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Year : 1998  |  Volume : 46  |  Issue : 1  |  Page : 1-2

Molecular techniques in ophthalmic practice

Correspondence Address:
B Rajeev

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Source of Support: None, Conflict of Interest: None

PMID: 9707840

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How to cite this article:
Rajeev B. Molecular techniques in ophthalmic practice. Indian J Ophthalmol 1998;46:1-2

How to cite this URL:
Rajeev B. Molecular techniques in ophthalmic practice. Indian J Ophthalmol [serial online] 1998 [cited 2023 Feb 3];46:1-2. Available from: https://www.ijo.in/text.asp?1998/46/1/1/14985

Molecular biology is a nascent scientific discipline that has made rapid strides since the elucidation of the deoxyribonucleic acid (DNA) structure to the more recent cloning of sheep. The molecular techniques that form the basis of this science have had a profound impact on biomedical research as well as clinical medicine, and their use in everyday ophthalmic practice is destined to increase exponentially over the coming years.

Although molecular biology actually connotes the study of all cellular events at the molecular level, for clinical applications the focus is on recombinant DNA technology which includes the isolation, amplification, cloning, analysis, sequencing, and detection of nucleic acids (DNA and ribonucleic acid [RNA]) in vitro. Two key techniques for clinical application are the polymerase chain reaction (PCR) and nucleic acid hybridization. The PCR involves in-vitro exponential enzymatic amplification of specific DNA segments. In nucleic acid hybridization, nucleic acid probes are used to identify specific nucleic acid sequences. These probes are pieces of DNA labeled with a marker and specifically bind to complementary sequences in the nucleic acid of tissue specimens. The basic concepts of these molecular techniques, which essentially are easy to understand, are described elsewhere in this issue.[1]

The increased usage of these techniques is largely due to their inherent advantage of enhanced specificity, sensitivity, speed, and the tiny amounts of tissue or ocular fluids that are required. These techniques work equally well with DNA from well-preserved archived tissue. This is in marked contrast to conventional techniques such as light microscopy, histochemistry electron microscopy, microbial cultures, and at times even immunohistochemistry. Advances in ocular microsurgery that now enable a relatively atraumatic biopsy and the accessibility of the eye have further increased the application of these techniques in ophthalmic practice.

In ophthalmic practice, these molecular techniques are of both diagnostic and therapeutic value. In diagnostic ocular pathology these techniques are set to surpass antibody-based techniques such as immunohistochemistry and enzyme linked immunosorbent assay (ELISA). In patients with atypical clinical features, PCR performed on vitreous or aqueous specimens has been used to diagnose cytomegalovirus retinitis, ocular tuberculosis, herpetic acute retinal necrosis, and toxoplasmosis. The number of infective agents that can be so identified from any ocular tissue (including a conjunctival swab) is increasing by the day. These techniques which till recently were the exclusive domain of well-equipped research laboratories, are now being developed on a commercial basis for routine use in the clinical laboratory.

These molecular techniques have led to the demonstration of the molecular basis of many genetic eye diseases including retinitis pigmentosa, retinoblastoma, gyrate atrophy, congenital cataract, and juvenile glaucoma. At present the use of ophthalmic genetics is limited to classification of inherited ocular diseases and genetic counselling since this knowledge allows us to detect these genetic traits and predict whether patients or their offspring are at risk of developing disease. Future potential applications include gene therapy (introduction of DNA into somatic cells to correct defective cellular function) or gene suppression (for example, using antisense molecules to suppress the production of abnormal proteins).

It is evident that these techniques have tremendous potential for deciphering the pathophysiology of ocular diseases unique to our sub-continent. An immediate potential application is to either prove or disprove the presumed tuberculos etiology of various ocular diseases including Eales' disease, central serous retinopathy, and central serous chorioretinopathy. Application of these techniques will transform a 'intuitive and anecdotal' ophthalmic practice into a more desirable 'evidence-based' ophthalmic practice.

In the context of our ophthalmic practice, in the coming years these techniques will influence the diagnosis, prognosis, and therapy in clinical ophthalmology. Improvements in specific antibiotic and antiviral therapy, and their mode of delivery for ocular infections will require an increasingly accurate diagnosis. Although these tests may not be available in all pathology laboratories, they will certainly be offered in reference laboratories, and a few of these techniques are already available in multispeciality ophthalmic hospitals in India. If an ophthalmologist has to become a true partner of the ophthalmic pathologist, he/she will have to know the theory and technique of molecular biology. Given the limitations of some of these tests, the ophthalmologist will have to critically evaluate the new molecular techniques in terms of quality control, standardization, reproducibility, and above all, clinical relevance.

  References Top

Rajeev B, Biswas J. Molecular biologic techniques in ophthalmic pathology. Indian J Ophthalmol 1998;46:3-13.  Back to cited text no. 1


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