PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 7448139

Photogrammetry experiments with a model eye.

A R Rosenthal·D G Falconer·I Pieper
View original source ↗Export metadata ↓

Abstract

Digital photogrammetry was performed on stereophotographs of the optic nerve head of a modified Zeiss model eye in which optic cups of varying depths could be simulated. Experiments were undertaken to determine the impact of both photographic and ocular variables on the photogrammetric measurements of cup depth. The photogrammetric procedure tolerates refocusing, repositioning, and realignment as well as small variations in the geometric position of the camera. Progressive underestimation of cup depth was observed with increasing myopia, while progressive overestimation was noted with increasing hyperopia. High cylindrical errors at axis 90 degrees led to significant errors in cup depth estimates, while high cylindrical errors at axis 180 degrees did not materially affect the accuracy of the analysis. Finally, cup depths were seriously underestimated when the pupil diameter was less than 5.0 mm.

Explore related subjects

AstigmatismComputersHumansModels, StructuralOptic DiskPhotogrammetryPhotographyPupilRefractive ErrorsJournal ArticleResearch Support, U.S. Gov't, P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A R Rosenthal, D G Falconer, I Pieper. 1980. Photogrammetry experiments with a model eye.. https://doi.org/10.1136/bjo.64.12.881

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed1996

Clinical analysis of steep central islands after excimer laser photorefractive keratectomy.

PURPOSE: To examine topographic irregularities known as steep central islands that may occur after excimer laser refractive surgery and affect visual acuity. METHODS: We reviewed the computed corneal topographic maps of 35 eyes that had undergone excimer laser photorefractive keratectomy with an excimer laser for compound myopic astigmatism or anisometropic myopia. Steep central islands were defined as areas of steepening of at least 3 diopters and 1.5 mm in diameter. A classification system was developed based on the presence of steep central islands during the postoperative period as follows: class 0, absent; class 1, present at 1 week; class 2, present at 1 month; class 3, present at 3 months. RESULTS: Steep central islands were seen in 25 eyes (71%) at 1 week, 18 eyes (51%) at 1 month, seven eyes (20%) at 3 months, and four eyes (11%) at 6 months. After surgery without nitrogen gas blowing, 16 of 25 patients had class 2 or 3 steep central islands compared with two of 10 eyes when gas blowing was used. Loss of best spectacle-corrected visual acuity of 2 Snellen lines or more was seen in eight of 18 eyes with class 2 or 3 steep central islands at 1 month and three of 18 eyes at 3 months. A similar loss occurred in one of 17 eyes with class 0 or 1 steep central islands at 1 month and none of 17 eyes at 3 months. In all eyes with only class 2 steep central islands, loss of at least 1 Snellen line of best spectacle-corrected visual acuity at 1 month was associated with visual restoration at 3 months when the island was no longer present. CONCLUSION: Loss of best spectacle-correlated visual acuity is associated with steep central island formation, and may prolong visual rehabilitation after excimer laser photorefractive keratectomy.

Astigmatism↗