L7 Flashcards
(11 cards)
What does retinoscopy in astigmatic eyes reveal?
An astigmatic eye displays two different refractive powers in two principal meridians, perpendicular to each other. Each principal meridian must be identified and corrected.
What is the process for correcting astigmatism during retinoscopy?
Determine the principal axis by aligning the ret reflex with the facial light. The second principal meridian is 90° to the first. Decide which meridian to correct first. Correct the slowest with or fastest against with a sphere. Leave the sphere in place. Assess the perpendicular meridian (should show an against movement). Use a negative cylinder to correct this meridian. Refine the axis.
How should results be recorded in power diagrams?
Note the power meridian, not the axis meridian (which is 90° to the power meridian).
What is the importance of the term ‘along’ in power cross notation?
‘Along’ refers to the power meridian, not the axis meridian.
What is the practical importance of the speed of the retinoscopy reflex?
An experienced practitioner can estimate the refractive error by the direction and speed of the reflex. Lower refractive errors produce a faster reflex; higher errors produce a slower reflex.
What is the relationship between the direction of retinoscopy movement and the axis?
The direction of ret movement is perpendicular to the axis; if the ret is swept up/down along 90°, the cylinder needs to be placed along 180°.
How do you confirm the cylinder axis?
Lindner’s method: sweep the ret at +45º and -45º to the cylinder axis. If the axis is correct, the reflex should be equal on both sides; if not, move the axis towards the meridian showing with movement.
What are some other methods of retinoscopy?
Barrett’s method: for practitioners unable to do ret accurately with both eyes or in domiciliary situations.
Mohindra’s technique: for infants/young children without cycloplegics; performed in a dark room, working distance 50cm, result compensated by -1.25D.
Cycloplegic refraction: uses cycloplegia to control accommodation, allowing accurate measurement of refractive error.
What is dynamic retinoscopy?
A technique to investigate the accommodative state of the eye in near vision; patient fixates on a near target, and the examiner neutralizes the ret reflex.
What is concave mirror retinoscopy?
Created by changing the distance between the lens and light source; in concave mirror ret, the immediate source is in front of the mirror. Reflex movements are opposite to those seen with plane mirror retinoscopy.
What are some common factors and problems in retinoscopy?
Media irregularities (e.g., keratoconus), corneal opacities, small pupils, poor fixation, unsteady patient, high refractive errors, and irregular astigmatism can all affect the quality of the reflex and accuracy of results.
