Choosing the Right Ophthalmic Examination Equipment

There are different ophthalmological examination devices that can be divided into three main categories: those intended for the measurement of ocular parameters, those dedicated to the analysis of visual acuity and those reserved for the examination of the eye itself.

• Measurement of ocular parameters:
  • The tonometer is used to measure intraocular pressure. To do so, it creates contact with the cornea (most often by sending a burst of air) and measures the reaction time. Abnormal eye pressure, for example, is one of the symptoms of glaucoma.
  • The pachymeter is used to measure the thickness of the cornea.
  • The ophthalmic biometer is used to measure different segments of the eye such as its axial length for example (the length between the apex of the cornea and the foveal retina).
  • The automatic refractometer/automatic keratometer is used to test the refraction of light by the patient’s visual system in order to detect possible refractive errors and calculate the necessary correction index. It is also used to measure the curvature of the anterior surface of the cornea in order to adapt contact lenses if necessary.

• Visual acuity tests:
  • An ophthalmic phoropter or refractor allows you to perform an eye test with lenses of different indexes.
  • An ophthalmic perimeter measures a patient’s visual field.

• Eye examinations: 
  • The ophthalmoscope is a small hand-held tool that projects a beam of light to observe the interior of the eye and its components: cornea, lens, vitreous body, retina, optic nerve and ophthalmic vascular system. 
  • The OCT ophthalmoscope (or simply OCT) is used to take non-invasive images of the eye by section, with the option of reconstruction. The OCT ophthalmoscope uses a principle similar to scanners, except that infrared radiation is used.
  • The slit lamp consists of a lamp and a binocular microscope. It allows a direct, natural, in-depth and three-dimensional visualization of the structure of the eye and its tissue, from the anterior segment (in front of the lens) to the posterior segment (behind the lens).
  • The retinal camera can take a photograph of the eye fundus in order to detect possible retinal pathologies of the macula and the optic nerve head.
  • The specular microscope allows you to visualize and count the cells of the corneal endothelium (a single layer of cells that covers the posterior surface of the cornea).
  • The corneal topographer is used to create a three-dimensional map of the surface curvature of the corneal for refractive corneal surgery, for example for myopia, or for screening for keratoconus in order to determine the centering of the focal point on the fovea.

Nidek OCT ophthalmoscope

The basic machines needed for an ophthalmology practice are:

• Automatic refractometer
• Ophthalmic refractor
• Tonometer
• OCT ophthalmoscope
• Slit lamp

All these devices together amount to an investment of close to 250,000 euros. Other machines can also be acquired if necessary, but they are less essential and can sometimes double the investment. These include:

• Corneal topographer
• Specular microscope
• Angiograph for retina examination
• Various lasers, in particular the laser for myopia surgery, which requires a very significant investment (around one million euros).

Tomey Corporation autorefractor-keratometer

There are several essential criteria for choosing an ophthalmic refractor or phoropter, including the actuation of the device, its measurement range, the presence of filters, etc. Here is a list of the main criteria:

• Manuel or digital
• Available measuring range
• Choice of available auxiliary lenses
• Presence of filters (red/green, polarizing, etc.)
• Used or new

Advantages of a digital phoropter: 

• It can be used to link the device to a digital data storage platform 
• It can switch to manual phoropter mode at any time.

Disadvantages of a digital phoropter: 

• A digital device takes time to turn on 
• Electric motors can sometimes be noisy

Essilor Instruments digital ophthalmic phoropter

The tonometer is an essential device for ophthalmologic consultations. Several criteria allow you to choose the best tonometer, such as the ergonomics of the device, the option of performing combined examinations or the type of tonometry you want to perform.

• Ergonomy of the device:
  • Portable or tabletop tonometer
  • Tonometer attached to a slit lamp

• Combined examinations: a tonometer sometimes offers the option of performing combined examinations such as tono-pachymeter, auto-ref/ker + tono-pachymeter, etc.

• Type of tonometry performed:
  • Goldmann tonometry (applanation tonometry)
  • Schiotz tonometry (indentation tonometry)
  • Non-contact tonometry (air tonometry)

Keeler portable non-contact tonometer

To choose a slit lamp, it is important to focus on the quality of the optics, the power of the light and the mechanical stability. Here is a list of the main selection criteria:

• Quality of the optics: the quality of the optical system will largely determine the quality of the examination results for which the slit lamp is used. This is essential for accurate diagnosis and safe treatment of the patient.
• Type and power of lighting: newer LED lighting systems create a precise slot with even, powerful illumination.
• Reliable and stable mechanics: good mechanics allow all movements to be performed smoothly and effortlessly, without twisting the wrists or fingers. Good mechanics also ensure a long service life for the slit lamp.
• Maximum zoom available: the zoom provides excellent diagnostic features especially when used with the video function.
• Video function (available or not)
• Portable or tabletop lamp
• Available accessories:
  • Video adapters
  • Beam splitters
  • Contrast enhancement filters, etc.

Haag-Streit slit lamp