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Stereophotos, SD-OCT, SAP similarly detect glaucomatous optic neuropathy
Stereophotographs often match the findings of spectral domain optical coherence tomography and standard automated perimetry for detecting early signs of glaucomatous optic neuropathy, researchers reported.
One eye of 100 glaucoma patients or suspects and 62 healthy subjects were tested with macular and disc SD-OCT scans and 24-2 and 10-2 standard automated perimetry (SAP). Two glaucoma specialists, meanwhile, analyzed the fundus stereographs of the same eyes.
Clinical signs of glaucomatous optic neuropathy (GON) were defined as vertical cup-to-disc ratio (VCDR) of greater than 0.6; inter-eye VCDR asymmetry of greater than 0.2, small disc with significant cupping, optic disc pit, focal and diffuse neuroretinal rim thinning, disc hemorrhage, b-zone peripapillary atrophy, nasal cupping, violation of the “ISNT” (inferior rim greater than superior greater than nasal greater than temporal), and focal and diffuse retinal nerve fiber layer loss.
Multivariate analysis showed a statistically significant difference between the clinical signs of GON found in glaucoma patients and glaucoma suspects as compared with normal eyes.
VCDR of greater than 0.6 was the most common feature, present in 92% of glaucoma eyes, 70% of glaucoma suspects and only in 3% of false positive healthy eyes. Violation of the ISNT rule was the second most significant sign, present in more than 80% of glaucoma or glaucoma suspect eyes and 5% of false positive controls. Close correspondence was found with the classification based upon visual field and OCT results.
“The classification of GON features on stereophotographs can differentiate healthy eyes from those with glaucoma or suspected glaucoma as defined based on SAP and SD-OCT abnormalities,” the authors concluded.
However, further follow-up might be necessary in some of the eyes to differentiate false positives from early signs of the disease. – by Michela Cimberle
Disclosure: Alhadeff reports no financial disclosures. Please see the study for the other authors’ financial disclosures
Perspective
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Good old stereo photographs of the optic nerve have been getting short shrift lately. For many, optical coherence tomography is the structural glaucoma test of choice.
Interestingly, studies of OCT for glaucoma have used photos as the comparative gold standard. Alhadeff and colleagues have decided to turn the tables and see if photo analysis is an accurate way to identify OCT and visual field-defined glaucoma patients and suspects. Not surprisingly, they found that disc photo analysis can differentiate glaucoma/suspects from healthy patients.
Allow me to list a few reasons why you should still acquire stereodisc photos:
--Careful photo analysis will develop your clinical skills and make you a better doctor;
--Hedge your bets, as there are many rule exceptions in glaucoma. I’ve often diagnosed glaucoma based on photographic evidence of change when OCT suggested stability; and
--You won’t see a disc hemorrhage with your OCT, and you’ll see many on photos that you miss on exam.
In 1985, Quigley suggested that it was silly (not his word) to forgo field testing until structural damage had occurred just because structural damage tends to precede functional loss. Now, as then, we need all means at our disposal in order to meet the challenge of glaucoma diagnosis and management.