Shortening of Interpupillary Distance after Instillation of Topical Prostaglandin Analog Eye Drops

To investigate changes in the interpupillary distance (IPD) after continual instillation of topical prostaglandin analogs (PGAs) in glaucoma patients as an objective indicator of prostaglandin-associated periorbitopathy (PAP).

Retrospective, comparative case series.

A total of 152 institutional patients with glaucoma were enrolled in this study. Inclusion criteria were visual acuities exceeding 10/20 bilaterally and no intraocular surgery during observation. Intervention/observation procedures: First-time bilateral instillation of bimatoprost, travoprost, latanoprost, or tafluprost and IPDs measured by automatic refractometry. IPDs, intraocular pressures (IOPs), and refractive errors were measured before and after continual drug administration (treatment, 2-24 months).

Post-treatment changes in IPDs. A total of 61 untreated patients served as controls.

The IPDs shortened significantly (P < 0.001) after treatment (-0.80 ± 2.1 mm); the IPDs of control subjects remained unchanged (0.05 ± 0.96 mm; P = 0.69). The IPD change after bimatoprost instillation (-2.20 ± 0.97 mm) was significantly (P < 0.001) greater than with other PGAs (-0.65 ± 2.09 mm). The IOPs decreased significantly (P < 0.001) (-3.7 ± 4.3 mm Hg); the refractive errors did not change significantly (P < 0.099) (-0.07 ± 0.69 diopter) post-treatment. The percentages of subjects with 2-mm or greater decreases in IPD after bimatoprost, travoprost, latanoprost, or tafluprost were 85.7%, 20.0%, 18.2%, and 17.2%, respectively, and with 3-mm or greater decreases in IPD 35.7%, 12.0%, 14.5%, and 12.1%, respectively. The specificities were 93.4% and 100% in the control group, respectively, with IPD threshold changes of 2 and 3 mm or more, respectively.

The IPD decreased significantly after topical PGAs within 24 months. The effect was significantly greater with bimatoprost than with other PGAs. The noninvasive, immediate automatic refractometry measurement may be an objective numerical indicator of PAP.