Response to comments on: Validating tablet perimetry against standard Humphrey Visual Field Analyzer for glaucoma screening in Indian population.

Dear Editor,

We thank the readers for their letter commenting on our manuscript.[12] The study design is not a prospective cohort as understood by the reader. Careful inspection of scientific literature will show that prospective cross-sectional is a common term (PubMed-MEDLINE search shows 63,515 results[3]) that illustrates different aspects of study design, “prospective” indicates that the data were collected after the study was designed (direction), “cross-sectional” indicates a single frame of reference (time point) or how many times the data were collected, while “observational” indicates the type of intervention.[4]

We agree with the original STROBE guideline statement that authors of the guideline mention that ‘manuscripts should not be “STROBEd”, in the sense of regulating style or terminology. We agree to the use of narrative elements, including the description of illustrative cases, to complement the essential information about their study, and to make their articles an interesting read.‘[56]

We thank the readers for pointing out the error in the description for [Figure 2] and apologize for the same. It should be read as SITA FAST.

Regarding the MRF, the application is only available on the iPad/iOS devices which is only around ¼ of the global mobile operating system market, although in the tablet segment the share is around ½.[7] The lite application (now available in multiple formats as MRF glaucoma/neural/macula/diabetes on the Apple store) offers limited functionality and costs around 600 USD (License fee: 270 USD, 100 Test pack: 330 USD).[89] We believe, for a resource-limited setting in developing nations like a government hospital or a peripheral (semiurban/rural) primary or secondary care setup, these are significant costs especially with the recurring expenditure on the test packs. Despite the availability and affordability aspects of the paid application, if the results are as good as the traditional perimeters, it may be the game-changer that glaucoma management needs.

For the clarification on refractive correction, all subjects wore their prescription glasses for the VFE test. In addition, all subjects had best-corrected visual acuity better than or equal to 20/40 to undertake the VFE test. For the room illumination: LED light: 22 W, color temperature: 6500 K and lumens: 1900 Lm was used in the room without daylight to minimize glare. We agree that use of a tablet hood like the one provided with the new MRF app variant could improve the patient experience and test reliability.[9] We also agree with the suggestion that use of a Bluetooth keyboard/mouse would eliminate the need to clean the device again and again, thus test reliability and user experience would improve. We are using both the tablet hood and the Bluetooth keyboard with the MRF test.

These are exciting times for innovations in how glaucoma is diagnosed and managed across the world, especially during these COVID times. With new technology and concepts like tablet and VR perimetry, it is imperative that initial interest and buzz around them would lead to widespread adoption/adulation however it is important to highlight that robust comparison data with existing gold standards is vital before any of them replaces the trusted HVF in the glaucoma toolkit.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.