Described in the early fifties, V phenomenon remains a controversial subject in respect to its etiopathogeny. Several theories have been proposed dealing to specific surgical treatments. According to the "oblique" theory, we have been performing a bilateral inferior oblique muscle weakening procedure alone or combined with horizontal muscle surgery in our patients presenting horizontal squint associated with a "V" phenomenon.
Since 1984, among the 103 patients presenting with a "V" phenomenon, we have been able to analyze 55 cases (40 "V" esotropias and 15 "V" exotropias) who underwent 3 different surgical protocols; 1) bilateral inferior oblique (IO) muscles weakening procedure combined with conventional horizontal surgery, 2) bilateral IO weakening procedure combined with posterior fixation of Med. Recti (Faden operation) in esotropias only, or 3) bilateral inferior oblique muscles weakening alone. All groups were comparable in respect with there pre-surgical "V" pattern.
No statistical significant difference in reduction of the "V" pattern could be demonstrated in the different treatment protocols. "V" esotropias showed a mean 16.3 delta diopter reduction +/- 2.2 SEM in treatment number 1; 19.8 +/- 2.1 in treatment 2. Reduction was only 10.7 +/- 3.3 in group with third treatment. "V" exotropias reduction were: 15.4 delta diopter +/- 1.6 in the combined surgical procedure compared to 18.3 +/- 4.8 in IO weakening alone. No dose-effect relationship could be clearly demonstrated in measured IO weakening procedure.
IO weakening procedure is effective in reducing "V" pattern. This effect is enhanced if associated with an horizontal muscle surgery which reduces the horizontal deviation especially in in V esotropias. We prefer Fink's procedure to simple myotomy since its allows a measurable and reversible IO weakening.