1 Introduction
Filamentary keratitis (FK) is a chronic and recurrent disorder of the cornea and, rarely, the conjunctiva. Patients with FK generally experience a foreign body sensation, chronic pain, tearing, mucoid discharge, photophobia, and blepharospasm.[1] [2] keratitis , keratoconjunctivitis, brain stem injury, postcataract surgery, penetrating keratoplasty (PKP), recurrent erosion, prolonged eye patch use, ptosis, and large-angle strabismus.[3]
2 Materials and methods
2.1 Objects
According to slit-lamp microscope examinations, anterior segment photographs, and computer-based patient records, a retrospective study was conducted on patients with FK. These findings were evaluated in terms of sex, age, causative factor, treatment history, and the location and number of filaments. The patients had been continuously and completely recorded from August 2012 to August 2015 at the Ophthalmology Clinic of the Second Affiliated Hospital of Zhejiang University, which was a general research hospital in Hangzhou, east of China. The inclusion criteria were those eyes with excessive abnormal mucous debris and tenacious mucus strands or plaques, which were often several millimeters long and attached to the cornea. Observation indices included the quantity of the filaments and their distribution. The positions of the filaments on the corneal surface were divided into the interpalpebral zone, corneal limbus, corneal damage or suture site, and total cornea.
2.2 Methods
Each patient was examined with a slit-lamp microscope and photographed with an anterior segment camera. Corneal fluorescein staining and tear film breakup time (TFBUT) were also performed on each patient.
The patients were divided into 3 age groups: 0 to 25 years (group A), 26 to 50 years (group B), and 51 to 81 years (group C). The patients were also assigned into 3 different groups according to the cause of the FK (dry eye and exposure keratitis group, autoimmune diseases and ocular inflammation group, and surgery and chemical injury of the eyes group). These latter groups were assigned in order to investigate the different locations of filaments distributed on the corneal surface.
2.3 Management
After a topical anesthetic was applied in the lower conjunctiva fornix of the eye, the filaments were removed using cotton swabs moistened with saline. The patients were also prescribed preservative-free artificial tears. In addition, we gave different treatments for various causative factors: patients with exposure keratitis were given tarsorrhaphy; patients with allergic conjunctivitis were prescribed topical antiallergic agents; those with dry eyes were given topical nonsteroidal anti-inflammatory or topical low concentrations of steroids; patients with viral keratitis were given topical antiviral drugs; those who had ocular surgical procedures, chemical injury, or autoimmune disease were prescribed topical high concentrations of steroids and oral steroids; and patients with refractory or severe stimulating symptoms after surgery were given a bandage contact lens combined with topical and oral steroids. Dosage adjustments may have been needed based on the severity of the disease.
2.4 Statistical analysis
Data were presented as the mean and standard deviation or frequencies. The categorical data were analyzed by chi-square tests. P values of <0.05 were considered statistically significant.
3 Results
Patient details are summarized in Table 1 . A total of 147 patients (162 eyes) were included in this study, ranging in age from 6 to 81 years old (mean: 43.54 ± 18.58 years). All patients had symptoms of foreign bodies in the eyes. There were 28 eyes in group A, 74 eyes in group B, and 60 eyes in group C. FK was found to be involved in both eyes in 15 patients. Among these 15 patients, 11 cases were caused by autoimmune factors, 2 by allergic conjunctivitis, 1 by dry eye, and 1 case was caused by ocular surgery. The causative factors inducing FK included allergic conjunctivitis, nonautoimmune forms of dry eye, viral keratitis , exposure keratitis , ocular surgeries, chemical injury, and autoimmune diseases.
Table 1: Causative factors of filamentary keratitis among different age groups (eyes n [%]).
In group A, 15 eyes (53.57%) with FK were caused by allergic conjunctivitis. In groups B and C, FK caused by dry eye were found in 33 cases (44.59%) and 24 cases (40.00%), respectively. The detailed causative factors of FK included 16 eyes with allergic conjunctivitis, 62 with dry eye, 28 with viral keratitis , 3 with exposure keratitis , and 19 with ocular surgical procedures or chemical injuries. Other causative factors included 34 eyes with autoimmune diseases including graft-versus-host disease (GVHD) (9 eyes), Sjogren syndrome (SS) (19 eyes), rheumatoid arthritis (RA) (4 eyes), and systemic lupus erythematous (SLE) (2 eyes).
FK induced by allergic conjunctivitis in group A was significantly higher than the other 2 groups (15/28 vs 1/74, 15/28 vs 0/60) (P < 0.001, P < 0.001). However, FK cases caused by dry eye and autoimmune disease among group A patients were much lower than the other 2 groups (5/28 vs 33/74, 5/28 vs 24/60 and 1/28 vs 19/74, 1/28 vs 14/60) (P = 0.013, P = 0.040 and P = 0.012, P = 0.046). FK caused by surgery and chemical injury in group C was significantly higher than the other 2 groups (14/60 vs 1/28, 14/60 vs 4/74) (P = 0.046, P = 0.002). The findings of FK due to viral keratitis were not significantly different among the 3 groups (P > 0.05).
The filament locations are summarized in Table 2 . The filaments of 52 eyes (80.00%) were restricted to the exposed interpalpebral zone (Fig. 1 ) in the dry eye and exposure keratitis group. The filaments of 41 eyes (52.56%) were distributed in the corneal limbus (Fig. 2 ) in the autoimmune factors and ocular inflammation group. The filaments of 8 eyes (42.11%) were distributed in the corneal damage or suture site (Fig. 3 ) in the surgery and chemical injury of the eyes group.
Table 2: Locations of filaments among different groups (eyes n [%]).
Figure 1: Filaments were restricted in the exposed interpalpebral zone caused by nonautoimmune forms of dry eye.
Figure 2: Filaments were distributed in the corneal limbus due to viral keratitis .
Figure 3: Filaments were distributed in the corneal suture site after penetrating keratoplasty.
In most cases, filaments disappeared, and fluorescein staining of corneal epithelial shedding became negative within a month of treatment. The treatment effect in the cases due to exposure keratitis or ocular surgical procedures was good. However, the treatment effects in the cases due to severe dry eye or autoimmune diseases were not ideal because, while the filaments decreased, the disease course was long (6 months–3 years).
4 Discussion
FK was most often caused by dry eye, especially aqueous tear-deficient (AQD) dry eye. Both autoimmune and nonautoimmune forms of AQD dry eye can give rise to corneal filaments.[4] keratitis , ocular surgical procedures (cataract surgery, PKP, and large-angle strabismus), recurrent erosion, neurotrophic keratopathy, vernal keratoconjunctivitis, prolonged use of an eye patch, and ptosis, among others.[5]
The FK induced by allergic conjunctivitis in group A was significantly higher than the other 2 age groups. The members of group A were at their childhood and youth stages, thus, their immune systems might be much more vulnerable to the influence of the external environment. Due to more severe atmospheric pollution, the incidence of allergic conjunctivitis is getting higher because the conjunctiva is in direct contact with air pollutants.[6,7] [8–10] [11]
The FK caused by nonautoimmune forms of dry eye in group A was much lower than the other 2 age groups. Patients in groups B and C were more likely to develop dry eyes because of daily activities including long-term contact lens wear, smoking, extended visual tasks with computers or mobile phone use, television watching, and prolonged reading. Furthermore, other factors that exacerbate dry eyes include being in an indoor environment and air pollution. These factors lead to excessive tear evaporation[12] [13] [14] [15]
The FK caused by surgery and chemical injury of the eyes in group C was significantly higher than the other 2 age groups. With aging, tear production is reduced and the number of people who undergo cataract or pterygium surgery gradually increases. It takes a period of time to recover the composition and production of the tear film and the healing of the corneal wound because of the inflammation from surgical stimulation. For these reasons, they are likely to lead to FK during this period.
In this study, the filaments of 52 eyes (80.00%) were restricted to the exposed interpalpebral zone in the dry eye and exposure keratitis group. The first part of the ocular surface involvement generally occurs in the exposed interpalpebral zone among the nonautoimmune forms of dry eye and exposure keratitis because tear secretion and TFBUT decreases. It is also characterized histologically by ocular surface inflammation, abnormal production of ocular surface mucins, alterations of epithelial morphology, and premature corneal epithelial exfoliation.[16] [17,18] [19,20]
By exploring the frequency and clinical features of FK, we believe that the findings from our research will be clinically significant and aid in the early prevention and treatment guidance of the disease.
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