Accommodation

Accommodation Training #

Description #

The accommodation test is tailored to automatically assess and enhance Monocular Accommodation Facility. For this test, patients should wear their distance correction and not be presbyopic.

Upon initiating the test, five Sloan-type letters, configured in a cross pattern with the central letter duplicated, are displayed. With the use of red/blue glasses or polarizing filters (for 3D displays), these letters are visible to only one eye, as specified in the screen’s upper-left corner. All letters are of identical size, which is denoted in the screen’s lower-right corner (in VA units).

A letter size around 0.6 Dec or smaller is advisable (considering the selected viewing distance, typically 40 or 50 cm), although this is contingent upon the display’s resolution capabilities, as some screens may not support displaying letters this small.

Before commencing the test, a positive lens is placed before one eye and a negative lens before the other (commonly -2.00 for the right eye and +2.00 for the left). This setup can be achieved using various methods, such as flipper lenses, the trial frame, or individual clip-on lens holders (illustrated in the image).

Tool Menu #

Activating the right tab unveils the tool menu, presenting options as follows:

Icon	Function	Keyboard Shortcut
	This function measures Monocular Accommodative Facility, advisable before beginning training for subsequent performance comparisons. It is also suitable for accommodation training.	A
	These buttons adjust the letters’ size, with the VA value refreshing in the lower right of the screen. Utilizing a VA near the patient’s threshold ensures precise accommodation. Note: Clicking the VA value or pressing “W” alters the expressed units of VA.	+ –
	This button alternates between letter types (fonts) in the sequence of Sloan, Symmetrical, British, Numbers, Landolt Cs, and Snellen Es.	F
	This icon allows changes which eye views the displayed letters.	I
	Randomizes the letters’ layout.	Z
	Resets the layout to its original configuration.	X
	Switches between red/blue and polarized views for compatibility with passive 3D screens.	D

Monocular Accommodative Facility #

To measure Monocular Accommodative Facility with the Vision Unit, apply the red/blue filters and assign each eye lenses of matching power: negative for the right, positive for the left. Commonly used are:

RE: -2.00 and LE: +2.00

Navigate to the menu on the right and select the Accommodation button (or press “A”). In the ensuing window, specify the lenses’ powers before each eye and the activity’s desired duration. For facility measurement, choose 1 minute; for training, select a longer span, between 3 and 5 minutes.

After pressing start, five letters are shown. Patients are instructed to strive for clarity through the lenses and filters. Initially, the letters, being blue, are solely visible to the right eye via colour filters. With a -2.00 lens in place, the patient must accommodate by 2 diopters for clear sight.

To confirm clarity, patients are asked to read the central letter and identify its duplicate among the four surrounding letters. Responses can be made using the keyboard arrows, mouse clicks, or direct keyboard input of the corresponding letter.

Following each correct response, a new set of five letters in an alternate colour is displayed, now visible only to the left eye (through the blue filter) when the letters turn red.

With a +2.00 lens in front of the LE, the patient is required to relax their accommodation by 2.00 diopters for clarity. The process of identifying the duplicated letter repeats as described.

Should an incorrect response occur, the program retries with the same eye, randomizing the letter arrangement each time. Attempts continue until successful, thereafter alternating to the other eye. This loop persists for the predetermined duration.

Upon completion, the results table showcases the lenses used, correct and incorrect response counts, and the success rate for each eye individually. Additionally, it displays the time each eye was engaged and calculates the cycles per minute.

Disparities in time spent per eye may indicate whether the patient finds it more challenging to achieve clarity with negative or positive lenses.

Defined as a cycle, the process of clearing with negative lenses, followed by positive ones, and reverting to negatives, measures how many cycles per minute the patient accomplishes. This metric serves as a baseline to assess post-training improvement.

Lastly, interchange the lenses between eyes and repeat the exercise. Typically, outcomes are consistent across both arrangements since both eyes usually accommodate simultaneously and to the same extent, rendering the specific eye with the positive or negative lens irrelevant.

Exercises for Accommodative Facility without Lenses #

This test also functions without lenses or filters to train Monocular Accommodative Facility, similar to printed Letter Cards (or Hart Charts).

Position the patient 3 meters from the screen with one eye covered, holding a mini wireless keyboard:

This arrangement facilitates accommodation and fixation shifts between screen letters and keyboard letters. Patients alternate their gaze between the distant screen for the central letter and the keyboard to press it, promoting near and far accommodation shifts while the program records correct and incorrect responses and time spent.

In such instances, neutral lenses may be specified in the test parameter window:

Additionally, this exercise is feasible in binocular vision with both eyes open.