Central Visual Field Defects in Glaucoma

“Tamasa ma jyotirgamaya” / “Lead me from darkness to light”
Brihadaranyaka Upanishad 1.3.8
circa 7th-6th BCE Sanskrit
philosophical text

Glaucoma is a leading cause of irreversible blindness, making early detection
and management crucial. Protecting central vision is the ultimate goal of glaucoma
treatment, yet common visual field tests often overlook early signs of central visual
field defects (CVFDs), which can sig-nificantly impact the quality of life for glaucoma
patients. This book offers a comprehensive guide to understanding CVFDs at all stages
of glaucoma, from early detection to advanced cases, providing cutting-edge insights
into the detection, diagnosis, and management of CVFDs gleaned from the latest scientific
data as well as clinical practice.

Poor detection and underrating of central defects and their progression may cause
severe vision loss, even in patients with suspected or early glaucoma, which affects
the quality of care from the outset of disease. Hence, the detection of CVFDs is
essential in the diagnosis and management of glaucoma even at the earliest stages.
There are no accepted standard guidelines for detecting progression in advanced
glaucoma with central defects. Therefore, a better understanding of the patterns
of CVFDs and their development over time is crucial to improve the management of
glaucoma.

This book is primarily written for the use of practicing ophthalmologists and
optometrists as well as young trainees in these disciplines who will be at the forefront
of glaucoma care in the near future. Eye care specialists who seek an overview of
the basic principles may choose to read the first 4 chapters of this book to understand
CVFDs in glaucoma. The first 2 chapters lay the foundation for understanding the
types of glaucomatous visual field defects and comprehending CVFDs in early glaucoma.
Chapter 1 presents one of the most difficult subjects in glaucoma for all ophthalmologists:
classification of visual field abnormalities in highly myopic eyes without pathological
change. Underlining the relationship between retinal ganglion cell loss and visual
field loss varies depending on the stage of the disease, Chapter 3 focuses on the
structural techniques and functional tests employed to diagnose glaucoma. The combination
of optical coherence tomography and visual field testing is beneficial for disease
monitoring, as it allows more frequent detection of disease progression than using
either method alone. The chapter then zooms into the evaluation of the struc-ture-function
correlation of the 24-2 and 10-2 visual field tests with macular ganglion cell layer/inner
plexiform layer thickness, explaining the most salient concepts with schematic models
and specifying the relative vul-nerability zones of the optic disc to early glaucomatous
damage. Chapter 4 discusses the limitations of the 24-2 visual field test to adequately
estimate central visual field damage in the early stages of glaucoma.

Current glaucoma staging systems to measure the disease severity are discussed
in Chapter 5, which makes it an ideal primer for young trainees in residency and
optometric training programs.

Chapter 6 attempts to solve the riddle of whether glaucomatous CVFDs can be evaluated
by both 24-2 and 10-2 tests as well as the utility of 10-2 tests for evaluating
CVFDs in early glaucoma. The long-term debate about whether 10-2 testing detects
any additional defects not identified in 24-2 testing is central to this chapter,
which explores two questions. How and why would a 10-2 visual field test pattern
be a better instrument for recognizing CVFDs? Does the 10-2 visual field test provide
sufficient additional information to the 24-2 visual field test to warrant its routine
use in the evaluation and management of early-stage glaucoma? Chapter 7 touches
upon how the severity of central damage can be assessed and predicted by these two
tests (24-2 and 10-2) and provides a point-based analysis of the visual field in
addition to the factors related to abnormal 24-2 visual field points responsible
for the presence of parafoveal scotomas on the 10-2 visual field. The chapter in
question is integral to Chapter 6 and as companion chapters, they will hopefully
guide clinicians to successfully predict the severity of CVFDs.

Chapters 8 to 10 navigate established and novel methods of evaluating the visual
field to detect glaucomatous damage. In routine clinical practice, using a single
test to evaluate both the central 10° area and the total 30° visual field simultaneously
for detecting glaucomatous damage is a useful tool. The scope of testing the central
and peripheral visual field separately is limited as it demands extra time and cost.
In this respect, is the new 24-2C a better choice to end these debates, or is the
Octopus G1 program the only solution? Another burning and controversial issue is
whether the 24-2C test strategies—with extra central test locations—included in
the new Humphrey Field Analyzer 3 (ZEISS) show enhanced ability to improve the detection
of central defects over the standard 24-2 visual field.

Is the SITA Faster algorithm a better alternative than the SITA Standard algorithm,
even after abandoning the blind spot catch trial and false-neg-ative catch trial?
Chapter 9 delves into this issue while also outlining the interpretation of 24-2C
test results as well as the evolution of the SITA Faster paradigm and its potential
benefits and limitations. Chapter 10 offers a primer on the Octopus perimeter, focusing
specifically on the detection and interpretation of CVFDs by means of its G1 program.

Chapter 11 contains an in-depth discussion regarding the modes and methods of
characterizing and classifying central visual field loss in advanced glaucoma. Crucial
factors such as how to evaluate disease progression in advanced-stage glaucoma on
the 24-2 and 10-2 visual field tests, the characterization and classification of
central visual field loss in advanced glaucoma, central visual field loss patterns
and their shifts in advanced glaucoma, and the impact of filtration surgery on CVFDs
in advanced glaucoma complete the book’s final chapter.

On a personal note, I especially wish to recognize my year-long (2019–2020) Fulbright-Nehru
Academic and Professional Excellence Fellowship at the Hamilton Glaucoma Center,
University of California San Diego, CA, United States, for enabling me to study
CVFDs in glaucoma. It was a rare privilege for me to have interacted with stalwarts
in the field during this Fellowship period. I wish to thank my host faculty, Professor
Linda M. Zangwill (Professor of Ophthalmology, Co-Director of Clinical Research,
and Director of the IDEA at the Hamilton Glaucoma Center), who helped me immensely
in understanding this subject.

It is difficult to adequately express my gratitude to Professor Robert N. Weinreb
(Chair and Distinguished Professor of Ophthalmology, Director of the Shiley Eye
Institute, and Director of the Hamilton Glaucoma Center), who always answered my
queries, however insignificant, and inspired me to probe and think about the questions
raised in this book. I record my most sincere thanks to Kugler Publications, and
particularly Mr. Simon Bakker, its Managing Director, for kindly publishing my manuscript.
I would like to express my sincere gratitude to Ms. Silvia Sanchez Di Martino of
Kugler Publications, who considerably helped improving the manuscript.

Dr. Tutul Chakravarti, MBBS, DO, DNB
Eye and Glaucoma Care, Kolkata, India
January 2025

Glaucoma affects almost 100 million individuals worldwide and it is the leading cause of irrevers-ible blindness. More than half of such individuals are undiagnosed; in some areas of the world, this figure climbs to more than 80% of individuals who go undiagnosed and are unaware they have glaucoma. Ten million individuals are blind in at least 1 eye from glaucoma. So many more individuals have impairment of vision that impact their performance of daily activities. In part, this stems from the failure to diagnose as well as the failure to detect disease worsening in patients with existing glaucoma. With earlier diagnosis and detection, it is presumed that more timely management would reduce disease worsening and possible blindness. So how will a knowledge of central visual filed defects make a difference and lead to improved diagnosis and management?

Despite improvements in imaging and their interpretation, detection of visual field abnormalities remains the most widely used method for diagnosing and monitoring glaucoma. Although glaucomatous visual field defects can occur throughout the entire visual field, they are typically only tested within the central 24° or 30°. However, central visual field defects often are detected before peripheral ones. And for patients with existing glaucoma, a central visual field defect will often demonstrate worsening prior to a peripheral one. Thus, it follows that testing of the central visual field should be an essential part of glaucoma evaluation.

Despite a formidable body of research demonstrating the importance of testing the central visual field for glaucoma evaluation, it is often omitted by clinicians. However, this practice needs to change. With a clear exposition of the accumulated knowledge of central visual field defects and their testing, Tutul Chakravarti provides the background for stimulating its use by clinicians everywhere. Her explanations of the rationale for central visual field testing are thorough. Moreover, throughout the book she provides practical examples of its application that should resonate with all clinicians caring for glaucoma patients. Surely, this is a book that should be read by all such clinicians!

Despite the imminent emergence of novel testing methods (e.g., virtual perimetry,) and analytics (e.g., deep learning strategies) for visual field testing, it seems certain that the foundational importance of testing of the central visual field will endure. If not already done, therefore, central visual field testing should be implemented without delay into one’s clinical practice for glaucoma management!

Robert N. Weinreb, MD
Director, Shiley Eye Institute
Distinguished Professor and Chair of Ophthalmology
Distinguished Professor of Bioengineering
Morris Gleich MD Chair of Glaucoma
Director, Hamilton Glaucoma Center
University of California San Diego

Chapter 1: Types of glaucomatous visual field defects

Chapter 2: Understanding central visual field defects in early glaucoma

Chapter 3: The structural aspect of detecting glaucomatous macular damage

Chapter 4: The 24-2 visual field test underestimates central visual field defects

Chapter 5: Current glaucoma staging systems underestimate disease severity in eyes with central visual field defects

Chapter 6: The utility of the 10-2 visual field test for the evaluation and management of central defects in early glaucoma

Chapter 7: Prediction of 10-2 defects by central 24-2 defects

Chapter 8 24-2C: A new modality of the Humphrey Visual Field Analyzer

Chapter 9: The evolution of SITA-Faster: its benefits and limitations

Chapter 10: Detection of central visual field defects with the Octopus G pattern

Chapter 11: Central visual field defects in advanced glaucoma