Figure 7.

Mathematical model for estimating the magnitude of pressure exerted by intraretinal cysts. Inward deflection of the retina over the cysts indicates that the pressure exerted by the intraretinal fluid pockets is greater than the intraocular pressure. The magnitude of this pressure is equal to the force (F) applied per unit area (A). Considering the spherical shape of intraretinal cysts as a single body, pressure applied by the cysts on the RNFL (P_CME) can then be calculated as: [4/3 πr_cyst³] x d x g/ 4 πr_cyst² where (d) denotes the density of the water and (g) is the gravitational constant. Similarly, the outward pressure on RNFL exerted by intraocular pressure (P_IOP) is equal to [4/3 πr_vitreous³] x d x g/ 4 πr_vitreous². Simplification of the formulas will reveal that the ratio of the radii of the vitreous cavity (r_vitreous) and intraretinal cysts (r_cyst) will yield the quotient of the opposing pressures (P_IOP/P_CME). Substituting the numeric value of the vitreous radius (16.28 mm)⁵⁷ and using the average diameter of the cysts observed in this study (264.5 ± 78.4 µm) indicate that the force applied by the intraretinal cysts is comparable to an increase in intraocular pressure up to 62 mm Hg.