Scleral changes with accommodation.

PURPOSE: To assess whether the sclera changes its shape during accommodation, quantify those changes and ascertain whether they depend on age and refractive power.

METHODS: Twenty-two subjects, aged between 19 and 84 years old were recruited for the study. Young subjects were grouped according to their refractive power as emmetropes (seven subjects) and myopes (seven subjects). Data were obtained with a height corneo-scleral topographer (Eye Surface Profiler) with coverage area far beyond the limbus. Lenses of different power were used to stimulate accommodative demand of 0.0 D, 2.5 D and 4.0 D. Elevation differences between measurements acquired while at the intermediate or close target and infinity where calculated for each participant for the horizontal meridian for a 16 mm chord.

RESULTS: We found that sclera undergoes significant changes in its shape with accommodation in young subjects able to accommodate but not for those with limited accommodation. For a 4.0 D stimulus at the nasal side the scleral change amounted on average to 390 ± 330 μm (mean ± S.D.) for the young group. This phenomenon was more pronounced in myopes (for a 4.0 D target; nasal part: 560 ± 350 μm (mean ± S.D.)) than emmetropes (for a 4.0 D target; nasal part: 220 ± 120 μm (mean ± S.D.)). Differences were also found between different meridians.

CONCLUSIONS: Scleral shape undergoes changes with accommodation and this phenomenon is more pronounced in myopes than emmetropes.