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Editors Selection IGR 10-3
Response
Comment by David Greenfield on:
59604 Short-Term Enhancement of Visual Field Sensitivity in Glaucomatous Eyes Following Surgical Intraocular Pressure Reduction, Wright TM; Goharian I; Gardiner SK et al., American Journal of Ophthalmology, 2015; 159: 378-85.e1
See also comment(s) by Ivan Goldberg • Kaweh Mansouri • Shamira Perera •We are grateful to the reviewers for their positive comments regarding our study. The concept of visual field (VF) improvement following intraocular pressure (IOP) reduction has existed for decades.1 In clinical practice there are patients that describe subjective improvement in vision after glaucoma surgical intervention, which has often been dismissed by physicians given widespread disbelief that such improvement may occur. The growing body of evidence2,3 demonstrating enhancement of visual function after IOP reduction supports electrophysiological data using pattern electroretinogram4 and offers promise for the development of biomarkers of RGC function for use in research trials and clinical practice.
We describe a statistical method for identifying repeatable improvement in VF test locations using a glaucoma change probability strategy. At present, commercially available VF testing algorithms for glaucomatous change detection are engineered soley to detect progression. For example, the Glaucoma Progression Analysis™ (GPA, Carl Zeiss Meditec, Dublin CA) was introduced in 2004 and employs statistical criteria to compare VF locations on the pattern deviation probability map of follow-up VF exams compared to the average of 2 baseline exams. An automated analysis identifies progressing test locations that show change greater than the expected variability in pattern deviation (at the 95% significance level). Improving VF test points are not identified using GPA software. However, it is interesting to note that an earlier generation of change detection software entitled Glaucoma Change Probability™ (GCP, Carl Zeiss Meditec, Dublin, CA) did identify statistically “improving” test locations on follow up VF exams compared to baseline, but confirmation was not required.
Our study, along with others, demonstrates that short-term improvement in visual function does occur after IOP reduction in glaucomatous eyes. Dysfunctional RGCs may represent a viable treatment target for glaucoma, and biomarkers should be identified to measure both biological improvement and deterioration in RGC function. Although long-term data is necessary, as described by the reviewer, this data may “encourage clinicians to offer glaucoma patients cautious words of hope that some degree of loss may be recoverable.”
References
- Spaeth GL. The effect of change in intraocular pressure on the natural history of glaucoma: lowering intraocular pressure in glaucoma can result in improvement of visual fields. Trans Ophthalmol Soc U K 1985;104(Pt 3):256-64.
- Caprioli J. Glaucoma: a disease of early senescence. Invest Ophthalmol Vis Sci 2013;54:ORSF60-7.
- Musch DC, Gillespie BW, Palmberg PF, et al. Visual Field Improvement in the Collaborative Intitial Glaucoma Treatment Study. Am J Ophthalmol 2014;158:96-104.
- Sehi M, Grewal DS, Goodkin ML, Greenfield DS. Reversal of retinal ganglion cell dysfunction following surgical reduction of intraocular pressure. Ophthalmology 2010;117:2329-36.
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