Morphological features of anterior segment: factors influencing intraocular pressure after cataract surgery in nanophthalmos

Abstract

Purpose To investigate the anterior segment in nanophthalmic eyes and their association with intraocular pressure after cataract surgery. Methods Thirty-two nanophthalmic eyes (axial length [AL] < 18.5 mm) in 18 patients and 35 normal eyes (21 ≤ AL ≤ 24.5 mm) in 35 controls who had undergone uneventful cataract surgery were included. Swept-source optical coherence tomography was used to compare the anterior segment structures between the two groups. The associations between the anterior segment characteristics of nanophthalmic eyes and postoperative intraocular pressure (IOP) were also investigated. Results The IOP-lowering effect of cataract surgery was remarkably insufficient in nanophthalmic eyes. Peripheral anterior synechiae (PAS) were observed in 56% (18/32) of nanophthalmic eyes, and a characteristic boomerang-shaped iris was observed in 28% (9/32). The anterior surface of the iris seemed “smoother” in nanophthalmic eyes than in normal eyes. Schlemm’s canal (SC) diameter, SC area, trabecular meshwork (TM) thickness, TM width, and TM area were generally smaller in the nanophthalmic eyes. Younger age, higher preoperative IOP, broader PAS, and smaller SC area were main contributors to higher postoperative IOP. AL and SC diameter may also be of great importance in IOP prediction in patients without glaucoma surgery and PAS. Conclusions The morphological features of the anterior segment in nanophthalmic eyes are significantly different from those of normal eyes. Influencing factors such as age, AL, preoperative IOP, extent of PAS, SC and TM size could all be prognostic for IOP after cataract surgery in nanophthalmic eyes. Trial registration ClinicalTrails.gov, Trial registration number: NCT02182921, Registered 8 July 2014.

Cataract surgery in adult eyes with short axial length

“…Patients with AC depth <1.5 mm had a six folds increased risk of postoperative IOP spike compared to those with AC depth >1.5 mm [6]. In another study, Lu and colleagues concluded that postoperative IOP in nanophthalmic eyes significantly correlated with preoperative IOP, history of glaucoma surgery, the extent of peripheral anterior synechiae, Schlemm's canal area, and trabecular meshwork area [21 ▪ ].…”

“…A recent study of 144 patients by Rajendrababu and colleagues found that 68% of nanophthalmic eyes had angle-closure and 36% had angle-closure glaucoma [3 ▪▪ ]. Regarding the risk of open-angle glaucoma, a study by Lu and colleagues found that nanophthalmic eyes have less developed Schlemm's canal and trabecular meshwork which subsequently affect the aqueous outflow drainage [21 ▪ ]. The Beijing Eye Study has demonstrated that pseudoexfoliation syndrome was significantly associated with shorter AL ( P = 0.03) and shallower AC ( P = 0.03).…”