Frontofokometer (focal power meter)
Frontofokometer is an instrument used to check the prescription of glasses or spectacles. Many lens gauges can also check the power of contact lenses by adding a special lens holder. The values obtained from a frontofokometerare the values stated on the eyeglass prescription: sphere, cylinder, axis, addition and in some cases prism.
An autorefractor is an instrument that helps assess refraction. This is an alternative method to determine the refractive error. The procedure is called refractometry or optometry. The autorefractors can be of different types depending on the underlying principle. The various indications to perform optometry are myopia, hyperopia, astigmatism, presbyopia, glasses prescription and contact lens prescription, which serve as a starting point for subjective refraction for ophthalmologists and optometrists in children’s refraction and people with a disability who need glasses.
Medical Ophthalmological Examination
Examination with the slit lamp
A slit lamp is the most common ophthalmic device used by ophthalmologists in daily clinical practice. It is an indispensable tool in the ophthalmologist. The slit lamp not only provides a magnified view of the intraocular structures (anterior and posterior segments), but also helps in the qualitative and quantitative analysis of various parameters such as corneal endothelial cell count, corneal thickness, anterior chamber cells, anterior chamber depth, pupil size, cataract degree, etc.
Tonometry (measurement of intraocular pressure)
The tonometer measures the intraocular pressure, which differs from the blood pressure, which is measured on the arm
A fundoscopy is an instrument that uses a collimated beam of laser light to image the structures of the eye, particularly the retina and optic nerve head. Unlike indirect ophthalmoscopes, fundoscopy drastically reduced the amount of light needed to image the posterior segment of the eye, improving patient comfort during the procedure.
Skiascopy (shadow test)
The eyes are examined after the pupil has been dilated with eye drops. This examination allows an objective determination of visual acuity. It is particularly appropriate for preschool children and those who frequently suffer from headaches, for patients who are squinting or who are about to undergo surgery to correct myopia, and for whom an objective measurement of refraction is therefore essential. You will have three drops in each eye, which will take 30 minutes to work before the examination. Infants will receive drops in both eyes for three days prior to the exam. Retinoscopy is a very helpful examination method for strabismus.
Topographical description of the cornea
Corneal topography is an integral diagnostic tool in the arsenal of corneal, cataract, and refractive surgeons. This activity highlights the development of corneal topographical mapping and the methods used to assess the anterior and posterior surfaces of the cornea. The radius of curvature of the central part of the anterior surface of the cornea is measured by the magnitude of the reflection of an image projected by the keratometer.
Teardrop or Schirmer test
The Schirmer test determines whether the eye produces enough tears to keep it moist. This test is used when a person has very dry eyes or excessive tearing of the eyes. It does not pose any risk. A negative test result (more than 10 mm moisture on the filter paper in 5 minutes) is normal. Both eyes usually shed the same amount of tears.
Break up time test
Breakup Time (BUT) is a clinical test used to assess dry eye. To measure BUT, fluorescein is instilled into the patient’s tear film and the patient is asked not to blink while the tear film is observed under a broad beam of cobalt blue light. The BUT is recorded as the number of seconds that elapse between the last blink and the appearance of the first dry spot in the tear film, as seen in this history of these slit lamp photos over time. A BUT under 10 seconds is considered abnormal. This patient also has punctate epithelial erosions (PEE) that stain positively with fluorescein, another sign of dry ocular surface.
An exophthalmometer is an instrument used to measure the degree of forward displacement of the eye in exophthalmos.
Color Vision Test
The color vision test is an examination of abnormalities in the perception of colors such as color blindness
Corneal pachymetry measures the thickness of the cornea. A pachymeter is a medical device used to measure the thickness of the cornea of the eye. It is used to perform corneal pachymetry prior to refractive surgery, for keratoconus screening, LRI surgeries and, among others, to screen patients suspected of developing glaucoma.
Visual Field Examination
A visual field test can determine if you have blind spots (called scotomas) in your vision and where they are located. The size and shape of a scotoma can show how an eye disease or brain disorder is affecting your vision. For example, if you have glaucoma, this test will help identify possible side (peripheral) vision loss due to the disease.
Eye doctors also use visual field tests to assess how vision may be affected by eyelid problems such as ptosis and droopy eyelids.
Coherence Tomography (OCT)
Coherence tomography (OCT) is a non-invasive imaging technique. OCT uses light waves to take cross-sectional images of your retina.
With OCT we can see each of the characteristic layers of the retina. This allows the thickness of the retina to be mapped and measured. These measurements help with the diagnosis. They also provide treatment advice for glaucoma and diseases of the retina. These retinal diseases include age-related macular degeneration (AMD) and diabetic eye diseases.
During an OCT exam, dilating eye drops may or may not be put in your eyes. These drops dilate your pupil and make it easier to examine the retina.
You sit in front of the OCT machine and put your head on a support. The device then scans your eye without touching it. Scanning takes about 5 to 10 minutes.
Eye biometrics is a test that measures the dimensions of the eyeball: the axial length (distance between the front and back of the eye) and the depth of the anterior chamber (part between the cornea and the iris and lens). It is also used to measure the thickness, curvature and diameter of the cornea.
B-scan Ultrasound Method
B-scan is a diagnostic imaging tool used when vision of the fundus or posterior segment is obstructed. The posterior segment is the back two-thirds of the eye and consists of the vitreous humor, retina, optic nerve, and choroid. If the posterior segment of the eye is difficult for the ophthalmologist to see due to cataract, vitreous hemorrhage, and/or retinal tear/detachment, a B-scan may be ordered to better assess the fundus.
There are two main types of retinal angiography. The most common and useful is fluorescein angiography. Indocyanine green angiography is used in special circumstances or when the patient is allergic to fluorescein.
Fluorescein angiography, a clinical test to examine blood flow at the back of the eye, helps diagnose retinal disorders associated with diabetes, age-related macular degeneration, and other eye abnormalities. The test can also help track the progress of a disease and monitor its treatment. It can be repeated multiple times without harm to the eye or body.
Indocyanine Green Angiography (ICG)
ICG angiography is a clinical test used to detect abnormal blood vessels in the choroid, the layer of blood vessels beneath the retina. Typically associated with macular degeneration, these abnormal blood vessels can cause bleeding, scarring, and vision loss. If blood vessels can be constricted by laser surgery, vision loss can be stabilized or improved.
Retinometry is a method of measuring sharp eyes using a retinometer to determine the potential for sharp vision. Retinometer is a tool that uses the principle of interference fringes to assess the patient’s sharp vision through a cloudy lens. In a retinometer, a light source is split into two beams, which then enter the area of the lens that is least opaque, creating an interference grid on the retina. The grid can have a vertical, horizontal or oblique meridian orientation
Electrophysiological tests check how well this optic nerve pathway sends the electrical signals needed for vision. These tests measure the electrical activity that occurs in your eye when you look at something.
Electrophysiology includes various tests that measure how well the retina is functioning. It can help to check for diseases of the retina. The tests can also help diagnose and evaluate different types of vision and health problems.