Sankara Nethralaya
Sankara Nethralaya
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Our investigative facilities include an array of sophisticated equipment
Vitreo retinal service
Neuro Ophthalmology evaluation
Imaging Techniques
Biometry – DBR (A Scan)
The Visual Fields (Perimetry)
Corneal Topography
Specular Microscopy
Glaucoma Diagnosis

Glaucoma is a disease where there is a raise in the intra-ocular pressure, optic disc changes and an associated visual field loss.

Intra - ocular pressure measurement
Applanation Tonometry
Non Contact Tonometry
Pascal DCT
Perkins tonometer
Reichert Ocular response analyzer
Rebound tonometer
Anterior segment Imaging ; Visante AS-OCT (Zeiss)
Optic nerve evaluation by
Digital Fundus photography (Zeiss)
GDx VCC nerve analyzer (Zeiss)
HD Optical Coherence Tomography (Zeiss)
Heidelberg retinal tomogram
Ultrasound Biomicroscopy
Swept source OCT
Visual field testing by
Humphrey Visual field analyzer
Frequency Doubling Perimetry
Blue on yellow perimetry
Differential light sensitivity
Based on the above tests the type of glaucoma is diagnosed.
Lasers available:
ND YAG laser (Zeiss)
Argon Laser (Zeiss)
Diode Laser(Iridex)
Lumenis SLT/YAG integrated combo Laser (Selecta Duet)
Endoscopic Cyclophotocoaglation


Glaucoma is the second most blinding disease in the World. It is known as the "Silent thief of sight" as most of the types of glaucoma are asymptomatic

Vitreo retinal service
Ultrasound Biomicroscopy
Fundus fluorescein angiography
Ophthalmic photography
Electro diagnostic tests
Optical coherence Tomography (OCT)
Neuro Ophthalmology evaluation
Visual Psychophysics
Contrast Sensitivity
Color vision – FM 100 hue test
Potential acuity meter test
Imaging Techniques
Slit Lamp Photography
Fundus Photography
Fundus Angiography
Digital Biometry


To determine the power of the intraocular lens (IOL) to be implanted in patients undergoing cataract surgery.
It involves measurement of the axial length (the distance between the anterior and posterior part of the eye) and the corneal curvature (curvature of the black portion of the eye ball) of the eye.
Test is done in both the eyes.
Generally corneal curvature is measured first using an instrument called keratometer.
The patient needs to fixate steadily centrally as instructed by the examiner and the readings are obtained. he eye.
This is a non contact procedure.
A Scan:
Axial length is measured using ultrasound A scan
A drop of local anesthesia is instilled on to the eye
The patient is asked to fixate centrally
Examiner gently places a probe on the eye
Ultrasound waves are sent to the eye through the probe
The axial length readings are displayed on to a screen.
The examiner selects the appropriate reading
IOL power calculations are then done accordingly
Axial length measurements are also done in few other cases like
High myopia (high minus powered glasses)
Anisometropia (difference in spectacle power between both the eyes)

1. Full field Electroretinography (ERG): Test which measures the electrical responses of various cell types in the retina, including the photoreceptors (rods and cones), inner retinal cells (bipolar and amacrine cells). Used to diagnose various retinal degenerations.

  Retinitis pigmentosa and their variants
  X-linked juvenile retinoschisis
  Heredo-macular degenerations
  Retinal Vascular occlusions
  Intraocular Foreign Body
2. Multifocal Electroretinography (mfERG): Multifocal electroretinography (mfERG) is a valuable technique in assessing macular function in retinal disease objectively. It is used to record separate responses for different retinal locations. It is also used in the detection of
  Macular dystrophies
  Macular hole
  X-linked retinoschisis
  Drug toxicity
  Multifocal choroditis
  White-dot syndrome
3. Electrooculogram (EOG): This is used to assess the function of the outer retina and Retinal Pigment Epithelium (RPE). EOG is used to confirm
  Best disease
  Suspected drug toxicities
4. Pattern Electroretinogram (PERG): This test provides information about central macular and retinal ganglion cell layer. It is also used to differentiate vision loss due to retinal or optic nerve diseases. PERG is used in evaluating
  Glaucoma and ocular hypertension,
  Optic neuritis other optic neuropathies,
5. Visually Evoked Responses (VEP): The VEP is a test to detect problems with the optic nerve and lesions in the anterior part of our visual pathway. VEP tests are used to evaluate
  Optic neuritis,
  Compressive Optic neuropathy,
  Toxic amblyopia
  Cortical Blindness
  Demyelenating diseases such as multiple sclerosis.
  Unexplained visual loss
6. Multifocal Visually Evoked Responses (mfVEP): This test allows for topographical assessment of visual field. In this test multiple individual VEP responses are recorded simultaneously from 60 or so regions of the central 20 to 25° radius of the visual field. This is also known as objective visual field perimetry. Indications are
  Diagnosing and Following of Optic Neuritis/Multiple Sclerosis
  Unexplained visual loss
  Detecting and following of Glaucomatous damage
  Confirming unreliable or questionable fields
The Visual Field

What is Visual Field?

Visual field is the degree of side or peripheral vision a person can perceive when looking straight at an object.

How is the Visual field of a patient measured?

Perimeter is the instrument used to measure the visual fields of a patient. There are various types of perimeters to quantify the visual fields.

What instrument do we use at our hospital?

Perimetry is performed in Sankara Nethralaya using the AUTOMATED HUMPHREY FIELD ANALYZER (HFA II and HFA i-SERIES)

Why is Visual field testing important?

The purpose of visual field testing or perimetry is to provide information critical to:

Diagnosing ocular diseases, especially Glaucoma
Evaluating neurological diseases
Monitoring the progress of ocular and neurological diseases.
How is the visual fields testing done?
Mostly done for one eye at a time followed by the other eye.
Sometimes visual field testing is done for both the eyes simultaneously which is known as Binocular Visual field testing.
A perimetrist will assist the patient by clearly giving the instruction on how to perform the testing.
Patient’s understanding of the test and cooperation is very important to get a reliable report which in turn will assist the Ophthalmologist in the diagnosis and management of the disease.
Hence visual field plays a major role in early detection and treatment of the disease and also in evaluating the efficacy of the therapy used to control the disease process.
Normal fields
Inferior arcuate defect in glaucoma case
Superior arcuate defect in glaucoma case
Biarcuate defect in glaucoma case
Full Field 120 in a retinal case depicting central scotoma
Neuro case of Left Homonymous Hemianopia.
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