APOD is a term that describes a fully automated facial and eye recognition WiFi enabled handheld camera that serves as a sophisticated diagnostic assistant for the optometrist, contact lens optician and ophthalmologist. Currently the most advanced APOD in terms of functionality is the Volk Eye Check which has been reviewed in the past.1,2

Figure 1: Volk Eye Check in use

Advantages of an APOD

An APOD device (such as the Volk Eye Check) is simple to use and allows the practitioner to:

  • Take photographs of patient’s face (usually three pictures required)
  • Immediately display automated clinical measurements on the camera screen
  • Generate a pdf and jpeg data sheet that is received via email on the practitioner’s PC, laptop, tablet or phone device
  • Print or save the pdf/jpeg to the patient’s record

The Volk device has three clinical modules available, all of which additionally produces mediGrid which will be described below.

Contact lens module

The contact lens module provides the optometrist or contact lens optician with an intelligent clinical assistant, enhancing the contact lens fitting process while significantly improving efficiency.3 The device has been described independently as a tool to aid presbyopic lens fitting4 and to assist the fitting of tinted contact lenses.5

Figure 2: Documenting change of strabismus amplitude in different directions of gaze in a case of Duane syndrome

Measurements possible and relevant to contact lens practice are:

  • Horizontal visible iris diameter – HVID helps to pinpoint the best fitting contact lens for your patient.6 Approximately 25% of patients have ocular measurements, particularly HVID, that fall outside the ranges associated with the parameters of standard fitting disposable lenses. The measurement of corneal diameter is very important for contact lens fitting. Knowing which patients may need more attention in advance will save time.
  • Sagittal depth Ω SAG supports a better fit than K-values alone.7 Having entered keratometry readings onto the device before taking the photographs, the device will calculate SAG from the K readings and HVID and inform the practitioner whether a standard lens may be chosen; or alert the practitioner to the likelihood that a custom lens may be required. This artificial intelligence is called Best Fit Analysis (BFA) and is particularly valuable for soft, semi-scleral and scleral lens fitting.
  • Pupils Ω maximising visual acuity with multifocals depends on accurate pupil measurements.8 Measurements of pupil size and eccentricity are important for multifocal lens fitting. Most pupils are positioned eccentrically within the iris.9 The BFA has the facility to automate the design of the optimum multifocal parameters for each patient based upon HVID, pupil size and pupil eccentricity and keratometry readings as well as predict difficulties that are likely to occur again chair-time.

Practitioners tend to follow one of two protocols when using the contact lens module:

  • Screening every patient prior to fitting.3
  • Problem solving and complex fittings. Some optometrists use the device to solve issues of a poorly fitting lens; for designing multifocals or bifocal lenses; and fitting Ortho-K; scleral and semi-scleral lenses.

Figure 3: Photograph illustrating difficulty in detecting clinically significant anisocoria

An APOD device is individually programmed to advise the practitioner what lenses to choose from the list of manufacturers used by that practice. A list of lenses is produced in pdf format to accompany the data sheet received. For patients with regular eyes, the standard daily and monthly lenses fitted by the practice will be listed.

Figure 4: Showing patient with anisocoria (R < L) in bright ambient light secondary to neck surgery

For the significant minority of non-standard eyes, a list of custom lens types and parameters (BOZR; TD) will be suggested. Rather than wasting valuable chair-time trying to fit these patients with standard designs, the practitioner simply forwards the BFA details to the custom lens manufacturer and reschedules the patient for a fitting appointment with lenses of the correct fit and power. For multifocal lens designs, the BFA can provide very precise parameters including the size of the centre-near or centre-distance zone.

Table 1: Some causes and associations of acquired Horner and management advice

A number of specialist contact lens manufacturers have fitting algorithms integrated into the BFA system including Bausch + Lomb Specialty Vision Products HP toric and sphere, Astera Multifocal Toric, NovaKone; and CVue toric, sphere, and multifocal design contact lenses. Other lens manufacturers and products included in the BFA algorithms include Extreme H20 (Excel Speciality Contacts), SpecialEyes and MarkEnnovy.

Table 2: Summary of some possible causes of Horner in the presence of pain

Practice management outcomes

Introducing an APOD has implications for practice management:

  • Enhanced patient satisfaction due to more efficient and optimised fitting. The optometrist or CLO will inform those patients whose eyes are not ideally fitted with standard lenses before inserting any lenses that it is likely custom designed lenses will be required. Patients are better informed in advance and the time wasted in trialling more than one or multiple lens designs is pre-empted.
  • Increased revenue for the practice from custom lenses with protection from loss of revenue due to online contact lens suppliers. Practitioners tend to fit more custom design lenses leading to improved patient satisfaction while protecting their own business from online contact lens suppliers which do not supply theses lenses.
  • Enhanced cost effectivity because of saved chair-time. Using the device enables a clinical assistant to reliably commence contact lens fitting, saving the practitioner chair-time, streamlining lens choice and, in a significant percentage of single vision and multifocal lens fittings, enables optimum lenses to be ordered without going through time consuming lens trials.
  • Optimising profitability of standard lens dispensing. Standard lenses (such as dailies) can be ranked in terms of profitability. The order of listing can be changed as desired to allow multiples to recommend to their fitters which should be the lens of first choice when more than one standard lens is available.

Eye Check module

The Eye Check module may be considered to be a screening module. It produces 17 data including pupil size; difference in pupil size; measurement of eye position (automated Hirschberg test for strabismus); HVID; eye lid position (documentation of ptosis); pupil eccentricity and IPD.

Figure 5: pdf output documenting 0.27mm anisocoria in bright ambient light

Figure 6: Showing increase of anisocoria to 0.37mm in dimmer lighting.

The pdf data sheet lists the results in a display that includes a red-green scale with red alerting the optometrist to data that falls outside the normal distribution.

Protocols for using the Eye Check module include;

  • Screening every patient – some optometrists carry out a screening session as part of the routine pre-screening for all or most patients. The red-green display serves to alert the optometrist about anything that might require further investigation. For example, if there is clinically significant anisocoria further tests may be required.
  • Specific investigations where precise measurements are diagnostically valuable.

Clinical findings of relevance available using an APOD are;

  • Strabismus Ω the automated Hirschberg test forms part of the Eye Check analyses and is invaluable for screening for strabismus in babies and infants. An off-centre near target provides a stimulus to accommodation and increases significantly the sensitivity for detecting strabismus as compared to central fixation.10 Sensitivity for detecting horizontal strabismus has been shown to be about 80% and internal studies have reported specificity of greater than 90%.11 Strabismus can be documented objectively in different directions of gaze and to demonstrate to parents the effect of spectacles on accommodative esotropia. A number of behavioural optometrists around the world have found this facility to be very useful in the management of their patients.
  • Pseudostrabismus Ω in the presence of pseudostrabismus, caused for example by persistent epicanthus, it can be challenging to explain to a parent that while the baby or young child appears to have strabismus, conventional tests such as the cover test show the eyes to be straight. Documentary evidence from an automated device that has a sensitivity of greater than 80% and specificity greater than 90% is reassuring to the parent and is documentary evidence to support the optometrist’s diagnosis.
  • Pupil size and anisocoria Ω in most practices, a large proportion of the population have very darkly pigmented irides and optometrists and ophthalmologists will have difficulty in assessing pupil size. Indeed, it is likely that many optometrists when assessing very dark eyes are in the habit of recording in their notes the acronym PERLA in which the ‘E’ stands for ‘equal’ when, in truth, they are guessing that the pupils are equal in size.

The prevalence of anisocoria (>0.40mm difference in pupil diameters) is reportedly between 10% and 19%12-14. It is therefore a common finding but, while in most cases there is no active disease, it is most important that the presence of anisocoria is noted and the practitioner considers the finding in the context of symptoms (eg did the patient mention headaches), other signs (eg ptosis on the side of the smaller pupil) and the possible need to decide on additional tests (eg visual fields).

Figure 7: Conjunctival pigmentation documented with mediGrid iPhone 6. Small squares are 1mm in size. This pigmented lesion requires regular monitoring

mediGrid

Horner syndrome – Horner syndrome occurs when there is disruption of the oculosympathetic pathway, leading to ipsilateral miosis, lid ptosis and facial anhydrosis (lack of sweating).15,16 A smaller size pupil in the presence of ipsilateral ptosis is suggestive of Horner syndrome. The reduced innervation to Müller’s muscle of the superior and inferior eye lids will cause ptosis of the upper lid and an ‘upside-down ptosis’ of the upper lid giving a reduced palpebral aperture on that side.

Figure 8: Junctional melanosis of eye lid margin. This pigmented lesion requires regular monitoring

On the same side, innervation to the sphincter dilator is affected causing the pupil to be smaller than that of the fellow eye with the pupil not dilating normally in dimmer illumination. Horner syndrome, while not common, will be seen by optometrists in general practice as an incidental finding related to a benign cause. However, it occasionally may be a manifestation of a serious and life-threatening disorder17 (see table 1). In the presence of a newly presenting suspected Horner, careful questioning regarding symptoms and history is required.

Figure 9: Suderiferous cyst documented before referral for excision

The presence of heterochromia will support the likelihood that the Horner syndrome is longstanding. To help confirm that a lesion is longstanding, the optometrist can ask to see old photographs of the patient to determine the presence of ptosis or anisocoria. If the affected iris is blue and the other is brown, the lesion most likely was present at birth or during the first two years of life. The effect will not be present in blue-eyed patients. Patients can easily send photographs via email for assessment.

Figures 10 & 11: Heterochromic iris and associated conjunctival/scleral pigmentation in a seven-year-old girl. Although the bulbar pigmentation was longstanding, the iris finding was new and patient was referred

A previously undetected Horner syndrome found incidentally at a routine eye examination of a baby or child should be referred for ophthalmological investigation. If the child is otherwise asymptomatic this may be treated as a routine referral. If the presenting complaint was the ptosis or anisocoria referral should be more urgent.

Figure 12: Pigmented lesion (15cm x 11 cm) on forehead of 27-year-old male

The optometrist may have noted anisocoria or a ptosis during the initial eye examination or may have been alerted by the Eye Check screening flagging up a ‘red’ result. While pharmacological agents (including apraclonidine) can be used to confirm Horner,20 these are not widely employed by optometrists. In the presence of ptosis on the same side as the smaller pupil, to confirm diagnosis of Horner, the Eye Check session may be repeated in a different lighting level. In the presence of Horner, if for example, a session is repeated in a dimmer lighting level then the unaffected pupil will dilate more than the affected pupil thus producing a change in the size of anisocoria.

Figure 13: Marginal eyelid naevus. This lesion requires regular monitoring

Having confirmed diagnosis, the optometrist is in a position to come to a patient management decision (table 3).

Table 3: Overview of referral advice for Horner syndrome

  • Interpupillary distance Ω automated measurement of the IPD is most helpful used with babies or very young children with high degrees of ametropia for whom an accurate IPD is otherwise difficult to obtain.
  • Eye lid position Ω The Volk Eye Check data includes ‘MRD’ which denotes the distance (D) from the eye lid margin (M) to the corneal reflex (R). MRD 1 is the measurement for the superior eye lid and MRD 2 for the lower eye lid. Palpebral aperture is also listed in the pdf output. As discussed previously, the presence of ptosis can be a sign of Horner syndrome.

Oculoplastics module

The Oculoplastics module provides not only MRD 1 and 2 but automated measurements of upper and lower lid positions at the nasal and temporal limbus. Ophthalmic surgeons in the UK utilise these measurements together with the results of Humphrey 76-point visual field screening to determine whether ptosis surgery is required and whether such surgery is deemed clinically necessary or ‘cosmetic’. Including the pdf report containing the MRD data with a referral letter can be helpful to ophthalmologists in cases of ptosis and thyroid eye disease.21

In addition to producing pdf data reports, each of the Contact Lens, Eye Check and Oculoplastic modules produce high resolution jpeg images of the patient’s eyes overlaid with an accurate 1mm grid. This has a wide variety of uses including measuring the position of edges and bifocal segments during contact lens fitting and documenting eye and lid lesions that require monitoring or referral. Pigmented lesions (which are common) do require monitoring for changes in size. Figures 7 to 13 illustrate the use of mediGrid which is also additionally supplied to all Volk Eye Check users if they want to have the facility on their smartphone. mediGrid is also available as a standalone iPhone App.

Dr Simon Barnard is in private practice in London and the chief medical officer of IRISS Medical Technologies Ltd a partner of Volk Optical.

Acknowledgments
The author wishes to acknowledge the review of Horner syndrome by Barder CM (2016).

References

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21 Barnard S and Repucci G (2016). Our experience with an automated photo-ophthalmic device for measuring MRD. IV International Course of Orbitoplastics Surgery, Praiano, Italy October 7 and 8, 2016.