Glaucoma is the second leading cause of blindness after cataracts and is the leading cause of irreversible blindness, with an estimated burden of 8.4 million people bilaterally blind from glaucoma worldwide in 2010.1 It is predicted that due to the changing demographics and increased life expectancy there will be a significant increase in the number of glaucoma patients worldwide. More than 90% of glaucoma patients are unaware of the disease in the South Indian population.2,3 There should be an emphasis on a comprehensive ocular examination including gonioscopy for proper case detection and treatment of primary angle closure disease (PACD).4 Identifying and differentiating the type of glaucoma based on gonioscopy and optic disc assessment requires sound clinical experience.

There is a pressing need for eye care professionals at the community level as the ophthalmologist to population ratio is 1:25,000 and 1:219,000 in urban and rural areas of India, respectively. The number of ophthalmologists located in urban areas is 70% despite the fact that only about 23% of the population of India reside in towns and cities.5 Optometry training in India involves 3 years of theory classes and a year of clinical internship in a tertiary eye care centre. After completion of graduation most of the optometry students prefer to undergo a clinical fellowship at the L V Prasad Eye Institute for an year, where the fellows are trained in each and every subspecialty area. India currently has approximately 9000 4-year trained optometrists and needs 115,000 Optometrists in order to address an estimated 456 million people of India's population (of 1.12 billion people total population) who require vision correction (spectacles, contact lenses or refractive surgery) to perform the daily living and 26 million people are blind or visually impaired due to any eye disease. A further 133 million people, including 11 million children, are blind or visually impaired simply from lack of an eye examination.6

Considering the fact that most people are unaware of the presence of glaucoma or its status as one of the major diseases affecting public health, a population based detection strategy is more likely to be effective than individual focussed collective responsibility. In this scenario the availability of suitably trained personnel other than ophthalmologists, such as optometrists, can play a key role by engaging in public health disease detection activities.7,8

This approach fits into the eye care delivery model advocated by of the L V Prasad Eye Institute whereby a focussed examination conducted close to the home location of the individual results in the identification of suspected specific pathologies. This can then initiate an efficient referral process to confirm the diagnosis and administer the appropriate treatment within a reasonable time frame. It also helps developing the communication with fellow eye care professionals.9 As reported in previous studies on shared care for glaucoma diagnosis, highly motivated and skilled community-based optometrists with good agreement are safe, clinically effective and reliable local resources in providing a convenient and appropriate shared care of glaucoma patients.10,11 Myint and associates reported that a shared competency-based approach enables a coordinated training and development model for all professionals involved in glaucoma detection and management.12

To become an integral part of the glaucoma team, optometrists need to acquire the skills required for detecting the designated diseases. It has been shown in various studies that optometrists have a high level of agreement with the reference standard specialist ophthalmologists in glaucoma detection by optic disc examination and management.13,14 To the best of our knowledge, there are no reports on the agreement between optometrists and glaucoma specialists in gonioscopic evaluation of the angle.

The primary goal of this study is to establish the sensitivity and specificity with which the two experienced optometrists can detect glaucomatous changes using gonioscopy and optic disc assessment relative to the gold standard ophthalmologists diagnosis.

The LVPEI pyramidal model for eye-care delivery that is advocated by the World Health Organization (WHO), at the lowest level of the pyramid is a vision center managed by a vision technician. Primary–secondary interface exists between the primary care services at the vision center and secondary care services at the service centre. Each vision center caters to a population of 50,000.15 (Fig. 1)

Figure 1.

Multi-tiered interlinked eye-care delivery model.

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The study was conducted in the outpatient department of the L V Prasad Eye Institute, Hyderabad, India itself. The study was approved by the ethics committee of the L V Prasad Eye Institute and was conducted according to the tenets of the Declaration of Helsinki. Informed consent was obtained from all the participants.

Three glaucoma specialists with experience ranging from 8 through 23 years and 2 optometrists who had been working with the same specialists for over 7 years in the Glaucoma department of a tertiary eye care centre were available for this work. During this time between 5000 and 9000 glaucoma patients were examined and managed by the ophthalmologists. Both the optometrists performed gonioscopy and optic disc assessment on over 2000 patients while gaining experience in the assessment and management of patients with glaucoma along with the same glaucoma specialist ophthalmologists.

The data were collected prospectively while following the standard proforma of patient examination.

Separate cohorts of subjects were evaluated for agreement in gonioscopy and optic disc interpretation by both optometrists. Optometrist 1 performed gonioscopy in 72 subjects (male:female=41:31). Mean (±standard deviation) age of these subjects was 53±12 years (Range=25 to 80). Optometrist 2 performed gonioscopy in 77 subjects (male:female=46:31). Mean age of these subjects was 50±18 years (Range = 18 to 84).

Optometrist 1 performed optic disc evaluation in 94 subjects (male: female=59:35). Mean age of these subjects was 48±15 years (Range=18 to 74). Optometrist 2 performed optic disc evaluation in 100 subjects (male: female=60:40). Mean age of these subjects was 48±15 years (range, 18 to 80).

Tables 1 and 2 show the agreement between glaucoma specialist and each optometrist separately for gonioscopy and optic disc evaluation. κ was 0.92 for agreement between glaucoma specialist and optometrist 1, and 0.84 for agreement between glaucoma specialist and optometrist 2 in interpretation of gonioscopy. κ was 0.90 for agreement between glaucoma specialist and optometrist 1, and 0.89 for agreement between glaucoma specialist and optometrist 2 in interpretation of optic disc.

Tables 3 and 4 show the diagnostic accuracies of each optometrist separately for gonioscopy and optic disc evaluation. Gonioscopic evaluation by optometrists had sensitivities and specificities both above 90% to discriminate open from occludable angles. Positive and negative likelihood ratios were significant enough to have large effects on the post-test probability of having occludable angles. Optic disc evaluation by optometrists had specificities greater than 95% to discriminate normal from glaucomatous discs while the sensitivities were 83% and 93%. Positive and negative likelihood ratios were significant enough to have moderate to large effects on the post-test probability of having abnormal optic discs.

Our results show that there is a high level of agreement between the expert glaucoma specialists and the experienced optometrists. In a situation where over 50% of the persons in developing countries with OAG are unaware that they have the disease,20 this method of training optometrists in gonioscopy and optic assessment can be expected to have a significant impact because it has the potential to make a larger cohort of diagnostically capable individuals available in locations where there is the greatest need. However, our main purpose is to compare the glaucoma trained optometrists and glaucoma specialist ophthalmologist, such that the results can be used to validate the use of the same glaucoma trained optometrists in the LVPEI-GLEAMS.

Various studies have shown that higher rates of visual impairment and blindness are associated with lower economic status and older age and these groups are commonly found in rural areas and in developing countries. As visual acuity assessment alone misses most cases of glaucoma and screening field tests can be ineffective, 21 the need for a more complete evaluation of each individual is evident.

Our results differ from those of Jampel and associates who found poor concordance between glaucoma experts in assessing disc change over time. The observers in that study were not trained however.22

There have also been agreement studies where photographs (stereo or non-stereo optic disc images) or direct ophthalmoscopic assessments were shown to ophthalmologist or optometrists with poor to moderate intra and inter observer reliability being the result. Again however varying levels of experience existed among the various observers23,24 and when clinical documentation of the optics discs through dilated pupils using a stereoscopic viewing system was used, intra-observer agreement improved.24 This approach helped evaluate subtle, early changes to the neuroretinal rim and the retinal nerve fiber layer.

Optic disc appearance has been suggested as the best reference standard for glaucoma diagnosis at present, despite the fact that it suffers from less-than-perfect inter observer agreement.22 Furthermore, standards of Preferred Practice Patterns stress the importance of including a range of appropriate examination techniques like gonioscopy, imaging and visual field tests during examination and diagnosis. While many physicians perform visual field tests and optic disc imaging, they frequently fail to assess the angle by gonioscopy.25 Hence, it has been recommended that vigilant examination of the optic disc and gonioscopy should be maintained during routine evaluation.20

The uniqueness of the current study lies in the involvement of gonioscopy, as listed in the UK NICE guidelines, April 2009 as essential competence for those providing glaucoma care26 and our data provide the first assessment of the diagnostic accuracy of the trained optometrist in this regard.

One limitation of the current study was that for logistical reasons it was not possible to assess agreement among the three glaucoma specialists. The assumption that there exists substantial agreement cannot be formally verified. In conclusion, our results show that there is a high level of agreement between glaucoma specialists and trained optometrists in gonioscopy and optic disc assessment. We suggest that the reason for the significantly higher agreement than has been reported previously is the fact that both optometrists had high levels of glaucoma patient experience gained from working with same consultants for many years. As a consequence they were able to develop judgement criteria similar to those of the supervising consultant ophthalmologists. This suggests that the optometrist with good experience and clinical skills, if trained in optic disc assessment and gonioscopy, can appropriately diagnose glaucoma using these indicators. This adds to and reinforces previous work demonstrating similar results based on the assessment of the optic disc. In situations where glaucoma specialist ophthalmologists are unavailable for whatever reason, we propose therefore, that it would be reasonable to utilize optometrists to facilitate the screening and diagnosis of glaucoma, provided that they have been suitably trained and have access to the appropriate equipment.

The authors have no conflicts of interest to declare.