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| PG CORNER |
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| Year : 2022 | Volume
: 34
| Issue : 1 | Page : 84-86 |
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Corneal biopsy
RB Radhika Krishnan
Department of Ophthalmology, RIO, TVM, Thiruvananthapuram, Kerala, India
| Date of Submission | 28-Jan-2022 |
| Date of Decision | 29-Jan-2022 |
| Date of Acceptance | 29-Jan-2022 |
| Date of Web Publication | 21-Apr-2022 |
Correspondence Address:
Dr. R B Radhika Krishnan
Department of Ophthalmology, RIO, TVM, Thiruvananthapuram, Kerala
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/kjo.kjo_19_22
How to cite this article:
Radhika Krishnan R B. Corneal biopsy. Kerala J Ophthalmol 2022;34:84-6 |
| Corneal Biopsy | |  |
Corneal biopsy is an effective aid in establishing diagnosis in a variety of corneal pathologies.
| Indications of Corneal Biopsy | | |
- Infectious corneal processes
- Deep suppurative stromal keratitis with no involvement of anterior stroma
- Sight threatening or progressive corneal infiltrate exhibiting one or more of the following
- Inadequate response to proper antimicrobial therapy
- Culture negative on repeated corneal scrapings
- Atypical clinical course.
- Infectious crystalline keratopathy if cultures not easily obtained with superficial scraping
- Suspicion of slow-growing fastidious organisms which are difficult to culture such as acanthamoeba, atypical mycobacteria, and microsporidium.
- Neoplastic limbal processes
- Suspected conjunctival neoplasms with corneal extension.
- Corneal dystrophies and degenerations
- Corneal manifestations of systemic diseases
- Drug-induced changes in cornea.
| Pre Procedure Evaluation | | |
- Slit-lamp biomicroscopic examination to assess the depth of infiltrating and surrounding corneal thickness
- Pachymetry can be used to measure the corneal thickness
- Confocal microscopic examination can be done to identify the presence or absence of infectious organism and in such cases, corneal biopsy can be avoided
- Topical antimicrobials should be stopped approximately 24 h before performance of biopsy if culture is planned.[1]
| Instrumentation, Anaesthesia, and Techniques | | |
Setting
Patient lying in supine position under the operating microscope. If patient is very cooperative, all techniques except trap door may be performed with patient seated at slit lamp biomicroscope. Under aseptic precautions operating eye is draped and if necessary speculum is inserted.
Anesthesia
Preservative-free topical anesthetic agent is instilled and if needed, a cotton tip applicator soaked in lidocaine may be held at limbal position where forceps fixation is performed.
Techniques
Different techniques for corneal biopsy are use based on the size and depth of the infiltrate and presence of thinning.
Excisional biopsy
Excisional biopsy is done in smaller peripheral ulcer where ulcer is excised totally [Figure 1].
Incisional biopsy
In larger ulcers, incisional biopsy is done where microtrephines are used to punch and then tissue is dissected deep to infiltrate and multiple incisional biopsies can be taken [Figure 2].
Centrifugal dissection
In deep and thin ulcers technique of lamellar dissection with centrifugal advancement is used to minimize the risk of perforation [Figure 3].
Lamellar flap biopsy
Used in mid to deep stromal lesions. Stromal tissue anterior to lesions is spared. This helps in decreasing the removal of excess corneal tissue which happens in prelamellar dissection. Incisions are made in surrounding relatively normal cornea and are 3–4 mm long triangular flap dissected at the level of lesion by keeping blade parallel to Descemet's membrane [Figure 4]. Within triangular flap, deeper plane is created from apex to base and a block of tissue is dissected. Bed of dissection is scraped and sent for culture. Flap is reapproximated and sutured with 10.0 nylon suture.[2]
Trephination using slit-lamp biomicroscopy
Topical anesthetic is instilled and a sterile, handheld trephine (2–3 mm dermatological punch) is used at the slit lamp to achieve a partial thickness trephination containing pathological specimen [Figure 5]. The size of the trephine depends on the size of the lesion. Trephine is positioned at the junction of diseased and normal corneal tissue. After the partial thickness trephination, the edge of the lesion in the area of the normal tissue is lifted using 0.12 forceps and dissected off the cornea using a blade.
Femtosecond laser can also be used for corneal biopsWy
| Specimen Handling and Processing | | |
Biopsy specimen should be adequate enough to send for both microbiological and histopathological examination, specimen should include at least 1 mm of adjacent clear cornea at the leading edge of the ulcer. Biopsy tissue should be sent as two samples one for microbiological culture in normal saline and one for histopathological examination in 10% formalin.
| Complications | | |
- Delayed healing
- Inadvertent perforation
- Visually significant scarring
- Dellen formation
- Astigmatism
- Thinning.
If perforation happens, it results in aqueous humor leakage and/or introduction of infectious organisms into anterior chamber. A simple incision/flap made in cornea is sutured with 10.0 nylon. If not able to maintain deep anterior chamber, may place thin application of cyanoacrylate tissue adhesive over flap followed by bandage contact lens placement. If tissue is necrotic and closure is not possible with sutures/tissue adhesive, then corneal or scleral patch graft can be done.[3]
| How to Prevent Perforation? | | |
- Thorough slit-lamp biomicroscopic examination before the procedure to estimate depth of infiltrate and nearby corneal thickness
- Ultrasonic pachymetry can be done before lamellar dissection
- Corneal imaging with optical coherence tomography/ultrasonography to determine corneal thickness and depth of lesion before dissection.
| Follow-up and Patient Instructions | | |
- Antimicrobial therapy should be restarted after the biopsy
- Treatment is modified according to the results of microbiological and histopathological investigations
- Patient should be instructed not to rub the eye.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
| References | | |
| 1. | Yanoff M, Duker JS. Ophthalmology. Yanoff M, Duker JS: Ophthalmology 5 th ed. Edinburgh:Elsevier. 2019;p. 306-7.  |
| 2. | Alexandrakis G, Haimovici R, Miller D, Alfonso EC. Corneal biopsy in the management of progressive microbial keratitis. Am J Ophthalmol 2000;129:571-6. |
| 3. | Weisenthal RW. Basic and Clinical Science Course. Section 8:External Diseases and Cornea American Academy of Ophthalmology 2020-2021.. |
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
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