Anterior Segment Examination Unit

The anterior segment is defined as all the former structures to vitreous: The cornea, the uvea (iris, ciliary body) and the lens.

The Cornea: is transparent and is situated in front of the other structures.

The ciliary body: is the responsible for the production of aqueus humor and the setting of lens (focused). Production increase of this liquid or its limited drainage, causes a pressure increase within the eye, causing damage to the optic nerve. This disease is known as glaucoma, and when the clinical treatment is not enough, it has a surgery treatment.

The Iris: is the structure, which gives color to the eye and controls the quantity of light to enter the eye.

The lens: it is a transparent lens situated behind the iris and in front of vitreous.

Bostan Diagnostic Eye Center provides different investigative tools used in diagnosis and follow-up of different anterior segment conditions:

    • Corneal OCT
    • Specular Microscopy
    • UBM
    • Corneal Pachymetry


Corneal pachymetry is the process of measuring the thickness of the cornea using contact methods. Corneal Pachymetry is particularly essential prior to a LASIK procedure for ensuring sufficient corneal thickness to prevent abnormal bulging out of the cornea, a side effect known as ectasia.

Conventional pachymeters are devices that display the thickness of the cornea, usually in micrometres, when the ultrasonic transducer touches the cornea. Newer generations of ultrasonic pachymeters work by way of Corneal Waveform.

Using this technology the user can capture an ultra-high definition echogram of the cornea. Pachymetry using the corneal waveform process allows the user to more accurately measure the corneal thickness, verify the reliability of the measurements that were obtained, superimpose corneal waveforms to monitor changes in a patient’s cornea over time, and measure structures within the cornea such as micro bubbles created during femto-second laser flap cuts.

Visual acuity assessment for preverbal infants

Our consultants are specialized in the evaluation of all visual functions for non-verbal and verbal children using the most up to date technology of “Smart System” software and screen.

For interested ophthalmologists we can also provide advice about optical, orthoptic or surgical management for strabismus patients.
BDEC also provide visual rehabilitation for children including amblyopia therapy and low vision aids.

These services in BDEC include:

  • Electrophysiolocial tests (ERG (pattern & flash), VEP (pattern, flash & sweep) and EOG)
  • Low vision aids
  • Full assessment for all visual functions:
  • Visual acuity:
    • Lea gratings (preferential looking)
    • Kay pictures (single & crowded optotypes)
    • Lea chart, E chart, Snellen chart and Landolt’s chart
  • Color vision:
    • Laminated HRR Pseudoisochromatic test
    • Ishihara test
  • Refraction and fundus:
    • Retinoscope and opthalmoscope
    • Portable autorefkeratometer
    • Retinoscopy racks
    • Portable autokeratometer
  • Stereopsis & Sensory function:
    • Worth’s 4 dot test for distance and  near
    • Bagolini glasses
    • Lang test
    • Randot test
    • TNO test
    • Frisby test
  • Strabismus assessment & measurement of deviation in all positions of gaze including horizontal, vertical and cyclic deviation using:
    • Hess screen examination
    • Prism bars
    • Awaya cyclodeviation booklet


How the test is performed:

You will sit in a chair. The eye will be numbed with anesthetizing drops. The ultrasound wand (transducer) is placed against the front surface of the eye.

There are two types of scans:

For the A-scan, you will be asked to look straight ahead.
If a B-scan is performed, you will be asked to look in multiple directions.

How to prepare for the test:

No special preparation is necessary for this test.

How the test will feel:

  • Your eye is numbed, so no discomfort is involved. You may be asked to look in a different directions to improve the ultrasound image or to view different areas of the eye.
  • A lubricant placed on the transducer may run on your cheek, but there will be no discomfort or pain. The test takes about 15 minutes.

Why the test is performed:

The ultrasound helps evaluate the farthest part of the eyeball when you have cataracts or other reasons that make it hard to look into your eye. The test may help diagnose retinal detachment or other disorders when the eye is not clear and the ophthalmologist can not use routine examining equipment. An A-scan ultrasound measures the eye for the proper power of a lens implant before cataract surgery.

What the risks are:

To avoid scratching the cornea, do not rub the anesthetized eye until the anesthetic wears off (about 15 minutes). There are no other risks.

Ultrasonic biomicroscopy

Ultrasound Biomicroscopy (UBM) is a new imaging technique that uses high frequency ultrasound to produce images of the eye at near microscopic resolution.

UBM gives clinicians higher-resolution digital images and video of the anterior segment of the eye behind the iris better than any other technology. This new capability is generating excitement among eyecare practitioners for its potential use in glaucoma and intra ocular lenses (IOL) patients and other common conditions and procedures.

Specular Microscopy

The corneal specular microscope is a reflected-light microscope that projects light onto the cornea and images the light reflected from an optical interface of the corneal tissue, most typically the interface between the corneal endothelium and the aqueous humor. Depending on the instrument used, the projected light can be in the form of a stationary slit, a moving slit, or a moving spot and the optical design can either be non-confocal or confocal. Although specular microscopes have been used primarily to evaluate the corneal endothelium, the corneal epithelium and stroma as well as the crystalline lens can also be visualized and evaluated.

Normal corneal endothelium as photographed by specular microscopy. A quasi-regular array of hexagonal cells all having nearly the same area is seen.

Optical Biometry

Biometry means the calculation of the intraocular lens power to be implanted in the eye after cataract extraction. Biometry can be performed by ultrasonic devices if the cataract is dense or by a non contact instrument using light waves to measure accurately the IOL power.

Ocular pathology & bacteriology

These tests are done in partnership with El Borg lab.

Pathological specimen from a mass excised from the eye lid, conjunctiva, iris or other parts of the globe is described by our ophthalmologists and interpreted after being processed by the lab technicians.

The bacteriological studies for conjunctival smears or corneal scrapings  in cases of resistant conjunctivitis or corneal ulcer are essential, to prescribe the appropriate treatment. The smear is taken under sterile conditions by our ophthalmologists

Neuro physiological unit

Electrophysiological tests are non-invasive tools indispensable in many diagnostic dilemmas.
Being objective and reproducible they have a considerable prognostic role.

The neurophysiology unit of Bostan Diagnostic Center includes tests such as: EMG, EEG, BAEP, SSEP, VEP, ERG, EOG
Indications & Clinical applications of Electromyography (EMG) & Nerve conduction studies (NCS)

  1. Myopathic Disorders
  2. Neuropathic Disorders
  3. Disorders of Neuromuscular Transmission
  4. Extraocular muscle tests for synergistic or antagonistic movements to diagnose Duane retraction syndrome or paralytic squint

Indications & Clinical applications of Electroencephalography (EEG)

  1. Epilepsy
  2. Syncope
  3. Vascular Lesions
  4. Chronic Headache Syndromes that fail to respond to medical
  5. Tumors
  6. Dementia
  7. Metabolic Disorders
  8. Head Trauma
  9. Altered states of consciousness

Indications & Clinical applications of Brainstem Auditory Evoked Potential (BAEP)

  1. Acoustic Neuroma
  2. Other Posterior Fossa Tumors
  3. Cerebrovascular Disease
  4. Demyelinating Disease
  5. Developmental Disorders
  6. Metabolic and Degenerative Disorders
  7. Anoxia
  8. Head Injury
  9. Cognitive Disorders

Indications & Clinical applications of Somatosensory Evoked Potential (SSEP)

  1. Disorders of Peripheral Nerves
  2. Plexus Lesions
  3. Thoracic Outlet Syndrome
  4. Cervical Spondylotic Radiculopathy and Myelopathy
  5. Radiculopathy
  6. Multiple Sclerosis
  7. Spinal Cord Dysfunction
  8. Brainstem Lesions
  9. Hemispheric and Thalamic Lesions

Indications & Clinical applications of Visual Evoked Potential (VEP)

  1. Maculopathies
  2. Disorders of Optic Nerve and Chiasma
  3. Retrochismatic Disorders

Indications & Clinical applications of Electroretinogram (ERG)

  1. Retinal Dystrophies
  2. Retinoschisis
  3. Vascular Disease
  4. Intraocular Foreign Bodies
  5. Retinal Detachment

Indications & Clinical applications of Electrooculogram (EOG)

  1. Detects Retinal Pigment Epithelium dysfunction.
  2. It is essential in the diagnosis whenever Best’s disease is suspected.

Prior booking is essential for neurophysiology tests. 

Low vision aids

When conventional spectacles can no longer help and surgery or medical treatment is not appropriate, or very prolonged, then it is time to consider low vision aids. These come in a bewildering array of strengths and designs. They range from simple hand-held lenses to electronic devices. Different ones are needed for different visual tasks.

The use of a low vision aid is dependent on many factors, the type of vision loss, the degree of loss, the patient’s light and glare needs, the ability of the patient to handle and operate the aid plus many other factors.

Your care should start with a low vision evaluation by our ophthalmologists who specialize in low vision rehabilitation. The low vision examination is not the same as the retinal or general eye examinations you might have experienced.

Doppler for carotid & ophthalmic artery circulation

A Doppler ultrasound test uses reflected sound waves to evaluate blood as it flows through a blood vessel. It helps doctors evaluate blood flow through the major arteries and veins
It may be used to detect blood flow in carotid arteries and veins, also for ophthalmic artery and vein. This test helps to diagnose defective blood flow in the eye that affects the optic nerve or retinal functions.

During Doppler ultrasound, a handheld instrument (transducer) is passed lightly over the eye globe. The transducer sends and receives sound waves that are amplified through a microphone. The sound waves bounce off solid objects, including blood cells. The movement of blood cells causes a change in pitch of the reflected sound waves (called the Doppler effect). If there is no blood flow, the pitch does not change. Information from the reflected sound waves can be processed by a computer to provide graphs or pictures that represent the flow of blood through the blood vessels. These graphs or pictures can be saved for future review or evaluation.



The nasolacrimal duct (sometimes called tear duct) carries tears from the lacrimal sac into the nasal cavity. Excess tears flow through nasolacrimal duct which opens in the nose. This is the reason the nose starts to run when a person is crying or has watery eyes from an allergy, and why one can sometimes taste eye drops

Obstruction of the nasolacrimal duct leads to the excess overflow of tears called epiphora.

In this condition an X-ray imaging using a dye that is injected through the small opening on the inner side of the lid margin (punctum) to diagnose the site and level of the obstruction, is needed to plan the surgery.

CT orbit

A computed tomography (CT) scan of the orbit is an imaging method that uses x-rays to create detailed pictures of the eye sockets (orbits) and eyes (globes).

How the Test is Performed:
A special dye, called contrast, may be injected into your hand or forearm before the test starts. Contrast can highlight specific areas inside the body, which creates a clearer image.

You will be asked to lie on your back a narrow table that slides into the center of the CT scanner. Only your head is positioned inside the CT scanner.

You may be allowed to rest your head on a pillow, but this must be done before the scan begins. It is very important that once your head is in place, you do not move it during the test. Movement causes blurred images.

Once inside the scanner, the machine’s x-ray beam rotates around you. (Modern “spiral” scanners can perform the exam in one continuous motion.)

Small detectors inside the scanner measure the amount of x-rays that make it through the part of the body being studied. A computer takes this information and uses it to create several individual images, called slices. These images can be stored, viewed on a monitor, or printed on film. Three-dimensional models of organs can be created by stacking the individual slices together.

Generally, complete scans take only a few minutes.

How to Prepare for the Test:
Remove dentures, any jewelry, and anything metal.
If contrast is used, you may be asked not to eat or drink anything for 4-6 hours before the test.
Some people have allergies to IV contrast and may need to take medications before their test in order to safely receive this substance.

How the Test Will Feel
Contrast given through an IV may cause a slight burning sensation, a metallic taste in the mouth, and a warm flushing of the body. These sensations are normal and usually go away within a few seconds.

Why the Test is Performed
This test is helpful for diagnosing diseases that affect the following areas:

  • Blood vessels
  • Eye muscles
  • Eyes
  • Nerves supplying the eyes (optic nerves)
  • Sinuses

An orbit CT scan may also be used to detect:

  • Abscess (infection) of the eye area
  • Hard-to-see fractures of the eye socket
  • Foreign object in the eye socket

Pentacam Topography

Corneal topography is a process for mapping the surface curvature of the cornea, similar to making a contour map of land. The cornea is a clear membrane that covers the front of the eye and is responsible for about 70 percent of the eye’s focusing power. To a large extent, the shape of the cornea determines the visual ability of an otherwise healthy eye. A perfect eye has an evenly rounded cornea, but if the cornea is too flat, too steep, or unevenly curved, less than perfect vision results.

The purpose of corneal topography is to produce a detailed description of the shape and power of the cornea. Using computerized imaging technology, the 3-dimensional map produced by the corneal topographer aids an ophthalmologist in the diagnosis, monitoring, and treatment of various visual conditions.

How does corneal topography work?

The corneal topographer is made up of a computer linked to a lighted bowl that contains a pattern of concentric rings. The patient is seated in front of the bowl with his or her head pressed against a bar while a series of data points are generated on a placido disk, which has been projected on the cornea. Computer software digitizes these data points to produce a printout of the corneal shape, using different colors to identify different elevations.
The procedure itself is painless and brief. It is a non-contact examination that photographs the surface of the eye using ordinary light. The greatest advantage of corneal topography is its ability to detect conditions invisible to most conventional testing.

Corneal OCT – Optical Coherence Tomography

Anterior segment OCT (Ocular Coherence Tomography) involves the measurement of a series of cross sections of the anterior segment of eye, including the cornea, iris, angle, and lens.


Assessment of diplopia through Hess screen

Hess chart is the test used to assess diplopia (squint). It shows the position of the non fixing-eye in all positions of gaze when the other eye is fixing.

The image can be separated in widely differing ways. The most usual way is to separate the image by means of fixation objects in complementary filter goggles in complementary colors (red & green).

The red filter reflects all lights and allows only for the transmission of the red light while the green filter allows only for the transmission of the green light.


Performing an examination:

  1. The patient will be asked to sit 50 cm in front of the screen so that its mid-point is situated in his main direction of gaze, that is the primary position of gaze.
  2. The patient wears red and green goggles with the green lens in front of the left eye.
  3. The room lights will be dimmed to a level were the patient cannot see the markings on the Hess screen through the goggles.
  4. The patient is asked to direct the light spot of the green laser pointer, which he guides himself using the hand he writes with, onto the red fixed point.
  5. When the fixation point changes the patient changes his direction of gaze and tries to target the fixed point again.

This is a completely non-invasive test and do not consist and potential side effect to the patients.

Retinal OCT – Optical Coherence Tomography

Optical Coherence Tomography, “OCT” for short. OCT is a non-invasive technology used for imaging the retina, the multi-layered sensory tissue lining the back of the eye. OCT is the first instrument to allow doctors to see cross-sectional images of the retina, is revolutionizing the early detection and treatment of eye conditions such as macular holes, pre-retinal membranes, macular swelling and even optic nerve damage.

Similar to CT scans of internal organs, OCT uses the optical backscattering of light to rapidly scan the eye and describe a pixel representation of the anatomic layers within the retina. Each of these ten important layers can be differentiated and their thickness can be measured.

Knowing the normal thickness of a healthy retinal layer, the ophthalmologist can then distinguish a multitude of retinal diseases and conditions.
In 2007, OCT was named one of the top 10 medical innovations expected to improve healthcare.

For certain conditions, such as age-related macular degeneration and cystoid macular edema, the 45 second OCT procedure is able to reduce or eliminate the need for fluorescein angiography for some patients.

Automated Perimetry

Your visual field refers to how much you can see around you, including objects in your peripheral (side) vision.

Visual field testing is used to monitor peripheral, or side, vision.

This test produces a map of your field of vision. Visual field tests help your ophthalmologist monitor any loss of vision and diagnose eye problems and disease.

How is Visual field test performed?

The test is performed with a large, bowl-shaped instrument called a perimeter. In order to test one eye at a time, one of your eyes is temporarily patched during the test. You will be seated and positioned comfortably in front of the perimeter and asked to look straight ahead at a fixed spot (the fixation target). The computer randomly flashes points of light around the bowl-shaped perimeter. When you see a light, press the indicator button. It is very important to always keep looking straight ahead. Do not move your eyes to look for the target; wait until it appears in your side vision. A delay in seeing a light does not necessarily mean your field of vision is damaged.

If you need to rest during the test, tell the technician and he or she will pause the test until you are ready to continue.

Your ophthalmologist will interpret the results of your test and discuss them with you.

Types of visual field tests:

There are two main testing methods:

  • Moving Targets. Lighted targets are moved from where you can’t see them (beyond your side vision) in towards the center of your vision until you do see them. As soon as the target appears in your field of vision, you press the indicator button.
  • Fixed Targets. Instead of targets moving into your field of vision, fixed targets suddenly appear in different areas on the screen. When the targets appear, you press the indicator button.

Why are these tests important?

Initially, visual field tests help your ophthalmologist diagnose problems with your eyes, optic nerve or brain, including:

  • loss of vision;
  • glaucoma;
  • disorders of your retina (layer of cells that lines the back of your eye);
  • other neurologic conditions including brain tumors, multiple sclerosis, and stroke.