Infective fungal keratitis reported to range from 5%

 

       Infective keratitis is a common cause for corneal blindness in India.
Fungal infections are the commonest of all forms of infective keratitis 1-3.
A contributing factor for development of fungal infection is ocular trauma and
contamination of corneal lesions by soil and plant material. Another factor
which contributes to increased incidence is widespread use of broad spectrum
antibiotics and steroids 4.Fungal keratitis is often difficult to manage with
medical therapy alone 5-8.The management of fungal keratitis poses several
challenges. The reasons for poor response to medical treatment are due to a
delay in diagnosis and lapse in early institution of the therapy when the
infiltrate is smaller size. One major limiting factor in the management of
fungal keratitis is the absence of fungicidal medications. All medications are
fungistatic and hence the treatment success with medications alone is limited.9-10
 An important cause of treatment failure
is fungal recurrence after surgery, with the rate of recurrence of fungal
keratitis reported to range from 5% to 14% 5-8.Thus, fungal recurrence after
keratoplasty is still a significant challenge for ophthalmologists. The post operative period can be complicated
by recurrences of the infection. It is well known that corticosteroids are
detrimental and favour the growth of fungus; hence topical corticosteroids are
withheld immediately after keratoplasty. As a consequence the inflammation in
the initial post–operative period is prolonged, thereby affecting the graft
outcomes. The reasons for recurrence fungal infections may be due to delay in
diagnosis and lapse in early institution of the therapy.9

The purpose of this study was to analyse the
outcomes of therapeutic penetrating keratoplasty for fungal keratitis.

Materials and methods

     The study was
approved by the Institutional Ethics Committee and followed the tenets of
Declaration of Helsinki.

Patients

A total of 198 fungal keratitis patients who did not
respond to topical and systemic antifungal drugs underwent corneal transplantation
by means of Therapeutic PK (ThPK) at L V Prasad Eye Institute, Hyderabad, India
between 2008 -2010 were included in the study . Data collected included
demographics, microbiology of ulcers, type of surgical procedure performed,
details of donor tissue in terms of Donar age, graft size and endothelial
density, duration of follow up, time period of recurrence, clinical features of
the recurrent keratitis, and management of recurrent keratitis.

Diagnostic Methods
and Medical Management before Surgery

   The standard practice pattern at the
institute for the management of keratitis is described here briefly. All eyes
clinically evaluated to have infection, irrespective of their previous
diagnosis and treatments undergo a microbiological evaluation. The diagnosis of
fungal keratitis is made on KOH mount, smear examinations and slit lamp
microscopy. Following a microbiological confirmation on smears and/or culture
antifungal treatment is instituted comprising of Natamycin 5% suspension every
hourly and oral Ketoconazole twice/day. If the status of corneal ulcers
deteriorated or did not improve after periodic follow up of 3 days, therapeutic
penetrating keratoplasty is planned under a local /general anaesthesia to
eliminate the eye of the infection. All patients underwent B-Scan ultrasound
before corneal transplantation to exclude endophthalmitis.

Surgical technique
and postoperative management

The TPK was performed under peribulbar block. Intra-operatively,
care is taken to size the graft 1 mm more than the area of the infiltrate in
its widest dimensions. For routine TPK, after removal of the diseased cornea, the
anterior chamber angle and iris surface were irrigated carefully with saline to remove any exudates and hypopyon at the angles and
careful inspection is done at the edges of the host to ensure that the area of
infiltrate is completely excised. In those eyes, with total corneal infiltrate,
peritomy is done to inspect the sclera of any contiguous spread and part of infected
sclera (as much is feasible to preserve the angle anatomy) is included in the
trephination). For cases with spontaneous rupture of the lens capsule resulting
from fungal infection or having dense cataract, extracapsular cataract extraction
(ECCE) was performed. Corneal grafts were secured with 16 interrupted 10-0
nylon sutures.At the time of TPK, the infected corneal tissue is divided
into 2 parts- One part of the tissue is sent for microbiological evaluation and
second is subjected to histological study. The post-op care post therapeutic
keratoplasty comprises of receiving frequent instillation of antifungal agents
and oral ketoconazole for 2 weeks along with antibiotics drops and nonsteroidal
anti-inflammatory drops. Assessment was made for any recurrence during 2 weeks time
interval, and initiating low dose topical steroids only after a period of 10-14
days when the eye is clinically evaluated to have no evidence of residual/
recurrence of infection.

Detection and
Treatment of recurrence

In the postoperative examination of the patients with
suspected Recurrence, Slit lamp microscopy and Corneal scrapings were incubated
and examined as wet mounts with KOH; they then were subjected to fungal culture
and strain identification. The finding of fungal filaments from any of the
above examinations served as confirmation of fungal recurrence. All recurrent
patients received eye drops of Natamycin 5% every 30 minutes combined with eye
drops of oral ketazonol. Anterior chamber recurrence was controlled with an
intracameral injection of amphotericin B along with AC wash. Patients with
posterior segment recurrence also received an intravitreal injection of
amphotericin B along with IOAB if required. Surgical treatment was used when
drug therapy was shown to be ineffective after approximately 5 to 7 days.

Statistical Analysis:

The software Origin v 7.0 (OriginLab Corporation,
Northampton, MA, USA) was used to perform the statistical analysis. Normality
of the continuous data and homoscedasticity were evaluated using Shapiro-Wilk
and Levene tests respectively. Mean (± standard deviation) and median (along
with inter-quartile range, IQR) were used to describe the parametric and
non-parametric data respectively. Kaplan-Meier survival plots were done for
time-to-event analyses. The recurrence rate after TPK and the presence of
different risk factors were compared with chi-square analysis. An initial
univariate stratified analysis was performed to identify and select important
risk factors for recurrence in the regression model. A p-value of <0.05 was considered statistically significant.   Results:   Demographics - Mean age of the patients was 44.95 (Range 10-80) Years. 129 were males and 69 were females. Majority of the patients hailed from within the state and 25 were from outside states. The mean duration of symptoms to the time when seen in the clinic was 16.7 (Range 1-90) days. The duration between the symptoms to the time of TPK was 20.9 (Range 1-120) days.   Pre-operative Characteristics - All patients had infiltrate involving the central visual axis and hence the pre-operative vision was hand motions. At the time of TPK, 41 eyes had infiltrate size <6 mm, 77 eyes had infiltrate size between 6-8 mm, and 80 eyes had infiltrate dimensions> 8 mm. All of them had infiltrate involving full thickness of the
cornea, 54 eyes had hypopyon, 8 eyes had descemetocele with perforation, and 2
eyes had sclera involvement. None of the patients had evidence of posterior
segment involvement on B scan ultrasonography

 

Microbiological characteristics – In
all eyes, the initial microbiological smear re-examination revealed fungal filaments.
Cultures from either the initial scrapings and or half corneal button obtained
after TPK was positive in 189 cases. The species identification on
microbiological work up revealed Aspergillus flavus in 64 eyes, fusarium
species in 31 eyes, acremonium species in 35, Cladosporium in 1 eye, Curuvalia
in 2 eyes Scedosporium in 1 eye; 44 eyes had unidentified hyaline fungus, 10
were dematicious fungi and 1 patient with unidentified hyaline fungus had a
co-infection with Pseudomonas aeroginosa species.

Intra-operative/Surgical characteristics – The
Donor graft size was 8-9 mm in 35 eyes, 9-11 mm in 108 eyes, > 11mm in 49 eyes
and 6 had missing information. 8 eyes had a combined surgical intervention that
included- extracapsular cataract extraction in 4 eyes, Extra capsular cataract
extraction with Anterior vitrectomy in 4 eyes, and IOL explanation in 1 eye.
The preoperative characteristics of all the eyes are summarised in Table 1.

Baseline Donor characteristics – Mean
age of the donor corneas was   69.7 (Range
19-98) years. Mean endothelial cell density of the donor corneas was 2231.9 (1043-3436)
cells/mm2.

 

Primary Outcomes measures

 

     Anatomical restoration was achieved in majority of cases
(192 of 198 eyes; 96.97%).

Out of the 6 eyes, 3 eyes required evisceration and 3 eyes
went Phthsical. All these eyes in which anatomical stability could not be
achieved had recurrence in AC along with Posterior segment involvement in 3
eyes. Recurrence in these eyes occurred in a mean of 11 days (Range 1 to 28
days). Pre-operatively out of 6 eyes, 3 eyes had endo exudate, 2 had endo
exudate along with Hypopyon and only 1 eye had cataract. All eyes required
larger graft size 9.75mm (Range -8.5 – 11.5 mm).

 

 

 Out of 198 subjects
who underwent a TPK, 178 had no recurrence of fungal infection. Fungal
recurrence developed in patient between 1 and 27 days after surgery. Among the
20 recurrent patients, 8 patients developed recurrence within 7 days of TPK, 5
patients recurrence developed after 8 to 20 days and 7 patients after 20 days
of TPK. There sites of recurrence were: the recipient bed (5 patients),
anterior chamber (7 patient), Involving both recipient bed and AC (4 patients),
AC with posterior segment (3 patient) and GHJ, 1 patient had recurrence
involving GHJ, AC and Posterior segment. Only 4 patient had cataract
preoperatively.

 

 6 patients were found to be infected with same
species of fungus as had been identified before corneal transplant; out of the
remaining 13 patients, 6 patient smear report suggested the presence of fungus
filaments and 3 patients were found to have negative result by fungal culture
but responded to administration of antifungal medical therapy and 4 patients
did not had any smear done after detection of recurrence.

 

     Among
the 5 patient with recipient bed infection, 2 was treated with medical therapy
alone, 2 required repeat TPK and 1 had to undergo evisceration due to scleral
involvement. Anterior chamber recurrence was
controlled with an intracameral injection of amphotericin B along with AC wash
followed by anti fungal medical therapy in 5 patients and 1 eye went Phthsical
after 1 month and 1 patient lost Follow Up. Eyes involving both GHJ and AC were
treated with repeat PK for 2 eyes and 2 eyes received AC wash and intracameral injection
along with topical medical therapy. With posterior segement involvement 2 eyes
developed endophtalmitis and 2 went phthsical. As soon as the recurring
infection went under the graft, drug therapy was ineffective and required
surgical intervention to protect the anatomical stature of the eye

Table 2 gives details mentioning the Clinical Course of
recurrent fungal infection after Therapeutic keratoplasty.

 

Secondary
Outcomes Measures:

 

Graft
clarity:

178 patients had complete eradication of fungal infection.
Of the 178 eyes, graft clarity was restored in 52 eyes at 3 months, 21 eyes at
1 year and 11 eyes at 4 years. 45 eyes had primary graft failure at 1 month and
Subsequent intervention of Regrafting (PK/DSEK) was done in 27 Eyes (13 eyes
for DSEK and 14 eyes for PK). 11 eyes (5.5%) maintained a clear graft during a
median follow up period of 48 months (range, 1- 60 months). Median graft
survival rate was 5.88 months. Clear TPK’s were significantly associated with
smaller graft size (P = 0.026). The
mean graft size was 8.5mm with mean Donar Endothelial cell density of 2364.83.

 

Secondary
Infection: Twenty four eyes (12%) developed a
secondary infection after a follow up period of 1 month (range, 1 -36 months).
Out of those 24 eyes, 10 eyes developed secondary bacterial infection (GPC
& GNB) whereas 12 Patient did not have any smear report performed for them.

 

Visual
Outcomes: As all patients had visual axis involvement, pre-operative visual
acuity was hand motions to counting fingers at 3 mtrs. The median postoperative
best-corrected visual acuity for all survived grafts was 20/100 at 3 months,
20/60 at 6 months and  20/40 at 1 year.
At 5 years follow up visit, the best-corrected visual acuity was ?20/50 in 7/10
eyes. No significant difference in terms of postoperative visual gain between
different species of fungus was seen; however, eyes with smaller grafts
(<9mm) had a postoperative BCVA >20/200 more frequently compared to eyes
with larger graft of 9-11mm and >11mm.

 

The table 3  below
describes clinical characteristics of all the 11 eyes whose primary graft
remained clear, maintaining a visual acuity of >20/100 upto a follow up
period of 48 months. 10 out of 11 patients maintained BCVA ?20/50, out of which
two eyes had BCVA 20/20. Preoperatively, all 11 eyes had corneal infiltrate
size less than 9 mm. Mean age of donor was 71.25 years (Range 40 years to 90
years). Mean ECD of donor cornea was 2364.83. Three eyes had reduction in
visual acuity in subsequent follow up visit (mean follow up period 4 months).
It was because the grafts had an early episode of rejection at that particular
time but was well managed with medical therapy and hence, maintained visual
acuity better than 20/60 at a follow up period of 48 months.

 

 

Risk factor Analysis:

 

The
presumed risk factors for primary graft failure and recurrence of infection in
TPK were analysed. The variables were categorized as follows: size of
infiltrate (<6mm, 6-8mm and >8mm), size of graft (8-9mm, 9-11mm and >11mm),
species of fungus (Aspergillus, Fusarium, Acremonium, Unidentified hyaline
fungus and others) and additional cataract surgery with EK (presence/absence).
Graft size was the only significant risk factor for graft failure and recurrence
in this series (p = 0.01) and (p = 0.02) respectively. Figure 1 shows the
probability of graft survival over time. The probabilities of survival are 48.9%,
29.4%, 13.6% and 10.5% at 6 months, 1, 3 , 4 years respectively.