7. Accommodation & vergence assessment - Part 1

[Audio] Orbit Eye Center for Pediatrics & Oculoplasty.

[Audio] ACCOMMODATION & VERGENCE ASSESSMENT Part: 1.

[Audio] Assessment of Accommodation Assessment of Vergence Multiple Choice Questions References.

[Audio] Assessment of Accommodation. Assessment of Accommodation.

[Audio] Introduction Accommodation is a critical visual function that allows the eyes to maintain clear and sharp vision at various distances. This process involves the adjustment of the crystalline lens in the eye to focus light from near objects onto the retina, ensuring visual clarity. At is particularly important in daily activities such as reading, using digital devices, and performing close-up tasks. Accommodative function can be compromised in various conditions, leading to symptoms like blurred vision, eye strain, headaches, and difficulties in maintaining focus during prolonged near work. These symptoms, collectively referred to as asthenopia, often become more pronounced by the end of the day and may be indicative of underlying accommodative dysfunctions..

[Audio] Given the increasing emphasis on near vision tasks in the modern world, from reading to using smartphones, tablets, and computers, it is crucial to test for accommodative dysfunctions. The assessment of accommodation should be a routine part of a comprehensive eye examination. This includes a baseline cycloplegic refraction, especially in children, to quantify significant refractive errors that could impact accommodation. Moreover, accommodative dysfunctions often coexist with binocular vision issues, as both accommodation and vergence are interrelated through an interactive negative feedback loop. Therefore, evaluating accommodation provides valuable insights into the eye's focusing mechanism and helps in the diagnosis, management, and treatment of various visual disorders. Ensuring optimal accommodative function is essential for maintaining clear and comfortable vision in all visual tasks..

[Audio] Causes of Accommodation In healthy children, accommodation disorders are linked to convergence disorders, emotional stress, and uncorrected refractive errors, particularly hyperopia (Choruses et al., 1988). Ocular conditions such as inflammation and sclerosis of the crystalline lens can lead to accommodation disorders. Neurological conditions, including head trauma, cranial nerve III palsy, and encephalitis, as well as certain medications, can impair accommodation. Systemic conditions like myasthenia gravis, diabetes, hypertension, Guillain-Barré syndrome, tuberculosis, endocrine disorders, and syphilis are also associated with accommodation disorders (Cooper and Lamoriello, 1988; Derespina's et al., 1989; Master et al., 2016; Moss et al., 1987)..

[Audio] Eye Structures and Accommodation Process The eye structures involved in accommodation include the crystalline lens, ciliary muscle, and zonule fibers, which connect the lens to the ciliary muscle. Optical accommodation helps keep an object in focus on the retina as the distance between the object and the eye changes. When viewing a distant object, light rays are nearly parallel, and no accommodation is needed to focus the image on the retina. In the unaccommodated state, the eye is relaxed, with the ciliary muscles relaxed, zonule fibers taut, and the lens less convex. When focusing on a near object, light rays diverge, requiring accommodation to bring the object into focus on the retina. Accommodation is achieved by increasing the convexity of the crystalline lens, enhancing its refractive power. This increase in convexity occurs as the ciliary muscle contracts, causing the zonule fibers to relax and the lens to become more convex..

[Audio] Three Components of Accommodation Tested Clinically Amplitude of Accommodation: Amplitude of accommodation refers to the maximum refractive power the eye can generate at a given distance. A reduced amplitude is termed Accommodative Insufficiency, where the patient struggles to stimulate accommodation. Ill-Sustained Accommodation is a subtype where the symptoms of accommodative insufficiency worsen over time, especially with prolonged near work. 2. Accuracy of Accommodation: Accuracy of accommodation is the measured lag or lead in the eye's response to a near stimulus. The normal lag of accommodation in school-age children ranges from +0.25D to +0.75D. Accommodative Excess occurs when the accommodative response exceeds the required stimulus. Accommodative Spasm is a more severe form of this condition. 3. Facility of Accommodation: Facility of accommodation is the eye's ability to alternately stimulate and relax focus in response to changing stimuli. Accommodative Infacility is the condition where the eye struggles with quickly and accurately shifting focus, which is crucial for tasks like switching focus from the board to a notebook and vice-versa..

[Audio] Assessment of accommodation includes Assessment of NPA and amplitude of accommodation Assessment of accommodative response Assessment of dynamics of accommodation Push-Up Method determine the NPA with RAF rule Minus Lens Method Monocular estimation method (MEM) Nott retinoscopy accommodative facility.

[Audio] ACCOMMODATIVE AMPLITUDE TESTING There are three clinical tests to measure accommodative amplitude: Push-Up Method RAF Rule (Royal Air Force Rule) Minus Lens Method.

[Audio] Push-Up Method Equipment 1. Near target with 20/20 letters or symbols 2. Ruler (cm) 3. Eye patch or occluder.

[Audio] Procedure • Perform the test monocularly. • Use a patch to cover the patient’s left eye. • Hold a target with 20/20* letters or symbols at 40 cm directly in front of the patient’s unoccluded eye. (If the patients near visual acuity is worse than 20/20, use a target that is two lines larger than the best acuity.) • Move the target towards the patient . • Instruct the patient to keep the target clear and to report when the target first starts to blur. • When the patient reports sustained blur, stop moving the target and measure the distance from the target to the patient’s lateral canthus. • (If the patient is wearing spectacles, measure the distance from the target to the patient’s spectacle plane.) • The maximal amplitude of accommodation is the calculated inverse of the measured distance in meters and expressed in diopters • Transfer the occluder or patch to the right eye. Repeat Steps 1-3 for the other eye.

[Audio] To determine the NPA with RAF rule: RAF Rule (Royal Air Force Rule) The RAF (Royal Air Force) Rule is a simple and practical instrument used to measure the near point of accommodation (NPA) Procedure Place the cheek rest of the RAF Rule on the patient's inferior orbital margin (just below the eye). The instrument should be slightly depressed at a 45-degree angle to align properly with the patient's line of sight. Make sure the patient is wearing their full refractive correction (glasses or contact lenses). Instruct the patient to focus on a row of letters, typically one or two lines better than their near visual acuity, displayed on the target. Start by measuring each eye separately. After the monocular measurements, assess both eyes together. Direct the patient's attention to the chosen row of letters and instruct them to "keep the letters clear.“ Slowly move the target towards the patient at a constant rate of 1 to 2 cm per second. Ask the patient to inform you the moment the letters appear blurred..

[Audio] Recording the Results: The NPA is measured in centimeters using the scale on one side of the RAF Rule. The amplitude of accommodation, measured in diopters (D), can be read directly from the dioptric markings on the other side of the bar. The third side of the bar shows the age corresponding to the measured amplitude of accommodation. In young adults, the amplitude of accommodation is typically around 10-12 diopters. As a person ages, the amplitude of accommodation decreases. By age 40, the amplitude usually drops to about 4.0 diopters. The decline in amplitude of accommodation continues with advancing age. Example: If a patient reports that the letters become blurred at 25 cm, the dioptric markings on the RAF Rule will indicate an amplitude of accommodation of +4.0 D, which corresponds to the expected amplitude for a 40-year-old..

[Audio] Minus Lens Test for Accommodative Amplitude Equipment Near point rod Eye patch Minus lenses Near Point of Accommodation (Minus Lens Method) The test is done both monocularly and binocularly with the habitual correction. The near point visual acuity chart should be well illuminated and is kept at a standard distance of 40 cm. Direct the patient’s attention to a row of letters one or two lines better than his near visual acuity. Instruct the patient to ‘keep the letters clear’. Add minus lenses in 0.25D steps and ask the patient to report when the letters become blurred and remain blurry (first sustained blur). The minus lenses with which the patient reports sustained blur is noted down. for the test distance of 40 cm, the accommodative demand value of 2.50 diopter is added to this value. The resulting dioptric value represents the patient’s amplitude of accommodation(AA). For e.g., if sustained blur is reported at -4.00 diopter, the amplitude of accommodation is 6.50 diopter. Due to the minification observed with minus lenses, minus-lens testing tends to under-estimate accommodation amplitudes. To compensate for this, Export and Which suggested testing at 33 cm, but use only 2.50 D instead of 3D to compensate for the working distance..

[Audio] Norms for Accommodative Amplitude The two most commonly used system for obtaining the excepted amplitude of accommodation are Hofstetter's formula. Donders table.

[Audio] Hofstetter’s formulas for calculating amplitudes of accommodation Below table provides Hofstetter’s formulas for calculating minimal, average, and maximal amplitudes of accommodation based on age in years. Minimal amplitudes of accommodation 15 D-1/4(age) Average amplitudes of accommodation 18.50 D -1/3(age) Maximal amplitudes of accommodation 25 D-1/4(age).

[Audio] Age-expected amplitude of accommodation for age 5 through 18 years Below table provides the average amplitudes of accommodation for 5 through 18 years of age. Age-Expected Amplitude of Accommodation Avg amplitude of accommodation = 18.5 D -1/3(age) AGE (yr) AMPLITUDE (D) AGE (yr) AMPLITUDE (D) 5 16.8 12 14.5 6 16.5 13 14.2 7 16.2 14 13.8 8 15.8 15 13.5 9 15.5 16 13.2 10 15.2 17 12.8 11 14.8 18 12.5.

[Audio] Age Amplitude of accommodation 10 14.00 15 12.00 20 10.00 25 8.50 30 7.00 35 5.50 40 5.00 45 3.50 50 2.50 55 1.75 60 1.00 65 0.50 70 0.25 75 0.00 Donders table Donders table for age referenced amplitude of accommodation ..

[Audio] Assessment of Accommodative Response Accommodative response measures the accuracy of a patient’s accommodative system when viewing a target at near. The response can be a LAG (accommodative response (AA) is less than the accommodative stimulus in a given distance) or a LEAD(accommodative response (AA) is more than the accommodative stimulus in a given distance ). A lead of accommodation is a key sign of accommodative excess, which is characterized by excessive near focusing; in more severe cases, such as accommodative spasm, accommodation is maintained even without a stimulus or is excessively strong in response to a near stimulus. Tests of Accommodative Response Two methods are performed objectively: Monocular Estimate Method (MEM) retinoscopy and Nott retinoscopy..

[Audio] Monocular Estimated Method (MEM) Retinoscopy Equipment 1. Retinoscope 2. Age-appropriate accommodative target 3. Plus, and minus power lenses Procedure The test is performed under binocular viewing conditions At is a dynamic retinoscopy technique involves the use of a retinoscope with magnetically attached cards Cards have a central aperture for alignment with the subject’s visual axis. Targets on cards include printed words or pictures in various sizes ranging from (6/120 to 6/9). Performed in normal room illumination with the examiner positioned 40 cm away from the patient at eye level. Patient wears appropriate spectacle correction or trial frame with subjective refraction correction Examiner observes motion in the horizontal meridian while the patient reads words out loud. Plus, lenses are used for "with" motion and minus lenses for "against" motion, applied briefly to minimize accommodation impact. Test is performed in one meridian only, as the other meridian is corrected during subjective refraction. Neutralize the reflex with appropriate lenses and note the power of the lens that achieves neutrality..

[Audio] MEM Retinoscopy Interpretation Neutral to Low MEM (0.25D to 0.75D): Reflex: Neutral or slight "with" movement. Interpretation: Normal accommodative response; accommodation matches the target distance. Very Low MEM (Less than 0.25D): Reflex: "with" movement. Interpretation: lag of accommodation. Associated Conditions: Near esophoria, convergence excess, accommodative insufficiency, under-corrected hyperopia, over-corrected myopia, presbyopia. High MEM (More than 0.75D): Reflex: "Against" movement. Interpretation: Lead of accommodation. Associated Conditions: Near exophoria, convergence insufficiency, accommodative excess, spasm of accommodation, under-corrected myopia, over-corrected hyperopia. Lens Power Interpretation Plus Lens Power: Indicates lag of accommodation; additional plus power needed for neutrality, reflecting under-accommodation. Minus Lens Power: Indicates lead of accommodation; minus lenses needed for neutrality, reflecting over-accommodation..

[Audio] Nott Retinoscopy Nott retinoscopy is similar to MEM, but neutralization is achieved by adjusting the distance between the retinoscope and the fixation card instead of using additional lenses. Equipment 1. Retinoscope 2. Age-appropriate accommodative target 3. Ruler (cm) Procedure A fixation card (typically 6/6 in size) is positioned 40 cm away from the patient’s eyes, and the patient views the target binocularly with their subjective correction. The examiner performs retinoscopy in the horizontal meridian and adjusts the distance based on the observed reflex movement. If "with" movement is observed, the retinoscope is moved away from the fixation card; if "against" movement is observed, it is moved closer to the patient’s eye. The final result is determined by measuring the distance between the fixation card and the retinoscope from the patient’s eye, converted to diopters using the formula 100 divided by the measured distance. Example calculation: If the neutral point is found at 50 cm while the fixation card is at 40 cm, the Nott retinoscopy value would be +0.50 D (2.5 D - 2.0 D)..

[Audio] Interpretation of Nott Retinoscopy Results A positive value indicates a lag of accommodation, while a negative value indicates a lead of accommodation. Nott retinoscopy has the advantage of achieving neutrality by adjusting distance, avoiding the use of additional lenses that might stimulate or relax accommodation. Normal values for lag of accommodation range from +0.25 DS to +0.75 D. High lag of accommodation is associated with near esophoria, convergence excess, accommodative insufficiency, under-corrected hyperopia, overcorrected myopia, and presbyopia. Lead of accommodation is observed in near exophoria, convergence insufficiency, accommodative excess, spasm of accommodation, under-corrected myopia, and overcorrected hyperopia..

[Audio] ASSESSMENT OF DYNAMIC ACCOMMODATION Accommodative facility refers to the ability of the visual system to effectively stimulate and inhibit accommodation, the process of adjusting the eye's focus for different distances. This ability can be assessed either monocularly or binocularly..

[Audio] Lens Flipper Test for Accommodative Facility Equipment 1. Plus, and minus 2.00 D lens flipper 2. Near target with 20/30 letters or symbols 3. Timer or stopwatch 4. Eye patch or handheld occluder (for monocular testing)Start with patient wearing distance prescription Procedure for Accommodative Facility (Monocular) Patient wears the distance correction Place the 20/30 letter target at 40cm from the patient Occlude the left eye Place the plus 2.00 D lenses binocularly in front of the patient’s eyes Ask the patient to report when the letters are clear and single Once the patient reports the letters are clear and single, flip the lenses to the minus 2.00 D side. Ask the patient to report when the letters are clear. Continue this for 1 minute, alternately flipping the +2.00 and -2.00 lenses Need count of the number of cycles of plus and minus lenses the patient can clear within 1 minute (One cycle is clearing one set of plus and minus lenses) Record results in number of cycles per minute (cpm) Transfer the occluder or patch to the right eye. Repeat Steps for the left eye Important point: Emphasize the importance of keeping the target clear and single during the test..

[Audio] Result Interpretation Accommodative facility is usually tested over a 1-minute period. The patient struggles to clear the target with plus lenses, which is indicative of accommodative excess. The patient struggles to clear the target with minus lenses is seen in presbyopes and with accommodative insufficiency Norms for accommodative facility DIOPTER AGE NORMAL CPCM +2.00 Child to 18years 10cpcm +1.50 19-31years 8cpcm +1.00 32-45years 6cpcm.

[Audio] Treatment and key test findings for various accommodative dysfunctions Accommodative Dysfunction Key Test Finding Treatment Accommodative insufficiency Reduced amplitude of accommodation Large lag of accommodation Inability to clear minus lenses on monocular facility test Plus lenses for near vision therapy Accommodative infacility Inability to clear minus and plus lenses on monocular facility test vision therapy Accommodative excess Inability to clear plus lenses on monocular facility test Lead of accommodation vision therapy Ill-sustained accommodation Ability to clear minus and plus lenses on binocular facility test diminishes over time Plus lenses for near vision therapy.

[Audio] Relative Accommodation Negative Relative Accommodation (NRA) and Positive Relative Accommodation (PRA) Testing of Relative Accommodation Testing relative accommodation assesses the flexibility in the relationship between accommodation and vergence. This test is conducted under fused or binocular conditions to evaluate how changes in accommodative convergence are managed by fusional vergence. When the clinician binocularly introduces either plus (NRA) or minus (PRA) lenses, the accommodative response is altered, while vergence is maintained within Panum’s fusional area. It is important to note that as the lenses are introduced, there is a transient change in eye posture to maintain single vision. For example, when minus lenses are added, the eyes are transiently driven to converge due to the increased accommodation and corresponding accommodative vergence. Maintaining fusion requires an immediate compensatory response of negative fusional vergence (NFV) to realign the target within the center of Panum’s area..

[Audio] The results of relative accommodation can be further investigated with other tests: Accommodative Amplitude Testing : Measures the total range of accommodation. Fusional Vergence Testing : Assesses the range and effectiveness of fusional vergence. Monocular Accommodative Facility: Evaluates the ability to switch between different accommodative demands. The magnitude of the relative accommodation finding is influenced by: Vergence Range: The range of vergence movement required to maintain single vision. AC/A Ratio: The ratio of accommodative convergence to accommodation, providing insights into the relationship between accommodation and vergence NRA & PRA helps us to Determine:- Normal Accommodative Functions. -Accommodation Excess. -Accommodation Insufficiency. -Status of Fusional Convergence. -Status of Fusional Divergence. -Determine Retractive Corrections. In PRA, accommodation is stimulated with minus lens that’s why it's called Positive Relative Accommodation. In NRA, accommodation is relaxed with plus lens that’s why it’s called Negative Relative Accommodation.

[Audio] Equipment 1. Trial frame 2. Near vision chart or Card 3. Negative Lenses. Procedure Negative Relative Accommodation (NRA) Place the patient's distance correction in the trial frame before starting the procedure. Ask the patient to sit comfortably. Hold the near vision target (N6 or the smallest line the patient can comfortably read) at a distance of 40 cm from the patient. Instruct the patient to fixate on the near vision target. Begin adding plus lenses in 0.25 D increments at a rate of one step every 1-2 seconds while the patient maintains fixation on the target. Ask the patient to tell you when the letters begin to blur as you add plus power. When the patient reports blur, ask them to attempt to clear the target if possible. Note the amount of plus power added until the patient reports the first sustained blur. If applicable, reverse the process by reducing the plus power to measure any recovery. Ask the patient to report when the target becomes clear again. Record the amount of plus power added until the first sustained blur as the NRA. For example, if the blur occurs with +2.25 D and cannot be cleared, record the NRA as +2.25 D. If recovery is measured, for instance, at +1.75 D, record the complete NRA measurement as +2.25/+1.75. Place the second lens in the trial frame before removing the 1st lens..

[Audio] Procedure for Measuring Positive Relative Accommodation (PRA) Place the patient’s distance correction in the trial frame before starting the procedure. Ask the patient to sit comfortably. Hold the near vision target (N6 or the smallest line the patient can comfortably read) at a distance of 40 cm from the patient. Instruct the patient to fixate on the near vision target. Begin adding minus lenses in 0.25 D increments at a rate of one step every 1-2 seconds while the patient maintains fixation on the target. Ask the patient to tell you when the letters begin to blur as you add minus power. When the patient reports blur, ask them to attempt to clear the target if possible. Note the amount of minus power added until the patient reports the first sustained blur. If applicable, reverse the process by reducing the minus power to measure any recovery. Ask the patient to report when the target becomes clear again. Record the amount of minus power added until the first sustained blur as the PRA. For example, if the blur occurs with –2.50 D and cannot be cleared, record the PRA as –2.50 D. If recovery is measured, for instance, at –2.00 D, record the complete PRA measurement as –2.50/–2.00..

[Audio] Positive Relative Accommodation: Interpretation of PRA Test Expected PRA Value:-1.50DS to -2.50DS Normal Accommodative Function: If PRA value falls between -1.50DS to -2.50DS. Accommodation Insufficiency: If PRA value less than -1.50DS. Accommodation Excess: If PRA value more than -2.50DS. Inadequate fusional divergence: If PRA value less than -1.50DS.Minus lenses in PRA testing induces accommodation and increases accommodative convergence due to the AC/A link. In order to maintain clear binocular single vision, the eyes must neutralize the accommodative convergence by fusional divergence response. Over-correction in Hyperopia or Under-correction in Myopia: High PRA value can be indicative of Over-correction in hyperopia and Under-correction in Myopia..

[Audio] Positive Relative Accommodation: How does PRA can identify overcorrection in hyperopia and under correction in myopia? In both conditions, overcorrection in hyperopia and under-correction in myopia rays focus in front of the retina. To shift the rays in the retina, we need certain amount of diverging or minus power. This extra minus power will be added to the PRA value which results high PRA value in Over-corrected Hyperopia and Under-corrected Myopia. So, if patient's accommodation response is normal but showing high PRA, value then it indicates Over-correction in Hyperopia and Under-correction in myopia is done during the Refraction..

[Audio] Negative Relative Accommodation: Interpretation of NRA Test: Expected NRA Value: +1.75DS to +2.50DS Normal Accommodative Function: If NRA value falls between +1.75DS to +2.50DS Accommodation Insufficiency: If NRA value more than +2.50DS. Accommodation Excess: If NRA value less than +1.75DS Inadequate fusional convergence: If NRA value less than +1.75DS.Addition of plus lenses relaxes accommodation and stimulates divergence due to AC/A link. In order to maintain clear single binocular vision, the eyes converge or use. fusional convergence. Inadequate fusional convergence therefore can reduce the end point of NRA. Over-correction in Myopia or Under-correction in Hyperopia: High NRA value can be indicative of Over-correction in Myopia and Under-correction in Hyperopia..

[Audio] How does NRA can identify over correction in myopia & under correction in hyperopia? In both conditions, overcorrection in myopia and under-correction in hyperopia rays focus behind the retina. To bring back the rays in the retina, we need certain amount of converging or plus power. This extra plus power will be added to the NRA value which results high NRA value in Over-corrected Myopia and Under-corrected Hyperopia. So, if patient's accommodation response is normal but showing high NRA value then it indicates Over-correction in Myopia and Under-correction in Hyperopia is done during the Refraction..