|Year : 1989 | Volume
| Issue : 1 | Page : 20-23
Is the test patch useful in determining safety against operative infection?
Rajvardhan Azad, Manoj Rai Mehta
R.P. Centre for Ophthalmic Sciences, AIIMS, Ansari Nagar, New Delhi - 110 029, India
R.P. Centre for Ophthalmic Sciences, AIIMS, Ansari Nagar, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
The practice of pre-operative 'Test Patch' on any eye continues to be an important, conventional step at a number of eye infirmaries. The present study was carried out on eighty seven eyes to determine the relevance of Test Patch as a prelude to surgery. After a critical analysis of the result of investigation, it is concluded that the 'Test Patch' does not provide a statistically reliable information regarding potential bacterial infection since there is no correlation between pre-patching and post-patching clinical appearance, and bacterial isolates in a given case. Presence of polymorphs or organisms in the Grams stained conjunctival smears did not make any difference with regard to a positive or negative bacterial growth in a given eye. It is concluded that 'Test Patch' neither predicts nor helps in any way in a case waiting to undergo intra ocular surgery. The Test Patch, therefore, at best, can serve as an acclimatizing exercise that simulates bandaging in the post-operative period.
|How to cite this article:|
Azad R, Mehta MR. Is the test patch useful in determining safety against operative infection?. Indian J Ophthalmol 1989;37:20-3
|How to cite this URL:|
Azad R, Mehta MR. Is the test patch useful in determining safety against operative infection?. Indian J Ophthalmol [serial online] 1989 [cited 2020 Apr 6];37:20-3. Available from: http://www.ijo.in/text.asp?1989/37/1/20/26109
| Introduction|| |
The comprehensive knowledge of the conjunctival flora has accumulated over the years through the efforts of the early. Microbiologists and the Ophthalmologists, ,,,,, Systematic investigations in ocular infections were started soon after the invention of the microscope, however the attention towards the study of the healthy eye was drawn in the late 19th century when Foote  reported that the healthy conjunctival sac is free of organisms in most of the cases.
An important discovery was made by Eyre  who found bacterial contamination to be predominant in the lower fornix of the eyes that yielded growth. Back  and Hauenschild  isolated bacteria from the nostrils of the experimental animals 24 hours after inoculation into the conjunctival sacs. The foundations of modern ocular microbiology were firmly laid by Morax  and Axenfeld together ,, Their extensive investigations resulted in the co-discovery of the Morax-Axenfeld diplobacillus.
The clinicians have been interested in studying the bacterial growth in the eyes after patching, which is resorted to in several situations. The precise origin and expected utility of pre-operative overnight patch is not known.
The present study has been carried out to critically evaluate the effect of a `Test Patch' on an eye and its predictability in cautioning the surgeon against operating upon an eye predisposed to infection.
| MATERIAL & METHODS|| |
The study included 87 eyes which underwent complete ophthalmological check-up for cataract extraction on day 1. Special attention was given to conjunctival congestion, lid margin hyperaemia, scaling, crusting, concretions and regurgitation from the lacrimal sac on digital pressure. A swab was sent from the eye for isolation of any organism in the manner described later. On day 2 'Test Patch' was applied on the eye waiting to undergo surgery in the manner described below.
| Swab for isolation of bacteria|| |
A sterile cotton tipped applicator dipped in a sterile nutrient broth solution was rolled over the lower fornix from the temporal to the nasal side after gently pulling the lower lid away from the eye ball. Precautions were observed to prevent the contact of the moistened tip with the lid margins, cilia, skin of the lids or the exterior of the despatch bottle. The swabs were sent to the microbiology laboratory in autoclaved bottles,. where plating on the blood agar was performed immediately.
| Test patch|| |
A sterile cotton pad was kept over the test eye after lid closure and a bandage was applied. The pad was examined the next morning for accumulation of any discharge and the eyes examined for matting of the lashes, crusting or discharge over the lids or presence of frank conjunctivitis. The following grading of hyperaemia and discharge was followed throughout the study.
0; Palpebral and bulbar vessels of normal colour/caliber. 1; Vasodilatation and redness of the bulbar and the palpebral conjunctiva with mucoid discharge. 2; Moderate vasodilatation with thick mucoid or mucopurulent discharge. Marked dilatation with or without frank conjunctivitis with matting and crusting.
After clinical grading a smear was made from the conjuctival fluid for Gram's staining and a swab was sent for microbiological analysis.
| Result|| |
The result have been provided in [Table - 1][Table - 2][Table - 3][Table - 4][Table 5].
There was a lack of correlation between the clinical appearance of the eye and the isolation of bacteria either before or after patching. Before the test patch (44.8%) eyes yielded growth of the various organisms, Staph albus being the commonest (37.9%). After the patch, the clean looking eyes had stopped growing staph albus in 38.5% cases, staph aureus in 2% Pneumococci in 5.1 % and Pseudomonas in 2.6% of cases. At the same time 54.2% of the staph albus were sterile, when the conjunctival fluid was plated on the blood agar plates. [Table - 1][Table - 2][Table - 3] The pre-patching microbiological status of an eye did not have any statistically significant bearing on the post patching bacterial isolation and it is important to not that the pre patching bacterial isolation did not effect the clinical appearance of an eye significantly after the patch. [Table - 2] There was no correlation between the `grade' of hyperaemia discharge and bacteriologic status in the post-patch eyes. The presence of polymorphs or organisms in the Gram's stained smear also did not have any correlation with the bacterial isolation from the eyes after patching. [Table - 4]
| Discussion|| |
The `Test Patch' has generated much debate in Ophthalmology circles in the past. It is believed to interfere with the tear drainage mechanism causing stasis and promotes the growth of the bacteria by raising the temperature in the cul-de-sac. Fatt and Chaston  used a bolometer between the closed lids in their study and confirmed the rise in temperature.
Linder  and Piilat  were probably the first workers to demonstrate that practically every eye exhibits some bacterial flora. They reported a wide range of organisms-Bacillus xerosis (100%), Staphylococcus epidermidis (94%), Pneumococcus (4%) and Haemophilus lacunatous (22%). In our study the isolates from healthy eyes include staph albus (37%) and Pneumococcus (2.2%). This is in agreement with the results obtained by Kharazo & Thompson1. The smear examination after Gram's staining also did not provide any clues to the possible bacterial contamination.
In our study the fluid from the lacus lacrimalis was collected with the help of a cotton applicator and was immediately plated on blood agar.  We also tried to correlate Grain's smear findings with bacterial culture from tears and found that the smear examination is not sufficient to reveal pathogenic organisms. This corroborates the earlier study carried out by McKee. 
The `Test Patch' therefore does not give reliable information regarding the bacteriological safety in intraocular surgery, rather it has several fallacies viz. (i) the bandage itself induces conjuctival secretion and reaction even after anti-biotic treatment for a few days  (ii) the absence of lid action may aggravate a subclinical infection and (iii) the test is not entirely trust-worthy as the pathogenic bacteria may be present in the recess of a Meibomian gland, the caruncle or elsewhere.  Is the `Test Patch' entirely useless, then? It may be of a limited utility when a surgeon is to operate upon the only potentially functional eye. It also provides information regarding the behaviour of the conjunctival flora to patching and acclimatizes the patients to a post-operative patching. A patient may derive psychological benefit of a dress rehearsal. Pre-operative cultures though not entirely justified statistically, provide a bullwark of safety especially from the medico-legal point of view.
What can we do to prevent infection in the post operative period? The measures, which could be taken are (i) Instillation of a broad spectrum antibiotic a few days before the surgery. (ii) Trimming and removal of loose lashes one or two days before surgery (iii) Postponement of surgery in the presence of Gram negative isolates. (iv) Washing the conjuctival sac thoroughly before draping the patient for surgery.
An Ophthalmologist should remember that due to extensive and unsupervised use of antibiotics and steroids, invasive strains of Staphylococcus epidermidis are emerging, which are resistant to the routinely used antibiotics. This causes relentless low grade infection. Therefore, injudicious use of steroid and antibiotics must be curbed to reduce the emergence of invasive strains of the normal commensals in the conjunctiva.
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[Table - 1], [Table - 2], [Table - 3], [Table - 4]