BIOMETRY (IOL MASTER) Biometry is the process of measuring the power of the cornea (keratometry) and the length of the eye, and using this data to determine the ideal intraocular lens power. If this calculation is not performed, or if it is inaccurate, then patients may be left with a significant refractive error.
A-SCAN A-scan ultrasound biometry, commonly referred to as an A-scan (short for Amplitude scan), is a routine type of diagnostic test used in optometry or ophthalmology. The A-scan provides data on the length of the eye, which is a major determinant in common sight disorders. The most common use of the A-scan is to determine eye length for calculation of intraocular lens power.
B-SCAN [ULTRASONOGRAPHY] B-scan ultrasonography (USG) is a simple, noninvasive tool for diagnosing lesions of the posterior segment of the eyeball. Common conditions such as cataract, vitreous degeneration, retinal detachment, ocular trauma, choroidal melanoma, and retinoblastoma can be accurately evaluated with this modality.
DIGITAL FUNDUS FLUORESCEIN ANGIOGRAPHY Fluorescein angiography (FA) or Fundus fluorescein angiography (FFA) is a technique that is used for examining the blood flow in the retina and choroid using a fluorescent dye and a specialized camera. This Specialized camera is known as a Digital Fundus camera and it is used to take an image of the fundus — the back portion of the eye that includes the retina, macula, fovea, optic disc and posterior pole. A digital fundus camera normally consists of a camera with a specialized microscope attached.
ICG ANGIOGRAPHY Indocyanine Green Angiography (ICG) is a diagnostic procedure that uses ICG dye to examine the blood flow in the CHOROID – the layer of blood vessels which lies underneath the retina
FUNDUS PHOTOGRAPHY Fundus photography involves photographing the rear of an eye; also known as the fundus. Specialized fundus cameras consisting of an intricate microscope attached to a flash enabled camera are used in fundus photography. The main structures that can be visualized on a fundus photo are the central and peripheral retina, optic disc and macula. Fundus photography can be performed with colored filters, or with specialized dyes including fluorescein and indocyanine green. OPTOS – It is a non invasive OCT machine used for choroidand retinal blood flow
UBM (ULTRASOUND BIOMICROSCOPY) Ultrasound Biomicroscopy (UBM) is a technique primarily used for imaging of the anterior segment (AS) of the eye. UBM can be used for imaging much of the anatomy of the anterior segment, as well as associated pathologies, including angle closure glaucoma, ciliary body cysts, neoplasms, and angle trauma. It is a type of ultrasound eye exam that makes a more detailed image than regular ultrasound. It is useful in detecting glaucoma, cysts and neoplasms of the eye, as well as in the evaluation of trauma and foreign bodies of the eye.
SPECULAR MICROSCOPY The corneal endothelium is a simple, squamous epithelial sheet on the posterior side of the cornea and it is responsible for maintaining proper corneal hydration. Corneal endotheliopathy is a broad term used to classify several diseases and clinical circumstances that affect the structure and function of the corneal endothelium. Specular microscopy is a noninvasive photographic technique that allows an Ophthalmologist to visualize and analyze the corneal endothelium.
HRT (HEIDELBERG RETINAL TOMOGRAPHY) – The Heidelberg Retina Tomograph (HRT) is an ophthalmological confocal point-scanning laser ophthalmoscope for examining the cornea and certain areas of the retina using various diagnostic modules (HRT retina, HRT cornea, HRT glaucoma). The most widely used area of application of HRT is the inspection of the optic nerve head (papilla) for the early detection and follow-up of the glaucoma.
OCT (OPTICAL COHERENCE TOMOGRAPHY) Optical Coherence Tomography (OCT) is a commonly performed diagnostic test designed to assist an Ophthalmologist in identifying retinal diseases, such as age-related macular degeneration (AMD) or diabetic retinopathy (diabetic eye disease). It is effectively ‘optical ultrasound’, imaging reflections from within tissue to provide cross-sectional images. OCT can be used for both the segments of the Human eye, namely, the anterior segment and the posterior segment. The Anterior Segment OCT is used to visualize the images of the anterior segment of the eye - cornea, anterior chamber, iris and angle. The Posterior Segment OCT, on the other hand, is used in evaluating the Posterior Segment of the human eye to detect/diagnose Retinal conditions and Optic nerve disorder. OCTA – 200° widefield fundus photo
CORNEAL TOPOGRAPHY Corneal topography, also known as Photokeratoscopy or Videokeratography, is a non-invasive medical imaging technique for mapping the anterior curvature of the cornea, the outer structure of the eye. Since the cornea is normally responsible for some 70% of the eye's refractive power, its topography is of critical importance in determining the quality of vision and corneal health.
RETCAM EVALUATION The RetCam is an advanced, wide-field digital imaging system that delivers the next generation of ophthalmic visualization, photo documentation and ease of use. This wide - field ophthalmic imaging camera captures brilliant, full color images that can be used for immediate evaluation of pediatric ocular pathology.
OCULAR PENTACAM ANALYSIS Pentacam is the most commonly used corneal tomography system. It creates a 3-D imaging of the anterior segment and provides details of the anterior and posterior corneal contour, pachymetery, and anterior chamber depth and pupil diameter. The Pentacam Comprehensive Eye Scanner is a rotating camera that photographs both the anterior (front) and posterior (back) surfaces and other areas of the cornea (the front part of the eye).
GONIOSCOPY (DIRECT/INDIRECT) Gonioscopy is an eye examination to look at the front part of the eye (anterior chamber) between the cornea and the iris. Gonioscopy is a painless examination to see whether the area where fluid drains out of the eye (called the drainage angle) is open or closed. There are two basic types of gonioscopy: direct and indirect. In Indirect Gonioscopy, the viewer will have an inverted and slightly foreshortened image of the opposite angle because the light from the angle is reflected off of a mirror and directed towards the viewer. The lenses used in indirect gonioscopy use mirrors to overcome total internal reflection. Direct Gonioscopy, on the other hand, provides a straight-on view of the angle rather than the mirror image given by the indirect lenses. Direct gonioscopy permits the examiner to vary the angle of visualization more readily
TONOMETRY (GOLDMANN, PERKIN, TONOPEN, NONCONTACT TONOMETERS) Tonometry is a procedure that is performed to determine the intraocular pressure (IOP) of the eye (fluid pressure inside the eye). It is an important test in the evaluation of patients at risk from glaucoma. Different methods of Tonometry are utilized:
Applanation Tonometry
Goldman Tonometry
Perkins Tonometer
Tonopens
Noncontact Tonometer
VISUAL FIELD ANALYSIS (HUMPHREY/OCTOPUS) A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, pituitary disease, brain tumours or other neurological deficits. Visual field testing can be performed clinically by keeping the subject's gaze fixed while presenting objects at various places within their visual field. Simple manual equipment can be used such as in the tangent screen test or the Amsler grid. When dedicated machinery is used it is called a perimeter. The Humphrey Field Analyzer (HFA) is a tool for measuring the human visual field that is commonly used by our optometrists, and ophthalmologists, particularly for detecting monocular visual field. The results of the analyzer identify the type of vision defect. Therefore, it provides information regarding the location of any disease processes or lesions throughout the visual pathway. This guides and contributes to the diagnosis of the condition affecting the patient's vision. These results are stored and used for monitoring the progression of vision loss and the patient's condition.
SLIT LAMP PHOTOGRAPHY A slit lamp is a microscope with a bright light used during an eye exam. It gives the ophthalmologist a closer look at the different structures at the front of the eye and inside the eye. It's a key tool in determining the health of the eyes and detecting eye disease. Slit Lamp Photography utilises a variety of magnifications, angles of view and types of illumination to highlight the areas of interest. This is especially useful in following progression or changes in specific pathology such as new vessels, cataracts and pterygium.
CORNEAL PACHYMETRY (OPTICAL/ULTRASOUND) Corneal pachymetry is the process of measuring the thickness of the cornea. A pachymeter is a medical device used to measure the thickness of the eye's cornea. It is used to perform corneal pachymetry prior to refractive surgery, for Keratoconus screening, Cataract, LRI surgery and is useful in screening for patients suspected of developing glaucoma among other uses. Modern devices use ultrasound technology, while earlier models were based on optical principles. Both these models are used at Sri Sankaradeva Nethralaya.
CONFOCAL MICROSCOPY Confocal microscopy or laser confocal scanning microscopy (LCSM), is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a spatial pinhole to block out-of-focus light in image formation
ABERROMETER An Aberrometer is a diagnostic device that measures refractive aberrations of the eye. It is used in laser eye surgery to ensure high accuracy.
DIPLOPIA CHARTING Diplopia, or Double Vision, is when a person sees two images of the same thing. A person might have diplopia in one eye or both. Generally, double vision in both eyes is more serious than having double vision in just one. With a careful evaluation and accurate diagnosis, double vision can often be effectively treated. Diplopia charting refers to the recording of separation of the diplopic or double images in the nine positions of gaze.
TEAR FILM ANALYSIS (OSMOLARITY, MMP-9) The tear film is a unique thin fluid layer that covers the outer mucosal surfaces of the eye. As such, it is the interface of the ocular surface with the environment.
KERATOMETER A Keratometer, also known as an Ophthalmometer, is a diagnostic instrument for measuring the curvature of the anterior surface of the cornea, particularly for assessing the extent and axis of astigmatism.
PAM (POTENTIAL ACUITY METER) A PAM measurement is sometimes appropriate as an estimate of potential vision prior to a surgical procedure, especially cataract surgery. The main purpose of performing this test is to get an idea of the visual acuity that the patient can potentially achieve.
VEP (VISUAL EVOKED RESPONSE) VEP testing is used to investigate the pathways that carry signals from the patient’s eye to the brain.
ERG (ELECTRORETINOGRAPHY) It is one of the most common forms of visual electro diagnostic testing. It records the electrical signals sent from the retina during this testing. ERG Testing examines both the rods and cones of the eye.
mfERG (MULTIFOCAL ELECTRORETINOGRAPHY) The mfERG technique is a method of recording local electrophysiologic responses from different regions of the retina.
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