Ophthalmoscope

An ophthalmoscope is used to examine the retina and vitreous. Ophthalmoscopy aids visualization of the inside of the back of the eye including the retina, optic disc, choroid and blood vessels. It is often part of a routine eye examination. A direct ophthalmoscope is used for viewing the central retina. It is hand-held and powered with a light source. The instrument has to be adjusted constantly to focus on different structures within the eye. The light can be intense and disturbing. An indirect ophthalmoscope aids in examining the entire retina. This instrument is attached to the doctor's head and allows a clear view of the retina with a special lens. The patient may feel uncomfortable due to the intense light and pressure from the instrument.

Ophthalmoscopy is useful in detecting any changes in the retina due to diseases such as eye disease, diabetes, arteriosclerosis, high blood pressure or macular degeneration. Cataracts and other eye problems can be detected with an ophthalmoscope.

The patient's eyes are dilated so as to allow a good view of the insides of the eye. Some patients develop allergic reaction, vomiting, nausea and dizziness. This test is conducted in a darkened room where the patient is asked to look ahead at a distant spot. The eyes must be held steady without blinking. The ophthalmoscopy procedure may take just about 5 - 10 minutes.

Tonometry

Tonometry test is a diagnostic test to measure the intraoccular pressure (IOP). When the tonometry test measures the pressure inside the eye, it can help in detecting glaucoma. Ensure that you take off your contact lenses. Do not wear tight clothing around the neck as it can lead to increased pressure inside the eye. Do not smoke a few hours prior to the tonometry test. The tonometry test is also conducted in cases of head or eye surgery and hyphema.

When the pressure builds up within the eye due to improper drainage, it can cause permanent damage to the ooptic nerve. Tonometry is done as part of routine eye examination to check for glaucoma. Anesthetic eye drops are used to numb the eye before using the tonometer. In the application method of testing intraoccular pressure, a paper stained with Fluorescein is placed to the side of the eye thereby staining the front of the eye. The tonometer is then brought close to the cornea for testing. Here the intraoccular pressure is measured by the amount of weight that is needed to flatten the cornea. This type of tonometry test can also be conducted with a pencil-like instrument, which will give instant digital measurement. The air puff method of conducting tonometry is a non-contact one where a puff of air is blown at your eye and change in the light reflected from the cornea is measured to arrive at the intraoccular pressure. This method is preferred for children and persons who have undergone LASIK surgery.

Slit Lamp Test

Slit lamp test is used to examine the eyes from a three dimensional view. Different parts of the eyes like the anterior and the posterior segments are viewed during the test. The front part of the eye including the clear, cornea (outer covering), the lens, iris, and the vitreous gel (front section of the gel-like fluid) in the middle of the eye are studied. The slit lamp is a low power microscope combined with a high intensity light source that is focused into a thin beam to shine. The binocular slit lamp provides a magnified view of the eye structures in detail. An additional hand-held lens is used to examine the retina.

Special lenses are placed in between the slit lamp and cornea to view the deeper structure of the eye which includes the retina, optic nerve and the drainage angle (area from where the fluid drains out of the eye). A camera attached to the slit lamp may be helpful in capturing pictures of the eye. To detect foreign bodies in the eye, a special dye (Fluorescein) is used. The eyes are dilated before the test is done so as to widen the pupil for examination.

Various methods are used to conduct the test namely observation by optical section, direct diffuse illumination, retro illumination, indirect illumination, etc.

Slit lamp test diagnosis

Slit lamp tests are used to identify eye problems at an early stage. The test is usually done:

• As a part of routine eye examination.
  
• To examine structures at the back of the eye like the retina and the optic nerve.
  
• Help detect glaucoma, macular degeneration, etc.
  
• To examine structures at the front of the eye.
  
• To detect cataract, conjunctivitis, injury to cornea, etc.
  
• To detect presence of foreign bodies in the eye.
  
• Monitoring injuries/bleeding from injuries, etc.
  
• Detect eye problems that may show up due to diabetes, rheumatoid arthritis
  

Slit Lamp Test Procedure

Slit lamp test is performed by an ophthalmologist or optometrist. The test takes about 5-10 minutes. The following steps are followed:

• Eyes are dilated to widen the pupil for examining the structure of the eye clearly.
  
• Anesthetic eye drops (to numb the eyes) are used in case of removing a foreign body.
  
• Patient is made to sit placing the chin and forehead against the bars on the slit lamp.
  
• The slit lamp is placed in front of the eyes in line with the doctor's eyes. The patient is asked to focus the eyes without blinking in the direction as requested by the doctor.
  
• A narrow beam of light is directed into the eye as the doctor examines through the microscope. A camera attached to the instrument may be used to capture images of different parts of the eyes.
  
• To check for ulcers, scratches or burns, the doctor may use a Fluorescein drop. This dye dissolves in the tears and coats the cornea thus covering the area of scratches, ulcer, etc. This will enable the doctor to examine the injury better.