctate corneal erosions), severe (active large cobblestone appearance, coarse corneal erosions, keratitis, severe limbal inflammation in >6 clock hours), and blinding (active large cobblestone, active shield ulcer, severe annular limbal inflammation, limbal stem cell deficiency).[7,8] Presence or absence of PLP was recorded in all the cases. In the eyes with PLP, its location and extent were recorded as the number of quadrants involved around the limbus (1 quadrant = 3 clock hours), and the type (discrete or dotlike) and color (brown to black) were recorded.
Data was analysed using Statistical Package for the Social Sciences (SPSS) 20.0 for Windows. Qualitative data variables were expressed as frequency and percentage, while quantitative data variables were expressed as mean, standard deviation (SD), and median. Various correlations and the relation of extent of PLP with severity and duration of the disease were analyzed using Wilcoxon–Mann–Whitney U test, Kruskal–Wallis test, Chi-squared test, Fisher’s exact test, and Spearman’s rho test. Mann–Whitney U test was selected for performing the statistical analysis as the data was nonparametric. The relationship between the duration of symptoms and severity of conjunctival pigmentation among patients was analyzed using Spearman`s rho test. A P value <0.05 was considered statistically significant.
Of 152 cases, 121 (79.61%) were males. The mean age at presentation was 11.4 ± 5.6 years (median, 11; range, 3.00–31.00). The maximum occurrence was in the age group of 11–15 years (32.9%).
Majority had reported in the months of May–June (59 cases, 38.82%). Also, 120 cases (79%) gave history of avoiding outdoor activities due to ocular symptoms. Seasonal exacerbations were found to be present in 112 cases (73.68%).
In this series, positive family and personal history of atopy or allergic conjunctivitis was present in 19 cases (12.49%). The commonest symptom found was itching (98.68%), followed by redness in 78 cases (51.32%).
Mixed pattern of VKC was found in 74 cases (48.68%; 95% confidence interval [CI]: 66.27, 80.77), which was followed by the palpebral form in 68 cases (44.74%; 95% CI: 36.68, 53.01) and the limbal form that had the least number of cases (6.58%; 95% CI: 3.20, 11.77).
The commonest sign found was upper tarsal papillae in 121 cases (79.61%). VKC-related complications like superficial punctate keratopathy were noted in three cases, and limbal stem cell deficiency was seen in two cases. The overall severity of the clinical course of VKC was found to be mild in the majority of cases.
PLP was observed in 81 cases, which was found to be in ‘significant’ number of cases (53.29%; 95% CI: 45.03, 61.42; P < 0.0001.The correlation of PLP with demographic factors, type, and severity of VKC has been described in Table 1, and further correlation with the type of PLP has been presented in Table 2.
The pigments were multiple, scattered, black in color and mainly dotlike in appearance (85.2%; 95% CI: 75.2%- 91.8%) as seen in Figure 1a and 1b and the rest were of discrete type as depicted in figure 1c and 1d. They were concentrated around the limbus and in the interpalpebral area of bulbar conjunctiva. There was a significant difference between the two groups in terms of age (W = 206.000, P = 0.006), with the median age being highest in the discrete group [Table 2].
Chi-squared test was used to explore the association of PLP with the quadrants involved and found to be insignificant [Table 3]. Tables 4 and 5 show the association among the quadrants involved, the extent in clock hours, and various parameters.
The extent of pigmentation was found to be significantly correlated with the type and severity of VKC (P < 0.001). There was a significant difference between the groups with respect to quadrants in terms of the extent of PLP in clock hours (Χ2 = 73.853, P < 0.001), with the median group involving all the quadrants. However, there was no significant correlation between the duration of disease and the extent of PLP. There was a significant difference between the groups with respect to the quadrants involved in terms of the extent of PLP in clock hours (Χ2 = 73.85, P < 0.001), However, the extent did not correlate with age (rho = 0.08, P = 0.487), sex (P = 0.115), time since onset in months (rho = 0.03, P = 0.77), duration of VKC, and type or color of PLP (P = 0.12). Table 6 shows Indian studies depicting characteristics of VKC from various parts of India.
VKC is a chronic, bilateral ocular inflammatory disorder affecting young males predominantly. This study showed that the odds of having VKC among males were 3.9 times higher than those of females, which is consistent with our findings.[7,10-12]
In our study, 40 patients (26.31%) had chronic perennial disease, which is in contrast to a recent Indian study which reported 60% cases with perennial disease and 35% cases with seasonal onset of disease. However, seasonal variations have been seen in multiple studies including ours. The predominant form found was mixed type. Palpebral forms are said to be more prevalent in Europe and the USA, whereas the mixed and limbal forms are more commonly seen in Asia and Africa, respectively, with some geographic variations and probably due to hospital attending bias. VKC has a varied spectrum of presentation from itching, ropy discharge, redness, and watering to severe forms of corneal ulcer leading to loss of vision, which is in conjunction with our study. This supports the dictum, “no itching, no vernal/spring catarrh” in VKC.
VKC has been considered as a type-I IgE-mediated immune disease, and this was supported by personal or family history of atopy and laboratory evidence of elevated IgE titers in patients’ serum and tears. However, Bonini et al., in a case series, found a positive response to skin and radioallergosorbent tests in 50% of the patients. This suggests that immunopathogenesis of VKC is multifactorial with cell-mediated involvement as well. Lately, PLP is a new clinical sign described in VKC.[6,9]
The role of type-I hypersensitivity reaction in VKC has been supported by various studies revealing elevated tear histamine levels and clinical response to mast cell stabilizers. Whereas immunohistochemical studies showed the presence of T-helper cells, which indicate the role of type-4 immune response as well. Thus, involvement of Th-2 lymphocytes, mast cells, eosinophils, other neural factors like substance-P and nerve growth factors may also play a role. The limbus is actively involved in the process of immunological reaction as it is rich in Langerhans cells (macrophages) which act as antigen-presenting cells in the eye, mast cells, and melanocytes.
Vitamin A deficiency may also show PLP, which can be differentiated from VKC by the presence of Bitot’s spots and the absence of other limbal and palpebral changes. In chemical injury, bulbar pigmentation and apart from the history of trauma and associated signs, this pigmentation tends to have a blotchy appearance and is deficient in fine granularity as seen in VKC.
Rao and Padmanabhan suggested that the presence of PLP in VKC may be a result of the ocular surface changes reflecting the immune response and was described as a consistent finding in VKC in the Indian population. It was followed by another study from Hong Kong in the Chinese population in which this pigmentation was reported in all the cases. Subsequently, multiple studies from various parts of India have reported this new emerging clinical sign, ranging in incidence from 8% to 11%.[5,7,14] These PLP pigments more commonly occur in the interpalpebral and inferior areas of the bulbar conjunctiva around the limbus, sparing tarsal conjunctiva.
Our study is unique as it reports a higher incidence (53.29%) of PLP in cases of VKC in the Indian population. This was noted as multiple, scattered, dot-like pigmentation with varying color, with the majority having blackish pigmentation. Diagnosis of VKC is usually clinical based on the signs and symptoms, but where the diagnosis becomes difficult, histopathologic analysis of conjunctival scraping may be helpful to demonstrate the presence of infiltrating eosinophils. Whether racial factors have a role in the distribution of the pigments remains to be solved.
Immunopathological studies of specimens of these conjunctival pigments from VKC patients may provide additional information. But it is an invasive procedure and sometimes difficult to perform in uncooperative children. Our study has demonstrated PLP in a large number of patients, therefore making it a reliable clinical sign in patients with VKC. Furthermore, it may be of greater clinical importance in diagnosing mild cases of VKC when palpebral and limbal signs are not very distinctive.
The overall severity of the clinical course of the disease found in our study was mild. However, it was found in all the grades of VKC. The extent of pigmentation was found to be significantly correlated with the severity of VKC. However, there was no statistically significant correlation seen between duration of the disease and the extent of perilimbal conjunctival pigmentation. Similarly, no relation was found between age and severity of inflammation, and PLP was present even when the disease went into remission.
This study has many strengths. It is a prospective study with a large sample size. To the best of our knowledge, this is the first study to report PLP in detail and correlate PLP and its types with the demographic factors and severity and duration of VKC.
PLP seems to be a consistent clinical finding seen in a large number of patients with VKC. It may benefit ophthalmologists in managing VKC cases much earlier when palpebral/limbal signs are not distinct. This may help in preventing sight-threatening complications and providing good quality of life to the young population.
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Conflicts of interest
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