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Updated: Apr 3, 2026
Impression Cytology of the Lid Wiper Area
Published on: August 9, 2016
Impression membrane for the diagnosis of microbial keratitis
Stephen Kaye1, Henri Sueke1, Vito Romano2
1St Pauls Eye Unit, Royal Liverpool University Hospital, Liverpool, UK Department of Eye and Vision Science, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK.
Purpose:
To evaluate a corneal impression membrane (CIM) for isolation of bacteria, fungi and acanthamoeba in suspected microbial keratitis.
Methods:
Consecutive patients presenting with suspected microbial keratitis were included. For each patient, samples were collected in a random order using a surgical blade and a 4-mm-diameter polytetrafluoroethylene CIM disc, and transported in brain heart infusion broth. Risk factors, best corrected visual acuity (BCVA), size, location, depth and healing time of the ulcer were recorded. The microbial isolation rate was used to compare sampling methods.
Results:
130 patients were included (mean age 62.6 years, SD 19.0). An antimicrobial had been used prior to presentation in 36 (27.7%) patients. Mean major and minor ulcer diameters were 2.1 mm (SD 2.0) and 1.6 mm (SD 1.7). Mean healing time was 12.4 days (SD 13.6). BCVA at presentation and following healing was 0.7 (SD 0.7) and 0.62 (SD 0.7) (p=0.34). There were 66 isolates (50.8%); 53 (40.8%) using a CIM and 35 (26.9%) using a blade (p=0.02). ITALIC! Staphylococcus aureus and coagulase-negative staphylococci were the commonest isolates. Isolation rate was not influenced by organism type, although in four cases ITALIC! Acanthamoeba spp. were isolated; three using CIM and one a blade.
Conclusions:
In this study, the isolation of microorganisms from cases of suspected microbial keratitis was significantly higher using a CIM than a surgical blade. A CIM may be a useful alternative or addition for sample collection in microbial keratitis.
Insights
A corneal impression membrane (CIM) significantly improves microbial isolation rates in suspected microbial keratitis cases compared to traditional blade sampling. This method offers a valuable alternative for diagnosing eye infections.
Area of Science:
- Ophthalmology
- Microbiology
- Medical Diagnostics
Background:
- Microbial keratitis is a serious eye infection requiring prompt diagnosis.
- Accurate identification of causative microorganisms is crucial for effective treatment.
- Current sampling methods may have limitations in microbial yield.
Purpose of the Study:
- To compare the efficacy of a corneal impression membrane (CIM) versus a surgical blade for isolating bacteria, fungi, and Acanthamoeba in suspected microbial keratitis.
- To evaluate the diagnostic yield of CIM in microbial keratitis cases.
Main Methods:
- A comparative study involving consecutive patients with suspected microbial keratitis.
- Samples were collected using both a surgical blade and a 4-mm polytetrafluoroethylene CIM disc.
- Microbial isolation rates were compared between the two sampling methods.
Main Results:
- The corneal impression membrane (CIM) achieved a significantly higher isolation rate (40.8%) compared to the surgical blade (26.9%) (p=0.02).
- Common isolates included Staphylococcus aureus and coagulase-negative staphylococci.
- Acanthamoeba spp. were isolated in four cases, with three identified using the CIM.
Conclusions:
- The corneal impression membrane (CIM) demonstrates superior performance in isolating microorganisms from suspected microbial keratitis.
- CIM is a promising alternative or adjunct for sample collection in diagnosing microbial keratitis.
- Improved diagnostic yield with CIM can potentially lead to more timely and appropriate treatment of eye infections.
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