5.1 Overview

Optical coherence tomography (OCT) is a computerized imaging modality which is commonly used to diagnose and manage glaucoma, as well as other conditions in the eye. OCT imaging of the optic nerve, peripapillary retinal nerve fiber layer (RNFL), and macula are frequently employed for glaucoma patients.

As described in accompanying chapters, characteristic findings on OCT imaging of the optic nerve and RNFL include thinning of the neuroretinal rim following the inferior-superior-nasal-temporal (ISNT) rule rule, with inferior and superior quadrants affected earliest, followed by nasal, and finally temporal, in the course of glaucoma progression (Chapter 3). Characteristic findings on OCT imaging of the macula include losses in the ganglion cell layer, inner plexiform layer, and nerve fiber layer, and are often in an arcuate shape on thickness maps (Chapter 4). The structure–function correlations between the optic nerve head and visual fields that are characteristic of glaucoma are also demonstrated between structural OCT findings and functional automated visual field findings (Chapter 6). There are several widely used commercially available devices. Although the data from the devices are not directly interchangeable, they have been shown to have comparable diagnostic capabilities (Chapter 7).

Case examples illustrating the range of glaucoma severity are provided to show the reader how OCT is used in the clinical management of real-world glaucoma patients.

5.2 Early (Preperimetric) Glaucoma

The first case example (Fig. 5‑1) shows images from a 59-year-old African-American woman who has been followed for 4 years as a glaucoma suspect. Her intraocular pressure (IOP) has been in high teens to low twenties in both eyes with a central corneal thickness in the mid-400s. Her visual fields are full. The OCT demonstrates normal RNFL thickness and ganglion cell analysis.

The next case example (Fig. 5‑2) shows the visual field and OCT image from the left eye of a 65-year-old African-American man with primary open-angle glaucoma (POAG). Based on the American Academy of Ophthalmology Preferred Practice ¹ guidelines, the stage is mild due to optic nerve changes in the setting of a full visual field.

An example of a patient with progression on OCT testing is shown in Fig. 5‑3. OCT images from a 56-year-old white woman with preperimetric glaucoma in the left eye shows RNFL thickness thinning temporally in the left eye, with progressive temporal thinning over 12 years of follow-up, seen also on the macular progression analysis. The patient was not tolerant of topical medications and has been observed off treatment. Visual field testing remains full in both eyes.

5.3 Mild-to-Moderate Glaucoma

Fig. 5‑4 shows a case of a 62-year-old white woman with normal tension glaucoma in her left eye. She received one treatment of selective laser trabeculoplasty (SLT) at the time of initial diagnosis and is currently on topical pressure lowering therapy. Her vision is 20/20 with corrective lenses with an IOP of 13 mmHg. Her examination is notable for 1+ nuclear sclerosis, and she has a cup to disc ratio of 0.5 with inferior temporal sloping. The OCT demonstrates inferotemporal thinning corresponding to the superior Seidel’s scotoma, which can later develop into a superior arcuate scotoma if her glaucoma were to progress.

The next example (Fig. 5‑5) is a case of a 48-year-old Korean man with normal tension glaucoma in the left eye. Central corneal thickness measurements are normal, 583 OD and 592 OS. He is myopic (−9.50 −0.25 at 30 OD; −9.75 −1.00 at 180 OS), with long axial lengths (24.87 mm OD, 27.84 mm OS). Baseline IOPs were 11 to 14 mmHg OD and 12 to 14 mmHg OS. He is currently treated with topical pressure lowering therapy in the left eye, with recent readings of 11 mmHg OD and 12 mmHg OS. The OCT of the optic nerve demonstrates superior greater thinning than inferior and the OCT of the macula demonstrates thinning of the superior and inferior macula. The visual field demonstrates inferior greater than superior nasal depressions on the pattern deviation analysis.

A case of a 71-year-old white man with pseudoexfoliation glaucoma of the left eye is shown in Fig. 5‑6. This patient is status post combined cataract extraction and mitomycin C (MMC) trabeculectomy of left eye. His vision is 20/25–1 with corrective lenses with an IOP of 16 mmHg. His examination is notable for a superior bleb, pseudoexfoliation material on the anterior capsule, and a cup to disc ratio of 0.6. The OCT demonstrates superior and inferior thinning. The visual field demonstrates an inferior arcuate defect that spares central fixation. He is being treated with topical pressure lowering therapy.

A case of a 40-year-old Korean man with normal tension glaucoma in both eyes is shown in Fig. 5‑7. Central corneal thickness measurements are normal, 582 OD and 587 OS. He is myopic (−7.75 −0.25 at 160 OD; −6.75 −1.00 at 180 OS), with long axial lengths (27.12 mm OD, 26.77 mm OS). He is currently treated with topical pressure lowering therapy in both eyes, with recent readings of 13 mmHg OU. The OCT of the optic nerve demonstrates superior and inferior thinning with relative sparing of the nasal quadrant. The OCT of the macula demonstrates diffuse thinning of the maculae with an area of relatively preserved macular thickness superiorly in the right eye. The visual fields demonstrate nasal defects superiorly and inferiorly with early arcuate extension OS, and superior nasal defect with inferior arcuate defect OD.