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

Qiang Lu,Yi Lu,Xiangjia Zhu,Wenwen He

doi:10.1186/s40662-020-00212-4

Qiang Lu, Yi Lu + Show 2 more

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https://doi.org/10.1186/s40662-020-00212-4

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Abstract

PurposeTo investigate the anterior segment in nanophthalmic eyes and their association with intraocular pressure after cataract surgery.MethodsThirty-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.ResultsThe 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.ConclusionsThe 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 registrationClinicalTrails.gov, Trial registration number: NCT02182921, Registered 8 July 2014.

Highlights

Nanophthalmos is a developmental failure of the anterior neural tube or optic pit [1]
We evaluated the following morphological features of the anterior segment: synechiae and the narrowing of the anterior chamber angle, the characteristics of the iris, and the changes in s canal (SC) and trabecular meshwork (TM)
Baseline characteristics Thirty-eight nanophthalmic eyes of 20 patients and 35 normal eyes of 35 age-matched controls were included in the follow-up

Summary

Introduction

Nanophthalmos is a developmental failure of the anterior neural tube or optic pit [1]. Due to the high lens/eye ratio, up to 54–77% of nanophthalmic eyes develop angle-closure glaucoma [5], which is the main cause of elevated intraocular pressure (IOP) in nanophthalmia. In eyes with angle-closure glaucoma, synechiae and a narrowing of the anterior chamber angle are direct and persistent causes of elevated IOP. Previous studies have demonstrated that broader peripheral anterior synechiae (PAS) can lead to a smaller reduction in IOP after phacoemulsification compared to that in eyes with fewer PAS [7]. The anterior positioning of the ciliary body and the dynamic physiological responses of the iris can contribute to the narrowing of the chamber angle and possibly to PAS formation, as could be illustrated by medical imaging and iris crypts, respectively [8, 9]

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