Postoperative refractive change following penetrating versus non-penetrating glaucoma surgery

Session Details

Session Title: Glaucoma II

Session Date/Time: Monday 15/09/2014 | 08:00-10:30

Paper Time: 09:33

Venue: Boulevard F (Level 1)

First Author: : T.Painhas PORTUGAL

Co Author(s): :    I. Lopes-Cardoso   M. Amorim   I. Almeida   J. Chibante-Pedro     

Abstract Details

Purpose:

To compare surgically induced corneal refractive changes following trabeculectomy versus nonpenetrating glaucoma surgery such as deep sclerectomy (NPDS) with and without implant. Technical evolution in non-penetrating glaucoma surgical techniques allows good ocular hypotensive effect as trabeculectomy with a better safety profile and by this reason surgery tends to be a progressively earlier indication in glaucoma management. Altered visual function induced by changes in corneal curvature following glaucoma surgery may be distressing to the patient. Also concerns on the refractive status after ocular surgery can be an increasing demand of patients, since the era of refractive surgery. A number of authors have studied corneal refractive changes induced by trabeculectomy but few studies focus the impact of these changes after nonpenetrating glaucoma surgery.

Setting:

Ophthalmology Department, Centro Hospitalar Entre-Douro-e-Vouga (Santa Maria da Feira, Portugal).

Methods:

Retrospective revision of the medical records of patients submitted to trabeculectomy or nonpenetrating deep sclerectomy (NPDS) with or without implant between 2011 and 2013, with selection of cases of isolated non-complicated glaucoma surgery having preoperative and postoperative evaluation of the refractive status of the eye with autokeratorefractometry (TONOREF™ II – Nidek®) and subjective refraction at least 3 months after surgery. Patients having ocular surgery between these measurements and perforations of the trabeculodescemetic membrane in NPDS were excluded from the study. A series of 34 eyes (33 patients) were included, being 15 eyes in the trabeculectomy arm and 19 eyes in the NPDS group. All patients had baseline and postoperative best-corrected visual acuity measurement, biomicroscopy, gonioscopy, Goldmann applanation tonometry, autokeratorefractometry. We compare the difference in subjective refractive cylinder (axis and power), difference in minimum keratometry (K1) and in maximum keratometry (K2) obtained with autokeratorefractometer (TONOREF™ II – Nidek®), before surgery and at lest 3 month after the procedure.

Results:

Mean patient age was 68.4 years ± 8.1 in the group of trabeculectomy and 69.05 years ± 9.05 in the group of patients who underwent NPSD and did not differ among groups. Mean intraocular pressure (IOP) preoperative was 25.64 mmHg in the trabeculectomy group and 26.3 mmHg in the NPSD group. Postoperative IOP did not differ among groups (p< 0.05) and was 15.2 mmHg vs. 14.7mmHg at 1 month and 15.7mmHg vs. 14.5 mmHg at 3 months for trabeculectomy and NPSD respectively. Changes in astigmatism power after the procedure was significantly different from the baseline in the group of trabeculectomy (p=0.04) but not in the NPSD group (p=0.74). The variation in the axis after the surgery was 25º in the trabeculectomy groups and 19.4º in NPDS group but was not significantly different between the groups (p=0.2). K1 and K2 in the NPDS group did not change significantly after surgery (p= 0.8 and 0.06 respectively). In the trabeculectomy group despite a greater change in keratometry values with the procedure than in NPSD group, these were also not significantly different (p=0.051 and 0.08, for K1 and K2 respectively).

Conclusions:

NPDS induced less astigmatism and refractive changes than trabeculectomy, although the keratometry changes were not statistically different than preoperatively in none of the procedures, probably attending to the small sample size of our study. Such differences can be due to different anterior chamber architecture by the presence of an intact trabeculodescemetic membrane in NPDS or also to different scleral flap suturing in the two procedures. NPDS scleral sutures tend to be looser comparing to trabeculectomy, because in trabeculectomy scleral flap suturing is the flow limiting step preventing postoperative hypotony as opposed to NPDS where the trabeculodescemetic membrane plays the major role in aqueous out-flow resistance, not being dependent on the tension of the scleral stitches. Further studies with larger population sizes are still needed to confirm these findings.

Financial Interest:

NONE