August 2012
Volume 53, Issue 9
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Letters to the Editor  |   August 2012
Comparative Resilience of Clinical Perimetric Tests to Induced Levels of Intraocular Straylight
Investigative Ophthalmology & Visual Science August 2012, Vol.53, 5748. doi:10.1167/iovs.12-10445
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      Marta Gonzalez-Hernandez, Manuel Gonzalez de la Rosa; Comparative Resilience of Clinical Perimetric Tests to Induced Levels of Intraocular Straylight. Invest. Ophthalmol. Vis. Sci. 2012;53(9):5748. doi: 10.1167/iovs.12-10445.

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      © ARVO (1962-2015); The Authors (2016-present)

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IOVS, in the March 2012 issue, published an article by Justyna D. Oleszczuk, Ciara Bergin, and Eamon Sharkawi, 1 which concludes that Pulsar perimetry is affected by the levels of intraocular straylight, as is conventional perimetry (standard automatic perimetry [SAP]), as opposed to Moorfields motion displacement test (MDT). 
The authors wrote “Gonzalez-Hernandez et al. found that thresholds for central and peripheral visual field were higher for PP (Pulsar) than conventional perimeters. They also suggested PP would not be significantly affected by aging.” 
Neither of the two sentences is true. The abstract cited by the authors 2 clearly states: “The difference between the thresholds in the central and peripheral visual field was higher than in conventional perimetry. This difference was particularly increased in the nasal field. The results for CP-SW, CP-K6W and CP-T30W were respectively: mean sensitivity (MS) for 20 years 25.8, 25.3 and 24.7 src; loss per year 0.099, 0.08 and 0.09 src.” In the text, these results are clearly graphically illustrated. 
So, what we say is that the sensitivity topographic slope is pronounced in Pulsar, as corresponds to an examination involving spatial resolution. Regarding the sentences that follow in that article, it is well known that Octopus establishes a reduction of 0.065 dB/year for SAP. We therefore affirmed, 11 years ago, that with Pulsar perimetry, there is a notable reduction of sensitivity with age. This is, therefore, not something that the authors have discovered, and the reduction is adequately compensated for in the results provided by the instrument. 
We personally believe that a diagnostic procedure that is not sensitive to age does not guarantee its sensitivity. On the contrary, age produces an unquestionable functional deterioration, therefore a diagnostic procedure that is not able to detect it does not seem to have greater diagnostic sensitivity than another that does. 
The conclusion of the authors, namely, that Pulsar results are altered by intraocular straylight causing image blurring, is not a remarkable discovery; rather, it is quite obvious. A test like Pulsar, involving the capacity for spatial resolution, must necessarily be affected by reduced visual acuity, because that is precisely the essence of the biological function of spatial resolution capacity. 
In another study by our group, 3 which the authors do not cite, we indicated that with Pulsar the results “are reduced when inappropriate refraction is worn” and to take this effect into account “the instrument shows a visual acuity test just before each examination.” 
In the manual on Pulsar (document provided by Haag Streit, Int., König, Switzerland, to the evaluators of the Pulsar perimeter prototype), we wrote the following: “Pulsar T30W can be affected if visual acuity is not good, 0.85 src for every tenth (0.1) units of visual acuity.” This was experimentally demonstrated during the design and evaluation phases of the instrument, and for this reason, it incorporates a procedure to measure the patient's visual acuity with stimuli similar to those used during the examination. 
We do not disagree with the results of the study, but we would stress that false comments about our work are unacceptable, and the authors should not present obvious, well-known aspects as if they were novel findings. Above all, they should have commented on the really important question relating to the clinical use of the test, which is its capacity to diagnose and analyze progression, taking into account the patient's age and visual acuity. In this regard, we believe the authors should have included some comments on clinical results, not only ours but those of other independent groups in recent publications. 4,5  
The fact that a particular test is not affected by image blurring does not guarantee its clinical utility. Other procedures based on temporal phenomena, such as flicker perimetry, are also unaffected by image blurring but have proved to be of very limited clinical utility for various reasons, mainly because they require a complex response that is not easy for many patients to produce, and because they do not provide a useful graduation of the progression of the defect. We, therefore, believe that the discussion fails to include a number of important considerations, which would give a better idea of the true clinical impact of what the authors found and not simply leave the reader with a falsely negative impression. 
References
Oleszczuk JD Bergin C Sharkawi E. Comparative resilience of clinical perimetric tests to induced levels of intraocular straylight. Invest Ophthalmol Vis Sci . 2012;53:1219–1224. [CrossRef] [PubMed]
Gonzalez-Hernandez M Rios A Rodriguez M de la Rosa M. Combined spatial resolution and contrast perimetry in normal subjects. In: Wall M Mills RP eds. Perimetry Update 2000/2001 . The Hague, The Netherlands: Kugler Publishing; 2001:109–114.
Gonzalez-Hernandez M Gonzalez de la Rosa M Rodriguez de la Vega R Hernandez-Vidal A. Long-term fluctuation of standard automatic perimetry, Pulsar perimetry and frequency-doubling technology in early glaucoma diagnosis. Ophthalmic Res . 2007;39:338–343. [CrossRef] [PubMed]
Salvetat ML Zeppieri M Tosoni C Parisi L Brusini P. Non-conventional perimetric methods in the detection of early glaucomatous functional damage. Eye . 2010;24:835–842. [CrossRef] [PubMed]
Zeppieri M Brusini P Parisi L Johnson CA Sampaolesi R Salvetat ML. Pulsar perimetry in the diagnosis of early glaucoma. Am J Ophthalmol . 2010;149:102–112. [CrossRef] [PubMed]
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