Researchers from Wills Eye Hospital in Philadelphia and Rutgers Robert Wood Johnson Medical School in New Brunswick, New Jersey, say that optical coherence tomography may still be useful in severe glaucoma cases.

The investigators note that retinal nerve fiber layer imaging done by OCT in glaucomatous eyes with advanced structural damage can reach a floor after which there is no further detectable thinning of the RNFL. They add that insurers are considering limiting coverage for OCT in “severe-stage glaucoma” as defined by CMS. However, CMS definitions of severe glaucoma are based primarily on visual field criteria, the authors say, adding that many of these patients may have preserved RNFL in other sectors.

In the study, researchers reviewed the records of patients with CMS-defined severe glaucoma, and collected data on such parameters as the average/sectoral RNFL thickness and the mean deviation of the visual fields. Previous estimates of RNFL floor and test-retest variability for Cirrus OCT were used to establish three threshold values for the RNFL. 

A total of 129 eyes qualified (age: 71 ±12 y; mean deviation: −13.5 ±4.3 dB; average RNFL: 60.9 ±7.9 µm). A majority of eyes (66 percent) met “severe” glaucoma criteria, with defects in both hemifields; 34 percent met only paracentral-defect criteria. The proportion of eyes that had significant remaining average, superior, or inferior RNFL, estimated by thresholds 1 to 3, was 21 to 54 percent, 29 to 51 percent and 16 to 37 percent, respectively. At least one vertical quadrant had significant remaining RNFL in 35 to 66 percent of eyes, depending on the threshold used.

The researchers say that their data demonstrate that the presence of CMS-defined severe glaucoma doesn’t exclude the potential utility of OCT for monitoring progression.

J Glaucoma 2020;29:4:241. 
Kolomeyer NN, Mantravadi Anand V, Brody G, et al. 


Impact of Glaucoma Surgery On the Cornea

Resarchers evaluated alterations in corneal biomechanical properties before and after conventional trabeculectomy and Ahmed valve implantation.

Thirty-nine eyes of 39 patients were evaluated retrospectively. Complete ophthalmic exams including evaluation of corneal biomechanical properties using the Ocular Response Analyzer were performed before and after six months postoperatively. The means four measurements-—corneal hysteresis (CH), corneal resistance factor (CRF), Goldmann correlated intraocular pressure (IOPg) and corneal compensated intraocular pressure (IOPcc) -—were recorded. Patients had undergone trabeculectomy or shunt surgery as the first surgical procedure and were on maximum glaucoma medication.

Twenty eyes of 20 individuals were in the trabeculectomy group and 19 eyes of 19 patients were in the Ahmed valve group. Some of the findings were: 

• No significant differences were found between the two groups in terms of glaucoma drug usage, preop mean deviation of Humphrey visual fields; CH, CRF, IOPcc or IOPg (p>0.05). 

• CH and CRF increased significantly after shunt surgery (p<0.001). 

• In the trab group, postoperatively the CH increased (p<0.001), while CRF slightly decreased, though not statistically significantly (p>0.05). 

• CH and CRF showed a greater increase after AGV surgery than after trabeculectomy surgery (p<0.05). 

• No significant correlation was found between IOP changes and CH-CRF changes in conventional trabeculectomy or AGV groups (p>0.05).

Researchers found that surgical technique differences may have an impact on postoperative corneal biomechanical outcomes. They also determined that AGV surgery offered better corneal biomechanical results than standard trabeculectomy at six-month follow-up.  REVIEW

Int Ophthalmol 2020; April 16 (epub)
Kaderli A, Demirok G, Tamer Kaderli S, et al.