Investigation Of Risk Factors That Precede Primary Open Angle Glacoma

Primary open angle glaucoma (POAG) is characterized by progressive degeneration of the
retinal ganglion cells, resulting in optic nerve atrophy with visual field defects. The
biological basis of POAG is not fully understood.
This thesis covers two studies. The aims for Study 1 were to investigate the risk factors of
glaucoma in a population aged 18 years to 40 years. These were investigated by a
retrospective study of intraocular pressure measurements and optic nerve assessments (cup
to disc ratio) in two groups. One group had a family history of glaucoma and a second group
was without a family history of glaucoma. The aims for Study 2 were to investigate whether
the risk factors for primary open angle glaucoma were present many years before glaucoma
develops. These were investigated with a retrospective review of intraocular pressure
measurements and optic nerve measurements in participants who subsequently developed
primary open angle glaucoma.
Each study collected anonymised retrospective data from community optometry clinics for
extraction and analysis of data on intraocular pressure measurements and optic nerve
assessments. Study 1 collected one data entry per case. Study 2 collected ten years of
historical data from each clinical visit from clinical records of participants prior to their
diagnosis/treatment of glaucoma. This data spanned 33 years. For each glaucoma record,
data for a similar period were obtained from a case-matched control record.
The results for Study 1 are that mean intraocular pressure measurements and optic nerve
head assessments in young adults aged between 18 years and 40 years did not differ
significantly in cases with a family history of glaucoma compared with a group without.
For Study 2, the correlations of intraocular pressure and optic nerve cup to disc ratio indicate
an increase in values over a 10-year duration for cases that subsequently developed
glaucoma as compared to case-matched controls. Analyses conducted at 5 and 10-year time
points for mean intraocular pressure and median optic nerve cup to disc ratios prior to
POAG diagnosis were statistically significantly different (p<0.05). Visual field data were collected for all the cases and descriptive data showed that pre-diagnosed cases had more
reported suspicious visual field defects.
The principle findings of this thesis are that there are pre-glaucomatous changes up to ten
years before glaucoma diagnosis and that this may have considerable relevance for models
of glaucoma aetiology. It also highlights the important role that community optometrists
play in guarding the borders between pre-glaucoma and glaucoma.