Article

The Importance of Assessing Low Vision in Retina Practice

Retina specialists can help improve quality of life in patients with residual low vision.

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Of all ophthalmic diseases, retinal pathologies such as diabetic retinopathy and macular degeneration cause the clear majority of irreversible vision loss.1,2 Recent therapies such as intravitreal injections can prevent blindness and improve vision, but they often leave the patient with residual low vision.3 This growing population of treated retinal patients mandate that retina specialists be able to comprehend the needs and management of these low-vision patients.4,5

Treated retinal patients on average fall into the category of low vision, in contrast to the preinjection era, where most patients were legally blind. Low vision is defined as best corrected vision between 20/60 and 20/200 or visual field loss of less than 20 degrees in the better eye. Legal blindness is defined as 20/200 or worse vision or a visual field no greater than 10 degrees around central fixation.6

Manuel Paez-Escamilla, MD, is a research fellow at The Macula Center in Clearwater, Florida. Eric W. Deupree is a clinical coordinator and head technician at The Macula Center. Dana M. Deupree, MD, is a vitreoretinal specialist at The Macula Center. Michael J. Tolentino, MD, is a vitreoretinal specialist at The Macula Center. Dr. Tolentino reports advisory board membership with eSight. The remaining authors report no related disclosures. Reach Dr. Tolentino at mtolent88@me.com.

LOW VISION IN THE RETINA PATIENT

AMD is the leading cause of permanent visual impairment among the elderly in the western hemisphere.7,8 In the ANCHOR and MARINA studies, less than 20% of patients receiving ranibizumab had 20/200 vision or worse. Only 40% of patients retained 20/40 vision or better after 2 years. This leaves around 40% of patients with low vision.9 DR is considered the leading cause of new visual impairment cases among adults between 20 years and 74 years old in the United States.10 DME is the main cause of visual impairment for this population, whereas proliferative DR results in the majority of legal blindness.10,11 This shift in outcome will increase the retinal practice patient population that requires low-vision evaluation and management in the future.12

ASSESSING THE LOW-VISION RETINAL PATIENT

The assessment of visual function in the retinal population has centered primarily on VA, which demonstrates the greatest loss in late-stage retinal disease and is decreased in intermediate disease.13 Retinal disease in both early and late stages affects more than VA; it also affects shapes and contours of objects. Thus, in order to help patients with low vision, other measures of visual function such as dark adaptation (DA) and contrast sensitivity (CS) need to be assessed. Along with VA these other measures are directly correlated with performance of daily tasks. Improved performance on these tasks should be the primary purpose of therapy for retinal patients.

DARK ADAPTATION

Dark adaptation delay can reveal abnormalities in retinal disease and, in particular, AMD. The AdaptDx adaptometer (MacuLogix) is a test that is able to measure dark adaptation in the physician’s office. Studies found that DA testing can detect AMD before drusen are detected on clinical exam.13,14 Dark adaptation is an important measure of low-light (eg, nighttime) visual performance and can be affected even when VA is normal. With advanced AMD and other retinal diseases, DA delay is correlated with worsening disease.15 AdaptDx is a rapid and clinically useful assessment tool for the low-vision retinal patient.

CONTRAST CHARTS

Contrast chart measures the ability to distinguish between finer increments of light vs dark.4 This test measures visual function in situations of low light, fog, or glare (eg, night driving). Contrast reading performance is often decreased in patients with drusen even if they don’t report any visual symptoms. Late-stage disease correlates with greater decline in contrast sensitivity.16

THE HIPPOCRATIC OATH AND LOW VISION

Our specialty takes the preservation of vision as its paramount and primary goal, defining success in ophthalmology as: improvement of vision first, then preservation of vision, then preservation of the eye. These goals adhere to the Hippocratic oath taken by physicians, by which they vow to do no harm. This commitment is fulfilled by recognizing that the preservation of vision for the patient means the preservation of functional vision, or the ability to effectively apply the vision that is available to the performance of useful daily activities. Vision rehabilitation is recognized by Medicare as medically indicated for patients with central scotomas, VA of ≤20/70, or visual field loss.

THE SMARTSIGHT PROGRAM

The Smartsight Program program was established by the American Academy of Ophthalmology (AAO) to give ophthalmologists the ability to incorporate the medical model of vision rehabilitation into their individual practices. It is divided into 3 levels:17

  • SmartSight level 1, recognize and respond: with mild contrast sensitivity or VA <20/50, reassure normal daily function is possible and provide information.
  • SmartSight level 2, record, refract, recommend, and report: with moderate contrast sensitivity loss or VA <20/200, report patients to their internist or primary care providers. This level of vision loss puts their patients at risk for comorbidities like depression, falls, and Charles Bonnet syndrome.
  • SmartSight level 3, comprehensive vision rehabilitation: This level is for academic programs, large retina practices, and multispecialty groups. Patients benefit from extensive vision rehabilitation, in addition to low-vision devices or head-mounted displays.

LOW-VISION DEVICES

The field of low vision has been reliant on optical technologies like magnifiers and telescopes.2 These early devices may enhance task-specific VA (eg, reading, watching television, and driving), but they do not aid in enhancing contrast or night vision.18 Recent advances in video processing technology have allowed the development of head-mounted displays that offer versatility, mobility, enhancement of VA, dark adaptation, and contrast.19,20

MAGNIFICATION

Patient needs for magnification are individually unique and require an interdisciplinary clinical assessment and analysis. There are 3 types of magnification routinely employed in vision rehabilitation: angular (the image of an object is made to subtend a larger visual angle; ie, a telescope), relative distance magnification (reducing the distance between the object and the eye; ie, reading material at arm’s length is brought closer to the face), and relative size magnification (making the object larger; ie, larger text in printed material).

Spectacle Systems

The family of spectacle systems includes a wide variety of options that treat reduced VA, field loss, reduced contrast, and glare sensitivity. Spectacle-mounted systems offer the patient who has customary use of the eye with a hands-free option, they are unique in that they also are cosmetically acceptable.21

Spectacle-mounted telescopic devices are primarily used to treat reduced VA and are prescribed with tasks with a viewing distance of 10 feet or more; the maximum average tolerable magnification is 6x, but the device can also be modified for intermediate and near vision.22 These include Galilean telescopes such as the the Spiral Galilean Telescope (Designs for Vision, Inc.), the Beelcher bioptic telescope, reading telescopes mounted on regular glasses such as those by Ocutech, and the Eagle Eye telescope (Designs for Vision, Inc.).

Spectacle microscopic devices (high-plus lenses, such as the UniVision by Eschenbach Optik) are used to treat reduced near VA. They are best used for tasks in work distances of 2 cm to 30 cm.18,23 A microscope provides the largest field of view when compared with a telescope.

Telemicroscopic (reading telescope) systems are telescopes modified for nondistant use and are mostly used to treat reduced intermediate VA (30 cm to 100 cm).24

Electro-Optical Systems

Video magnification combines relative size and distance magnification and provides a range from 8x to 60x with a reasonable field of view and more normalized working distance. The best examples include closed-circuit television (CCTV systems) and low-vision enhancement systems (LVEs). Advantages of these systems include binocularity, wide range of levels of magnification, and color/brightness/contrast controls. Disadvantages include limited portability, necessity of a power source (electricity/battery power), and dexterity needed for manipulating controls. Due to these concerns, head-mounted displays (HMDs) were developed to compete with spectacle systems and to offer another alternative to the low-vision patient.25,26 Examples can be found in Table 1.

Table 1: Classes and Functions of Head-Mounted Displays
CLASS DESCRIPTION EXAMPLES FUNCTION LIMITATION
Retinal projection Head-mounted display that projects an image onto the retina Google Glass, Fujitsu Laser Headset Expansion of visual field difficult mobility, image projection not variable
Near-eye display Projects a transparent image in front of the eye Microsoft Hololens, Epson Moverio Expansion of visual field Task-specific, less versatile
Virtual reality Covers the eye and occupies the entire visual field Jordy by Enhanced Vision, Oculus Rift Enhancement of central vision, contrast sensitivity, and night vision Immersive and thus poor mobility
Bioptic tilt Enhances central vision but allows peripheral vision eSight Eyewear Enhancement of central vision, contrast sensitivity, night vision, and mobility Costly

HEAD-MOUNTED DISPLAYS

Head-mounted displays display an image in front of the user’s eyes through video displays. They are theoretically considered a portable CCTV device. A frontal camera captures live video, and embedded image processing software enhances visual information.27 An HMD provides hands-free vision enhancement, has the potential to improve visual search and nighttime travel in individuals with visual field loss.20,25 Several studies have shown an increase benefit of enhanced vision and task speed using HMDs vs typical optical low-vision aids in patients with macular vision impairment.28,29 What differentiates HMDs is the embedded image processing algorithms, the immersive or nonimmersive design, video capture to display latency, and ease of use (Table 1).

eSight Eyewear

eSight eyewear is a new HMD that is a class 1 medical device, registered with the US Food and Drug Administration, Health Canada, and the European Union directives on medical devices. What differentiates this device from other HMDs is its high-resolution 30 FPS video camera, which has virtually no latency from image capture to display.30 The image is displayed on 2 high-resolution OLED (800x600 pixels) screens placed in front of the user’s eyes. It subtends a visual field of 28 degrees width (35 degrees diagonal). If there is a scotoma in one eye but not in the other eye, the image in the good eye will fill in the scotoma in the other eye, thereby enhancing visual function (Figure 1). This nonstereo image presentation provides enhanced benefit in comparison to stereoscopic low-vision aids.

Figure 1. Binocular spectacle-mounted Galilean focusable telescopic system.

In this prospective trial, patients using eSight for the first time had significantly improved VA (0.74 ± 0.28 logMAR), contrast sensitivity (0.57 ± 0.53 log units), critical print size (0.52 ± 0.43 logMAR) and the Melbourne score of Low Vision Activities of Daily Living (ADL). While these numbers outperformed and were comparable to other HMDs, eSight eyewear improved facial recognition, which had not been demonstrated with other HMDs. Furthermore, its lightweight, nonimmersive, hands-free design and bioptic tilt capability (Figure 2) reduced some of the common side effects of immersive mobile HMDs, such as nausea or dizziness.

Figure 2. eSight eyewear.

These theoretical advantages were evaluated clinically in a multicenter prospective trial that analyzed the medium-term benefits of a lightweight head-worn vision enhancement device. The primary purpose of this trial was to measure the quality of life improvement in a 3-month frame, where 51 novice participants used eSight (Clinicaltrials.gov identifier NCT02616900). Data are expected to be published in the end of 2017.

Figure 3. Patient using eSight eyewear.

CONCLUSIONS

With the advent of anti-VEGF injections, retina specialists are preserving patients vision. However, vision recovered after treatment, while not considered legal blindness, is still considered low. And, in some circumstances, this low vision is not viable for everyday tasks. Because of the tremendous increase of patients with low vision in our offices, we need to identify this population and educate them about alternatives in treatment of irreversible low vision such as HDMs, which can help patients recover some independence. The eSight device can replace multiple low-vision devices, and it also can enhance facial recognition, which is critical to quality of life and not possible with other devices. Retina specialists are capable of halting blindness with injections, and with new technologies, they can also improve residual visual performance with low-vision devices. RP

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