Phoropters

Modern Phoropters or refractors are an alternative to trial

lens set. All the lenses in the phoropters are inbuilt with the help

of motors. There are basically two types of phoropters—Manual

and Automatic. Two spherical lens assemblies and two cylinder

lens assemblies are housed in the phoropter for each eye.

Cylinder axis is altered by turning a knob for each eye that rotates

the axis through meridian from 0–180°. Two cross cylinders, two

rotary prisms, pinhole, stenopaic slit, occluders, red lens and

polarizing analyzer are also included on accessory post. The

patient is asked to be seated behind the phoropter. Horizontal

and vertical position of the lens apertures are determined by

the mechanical arm adjustment suspending the phoropter. The

adjustment knob for IPD is used to adjust the geometric centers of

apertures before the eyes. Pantoscopic tilt can be incorporated by

adjustment of the swing connection between the phoropter and

the mechanical arm. The light mounting provides illumination

of the near test card. Newer generation phoropters also provide

additional feature to tilt during the course of reading to ensure

natural reading posture. The only drawback of phoropter is the

eyes of the patient is hidden behind the phoropter which means

the practitioner cannot see patient’s reactions and operational

flexibility is less as it is fixed at one place. It is difficult to have

eccentric viewing which may be a reason why it is not suitable for

visually impaired patient. However, there are certain advantages

of the phoropter. They can also measure phoria (natural resting

position of the eyes), accommodative amplitudes, horizontal

and vertical vergences, and many more.