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Fact or fiction? A closer look at management options

Optometry Times JournalApril digital edition 2024
Volume 16
Issue 04

At-home devices challenge commonly held beliefs on IOP measurements, visual field testing, and imaging.

Glaucoma written as diagnosis on chart Image Credit: AdobeStock/VitaliiVodolazskyi

Image Credit: AdobeStock/VitaliiVodolazskyi

Glaucoma is a slowly progressive optic neuropathy and a leading cause of irreversible blindness worldwide. Findings from our progressive longitudinal studies have demonstrated that a leading risk factor is a number, the intraocular pressure (IOP). We use this number to diagnose, treat, manage, and change therapies, including surgical recommendations. However, we only collect a single number at a single time point and, in many instances, only once every 3 to 6 months. IOP fluctuates and is a volatile and dynamic number that is often higher in the early waking hours.1

IOP home monitoring

Findings from studies in a sleep laboratory have confirmed that IOP increases while sleeping and when in a supine position.2 People spend most of their sleeping time in a supine position and run the risk of having an IOP elevation without eye care professionals knowing the true maximum IOP or how these IOP spikes and fluctuations affect the patient’s disease and risk of progression. Furthermore, not all therapies work equally well at night and in the early waking hours, which is when these IOP spikes may be occurring. β-blockers, for instance, work well when taken in the morning but have minimal impact on IOP during the nocturnal period while prostaglandins show IOP lowering during both nocturnal and daytime periods.3 Selective laser trabeculoplasty (SLT) may have a higher likelihood of lowering IOP spikes based on findings from the 6-year LiGHT study showing less progression.4,5 Thus, the conventional belief that one can capture IOP variability in the office is pure fiction.

Furthermore, not all therapies control and flatten IOP equally, thus reducing the IOP fluctuations, which has in fact been found to be an independent risk factor for glaucoma progression in findings from our large landmark prospective studies.6 Similar to continuous glucose monitoring and home blood pressure devices, the fact is we can do much better with IOP monitoring by enabling and recommending at-home and beyond-the-office IOP devices such as the iCare HOME tonometer to our patients even earlier in the diagnosis and management process. In fact, thanks to the iCare Home tonometer, cases have been informed on next steps as well as which therapies are working to lower a patient’s IOP effectively through this device, hopefully prior to onset of retinal ganglion cell damage.7,8

Glaucoma practitioners and their patients currently have access to home IOP monitoring. The iCare Home2 device is available by prescription. Third-party entities such as MyEyes.net facilitate the rental process of iCare HOME to patients, taking the administrative, education, insurance requests, and training burden away from office staff. With proper use over a period of 1 week or longer, a much more complete IOP graph is documented. Data from the device can be collected in various ways, with or without sharing with the patient. This allows the provider to review the data, discuss with the patient, adjust treatment regimen as needed, and often even recommend surgery.7 Although iCare HOME is not universally covered by insurance at this time, there is ongoing work to achieve a Current Procedural Terminology and Durable Medical Equipment code that will help facilitate coverage. For the highly motivated patient, a purchase-to-own option is also available. In the future, implantable IOP sensors with 24-hour continuous monitoring may become available, thus further enabling us to identify and follow IOP variability so we can act sooner rather than waiting for damage to occur.7

Visual field testing

How do we determine whether to treat, change therapies, and/or recommend more invasive surgical procedures? We use a few devices to help us decide on next steps, and many of these devices may be moving beyond the clinic and into the realm of telemedicine. As a slowly progressive optic neuropathy, glaucoma affects the optic nerve and the retinal nerve fiber layer (RNFL) at the posterior segment of the eye. We can measure the function and structure of the optic nerve and the retinal nerve fiber using a visual field (VF) and optical confocal tomography (OCT), respectively.

The fiction is that OCT has replaced VF as a diagnostic. As clinicians, we still rely on the function of vision as measured by VF to help us determine a treatment plan for each patient. Our published literature and academy guidelines clearly state that patients should be receiving 1 to 3 tests in the first year of diagnosis, with yearly tests thereafter. Patients who are at high risk, have more rapid progression, and/or have high IOP should undergo 3 to 4 VF tests per year. In findings from a large retrospective cohort study, it was shown that in the US, 75% of patients with glaucoma are receiving less than 1 test per year on average and hence are not receiving adequate guidance-adherent glaucoma monitoring.9 Furthermore, findings from studies have demonstrated that testing reliability can be improved by more frequent testing.10

Virtual reality options, such as headset-mounted VFs, are becoming available for patients and providers, and may be an answer to more frequent testing while improving access to care, especially for those patients who must travel long distances or miss work so they can keep appointments. Although these methodologies and technologies are being studied in cross-sectional and normative databases, progression analyses as well as sensitivity and specificity data are currently lacking. Although the ergonomics are favorable and more comfortable, access to the test may be more likely and test time is shorter. Time will tell how these alternative VF tests compare with the gold standard of Humphrey.11

VF remains a viable and important assessment for glaucoma diagnosis and glaucoma progression. It provides valuable information on the functional impact of the disease, enables documentation of disease impact, and contributes to a comprehensive understanding of our patient’s condition.

OCT imaging

OCT has become a standard of care for assessing structural loss of RNFL and ganglion cell layer due to glaucoma optic nerve damage. When used early, OCT can show thinning preceding functional VF loss, thus enabling us to act earlier and preserve vision.

However, the belief that OCT imaging is always the most accurate and sensitive method for diagnosing glaucoma​ is fiction. In fact, upward of 36% of scans can have artifacts that confound a diagnosis. OCT can be affected and show artifacts due to user error and poor segmentation, the tear film, pupil size, lens changes, tilted nerves with extensive peripapillary atrophy, vitreous floaters, diabetic retinopathy, and the axial length (ie, myopia).12 When using OCT, we often forget that the normative database was created from a majority of eye with emmetropia from White adult eyes. Hence, the OCT readouts may not take severe myopia and/or racial differences into account. Furthermore, images showing red do not always signify glaucoma just as green imaging does not rule out glaucoma.

Lastly, as previously mentioned, it is fiction that OCT can replace the VF. High-quality OCT scans are critical for glaucoma diagnosis​, but they do not tell the full story. Use related maps to identify the characteristic patterns of disease,​ look for focal RNFL loss vs diffuse damage, use in conjunction with optic disc photos and VF,​ and be aware of non-glaucomatous retinal and cerebral masqueraders.

In summary, unmet needs remain in glaucoma management despite all the incredible advancements we have made over the years.13 Expanding to home diagnostics with a telemedicine approach can help with unmet needs such as improving glaucoma screening and management as well as improving and expanding diagnosis and monitoring to not only our local patients but those in rural and underserved communities.

  1. McGlumphy EJ, Mihailovic A, Ramulu PY, Johnson TV. Home self-tonometry trials compared with clinic tonometry in patients with glaucoma. Ophthalmol Glaucoma. 2021;4(6):569-580. doi:10.1016/j.ogla.2021.03.017
  2. Liu JH, Bouligny RP, Kripke DF, Weinreb RN. Nocturnal elevation of intraocular pressure is detectable in the sitting position. Invest Ophthalmol Vis Sci. 2003;44(10):4439-4442. doi:10.1167/iovs.03-0349
  3. Liu JH, Medeiros FA, Slight JR, Weinreb RN. Comparing diurnal and nocturnal effects of brinzolamide and timolol on intraocular pressure in patients receiving latanoprost monotherapy. Ophthalmology. 2009;116(3):449-454. doi:10.1016/j.ophtha.2008.09.054
  4. Gazzard G, Konstantakopoulou E, Garway-Heath D, et al; LiGHT Trial Study Group. Laser in glaucoma and ocular hypertension (LiGHT) trial: six-year results of primary selective laser trabeculoplasty versus eye drops for the treatment of glaucoma and ocular hypertension. Ophthalmology. 2023;130(2):139-151. doi:10.1016/j.ophtha.2022.09.009
  5. Awadalla MS, Qassim A, Hassall M, Nguyen TT, Landers J, Craig JE. Using iCare Home tonometry for follow-up of patients with open-angle glaucoma before and after selective laser trabeculoplasty. Clin Exp Ophthalmol. 2020;48(3):328-333. doi:10.1111/ceo.13686
  6. Musch DC, Gillespie BW, Niziol LM, Lichter PR, Varma R; CIGTS Study Group. Intraocular pressure control and long-term visual field loss in the Collaborative Initial Glaucoma Treatment Study. Ophthalmology. 2011;118(9):1766-1773. doi:10.1016/j.ophtha.2011.01.047
  7. Levin AM, McGlumphy EJ, Chaya CJ, Wirostko BM, Johnson TV. The utility of home tonometry for peri-interventional decision-making in glaucoma surgery: case series. Am J Ophthalmol Case Rep. 2022;28:101689. doi:10.1016/j.ajoc.2022.101689
  8. Rojas CD, Reed DM, Moroi SE. Usefulness of Icare Home in telemedicine workflow to detect real-world intraocular pressure response to glaucoma medication change. Ophthalmol Glaucoma. 2020;3(5):403-405. doi:10.1016/j.ogla.2020.04.017
  9. Stagg BC, Stein JD, Medeiros FA, et al. The frequency of visual field testing in a US nationwide cohort of individuals with open-angle glaucoma. Ophthalmol Glaucoma. 2022;5(6):587-593. doi:10.1016/j.ogla.2022.05.002
  10. Wu Z, Medeiros FA. Recent developments in visual field testing for glaucoma. Curr Opin Ophthalmol. 2018;29(2):141-146. doi:10.1097/ICU.0000000000000461
  11. Johnson C, Sayed A, McSoley J, et al. Comparison of visual field test measurements with a novel approach on a wearable headset to standard automated perimetry. J Glaucoma. 2023;32(8):647-657. doi:10.1097/IJG.0000000000002238
  12. Asrani S, Essaid L, Alder BD, Santiago-Turla C. Artifacts in spectral-domain optical coherence tomography measurements in glaucoma. JAMA Ophthalmol. 2014;132(4):396-402. doi:10.1001/jamaophthalmol.2013.7974
  13. Downs JC, Fleischman D; 2020–2022 Research Committee of the American Glaucoma Society and the 2020–2022 Glaucoma Clinical Committee of the American Society of Cataract and Refractive Surgery. Unmet needs in the detection, diagnosis, monitoring, treatment, and understanding of primary open-angle glaucoma: a position statement of the American Glaucoma Society and the American Society of Cataract and Refractive Surgery. Ophthalmol Glaucoma. 2022;5(5):465-467. doi:10.1016/j.ogla.2022.02.008
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