Progressive addition lenses are single-piece lenses that feature a smooth transition in curvature across the lens surface. The curvature gradually increases from the upper distance portion to the lower near portion. Unlike bifocal or trifocal lenses, progressive lenses offer a…
After completion of monocular subject refraction, binocular balancing is performed to balance the state of accommodation between two eyes. Binocular balancing aims to balance the state of accommodation of the two eyes. The procedure ensures that a person exerts the…
The prism dissociation and alternate occlusion test are only used when both eyes have similar monocular visual acuity. If monocular corrected visual acuity is not the same for both eyes, the bichrome prism dissociated method is used. Procedure of bichrome…
This differs from the vertical prism dissociation method, instead of using prisms in both eyes, eyes are dissociated using occlusion. A paddle occlude is used for occlusion of the eye (occluder which is used in the cover test) which allows…
The procedure makes use of prisms to break the fusion between two eyes. The vertical prisms of the same amount are used to maintain equal degradation of image quality which is caused by prism. Don’t use horizontal prisms, as a…
The Fan and block chart is similar to an astigmatism fan chart but additionally includes a block which contains an arrow at the center and two blocks of the line adjacent to the arrow which are perpendicular to one another.…
The astigmatism fan chart has line differences in 10 degrees intervals. Some charts have correcting cylinder axis marked in chart written at top of each spoke of line (Figure 1) and some charts just only represent the actual representation of…
It consists of a series of the number of lines of equal length from the center and pointing towards a number similar to the face of a clock. Gaps between two numbers are equal to 30 degrees. Before reading procedure…
Two of the most commonly used astigmatism chart are the Clock dial chart and the astigmatism fan chart. This test well controls accommodation as fogging is done prior and has an advantage over the Jackson cross cylinder where one of…
The Hirschberg test is a quick and easy objective method for the assessment of ocular alignment. It is also known as the corneal light reflex test as the observation is based on the judgment of the position of the corneal…
