Evaluation of factors influencing distance stereoacuity on FD2 after surgery in Intermittent Exotropia

1. Rohit Saxena¹
2. Ashish Kakkar¹
3. Vimla Menon¹
4. Pradeep Sharma¹
5. Swati Phuljhele¹

¹Squint and Neuro-Ophthalmology Services, Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi, India.

Purpose: To evaluate factors affecting restoration of stereoacuity after surgery in cases of intermittent exotropia X(T).

Methods: Thirty consecutive patients of X(T) scheduled for surgical intervention and 30 age matched controls underwent complete ophthalmic and orthoptic examination. Deviations were measured with prism bar cover test for near and distance. For all cases and controls stereo acuity was measured using TNO for near and Frisby Davis Distance (FD2) stereotest at 6m for distance. All cases of X(T) were followed up with the above tests postoperatively at 1week, 1month, 3 month and 6month.

Results: Successful surgical alignment was seen in 84% of cases. The median distance stereo acuity improved from preoperative value of 50 arcsec to 17.5 arcsec and near stereoacuity improved from 240 arcsec to 90arcsec at 6 month postoperatively. Median distance and near stereo acuity in controls was 15 and 60 arcsec respectively. There was significant difference in both distance and near stereoacuity between controls and cases even after surgery. Preoperative near and distance stereoacuity made a significant difference in achieving normal stereoacuity after surgery while age and amount of pre and postoperative deviation was not found to have any affect. None of the above mentioned factors had any influence on successful postoperative surgical correction.

Conclusion: There is significant improvement in both near and distant stereoacuity postoperatively in X(T) however the achievement of normal level depends upon the preoperative sensory status of the patient. Sensory and motor outcomes in these cases of X(T) appear to be exclusive of each other.