Nandini Ravi,  BS Optometry

Fellowship in Binocular Vision and Vision Therapy, The Sankara Nethralaya Academy

Introduction

Accommodative Insufficiency (AI) is characterized by reduced Amplitude of Accommodation (AOA), which is confirmed by comparing the calculated AOA with the expected amplitude for the patient’s age using Hofstetter’s formula¹. The patient primarily has difficulty stimulating accommodation. While in Convergence Insufficiency (CI), we see greater exophoria at near than distance and receded Near Point of Convergence (NPC) as the hallmarks. Evidences show that, the prevalence of AI with comorbid CI is high among school-age children² and also, AI could be the primary reason for asthenopic symptoms in CI³.  Further, AI with CI is a distinct syndrome and management should focus at treating AI⁴. This report gives a brief idea on factors to consider while managing AI co-existing with CI.

 Diagnostic criteria

Patients with AI with associated CI complaints of severe asthenopia and blurred vision for near as well as distance³. The diagnostic criteria for AI include reduced AOA of about 2D lesser than the expected^5,6, reduced Positive Relative Accommodation(PRA) and difficulty clearing minus lenses in both monocular as well as binocular accommodative facility (+/-2Dflippers)⁵ with a high lag of accommodation in Monocular Estimation Method retinoscopy(MEM)^1,7. In case of CI, the presence of large near exophoria, reduced near Positive Fusional Vergence (PFV) or failing Sheard’s criterion⁸ and primarily a receded NPC contribute to the diagnosis ^{8, 9}.

Factors to be considered for management 

1. Firstly, it is about identifying the primary aetiology to be AI and decide on near added plus lenses to address blurred vision at near and the high lag of accommodation. Prescribing a bifocal or Progressive Addition Lenses (PALS) should be considered⁴.
2. Then, consider the phoria status; if the AI has given rise to a secondary CI, giving a near addition will resolve the signs of CI¹⁰.However, if you see that the near exophoria has worsened with near addition and the patient complaints of double vision, consider providing base in prisms. Gunter et al. reported that, such special therapeutic combination of bifocals and base in prisms to be effective in symptom relief⁴.
3. After refractive adaptation, it is essential to normalize other vergence and accommodative parameters through In-Office Vision Therapy (VT).
4. Subsequently, gradual weaning of prisms and near addition should be done with combination of home VT options¹¹.

Cumulatively (Figure 1), the principle behind treatment is on addressing the primary aetiology, prescribing the beneficial refractive correction for distance and near, followed by optimizing the accommodation and vergence status.



Figure 1: Flowchart describing the sequential management and factors to contemplate

 Recent Advancements

Software based home vision therapies are found to show improvements in binocular vision parameters in children withCI¹². Bynocs¹³is indigenous VT software for quantifying and training vergence and accommodative parameters. The software can train for heterophoria, accommodative dysfunctions, fusional vergence, stereopsis, saccades, pursuits etc. This home based software can also serve as a tele-health vision therapy tool for the practitioners to monitor the progress.

Overall, it can be said that, every eye care practitioner should have a bird’s eye view in handling such complex co-morbidities.

 

References

1. Daum, K. M. (1983). Accommodative insufficiency. American journal of optometry and physiological optics, 60(5), 352-359.
2. Borsting, E., Rouse, M. W., Deland, P. N., et al. (2003). Association of symptoms and convergence and accommodative insufficiency in school-age children. Optometry (St. Louis, Mo.), 74(1), 25.
3. Marran, L. F., De Land, P. N., & Nguyen, A. L. (2006). Accommodative insufficiency is the primary source of symptoms in children diagnosed with convergence insufficiency. Optometry and Vision Science, 83(5), 281-289.
4. Von Noorden, G. K., Brown, D. J., & Parks, M. (1973). Associated convergence and accommodative insufficiency. DocumentaOphthalmologica, 34(1), 393-403.
5. Cacho, P., García, A., Lara, F., et al. (2002). Diagnostic signs of accommodative insufficiency. Optometry and Vision Science, 79(9), 614-620.
6. Hofstetter, H. W. (1947). A useful age-amplitude formula. American Journal of Optometry and Archives of American Academy of Optometry, 24(4).
7. Wajuihian, S. O., &Hansraj, R. (2016). Vergence anomalies in a sample of high school students in South Africa. Journal of Optometry, 9(4), 246-257.
8. Davis, A. L., Harvey, E. M., Twelker, J. D., et al. (2016). Convergence insufficiency, accommodative insufficiency, visual symptoms, and astigmatism in Tohono O’odham students. Journal of ophthalmology, 2016.
9. INSUFFI, C. (2008). Randomized clinical trial of treatments for symptomatic convergence insufficiency in children. Arch Ophthalmol, 126(10), 1336-1349.
10. Scheiman, M., & Wick, B. (2008). Clinical management of binocular vision: heterophoric, accommodative, and eye movement disorders. Lippincott Williams & Wilkins.
11. Aletaha, M., Daneshvar, F., Mosallaei, M.et al. (2018). Comparison of three vision therapy approaches for convergence insufficiency. Journal of Ophthalmic & Vision Research, 13(3), 307.
12. Huston, P. A., & Hoover, D. L. (2015). Treatment of symptomatic convergence insufficiency with home-based computerized vergence system therapy in children. Journal of American Association for Pediatric Ophthalmology and Strabismus, 19(5), 417-421
13. https://www.bynocs.com/