Clinical Implications of Heterophorias PDF

CLINICAL IMPLICATIONS OF HETEROPHORIAS 1. CONVERGENCE INSUFFICIENCY Signs: (often related to prolonged, visually demanding tasks) 1. Exophoria at near. 2. Orthophoria or low exophoria at distance 3. Receded NPC. Generally symptomatic patients will present with decreased converge...

CLINICAL IMPLICATIONS OF HETEROPHORIAS 1. CONVERGENCE INSUFFICIENCY Signs: (often related to prolonged, visually demanding tasks) 1. Exophoria at near. 2. Orthophoria or low exophoria at distance 3. Receded NPC. Generally symptomatic patients will present with decreased convergence ability with repeated testing. 4. Reduced positive fusional vergence. 5. Low AC/A. Differential Diagnosis: Serious underlying etiology must be ruled out in the finding of convergence insufficiency. Typically, a true convergence insufficiency presents with longstanding, chronic complaints and negative health history. There is also no history of use of medication that could affect accommodation. 1. Accommodative Insufficiency (pseudoconvergence insufficiency): In this condition all tests assessing the accommodative ability will be reduced which is not the case in convergence insufficiency. 2. Convergence Paralysis: This is a supranuclear gaze disorder that has to be ruled out. Patients can fully adduct their eyes during conjugate gaze movements and the deviation is comitant. This condition can occur secondary to ischemic infarction, demyelination, which can occur following a flu or viral infection. 3. Parkinson’s disease 4. Parinaud’s syndrome 5. Medial rectus weakness due to multiple sclerosis and myasthenia gravis. Symptoms: The symptoms are often associated with near work and often worse at end of the day. 1. eyestrain 2. headaches after short periods of reading 3. blurred vision at near due to the relationship between accommodation and convergence. 4. diplopia 5. sleepiness and difficulty in concentrating 6. loss of comprehension over time 7. a pulling sensation probably due to fatigue because of the continuous focus adjustments required. 8. apparent movement or jumping of the reading material. Absence of symptoms could indicate the possibility of suppression, avoidance of near tasks, high pain threshold or occlusion of one eye when reading. Treatment: 1. LENSES: Correction of any underlying refractive error especially in the presence of significant myopia. Low degrees of myopia could be secondary to a convergence insufficiency and therefore should not necessarily be prescribed rather therapy provided. The presence of hyperopia could complicate the problem as it could increase the exophoria and thus the patient’s symptoms. In this case therapy should be given following prescription of the spectacles. 2. PRISM: If a vertical deviation is present, vertical prism should be prescribed before therapy is started. The amount of vertical prism to be prescribed can be determined from the associated phoria measured with any fixation disparity device. Base-In prisms have not proven very successful in treating convergence insufficiency. They should only be prescribed if therapy is unsuccessful. The amount of base-in prism should be determined from the associated phoria during fixation disparity testing. 3. VISION THERAPY: Vision therapy would require between 12 to 24 visits and will depend on the severity of the condition, the age of the patient, motivation and compliance with home therapy procedures. Vision therapy will comprise office therapy and home therapy. Office therapy includes: Tranaglyphs Vectograms Vodnoy Rule (single aperture rule) Home therapy includes: PHD exercises (see notes attached) Brock string (see notes attached) Eccentric circles Recommended reading:  1. Clinical Trial of Treatments for Convergence Insufficiency in Children. Archives of Ophthalmology 2005. [Download Article, Free PDF] 2. Visit website: http://www.convergenceinsufficiency.net/ 3. http://www.convergenceinsufficiency.net/uploads/SurveyOfTreatmentModali ties.pdf 2. CONVERGENCE EXCESS Signs: 1. Esophoria at near. 2. Orthophoria, or low to moderate esophoria at distance. 3. Reduced negative fusional vergences / BI reserves. 4. High AC/A ratio 5. Refractive error usually moderate to high hyperopia. 6. Patients often report diplopia rather than blur at the end point with the PRA and amplitude of accommodation with the ‘minus lens to blur’ method. Symptoms: 1. Discomfort aggravated by reading or near work. 2. eyestrain 3. headaches after short periods of reading 4. blurred vision at near due to the relationship between accommodation and convergence. 5. diplopia 6. sleepiness and difficulty in concentrating 7. loss of comprehension over time Absence of symptoms could indicate the possibility of suppression, avoidance of near tasks, high pain threshold or occlusion of one eye when reading. Treatment: 1. LENSES: If the convergence excess is due to accommodative dysfunction, then initially any significant refractive error must be corrected. The maximum plus to best visual acuity must be prescribed in the hyperopic patient. A cycloplegic examination will be required to determine the maximum plus to be prescribed.  Additional plus lenses can be prescribed for near. When prescribing these lenses, the lowest amount of plus that will eliminate the patient’s symptoms and normalize the phoria is prescribed. This additional plus can be determined using MEM retinoscopy, or NRA. 2. PRISMS: If a vertical deviation is present, vertical prism should be prescribed before therapy is started. The amount of vertical prism to be prescribed can be determined from the associated phoria measured with any fixation disparity device. Due to the high AC/A ratio, the use of lenses is so effective that horizontal prisms are rarely required. However, base-out prisms may be required for moderate to high degrees of esophoria’s. Prisms should only be prescribed if therapy would not be successful and the patient is symptomatic. The amount should be determined from the associated phoria in fixation disparity measurement. 3. THERAPY: Vision therapy would require between 12 to 24 visits and will depend on the severity of the condition, the age of the patient, motivation and compliance with home therapy procedures. Vision therapy will comprise office therapy and home therapy. Office therapy includes: Tranaglyphs Vectograms Vodnoy Rule (double aperture rule) Home therapy includes: Brock string (see notes attached) Eccentric circles (transparent) HOMEWORK: Differential Diagnosis of convergence excess Recommended Readings: 1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1771224/ 2. http://www.cybersight.org/bins/volume_page.asp?cid=1-351-355-447 3. http://www.ncbi.nlm.nih.gov/pubmed/9120214 3. DIVERGENCE INSUFFICIENCY Signs: 1. Larger eso (phoria or tropia) deviation at distance. 2. Orthophoria or small esophoria at near. 3. Reduced negative fusional vergences / BI reserves. 4. Normal or low AC/A ratio 5. Normal versions, and deviation is concomitant (i.e. same magnitude in all directions of gaze). Symptoms: 1. Intermittent diplopia more evident at distance and of gradual onset. The diplopia disappears once the patient has rested. 2. Headaches 3. Ocular fatigue 4. Nausea 5. Dizziness 6. Train and car sickness 7. Blurred vision 8. Poor accommodative facility (far to near) 9. Photophobia Treatment: 1. LENSES: Any significant refractive error must be corrected especially if hyperopia is present the maximum plus to best visual acuity should be prescribed. However, lenses are not as effective in this condition. 2. PRISMS With divergence insufficiency, prisms are often the most effective method of treatment, as it is difficult to voluntarily diverge the eyes. The amount of base-out prism can be determined from the phoria measurement, Sheard’s criterion or fixation disparity. However, the associated phoria measured with the Mallet unit tends to overestimate the amount of prism required, thus the disparometer or Wesson Card should rather be used. The minimum amount of prism that will relieve the symptoms should be prescribed. Since divergence insufficiency produced symptoms only at distance, the prescription can be for distance tasks only or worn all the time. 3. VISION THERAPY If the prescription of prism is not successful, then therapy should be considered. Office therapy includes: Projected Tranaglyphs Projected Vectograms Home therapy includes: Brock string (see notes attached) HOMEWORK: Differential Diagnosis of divergence insufficiency Recommended Readings: 1. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1310487/pdf/taos00028- 0172.pdf 2. http://archopht.ama-assn.org/cgi/reprint/118/9/1237.pdf 3. http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WH5- 45SRK21- 18&_user=7416867&_coverDate=12%2F31%2F2000&_rdoc=1&_fmt=high&_or ig=search&_sort=d&_docanchor=&view=c&_searchStrId=1377815430&_rerunO rigin=google&_acct=C000058881&_version=1&_urlVersion=0&_userid=741686 7&md5=742f1941b19018dc0d65684d978dee5b  4. DIVERGENCE EXCESS Signs: 1. Greater exo deviation (phoria or tropia) at distance. 2. Orthophoria or low exo deviation (phoria or tropia) at near. 3. Normal positive fusional vergence. 4. Comitant deviation which can be intermittent. 5. Vertical deviation in some cases due to overaction of the inferior oblique muscle. 6. High AC/A ratio. Symptoms: The symptoms are often associated with distance tasks. 1. Difficulty concentrating 2. fatigue 3. day dreaming Absence of symptoms could indicate the possibility of suppression or anomalous retinal correspondence (ARC) in the case of a tropic patient. Treatment: 1. LENSES: Any significant refractive error must be corrected. If the patient has a high AC/A ratio and is myopic, lenses are very beneficial. Don’t prescribe for low amounts of hyperopia. Added minus lenses at distance may be helpful. 2. PRISMS: Any vertical deviation must be corrected with prisms based on the associated phoria from fixation disparity testing. Vision therapy is very successful in divergence excess and therefore horizontal prisms are very rarely used. 3. THERAPY: The therapy routine will be determined based on whether the patient has a tropia or phoria, and if the patient has sensory adaptations (suppression, ARC). Details to be covered in the Binocular vision module. In-office: Anti-suppression Projected tranaglyphs  Projected vectograms Home therapy: Brock string Recommended Reading: 1. http://www.academy.org.uk/lectures/barnard8.htm 2. http://www.umsl.edu/~garziar/factsheets/factsheet_diverexcess.pdf 3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1316738/ 4. http://www.oepf.org/jbo/journals/7-3%20Flax,%20Cooper%20iewpoints.pdf RH/OPTOM/UKZN