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Role of Optometrists in Glaucoma Workup

by | Jan 1, 2023 | Manuscripts | 1 comment

Demi Janet E, B. Optom

Fellowship in Optometry, Aravind Eye Care System, Chennai, India

 

According to the World Health Organisation (WHO), glaucoma is a group of eye diseases that can cause vision loss and blindness by damaging a nerve in the back of your eye called the optic nerve.

Comprehensive examination

Every optometrist should perform a comprehensive eye examination. During comprehensive eye examinations, optometrists assess much more than visual acuity.

The primary eye examination includes an assessment of all eye conditions like cataracts, retinal disease, optic neuritis, etc.

The comprehensive eye exam includes a series of tests

Figure 1: Comprehensive examination
(Image courtesy: https://www.optometrists.ab.ca/web/AAO/Doctors/Role_of_Optometrists/AAO/Doctors/Role_of_Optometrists.aspx?hkey=f3a68490-1950-46ee-ab3c-dad2ebef8326)

 

Table 1: Components of history taking in a glaucoma workup (1-3)

a History Taking Several risk factors can easily be ruled out through a proper history taking. For any patient with sudden or gradual vision, this information should be important

  • Demographics data
  • Presenting complaint
  • Location: unilateral or bilateral
  • Onset: gradual or sudden loss of vision
  • Progression: gradual or sudden loss of vision
  • Associated factors: like pain or painlessness, visual phenomenon like haloes, flashes of light.
  • History of previous episodes
  • History of trauma
b Ocular Symptoms To investigate the vision status whether it is gradually or progressively decreased and then interrogate the associated symptoms like redness, irritation pain, or painless vision loss. Commonly irritation of the ocular surface will present in glaucoma because of topical therapy.
c Past ocular history Any laser surgeries, Prior to trauma, usage of Anti glaucomatous medication is important to the initial evaluation. Patients with pseudophakia will likely have an open angle if the Intra-ocular lens (IOL) implant is in the posterior chamber of the eye. In the case of an Anterior chamber, IOL implant it is important to check for anterior chamber angle status to avoid a rise in Intra Ocular Pressure (IOP)
d Past medical history History of neurological, blood pressure, diabetic, cardiac, and pulmonary require more consideration
e Family history Now-a-days glaucoma is very common, but you may be at higher risk if it runs in your family. To educate patients and their family members to know what glaucoma is and understand the disease progression.

Table 2: Diagnostic tests in glaucoma (1-3)

a Central corneal thickness (CCT) CCT plays a very important role in diagnosing glaucoma

  • It masks the real value of intraocular pressure
  • CCT has a predictive role in OH and NTG patients
  • Normal CCT is about 545 m

Note: Thin corneas put the patient under greater risk
b Anterior chamber depth
  • If the peripheral anterior chamber depth is one quarter or less of the width of the corneal thickness, then a referral should be considered
  • Patients with an occludable angle should be referred to an ophthalmologist for further investigation.
c Applanation tonometry More than one reading should be taken to confirm if the patient has high IOP.
Various types of tonometer:

  • Goldmann tonometer
  • Perkins tonometer
  • Tonopen
  • I care
  • Pneumotonometer

Among these, the Goldmann tonometer is considered the Gold standard according to the AAO.
d Gonioscopy
  • A closed and blocked angle may be a possible sign of acute glaucoma.
  • Acute angle closure should be referred to as soon as possible
e Dilated fundus examination
  • Examining the optic disc is a major key to diagnosing glaucoma easily.
  • Examiner should carefully look at the shape and depth and centration of the cup
  • The normal cup to disc ratio (the diameter of the cup divided by the diameter of the whole nerve head or disc) is about 1/3 or 0.3.

While a cup-to-disc ratio greater than 0.5mm is an independent risk factor for glaucoma.
ISNT rule

  • The ISNT rules the rim width, which decreases in the order of inferior (I) > superior (S) > nasal (N) > temporal (T).
  • Normally the neuro-retinal rim is thickest inferiorly and thinnest temporally.
  • In glaucoma you notice a vertical thinning, with atrophy along the inferior and superior rims. If the optic nerve does not follow the ISNT rule, it may have had glaucomatous damage.
  • We can take fundus photographs of the patient on every visit, so we can easily compare the health of the optic nerve in follow-up exams.
f Humphrey Visual Field
  • Also known as perimeter, to check your entire field of vision is just to see if any damage to your peripheral vision.
  • When assessing visual fields, it is important to think of early glaucomatous field defects usually present as nasal steps, paracentral scotomas, arcuate bundle scotomas, or temporal wedges.
g Optical Coherence Tomography (OCT)
  • Once the patient was confirmed or in the state of glaucoma suspected on the very first visit. We can advise taking an OCT to judge any damage to the optic nerve and nerve fibre layer.
  • While macular scans have shown clinical utility in detecting early glaucoma, RNFL thickness changes are more readily detected due to the faster rate of RNFL loss in glaucoma progression. (1-3)

Referring patients

Once the optometrist performs all investigations into glaucoma, the patient should be referred to an ophthalmologist for further evaluation. Ophthalmologists will confirm your diagnosis and find out how much the condition has developed and the disease progressed.

Refer a patient immediately to an ophthalmologist if you suspect acute angle-closure glaucoma, it is an emergency. If it is not treated early, it can lead to permanent loss of vision.

Table 3: Categories in glaucoma referral (4)

Category 1: Seen within 30 days Category 2: Seen within 90 days Category 3: To be seen in 1 year or 365 days
Intraocular pressure:30 to 35 mmHg Intraocular pressure :
>28mmHg < 30 mmHg without optic disc damage or visual field loss		 Intraocular pressure:
> 22 mmHg – < 28mmHg,
with any of the following:
Central Corneal Thickness < 555 High-risk medicine, History of trauma, Pseudo exfoliation, high myopia
Severe optic disc damage Early disc damage or field loss with consistent with glaucoma
Severe visual field defect Suspect narrow iridocorneal angle with risk of angle closure glaucoma

Conclusion

Glaucoma is  an irreversible blinding disease and every optometrist, no matter what country he/she works in, should be trained to recognise, evaluate and correctly refer to a glaucoma specialist for proper treatment and monitoring.

 

References:

  1. Glaucoma tests: What to expect &amp; how to interpret results. Cleveland Clinic. (n.d.). Retrieved August 30, 2022, from https://my.clevelandclinic.org/health/diagnostics/22514-glaucoma-tests
  2. Understanding the role of optometrists. (n.d.). Retrieved August 30, 2022, from https://www.optometrists.ab.ca/web/AAO/Doctors/Role_of_Optometrists/AAO/Doctors/Role_of_Optometrists.aspx?hkey=f3a68490-1950-46ee-ab3c-dad2ebef8326
  3. Kyari F, Philippin H, Shah P, Faal H, Babayo S, Abdull M. Counselling in a glaucoma care service. Community eye health. 2021;34(112):47.
  4. The State of Queensland; jurisdiction=Queensland. (2020, January 24). CQ Health: Glaucoma referral information for GPS. Queensland Health. Retrieved August 30, 2022, from https://cpc.health.qld.gov.au/Condition/133/glaucoma

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