Abstract
Purpose:
The purpose of this study was to determine the effect of upgaze on lower eyelid position in patients with unilateral and bilateral congenital ptosis.
Methods:
Thirty- five patients were recruited for this study. Clinical photographs and measurements were taken in primary gaze and upgaze. An 8-millimeter circular disc was placed on the child’s forehead as a measuring guide. Measurements taken from photograph and clinical records include inferior scleral show (ISS), vertical lower lid height (LL) and canthal tilt angle (CTA).
Results:
There were 35 patients with congenital ptosis. 62.9% (n=22) of them were male. The mean age of the patients was 4.38 ± 1.81 years. 62.9% (n=22) of the patients had unilateral ptosis and 37.1% (n=13) had bilateral ptosis. There was more ISS in unilateral ptosis eyes compared to the normal side in both primary gaze (0.3± 0.5mm; 0.1± 0.2mm) (p<0.05), as well as in upgaze (3.3± 1.3mm; 2.1± 1.3mm) (P< 0.01); with corresponding increase in ISS on upgaze (p<0.05). There was also more ISS in unilateral ptosis eyes as compared to bilateral ptosis eyes in primary gaze (0.3 ± 0.5mm; 0.1± 0.2mm) (p<0.05) as well as in upgaze (3.3± 1.3; 1.6± 1.3)(P<0.01); with accompanying increase in ISS on upgaze (P<0.01). There was less elevation of the lower lid in ptosis eyes (0.5± 0.7mm) versus normal eyes (0.8± 0.7mm) but this was not statistically significant (p=0.07). CTA was lower in ptosis eyes compared to normal eyes in primary gaze (2.8± 3.5°; 5.2± 3.4°) (p<0.01) as well as in upgaze (0.7± 3.9°; 3.2± 4.6°)(p<0.05).
Conclusions:
Upgaze appears to increase inferior scleral show in children with congenital ptosis. We propose that the contraction of the superior complex to allow foveation results in compensatory inferior rectus contraction and a tightening of Lockwood ligament with superior globe displacement. There is underdevelopment of the levator muscle in congenital ptosis, which results in less compensatory contraction of the lower eyelid retractor and less elevation of the lower lid in ptosis eyes. Canthal tilt is lower in congenital ptosis than in normal eyes on primary gaze and upgaze. The weaker levator muscle is unable to counteract this, hence resulting in greater downward angulation at the lateral canthus (the fulcrum). It is important to understand the vectors of movement, as patients need to be counseled for possible cosmetic asymmetry on upgaze.