Meredith Walter Morgan--a salute.
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History, 20th Century↗
Biomedical subjects
M D Sarver
Publications and source records attributed to M D Sarver.
Discoloration of hydrogel contact lenses under standard care regimens.
Four types of hydrogel contact lenses (N = 164) were subjected to in vivo and in vitro standard care regimens for a period of six months. Lens care variables included: heat disinfection in Bausch and Lomb Sensitive Eyes saline solution; heat disinfection in Cooper Unisol 4 sterile, nonpreserved saline solution; American Optical/Reichert Lensept disinfection and storage in Sensitive Eyes saline; and Lensept disinfection and storage in Unisol 4 saline. The study was conducted to determine the conditions under which lens discoloration occurs. The 45% Bufilcon A (55% water) lens showed significant discoloration in vivo with both heat and Lensept disinfection when rinsed and soaked in sorbate-preserved saline, and in vitro when heat disinfected in sorbate-preserved saline.
Color↗
A bitoric gas permeable hard contact lens with spherical power effect.
A 36 lens fitting set of gas permeable hard (Polycon II) bitoric contact lenses with spherical power effect in vivo was used to fit 50 patients. Thirty six patients (66 eyes) were correctly fitted with spherical power effect (SPE) lenses while 14 patients (27 eyes) required cylinder power effect (CPE) lenses. The mean flat base curve was 0.45 D.K. flatter than the mean flat corneal K reading, and the mean base curve toricity was 0.50 D.K. less than mean corneal toricity. Overall patient response was good to excellent for 82% of the patient sample.
Adolescent↗
Corneal response to rigid and hydrogel lenses during eye closure.
Corneal changes were monitored in 14 subjects following 3 hr of eye closure while wearing selected oxygen permeable rigid and hydrogel lenses. The mean increase in corneal thickness ranged from 82.5 to 29.5 microns for rigid lenses with oxygen transmissibilities (Dk/L) between 0.2 X 10(-9) and 57.0 X 10(-9) (cm/sec) (ml O2/ml X mmHg), respectively, and ranged from 82.5 to 23.5 microns for hydrogel lenses with Dk/L between 2.5 X 10(-9) and 70.0 X 10(-9) (cm/sec) (ml O2/ml X mmHg), respectively. No differences in the amount of swelling between rigid and hydrogel lenses of the same oxygen transmissibility were observed (t-test, P greater than 0.20). Combining the swelling data for both types of lenses shows that a minimum lens oxygen transmissibility of approximately 75 X 10(-9) (cm/sec) (ml O2/ml X mmHg) is necessary during eye closure to prevent contact lens induced edema. The estimated oxygen tension under a lens with this Dk/L value is 40 mmHg. Recovery of the cornea to baseline thickness follows a nonlinear time course, with the rate of dehydration decreasing as the cornea thins. For initial swelling of 40-54 microns, 55-69 microns, and 70 microns and above, the time to reach baseline thickness was 1.5, 2.0, and 2.5 hr, respectively. Effects on vision, corneal curvature, distortion, and epithelial integrity were not clinically significant during this short period of eye closure.
Adult↗
Intersubject difference in corneal edema response to hypoxia.
A common clinical observation is that some patients are more prone to the development of corneal edema than others. To test the validity of this observation, 30 subjects each wore an experimental hydrogel lens designed to stress corneal metabolism by reducing oxygen availability and thereby producing measurable amounts of corneal edema. The corneal edema response varied from 20.3 (3.7%) to 55.1 microns (12.2%) after 3 hr of opened-eye lens wear. Mean intrasubject reliability was +/- 3 microns (0.6%). Corneal edema response to the experimental lens was well correlated with corneal edema response to a conventional thin hydrogel lens (r = 0.83). These results support the conclusion that some patients are more prone than others to developing corneal edema and that these patients can be identified by measuring corneal thickness changes after a 3-hr wearing trial with a thick HEMA lens of standard dimensions.
Adult↗
Aphakic patient response to extended wear contact lenses.
65 aphakic patients (89 eyes) wore extended wear contact lenses for an average period of 22.8 months. 74% of the patients developed one or more readily detectable ocular changes during the course of the study. These complications, their frequency, cause and management are described and discussed. In spite of the large number of complications, 82% of the patients were still wearing lenses at the termination of the study period. None of the complications were serious enough to produce ocular tissue damage that resulted in any permanent loss of vision. Careful patient management and frequent follow-up visits were the key to achieving successful wearing results.
Aged↗
Corneal edema with hydrogel lenses and eye closure: time course.
Central corneal thickness changes during the wearing of hydrogel lenses under closed-eye conditions were measured for two subjects. Each wore an investigational ultrathin Bausch & Lomb Soflens contact lens (series X-176) on one eye only under closed-eye conditions for periods ranging from 30 min to 6 hr. The other eye served as a control. Corneal thickness of the control eyes increased gradually and reached a maximum increase of about 4% at the end of the 4-hr wearing trial. Corneal thickness in the experimental eyes also increased with wearing time during the first 4 hr and then remained fairly constant up to a wearing time of 6 hr. The maximum thickness increases for the two subjects were 9.8 and 9.1%, respectively. About 80% of the maximum corneal thickness change was present after 3 hr of closed-eye contact lens wear. The corneal thickness in the control eye returned to baseline 80 min after removal of the contact lens. Corneal thickness of one experimental eye returned to baseline 2 hr after the contact lens was removed.
Adult↗
Corneal edema with hydrogel lenses and eye closure: effect of oxygen transmissibility.
Several investigators have reported that significant corneal edema develops when daily wear hydrogel lenses are worn with the eyes closed. The amount of edema that develops when extended wear hydrogel lenses are worn with eye closure is not well documented. This study compared the amount of corneal edema that developed when subjects wore one daily wear lens with the edema that developed when they wore three lens types designed for extended wear. The daily wear lens was the U3 series Bausch & Lomb Soflens contact lens. The extended wear lenses were the Cooper Permalens, the Soft Lens Hydrocurve II 55 lens, and the Sauflon PW lens. The five subjects developed only small amounts of corneal edema when they wore the four lens types under opened-eye conditions but they developed significant amounts of corneal edema when they wore the four lens types for 3-hr periods with eye closure. The amount of corneal edema correlated well with the oxygen transmissibility (DK/L) of the study lenses. The results can be used to predict the amount of corneal edema that the average patient will develop initially when wearing a hydrogel lens of known water content or oxygen permeability (DK) and thickness (L) under opened and closed-eye conditions.
Adult↗
Induced visual and optical changes.
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Accommodation, Ocular↗
Corneal edema with hydrogel lenses and eye closure: effects of lens thickness.
Subjects wore hydrogel lenses of two different thicknesses (0.07 mm and 0.18 mm) on one eye and no lens on the other eye during 3-hour periods of eye closure. They developed more corneal edema (12.7%) with the thicker lenses than with the thinner lenses (7.9%) and more corneal edema with the thinner lenses than with no lens (0.9%). The results suggest that hydrogel lens thickness would have to be less than 20 nm to reduce corneal edema to levels that develop when the eyes are closed without a contact lens.
Adult↗
Corneal edema with several hard corneal contact lenses.
Five patients were each fitted with polymethylacrylate (PMMA), BP Flex, and Polycon corneal contact lenses of the same dimensions. Corneal edema was monitored with a slit-lamp biomicroscope and pachometer. Lenses were worn in a double-masked and random sequence for periods of 6 hr. Patients developed less corneal edema with Polycon lenses than with PMMA lenses. There was no significant difference in corneal edema with PMMA and BP Flex lenses. Those patients who developed little corneal edema with optimum-fitting PMMA lenses also developed little edema with the BP Flex and Polycon lenses. Steeper-fitting PMMA and BP Flex lenses produced more corneal edema than optimum-fitting lenses made of the same materials, while steeper-fitting Polycon lenses produced only slightly more edema than the optimum-fitting Polycon lenses.
Adult↗
Corneal effects of high plus hydrogel lenses.
Five aphakic patients and five phakic patients were fitted with high plus Bausch & Lomb Soflenses. We evaluated corneal edema, staining, vertical striae, and corneal thickness before and after a 5-hr wearing period. The high plus lenses produced average corneal-thickness changes of 9.6% and 7.1% for the phakic and aphakic groups, respectively. Biomicroscope examination showed moderate amounts of vertical striae, epithelial staining, and corneal edema for both groups. The amounts of edema, staining, and striae were higher than when regular and thin minus lenses were worn. It is likely that the thickness of the high plus lenses reduces the oxygen supply to the corneal epithelium, causing relatively marked edema.
Adult↗
Corneal edema with contact lenses under closed-eye conditions.
Subjects wore PMMA, CAB, and thin hydrogel contact lenses with their eyes closed for periods of 6 hr. The corneal edema that developed was evaluated by observing the amount of central circular clouding and by measuring the increase in central corneal thickness with a slit-lamp biomicroscope and pachometer. Central circular clouding was greater with the PMMA and CAB lenses than with the thin hydrogel lenses. Corneal thickness increased by different amounts for the three subjects, but the three lens types caused about the same increase in corneal thickness for a given subject.
Adult↗
Stability of CAB contact lenses with hydration.
The effects of hydration on the base curve of CAB lenses were measured with a radiuscope. A significant amount of lens warpage and variability in curvature was detected in all lenses under conditions of continuous hydration. Thinner lenses flattened more than thicker lenses of the same power. Lenses of greater minus power flattened more than lenses of less minus power for a given lens thickenss. Plus power lenses were more stable than minus power lenses. Control lenses, stored dry, did not flatten or warp.
Absorption↗
Results with the Bausch and Lomb F3 series Soflens contact lens.
We wanted to determine whether the Bausch and Lomb F3 series Soflens contact lens increases the number of patients who can successfully wear Soflenses. Thirty-two patients (64 eyes) who could not successfully wear 12.5-mm-diameter B, F, J, or N series Soflenses were fitted with the 13.6-mm-diameter F3 series lenses. For 40 of the 64 eyes, the F3 series lenses were successfully worn. Use of this lens series clearly increased the number of patients who could be fitted with Bausch and Lomb Soflens contact lenses. For many patients, this flatter, larger lens centered better and improved vision and comfort compared with the best-fitting Soflens of the 12.5-mm-diameter series.
Adult↗
Patient responses to gas-permeable hard (Polycon) contact lenses.
Forty-six patients who were unable to wear polymethylmethacrylate (PMMA) contact lenses, owing mainly to corneal edema and associated symptoms, were fitted with gas-permeable hard Polycon lenses of the same dimensions. Thirty-one patients (67%) wore the POLYCON lenses successfully. Thirteen (28%) did not, because of discomfort. For 2 patients, the results were unknown. None of the 46 patients exhibited observable edema with the POLYCON lenses. For a group of 5 patients (10 eyes), mean corneal thickness change after 8 hr of lens wear was insignificant. Oxygen transmissibility of these lenses is approximately 5.0 X 10(-11) (cm2 X ml O2)/(sec X ml X mm Hg), a value less than that for hydrogel lenses which produce more edema. It is predicted that gas-permeable hard lenses will eventually replace PMMA lenses.
Adolescent↗
Soft and hard contact lenses worn in combination.
Each of 5 subjects with normal corneas was fitted with a Bausch & Lomb F3-series Soflens contact lens and with an experimental F3-series ultrathin Soflens. A best-fit PMMA lens was worn in combination with each of the soft lenses. In addition, a best-fit CAB lens and a tight PMMA lens were separately worn in combination with the ultrathin soft lens. Each of 3 subjects with keratoconus was fitted with an ultrathin soft lens combined with a PMMA lens. For the normal corneas, the combination that produced the least corneal edema after 5 hr was an ultrathin soft lens with either a PPM or CAB lens of best fit. Two of the 3 keratoconic subjects were able to wear their contact lens combination for the 5-hr test period; corneal swelling was 1.7% and 5.3% For all subjects, acuity with a combination co ntact lens system was better than with a soft or hard lens alone.
Adult↗
Patient responses to 13.6-mm diameter Bausch & Lomb thin Soflens contact lenses.
Responses were obtained from 12 subjects (24 eyes) who wore 2 types of 13.6-mm diameter Bausch & Lomb Soflens contact lenses-thin F 3 lenses and conventional-thickness F3 lenses. These responses were also compared with those of patients who had worn thin F lenses that were 12.5 mm in diameter. Fewer patients experienced discomfort or corneal changes with the thin F3 lenses than with the conventional ones. Lens diameter was also an important factor in improving the patients' responses. Only 35% of a different sample of 23 patients who had been fitted with 12.5-mm diameter thin F lenses had been able to wear them successfully, compared with 75% of those wearing the 13.6-mm diameter thin F3 lenses, even though the mean corneal thickening caused by the smaller lenses did not differ significantly from that caused by the smaller lenses did not differ significantly from that caused by the thin F3 lenses. Thin hydrogel lenses with diameters larger than 13.6 mm thus might produce an even better overall patient response while still causing minimal corneal edema.
Adult↗