Glaucoma is a group of eye conditions that can progressively damage the optic nerve and lead to irreversible sight loss. Because the most common form, primary open-angle glaucoma, may develop without noticeable symptoms in its early stages, timely detection and regular eye examinations remain central to protecting vision. Established assessment involves a combination of clinical tests, including intraocular-pressure measurement, optic-nerve assessment, visual-field testing, gonioscopy and, where appropriate, optical coherence tomography.
Against this background, Carolyn Aitken, an iridologist and optician based at The Lomond Clinic in Helensburgh, Scotland, undertook a community-based observational study exploring whether particular iris features might be associated with primary open-angle glaucoma.
The work arose from repeated clinical observations of distinctive iris markings in people who had already received a glaucoma diagnosis. Rather than presenting iris analysis as a replacement for ophthalmic examination, the study asked whether certain visible features might warrant further investigation as possible indicators of ocular or systemic risk.
Family history and predisposition: Is there a link?
Carolyn Aitken took a particular interest in glaucoma because of many cases in her family. Wanting to evaluate the genetic risk and if there were any indications in the iris that would show an increased risk of developing glaucoma, and perhaps, use preventative measures to reduce that risk based on iridology principles and conventional eye diagnosis.
It appears that there are indeed signs and markings associated with glaucoma.
From observation to investigation
The study used a cross-sectional observational design. Participants were recruited through a community clinic in Helensburgh and included adults over the age of 40 who volunteered to take part. The study group included people with a confirmed diagnosis of primary open-angle glaucoma, alongside an age-matched control group without known ocular pathology.
High-resolution iris photographs were taken and the images were then examined for a range of features, including:
Pigment distribution and colour variation.
Openings, rarefactions or apparent loss of structure within the iris fibres.
Changes in the collarette, the boundary between the pupillary and ciliary zones.
The overall shape of the iris.
The appearance of the pupillary border.
Vascular markings and patterns potentially associated with ocular circulation.
Additional information was recorded where available, including intraocular pressure, visual-field defects, glaucoma treatment, family history, driving status and relevant personal health information. The study also explored whether participants reported significant trauma or changes in quality of life around the time of their glaucoma diagnosis.
This combination of photographic observation and participant information was intended to identify possible associations between iris characteristics and features already recognised in glaucoma, such as optic-nerve damage, visual-field loss and altered ocular perfusion.
Abstract
This study investigates the potential link between nutritional deficiencies and glaucoma. Building upon previous clinical research linking iris colour variations to certain ocular diseases, this study explores how specific nutritional deficiencies highlighted by iris analysis techniques could provide insight into the specific essential mineral deficiencies that contributes to optic nerve damage. Recent advancements in high-resolution iris imaging and digital display technologies have enhanced the feasibility of using iris features for diagnostic purposes. Notably, specific iris characteristics, such as localised fibre openings or loss of substance, pigmented collarette and the presence of a dark circumferential band around the pupillary border known as shadow ring, have been associated with individuals diagnosed with glaucoma. While iris recognition focuses on the overall structure, iris analysis studies the local variations within specific regions of the iris. This research compares certain colour differences in irises of participants with and without glaucoma, highlighting the rapid, non-invasive diagnostic potential of this approach.
This Edited Volume, Glaucoma - Exploring Medical Therapies and Surgical Treatments, is a collection of peer-reviewed chapters that provide a comprehensive overview of recent developments in glaucoma research.
The book comprises single chapters authored by various researchers, edited by an expert in the field. All chapters are complete in themselves but united under a common research study topic.
This publication aims to provide a comprehensive overview of recent research by international authors in ophthalmology and to open new avenues for further development.
Features highlighted in the study
The chapter by Carolyn Aitken describes several iris characteristics that appeared repeatedly among participants with primary open-angle glaucoma. The most prominent was what the author terms a shadow ring: a dark circumferential band around the pupillary border, also known as the pupillary ruff.
The study also discusses an apparent lateral or almond-shaped bulging of the iris, a constricted or pigmented collarette, sectoral areas of reduced fibre density, unusual vascular markings and, in some cases, a greenish hue visible within the pupil. These observations are presented as potential areas for further investigation rather than as independently diagnostic signs.
The author links some of these observations with possible nutritional or circulatory factors, particularly zinc status, vitamin B3 metabolism and blood flow.
Nutritional mechanisms
A major theme of the study is the possible relationship between nutritional status and optic-nerve health. It discusses zinc in relation to retinal function, oxidative stress and retinal ganglion cells, and considers vitamin B3 compounds, including nicotinamide, in relation to mitochondrial function.
These mechanisms are biologically interesting. Retinal ganglion cells have high energy requirements, and mitochondrial dysfunction is an area of active glaucoma research. The chapter itself acknowledges, however, that direct clinical evidence linking vitamin B3 supplementation to correction of zinc deficiency or treatment of glaucoma remains limited and that further research is required.
This distinction is especially important for practitioners. Mechanistic plausibility can generate a valuable research hypothesis, but it does not demonstrate that supplementation will prevent glaucoma, reverse optic-nerve damage or replace established treatment.
The role of stress
Stress may be both a consequence of vision loss and a factor that influences ocular health. Research suggests that psychological stress can cause temporary rises in intraocular pressure, while prolonged stress may affect blood flow and the regulation of inflammatory processes around the optic nerve.
Sleep disruption, smoking, poor diet and physical inactivity may further compound risk, particularly when they accompany chronic stress.
“Pathophysiological mechanisms: recent research from the Vanderbilt Eye Institute suggests that the earliest signs of injury in glaucoma occur in the brain. Similar to neurodegenerative diseases such as Parkinson’s disease (PD), where neuronal damage begins in the distal projections through a process known as dying back, glaucoma appears to follow a comparable pattern.
In dying back, neuronal axons progressively lose their ability to communicate with their target structures. In the case of glaucoma, researchers have demonstrated that axons in the optic nerve lose connectivity with their projection sites in the midbrain.“
Specific Iris Characteristics
The study identified a group of iris features observed among participants with primary open-angle glaucoma (POAG). These included a shadow ringr, lateral changes in iris shape, a constricted pigmented collarette, sectoral fibre changes, unusual vascular markings and, in some cases, a greenish hue within the pupil.
— Shadow ring
The shadow ring was the most frequently observed feature. It appeared as a dark grey-to-black circumferential band around the pupillary border, also known as the pupillary ruff.
Within the iridology framework used in the study, the shadow ring is located in the area traditionally associated with nutrient assimilation and was linked to impaired zinc absorption. The chapter reports an 84.12% association from 5,121 cases, based on 4,308 cases in which zinc deficiency was confirmed through blood or urine testing or documented medical history. There may also be possible tissue atrophy in this region and the reported relationship between ocular pigmentation and zinc storage.
— Iris bulge
A second feature was an irregular, laterally bulging iris that appeared more almond-shaped than circular. The inferior portion of the iris appeared broader, while the superior area appeared flatter.
A light blue or white arc, described in the chapter as a lanula, was also observed on the sclera at the site of the bulge. The study records reported associations between the location of this arc and differences in heart rhythm, although these observations may need to investigated further.
The was also unusual vascular patterns in the bulbar conjunctiva. Small vessels appeared to extend towards the corneal limbus before looping back in an arc-like formation. This proposes that it may reflect altered ocular perfusion or a compensatory response to reduced blood flow.
— Pigmented, constricted collarette
The study also identified a pigmented and constricted collarette. In iridology, the collarette is interpreted in relation to autonomic nervous-system activity and digestive function, and this help associate a tight collarette with sympathetic dominance, prolonged nervous-system tension and possible digestive symptoms such as constipation or intestinal spasm.
Orange pigmentation within the collarette is typically discussed in relation to pancreatic function and possible adrenal stress. There seems to also be a relationship between a constricted endocrine-type collarette, adrenal activity and raised intraocular pressure.
— Sectoral shading and fibre changes
Another reported feature was sectoral shading, involving an area of reduced fibre density, sparse or thinning fibres, rarefactions or lacunae. The affected area appeared darker because the underlying iris base became more visible.
This finding was observed at approximately the 3 o’clock position in the left iris, corresponding to the heart and lung zones on the iris chart. The appearance may reflect altered circulation, weakened vascular integrity or reduced nutrient and nerve supply.
— Green hue within the pupil
A greenish hue was observed inside the pupil in some participants with glaucoma. Since the pupil normally appears black because light is absorbed by the retina, there may be several possible explanations, including changes in the lens, corneal transparency, retinal reflectivity or light scatter from structures affected by glaucoma.
Participants who had recently undergone cataract surgery did not display this feature. The study proposes that future research should compare this observation with optical coherence tomography, fundus imaging, retinal nerve-fibre-layer measurements and optic-nerve findings.[intechopen]
Comparison with controls
The study compared participants with POAG with an age-matched group without glaucoma. The glaucoma group displayed the full combination of reported features, including the shadow ring, lateral iris bulging, pigmented and constricted collarette, sectoral shading and, in some cases, a green pupil.
Some isolated findings were also present among control participants. These included minor iris-shape irregularities, corneal arcus, a green hue in at least one eye and sectoral shading in the heart and lung zones. However, the control group did not display the complete combination of signs and markings.
Interpretation for iridologists
For iridologists, the study presents a proposed pattern. The central observation is that several features appeared together in the participants with POAG:
A dark shadow ring around the pupillary border.
Lateral or almond-shaped bulging of the iris.
A pigmented and constricted collarette.
Sectoral fibre rarefactions or shading.
Unusual conjunctival vascular markings.
A possible greenish reflection within the pupil.
Mostly present in light-blue iris (however, may reflect the widespread of blue iris types in the region).
The study also recorded that many participants described heightened stress, feeling overwhelmed or corresponded to a traumatic event around the time of diagnosis. The shadow ring is interpreted, within behavioural iridology, as a possible accomplishment ring associated with mental tension, fear of failure, persistent worry and pressure to complete tasks.
Limitations and clinical boundaries
The design cannot determine whether any iris characteristic precedes glaucoma, develops as a consequence of the disease or simply occurs more frequently in the particular group studied. It also cannot establish whether the reported features would remain reliable when assessed by independent observers using blinded image analysis.
Further research would need to include:
Larger and more diverse participant groups.
Clear diagnostic criteria confirmed by ophthalmic records.
Blinded assessment of iris images.
Multiple independent image assessors.
Predefined criteria for each iris feature.
Statistical analysis of sensitivity, specificity and predictive value.
Control for age, ethnicity, iris colour, medication, ocular surgery and coexisting eye disease.
Longitudinal follow-up to determine whether features appear before clinically detectable glaucoma.
Independent replication by researchers who were not involved in the original study.
Without this validation, iris features cannot be used to diagnose glaucoma or to reassure someone that glaucoma is absent or that they are genetically predisposed to develop glaucoma.
Why the research deserves attention
The study is relevant to integrative practitioners and iridologists because it explores a possible interface between traditional iris observation, digital imaging, nutritional hypotheses and conventional glaucoma assessment. It also demonstrates how a practitioner-generated clinical observation can be developed into a formal research question.
Its importance lies less in claiming that glaucoma can now be diagnosed from the iris and more in opening a conversation about whether some observed features can be defined, measured and tested objectively.
Accessing the research
Carolyn Aitken’s peer-reviewed chapter, “Identifying Risk Factors for Glaucoma through Iris Images,” is freely available through IntechOpen:
Carolyn Aitken has also written a book expanding on the research and its background in iridology, available in paperback and digital formats through Iris Patterns and Glaucoma.
